IFATCA The Controller - October/November 1966 by IFATCA

IFATCA JOURNAL OF AIR TRAFFIC CONTROL

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z Determinants of Our Air Traffic Control Systems: Improved Equipment Performance Redevelopments Toward Future Requirements TE LE FUNKE N developed a new Precision Approach Radar System improving the range coverage from 10 NM to 12 NM. The transmitter power was increased and the receiver sensi tivity improved. The elevation reflector provides coverage in the azimuth plane by way of cosecant-squared pattern s on both sides. Upon request, the radar system can be fitted with less co mpl ex reflectors. The new indicator consoles have 16-inch display tubes for the 4-NM and 12-NM ranges. We supply further: Radar systems for airway surve illance ; radar systems for airport survei llance; radar remoting systems; data processing systems; data transmission systems.

Please add ress enquiries to TELEFUNKEN Engineering Equipment Group Export Department 79 ULM (Donau) Germany

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Corporation Members

of the International Federation of Air Traffic Controllers' Associations The Air Traffic Control Association, Washington D. C., U.S.A. Cessor Radar and Electronics Limited, Harlow, