IFATCA - The Controller - May 1975

D 21003 F

JOURNAL OF AIR

In this Issue:

OF THE INTERNATIONAL TRAFFIC

CONTROLLERS

FEDERATION ASSOCIATIONS

Quantification of Air Traffic Controller's Acceptable Workload ATC Implications of the Boeing 747 SP

FRANKFURT

AM

MAIN

MAY

1975

VOLUME

14

N 0.

2

IFATCA'76 · 26-30APRIL · IFATCA'76

THE CITY OF IFATCA'S XVth ANNIVERSARY CELEBRATION

IFATCA

JOURNAL

OF

AIR

TRAFFIC

CONTROL

THECONTROLLER Frankfurt am Main, May 1975

Volume 14 · No. 2

Publisher: International Federation of Air Traffic Controllers' Associations, P. O. B. 196, CH-1215 Geneva 15 Airport, Switzerland.

Officers of IFATCA: J-0. Monin, President, 0. H. J6nsson, Vice-President (Technical), R. E. Meyer, VicePresident (Professional), E. Bradshaw, Vice-President (Administration), T. H. Harrison, Executive Secretary, J. Gubelmann, Treasurer.

Editor: G. J. de Boer, P. 0. B. 8071 Edleen, Kempton Park, Tvl., 1625 South Africa Telephone: 975-3521 Contributing Editor: V. D. Hopkin (Human Factors) Managing Editor: Horst Guddat, 0-6368 Bad Vilbel 2, Otto-Bussmann-Stra8e 7 (Federal Republic of Germany).

Telephone: (06193)85299 Publishing Company, Production, Subscription Service and Advertising Sales Office: Verlag W. Kramer & Co., 6 Frankfurt am Main 60, Bornheimer Landwehr 57a, Phone 43 4325 and 49 21 69, Frankfurter Bank, No. 3-03333-9.Rate Card Nr. 4.

Printed by: W. Kramer & Co., 6 Frankfurt am Main 60, Bornheimer Landwehr 57a. (Federal Republic of Germany).

Subscription Rate: OM 6.- per annum for members of IFATCA OM 10.- per annum for non-members (Postage will be charged extra) Contributors are expressing their personal points of view and opinions, which must not necessarily coincide with those of the International Federation of Air Traffic Controllers' Associations (IFATCA).

IFATCA does not assume responsibility for statements made and opinions expressed, it does only accept responsibility for publishing these contributions.

Contributions are welcome as are comments and criticism. No payment can be made for manuscripts submitted for publication in "The Controller". The Editor reserves the right to make any editorial changes in manuscripts, which he believes will improve the material without altering the intended meaning.

Written permission by the Editor is necessary for re• printing any part of this Journal.

CONTENTS

Air Traffic Controller's Acceptable Workload ...............

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7

ATC Implications of the Boeing 747 SP

.

11 15

...................

Future Air Traffic Control Systems .......................

.

Airport Surface Detection Radars .........................

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20

New Generation Equipment for Dutch Airspace .............

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21

, ... , , .

25

International Law ...........................

, .....

Accident Investigation Report Aeronautical Satellites ............................

30 , ......

New Elements: New Responsibilities .....................

.

31

.

34

The Pilot's Point of View . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

36

Fotos: Archiv, Boeing, Hollandse Signaalapparaten, Philips Telecommunication Systems. Thomson·CSF

"AIRCAT": T-VT's New System Concept for ATC ..........

,.

39

Cover: Horst Guddat

News from the Federation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

43

News from Member Associations . . . . . . . . . . . . . . . . . . . . . . . . . .

44

News from Corporation Members . . . . . . . . . . . . . . . . . . . . . . . . . .

46

Spotlight on a Corporation Member - ASSMANN GMBH . . . .

48

Book Review . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

51

Advertisers In this Issue: APCA·IFATCA 76 (inside cover), AEG-Telefunken (page 2), Cossor Electronics (page 5). Marconi Radar Systems (page 6), Ferranti Digital Systems (page 26/27), ASSMANN GMBH (page 49), Selenia Radar (inside back cover).

Thomson-CSF (back cover).

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International Air Traffic :

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£

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Editorial

by Horst Guddat, retiring Vice President of IFATCA

A Decade with the Federation For the writer, ii all started in Vienna 10 years ago when he was a member of the German delegation to the 4th IFATCA Conference, and the time to call a halt came at the 14th Conference held in Melbourne last month when he retired from the Executive Board. Looking back on a decade of work for the Federation including 7 years as a Board member, it is not easy to remember all impressions as there are so many of them. But let me try to give you some which I shall never forget and which I hope will inspire and motivate others who will join the team in the years to come.

Personalities, to make a start, such as the men of the first hour - Maurice Cerf (France), Roger Sadet (Belgium), Hans Thau (Germany), Henning Thrane (Denmark), Walter Endlich (Germany) and "Tek" Tekstra (Netherlands) - how can we ever forget them? They navigated the IFATCA ship through narrow waters until it reached the open sea where it began to show its full usefulness and capabilities.

"Tek", as President, was at the steering wheel for more than 6 years, longer than one can normally expect a man to give his spare time for investment into IFATCA; his immense energy and great personality was an example to all. Then, some of the men who followed: Arnold Field fortunately, for the Federation, still with us as Chairman of Standing Committee I - with his superb monologues over long periods of committee sessions, with his flair for humour and diplomacy, his wide knowledge and spirited speeches during his spell of duty as President. There was Geoffrey Monk, devoted, untiring, IFATCA's first Executive Secretary, of whom it can be truly said that thanks to his efforts, IFATCA's name was put squarely on the diary of the international aviation community. Other names spring to mind: Bernhard Ruthy (Switzerland, also still with us as Chairman of SC. Ill); "Tommy" Thomas (Rhodesia); Gunnar Atterholm (Sweden); Dick Campbell (Canada); Ernest Mahieu (Germany); Herbert Brandstetter (Austria); and others. Finally, today, we have Jean-Daniel Monin (Switzerland); Tom Harrison (U.K.); Jean Gubelmann (Switzerland); Bob Meyer (PATCO, U.S.A.); Ole J6nsson (Iceland); Ge de Boer (South Africa), and the newcomer Ted Bradshaw (U.K.).

At the end of my decade of work for the Federation I can say - not without pride - that this Board of dedicated and motivated people is among the best the Federation has had. But not only Board members have contributed to IFATCA's high standing, as names like John Saker, Alfred Nagy and Ted McCluskey, to name only three, testify.

Milestones in the history of the Federation were the 1st Annual Conference (Paris, 1962), followed by London (1963) where Standing Committees I, II and Ill were formed; the Brussels Conference (1964) which saw the for-

mation of SC. IV; the 1965 Conference in Vienna (a personal langmark as my first Conference); the 1966 Conference in Rome (where I felt already quite familiar with the proceedings) which saw the establishment of the office of Regional Liaison Officer. It was around 1966 that the expert work of IFATCA's Technical Committee started to attract the attention of ICAO and IFALPA, and for the first time, a paper to which - IFATCA contributed with IFALPA on Area Navigation Aids was submitted to the 5th EUMRAN Meeting of ICAO, and thereafter IFATCA made its own contribution in the form of its now well known thesis on Primary Radar Procedures. The Geneva Conference in 1967 was a significant event for better ATC and recognition of the profession, well attended by Member Associations and attracting many aviation personalities from ICAO, IATA, IFALPA, IANC, IAOPA, and for the first time, the ILO. But Munich (1968) was the beginning of a new era. Not only was this Conference the first one on a really big scale, participation in the working sessions was also on a much higher plateau, while two further SCs saw the light of day (V and VI). It was at Munich where I joined the Board.

As IFATCA's Honorary Secretary at the time, I came face to face with the issue which I have not been able to solve during my years as an IFATCA Officer, an issue which has caused and is continue to cause much bitterness among controllers: free or reduced air transportation for controllers, which calls for a change in IATA Resolution 200, and a change in the attitudes of IATA and the Government authorities behind them. In my view, in their incomprehensible attitude, IATA separates the controller/ pilot team, a team that makes the system work. Airline managements and Governments have not yet realised that by separating the two, they cut the roots from a living tree.

I sincerely hope that one day reason will prevail, and that controllers' representatives will be able to attend those technical meetings from which they are now - due to lack of transport - absent to the detriment of safety in the air.

The Belgrade Conference (1969), the first in a socialist country, took place against a background of growing unrest and dissatisfaction among controllers regarding their lack of recognition and status, eventually resulting in a number of industrial disputes in the U.S.A., France, the Netherlands, Germany, and so on. PATCO came on the scene in the U.S.A., and the question of affiliation of the two U.S. Associations became an issue at IFATCA. We saw the first IFATCA action on hi-jacking, to obtain the release of an EL AL airliner held in Algiers. An IFATCA delegation took part in the 6th ANC (ICAO) Meeting in Montreal.

The 9th IFATCA Conference in Montreal (1970) was the first venue outside Europe, and was an outstanding success despite new problems which had to be overcome. Travelling facilities for delegates were obtained by the efforts 3

of Arnold Birnbaum of the German Association who was involved in the generous gesture of the German Air Force to put a Boeing 707 at the disposal of European and other delegates to enable them to fly to Montreal. At this meeting, SC. IV was re-organised to make it more effective.

As the !LO had already pointed out in 1963, the efficiency of an ATC system is directly related to the conditions of employment of ATC personnel. Standing Committee IV studies were becoming very relevant. Athens (1971) saw the establishment of a third Conference Committee (Professional), as the original two (Technical and Administration) could no longer cope with the rapidly increasing amount of work. Dublin (1972) demonstrated more than any other event the tremendous spirit of IFATCA, when delegates found the new Burlington Hotel, where the Conference was to be held, not quite ready, but instead of complaining, rolled up their sleeves to adjust their rooms and the meeting facilities available. The result: another memorable occasion. The IFATCA family really is a great family; the hotel staff could not get over it.

The period between the Dublin and Reykjavik (1973) Conferences was a difficult time for the Federation. Due to financial considerations, activities had to be cut down drastically. IFATCA's journal THE CONTROLLER, since 1961 a regular, well-known and highly professional magazine, was suspended as a cost-saving measure, and its absence was immediately felt to the detriment of the Federation's promotion efforts and image. The problems facing Jean-Daniel Monin, the new President at the time, and his team, were many. But they were all overcome one by one, and Reykjavik was truly a turning point for the better. In the technical field, subjects like Flow Control and Requirements of SSTs regarding ATS, were embarked upon; in the professional area, SCs IV and V dealt with numerous job related topics, including medical aspects.

On the administrative sector, the Canadian Association through SC VI came up with a new structure of the IFATCA management. The finances were put in order. After 12 years of untiring efforts, Walter Endlich handed over the reins of THE CONTROLLER to Ge de Boer who had the unenviable task to revive IFATCA's journal in a matter of weeks.

Ge is to be highly commended for his work in producing a high standard publication. The design of a new cover for our journal in order to give it a new look to correspond with the change in style and greater variety of.contents, was very well received. It was great to see the revival of THE CONTROLLER, but it was even greater to see it progress to the world's leading ATC publication again. Tom Harrison stepped into the Secretariat and did a marvellous job re-organising and mechanising the IFATCA administration. So it went on. IFATCA has not looked back since Reykjavik, where for the first time 25 0/o more working time was allotted to Conference work.

Alas, on a sombre note, the Reykjavik Conference also saw the last appearance of our true friend Bob Shipley, IFATCA's first Corporation Members' Co-ordinator, who died very unexpectedly last year. Bob will never be forgotten. Vienna, Geneva, Munich and Montreal were the scene of some of the most impressive technical exhibitions put on by our Corporation Members, who - in doing so - gave outstanding service to the Federation and the Air Traffic Control Service.

After Reykjavik, the image of the Federation has changed considerably. Often given the tag "social club" because of the social functions which form part and parcel of every international Conference, this assertion has vanished completely. The manner in which the Directors, 4

Regional Councillors, Executive Board, Standing Committees and Delegates discharge their duties have found attention and increased appreciation among the membership.

The 13th Annual Conference in Tel Aviv saw the formation of SC VII (Legal). Melbourne last month saw a new record of working papers and a new record of resolutions passed by the Directors. With three more new entrants at Melbourne IFATCA has now 41 Member Associations.

At Melbourne I dropped out of the team. But not quite. I shall still continue to serve IFATCA by staying on in Ge de Boer's team in the function of Managing Editor. The combined function of Vice President/Managing Editor which I have discharged since the Reykjavik Conference, was a great burden to carry, especially for my family. It meant a long working week, not counting the time spent at meetings and on travelling. Only insiders know the amount of work involved from the time the manuscripts are delivered to the Printing House until the magazine is in the mailbox of its readers. It was the realisation that my family should receive more of my time that caused me not to seek re-election as Vice President, and devote my efforts to the production of our journal only. We are the envy of many other organisations in having such a fine magazine, and we must keep it going.

To any one aspiring to serve on IFATCA's Executive Board, I have this message. You will join a great team, but it means many long hours of dedicated work, more often than not unthankful, but utterly rewarding personally.

The many rounds I have been running for IFATCA were a wonderful experience. I have met many nice people, made numerous lasting friendships which I hope to follow up during the coming years. To realize Federation policy is not always an easy task, leading to delicate and unpleasant situations at times. The workload often reaches the maximum of what can be expected of voluntary efforts. Considering that the 1964/65 IFATCA expenditure was only about 1400.- Pound Sterling, while the 1974/75 expenditure runs to over 140.000.- Swiss Francs, you can see the impressive rate of increase in the Federation's commitments. But don't let me put you off. I cannot bring myself to bail out entirely either, because after two years of close and harmonious co-operation with the Editor, a solid relationship now exists. A common interest to- produce the best ATC Journal possible has formed the team. To enhance the image of IFATCA and to bring our message through to all aviation people will keep the team alive.

I apologise for the length of this editorial, but 10 years with IFATCA just cannot be molded into a few paragraphs only.

Report on IFATCA 75 in the Next Issue In the August issue of THE CONTROLLER a report will be published on the Federation's 14th Annual Conference, which was held in Melbourne 14-18 April 1975.

'Ii

. u t

t

y.: '

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I

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6

Quantification Of Air Traffic Controller's Acceptable Workload

by Jason C. Yu, Ph. D., P. E. Professor of Civil Engineering; Director, Transportation Research Center, University of Utah, Salt Lake City, U.S.A.

Abstract In the air traffic control systems, the controller serves as the nuclei of the system with an aim of safety and efficiency. Thus, it is essential to study a human performance reliability so that a realistic evaluation of the improvement measure of the air traffic operation can be accomplished. The basic objective of this study is to identify a set of important factors for evaluating the air traffic controller's performance and to develop a method of quantifying their acceptable workload under various working conditions, including variables such as weather, emergency, work-hour and conflict. The controller's activities are analyzed and grouped into several subtasks which require such human capabilities as visual and suditory monitorings, reading, and recording. The examination of human factors research in the area of air traffic control and application in an actual field study have proved that the developed quantitative method seems to be supported by both theoretical analysis and empirical data for the real world.

Introduction Undoubtedly, painstaking consideration of human factors in a man-machine system design is of importance to the operational efficiency. Part of requisite considerations lie in allocation of functions between man and machine, and especially in planning for the workload on individual operations. Implementation of human factors in system design is difficult without a mathematical discription of the time-varying nature of man.

In the air traffic control (ATC) system, the controller serves as the nuclei of the system with an aim of safety, orderliness, and expedition. For this reason, the development of a human performance reliability system on the controller's workload capacity is paramount to the operation of the ATC system.

Recommendations from previous studies on the ATC controller's acceptable workloads under different physical, physiological, and environmental conditions did not provide the results in quantitative form. Most of human performance factors can be theoretically defined; however, quantifying these factors, so as to evaluate the controller's acceptable workload, has proven quite difficult. The objective of this study was an attempt to establish a group of principal interia for evaluating the ATC controller's performance and to develop a method of measuring the controller's acceptable workload under various working conditions.

The State-of-the-Art in Air Traffic Controller's Workload Research work on the ATC from the human factors point of view was started in the late 40's, but no particular attention was paid to the problem of the controller's workload at that time. In 1963, Arad and Bar-Atid constructed their mathematical model of prediction of controller's workload. They established a model which considered the total workload as the sum of the background load, the routine load, and the airspace load. This model was later studied by Jolitz (1965) to check its validity. He compared the Arad and Bar-Atid's model with two other models; one model used the routine load as the total workload, and the other model assumed the total workload as being equivalent to the average number of aircraft under simultaneous control. The results indicated that the Arad and BarAtid's approach is superior to others in predicting the controller's workload.

Physiological studies on the controller's strain by testing his heart rate, blood pressure, urine analysis, etc., have not been successfully applied. However, physiologists believe these types of measures will eventually provide applicable results.

Several measures using simulators to obtain the controller's mental load were proposed by previous researchers. These included the measure of space mental capacity in which the contr,olter was asked to perform a secondary task while also absorbing a mental task; the method of distraction, in which the controller was asked to perform the task in a stress condition, i. e., a binary choice secondary task (Brown 1961, Rolfe 1969). There were also methods for measuring the controller's error rate and the controller's moment of conscious brain control (Kalsbeek 1971). All of these measures require a laborious simulation process and data analysis, from which the results are mostly ambiguous.

Leplat and Bisseret (1965) and Older (1972) used the method of external observation of the controller's activities to analyze his workload. Lepat und Bisseret broke the ATC work into subtasks, and constructed a flow diagram to show the work sequence; Older then calculated the percentage of time the controller spent on each subtask required in the ATC. Their method eliminated the system errors caused by the simulator and is inexpensive. The results are easily understood and applied. However, the analysis of the controller's mental process is quite subjective.

Jolitz (1965) used questionnaires and interviews to obtain empirical data on the controller's judgment. Because the results are practical and realistic in nature, the Federal Aviation Administration has adopted his method 7

to measure the controller's workload. In this method, errors inherited from the variation of the controller's strategies and judgment can be reduced by enlarging the sample size and by using unambiguous questioning.

From the above summary of past research on the ATC controller's workload, it appears that the method of external observation suggested by Leplet, Bisseret and Older and empirical methods employed by Jolitz have advantages over other approaches in terms of practicability and reality.

With these theories and methods in mind, it is meaningful for this study to blend the advantageous features of them in order to develop a practical and quantitative means of relating the ATC controller's performance capability to various working situations. The ultimate objective of such an investigation is to aid the overall effort to improve the efficiency of the ATC system.

Analysis of Air Traffic Controller Activity There are three types of ATC stations: the enroute, terminal and flight service station. Each type of station serves a different purpose in the ATC system and requires specially trained controllers. The detailed activities of the controllers in each type of station is presented in the following sections.

En Route Operations Currently, 21 en route centers are in operation in the continental United States. These centers have responsibilities for en route traffic, transition traffic (changing altitude), and back up traffic from the congested terminal. En route controllers are usually required to be able to work in all operational positions in the en route center which includes the Flight Data lnterphone position, the Nonradar Control Position, and the Radar Control Position. An analysis of the activities of the en route center indicates that the operational responsibilities of controllers are as follows: A. Flight Data lnterphone In this position, the controller's activities include (1) copying, interpreting and distributing flight plan information, (2) preparing the required fixed postings, (3) operating the interphone system, (4) encoding, decoding, interpreting and disseminating teletype flight plan messages, (5) interpreting and posting weather information and notices to airmen, (6) coordinating traffic by transmitting flight plans, estimates, control data and revisions to the adjacent sector/facility, and (7) issuing clearances and advisories to aircraft.

B. Nonradar Control The controlled activities include (1) operating radio equipment, (2) reviewing the accuracy of flight progress strips and weather information, (3) receiving and posting flight progress reports, (4) analyzing the traffic picture for potential conflicts, (5) initiating, issuing, revising and forwarding clearances, advisories and other control information to departing, en route and arriving aircraft, (6) preparing required reports and maintaining sector logs.

C. Radar Control The controller in this capacity is required to (1) align and adjust radar equipment, (2) read and interpret the radar scope display, (3) provide traffic advisories to aircraft operating under visual flight rules, (4) operate the

8

coordinate position, and (5) prepare required reports and maintain sector logs.

Terminal Operations The basic function of a terminal controller is to control air traffic near the airport (usually within a 40-mile radius) by direct vision or radar. His responsibilities are to insure the orderly separation, sequencing, and spacing of aircraft; and to give navigational assistance, approach guidance and weather information. Each operational position in the terminal operation has different stress, and the controllers are usually scheduled to work in all operational position alternatives in order to achieve fairness and better performance. The activities of each operational position are analyzed in this study and are given below: A. Flight Data In this position, the controller's activities include (1) operating the interphone system, flight data entry, and printout equipment, (2) copying, interpreting, and relaying flight data, (3) preparing and distributing flight progress strips, (4) receiving and - relaying weather information, (5) setting up frequencies on standby radio equipment, (6) alerting emergency equipment, (7) making visibility reports, and (8) collecting, tabulating and storing daily records.

B. Ground Control The controller's activities in this position include (1) monitoring and analyzing ground traffic, (2) operating the radio equipment and guarding assigned radio frequencies, (3) issuing taxi clearances, (4) collecting, analyzing and distributing pilot reports as well as reports concerning hazards, or the operational status of facilities, (5) relaying, initiating or coordinating advisories, information, and IFR clearances, and (6) initiating and directing emergency action.

C. Local Control The local control position requires the controller to (1) determine and issue instructions relative to the flight path, landing and takeoff sequence, clearance and traffic information of each aircraft, (2) assign runways, (3) issue control instructions and advisories to departing aircraft, (4) instruct pilots to change radio frequencies or radar beacon codes, (5) operate the airport visual aid system, (6) observe and report weather changes, and (7) monitor navigational aids.

D. Nonradar Approach Control The controller's activities in the approach control (non radar) position include (1) sequencing fixed posting, (2) reviewing the accuracy of flight data, (3) updating weather information, (4) receiving and posting flight progress reports, (5) revising estimates, (6) analyzing traffic for potential conflicts, (7) monitoring the approaches of aircraft on instrument clearance, (8) initiating, issuing, and revising clearances, advisories, and other control information (9) analyzing and expediting total traffic movement by coordination with other positions within the facility as well as outside facilities, (10) providing flight assistance service, (11) receiving, interpreting, and disseminating pilot weather reports and (12) operating direction finding equipment.

E. Radar Approach Control The controller in this position in required to (1) provide radar arrival control, departure control, and emergency

service, (2) align and operate radar equipment, (3) read and interpret the radar scope display, (4) provide traffic advisories to aircraft operating under visual flight rules, and (5) provide stage I, 11,or Ill service.

Flight Service Station Operations The flight service station gives weather information, warnings, and advisories to pilots at local airports through an extensive telephone and r..adio system. The controller working in a flight service station encounters much less stress and strain than the others. Therefore, the concern about the controller's workload problem need not be given to this area.

Workload Measurement Criteria From the analysis of the controller's activities, it is obvious that the dimensions of measurement criteria required for each operational position are different and immense. Any attempt to set up a utility function for each subtask in each operational position will be laborious and expensive in time. In order to overcome this problem, subtasks requiring similar human capabilities may be grouped into ten categories. The details of this categorization are given below: 1. Visual Monitoring - Display This includes all activities which require the controller to attend to a continuously changing visual information source, e. g., observation of cathode ray tube displays, meters and counters.

2. Visual Monitoring - Nondisplay This includes all activities which require the controller to attend to a continuously changing visual information source, e. g., observing aircraft patterns, signal lights, and runways.

3. Auditory Monitoring This includes all activities which require the controller to attend to a continuously changing auditory information source, e. g., listening for radio, telephone, and intercom messages or warning signs.

4. Reading This includes all activities which require extraction of relevant information from written or printed materials, e.g., reading flight progress strips, weather messages, tables, maps, and charts.

5. Recording This includes all activities which require preparation of written messages, information and reports, e. g., preparing flight progress strips, weather messages and encoding flight data.

6. Reporting This includes all activities which require the transmission of oral messages, information and reports, e. g., transmitting flight path instructions, altitude instructions and weather reports.

7. Control Operations This includes all activities which require the application of manual force to equipment or controls, e. g., manipulating turning controls, cursors, shrimp boats and teletyping.

8. Information Organization This includes all activities which require the evaluation, synthesis, and integration of information from varied visual

or auditory sources; e. g., simultaneous consideration of type of aircraft relative speed, maneuverability, cockpit visibility, and integrating weather information from a variety of sources.

9. Selecting Among Alternatives This includes all activities which require the application of optimization techniques, e g., path selection, conflict detection, and delay prevention.

10. Information Storage This includes all activities which require short-term retention of recently acquired materials, e. g., memorizing radio frequencies, aircraft identification information, wind conditions, and flight path.

The Acceptable Workload Model Accepting the above categorization of human capabilities as workload measurement criteria, a mathematical model of the maximum acceptable workload can be derived.

As suggested by Older, the percentages of the controller's performing capacity under normal conditions required for all ten capability categories are designated as follows: N, for Visual Monitoring - Display N, for Visual Monitoring - Nondisplay N, for Auditory Monitoring N, for Reading N, for Recording N6 for Reporting N, for Control Operation N8 for Information Organization N9 for Selecting Among Alternatives N10 for Information Storage Let Kij be the ratio of the required controller capacity under condition j versus the normal condition for capability i. Let P be the total number of aircraft that the controller is able to handle simultaneously under normal conditions, and Pj be the number of aircraft that the controller is able to handle simultaneously under condition j. Assuming the total safe working capacity is approximately identical for different controllers under various working conditions, the acceptable number of aircraft that the controller can handle is inversely proportional to the sum of all required capacity to handle an aircraft. Then, C 10

i=

Where C is a constant. When the controller operates the ATC system under the normal condition, we have 10 2

KijNj = 1. Therefore, C = P, or

Pj

p

=

10

(

2

i =

KijNj

+ 05)

I

In the above equation, the truncation with the additional value 0.5 is to insure an integer solution.

Applications and Examples In applying the mathematical model constructed above to predict an acceptable workload, the first step is to 9

acquire the value of Ni by external observations. This can usually be done by timing the controller's activities of each of his capabilities. Next, interviews with the controller's and analysis of the answers provide the values for Kij and P, Pj can then be obtained by simple substitution.

Observations and interviews with controllers have been conducted at Woodrum Airport in Roanoke, Virginia. At the Approach Controller (Radar) position, the controller's time spent on each Ni was recorded, and interviews with the controller followed.

Interview questions were concerned with the effect of four conditions on ten activities of the controller. The ten activities are as follows: 1. Read the radar screen 2. Observe aircraft patterns on the ground and signal lights 3. Listen to radio, telephone, and intercom 4. Read flight progress strips, weather messages, tables, maps, and charts 5. Prepare flight progress strips, weather messages, and encoding flight data 6. Transmit flight path instruction, altitude instructions, and weather reports 7. Manipulate turning controls, sensors, shrimp boats, and teletyping 8. Determine the type of aircraft, relative speed, maneuverability; cockpit visibility, from various sources 9. Detect conflict and prevent delay 10. Memorize radio frequencies, aircraft identification, wind condition and flight path.

The four conditions used were the following: 1. Strong wind conditions How much more (or less) work do you need to perform the above ten activities?

2. Emergency conditions How does an emergency affect the amount of effort needed to perform these activities?

3. After two hours of maximum load condition How much more effort is needed to perform these activities?

4. Conflict condition How does this condition affect the amount of work needed to perform these activities?

A total of six ATC controllers were interviewed during a period of three peak hours. Typical answers were "no difference", "double", "about one and a half", "about three or four times". The mean of the controllers' answers on each capability were used as Kij. For example, in the strong wind condition, two controllers felt no extra time was needed on the radar screen; one felt double time was needed, and the other three said they needed about one and a half more. The sum of the total requirement ist 8.5 and the average is 1.4. Thus, the entry K11has the value 1.4.

The values of Kii, Ni, and P are shown below: 11 2 3 4

Kii

Ni 10

2

1.4 4.3 2 1.2 1.1

3

4

2.3 2

5

1.3 2

2.2

.34 .05 .04

.01 .005

6

7

8

2.1 1.8 1 1

1.5 1.5 1.2 1.3

2 2 4.8 1 1.1 2 1.4 1 1.5 1.5 1.2

9

10

.12 .225 1.2 0.6 0.3

P = 6 (Number of controllers interviewed) The predictions are

P, = 4

P, = 2 It is evident that human factors have significant bearing on the basic functions of the ATC system. Therefore, it is vital that a substantial program of human factors support must be planned and implemented as soon as possible.

This means the predicted acceptable workload for a controller under condition 1 is four aircraft. Under condition 2, it is two aircraft, and under conditions 3 and 4 it is five aircraft.

Conclusions Air traffic control represents a very complex system of very many elements which interact with each other in complex ways. No simple description of the behavior of this system is available from which deductions could be drawn covering the effect of changes in the systems parameters on the system performance. Such highly complex, multiply interconnected systems operating with constraints tend to behave in a counterintuitive manner. It is evident that the human element has significant bearing on the efficiency of the ATC operations. Therefore, it is vital that a substantial program of human factors support must be planned and implemented as soon as possible.

The average requirement on human capabilities during each operational position are obtainable from some previous studies. However, these requirements are difficult to define quantitatively for their relative effect on the performance of the ATC system. This study has suggested a method of quantifying ATC controller's acceptable workload under different working conditions. The developed procedure combines the methods of external observation and the rules of thumb of measuring the controller's performance capability. The results of the application of the developed quantitative method have generally been agreed upon by the controllers surveyed at Roanoke Airport, Virginia. It is recommended that further research efforts should be undertaken to develop other potential methods of alleviating the ATC controller's workload. Obviously, human factors research and development to support the overall effort to solve ATC problems are extremely essential to air transportation.

Acknowledgments This research was performed by the Department of Civil Engineering of Virginia Polytechnic Institute and State University, Blacksburg, Virginia as part of a project supported by the National Science Foundation Grant No. GK-303225. The valuable assistance of P. P. Fung in collecting and analyzing the necessary data is appreciated.

References 1. Arad, Bar-Atid, et. al., Control Capacity and Optimal Sector Design, FAA SRDS Interim Project Report No. 102-11R, 1963.

2. Brown. I. D., "Measuring the Spare Mental Capacity of Car Drivers by a Subsidiary Task", Ergonomics Vol. 4, 1961.

3. Davis, M. "Application of Fast-Time Simulation Techniques to the Study of ATC Systems", Ergonomics, Vol. 14, 1971.

4. Jolitz, G. D., Evaluation of a Mathematical Model for Use In Computing Control Load at ATC Facilities, FAA SRDS Report No. RD-65-69, 1965.

5. Jones, D. B., "The Need for Quantification in Human Factor Engineering", Annals of Rellablllty and Malntalnablllty, 1967. (cont. page 36)

ATC Implications of the Boeing 747 SP

by Tirey K. Vickers, James C. Buckley, Inc.

The Boeing 747 SP.

Many large transport aircraft were designed to be stretched in later models - for example, the Constellation, the Boeing 727, the DC-8 and the DC-10. However, several years ago Boeing was able to enter a new segment of the market by shrinking the 707 design to create the 737.

The dozen or two Boeing 747's sitting in storage this year are mute evidence that the first wide-body jet was a little too much, too soon, for some airlines to operate profitably, so Boeing has shrunk the 747 design to create a more compact, lighter, long-range wide-body transport the 747 SP (the initials stand for Super Performance). The SP will compete directly with the DC-10 and 1011 trijets and possibly with the A-300 Airbus.

Performance With a fuselage 47 feet shorter than the standard 747, but with the same engines, the SP will be about 110,000 pounds lighter than its predecessor. The reduced wing loading and power loading of the SP will provide some spectacular increases in performance. Most of these increases will directly benefit the ATC system.

On flights up to 3000 miles in length with a full passenger payload, the SP will lift off in only 25 seconds, versus 40 or more seconds for a 707 or a DC-8. The sealevel takeoff runway length required for flights up to 4000 miles will be only 6000 feet (1800 meters). At its maximum gross takeoff weight of 660,000 pounds, the SP will have an initial climb rate of 2400 feet per minute! The shorter

ground run plus the high climb rate will produce less noise for nearby communities under the climbout path; the noise will be restricted to a small area outside the airport boundaries, and will be slightly less intense at any given point under the climbout path because of the higher altitude of the aircraft. The steeJ)er climb angle of the SP should enable it to cross transition fixes at higher altitudes than other types of civil aircraft.

It is expected that SP operators will prefer to continue a high rate of climb all the way to cruising altitude in order to fly as much of the trip as possible at cruising speed.

It is planned to get the SP certificated for cruising altitudes up to 45,000 feet. Few other civil aircraft ever exceed 41,000 and use of the higher levels by the SP will tend to reduce enroute traffic density at any given flight level by spreading the total traffic load over a greater range of altitude levels. There are two other significant operational advantages in using the higher levels.

First, many thousands of hours of high-altitude research and surveillance flights by U-2 aircraft have shown that in most parts of the world (Japan may be an exception) there is a marked reduction in the amount and intensity of turbulence at altitudes above 39,000 feet. The use of these altitudes should reduce appreciably the need for SP pilots to slow down or to request an altitude change due to turbulence. The higher altitude capability of the SP will have another advantage in that it should allow this aircraft to get above most other aircraft and cruise at its higher speed capability (Mach 0.85) instead of being slowed down in 11

Legend

t ~

V

-

a c g m n -

r

Fig. 1: Present procedure, where ceiling and visibility dient on missed approach path.

minima are raised to allow for 40: 1 gra-

o p q

r s v -

x y

34 : 1 approach surface minimum ceiling 3° glide slope missed approach point intersection of 34 : 1 approach surface and 40 : 1 missed approach surface critical obstruction assumed 40 : 1 climb path demonstrated climb path at maximum landing weight, one engine out, and de-icing on. runway 40 : 1 missed approach surface from critical obstruction minimum visibility climb distance demonstrated clearance in feet (must be at least 35 feet per nautical mile, throughout distance x).

Fig. 2: Proposed procedure to safely permit lower decision height for aircraft with high demonstrated climb performance.

trail behind other jet liners which normally do not exceed Mach 0.80. On an 8-hour intercontinental flight, the higher speed of the SP should shorten the trip by about 22 minutes.

The approach speed of the 747 SP will be somewhat lower than that of other wide-body jets, and will correspond more closely to that of smaller jet transports. The approach speed of the SP will range from about 135 knots at maximum landing weight, down to about 115 knots at minimum landing weight. At maximum landing weight, the SP will have a landing field length requirement of 6000 feet. The reduced takeoff and landing runway requirements of the SP are expected to enable airlines to provide 747-type service to a number of cities around the world which would not otherwise be able to accomodate any wide-body jet aircraft.

From the ATC standpoint the shorter takeoff and landing runway length requirements of the SP will tend to reduce the complexity of airport traffic control by reducing the number of times the aircraft will require a different runway (which at many airports means a different direction) from the one in use by other aircraft. (This assumes, of course, that the runway with its connecting taxiways is strong enough and wide enough to handle the SP.) At a number of airports throughout the world, IFR approach minima are higher than normal, because of obstructions on the missed approach path, as shown in fig. 1. In such cases, the standard procedure has been to assume that multi-engined aircraft are capable of only a 40:1 climb gradient with one engine out, and the weather minima have been raised so that a 40:1 climb from the missed approach point will still provide adequate clearance from all obstructions on the missed approach path.

However, the Boeing 747 SP will have a climb gradient, with one engine out, much steeper than the 40:1 rate presently assumed. At locations where the critical obstruction is on the missed approach path, a reduction in weather minima would be sate for such aircraft, if regulatory agencies would take into account the performance of the specific type of aircraft when setting approach minima. This would allow the aircraft to descend to a lower decision height, as shown in Fig. 2. Even if the approach were missed at the lower minimum altitude, the high climb 12

gradient would still enable the aircraft to climb well clear of the critical obstructions.

A precedent for this philosophy has already been established in the United States. At Aspen, Colorado, the FAA established lower minimums for Rocky Mountain Airways, based on the demonstrated high climb gradient of their Twin Otter 300 Series aircraft. The capability of using lower minimums increases schedule reliability - with a corresponding economic gain for airline operators and users.

Vortex Dissipation Will the lighter-weight SP be able to provide any relief to the trailing vortex problem? Up to now, Boeing has made no claims that it will. Yet there is a good chance that work now under way by the National Aeronautics and Space Administration may promote faster dissipation of wingtip vortices for the 747 and the 747 SP, on the approach path.

Shortly after the commissioning of the first 747 aircraft in 1968, the FAA set up a new category of heavy jets (defined as any aircraft having a maximum gross takeoff weight of 300,000 pounds or over); and required that air traffic controllers utilize a minimum of five nautical miles separation between a heavy jet and any following aircraft of the non-heavy-jet (under 300,000 pounds max. GTOW) category. The effect of this rule on runway capacity is shown by the lower parabolic curve in Fig. 3. Some years later, the FAA prescribed a 4-nautical mile separation between heavy jets, and the effect of this rule on runway capacity is shown by the upper curve in Fig. 3.

In June 1974, the National Aeronautics and Space Administration purchased one of American Airlines' mothballed 747's, primarily for use in the space shuttle ferry program. However, one of the first modifications to be made to this aircraft was the installation of smoke generators to try out some new techniques for vortex dissipation.

One of the fixes being tested by NASA is the addition of energy to the trailing vortex in order to increase its instability and thereby break it up faster.

When the wing flaps are deployed on approach, the vortices spinning off the outboard tips of the flaps are normally much stronger than those spinning off the wing

Boeing 747 SP Mockup takes shape. The fuselage of the 747 static-test airframe. subjected in structural tests to loads far in excess of those which 747 s would ever encounter in normal airline service. was retired when the static-test program was completed in February 1970. Recently it was brought out of retirement to serve as a major part of the 747 SP (for Special Performance) engineering mockup. The SP fuselage (in foreground), shown here in the Boeing 747 Division mockup area at Everett, Washington, was reduced in length by removing a section 16 feet 3 inches long from in front of the wing and a section 13 feet 4 inches long from behind the wing. A new aft fuselage section, 18 feet shorter than the original 747 s, was installed. The mockup is being used as an engineering tool to "fit-checks" components and the equipment destined for the new superjet derivative. The actual 747 SP will have ten windows on either side of the upper deck. rather than the three windows shown.

tips. This fact is readily discernable from the appearance of the contrails which outline the vortex cores when a large heavy aircraft makes an approach in very humid air.

Normally the flap vortex combines with the wingtip vortex a short distance behind the aircraft, to make one large vortex behind each wing.

The outboard engine on the 747 or 747 SP is very close to the point where the flap vortex streams off the outboard end of the wing flap. Initial model tests indicate that when the outboard engine is developing considerable power, the exhaust can blast the flap vortex out of shape, hastening its diffusion before it can combine with the smaller tip vortex.

Therefore, one procedure which NASA will be testing with their 747 will be to idle the two inboard engines on approach, and to increase the power of the outboard engines accordingly, to inject as much turbulence as possible into the flap vortices, in order to break them up a short distance behind the aircraft. If this technique works as planned, it may allow other aircraft to follow closer behind a 747 with safety - and thus reduce the extra separation required, thereby regaining some of the capacity losses resulting from heavy-jet operations. Obviously, this technique cannot be used for departures. However, NASA has several other promising aerodynamic fixes in the mill, which may soon lead to a major breakthrough in the solution of the vortex problem - not just for 747 aircraft but for other types as well.

30 --~-~,_+-'-c....,..-'-'-~~__........_ o------+-;-.,-,~•-1 • •..L-

'

-· -r-~ '

; ' ' <

.:,

'.

~~ t-+--+f-'-~

~

I

I

25

f-

z

... 20 0

a: ...

0..

~

"' 15 "' 0

...J

>f-

;:; 10 <( 0.. <(

0

l;

3t z·

5

::::,

a:

0 0

40

20 PERCENTAGE

OF

HEAVY

60

JETS

80

IN • TRAFFIC

JOO

MIX

Fig. 3: Effect of U.S. heavy-jet separation standards on runway capacity.

13

Appearance Seen from the front, the 747 SP will closely resemble the 747. From the side, however, its stubbier fuselage will be readily apparent. Because of their shorter distance from the center of gravity of the aircraft, the vertical tail will be about 1o feet taller and the horizontal tail about 6 feet greater in span, to maintain approximately the same stability characteristics as the standard 747.

Besides its reduced dimensions (16' - 3" shorter in front of the wing and 13' - 4" shorter behind the wing) the 747 SP will have a row of 10 windows on each side of the upper deck, in place of the three upper-deck windows of the earlier 747's. The reason for this change is that it is planned to seat 32 passengers upstairs (in place of the 747's upper lounge) to give the 747 SP a total capacity of 321 passengers.

Availability Production of the 747 SP is already under way with the first flight planned for mid-1975 and FAA certification about one year later. As of this writing, Pan Am has traded two 747's back to Boeing as part of the financing for seven 747 SP aircraft. Iran Air has ordered three 747 SP's and South African Airways has ordered three. Deliveries are scheduled to start in 1976. Controllers can look forward with interest to the super performance of the shortbodywidebody 747 SP. (reprinted from the Journal of ATC)

Comments on Air Traffic Control

by Aviation Spokesmen across the World Dr. F. S. Preston, Principal Medical Officer, British Airways, on the subject of food and the controller:

Are you one of these diet cranks who cut out breakfast and rush off on duty with a cup of black coffee and a cigarette? If so, you may be endangering not only yourself but the safety of aircraft under your control.

The body, if it is going to function correctly, and particularly the brain, demands a constant level of circulating blood sugar. This is the fuel we •:require to operate in a normal and rational manner. Normally, when we eat a meal the blood sugar level rises and due to the fact that most foods we eat are converted into sugars and fats in the body, this high post-meal level will last for 2 - 2 '/, hours when it gradually falls. Starvation on the other hand will lower the blood sugar and one can include in this the missing of the odd meal. In such a situation the blood sugar will fall to a level at which the body begins to operate on a low key. The brain and nervous systems are amongst the first affected and there is a noticeable falling-off in brain power, particularly the ability to exercise judgement and make decisions.

Normally the body can mobilise extra sugar by breaking down stored fat - the stuff you have tacked around your waist and elsewhere. But this of course takes time - and in fact it might be several days before you begin to mobilise these overload tanks we carry around and so notice you are getting leaner.

The odd-meal-misser is in a different category. He has all the problems of a falling blood sugar level with its 14

subtle effects on brain power without the ability readily to reverse this process by mobilising his fat reserves. He is therefore very much at risk as far as instant action is concerned and certainly as far as instant decisions are concerned.

There is an additional hazard to the night-shift controller. Due to the fact that we have in-built bodily rhythms - so-called "Circadian Rhythms" - the body's ability to digest and absorb food during the long watches of the night is markedly reduced. In fact most of our digestive processes shut down and we are even less able to increase our blood sugar on demand at night.

Skipping meals is not a good practice, but skipping breakfast is probably the worst sin of all. Why is this? The answer is that during the night our blood sugar, together with other bodily systems, falls to a low level. This is quite usual because the body normally "rests" at this time - that is for all people who work during daylight and sleep during hours of darkness. As controllers however are not in this category you have to fight your bodily rhythms while you are controlling at night. Among these rhythms are a falling blood sugar and body temperature. So, the moral is obvious - if you want to remain at peak performance one of the things you must do is to maintain an adequate blood sugar level. Do not omit meals while on duty. This can put you in jeopardy. A quick boost if necessary can be got from drinking two cups of hot, sweet tea. Remember you need fluid replacement as well as energy. Coffee is not so good as it acts on the kidneys to produce further fluid loss the proverbial race-horse situation!

Richard R. Bowe, Director, Transportation Systems Marketing, Sperry Univac Defense Systems, on the impact of automation on ATC:

Probably the best measure of impact is the acceptance level and nature of the comments from the controllers. It is certainly safe to say that the degree of acceptance has been extremely high. Without question, the operational groundwork that was laid in ARTS I at Atlanta, the ARTS IA in the New York Common IFR Room and ARTS II in Knoxville, contributed greatly to ARTS Ill acceptance. As might be expected from the high degree of acceptance, the nature of the comments has been very positive. To attempt to "average" the comments with respect to impact is meaningless, but there is one consistent theme that bears on controller capacity.

Over and over again, it is said that the system tends to reduce the capacity spread between the controllers. It is now becoming clear that what is happening is that the "hot" controller was operating at full capacity while the others were not. ARTS Ill has brought the newer or average controller some of the tools needed to increase his capacity, thus reducing the spread.

What Controllers are not Although controllers are Public Servants, they do not regard themselves as fitting the popular image of a Public Servant and their training and day-to-day responsibility for rapid decision making makes it difficult for them to accept patiently the lenghty process of decision making that is common to the administrative side of the public service.

(CATCA Information Bulletin)

Future Air Traffic Control Systems An Important New Study by Controller/Pilot Group Foreword In the second part of this series (the first instalment was published in our November 1974 issue), the Air Traffic Control Systems Committee goes on to define the Principles, Objectives and Characteristics of future ATC systems and examines vital Human and Environmental Considerations which affect the efficiency of the Air Traffic Controller. In a following issue, the Committee will examine the effects of these considerations on the Pilot.

The Committee is a private British group which was set up to consider and propose long-term planning concepts for a new ATC system. Its membership consists essentially of ATC users, with advice upon the engineering and ergonomics aspects of system design provided through the Royal Aeronautical Society, and is drawn from the British Air Line Pilots Association, the Guild of Air Pilots and Air Navigators, the Guild of Air Traffic Control Officers and the Royal Aeronautical Society. The work has been in a voluntary and personal capacity, with members being nominees rather than representatives to avoid any formal commitment to particular interests. It is believed that the contribution of this Committee may be unique in the field of aviation, in that this is thought to be the first time such a system design study has been jointly undertaken by the principal users rather than by designers or researchers.

Principles and Objectives of the Future System A number of different approaches can be made to the subject of aims and objectives. However, the committee decided that the principles and objectives of the desired ATC system could most appropriately be set down under three headings, i. e.: (1) Operational Philosophy; (2) Safety Considerations, and (3) Communications.

Operational Philosophy The system must be a strategic one, pre-planned so that it requires minimal (if any) intervention during normal operation. It must be based on airborne navigation (in four dimensions) and regionally centralised ground control (separation and traffic management), and be based on the concept of "protected airspace", i. e. airspace designated for the positive control of all traffic at all times.

So far as scheduled operations are concerned, the system should use pre-planned promulgated tracks/profiles designed to accomodate the peak traffic during the specified period in the most direct and economical manner. The structure should be readily capable of revision and promulgation on a regular basis to allow for predictable changes in air traffic patterns. Any likely overloading of the basic system by scheduled operations should be detectable at the timetable preparation stage and should be accomodated by changes in the track structure or other appropriate action. Tracks within the system should be defined

by geographical co-ordinates and the navigational capability should be specified. The choice of equipment to achieve this requirement should be that of the operator.

The maximum acceptable excursions from pre-planned flight paths, in terms of track, cruising level, forward speed and rates of climb and descent, which may be required by ATC to achieve a safe and efficient traffic flow during routine operations, should be determined. The accuracy tolerances for the aircraft's navigational capability, in terms of track, cruising level, forward speed and rates of climb and descent, which are acceptable to the system, should also be determined.

Those aircraft unable to comply with certain minimum requirements for designiited parts of the protected airspace may be excluded from them. These requirements are likely to be in the form of minimum climb-out gradients, cruising speed(s), descent gradients, communications equipment, navigational performance, etc.

The horizontal dimensions of protected airspace should be determined by the number and separation of routes required within a given airspace, plus a safety allowance on each side of these routes as a buffer to ensure protection from non-participating traffic. Vertical dimensions should be determined by achievable climb/descent/cruising level profiles without the extravagant use of total airspace.

Transit through protected airspace should be available to all aircraft subject to the jurisdiction of a common controlling agency, which may require, inter alia, appropriate navigational and communications capability.

The system should be readily capable of development using inputs from Nav/Com satellites, etc.

Safety Considerations The system must be engineered to operate in a fail-safe manner. The capacity of the system must be planned with sufficient reserve so that the fail-safe quality is retained during predictable peaks and abnormalities. Essential subsystems in the overall ATC system must automatically detect and indicate malfunction as soon as it occurs. The warning must take a form which cannot be rendered inoperative by human intervention.

The management of all air traffic within a defined volume of the airspace must be the direct responsibility of a single controller or of the Manager/Supervisor of a single co-located control team. Operations involving commercial air transport (and equivalent categories) should be planned and carried out wholly within protected airspace. The separation standards to be used should be based on mathematical and practical evaluations linking accuracy, reliability and the target level of safety. (Note: The work of the ICAO Review of the General Concept of Separation (RGCS) Panel should be closely followed). The target level of safety for the system must be determined and be acceptable to all users.

The use of airborne collision avoidance systems (ACAS) as a primary method of ensuring separation is not acceptable. Their use as a possible monitor of the separation 15

provided by the system in order to meet the target level of safety should however be considered. The potential of ACAS as a station-keeping device also merits consideration.

In order to ensure separation to the required level of safety there must be a ground monitor of the aircraft position which is independent of the navigational system(s) in use. The system must be responsive to aircraft reaction under such exigencies as turbulent wake and adverse meteorological conditions, e. g. storm avoidance. Information on adverse meteorological conditions must be provided and displayed to the ground element of the system in order to permit a weather avoidance service, if necessary by the temporary re-alignment of tracks. Constraints on the ground components of the system due to weather affects should be negligible.

In order to minimise inadvertent infringements by other airspace users, protected airspace boundaries should be clearly defined and wherever possible standardised. The system must have the ability to detect any "rogue" aircraft in the airspace. An non-co-operative method of detection is required, e. g. primary radar.

Communications The air/ground exchange of routine information within the system should be basically automatic using established principles such as data link, SSR, etc. The ground/ground exchange of routine information should be instantaneous, using established principles such as Electronic Data Displays, on-line computer/computer links, etc. Voice communications should be supplementary to the basic automatic communications systems, both air/ground and ground/ground.

In the event of an aircraft emergency situation the controller must have immediate and continuous access to all available stored data regarding the aircraft concerned, in a form which cannot be inadvertently erased or otherwise lost.

Characteristics of the ATC Organisation The Committee accepted the following assumptions in determining the characteristics of the required ATC organisation, taking into consideration ,;"the general strategic approach to ATC planning and the conclusions drawn regarding aircraft performance (which were outlined in the November 1974 issue of The Controller).

A fixed route structure, containing the necessary family of tracks, would be established between major terminals.

Parallel tracks would accomodate the climb/descent paths of aircraft of variable performance. For this purpose aircraft would be grouped into standard performance categories.

Pre-planned vertical separation would be the standard method of preventing conflicts between SID (Standard Instrument Departure), STAR (Standard Arrival Route) and en-route tracks.

Appropriate ·4-0 (3-dimensional plus time) navigational capability would be provided on the flight deck to enable aircraft, within pre-determined limits of accuracy: (a) to maintain a defined track; (b) to maintain specified or standard speeds and along-track positions based on time; (c) to follow specified climb/descent profiles.

16

An on-line computer system, ideally consisting of three interlinked sub-systems, would handle the departure, enroute and arrival phases of all flights. Before issuing a departure clearance an acceptability check would be made by the departure unit with the en-route and arrival units.

In the case in which any phase was not "on-line", or where there were a number of en-route interlinked units, acceptability may have to be based on a specified flow rate or on time separation minima, always providing that acceptability was determined well in advance of the aircraft.

The Ground Control Organisation On an appropriate planning time-scale, e. g. on a fiveyear rolling prediction, and at regular intervals, e. g. during seasonal time-table preparation, the effective system capacity must be analysed and any imbalance between the estimated traffic demand and effective system capacity rectified.

A flight plan processing system is required which receives, checks acceptability and stores pre-notified plans, issuing the appropriate information at the action time required or on call-up. A ground monitor system capable of tracking aircraft in all planes, independent of the airborne system but compatible in accuracy with it, is required in order to ensure the acceptable level of safety as well as optimum airspace utilisation.

For direct operational, i. e. dynamic, control purposes, an automated on-line system is needed which is capable of the following nine tasks: 1) checking acceptability of a flight plan to destination and providing clearance; 2) providing revised flight clearances, including departure times if necessary; 3) checking the position of aircraft in all planes against the planned position required by the flight clearance; 4) giving warning of deviations outside specified limits; 5) in the event of potential conflict due to deviation, supplying the controller with specific ATC instructions, or alternative courses of action together with their implications, in order to correct such deviations; 6) providing visual data displays for the presentation of full, updated flight plan and other information in order to facilitate ATC intervention, to correct deviations, resolve conflicts or provide positive guidance to an aircraft unable to conform to the required plan, e. g. due to unserviceability; 7) providing automatically predicted times of arrival of all aircraft at a TMA (Terminal Control Area) holding point or "gate" to the runway(s), based on updated flight plan information; 8) indicating any speed adjustment or holding instruction (based on predicted times) to achieve the correct landing order and sustain an efficient arrival pattern; 9) checking acceptability of, and offering clearance to, "off-route" traffic wishing to enter or transit the system.

General Operational Concepts In order to illustrate the operational concepts to be adopted in a cooperative air/ground system, an attempt has been made to break down the general parameters of

the system into those which can be considered to be fixed and those which are continually variable within the system.

Fixed Parameters (allocated according to standard aircraft performance categories) are: (a) Standard Instrument Departure (SID). The track, speed(s) and levels at which to cross specified conflict points would be stipulated; (b) Standard climb out track, profile and, where necessary, speed; (c) Standard track at cruising level(s); (d) Standard descent track, profile and, where necessary, speed; (e) Standard Arrival Route (STAR). The track, speed(s) and levels at which to cross specified conflict points would be stipulated.

Variable Parameters are: (a) Departure time. This is variable in relation to the acceptability of a flight within the system; (b) Track allocation. Where a choice exists, the allocation of tracks at any stage of flight may be varied to provide the optimum traffic flow; (c) Cruising levels. However, it may be necessary as a standard procedure to place ceiling restrictions on the cruising levels available to flights on medium and short stage-lengths on high density routes, to maintain an optimum traffic flow. (Note: where significant variation to the cruising level is required

by ATC, adequate warning must be given to the operator). (d) Speed. This will be varied to allow for finite adjustments of aircraft spacing. Conventional holding patterns may not be the most economical method of regulating the traffic flow to an airport, although it may be necessary, in any event, to retain this capability, in order to deal with unforeseen circumstances, e. g. runway blockage, weather deterioration, etc. (e) General aircraft performance. Acceptability and conflict probes should be able to indicate that, due to the traffic offering to all or part of the system being below the available capacity, or due to a "no conflict" situation existing, aircraft should be allowed to disregard any restf+ctive standard speed and/or profile requirements and operate at their optimum performance.

Communications - the following arrangements would be standard: (a) Air/ground communications for all routine operations would be by data link. (b) Direct pilot/controller voice communications would be retained for non-routine and emergency situations.

Note: A very high degree of confidence will need to be engendered before item (a) can be implemented in full.

Even then, the requirements of pilots and controllers to establish satisfactory mutual relationships might preclude total implementation.

Control Functions It is assumed that the system will be capable of the nine functions listed earlier (see "The Ground Control Organisation") in respect of three classes of aircraft operations: -

(a) Operations contained entirely within the automated system and following the fixed route structure; (b) Operations generated outside the automated system wishing to enter the system and subsequently follow the fixed route structure; (c) Operations generated within or outside the automated system but either unable to conform to the fixed route structure or requiring to transit only part of the route structure.

Controller Responsibility - in respect of operations contained entirely within the automated system and following the fixed route structure, controllers will be responsible for: (a) the input of the flight plan and checking its current acceptability; if the filed flight plan is unacceptable, offering advice to the operator on suggested alternatives; (b) the advice to the operator, at the earliest possible time, of any significant delays in the system, with reasons; the advice should also contain the revised departure time; (c) the input of the updated departure time, checking the final acceptability of the flight and issuing the clearance. (Note: this procedure will be initiated at the time the pilot requests start-up clearance); (d) the input of the actual departure time; the subsequent monitoring of the system for warnings of deviation from cleared flight path; the decision whether such deviations require continuous positive control or short-term assistance or other appropriate action; (e) checking the credibility of machine-derived solutions to the nine traffic problems outlined earlier under "The Ground Control Organisation"; (f) classification of unusual situations to enable them to be handled by the automatic system in the most efficient manner; (g) executive choice between alternative strategies which the machine may suggest; (h) communicating to the pilot any revisions to the planned flight path, e. g. speed adjustments, required to permit'. integration into the terminal arrival system; (i) transfer of control to the adjacent unit at the appropriate time/place.

In respect of operations generated outside the automated system wishing to enter the system and subsequently follow the fixed route structure, the controller will be responsible for the procedures listed above under "Controller Responsibility", except that "departure time" is interpreted as the planned/actual time at which the operation enters the route structure of the automatic system. (Note: Although the clearance issued will be effective only from the entry position, positive control or manual monitoring to ensure adherence to the required clearance will be initiated prior to entry and be continued until the flight is integrated into the automated system).

In respect of operations generated within or outside the automated system but either unable to conform to the fixed route structure or requiring to transit only part of the route structure, the controller will be responsible for: (a) in the case of aircraft unable to conform to the requirements of the fixed route structure, providing manual monitoring/positive control at all times to ensure separation from other traffic;

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(b) in the case of aircraft transitting part of the system, ensuring the separate input, clearance and automatic monitoring through that specific section of the route structure.

Human and Environmental Considerations General In the type of Air Traffic Control system which is envisaged, where human controllers and pilots are confronted with increasingly complex automation, the environment in which they work becomes of even greater importance than it is today. Experience has shown that too little attention has been paid in the past to human and environmental (ergonomic) factors when designing ATC systems, equipment and accomodation. If the importance of these factors is not recognised and acted upon, many of the benefits otherwise accruing from the system may be significantly degraded or even lost.

The discussion which follows concerns the ergonomic aspects relating to: (a) the controller; (b) the pilot; and (c) the types of contingency with which either or both will be faced from time to time.

The Controller It is believed that the controller's environment plays a major part in determining his efficiency and, therefore, the efficiency of the system as a whole. Historically, the Guild of Air Traffic Control Officers presented to the National Air Traffic Services, in August 1972, the results of a critical examination of the Mediator system in use at the London ATCC. The Guild expressed its concern at, inter alia, the shortcomings of that system as regards ergonomics and data displays, and made appropriate recommendations.

Although essentially concerned with comparatively shortterm improvements to the current ATC system, a number of conclusions and recommendations which were reached have long-term implications insofar as they reflect the required interface between air traffic controllers and their displays and automatic assistance. Both this document and other similar papers are relevant, it is believed, to the design study of the future system.

The use of proven scientific principles in the design of ATC displays and associated equipment cannot be too strongly emphasised. It is not sufficient to leave such work to the controllers and the electronic engineers alone: it is necessary also to bring the ergonomic and the medical specialists into the design team in the earliest stages.

Similar considerations apply when examining the controller's surroundings in the control room. Such things as control room lay-out, heating, lighting, seating, acoustics and decoration merit careful attention. Unlike the pilot's environment, which is governed to a considerable extent by the shape and size of the aircraft, the controller's physical environment is capable in most instances of approaching the ideal. With the advent of advanced methods of data transmission and presentation it should be possible, therefore, to build and equip control rooms wherein the efficiency, well-being and morale of the controller can all be assured.

However, the controller's efficiency is not wholly dependent upon his physical environment. It is already evident 18

that modern automated techniques could so change the nature of the task as to place additional stress upon him.

Stress may also be caused by what appear to be shortcomings in management at all levels - a point which is frequently ignored.

Recommendations concerning these and other factors are included in a summary which follows below. Probably the more important of these concern the psychological and organisational factors. Although less tangible than those regarding the equipment and general ambience in the working environment, it is likely that they contain the key to successful progress.

What may not perhaps be readily appreciated is that the function of a controller, while much more specialised and not nearly so diverse as the pilot, is bound to change markedly within the next 10 - 20 years. While safety from collision or near-collision will still be his fundamental responsibility, the task of the controller will increasingly embrace air traffic management aspects in order to optimise the use of airspace. He will be aided by fairly advanced computer technology, and will require training in contingency actions to an extent never thought necessary until now. The future environment created for the controller will, therefore, have to take account of these considerations.

The human and environmental (ergonomic) factors affecting the efficiency of the controller within the system are discussed under the broad headings of: (a) The Equipment - those factors directly concerned with the design of the equipment with which the controller is expected to carry out his functions; (b) The Ambience - those factors which affect his efficiency as a human being concerned with the task of controlling aircraft; (c) Psychological and Organisational Factors - those less tangible factors which affect the efficiency of the controller and which concern the nature of the task, reliability of equipment and relations with management.

The Equipment It is considered that a basic display system should be developed which is capable· of being adapted to suit any control task, including live and synthetic training, in any country. Great emphasis must be laid on the use of sound scientific principles in the early design stages, coupled with comprehensive evaluation trials to ensure that the controller's display is self-evident to trained personnel and provides all essential information appropriate to the specific controller and to his current traffic situation by ergonomic methods of presentation and selection. Account must be taken here of the requirements of training and supervisory staff.

The following recommendations are made with a view to achieving these aims: The level of illumination at the controller's workplace should match the display information characteristics at a level which is appropriate to the task in hand. Facilities must be available to allow the individual to exercise personal preference to some degree without interfering with the requirements of others.

The controller should have control over the intensity of any display which involves the transmission of light, within efficient operational limits. Primary information, i. e. information directly related to the traffic situation, should be

displayed in such a way as to avoid significant refocussing of the eyes.

It is possible that large displays of secondary information, i. e. information not concerned with the traffic situation, may not be practicable. Research should be done on the best methods of storing and presenting such information to the controller as the requirement arises.

Such elementary facilities as the provision of space and materials for writing notes must be provided.

The manipulation and selection of facilities, whether data displays or communications, should be simple and self evidently related to the task and the displays in use.

As much ancillary equipment and as many ancillary functions as possible, e. g. secondary radar code selections and code allocations, should be removed from the immediate vicinity of the controller's console.

The Ambience The following points are recommended as worthy of consideration under this heading: The traditional large control room containing several sectors or functions should remain, if only for ease of liaison and supervision. Windows which provide a sight of the outside world but do not allow direct solar light to cause contrast or temperature problems might be of psychological benefit.

Attention should be paid to the acoustic design of control rooms and equipment with the aim of achieving 3 noise level which, while not being sufficiently low to deaden alertness, would not impair concentration or interfere with speech. The temperature in control rooms should be controllable within defined limits to take account of the varying requirements of the human body by day and night.

Provision should also be made for the control of humidity and for the introduction of adequate supplies of fresh, filtered air.

The design of chairs should take into account not only the need for compatibility with the display console, but also the need to provide a comfortable, mobile and adjustable seat to suit the requirements of individuals of varying size and proportions. To this end it will probably be necessary to make more than one design of chair available at any given location.

Whilst the decoration of- control rooms will need to take into account the purpose of the room and the type of equipment and lighting, the use of both very dark and very light colours should be avoided where possible. It is thought that the use of some areas of contrasting colour might help to maintain alertness. Gloss finishes and bright metal fittings should be avoided in order to prevent distracting reflections. Generally the decor should give some visual/mental comfort to the control staff and hard futuristic metallic/plastic designs should be avoided.

The layout of control positions and facilities should be freely adaptable to meet new operational requirements.

To this end planning should ensure the greatest operational efficiency and a good working environment. Photogenic quality either of the control room or of individual positions is of a lower priority.

Psychological and Organisational Factors The controller should not operate solely in a monitoring capacity, nor should his task be concerned only with routine data entry and retrieval within a highly automated

system. Not only may the monitoring function impose unacceptable strains upon the controller, but any task which allows no scope for the exercise of his experience, judgement and skill must be expected to lead to a loss of job satisfaction and a consequent lowering of morale and efficiency.

Care must be taken that the controller is not subjected to overlong periods of continuous operation or to situations where he is being outpaced by the system which he is endeavouring to control, as both these conditions, either separately or together, may lead to human error.

It is essential that the controller should be able to trust the quality of the data and the equipment with which he is carrying out his task. Any suspicion about the reliability of an automated aid may quickly lead to unacceptable anxiety.

It has to be appreciated that Air Traffic Controllers, as human beings, will be beset by a number of fears or anxieties when confronted with automatic assistance of the kind described in other parts of this report. First and foremost, the safety of aircraft in the system will be safeguarded by a combination of human and automatic responses to the traffic situation. It is imperative, therefore, that the responsibilities of the Air Traffic Controller, as distinct from the responsibilities of the equipment and those associated with its technical efficiency and programming, should not only be understood but also set down in unequivocal terms. Secondly, the Air Traffic Controller should not be employed in making good deficiencies in the automatic system by having to comply with special procedures which form no part of an instinctive unautomated control function. To do so would create additional and, it is thought, unnecessary stress. Finally, from long experience the Air Traffic Controller mistrusts new automatic equipment, whenever and wherever it appears. This mistrust arises from a very proper regard for his responsibilities for flight safety. Consequently, to ensure the efficiency of the ATC system by obtaining optimum human and machine performance, it will be essential for the human controller to understand completely the role of the machine, including the fail-safe or fail-soft provisions made to cover malfunction sjtuations, and for the machine to be designed to match the capabilities and requirements of the human controller.

Management attitudes towards staff may have a considerable effect on the efficiency of the ATC system. Such matters as training, shift systems, rotation of operating positions, rest facilities and reaction to human error can bear upon the morale and, therefore, the efficiency of the controller. The aim should be an atmosphere of mutual confidence and respect between management and staff.

A True Story from an Unnamed Capital City APP:

SK 098 maintain heading 350 for radar positioning R/W 03 L. SK 098: Request heading 340 to avoid CB. APP: Negative, maintain 350.

SK 098: Heading 350 will take us into a CB- 340 just outside.

APP: Unable to approve - you will fly over the King's Palace!

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Airport Surface Detection Equipment Radars

by C. F. Phillips, Jr., Aerospace and Electronic Systems Division, Westinghouse Electric Corporation·

Introduction The problem of handling surface traffic at major airports under conditions of poor visibility is ever increasing.

New advances in landing systems with their decreasing landing minimums are adding to the airport surface control problem. Under poor visibility conditions, the ground controller is often forced to rely on VHF voice communications by asking the pilot for position reports. He may be forced to sequentially meter departure traffic into the taxiway network in order to limit the total number of aircraft under ground control. Clearly there is a need for providing the controller with some means to alleviate this situation so that both an increase in the ground traffic flow and an increase in safety can be provided under these conditions.

Canadian ASDE Program The Canadian Ministry of Transport has awarded a contract to the Mitsubishi Electric Corporation (MELCO) of Japan and to Canadian Westinghouse Electric Corporation for the procurement of an Airport Surface Detection Equipment (ASDE) Radar. Delivery was scheduled for the end of 1974. Canadian Westinghouse was made responsible for the system check-out and installation and will also manufacture any follow-in production equipments, should they be procured.

The new radar for Canada is based on the design of MELCO ASDE's which have been in use since 1961 at Tokyo, Nagoya, Osaka and Chitose airports. It is a very high frequency, high resolution radar using an antenna with a 10 foot width. This antenna, operating in the 24 GHz frequency band, provides an azimuth beamwidth of less than 0.3 °. The transmitted pulse width is 20 nanoseconds which in combination with the narrow beamwidth provides the very high resolution. The writer has observed this radar in operation and the display is most impressive and apparently is of great value to the local and ground controllers under conditions of poor visibility due to rain, fog, smog, etc.

The Japanese ASDE antenna rotates at 500 RPM in order to provide a bright display to the controllers in the tower cab. With this extremely high rotational rate, the antenna is too heavy for mounting on the top of the tower cab. Consequently the antenna/radome assembly is placed

• Mr. Phillips is Program Manager Air Traffic Control, which position he has held since 1967. This position involves civil and military Air Traffic Control, both en-route and terminal, dealing with radars, beacons, automation, displays, landing systems, etc. From 1964-1967 he was a system design consultant on the NATO Air Detense Ground Environment System (NADGE), the Swiss Air Defense System (Project Florida), the Swedish Air Defense System and the Australian Air Defense System, and has also been associated with the design requirements for various tactical and weather radars, GCA systems, personnel detection systems, etc. Mr. Phillips, who has had 7 patents issued, holds a B. S. in Physics; has attended the U.S. Navy Research Laboratory Radar School, and the Temple University U.S. Signal Corps Radar School. He Is a registered Professional Engineer - Maryland.

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in front of and below the tower cab or on a separate tower at the Japanese installations. In the case of the Canadian requirement, it is desired that the weight be reduced to allow for mounting on the top of the tower cab. To meet this reduced weight requirement the antenna, radome and pedestal structure has been modified slightly and the antenna rotation rate has been reduced to 200 RPM. The speed reduction has allowed for the major weight reduction with the associated necessity of supplying a scanconverted TV type of high resolution bright display instead of the conventional PPI display. The parameters of the new Canadian ASDE Radar are given on page 51.

Existing United States ASDE Radars The United States, approximately 15 years ago procured a number of ASDE radars whose electrical characteristics are similar to the Japanese ASDE. These radars had the nomenclature ASDE-2. Although this radar was considered very advanced at the time it was developed, the use of vacuum tubes (or valves) made the radar quite unreliable and very expensive to maintain. Also, there was difficulty with the radome and the controller was not provided with a bright display. (The display used a conventional PPI with a hood and was very bulky which made it almost impossible to use.) The radar also performed very poorly under heavy rainfall conditions, a condition where its use is most important. For these reasons, the ASDE-2 radar gained a very poor reputation and many of the radars were decommissioned. Unfortunately, the radar is now badly needed for the reasons stated in the introduction and the Federal Aviation Administration is now starting a program of updating these radars with the hope they may be useful until a new ASDE can be developed.

New ASDE Program in the United States The Department of Transportation, Transportation Systems Center, Cambridge, Mass., in conjunction with the FAA, is launching a major effort directed at the airport surface traffic control problem. The broad objective of this program is to increase surface traffic handling capacity, minimize surface traffic delays, and provide an all weather control and guidance capability up through an ILS Category Ill operational environment. As a part of this program, the development, test, and evaluation of a new ASDE (ASDE-3) is planned. This effort in conjunction with the ASDE program in Canada should result in a next generation ASDE with proven performance as well as highly reliable hardware.

It is hoped that the output of the new ASDE or any other similar surveillance system developed under this program can result in an automated system much like the ARTS Ill. Ultimately, on a long term basis, it is hoped that a fully automatic ground control and guidance system can be developed to greatly relieve the controller workload as well as to improve overall system performance and safety. (cont. page 51)

A New Generation of Equipment for Dutch Airspace

by David Woolley, Editor of AIRPORTS International

Control Tower, Amsterdam, Schlphol Airport, at night.

The Netherlands has played a leading part in the modernisation of Air Traffic Control Systems and in the introduction of automation. The country's Civil Aviation Authority (RLD) has embarked on an important programme of re-equipment for the Air Traffic Control Centre at Schiphol (Amsterdam) Airport.

The Dutch company specialising in Air Traffic Control, and which is the main contractor for the modernisation programme, is Hollandse Signaalapparaten of Hengelo, a member of the Philips group (and a Corporation Member of IFATCA - Ed.). The company's new ATC system has been named SARP (Signaal Automatic Radar Processing), and in its first stage, SARP I, it has entered service earlier this year with Approach Control at Schiphol, working in conjunction with - but separately from - the older SATCO flight-plan data system. In its second stage - SARP II, inauguration of which is due to take place in 1976 - it will be used for Area - as well as Approach Control. SARP I will be integrated into SARP 11,and SATCO is then likely to be retired, leaving SARP II to perform the entire processing function of both radar data and flight plans.

As it exists at present, SARP I displays raw as well as digitised radar video. SARP II will make the important step to an all-synthetic presentation. Thus synthetic displays will be expected to provide sufficiently high-grade information for the sequencing of traffic in the Amsterdam Terminal Area, as well as for Airways work.

An obvious difference between SARP I and SARP II will be the use of random-access bright displays in the latter, with 23 in (58 cm) cathode-ray tubes. The SARP I displays are not entirely conventional, in that use is made on the plan-position indicator of two colours - white and orange for easier legibility.

To put SARP in perspective, it is worth recalling earlier developments. Signaal was formed in 1922 as a precision engineering concern; it was nationalised after the second world war (on grounds of being enemy-controlled) and then sold to Philips, the Government retaining an 8 per cent share. The company, already making mechanical analogue computers, then entered electronics and claims to have been the first in the world to introduce digital techniques to gun laying and fire control. The interest in precision 21

engineering still persists, and has found application in the construction, for example, of radar antennae.

From radar and gun laying it was but a small step to Air Traffic Control. As Mr. E. C. Priebee, Signaal's senior ATC systems engineer, points out: in the one you arrange for two objects to meet, while in the other you arrange to keep them apart. Mr. Priebee underlined the company's ATC systems philosophy of leaving the executive decisions with the human controller, and using the system to reduce the data to what is relevant and to present it to him.

Schiphol was a pioneer in ATC automation in the 1960s with the introduction of Signaal's SATCO system. Initially it was a flight-progress strip-printing system, with calculation of flight-plan data. In 1964 SATCO was up-graded by the installation of the world's first automatic flight-progress boards for Airways procedural control. In this system conventional strips were replaced by small electro-mechanical alphanumeric indicators. With hindsight, one might suggest that it was a mistake to attempt the automation of purely procedural control; the subsequent trend has been towards radar processing. In any event, SATCO paid the price of pioneering and ran head-on into resistance from the controllers, and it had to be redesigned in 1965. SATCO II was phased in during the years 1966 to 1968, gained general acceptance, and is serving the Amsterdam Centre today.

The system processes flight plans, revisions and clearances, and distributes basic and up-dated flight-plan information by means of automatic displays. It also gives conflict warning to planning controllers and provides procedural co-ordination between sector controllers.

Forecasts of traffic growth at Schiphol suggested that an ATC system was needed which would enable Approach controllers to handle at least 80 movements in two hours at traffic peaks, with 40 of these movements giving an ETA within 30 minutes. Such capacity was a basic design objective of SARP I. The decision to order SARP was based not only on the forecasts of traffic growth and the workload it was likely to impose on control staff, but also on an assessment of ATC developments in neighbouring countries. Netherlands airspace is small - only some 500 by 250 km (300 by 150 miles) at its greatest - and coordination with neighbouring control authorities assumes

Console of SARP I with two-colour

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display and lightpen.

considerable importance for the Dutch. Liaison with such centres as London, Maastricht and Millingen has been a major consideration in the design of the SARP system.

SATCO offered no radar data processing, and, rather than extend it for this function, the RLD decided to start afresh with a new and independent system. The order for SARP I was placed in 1970, and installation was complete by September 1973. Training has been in progress since then until the system was taken into full operational use early this year.

The structure of Netherlands airspace has been modified in recent years. Dual-track Airways have replaced the old single-track arrangement; this lateral separation of opposite-direction traffic has removed one of the causes of excessive workload, given the high proportion of climbing and descending traffic found in Dutch airspace. The dual-track routes all converge on two VORs in the Amsterdam Terminal Area, Spijkerboor and Pampus.

The Schiphol Centre is organised into five Airways sectors and three stacking sectors. Standard approach routes (STARs) and standard instrument departure routes (SIDs) are in force. The STARs lead from the three stacks at the edge of the TMA to a vector area which is in principle separated from the outbound routes. Here aircraft are sequenced onto final approach.

The Approach Control unit consists of an Approach controller, who coordinates the inbound flow; a Feeder controller, who handles traffic from TMA entry to the vector area; and a Director who takes inbounds through in the vector area and onto final approach. There is also a Departure controller, and a no. 2 Director, the latter chiefly concerned with inbound and outbound traffic for other airfields. These airfields include Rotterdam and three military airfields.

Data inputs to SARP I include flight-plan data from SATCO and primary and secondary radar from two radars.

As mentioned above, mixed raw and digitised information may be presented on the PPI. Labels are added, giving identification, flight level or altitude, and speed. Flight data is displayed on an electronic data display (EDD), and may be transferred in condensed form from there to a "minitable" on the associated PPI. Computing facilities available to the controller include calculation of EAT (expected approach time) and slot time (time at the approach gate, about 10 n. m. from touchdown); calculation and display of range and bearing; compilation of an entry sequence list or stack list from the flight-plan data, which can be displayed on the PPI; and the limited recording of controller inputs. In addition there is provision for the calculation of distance from threshold to be displayed to the Tower controller.

Processing capability of SARP I is based on two Signaal SMR computers (capacity, 64k words of 24 bits) and three memory drums, each with a capacity of 512,000 24bit words. One drum acts as a stand-by and can replace either of the two other. An installation with six PPls can in principle accept 50 active flight plans and 150 passive (undisplayed) plans from SATCO. The video extractor subsystem can process up to 125 plots per antenna revolution, and of these 50 can be tracked. Total load on one EDD is 32 lines of 64 characters each, with a maximum of 10,000 characters on seven EDDs. The introduction of SARP II in 1976 will involve the transition to all-synthetic displays.

When SARP I was ordered in 1970, a conservative body of opinion among controllers insisted that a raw radar

Console of SARP II with the following configuration: Position 1: Director-Controller Position 2: Feeder-Controller Position 3: Departure-Controller Position 4: Masterprinter for Computer Inputs Position 5: Director No. 2 - Controller Position 6: Spare Unit All units are interchangeable.

back-up was essential. A series of simulator trials and close technical liaison with the manufacturer appear to have brought reconciliation with the idea of relying on synthetics, even in the TMA. There will however still be an emergency facility by which the raw radar plot, including height, can be routed direct from the radar digitiser to the display computers, giving the controller just a code and a height.

Important new facilities to be offered by SARP II include conflict search and a rudimentary form of conflict resolution. Conflict search is performed in respect of overflying traffic above FL 100 at the two VORs at Spijkerboor and Pampus, and for traffic at the boundary reporting points with other centres. Conflict search is based on flight-plan data up-dated by radar inputs. The controller is alerted by a flashing "C" on his PPI label and his EDD. Conflict resolution takes the form of a facility by which the controller can call up conflicting flights to his display, and ask the computer for the next available flight level.

SARP II will assist the Approach planning controller by calculating the optimum order for aircraft to leave the stacks. The calculation is based on runway-in-use data and predetermined separation standards.

A flow-control facility is also planned, with calculation of the number of flights that can be loaded on to a given Airway. The Tower controller can ask the computer for a departure time from Schiphol calculated with reference to flow-control requirements and to possible conflicts up to the airspace boundary. A display in the Tower would give the advised departure time.

Each of the five Area sectors at Amsterdam will normally be manned by two controllers - a radar controller and (seated at the EDD) a hand-off controller. Flight plans will be routed through a flight data section, and all airline schedules will be stored on tape (as is current practice with SATCO). An automatic link with the AFTN (aeronautical fixed telecommunications network) is planned.

The radar data will be obtained from two stations - the Schiphol Terminal Approach radar and the distant long-

range radar at Herwijnen. Each station has one primary and two secondary radar antennae and associated video extractors. Electronic units - but not the antennae - are duplicated, and there is emergency power supply, dual telephone lines and a RF telephone link to guarantee reliable flow of radar information.

Incoming digitised radar data is processed first by two Signaal SMR-S mini-computers (12k words of 24 bits) which correlate the data with relevant extracts from the flight-plan data. Also in the main computer complex are two SMR processors which perform additional radar processing, such as adding labels, with three drum memory units and two interface units. Again duplication is the philosophy; one unit of each type is active and the other is on stand-by, under the control of the monitor unit, which acts automatically to replace a defective unit with its stand-by.

There are five other principal sub-systems. The EDD sub-systems is fed direct from the main computer complex; if a failure of the latter interrupts data input, the EDD subsystem can continue to display data from its own memory.

The display capacity of each EDD is 32 lines of 64 characters. A total of 26 EDDs are envisaged, but maximum capacity is 64.

The teletypewriter sub-system links the system to Rotterdam and the military control centre, but there are also terminals at each Airways sector, which could be used for example by the controller for insertion of flight-plan data where necessary. The sub-system will drive 32 teletypewriters, but has a capacity of 48.

In general SARP II is destined to function without the use of conventional flight-progress strips, but strip printers are to be provided in the Schiphol Tower and Flight Information Centre.

The magnetic tape sub-system provides a bulk store for programs for initial loading, flight plans, and legal and statistical records.

The software sub-system assigns programs to the computers under three main categories - operational, test and programming-support programs. Flight-path calculation, 23

radar processing, conflict search, flow control, acceptance of AFTN messages, height-band filtering, and automatic SSR code allocation are just a few of the main functions, most of which have been mentioned previously.

Signaal officials draw particular attention to the display sub-system, and to the 23 in random-acces bright display.

The latter was the outcome of a fierce battle between Signaal and Raytheon to meet a Dutch Government order; Signaal designed the display in five months and won the order. The display is now in production and has won RLD approval. The tasks of the display sub-system, apart from presenting data on the synthetic plan display, are to process inputs made by controllers and to operate in the backup mode if the main computer complex should break down. Eight satellite computers each control two displays, with a connection scheme designed to ensure that failure of one satellite does not incapacitate both the displays on one sector.

One function of the satellite computers is to generate an artificial afterglow for plot and track positions (appearing on the display as a series of dots). This compensates for the very short-persistence phosphor used to coat the screens.

Plot information is subjected to the tracking procedure, which filters out information from military transponders (displayed but not processed further), and converts remaining plots into tracks. The track is compared with flightplan data for purposes of identification; where identification is achieved, the track is displayed with a special symbol (a star), which may then be replaced by one of several "under-control" symbols, allocated according to which controller is handling the traffic in question.

To avoid cluttering the display, the labels are restricted to three lines each of seven characters. A light pen enables the controller to identify quickly items of information on the display. Principal ATC functions are displayed in a block and can be actuated with the light pen, thus avoiding use of the keyboard.

A possible future development of the bright display is the use of four colours, based on the Penetron tube. Signaal is conducting investigations into the possibilities, but officials point out that the question of economics will influence the outcome.

(Footnote: AIRPORTS International Is the official Journal of the International Civil Airports Association. It Is the declared aim of David Woolley to cover the field of ATC developments widely, and for this reason alone the magazine should be of interest to controllers the world over)

mated system and keep it safe. The airlines know this and have continually pressed for more and better facilities, better working conditions, adequate staffing, early retirement, and the like. We are also aware that the initial steps in automating the ground system has had a favourable impact in reducing controller workload, and we will support efforts to further reduce the manual tasks of the controller.

We are proud of the ATC profession and the job it is doing.

I believe all of us realize that the cost of doing business is increasing at an alarming rate, and will continue to increase - making it mandatory to keep costs to a minimum consistent with good judgment. Unfortunately, the number of ATC delays are also increasing, as well as their costs, thus compounding the situation. In a recent survey, we found that airline delay costs due to ATC related causes are estimated to be currently running at about $ 6 to $ 7 million a month, or about $ 80 million a year, and are on the rise. Expenditures for advanced airborne systems to complement ground systems could well be considered a good investment if, in fact, there is an identifiable payoff in delay reduction.

Looking. at the adverse effect of ATC delays from yet another viewpoint and one in which all of us are becoming increasingly aware is their impact on the energy crisis.

ATC delays waste a valuable, scarce energy resource -fuel.

It has been estimated that due to ATC system inadequacies, the U.S. airlines are wasting as much as 130 - 150 million gallons of fuel per year. For example, one minute of flight time costs on the order of $ 7 to $ 15 or burns 25 gallons of fuel. Multiply this times 20 or 30 minutes then times the number of aircraft delayed, 40 or 50 per high density airport, times the number of airports involved, and the cost and fuel wasted becomes a substantial figure.

All of us must be on guard that we do not become over confident in the machine's ability and end up with something worse - a mechanical monster. I think we all recognise that the automatic system with its computers is only as good as the man-developed input it receives to do its thing. We must also be aware that we easily can become its servant, if we are not careful and we work for it rather than it serving us. In the airlines, we see signs of this even today as we begin our cutaover to NAS Stage A and ARTS Ill. We are having to tailor many of our ways of doing things to what the machine wants or will accept. For example, flight plan filing now must follow a computer format. How many of us have had horrible experiences with computerised (automated) billing by department stores?

Let's insure that we will not have similar experience with the automated ground ATC system.

Comments on Air Traffic Control

by Aviation Spokesmen across the World What is an Air Traffic Controller?

William T. Hardaker, Assistant Vice President-Air Navigation/Traffic Control, Air Transport Association of America, on an essential part of the ground ATC system - the man:

Men are and will continue to be for the foreseeable future the true backbone of the system and, in the last analysis, must be in control of the system. Even with the best automation equipment in the world, the ATC system would not function without them. It is the controller who with the best and most efficient on-board computer in the world (the human brain) provides the fine tuning that will wring out the last ounce of capacity in the ground auto24

An air traffic controller is a person of Solomon's wisdom, sitting in an ivory tower, from whence he sees ail, hears all, and confuses all through equipment of mongrel manufacture, erratic serviceability and random maintenance, chosen to be only suitable for traffic conditions during a solar eclipse on a Friday afternoon, by a procurement officer whose knowledge is derived from advertisements of irrelevant subject intended to mislead and confuse, sponsored by a foreign manufacturer in a foreign aviation publication. (not in 'The Controller', we hope? - Ed.) (Airport News, Dorval)

International Law

by E. McCluskey

Part 7: International Violence and International Crime Clearly the ideal in any legal system is the rule of law and order. In any legal system there must be rules to prevent violence and crime and a police force and a judicial system to see that these rules are applied and if not the transgressors punished. Nevertheless there is difficulty in the international field both for policing and bringing offenders before the courts since in many cases the offenders are States themselves. Being sovereign States they can decide whether or not to accept "police action" and they need not submit to international arbitration if they do not wish to do so. So just as in municipal law one is entitled to defend oneself against attack by a criminal so in international law subject to treaty provisions violence and war are permitted if they are carried out according to law.

Anything short of war does not affect legal relations between States under the Law of Peace as opposed to the Law of War. Since War is illegal for signatories of the United Nations Charter, States have U$ed everything short of war since the cessation of hostilities in 1945. Yet we may reasonably ask: "if war is illegal, what went on in Korea, Malaysia, Indonesia, Israel, Pakistan, Vietnam, Laos, Cambodia, etc., not to mention the hundreds of border clashes throughout the world?" Each case amounted to one State engaging in war with another under the guise of another form of legal violence. In other words, they did not declare war so did not infringe the United Nations Charter.

The world is yet a long way from the ideal of international law and will remain so as long as politicians play the legal system when it suits them and abandon it when it does not. Clearly disputes will always arise but it should be the aim of every State to settle disputes peacefully using the principles of law which we have already discussed in previous articles or by using the good offices of a third party in arbitration or by submitting their case to the International Court of Justice and more important accepting the decision.

No doubt some States do just that, but as long as all do not then methods must be available short of war to bring recalcitrant States to their senses. The first method is retorsion. Retorsion is retaliation for an act which though legal is discourteous or inequitable. Although it may not be the same act in reverse, it must be on the same scale and not more. If one State adopts an economic policy damaging to another, the other State might decide to ban the fishing vessels of the first from territorial waters where they were previously free to fish. If one State applies medical examination to the workers of another State in conditions unfit for human beings, the second State might apply abusive delays and rigorous examination of passports and baggage to tourists from the first State.

The second level of legal violence is reprisals. This has frequently been used by Israel in recent years. The Naulilaa Case 1928 covers this field. In 1915 while Portugal was neutral, an incident took place at Naulilaa on the Angola-German South West Africa frontier. Three Germans were killed. Germany as reprisal attacked several frontier

posts and drove out the garrison of Naulilaa. There was a resultant uprising in Angola which required a considerable Portuguese interve·ntion. Germany's plea of reprisal was rejected as the first incident was clearly established as a misunderstanding; Germany did not ask for redress and the action taken was excessive. The act of reprisal may be committed against any and everything belonging to the wrongdoing State or its subjects except the Head of State or a diplomatic envoy. Individuals seized are hostages, not criminals, and cannot be subjected to punishment.

Intervention is the next stage to be discussed and it brings us back to the case of Cyprus which we mentioned in the last article. Intervention is a dictatorial interference in the domestic or foreign affairs of another State which impairs that State's independence. The interference may be to maintain or alter the existing state of affairs. Interference with the affairs of another State is illegal so any intervention must be justified under one of seven recognised headings. Intervention is legal in the affairs of a protectorate. This is the United Kingdom's justification for her policy towards Rhodesia. The second possibility is intervention in matters which are the joint concern of both States if for example one State concludes a treaty inconsistent with one previously made with the second State.

The third case is if the form of government has been guaranteed by the intervening State and is in danger. In 1903 the Treaty of Havana gave the United States the right to intervene in Cuba for the preservation of its independence, the maintenance of a government adequate to the protection of life, property and liberty. As we saw in the last article, Turkey intervened in Cyprus under the Treaty whereby Greece, Turkey and the United Kingdom guaranteed the independence of Cyprus and the form of government in Cyprus. This is the only heading under which Turkey could act. The fact that she continued the invasion to the extent of occupying a large part of the State and has attempted to suggest a new form of government for Cyprus would appear to give a prima facie case that Turkish intervention was excessive. Another form of intervention is to protect one's citizens abroad. The United States has frequently used its sixth fleet in the Mediterranean for this purpose but has withdrawn immediately the crisis was over. Another form of intervention which has become a legally recognised method in recent years is intervention under the United Nations Charter to restrain States from disturbing the peace. In 1950 a United Nations Force directly responsible to the Security Council intervened to protect South Korea. Intervention is allowable also in the interests of humanity. In the 19th Century the Great Powers frequently intervened in the Turkish Empire to protect Turkish nationals. Intervention is also permitted to force two States to arbitrate rather than fight.

Another form of violence short of war is pacific blockade blockading against the ships of one State. Such a blockade must be fully effective to be legal. The blockade of Rhodesia was never fully effective.

Self defence is of course one of the pinciples of International Law. It is only legal in absolute necessity and the 25

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amount of force used must only be to the extent of the necessity. Invasion is justified to prevent a body of men across a border arming for hostilities. Israel has used this on frequent occasions.

The next step is declared war. War is illegal for the signatories of the Kellogg Pact and of the United Nations Charter. The aggressive character of a war is judged by objective standards. Once a war is declared, the Rules of War apply and the Law of Peace is suspended.

Once war is declared, all the rules for civil aviation in the belligerent countries are suspended and probably the control becomes totally military in nature so that for this series of articles it is not necessary to go into the law of War. Nevertheless, it is interesting to reflect on the other aspects short of war for they too disrupt civil aviation. Civil controllers in many parts of the world have had to adapt their controlling skills to take account of such circumstances. It is not easy to do so but in most cases they do adapt to circumstances be it in Europe to clear through excessive military movements during the Berlin airlift; be it in Vietnam where civil overflights carried on through the conflict; be it in Israel where 90 per cent of the airspace is in constant readiness for military action and civil flights have to be integrated; be it in Cyprus where the controllers are providing what service they can to en-route traffic without the possibility of having navigation aids serviced and without precise knowledge of Turkish military movements. IFATCA's Standing Committee VII has recently drawn up a protest to the United Nations of behalf of the Federation on this question.

It is therefore in the controller's interest that IFATCA and its member associations use what influence we have to encourage governments everywhere to cease resorting to violence of any sort whenever things do not appear to go right for them and to resort rather to discussion and arbitration which our Federation has used so successfully in our short existence to resolve disagreements between members and their Governments. If Governments cannot refrain from international violence themselves, how can they as the lawmakers hope to control international crime?

A State when it commits a breach of law, usually should pay restitution. Some breaches because of their gravity, ruthlessness and contempt for human=Hfe now put liability on the individual who actually carried out the act. Such criminals are unable to claim protection from their own State and may be captured and tried by the law of any State. Two crimes fall into this category: piracy and war crimes. Just as we have not gone into the detail of war, for the purposes of this article we may leave the latter aside except to mention that the United Nations have now recognised also in this category Crimes against Peace and Crimes against Humanity and the Genocide Convention 1948 makes Genocide a crime in this category. Israel tried Adolf Eichmann under these rules, having received no protest from Argentina for an unlawful arrest in the Argentine.

Although we have yet to deal with the principle of Freedom of the Seas, we can at this stage discuss piracy jure gentium and its kindred subject hi-jacking. Under an extremely old rule of maritime law, pirates are criminals under the law of nations. They are hostes humani generis (enemies of the human race) who may be arrested on the high seas by the warships of any State and brought into port for trial together with their ship. The right to arrest foreign vessels on the high seas is limited to acts which are piracy 28

jure gentium. This consists of unauthorised acts of violence against persons or goods committed on the high seas either by a private vessel against another vessel or by crew or passengers against their own ship except that the attack must be the conversion of ship or goods in the case of mutineers. Murder of the captain from hatred may not be piracy. Any unauthorised act of violence whether direct, or intimidation or attempt is sufficient to qualify as piracy.

Putting to sea on a marauding expedition without any target or any violence committed can be piracy. (United States v Ambrose Light 1885). In 1934, the Privy Council, the final Court of Appeal in the British Commonwealth, in the case In re Piracy Jure Gentium endorsed the view that any ship not commissioned by a lawful authority which engages in acts of war is a pirate. These views were rejected in the 1958 Geneva Convention where piracy is defined as "any illegal acts of violence, detention or any act of depredation committed for private ends by the crew or the passengers of a private ship or aircraft and directed on the high seas (and for aircraft we should add "over the high seas") or in a place outside the jurisdiction of any State, against another ship or aircraft, or against persons or property on board such ship or aircraft". This definition excludes from piracy jure gentium both acts solely inspired by political motives and acts committed on board a ship or aircraft by crew or passengers and directed against the ship or aircraft itself or persons or property on board.

In fact, as far as piracy jure gentium is concerned, the Geneva Convention is applicable to the very rare cases of pirate ships now to all intents and purposes limited to the China Seas. Piracy is rare because the great maritime powers of the 16th, 17th and 18th centuries carried out a ruthless search for pirates by using their navies even when these States were at war with each other. Ridding the seas of pirates was the achievement of the navies of Spain, Portugal, Denmark, England (later Great Britain), France, Venice, Sweden and the Netherlands. After independence, the United States Navy also tackled pirates. Navies and judiciary alike soon discovered that to hold a pirate for trial meant risking attack by other pirates with loss of innocent lives particularly in the ports of the Caribbean.

Pirates were therefore finally wiped out by summary justice by the navies themselves in many cases, when pirates were hanged from their own yardarms.

It will be noticed that no hi-jacker can come under the definition of pirate jure gentium so that the Geneva Convention 1958 is of no use in this context. Many organisations like our own have pleaded to make hi-jacking equal to the crime of piracy jure gentium, so far without success.

The States have been slow even to ratify the Tokyo, Hague and Montreal Conventions and the Conference of 1973 in Rome met with little success. Frequently IFATCA has urged States to ratify the three Conventions mentioned above but hi-jacking still goes on and with it the taking of hostages to obtain release from prison of convicted hijackers and the economic cost and inconvenience of personal search of passengers more or less well done at airports throughout the world. We in IFATCA must seek to have hi-jacking placed well and truly in the context of piracy jure gentium and to encourage States to take firm steps to eradicate this scourge on air safety. We must also do everything we can to discourage States from treating these "international criminals" as heroes.

At the same time however we must consider the root causes of hi-jacking which until now the States have been

loath to do. The first case is the hi-jack for private gain.

This is carried out either by a madman or a thief who should be dealt with as a pirate and locked away in prison for a long term. Usually he is a lone operator and is not likely to have any organisation which will hold hostages pending his release.

The second case is political and falls into three subcategories. There is the dissident in the United States who hi-jacks an aircraft to Cuba. The United States and Cuba have now signed an agreement on this subject and in most cases the hi-jacker can be arrested if he leaves Cuba and Cuba has now made conditions for hi-jackers there not particularly pleasant. Similarly Japanese hi-jacks to States such as North Korea have become rare because conditions on arrival are not pleasant. The USSR, Ethiopia and Sudan appear for the same reasons to have been abandoned as possible refuges for hi-jackers. This leaves the main case of the Japanese supporting the Palestinian case and the Palestinians themselves. This group comprises the vast majority of hi-jackers today. It is safe to say that the Japanese who support the Palestinian case would probably find some other cause to hi-jack for, if the Palestine problem could be resolved but should that problem be resolved we would probably see a vast decrease in hi-jack attempts by the Palestinians themselves. So while considering measures to be taken against hi-jackers, the States must start looking at the root cause of many hi-jacks, Palestine.

It is not the purpose of these articles to fight political causes but to look at the legal aspects. From a legal point of view, the Palestinian problem is a disgrace. The information on this problem is taken from a report by Sir William Dale, formerly General Counsel to UNRWA (United Nations Relief and Works Agency). UNRWA will be mentioned again when we look at International Organisations in a future article. UNRWA was established in 1949 by a resolution of the UN General Assembly with 48 votes for, none against, and 6 abstentions. It was sponsored by the United Kingdom, U.S.A. France and Turkey. All the Arab States then members of UNO and Israel voted for it. It was given two duties. The first was to carry out with Governments in the region the direct relief and works programme for the Palestinian refugees and the second was to consult interested Near East Governments about measures to be taken against the day when international assistance for relief and works programmes would no longer be available.

Resolutions of the UNO continued the work from year to year. Self-determination was never in the minds of those dealing with Palestinians. In 1948, the UN General Assembly had gone so far as to resolve that refugees wishing to return to their homes and live in peace with their neighbours should be permitted to do so at the earliest practicable date and that compensation should be paid for the property of those choosing not to return and for loss and damage to property. Attempts were made at development schemes towards resettlement. Agreements were made with Syria and Egypt to apply $ 30 million each to technical training and education. Agreements were made with Libya and the Tenessee Valley Authority to help with a Jordan Valley project. These schemes fell through and even if successful would have given employment only to 200,000 persons. But there were over a million refugees.

The Arab States chose to embarrass Israel by retaining these large numbers of refugees near the frontier and with 90 per cent of the aid coming from non-Arab sources.

Israel claimed to have paid compensation but if such were paid it was to landowners and not to the tenants who had lost their land and livelihood.

The greatest drawback to a solution was the possibility of repatriation and compensation. Other drawbacks were lack of resources, the longing to return home, the reluctance of the Governments concerned bearing in mind their own populations to do anything and the reluctance of Governments outside the area to recognise that a problem existed. During a short period only Jordan recognised her duties. But she finally expelled many Palestinians when terrorism became the method of telling the World of the plight of the Palestinians. Many more refugees were forced to go to Egypt when Israeli forces destroyed UNWRA camps in Gaza and Sinai in the wars which succeeded 1948.

1948! That is more than 25 years in which few people listened to the plea of the Palestinians. Eventually they resorted to violence including hi-jacking to show their case to the World at large and on each occasion the world condemned them.

The Universal Declaration of Human Rights should also cover Palestinians. In general the refugees receive the protection of the countries in which they live. But article 15 declares that everyone has a right to nationality. The League of Nations Mandate required the United Kingdom to enact a nationality law. This resulted in the Palestine Citizenship Order 1925 which was applicable to all persons domiciled in Palestine. They were never British although afforded protection by the United Kingdom abroad. When Palestine disappeared, Palestinian citizenship became meaningless. Jordan conferred Jordanian citizenship on all except Jews habitually resident in Jordan as it was in 1948.

Jordan was the only State to do so. Syria gave certain rights but no nationality. Lebanon gave no rights except on death to treat the estate of a Palestinian under the Palestinian Succession Ordinance 1923. Arab Governments grant a travel document under a decision of the Arab League which describes refugees as being Palestinian but such documents are not easily obtainable. Refugees remain Stateless in Syria and Lebanon. Those in Gaza are in the same category. "Everyone has a right to leave any country, including his own, and return to his country", which implies the right to have a country. Until this right is realised plus the right to education, a standard of living adequate to health and well-being, including food, clothing, housing and medical care, UNRWA and several charitable organisations are alone in trying to honour the Declaration of Human Rights. Israel has done much for those who elected to accept the State of Israel, but in many cases facilities are provided only in areas which suit the political situation.

This is not a Middle East problem. It is a World problem which the States must try urgently to resolve. If successful they may well eliminate many hi-jacks, not by the negative measures used against pirates jure gentium but by the positive measures of restoring human dignity to a nation which has suffered enormously over nearly two generations.

In the next article we shall return to the seven principles of International Law to discuss the Freedom of the Seas, the principle on which much of Aviation Law is based.

(For further study: - International Law Chapters 6 & 7 Chambers Sweet & Maxwell; The Law of Nations Chapter VIII Brierly O.U.P.; International Law Volume 2 Disputes War and Neutrality Oppenheim Longmans; UNWRA A subsidiary Organ of the United Nations Sir William Dale; International and Comparative Law Quarterly Volume 23 Part 3; United Nations Charter.)

29

Accident Investigation Report DC 9 Crash - Boston, Mass.

On 31 July, 1973, a Delta Airways DC9-31 crashed while on an ILS approach to runway 4R on the Logan International Airport, in Boston, Mass., U.S.A. Following are some excerpts from the findings of the National Transportation Safety Board Accident Report which relate to Air Traffic Control, as well as some comments.

The Special Weather Report immediately after the crash indicates: partial obscuration, estimated overcast 400 Ft., vis. 1 mile, tower vis. ½ mile, fog, wind 130 ° at 4 knots, fog obscuring 4/10 of sky, RVR 4R 1400 ft. variable to 6000 ft. (RVR on sequence was a ten-minute mean value).

The TWR RVR reading immediately prior to the accident indicated 6000 plus; the TWR controller so advised the pilot but also advised that a fog bank was moving into the approach end of 4 R. The DC9 was on radar vectors for a straight-in ILS approach to 4R. Quotes from the Board's conclusions and comments: "4. The flight was vectored to the localizer course with an excessive approach course interception angle."

FAA regulations require vectors to intercept at a maximum of 30 ° at least 3 NM back from the Outer Marker.

The DC9 was vectored to intercept at 45 °, 2.2 NM from the OM. No distance to the OM (another requirement) was given to the pilot.

"5. The approach controller's attention was diverted by an air traffic control problem involving two other flights, which resulted in a delay in the issuance of approach clearance and other required approach information and in a late release of the flight to the tower controller."

The flight had a clearance to intercept the localizer and fly inbound. However, the pilot had to ask for the approach clearance, which was then issued immediately. From the ,time that the crew first intended to leave the last assigned ·altitude to the time they acknowledged the approach :clearance, 12 seconds elapsed. However, the flight profile )ndicates that descent had been commenced already 12 seconds before the acknowledgement. This delay would ,thus appear to be inconsequential. The aircraft was above .the glide slope when it started its descent and also when ·it passed the OM. The approach controller had issued the landing clearance to the flight and transfer of control and frequency _change occurred approximately 2.5 NM from the touchdown point. The tower controller then issued landing clearance •ag(lin as well as traffic info, the RVR reading and the fog .info. -This information, "received by the captain at a very critical phase of the approach, added to the distraction already existing in the cockpit." The controller had no way of knowjng that a problem existed in the cockpit.

• "7. The RVR given to the flight was not indicative of c ,. ,the actual visibility on the approach to runway 4." .Jr:ifact, the RVR reading can never be considered indicative of the visibility on approach to the RVR runway or .even th_evisibility on that runway. Many pilots and controllers,. how.ever, are not aware of this fact and it bears rerstating. 'In most cases, the transmissometer equipment is 'displaced from the runway it serves. In Boston the location "r, ' ')I! • • is approximately abreast of the ILS touch-down point, on -

30

a 250-foot baseline, and about 500 ft. to the left of runway 4R. The RVR value may thus be misrepresentative because fog covering the runway might not be covering the equipment or vice versa. The 51.1 second cycling time of the RVR digital display can further complicate the problem.

With rapidly changing visual conditions over the runway, considerable disparity can exist between actual conditions and the values presented by the digital displays and reported to the flightcrews. Further, RVR was never intended to represent the distance the pilot expects to be able to see from the outer marker, middle marker, decision height. or over the runway threshold. Before the RVR can be representative, the aircraft must be near the touch-down point on the runway. " ... the RVR value is a sampling of a small segment of the atmosphere, usually near the touch-down point. It should also be emphasized that RVR value does not necessarily represent actual runway visibility conditions near the touch-down point and includes a significant time delay before reaching the crew."

The above quotes are especially interesting in the light of the fact that the RVR readings in part determine the decision height on CAT II ILS approaches.

"16. The air traffic controllers in Boston tower mistakenly assumed that Flight 723 had landed safely."

The heavy fog covering portions of the airport at the time of the accident restricted visibility and precluded visual observation of the accident from the tower cab.

A lack of communication existed between the ground controller and the tower controller concerning the sequence of incoming flights. Delta 623, a preceding arrival, was taxiing toward the ramp when Delta 723 crashed. The similarity between flight numbers caused confusion because controllers believed that the flight taxiing toward the ramp was Flight 723. Accordingly, airport operations continued without interruption. The FAA has now nationally changed their procedures to require pertinent information be forwarded to the ground controller on arrival aircraft when the active runway cannot be observed visually from the tower cab.

"17. The ALS (Approach Light System) warning system in Boston tower was ignored by air traffic control personnel because of previous false alarms and misunderstanding of the operation of the system."

Two approach light bars were destroyed by Flight 723, when it crashed, activating the ALS alarm. This ALS alarm system had a history of frequent false alarms caused by water in the power line. Thus, when the "real" alarm occurred, controllers silenced the buzzer and ignored the red lights. Reminds one of the numerous false "special code" alarms we're getting in some of our facilities.

In summary, while the Board did not specifically include any of the above in the "Probable Cause" portion of the report, it appears clear that they were not satisfied with some aspects of the service provided and procedures used. Here is the last sentence of the "Probable Cause" portion: "The poor positioning of the flight for the approach was in part the result of nonstandard air traffic control service." We'll leave it to the readers to draw their own conclusions about the possible consequences of using nonstandard procedures.

(CATCA Newsletter)

Aeronautical Satellites: Luxury Gadgets or The System of The Future?

by Jacques Villiers, lngenieur General de !'Aviation Civile (France)

Foreword by the Editor Those of us who rely on noisy and at times unreliable HF communication channels to affect separation between aircraft on long-distance flights, look out longingly for relief and much needed improvement which the introduction of an aeronautical satellites system would bring. But, as in other aspects of the controller environment, here also forces are at work who do not see the need for improvement in the same light as we do, and who look upon aeronautical satellites as luxury items which the world can ill afford.

To us and to those others who have for some years been hoping for a global agreement to develop aeronautical satellites, the news that such an agreement had been signed at last must seem too good to be true. The possibilities of an aerosat network have been under consideration since 1966, when ICAO decided that the oceanic traffic growth-rate dictated establishment of such a system before the end of the 1970s. ICAO stipulated a pre-operational network scheduled so that a fully operational service could be in use by the early 1980s, and requested a minimum of six voice channels in the satellite, although the proportion of automatic data transmission is likely to increase at a later stage. The most contentious point was the choice of UHF L-band frequencies instead of VHF, for which airlines are at present equipped. The argument was that UHF offers greater reliability as well as providing more bandspace compared with the already crowded VHF wavebands.

The decision in favour of L-band in 1971 resulted in the International Air Transport Association, which represents the airlines at the industrial level, threatening legal action against the imposition of any user charges "for a system which the airlines have not raised and do not, at this time, need." IATA considered that the use of UHF instead of VHF would double the programme costs and this would eventually find its way into user charges. A total cost of $ 600 million over 12 years is anticipated by the airlines for the fully operational system. This would include the on-board UHF installation - estimated at $ 100,000 per aircraft as opposed to $ 35,000 for VHF. The UHF system would require each aircraft to carry more powerful receivers and a small, steerable, dish antenna.

Following the ICAO L-band decision, IATA technical director Dr. R. Shaw said at the time that airline opinion had been more or less totally disregarded and added that it "may or may not have a better system. They (ICAO) claim it will be better in performance. We have doubts on that.

The VHF system we visualised could have provided a very useful communications capability for a total of about $ 75 million, half our estimate for UHF. We could have afforded to pay for that service even though it would have been a fairly expensive step to take."

However, the difficulties have been ironed out, and it

is expected that the location of the Aerosat Co-ordination Office will be in France as a central location, bearing in mind that the United Kingdom, as one of the European member countries, may well be the location of the main ground terminals through which the experimental Air Traffic Control signals will be transmitted and received. The Space Procurement Office seems likely to be located in the Washington/New York area, and so the two main continents will share the responsibility of hosting the major organisation of the new administration. Canada will also participate.

The latest Memorandum calls for the first flight model to be launched at the end of 1977, although with the delays incurred so far, this could well slide into early 1978. The second launch is scheduled for the end of 1978.

The implications of the agreement are extensive. The Aerosat programme is of immense importance both for its ultimate use and for the fact that in the first phase the development programme is being shared approximately equally between North America and Europe. The European satellite community has waited a long time for the opportunity to join its American counterpart on equal terms in such a big programme, and so it is very important that Aerosat should now proceed to a successful conclusion.

One of those who has advocated strongly the introduction of an aeronautical satellites system is Mr. Jacques Villiers. In the article which follows, Mr. Villiers puts the case for its introduction in an indisputable way and refutes the charge that the cost of the system is prohibitive and unrealistic. Air Traffic Controllers can but hope that this improvement which will be so beneficial to many of us, will materialise sooner rather than later.

The ESRO/CANADIAN/U.S. Aerosat Aeronautical Satellite Programme Readers of this journal will probably be familiar not only with the services offered to civil aviation by a sate IIite system (such as voice and coded communications and determining of aircraft positions), but also with the techniques involved in such a system.

The nations responsible for air navigation have become increasingly aware of these possibilities, and as a result of investigations by its working-group of experts (ASTRA), the International Civil Aviation Organisation (ICAO) has recommended its Member-States to proceed with 'actualsize' experiments with a view to preparing an operational phase envisaged for the early 1980s.

Owing to the world-wide nature of such an undertaking, the various nations have acknowledged the advantages to be gained from a pooling of both financial resources and effort, in conducting these experiments. After various initial difficulties, the United States, Europe and Canada tabled an agreement on aeronautical satellite experiments known 31

as the Aerosat Programme, to be conducted in an area centred over the Atlantic and covering Africa and part of South America.

Signing of the agreement was, however, ~elayed due to the vigorous opposition on the part of the American Air Transport Association, on the grounds that the Aerosat Programme is too ambitious. The Association also has a long-standing preference for the VHF band for the groundto-air liaison instead of the UHF L-Band chosen for the Aerosat experiment on I.C.A.O.'s recommendation.

In fact, this apparently technical controversy conceals a fundamental difference of opinion on the needs and uses of the future operational system, and, on a more general scale, on its economic effectiveness. Some airline companies would prefer a system which could be temporary or provisional, with a ceiling on costs and set limitations on capacity and performance, centred on one or two ground stations. The aim of I.C.A.O. and its MemberStates, however, is the preparation - under the best possible conditions - of a future system on a global basis.

The in-depth economic study for the Dioscures project showed the considerable potential benefits of such a system, but since these initial studies, several new elements have emerged, causing some doubt to be cast on the economic rentability of aeronautical satellites.

Without going into the details of either current or previous economic studies, is does seem worthwhile to take a general over-all look at the question of whether aeronautical satellites are luxury gadgets meant merely as 'fodder' for space technology, or whether they are in fact destined to become the basis of a future global system.

This is where the fundamental debate originates.

The main economic advantages which emerged so clearly from the Dioscures study, were based on operation over the North Atlantic. However, the study was completed in 1969 and since then, several fundamental factors have developed in such a way as to decrease considerably the system's anticipated 'returns' such as: delay in the date when Concorde goes into service; the shelving (at least provisionally) of the American SST; a levelling-off in Transatlantic traffic growth; success in the implementation of•inertial navigation systems.

Since this period, the efforts of the various nations have been concentrated to such an extent on the solution of the political obstacles to the introduction of a new system requiring international co-operation in space research, and the drawing up of technical specifications, that studies of both long and short-term economic problems have not always received the attention that they deserved. This has proved detrimental to the choice made on some options, determined on a basis that was more technological in nature than economic. In view of this situation, the French National Centre for Space Research (C.N.E.S.) and the French Civil Aviation Secretariat General (S.G.A.C.), decided to update their initial economic study and this task was taken in hand.

The general feeling of unease also affected the aeronautical authorities in the United Kingdom, and their investigations (whose actual content has not been divulged) led them to declare that aeronautical satellites are of little, if any interest to Civil Aviation at least until the end of the 1980s. It is worth pointing out here though, that their assessment only concerns the North Atlantic and apparently 32

these same authorities have not yet investigated the problem from the global stand-point, that is, the merits of a world-wide system.

But studies by the United States' aeronautical authorities have shown that the cost of a satellite system would not be any greater than that of the HF communication system in use at present.

Up to now, the aim of most economic studies was to try and assess 'operational needs' in order to evaluate the cost of the system, and calculate each possible fundamental economic advantage area by area, such as a reduction in aircraft separation standards and spacing or inflight time, earlier announcement of E.T.A.s, and improved communications in Air Traffic Control or in company communications (O.P.S.).

Whilst waiting for the results of the new C.N.E.S./ S.G.A.C. study, or other similar studies being undertaken elsewhere, it seems reasonable to try a summary approach to the problems involved, in trying to answer our initial question.

Let us suppose, for example, that a global system was set up in the early 1980s consisting of 5 satellites (2 in orbit over the Atlantic/Africa/South America region, 2 in orbit over the Pacific and one over the Indian Ocean). Let us also assume that at that time, all long-distance aircraft - that is, about 1,000 - are suitably equipped to use the system. The total cost of the system per hour of flying time for each aircraft could be calculated as follows: Purchase, installation and maintenance of airborne equipment over a 10-year period: about $ 100,000, that is about $ 10,000 annually per aircraft; Number of hours flying time per day per aircraft: about 9 hours, that is slightly more than 3,000 hours annually; Proportion of flying time over the airspace in question, that is to say, the sparsely populated continents and the oceans, or, in other words, the whole world except North America and Europe, is equal to at least twothirds of the total, that is: 2,000 hours per year; Airborne equipment's overall operating costs per hour of use:$ 5.-; Up-keep, by replacement or renewal of the space sector: 1 satellite per year, that is 15 million dollars, which is equal to $ 7,5 per hour of use per aircraft.

Therefore: The total cost of the airborne equipment together with the cost of the space sector will be about $ 12,5 per hour of flying time for a long-distance aircraft.

Should it be decided to redeem the out-lay on the initial space sector (satellites, etc.) at the rate, say, of 1o 0/o per year, then the equivalent of 0.5 satellites per year would have to be added to the calculation; in other words: a further $ 2,5 per hour of flying time. The relatively low cost of the system is immediately obvious, despite the particularly conservative estimates which have been accepted up to the present.

Before going on to list the resulting advantages, it is worth comparing the system's operating costs with other running costs involved in the operation of an aircraft: Marginal cost of one hour's flying time: $ 3,000; in other words: $ 50 per minute; Wage bill for technical aircrew: about $ 100 per hour of flying time; Cost of 'en-route' ATS Service in Europa for the aircraft concerned: $ 200 per hour of flying time (at the

present time only 15 % of the cost is actually charged to the user, increasing by increments to 100 %) ; Cost of the purely consultative Flight Information Service provided by the 'Agence pour la Securite de la Navigation Aerienne' (ASECNA) in African membercountries and in Madagascar: equivalent to about$ 160 per hour of flying time, of which 33 % is actually charged at present.

Obviously, the last figure is the most interesting, as it illustrates that: Over Africa, for example, and apart from any additional profits gained, the implementation of a service by aeronautical satellite would increase costs by as little as 8 %.

This alone should surely convince even the most hardened critics.

Before continuing the analysis, one or two other remarks can be made here: - The Flight Information Service offered at present, in accordance with the recommendations of the ICAO regional conferences, are not subjected to any analysis on the basis of 'economic rentability' and, indeed, it is difficult to imagine the mechanics of such an analysis, due to the virtual impossibility of assessing the basic 'profits' afforded by such a service.

- The actual quality of the present Flight Information Service can only be termed as mediocre, due to exclusive use of HF wavelengths in areas with high densities of radio-electric noise. Anyone who has operated an HF liaison, either successfully or unsuccessfully in Africa or South America knows just what this entails!

- There are numerous areas all over the world where, due to a lack of facilities, it is impossible to offer a service such as that offered by the ASECNA, and this is of course detrimental to both the flow and the safety of air traffic in those regions.

At this point, therefore, it is possible to answer at least part of the initial question by confirming that a global system of aeronautical satellites is not a 'luxury gadget' since the marginal increase in Air Traffic Control operating costs, as well as those for O.P.S., is minimal. Such a system cannot, therefore, be reasonably accused of having been designed merely to "satisfy commercial and political appetites by acting as a consumer of technology."

Is it, however, a useful gadget?

As there is not a lot of justification for having the present mediocre Flight Information Service when considering criteria purely based on economic studies, then this is all the more reason that the position should be improved if this can be done. We have seen that the existing service is useful, but costly and imperfect, and even distinctly lacking in value during marked periods of some flights.

This finding alone would justify the revolution in the present system, both in quality and quantity, that could be achieved for a minimal increase in marginal cost. This would then be followed by a progressive decrease in the net cost of the present service as it is gradually scaled down to make way for the new, improved system. Approaching the problem from this angle, one would surely be justified in anticipating further advantages to be gained from the use of aeronautical satellites, such as, for example: Uninterrupted access to, and availability of, a reliable ground-to-air link. In Air Traffic Control systems, and undoubtedly in O.P.S. too, this is a considerable ad-

vantage in itself, which is impossible to evaluate since it is not in relation to the number of communications exchanged. On the contrary, with a guarantee of permanent and immediate access, it is silence that we are prepared to pay for!

Time-saving, and thus a reduction in crew flight-fatigue, resulting in greater safety both 'en-route' and in the landing phase.

Greater knowledge of meteorological conditions both in flight and at destination, enabling a reduction in flight time, avoidance of unscheduled landings, the taking of re-routeing decisions at the optimum moment, passenger comfort, etc. As Air Traffic Controllers on the ground will have improved methods of determining aircraft positions, this will enable them to follow more direct and varied tracks at optimum levels and in complete safety. And finally, better control of airborne navigation.

It is worth noting that the cost of the aeronautical satellite service would be totally defrayed by a potential 0.4 0/o average saving in flight-time Improved company communications for better organisation at en-route stops and thus improved passenger service and better aircraft maintenance (engines and equipment).

Availability of special safety liaisons in the event of technical difficulties, hi-jacking or even incidents concerning passengers' health. Note, for example, that the future annual traffic forecasts envisage as much as a billion passenger-hours which, on long flights, would be spent with no access to medical advice and treatment.

There is reason to believe, therefore, that the introduction of reliable, high-quality communications into a system that has never been well-endowed in this respect, will give rise to a whole set of new and useful applications that are, as yet, difficult to envisage. This has always been the case in the field of communications, whose needs and economic rentability (difficult to estimate in concrete values) grow rapidly when the possibility exists of efficiently fulfilling these needs.

There are also numerous advantages to be gained from the system's application to maritime use, but we shall not go into that aspect here. Until the publication of a more in-depth financial ar.iatysis, or better still, a 'true-scale' experiment, it is safe to say that a satellite system would render valuable service to Civil Aviation, and that after a period of initial hesitation, the companies would rapidly equip their aircraft not only on their own initiative, but to an extent far beyond the tentative forecast put forward in this paper.

The question is therefore whether the satellites envisaged for the Aerosat programme - and their corresponding costs - would, in fact. meet the needs anticipated.

First of all, it should be pointed out that the automatic fixing function (determining of aircraft positions) - attacked so vigorously and incomprehensibly by certain companies - will provide Air Traffic Controllers with a fix on all aircraft within the system's cover, at any given moment and at suitable rate. The equivalent of only one voice channel will be allotted to this throughout the satellite's cover, at a minimal marginal cost.

The other speech channels could be used for nonsystematic transmissions (voice or data). Assuming that at any given moment, out of the 1,000 aircraft mentioned ear33

lier, a maximum of 250 will appear within the area covered by two satellites, it will be seen that with a 'use/actor' of 0.5, the Aerosat satellites could allot one minute's conversation per peak hour to each aircraft. This shows that the cost of the space sector that we used coincides with the other hypothesis.

There is reason to believe, also, that the number of aircraft in a subsequent generation that are equipped to use the system will increase, and that actual operational experience will eventually suggest various profitable applications that will, in their turn, become indispensable.

Satellites with a greater capacity will then have to be envisaged to meet the heavy, economically viable demands.

However, one would still have the right, logically, to query the fact that the Aerosat experimental system is designed with a capacity that could meet the potential needs of an initial operational generation.

In fact, bearing in mind the experiment's main aim (the study of access problems and technical and operational conditions). Aerosat's initial capacity is not only fully justified, but is an essential condition in achieving it. The experiment can only be deemed an unqualified success if, as a result of its findings, future standards and specifications for a subsequent fully operational system can be put before the I.CAO. As far as possible, the idea of a second generation experimental system should be avoided, particularly bearing in mind the cost involved.

Thus, it can safely be said that the Aerosat project is a sound one, both from the technical, operational and economic point of view and that everything should be done to implement it as soon as possible, especially bearing in mind that a period of 5 to 10 years must be allowed between a decision to proceed with the experiment (now

taken - Ed.) and the introduction of a fully operational service.

The fact that the existing HF communications system cannot yet be termed defective, does not mean that ideas concerning its eventual replacement on the grounds of the cosVelficiency ratio, should be ignored. Nobody would deny that often, a 15-year old car may still have many miles service left in it, but any one with some grasp of economics knows that some thought must be given to its replacement, especially if you know that you have to wait ten years for the delivery of a new onel An entirely new dimension will be added to the whole concept of a global system by satellites which will provide direct, high-quality and reliable liaisons between any point on earth and any long-distance aircraft flight, regardless of its position. It is in fact difficult to imagine all the possible consequences at the present time. What can be said, however, without entering into details, is that the consequences will be of a major order and will call for the solution of political, economic and organisational problems.

We would be wise to anticipate such a task by using the experience and results which will be gained by Aerosat, which is an experimental programme, in a semi-operational context.

This over-all analysis has also revealed that options concerning the nature and distribution of the groundstations will have a lasting impact both on the future and on the success of the system and further studies on the subject will soon be called for. The international aeronautical community will be faced with all kinds of problems and options in putting the system into operation and it would be wise to investigate them.

(Translated from the French by Angela Bessis, B. A., first Honorary Member of the Eurocontrol Guild of Air Traffic Services. This paper was first published in "Navigation" No. 84)

New Elements: New Responsibilities

by C. Martin Coddington, ATC Team Supervisor, Minneapolis International Airport

One of the newest components of the ATC environment in the U.S. is the ARTS Ill tracking system now operational in many radar equipped Approach Controls. This is a computerized system integrated into the standard radar.

It is truly an amazing device to see and use, but like anything else, when a new element is introduced, new responsibilities accompany it.

One problem is especially baffling. In this day and age of technology, when the ARTS tells you an aircraft's altitude within 50 feet, its ground speed within 5 knots, and constantly scans for hijackings, radio failures, and emergencies. we can't get pilots on the right transponder code!

Controllers don't always speak too clearly, and when they do, they can still misread these important numbers. Pilots, being of the same human design, may not hear the words exactly as they are spoken or may transpose them while reaching for the knobs. Even then, there is the problem of small numbers to be identified in the dimly lit confines of the flight deck. Regardless of who said or did what, if the

34

transponder replies with the wrong code, there is a good possibility that some one else's flight plan will be stolen and sometimes lost from the computer. In the Chicago Common IFR Room alone, we lose dozens of flight plans a day from this phenomenon. Portions of the flight plan can be saved if everything works right, but other portions are lost forever. I find it strange and frustrating that such sophistication can be reduced to the level of misunderstanding.

The problem I just mentioned relates to a responsibility the controller has acquired, that of starting and maintaining tracks in the computer for each of his aircraft. These aircraft must be tracked so that any controller can identify all controlled traffic within the system. This reduces a lot of coordination and allows some flexibility in what might be a rigid sectorization of airspace. Aircraft that cannot be tracked, whether because their transponder is acting up or they don't have one, must be coordinated, each on an individual basis. Then there is Mode C altitude readout.

The altitude of each airplane must be verified to insure that its Mode C is within tolerance. The FAA has decided that 299 feet is maximum error allowable before the crew must be instructed to turn the equipment off. The verification of these Mode C altitudes, again, reduces coordination and provides flexibility in the sectorization of the airspace.

299 feet seems to be an adequate standard, as Mode C readouts are generally very accurate.

Most readouts are right on. Those that are not are either within 200 feet or the error is so gross it is obviously wrong. Readouts that have been verified as correct sometimes go astray for brief periods but usually return to a reliable state. When the Mode C is really out of whack, anything is possible. Planes that have just taken off may show 10,000 descending. Planes that may be 8000 descending can show 4000 or 14,000 climbing. And would you believe: we even get erroneous altitude readouts from planes that don't have Mode C! In any case, actual altitude verification and the insurance that tracks are started and maintained have definitely increased the responsibilities of controllers who operate this equipment.

Quite separate from verifying the Mode C readout is the problem of monitoring these indications as the plan progresses throughout the system. This touchy situation has created a great deal of animosity between pilots and controllers, and there doesn't seem to be a cure for the condition. I hope to expose this problem and give you just a taste of the attitudes controllers are developing to cope with it.

We find an alarming number of pilots flying at other than assigned altitudes. If the difference between the indicated altitude and the assigned altitude is less than 300 feet, the controller may elect to overlook it on the basis that this is within tolerance. Simple arithmetic will tell you that two planes could be operating 600 feet apart under these circumstances. And logic would dictate that if the controller saw an unacceptable deviation, he would instruct the pilot to return to his assigned altitude, and the pilot would comply. It doesn't work that way though! Because of pride, I suppose, the majority of the pilots fire back that they are at the assigned altitude. The controller has no choice then but to instruct the pilot to turn off his Mode C as it is out of tolerance, even though it was working fine just a few moments ago. And he'd bet his day's wages that it still is. After this bitter experience, the controller tries a softer approach. When he sees significant deviation, he asks the pilot what his altitude is. About half answer truthfully, and the other half reply with their assigned altitude. This latter group is out of tolerance and must turn off the equipment. However, this fails to cut the controller's frustration in half. It occurs to him about this time that more and more of the aircraft that he knows to be equipped don't have their Mode C turned on. This seems to be a reaction from pilots at being caught. During discussions with pilot friends, he hears stories of how their captains have instructed them not to operate this equipment or not to operate it unless requested. One first officer swore his wrist had been broken when his captain demonstrated his karate technique simultaneously with an ATC request to turn on the Mode C. The controller now launches a campaign to instruct all aircraft that are known to be Mode C equipped, and those that probably have it, to turn it on. This has excellent results until one day he runs into a 727 pilot that flat out

refuses. The controller, who feels he is on firm ground, ascertains that: Yes, the plane is equipped; no, it has not been found out of tolerance or inoperative: yes, the pilot knows it's supposed to be on; and no, he will not turn it on. Not wanting to be outdone by this birdman, the controller refers the matter to a person of higher authority.

The person of higher a~thority questions the ancestry of this pilot, but because of other pressing matters in the realm of management, he does not follow up the incident.

Oh, well, Win some; lose some.

Meanwhile, after many months of pondering the dilemma of altitude deviations, the controller decides he will disregard all altitude readouts unless they are needed.

He decides that he will use the Mode C on initial contact, for the tolerance check, to insure important crossing restrictions, to prevent a pilot from climbing or descending out of his sector, to insure proper turn-on and descent procedures during parallel ILS approaches and to confirm in his mind that two of his planes that are converging on one another will indeed have a least a thousand feet. By the way, the latter case gets quite "amusing" when he sees two planes that have a thousand feet on his paper flight progress strip but only 200 or 300 on Mode C. Through experience he has determined that the best way to handle this situation is to issue traffic, including altitude, to the offender and then watch the Mode C rapidly correlate itself with the flight progress strip. When correlation fails to commence, he will follow up in some other manner.

Anyway, the controller decides that he will not use his Mode C readouts to remind pilots of their assigned altitudes when there is no other traffic and he will not use it to enforce noise abatement. For to do these he must suffer the wrath of a pilot who feels he is overcontrolled and is quick to tie up the frequency with an irate discussion of the matter. Secondary to this, he feels that he is not required to use the Mode C for these purposes and that his supervisor, while sympathetic to the situation, is reluctant to receive the captain's over-modulated phone call after landing, which ends with the statement that it would probably be best for all concerned if the controller could temper his judiciousness. After all, everyone makes mistakes! The controller weighs this advice with his conscience and prays that none of his flock make mistakes of the fatal variety. Those can spoil your whole day.

I do not wish to condemn pilots but aim to try to give a better understanding of controller's responsibilities than has existed previously. Nor do I condemn those charged with the management of the air traffic system but merely seek answers to just a few of the many questions controllers have about their responsibilities.

What is a Pilot?

A pilot is an individual of immeasurable superiority to his fellow creatures in the street, a Master of the Air wherein he flies his underpowered, poorly-instrumented, misaligned and multi-patched aircraft under dubious control in complete contravention of the instruction he has at some time received from his flying instructors and quite contrary to regulations published for his confusion by Government officials, much to the distress and damnation of an ulcerridden group of individuals known as air traffic controllers.

(Airport News, Dorval)

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The Pilot's Point of View

Flow Control (Europear:i Style) Must We Admit Defeat?

If any last, lingering doubt remained of the validity of IFALPA's oftstated convictions, that the practice of ad hoe flow control measures is negative and self-defeating, it was removed at an international pilot/controller forum held near London (Heathrow) Airport last November under the auspices of the London Branch of the U.K. Guild of Air Traffic Control Officers. A number of well-known figures from IFALPA's and IFATCA's European Member Associations were present on that occasion and contributed to a competent and positive representation of views of the unhappy flow control saga.

We heard all the old, familiar stories of the problems of pilots and controllers which inevitably arise as a result of the restrictive nature of flow control; delays, unwanted flight levels, uneconomic operations, flight management and controller co-ordination difficulties, etc., with some embellishments and variations due to local ATC system inadequacies (it was admitted, for instance, that sector controllers responsible for issuing clearances were frequently unaware of "slot" times allocated by flow control regulators). We also heard the equally familiar story of congested scheduling, incompatibility of national ATC facilities (the ATC computer at Frankfurt, for example, cannot "talk" to the ATC computer at Schiphol, Amsterdam); the particular geographical problems of France in relation to the main traffic flows; inaccessibility to civil aircraft of restricted military airspace; and many more besides. What can be done about this highly frustrating and unsatisfactory situation which, in the technological era we live in, is little short of disgraceful?

The basic problem, as everyone admits, is one of insufficient ATS system capacity to meet the traffic demand.

The positive approach, therefore, as .lFALPA maintains in its policy, is to improve the capacity:·Essentially this involves better ways of utilising the available airspace by improved navigation techniques (e.g. area navigation) permitting more routes and lower separation standards to be used, and by improved ATC facilities for the handling of the traffic on an international, instead of a national basis (one pilot expressed this requirement as the ability to get one clearance from Istanbul at his desired flight level direct to the outer marker at London).

It has to be recognised that these are long-term objectives, calling for the expenditure by the States and airlines of a lot of money for the necessary airborne and ground equipment. It also requires a truly internationally co-ordinated effort, including the surrender of many cherished nationalistic attitudes, to achieve an effective multinational ATC system in Europe responsible for air traffic service to all traffic, civil and military. There is little evidence of any significant progress in this direction.

So we are stuck, in the meantime, with the present European ATC environment, with all its manifold shortcomings. But this is no reason to abandon the positive approach to the problem, still less to allow it to stagnate and fester in the quagmire of bureaucracy which seems 36

to be associated with so many contemporary ATC systems.

Firstly, the fundamental question of congested scheduling needs to be sorted out, and quickly, so that multiple aircraft movements are not scheduled at the same time for the same airway routes and at the same flight levels (especially within the same airline, as happens now). Even at local, or national, level something could surely be done about this now (as is the case in the Federal Republic of Germany) pending the establishment of a computer-backed international scheduling organisation.

Secondly, until such time as the European airspace as a whole can be operated by a single executive supranational ATC Agency, flow control should be regulated and applied on a multi-national, or at the very least, on a bilateral basis, by suitable organisations. Unless this is done, the present flow restrictions attributable to inter-Centre co-ordination and communications problems will persisL Thirdly, the current efforts towards joint civil/military control, and the common use of the airspace to agreed separation standards should be intensified. The requirement for civil aircraft to gain access to military airspace when this is not in use, and to co-ordinate military activities in regard to civil air routes, must be tackled now. Fourthly, the maximum flexibility should be injected into the current flow control procedures as a function of improved inter-Centre communications, making maximum use of radar to facilitate hand-overs, and the provision of alternative routeings and flight levels.

Fifthly, wherever it is safe and practical to do so, reduced longitudinal separation (5 minutes/30 n. m. is now authorised under radar surveillance) should be applied, in conjunction with limited speed adjustment compatible with aircraft performance at specified levels (not blanket speed control). And, finally, keep the pilot informed. If he knows the problem, as it affects his aircraft, and he can help to solve it, he will if he can.

(Capt. V. H. King in "IFALPA Bulletin")

Cont. from page 10: 6. Kalsbeek, J. W. H., "Standards of Acceptable Load in ATC Tasks" Ergonomics, Vol. 14, 1971.

7. Leplat, J., and Blsseret, A., •Analyse des Processers du Traltement de !'information chez le Controleur de La Navigation Aerienne", Bulletin d'Etudes et Recherches Psychologlques XIV No. 1-2, 1965. English translation in Controller, Vol. 5, 1966. a. Meister, D., and Mills, R. G., "Development of a Human Performance Reliability Data System", Annals of Reliability and Maintainability, 1967.

9. Older, H. J., et al., Human Factors Aspect of Air Traffic Control, Report No. NASA CR-1957, 1972.

10. Ratcliffee, S., "Mathematical Models for the Prediction of Air Traffic Controller Workload", Controller, Vol. 9, 1970.

11. Rolfe, J. M .. An Evaluation of the Effectiveness of a Secondary Task, Royal Air Force JAM Report, No. 473, 1969. .

12. Rosenshine, M.. "Operations Research In the Solution of Air Traffic Control Problems•, J. of Industrial Engineering, Vol. 19, 1968.

Two Segment Approach

by Capt. Ed Mack MIiier

No Problems Envisaged for ATC General The muffling of landing noise pollution is a tough problem. A landing aircraft, to be slow enough for touchdown, comes in 'under full sail' with full, or nearly full, flaps, resulting in the use of full thrust to overcome the increased drag and keep the plane aloft and controllable. A partial answer is what they call the 'bent' or 'two segment' approach. This new type let-down procedure is now being brought into use at an increasing number of airports across the USA. Primarily, the credit for the new 'high profile-low noise' approaches can be traced to the FAA and NASA. Their aim was to find a solution to all the jet noise complaints and lawsuits registered by irate home owners under the prime approach paths to major city airports.

Development In May 1972, NASA put out a request for a proposal to develop an minimum noise approach to landing. It would go to an airline using Boeing 727's, because there are more 727's operating in the USA than any other type of airliner. A successful bidder, United Airlines, received a S 1.5 mio contract from NASA in the summer of 1972 to develop the aircraft landing procedures aimed at reducing the noise levels over airport communities.

Working with United, Collins Radio Co. is supplying avionic equipment to allow pilots to land at airports by means of a two segment descent that keeps the aircraft higher than is possible under current approach techniques.

According to the official release, the planes, equipped with special guidance, will be able - in all weather conditions to descend at a steeper than normal 6 degrees until they are approximately 1000 feet above the ground a mile and a half from the end of the runway. Then they will transition to the standard 3 degree glideslope for a conventional landing.

Following the 727 development, another contract was let to adapt different avionics to a two segment approach for long-range jets. United won this contract as well, and is furnishing an area-navigation-equipped DC 8 for this development.

Modifying An Existing Technique • The technique was simply to take an existing controlling method, and modify it to make it precise and safe. At most noise-sensitive cities, ATC now brings airliners into the landing stream high and fast, until the last possible moment. The problem for the pilot is that of being too high and too fast when released for approach, especially when on instruments, and where his position knowledge normally comes from the air traffic controller or from DME. On VMC days, of course, he has the ability to check his position with known landmarks. Under the new concept the pilot intercepts a primary steep glideslope and uses it for a quiet, power-off descent to a point where he would nor-

mally intercept the glideslope. At this juncture he is guided onto the normal ILS and finishes the approach as usual.

Heading guidance for both segments is provided by the localiser.

United technicians have modified the SB-50 autopilot so the plane can fly the two segment approach 'coupled'.

Auto-throttles were also installed in the test 727 and in the simulator, although these won't be part of the package on the line 727's converted to the new approach system.

Prime Considerations To get the program started on time, United leased a 727 fresh off the Boeing production line from Ansett and modified it for testing. This was carried out at Stockton, California. During the entire experiment, Routine Airline Operation was kept in the forefront of the evaluation: 'Can this type of approach be solidly effective in reducing noise?' and, 'Will the airline pilot accept it?' Other aspects that have been investigated are: 'How does this new approach fit into normal airline operation?' and, 'What problems will it cause for ATC?' So far, all can be answered optimistically. The two segment approach is a great leap forward in noise suppression; it is easy to fly from the pilot's standpoint; the approach, as mentioned previously, hardly differs from present scheduled air carrier operations - it just gives more positive pilot guidance. Finally, it should only be another welcome aid to ATC. After much investigation and experimentation in both the simulator and the aeroplane, it was decided that a sixdegree upper slope was the best compromise to give noise relief and yet not be too steep. The upper segment glideslope the pilot flies does not require another ground installation; a small computer is merely added in the radio rack of the aircraft. The computer is tied in with the Flight Director system, and is activated by the two segment switch. When this switch is in the 'armed' position, the modifications to the Flight Director and Autopilot are initiated. When the switch is at 'normal', the aircraft functions exactly as it did before, with no change in mode. It is located on the instrument panel in front of the captain, positioned to the left of the Flight Progress Display Annunciator.

The main pilot display difference is in the presentation of the glideslopes. While the aircraft is on the upper and steeper glidepath, guidance is gained from the Flight Director, which looks at the upper slope, seen on the Horizontal Situation Indicator. On United's installations, both this glideslope presentation and the one shown on the side of the Artificial Horizon are the same. In the two segment approach, however, the lower one only shows the steep glidepath, until the transition point when it is automatically switched back to the lower glideslope. Therefore, as the plane descends, the pilot can see his path relative to the upper angle. At the transition point, the Flight Director discards the upper path and takes its commands from the standard glideslope. A green light in the Annunciator System tells if all is 'go'.

37

Transition The transition from one glideslope to another is very easy. The descent rate on the upper slope will be in the order of 1600 fpm. The engine power will be greatly reduced (which of course contributes to the noise abatement desired). As the aircraft approaches the standard glideslope as indicated on the ADI, the pilot is commanded to smoothly bring the nose up as he slows to reference plus 5 kts. (in calm wind conditions), and adds power to slow-fly the aircraft to a landing. Speed in the upper segment will usually be about 135 kts., and on the normal glideslope about 125 knots. Wind shear on the upper slope would be handled exactly the same as on the lower.

If the pilot were somehow to miss the transition, a positive warning is provided to tell him he has passed the glideslope. He would simply level off until the. glideslope came back down to him, being cognisant of obstructions and minimum safe altitudes, of course! The beauty of the system is that it gives a greater margin of safety for noise abatement in bad weather, by giving the pilot positive position information at all times.

The other important addition to the cockpit display is the Airport Elevation Panel. The height of the landing field becomes the system's fixed base, and everything is calculated above it. Barometric altitude, taken from the captain's altimeter, is used, rather than radio altitudes.

In testing the two segment approach, United used the simulator exhaustively to anticipate problems that may have evolved. Every type of mechanical and meteorological snag was incorporated; everything was tried to find weak• nesses, even down to possible mishandling by the pilots.

The system is now in actual use in line operation on one of UAL's West Coast routes, to see how it will work in high density areas, and especially to see how hard it will be to co-ordinate with ATC. Special approach charts have been made up for the scheduled line tests and any 'bugs' will be shaken out. There will be critical comments from the pilots flying it, the Air Transport Association, the ALPA Safety Committee, and a number of other experts, after which unrestricted FAA certification for the new system will be obtained.

I have flown a number of simulator two segment approaches. Like other pilots who have sampled the newest idea in quiet flight, I am enthusiastic, and can predict confidently that the two segment approach will be the standard landing profile for big city airports in the near future.

(Shell Aviation News)

Brief News Items ATC Agreement Federal Aviation Administration and Radio Aeronautica Mexicana, S.A. (RANSA), have signed a co-operative air traffic control agreement affecting U.S. and Mexican cities.

Under the agreement air traffic control facilities in six neighbouring pairs of cities are authorized to enter into letters of agreement setting down communication requirements for specific flight procedures and methods of coordination to be followed at each location. The agreements will allow controllers on both sides of the border to direct aircraft more safely into specific patterns.

38

City pairs involved are: El Paso/Juarez; Brownsville/Ma• tamores; San Diego/Tijuana; McAllen (Tex.)/Reynosa; Laredo (Tex.)/Nuevo Laredo; and Imperial (Calif.)/Mexicall.

Freedom of Speech in ATC By citing the Freedom of Speech First Amendment, and by calling three women controller witnesses who said cursing was common and acceptable language, a General Counsel overturned a 3-day suspension for a U.S. controller in a recent case.

In an imaginative defense, the Counsel proved how common a part of the English language profanity is today.

The women, who worked at the same facility as the suspended controller, said they found nothing offensive in others cursing, that they accepted it as normal language during work, that it did not affect the job adversely in any way - in fact, that it was a perfectly acceptable way of releasing tension.

The Counsel brought out how the controller had merely mumbled to himself, not intending the term to be broadcast, nor overheard, and also showed that another controller who reported the incident, himself later said to the • • suspended controller, "You ... jeep." Counsel argued that what is profane or not is fixed by the particular community or context involved. The resultant arbitrator ruling does not give controllers the right to curse, however, but FAA must set guidelines as to cursing which are uniformly enforced.

Concorde in Near Collision Concorde's recent visit to Bogota, Columbia, to demonstrate its performance at the city's 8,355-ft. elevation El Dorado airport nearly ended in disaster when a light aircraft on a photographic mission flew into Concorde's takeoff path forcing Cpt. Jean Pinet to make a violent evasive manoeuvre at an altitude of less than 400 ft. Concorde missed the other aircraft, a Cessna 172, by about 100 ft.

The light aircraft, flown by a Columbian pilot, had been circling the airport at an altitude of about 500 ft., and on a final pass up the runway prior to Concorde's take-off, the Cessna pilot advised the control tower that he was making a 360-deg. turn to the left to clear the way for Concorde. The tower then cleared Concorde for take-off and asket Pinet to initiate a 45-deg. right turn after take-off in a noise abatement procedure designed to avoid a small village of the end of the runway.

As the aircraft rotated, co-pilot Pierre Dudal remembered the Cessna pilot had said he was going to make a 360-deg. turn, which if followed would bring him back to the runway. As Pinet started the right turn, Duda! looked out his right side window and saw the Cessna on a collision course. Unable to warn Pinet in time, Dudal pushed Concorde's control yoke forward. Pinet looked up and rolled Concorde out of its medium-banked turn to the right and into a steeply banked left turn. The miss distance was less than 30 meters - about 100 ft. - as Concorde ducked under the light aircraft. Pinet then rolled Concorde back to the right and regained the noise abatement profile.

Passengers and crew in the aft cabin were startled by the violent low altitude manoeuvre. Some thought the pilots had difficulty during the high elevation take-off. A formal near miss report was filed by the crew. {Aviation Week & Space Technology)

"Al RCAT": T-VT's News Systems Concept for ATC

~

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( Primary

and Secondary

)

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METEO DATA

ADJACENT CONTROL CENTRES

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Plans

figure 1

T-VT, a subsidiary of the French Company THOMSONCSF (one of IFATCA's Corporation Members) has evolved a new systems concept for Air Traffic Control, called "AIRCAT".

The principal features of "AIRCAT" (Automated Integrated Radar Control of Air Traffic) are its flexibility regarding the radar configuration (either en-route, or terminal, or mixed control} and the control sophistication (degree of automation of radar data processing and of flight data processing).

General System Configuration The general configuration of the AIRCAT system is shown in Fig. 1.

Radar coverage is assured by a network of detection centres, each detection centre comprising primary and secondary radars.

These detection centres are of two principal types: long range for exclusive en-route control, short or medium range for terminal or combined terminal/approach control.

The en-route radar data are locally processed and converted into digital form for narrow band remoting to the Area Control Centre.

The TMA stations radar signals are fed to the TMA/APP centre for use in raw form, while its SSR signals are digi-

tized and narrow-band remoted to the Area Control Centres.

Data coming from both types of stations are gathered in Area Control Centres (see fig. 2) where the airport radars are used as gapfillers when detection losses occur.

The number of radar stations depends on the configuration of the country involved (geography and airspace situation). A standard AIRCAT centre can work with as many as four radars. The number of ACCs depends more on the control philosophy adopted: although it is possible to concentrate data coming from all the radars in only one ACC, it is more often judged preferable to break down the system into several medium size ACCs, as is the case in France.

General Exploitation Considerations Two cases are to be considered: terminal and en-route control centres.

Let us first consider terminal control. The raw radar signals are locally available and they can be used just as they are: the primary radar information is displayed on viewer units of conventional type (classic radar sweep for IFR, and TV bright display for tower cab), and the SSR video undergoes a defruiting process before being employed in decoding units which serve the control positions.

39

A second solution for such a control centre is to display the processed SSR data in synthetic form. To the primary reply, still displayed in analog form, a label is added containing the SSR data (identity code and flight level).

A third solution is to display a fully processed and purely synthetic picture, as is the generally accepted solution for en-route control.

Let us consider now this solution which is applicable to any type of control centre.

The radar plots are received as digital messages over telephone lines. These messages are demodulated prior to feeding the central processor. Each message contains all the data collected by a radar station (primary and associated secondary) about a given aircraft on each antenna revolution. The central processor performs the tracking operation on the incoming messages and provides other functions such as digital video mapping, picture allocation to the various displays, correlation with flight data if any, etc ....

Whatever the level of system sophistication, this processor may be considered as the heart of the display equipment.

The Synthetic Picture

F3

1 : AIRCRAFT

DETECTED

0:

NON OET[ClED

AIRCRAFT

,.

A

figure 2

Passive decoding is achieved by comparing the incoming codes to codes preset by the operator; when a satisfactory comparison has been achieved, the corresponding aircraft is displayed on the PPI by a preset symbol (combination of thin and wide slashes). Emergencies are automatically signalled.

Active decoding is carried out by designating on the PPI the relevant blip with a light pen: the corresponding SSR identity and flight level appear in numeric form on the decoder read-outs.

Area of_ general information

-Micro.table

~

The viewer units used for the control of traffic have 16 or 21 inch diameter screens, depending on control requirements.

They have a low persistance and high picture refreshing rate (of the order of 50 times per second) hence permitting operation in normal ambiant lighting.

A new, tri-chrome display has been developed for use in AIRCAT systems.

The various components of the picture are (see figure 3): The radar tracks (mosaic picture made up of data from several sources), the video map, the general information area, the micro-table, the validation area, weather clutter areas (when processed meteo radar data is available).

Each track is basically composed of a position symbol, see figure 4 - one symbol for primary tracks, another for secondary tracks and super-imposition of both for associated tracks - representing the aircraft's present position and followed by a dot trail indicating recent past positions (track history).

To each track is added a linked label of three lines: first line: identity (SSR code or call-sign), second line: FL with reference (C for SSR, B with regard to transition level, blank for cleared level) and computed ground speed, third line: special data introduced by the controller, and emergencies.

Validation area

Radar track with figure 3

40

label figure 4

(referenced from A to P) with the SSR code/flight number correlation which includes the flights expected in the sector concerned, flights for which tracking has been momentarily interrupted (followed by "L" standing for track lost), and flights stacked in a holding pattern (followed by "H").

The validation area (figure 6) has a fixed place (lower part of the screen) and is only displayed and used for the preparation of the messages to be entered by the controller into the processing system. These messages are keyed in and checked prior to execution. This special area is used for any active operation of the controller by means of the data entry devices (keyboards, rolling ball ... ) such as flight data entry, read-out or cancellation, hand-off procedure, holding enter or exit, microtable positioning, etc.

A A3121 AF203 B A151 5 AC871 H C A1573 SU30 2 H D A1580 R1<03 E A1560 OA201 L F . . . FA312 G . . . . FA315 H A1575 PA809 I A2215 SR 72 0 J A2216 SR723 I< A2223 IT944 L A2224 IT 71 0 M A2226 IT808 N A2227 AF212 0 A2233 Sl<565 p A2234 l<L405

.

.

.

AIRCAT: Progressive Sophistication The AIRCAT system has been designed for application to any ATC situation and different phases have been defined corresponding to several degrees of automation, up to the highly sophisticated configurations planned for the 1980's.

figure 5

A letter is attached to the track for identification of the control sector in charge of the flight. In order to clarify the individual pictures, the complete label is normally displayed only for the sector controlling the flight.

The video maps (several are possible, such as runway lines for terminal operation) are displayed at the controller's discretion; they consist of straight lines to represent the airways, schematized borders, etc .... and various symbols representing the different beacons.

The general information area is a fixed zone at the upper part of the screen in which are displayed data such as time, summarized met information, local barometric pressure, etc ....

The micro-table (figure 5) does not have a fixed place and is positioned by the controller himself where it does not interfere with the radar picture. It contains a list of flights

----------

Phase 1: Exclusively reserved for terminal control, in two distinct steps: 1A: Primary and secondary radar data are digitized and automatic tracking is performed. Information from both radars is displayed on PPls in synthetic form. Labels associated to the radar tracks provide aircraft identity (SSR code display) and altitude extracted from mode C reply.

18: The possibilities of 1A are increased by adding rolling balls and keyboards on the radar consoles to enable the controllers to manually enter the SSR code/callsign correlation, the call-sign then replacing the SSR identity in the track label. These additional devices also permit the "Range and Bearing Line" operation.

Phase 2: Applicable to medium size ACCs, also in two steps: 2A: The radar processor comprises a mosaic input module enabling data coming from several radar centres to be processed together to provide a composite picture covering an extensive area. A mini-computer working in relation with the radar processor permits flight plan data to be displayed on the radar screens. Data con-

INDEX ROW

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41

FL

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figure 8

figure 7

cerning regular flights, recorded for the whole day are stored on magnetic tape or punched cards, the tape recorder and the card reader are connected to the mini-computer; non regular flight plans may be entered through tele-printer.

28: Non-scheduled flight data are entered through keyboards and presented on tabular screen. The keyboards can be suppressed by using the "DIGITATRON" terminal display (figure 7) which is a touch input device able to display a "dynamic keyboard" used to key in the messages, and to display the flight data (figure 8).

Phase 3: Applicable to heavy traffic ACCs, improvements are applied only to flight data processing, via three steps: 3A: At this level, the system is fitted with a ·powerful computer complex for the purpose flight plan computation, editing and distribution, and transmission - through the

,,Down-under" Controllers Dumbfounded Australian and New Zealand oceanic controllers were recently upstaged all the way by a position reporting USAF C141 Starlifter (MAC 70011) on his trip across the Tasman from Christchurch to Richmond. His reporting points were Chairlift, Skijump, Spurdog, Wrasse and Sydney.

Position reports were made as follows: 1955z: - "Auckland - MAC seven double oh double one departed Christchurch at double five climbing to flight level three five zero and estimating Chairlift at double two."

2022z: - "Auckland - MAC seven double oh double one was Chairlift at double two flight level three five zero and estimating Skijump at double five."

2055z: - "Auckland - MAC seven double oh double one 42

AFTN - of the messages to other control centres (civil, military, foreign) and to control towers.

38: Automatic flight plan up-dating is performed by correlation with the radar data. The flight strips are updated before aircraft entry in the sector.

3C: By increasing the computer capacity, collision avoidance is assured through the conflict prediction. The computer carries out the flight plan computation for all aircraft, the comparison of each flight to all others, and displays the predicted conflicts in the "Flight Plan Correction" room.

Al RCA T: Operational To-Day, Armed for Tomorrow The equipment and software utilized up to phase 3A are entirely produced within the THOMSON-CSF group and assembled by T-VT. The standard equipments have been designed in such a way that they constitute basic modules for the various alternatives, hence enabling progressive evolution starting from a simple installation. These basic equipments (radars, processing units and displays) are periodically up-dated to follow technological evolution, thus continuously improving performance but nevertheless preserving further up-grading capability. By this means, a currently operational system will be progressively up-graded to take on the work of the future.

was Skijump at double five flight level three five zero and estimating Spurdog at double three."

21332: - "Sydney - MAC seven double oh double one was Spurdog at double three flight level three five zero estimating Wrasse at double two double two." At this stage he calmy requested "flight level double three zero?" He was knocked back on principle by a somewhat apoplectic controller.

2222z: - "Sydney - MAC seven double one was Wrasse at double two double two flight level three five zero and estimating Richmond at double five."

Needless to say, he won by 5 reporting points to love and three speechless controllers. We don't know if it's true but we got it on the hot line that he ordered double caviar and chips and a double brandy in the mess at Richmond.

(Cocodoodledoo,

Australia)

News from the Federation

Mr. Chonacki (2nd from the left) informs the Executive Board and an Austrian delegation {Mr. Schyr and Mr. Kihr) about ATC Poland.

Meeting of the Executive Board, Zagreb, 18-21 February, 1975 The customary spring meeting of the Executive Board was held in Zagreb, Yugoslavia, from 18-21 February, 1975.

With the exception of the Editor, all members of the Board attended the meeting.

Main items on the agenda were: discussion of the reports by the Officers, Standing Committees, Regional Councillors and others in preparation for the 14th Annual IFATCA Conference in Melbourne, 14-18 April, 1975; a review of all the Federation's activities including cooperation with international organisations and the organisation of the Melbourne Conference, and many other topics.

Lengthy discussions took place on the reports by the President and Vice-President Administration regarding their visits to South America and possible action by IFATCA to assist the South American countries in their endeavours to improve the working environment, while on the subject of the arrangements for the Melbourne Conference, the Officers stayed in session until late at night on two occasions.

The Board was invited to take a look at the new Air Traffic Control Centre at Zagreb, scheduled to start operations later this year. This is a very modern unit, equipped with a Stansaab Radar and Automation System (Stansaab are Corporate Members of IFATCA). The members of the Board were introduced to representatives of the civil and military Air Traffic Services, the Airport Authorities, the major Airlines serving Zagreb, and colleagues of ATC Zagreb, Belgrade and Ljubljana.

The occasion proved a good opportunity for members of the Austrian Association to introduce a representative of the Polish Air Traffic Services to the Officers of the Federation. Mr. Jacek Chonacki, Chief of Air Traffic Services, Warsaw, explained to the Board the problems existing in ATC Poland and the conditions under which the Polish Air Traffic Controllers' Association, now being formed, could affiliate with IFATCA. The Federation offered its assistance to the Polish Authorities to realise plans for the modernisation of the Warsaw Air Traffic Control Center, and the hope was expressed that the Polish Association would soon join the international controllers' community.

During a press conference, the aims and activities of the Federation were outlined, while press coverage of the meeting and a 6 minutes TV evening broadcast featuring ATC and IFATCA achieved much publicity for the profession and the work of both YATCA and IFATCA. On the last day of the meeting, Mr. Ante Cuculic, Chief of Protocol and Secretary for International Relations to the President and representing the City Assembly, gave his respect to the Board and to controllers the world over. Mr. Cuculic said that he travelled many times by air and that he had always admired the smooth operation of airline travel. This, he believed, was an indication of the good work done by air traffic controllers.

The Federation is much indebted to the Yugoslav Association, in particular to Mr. Bernard Dujmovic (President), Mr. Tomislav Karner (Secretary) and Mr. Giric Bozidar (Treasurer) for the splendid arrangements made and the warm hospitality offered.

Investigation of Aircraft Incidents and the Legal Liability of the Controller The present system for the Investigation of aircraft incidents related to the Air Traffic Control field, and the legal liability of the Controller for both such incidents and aircraft accidents, have been - during past IFATCA Conferences - the subject matter of Working Papers and studies

by IFATCA's Legal Committee. Whilst a sophisticated system of accidents investigation exists with procedures established under ICAO Annex 13, no such system is in operation for the investigation of Incidents. The Federation has therefore submitted to ICAO a number of suggestions for possible adoption into ICAO Standards and/or Practices.

Different States adopt different procedures for investigating such incidents generally, but IFATCA deems it essential that ICAO should undertake the formulation of procedures and practices to be incorporated in a new Annex or in Annex 13, for the purposes of safety and standardisation. Two of the points put forward are: (1) the Investigator should have the appropriate experience in Air Traffic Control, Aeronautical Engineering and other associated

43

areas; and (2) the causes of Incidents, layout of reports and all relevant material necessary for the avoidance of future similar incidents should be published.

As for the legal liability of the Controller, IFATCA pursues means through International Conventions introduced

by ICAO to protect the Controller within reasonable and legal boundaries, and the Federation is determined that the execution of his duties are international in nature and should not be covered by national legislation as at present.

In many countries the Controller is liable to be imprisoned for the tort of negligence which will result in his financial ruin and loss of career. The Controller should not be the subject of such catastrophic consequences unless his guilt is the subject matter of criminal negligence. Fear of all such unfortunate consequences will most certainly be in his mind and may act as a negative factor in terms of safety in the air.

The objectives of the Federation in pursuing the adoption of the above principles in International Conventions are purely professional in an effort to increase to its maximum the efficiency and safety Standards of Air Traffic Control.

IFATCA President's Visit to Argentina and Uruguay Following President J.-D. Monin's 10-day visit to our Member Associations of Argentina and Uruguay in December 1974, Mr. Monin has written to Her Excellency the President of the Argentine Republic, expressing - on behalf of the Federation - his great concern about the situation in the Argentinian Air Traffic Services, where seventeen em-

ployees have been suspended from office, among them six controllers, while further sanctions appear likely.

Mr. Monin's letter continues: "I hope you will accept that my approach to the situation in question is based solely on professional grounds and does not represent an attempt by our Federation to get involved in politics or other matters. However, we know from experience that whenever the climate deteriorates within the Air Traffic Services due to difficult circumstances, the SAFETY in the air becomes impaired with all the consequences this may have for human lives and property. Therefore, I appeal to your Excellency, and ask you to do all you can to restore the situation in the Civil Air Traffic Services in Argentina back to normal, with the hope that all suspended personnel will soon be allowed to resume duty. Having myself much appreciated your strong presentation to the International Labour Conference earlier this year, I am confident that by your personal intervention a solution will be found out of the present difficulties in the interests of SAFETY and efficiency of Civil Aviation in Argentina."

In Buenos Aires, IFATCA's President had discussions with the Director of Air Traffic Services, Commodore Gandolfi, and in Montevideo with the Director of Civil Aviation, Colonel Atilio Bonelli. Accompanied by our Regional Councillor for South America, Mr. J. Beder, a number of visits were made to ATC establishments in both countries. After his return from South America, Mr. Monin distributed a nine-page report to the members of the Executive Board of IFATCA outlining the problems with which our colleagues in the region were faced, and this report was the subject of discussion at the Federation's Annual Conference in Melbourne, Australia.

News from Member Associations Luxembourg The Guild has been much concerned of late about a number of improvements, which, in their opinion, are needed to give the air traffic control service in Luxembourg new impetus. Luxembourg controllers have no familiariation flights; they have no refresher courses to bring their technical knowledge up-to-date; are not issued with licences and other documented qualifications; and have no radar service. The Guild has approached the Federation for help to convince their Administration that these proposals should be implemented as they are very reasonable and are no more than those already implemented in the countries of many MAs. The Executive Board of IFATCA trusts there will be a change of heart soon by the authorities in question as this would be in the best interests of aviation. An approach along these lines has been made to the Minister concerned.

Canada The governing body of the Association, the National Council, will convene in Vancouver in May 1975 in conjunction with CATCA's National Convention. At its last meeting held in Regina, Sask., the Council took a strong position in opposition to the proposed phase out of PAR facilities on the grounds that discontinuance of this faci44

lity will add to the hazards of flight. The Association proposes that, rather than phase out PAR, its use should be expanded to other airports so that more IFR arrivals can be monitored. The Council has also voiced its deep concern about proposals to assign any functions directly involved in air traffic control to unlicensed personnel.

An item of particular concern is still the long-standing problem of achieving an early retirement plan for controllers.

The majority of results of a survey conducted among the membership are now available for review and assessment by the Council. The answers to several questions posed to the membership appear to confirm the established aims of the Association in this area. Of equal interest, and requiring detailed study and consolidation, are the large number of written comments submitted. In general, it can be said that the survey reveals an abiding concern about an equitable retirement plan for controllers and a responsible attitude toward achieving it.

Moncton Controller credited with Rescue A Monctor air traffic controller, Mr. R. Chase, has been deemed largely responsible for the rescue of four occupants of a single-engine American registered Cessna 420 on a flight from Seven Islands to Fort Chimo, a distance of 600 miles over almost completely isolated and uninhabited areas, and which crashed 32 miles north of Labrador City, September 12 1974. Mr. Chase, a controller at the

Moncton Area Control Centre, exhibited something of a sixth sense in concluding that something was amiss concerning the safety of an aircraft he had been tracking.

Overflying Labrador City, the aircraft experienced difficulty in maintaining altitude, and the pilot was cleared to fly at a low altitude due to severe icing conditions. At that time the pilot expressed no concern for t~1e safety of the aircraft.

However, Mr. Chase sensed something was amiss and tried to contact the aircraft several minutes later. When he received no response, Mr. Chase alerted the Rescue Coordination Centre at Halifax, and an aircraft was immediately sent to the search area. The Cessna 420 had, in fact, crashed tail first into extremely rough country and was completely destroyed by fire. All four occupants received serious injuries, one being very critical.

Within three hours of being alerted by the Centre, a para rescue team jumped into the crash site. Within the hour two helicopters picked up the survivors and transported them to the Labrador City hospital. This prompt action was credited with saving the lives of two of the severely injured survivors.

United States PATCO President John Leyden has outlined four safety necessities in a letter to President Ford, immediately after the crash of TWA Flight 514 into the Blue Ridge Mountains outside of Washington, D. C. The action plan, which received wide and favourable coverage in the news media, consists of: 1. Mandatory radar monitoring of every airliner from the moment it leaves the ground to the moment it lands; 2. Installation of ILS at every runway which airliners use; 3. Re-installation of PAR at every commercial airport; 4. Installation of proximity warning devices in every airliner cockpit (now made mandatory by the FAA - Ed).

Leyden pointed out the number of air crashes which have occurred in the last two years, claiming hundreds of passengers' lives, basically because the controllers lacked the use of certain tools needed to ensure safety. The PATCO President and other national officers have also responded to enquiries from the news media in order to clarify the responsibilities of controllers to monitor the aircraft in question; this became necessary because of the premature release of the tapes of the accident. Many reporters, upon hearing them, made their own interpretations as to the cause of the accident. Leyden and others appeared on national TV, as well as being extensively quoted in the press and on radio, especially in the Eastern Region of the country. "Such an accident proves more than ever the need for an organization like PATCO, to stand up for controller rights, and to make sure the public is not misinformed," said the President.

PATCO also delegated its representative at the Dulles Airport to represent controllers at the National Transportation Safety Board investigation of the accident.

On another topic, namely the FAM Flights Scheme: after the restoration of the program to its former status, as a result of the change of mind by the airlines who had refused to continue with the scheme because of alleged misuse (see our Febr. 1975 issue), PATCO's President has issued a statement regarding participation in the program.

In pointing out certain standards which members are asked

to adhere to, the Organisation is not attempting to police its membership, but is seeking to eliminate industry complaints and to foster better relations within the ATC community.

In the President's statement, PATCO members are asked - among other things - to be punctual; attire should be appropriate to the conduct of government business; the FAA 8-hour rule on alcohol should be adhered to; areas of mutual concern should be discussed with flight crew, including but not limited to procedures, equipment and other safety related areas; movement should be restricted to flight deck during the flight; etc.

Australia The Association is concerned about the rumoured closing of the ATC Training College in Melbourne to new recruits and with the present staff shortage, an extremely uneasy situation could develop in that by June this year no trainees will be in the "pipeline", thus effectively halting most promotion from the lower ranks even whilst retirements and resignations still remain. The situation is similar to that which existed in the U.S.A. some time ago, when PATCO time and time again warned about the serious consequences which such a policy would bring to the safety and regularity of air traffic.

A continuous inflow of new recruits is simply essential in all Air Traffic Services the world over, but it seems that this lesson has not yet been learned universally.

The Association has attended two meetings with the Public Service Board and one with the Dept. of Transport to discuss conditions of service for Darwin members following the disaster of Cyclone Tracy. Among the matters discussed were: accomodation costs of the families of staff remaining or resuming duty in Darwin; accomodation- and expenses allowances for staff now located other than in Darwin; an expenses based travelling allowance for staff on temporary transfer to Darwin; and allocation of a first class return air warrant to a nominated mainland capital, or location in Australia of evacuated family member or dependent, with two weeks leave.

The long term plan is to fully restore the staff and facilities at Darwin, but this will depend upon the plans of the Darwin Reconstruction Authority. It is anticipated that 6 A.T.C.O.'s will be required in the immediate future until there is full restoration of facilities and adequate accomodation becomes available (31 A.T.C.O.'s were employed in Darwin as at 24. 12. 74). An Operational Control Unit giving 14 hours coverage, and working on delegation from Alice Springs is being planned. Flight Service Briefing will supplement A.T.C. Briefing.

Limited Approach- and Aerodrome Control is currently being provided by the RAAF. The Department will oppose the reintroduction of international movements at Darwin in the near future, will allow APT domestic movements, and limit G.A. operations as far as possible. Night movements are restricted to a minimum because the staff are concerned about the security of their families and property, and also because it cuts down on the number of people required in Darwin. As for staff accomodation, the Department will lease motel type accomodation adjacent to the airport (26 rooms and one 12 man dormitory - with 2 to a room, over 60 could be accomodated). The Department expects having these premises on lease for at least the next 12 months, and hopes to build more accomodation next 45

door. The Department also has bookings on 36 beds spread over 4 motels (2 to a room), and has 14 beds in caravans.

Between 1000 and 1500 houses (government and privately owned) which are currently unoccupied are being made habitable and will be allocated as they become available.

The Department will not insist on anyone staying in Darwin against his wishes. It is intended to staff Darwin on an occasional basis e. g. 3 to 4 months, and then pull them out, and it is hoped that the stage will not be reached "of directing staff to go to Darwin". The Association was warned, however, that the Department could anticipate Association opposition to the consciption of people, as it feels that if the Department wants people to go there then the conditions of service must be good enough to attract staff to Darwin.

Cyprus The Association has been deeply moved by the generous gesture of the members of the Eurocontrol Guild to donate a sum of money to the Cyprus Association in view of the continued discomfort and suffering of the inhabitants of the island. The Eurocontrol Guild, in an accompanying letter, expresses admiration for the courage demonstrated in the Association's efforts to re-establish ATC in the region, and the Cypruis Association, in reply, has confirmed that their members are continuing to pursue by all lawful means the re-establishment of normal conditions in ATC.

Letters from Readers An Appeal to Controllers the World over Following the successful symposium on Stress in Air Traffic Control held in Manchester in 1973, a Committee has been set up by the British Guild of Air Traffic Control Officers to advise on aspects of medical factors as they influence safety on duty.

As independent Chairman of this Committee I should like controllers everywhere to submit anonymously if preferred, any details of incidents of a stressful nature from whatever cause (failure of equipment, sudden disturbing influences, personal overloading of traffic or any intimate personal disturbance, etc.) which might have left a doubt in the controller's mind about its effect on his ability to cope at that particular moment.

As a professional person I can assure any correspondent of complete confidentiality. The information will be discussed only by my Committee for use in a future symposium on this subject in 1976, and any names submitted will be retained by me solely, if so desired. The basis of any future symposium on air safety will depend very largely on your replies.

Dr. N. C. Brown, 119 Park Road, Timperley, Cheshire, WA15 600, U.K.

News from Corporation Members Software Sciences Ltd. Software Sciences continue to design and apply computer models of Air Traffic Systems in the Air Traffic Management role. Amongst projects recently completed has been a series of Fast-Time Simulations of the Rome TMA to evaluate alternative new route structures and to investigate the workload and complexity of alternative modes of operation ·and sectorisation at the Rome ACC. An important element of the Company's contribution to resolving Flow Control problems has been the develop· ment from an earlier SSL model of an Arithmetical Model representing Air Traffic Flows, which has been supplied to Eurocontrol as a simulation tool to assist in ATC Planning and Research.

Communications Ltd., a major supplier of aircrew communications headsets, were invited to offer for evaluation a headset to complement the radio system in the Lockheed 1011 TriStar fleet of British Airways (European Division).

After extensive evaluation at Palmdale, California, by both British Airways and Lockheed, one of the "Astrolite" range of headsets, the Model 2700, was approved for use as standard aircrew communications equipment on the flightdeck of the TriStar. This acceptance was followed by a similar long evaluation of a special version of the Ampligard ear defender headset for use by all ground maintenance personnel. The "Ampligard" has also been approved for use with the British Airways TriStar fleet.

Marconi Radar Systems Ltd. Racal-Thermionic Ltd. Among tie magnetic tape recorders manufactured by Racal-Thermionic Ltd. is the Store 4 Instrumentation recorder. This instrument is used with automotive machines, including helicopters, for vibration analysis tests of aerofoils, airframes and turbines. A seven channel IRIG compatible addition to the company's Store aero range of products is the Store 7 and this was shown at the 1974 Farnborough Air Display along with an example from their digital cassette range, the P70N. This latter is a military version of the renowned Digideck which is able to withstand the inhospitable environments of in-flight conditions and con· forms to Table N of DEF 133.

Another member of the Racal Group, Racal-Amplivox 46

The company is carrying out a US $ 720,000 contract awarded by the Civil Aviation Division of New Zealand's Ministry of Transport, to upgrade the 50 cm radar system for the Wellington Air Traffic Control Centre. This will form the first stage of a complete modernisation of Wellington's radar, originally supplied by Marconi in the early 1960s.

Among the new equipment will be two type S7100 digital signal processors, type S3017 displays and type S3202 video map generators.

International Aeradio Ltd. International Aeradio's worldwide involvement in the provision of aviation technical services includes the new

"Rapidex" Passenger Security Screening system, airmobile band VHF equipment and Aerad flight documentation.

With over 3500 skilled staff strategically positioned in some 50 different countries, IAL undertakes the provision, operation, management and maintenance of technical equipment and the training and provision of skilled personnel for the operation of air traffic control services, aeronautical telecommunications and navigational aids, meteorological services, fire and rescue facilities and airport management.

The "Rapidex" passenger security system is designed as a fast and effective method of screening passengers and their hand baggage. It incorporates metal detection, baggage x-ray and explosive vapour detection. It is easy to install, requires only two operators and enables passengers to be screened at a rapid rate.

Other new equipment includes a six-channel mobile radio telephone unit for airport service movement control, a VHF ground direction finder with a novel digital presentation and an air traffic control console for the smaller airport, all manufactured by Park Air Electronics Ltd., one of IAL's 25 subsidiary and associate companies.

The Aerad Flight Guide is used for air navigation purposes on the flight decks of aircraft the world over. The complete Guide consists of some 2700 charts and four supplements but for ease of handling it is divided into 14 volumes with each volume containing information on a specific area of the world.

The new 250-watt transmitter is intended for aeronautical ground stations requiring extended-range VHF communication in the 118-136 MHz band, and offers the same advantages as the SO-watt transmitter. The output is obtained from 7 linear amplifier modules coupled together on the Posthumus bridge principle. A standard 19-in. cabinet will accomodate two such transmitters with their power supplies. If the temperature in the amplifier modules oversteps a certain limit (rarely reached under normal working conditions), a blower will be started automatically.

The new Doppler-VOA combines the concept of the new SO-watt transmitter with the techniques used in the VOA equipment that has been in production for some time.

In addition to DC + LF envelope feedback it also uses phase feedback. The sound construction, high reliability and minimum maintenance are borne out by the use of ceramic integrated circuits and of heavily derated components. The D-VOR is an all-solid-state system, using semiconductors even in the antenna distributor, and is a modern DSB system which has been found superior to alternate sideband systems from which it differs in radiating both sidebands simultaneously.

It is supplied with a digital monitor for ground check.

The angle measured is indicated by an LED display. The monitor can be installed at any angle in relation to the DVOR. The AC prime power may be taken from normal mains, or a no-break diesel-operated generator, or a charger and battery inverter combination.

Philips Telecommunications

Cossor Radar and Electronics Ltd.

PTI are marketing two new VHF transmitters and a Doppler-VOA which are based on a new technical concept, making the signals particularly accurate, linear and stable.

Using solid-state techniques, the new SO-watt VHF transmitter is intended for ground-to-air communication and offers a choice between two frequency ranges: 118-136 MHz for civil and 136-156 MHz for military applications.

The use of low-power modulation has permitted the application of DC + low-frequency envelope feedback, resulting in signals of remarkable linearity and stability. Thus the distortion measured at 90 % modulation depth is only 2 %.

The approach used actually permits modulation depths up to 98 %. To make the most of this, the low-frequency modulator incorporates a compression amplifier which ensures optimum modulation depth without the risk of over-modulation. The stability stands out also under mains voltage fluctuations. Although the power supply is not regulated, the DC component in the feedback system ensures that mains fluctuations of± 10 % cannot make the output power vary by more than ± 0.35 dB. To achieve high reliability, the transmitter was designed for minimum complexity and much attention was given to components and materials. The chassis is of stainless steel and robust Philips VHF transistors are used. The use of broad-band techniques combined with a built-in reflectometer makes it simple to tune the transmitter to its working frequency. If the VSWR should become too high during operation, the reflecto-meter will automatically reduce the output power to a safe value. The transmitter will work satisfactorily even with a 100 % duty cycle. If so desired, six transmitters may be stacked in one cabinet. Practical provisions are: energising output for an external transmiV receive relay, a microphone jack, a push-to-talk switch and remote control.

The Company has been awarded two contracts by the British Civil Aviation Authority for radar plot extractor systems. The contracts valued at over £ 750,000 will provide the CAA with 8 dual and 1 single channel combined primary and secondary radar plot extractors each with monitoring facilities for installation at the Airways radar stations and single channel equipment for evaluation and integrity checking of secondary radar system performance at London's Air Traffic Control Centre.

Production of the Airways equipment will be carried out by Cossor at Harlow based on a model designed and manufactured by Stansaab AB of Barkaby, Sweden. The equipment to be Sl!PPlied is similar to that which was evaluated by CAA at'the Burrington Radar Station during the summer of 1972 and represents the very latest thinking in the design of plot extractors. The Integrity Cell programme was completed in 1974 and deliveries of the equipment specified in the Airways contract will commence in October 1975.

This success is the result of a collaboration started early in 1972 by which the two companies explored the possibility of a cross licensing agreement which would permit Stansaab to market and manufacture IFF transponders in Sweden, and Cessor to do likewise with plot extractors in the U.K.

International Air Carrier Association At the ECAC (European Civil Aviation Conference) in Paris, 3 December 1974, a presentation was made by an IACA delegation on the subject of the so-called "part-charter" concept. The Association feels that the subject is most timely as the civil aviation industry is passing through a 47

difficult period and it becomes necessary to create a truly healthy international air transportation system.

Under the part-charter ruling, scheduled carriers in the United Kingdom, for example, are permitted to market up to 50 % of the capacity of a given flight, or 70 seats if this number was more than 50 %, as discount tour packages in group blocks of 10 or more seats. This is a fare which is in direct competition with pure-charter operators (organised within IACA), and the adverse impact on these operators should be clear. IACA believes that world commercial aviation is courting disaster if scheduled carriers are allowed to pursue marketing practices that defy basic concepts of air transportation, and unfairly eliminate competition.

In the 18-page document, the IACA delegation sets out

clearly the pitfalls in promoting pricing in the financially troubled transatlantic services where growth has been profitless, even financially destructive. IACA feels that at the heart of the problem lies an irrational desire to obliterate competition. By the example of their profitless growth, the scheduled airlines in the North Atlantic have demonstrated the futility of attempting to maintain fully creditable scheduled services that cater principally to cut-price demand.

Part-charters perpetuate this folly, as the principle symptoms of profitless growth will persist, namely selfdiversion of traffic, declining yields, overcapacity and eventual erosion of service to the public.

The concept of part-charter is unsound and inequitable economics, as it inescapably undermines the economics of the airline industry.

Spotlight on a Corporation Member ASSMANN GMBH, West Germany: More than 25 years of Audio Telecommunication Products Comprehensive world wide communications facilities are the vital basis for the efficient exchange of goods and effective exchange of speech and ideas. To broaden this basis and to cater for the increasing demand for additional communication services, a continuing program of improvement and expansion is necessary. ASSMANN, in endeavouring to meet the specification requirements of potential customers throughout the world, such as ATC authorities, have contributed for more than 25 years to improved, modern communication systems by the development of two groups of Audio Telecommunication Equipment. These two groups of products achieve the following main design aims: 1) Automatic Announcing. This is performed by: (a) Intercept machines for short ·messages, giving one or several fixed messages which have been prerecorded; (b) Variable-message-length announcers for longer messages which are changed at certain intervals, providing information concerning weather, surface conditions, etc.

2) Automatic Monitoring of all communications in a communications network (Multichannel Communications Recorders, up to 36 cannels).

Speaking Clock and Multitext Equipment complement the Automatic Announcer group of equipments. Special passenger announcement composition can be achieved by selection from a number of pre-recorded phrases and segments as required in airports. Both groups of equipment have been application-designed and engineered. By use of heavy duty mechanical and electronic components, troublefree service with 24 hour unattended operation over long periods of time has been achieved. Many ASSMANN customers throughout the world still use equipment which has been in continuous use for the past 20 years.

ASSMANN GMBH need no introduction to the IFATCA family. The company regularly exhibits at the Technical 48

Exhibition during our Annual Conferences, and IFATCA '74, held from 20-24 May last year, was no exception. However, to give our many other readers outside the immediate IFATCA circle some idea of what this IFATCA Corporation Member puts on the communication market, the following is a brief outline of the company's manufactured products:

Automatic Message Announcers There is the Variable Message Length Repeater FAG-100 for one message from approx. 4 seconds up to 14 minutes length (automatic adjustment), with remote control facilities for all methods of operation, built-in recording facilities and magnetic recording disc without guiding grooves (up to 20 services in one system are available). The system is used by Telephone Companies, Department Stores, Banks and especially Airports for messages which are updated frequently such as weather reports, weather forecasts, etc. Two units FAG-100 used in alternating service are ideal for ATIS (Air Terminal Information Service), considerably facilitating the daily work of the controllers. Additional components to the FAG-100 are making this system also ideal for VOLMET services. A less sophisticated but also professional Variable Message Length Repeater - similar to the FAG-100 - is the new type ATV with a maximal text length of 4 minutes.

In another Series, ASSMANN manufacture Short Text Announcers HAG-1, 3, 4 and HAG-5 and -10 for intercept announcing in public and large private telephone networks, and also for ILS identification. The international "Special Information Tone" and up to 32 different messages are prerecorded and are available simultaneously during one revolution of the recording medium (magnetic recording disc without guiding grooves). The system is also used for announcements to passengers in railway stations, airports, elevators and for alarm announcements in mines and industry. The maximum length of the message varies from approx. 2 seconds to 11,5 seconds, depending on the type in use.

A further new development, type ATF, is applicable for recording and reproduction of up to 16 different announcements one after the other with a maximum text length of 11,5 seconds each.

There is also a 40 Channel Announcer ME 3. The 40 different announcements with a length of up to 60 seconds each may be made in any sequence required - one after the other, one message at a time. The building block system permits the design of complete announcing systems as required in railway stations and airports. Such systems are capable of multilingual and most flexible announcements by composing announcements from phrase segments taken from two or more sets of Multitext units.

The system is also used in Department Stores, Elevators and in all such instances where the promotion of passenger traffic is desirable, including radio transmitting systems for traffic control along highways and GPO or PTT-Organisations for recording and for automatic announcing of alarm calls over public telephone systems. The recording medium is a magnetic recording loop, made from special rugged material for long life performance.

A similar system in application but a technically "madefor-the-future-system" is the latest ASSMANN development of the MCAG, a Multicomponents Audio Response Unit for COMPUTER-CONTROLLED VOICE OUTPUT of up to 32 different announcing elements simultaneously or selectable with text lengths of 0,5; 1; 2; and 4 seconds.

Multichannel Communication Recorders ASSMANN Multichannel Communication Recorders and Reproducers have been operating for many years and considerable improvements have been introduced to increase the reliability of this - the fourth generation. Maintenance has

become much easier, the need for which has been reduced to the absolute minimum. The new ideas of young engineers in conjunction with 25 years of experience by customers from all over the world. have resulted in the New Multichannel Communication Recorders / Reproducers Series MS 200 / MR 2000. Multichannel Communication Recorders differ from other professional and domestic recorders by the greater number of tracks and a more rigid design concept to ensure continuous round-the-clock operation without failure. The life expectancy is a 100.000 hours continuous operation with a minimum of maintenance.

The MS 200 Communication Recorders for voice recording have a maximum capacity for 36 parallel tracks. Capacity of one reel of double play tape amounts to 24 hours recording time, resulting in two full days continuous recording on one recorder. Mounted in a standard 19-inch cabinet rack, the standard model permits aural monitoring over tape and before tape for one track at a time, and simultaneous aural monitoring of two tracks and the time track.

Many new design details used on this model have resulted in a piece of equipment of utmost reliability and operational simplicity, even under most severe environmental conditions. Some of these features are: High Precision Tape Guiding System (vacuum sub-pression): for minimum wear of magnetic heads and magnetic tape; Continuous and Simultaneous Monitoring: the ASCAMPR system guarantees no delay in detecting a malfunction on any track with immediate switch-over to the spare track (ASCAM-PR: automatic simultaneous and continuous all track monitoring and parallel recording system); Logic Monitoring

assmann AUDIO-TELECOMMUNICATION

What's ATIS? "This is Sydney Airport Information: measured ceiling five hundred overcast, visibility one, wind one one two degrees at five, altimeter two niner niner two ... "

l

I:

Broadcasting all these message over and over every day, broadcasting them automatically thus reducing clearance length and enabling controllers to concentrate on precise vectoring for final approach and - last but not least - giving up-to-date-information to pilots as often as desired and required by using the Automatic Announcing System of ASSMANN.

Automatic Announcer Series FAG-100

. .. that's ATIS (Air Terminal Information Service)

ASSMANN

GMBH

D - 6 3 8 0 B A D H O M B U R G V. D. H. 1 German Federal Republic lndustriestrasse 5 • PoB 1147 • ~ (06172) *106-1 Telex 0415158 • Cables Akustik Badhomburg 1

49

and Alarm System: with selective fault-correcting system and automatic alarm selector which can be programmed by the user as required; Standardised Modular System: enables the combination of any equipment close to the user's specification; Stand-by Units: can be integrated with the automatic monitoring and fault-correcting system. This ensures, with the automatic spare track system, the optimum reliability of the equipment; Remote Indicator Unit; for comprehensive signalling of faults to a remote display location; Play-back Facilities: are available either as an integral part of the recorder or as a separate play-back unit (MR 2000). In addition, a wide range of extras are available at the user's selection for a special application and provides a variety of modifications.

The MR 2000 Communication Reproducer for replay is mounted in a portable housing, comprising tape deck and electronic sub-assemblies identical to the recorder.

Facilities for simultaneous playback of two tracks and the time track are available. Maximum capacity is 36 tracks (voice channels); 24 hours on one reel.

ASSMANN's New Generation of Time Announcing Units (Series ZAG-100) The recording of important radio- and telephone conversations for the purpose of documentary storage (as demanded by Air Traffic Control authorities) is useless without simultaneous time marking. The Speaking Clocks developed by ASSMANN make use of the grooveless magnetic recording disc, whose reliability has been proved in many years of service and which is particularly suitable because of its wear-resistance and long working life. In conjunction with the very robust indexing method (drive), many years of reliable operation with little maintenance are achieveid in this way. These "speaking secondary clocks" for both mains- or battery connection, are controlled by any type of master clock which supplies pulses or contact actuation at every second, or any ten seconds, or every minute. Many languages are available from the ASSMANN archives, recorded by male or female speakers in their home countries.

There are two types of equipment: (a) Speaking clock for announcements at one-minute intervals (ZAG-M), and (b) Speaking clock for announcements ·at ten~second intervals (ZAG-S). The speaking clock ZAG-M announces the hours and minutes, performed 15 times per minute. The ZAG-S announces also deca-seconds; there is one such announcement every 10 seconds. Depending on which type of equipment is used, either two or three pick-up arms are provided for the announcements.

Compared to the former types, the new series offer important improvements: Time adjustment has been simplified by omitting a clutch assembly. The adjustment of the minutes and deca-seconds is performed by fast-run of the motor, which is started by pushbutton operation only; wrong operation is impossible. The drive mechanism is equipped with a Hall-controlled and electronically stabilised DC-motor, so battery operation is possible. At mains operation the unit is independent from mains frequency.

Further innovations are: throughout silicon transistors and !Cs; printed circuit boards in European size, accessible from the front; adjustable individual pre-amplifiers for all playback heads, therefore tolerances in playback level and frequency response can be eliminated.

The following tone signals can be given after the spoken text: gonglike sound; continuous note of 0.15 or one 50

second duration; three tone signals at the 8th, 9th and 10th second (only for ZAG-S with one-second control).

Source impedance: :;;;; 1 ohm; a large number of subscribers can be connected to, whereby the necessary crosstalk-attenuation will not be lost.

In order to increase reliability and to ensure continuous operation also in case of maintenance, failure etc., an installation can be equipped with two speaking clocks.

Both the units operate in parallel, namely in synchronism, so that the second unit can take over supply of the announcement at any time.

Time Code Generator (ZMG 300) To indicate the time of day, this equipment uses either Morse code signals, or - as an option - an automatically readable digital code; it is nearly entirely designed to use digital integrated circuits, therefore mechanical maintenance is unnecessary. The construction data have been fixed so that the equipment may be either built-in into the MS 200 Recorder or may be used with a special table-housing as a separate independent unit.

Due to the steadily increasing recording capacity of the Multichannel Magnetic Tape Recording equipment communications, which are spread over several days will have been recorded on one tape if the MS 200 Recorder has been operated in voice-actuated mode. In such cases it will be insufficient to record the exact time of one day only. Therefore, the ZMG 300 may be endowed with an optional item, which allows - apart from the normal time-indication - also the indication of day and month (even considering a leap year).

Using the standard version of the ZMG 300, the time-signal will be announced every 10 seconds (six times per minute).

When additionally using the optional item for indicating day and month you will receive a time-signal every 20 seconds (three times per minute).

Synchronisation of the ZMG-300 may be done in three ways: (1) By mains-frequency: the accuracy therefore is dependent directly on the constancy of the mains-frequency; (2) By pulses of an external master-clock: in this case you may use contacts or voltage pulses between 2 and 60 volts as well as second- or minute pulses; or (3) By an internal crystal oscillator with a permissible deviation of maximum 1 x 10-6.

The time-signal information at the signal-output of the ZMG-300 is indicated at the same time on the front-panel by means of gallium diodes. The initial adjustment is done by means of a selector-switch, which allows a synchronising of the Time-Code Generator ZMG-300 with an accuracy of one second. It is also from the front-panel, where you may adjust the speed of the Morse-code generator.

When using the ZMG-300 with date-indication, you may - by means of a toggle switch - adjust whenever the current year has 365 days or 366 days (leap year). The further switching corresponding to the relative length of the month is done automatically by the ZMG-300 itself.

In case of mains-failure, any time-information as well as the switching of the time-pulses are stored for at least 12 hours by means of a built-in Ni-Cd-accumulator. During the time of mains-failure there is no optical indication and no output of the Morse-code signal.

Preparations are in hand to make available a corresponding Time-Code Generator, which will indicate the time by means of a digital readable code.

Readers who would like to receive further information regarding the company's products, are kindly requested to address their queries to the following address: ASSMANN GMBH, D-6380 Bad Homburg v. d. H. 1, lndustriestraf3e 5, Federal Republic of Germany, Tel.: (06172) 106-1, Telex: 0415158, Cable: Akustik.

husband and wife are doing shift work on different timetables.

The effects of shift work on social life in general are in some ways even harder to accomodate. Irregular free time threatens the worker's relationship with his friends and more distant relatives. Moreover, abnormal hours make it difficult to use mass entertainment facilities timed to suit normal working hours. /.\voiding discontent

Book Review Shift Work and its Human Cost* Shift work is one of the features of modern industrial life. It involves many workers, including air traffic controllers, and sometimes it has harmful effects. The ILO has published a study of shift work written by Marc Maurice, chief of research at the French National Centre for Scientific Research (CNRS).

Starting in a few sectors with special technical requirements, such as steelworks with continuously burning furnaces, shiftwork has gradually spread to many other parts of industry and commerce. When factories begin working 24 hours a day, whether in response to increasing demand or to make maximum use of plant, other sectors such as communications, transport, power supply and health services are bound to fall into line. And so a new way m' dividing time is born. It is related neither to the natural biological rhythms of the human being, nor to the sequence of night and day, or to the customary alternation of a working week followed by a weekly rest period.

The consequences for the worker may take the form of disturbances affecting such biological functions as nutrition and sleep.

Studies of shift work make it possible to outline the physical effects of varying hours of work. Mr. Maurice observes that disorders related to shift work are often of psychosomatic origin. For example, there have been cases of men who developed stomach ulcers, feeling trapped by the circumstances of their lives. Certain workers, in fact, have no alternative to shift work other than unemployment, or at best a sharp drop in earnings. In other cases a combination of disorders such as disturbed sleep and digestive functions can cause workers increasing difficulty.

Doctors, physiologists, psychiatrists and sociologists do not always agree in their research and in the interpretation of the results obtained from it. They do, however, agree that the harm caused by shift work is basically due to disturbance of those bodily functions which are related to daily rhythms.

When someone takes up continuous shift work he often feels that he is no longer leading a normal existence; that he is cut off from his fellow men.

Studies indicate a progression in the types of disorder experienced by workers. The constraints, in diminishing order, are those on family life, then on spare-time activity, then on social relationships. Most studies agree that shift work, particularly where there is night duty, disturbs family life, whether in the organisation of the household, in relationships between members of the family, in the conjugal relationship or in the role of the father in his children's education. Family tensions increase considerably when

The regulation of shift work poses problems with which national laws may deal directly or indirectly. Collective agreements are important here, because workers are more inclined to accept shift work if they have been consulted about it, and if they take part in arranging the practical details.

Hours of work, night work, wages and rest are also the subject of many standards set by the International Labour Organisation, whether in the form of international Conventions or of conclusions adopted by the various ILO Industrial Committees. ( • Shift Work: Economic benefits and social costs, ILO, Geneva, 1974.)

Cont. from page 20: Canadian ASDE Parameters Frequency Band 24.25 to 24.75 GHz Antenna Antenna Gain: 42.5 db Horizontal Beamwidth: 0.3 Vertical Coverage: Inverted CSC 2 to - 15 ° Polarization: Circular Integrated Cancellated Ratio: 20 db Rotation Rate: 200 RPM Radome Type: Fiberglass (¼ ), thickness) Antenna Size: 9.84 ft. wide x 2.62 ft. high Radome Diameter: 14.8 ft.

°

>

Transmitter Peak Power: 30 KW Pulse Length: 20 nanoseconds Pulse Repetition Frequency: 14,000 pps Tube Type: Varian inverted coaxial magnetron (315) Modulator Type: Hard tube Receiver Noise Figure: < 13 db (system) i-f Bandwidth: 100 MHz centered at 160 MHz Local Oscillator Type: Diode oscillator Sensitivity Time Control Fast Time Control > provided Display Type High resolution TV type bright display 16" diameter Antanna/pedestal/radome assembly weight < 2,000 lbs.

MTBF (calculated) 1,100 hours Range performance (calculated) 3 M 2 at 10,000 ft. for precipitation rate of 8 mm/hr.

(CATCA Journal)

51

Corporation Members of the InternationalFederation of Air Traffic Controllers'Associations AEG-Telefunken, Ulm/Donau, Germany Air Vision Industries, Inc., Montreal, Canada ASSMANN GMBH, Bad Homburg v. d. H., Germany CAE Electronics Ltd., Montreal, Quebec, Canada Cossor Radar and Electronics Limited, Harlow, England Dansk lmpulsfysik A. S., Holte, Denmark Ferranti Limited, Bracknell, Berks., England Glen A. Gilbert & Associates, Washington D. C., U.S.A. Ground Aid Group, Esbjerg, Denmark International Air Carrier Association Geneva, Switzerland International Aeradio Limited, Southall, Middlesex, England Jeppesen & Co. GmbH., Frankfurt, Germany Lockheed Electronics Company, Inc., Plainfield, N. J., U.S.A. The,Marconi Radar Systems Limited, Chelmsford, Essex, England N. V. Hollandse Signaalapparaten, Hengelo, Netherlands The Plessey Company Limited, Weybridge, Surrey, England Racal-Thermionic Limited, Southampton, England Selenia - lndustrie Elettroniche Associate S. p. A. Rome, Italy Software Sciences Ltd., Farnborough, Hampshire, England Space Research Corporation, Inc. Quebec, Canada The Solartron Electronic Group Limited, Farnborough, Hants., England Stansaab Elektronik AB, Jarfalla, Sweden Thomson - CSF, Paris, France The International Federation of Air Traffic Controllers' Associations would like to invite all corporations, organizations, and institutions interested in and concerned with the maintenance and promotion of safety in air traffic to join their organization as Corporation Members.

Corporation Members support the aims of the Federation by supplying the Federation with technical information and by means of an annual subscription. The Federation's international journal "The Controller" is offered as a platform for the discussion of technical and procedural developments in the field of air traffic control.

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selenia airport and • traffic control systems air

Selenia offers advanced equipment for Air Traffic Control including: • RADARS • BROAD BAND AND NARROW BAND LINKS • DIGITAL DISPLAY SUBSYSTEMS • COMPUTERS • PRIMARY AND SECONDARY RADAR EXTRACTORS • SIMULATORS AND DIGITAL INTERFACE EQUIPMENT • AUTOMATED AIRPORT SUBSYSTEMS as well as • COMPLETE AIRPORT TURN-KEY PROJECTS

iogether with wide experience in: • SYSTEM DESIGN • SYSTEM IMPLEMENTATION AND INTEGRATION • LOGISTIC SUPPORT

INDUSTRIE ELETTRONICHE ASSOCIATE SpA. CIVIL RADAR AND SYSTEMS DIVISION Via Tiburllna Km 12.400 - 00131 Rome, Italy Cables: Selen ia Roma Telex: 61106 Selenlat Phone: 43601

A new A.T.C.system from T-VT

Aircat Automated integrated radar control for air traffic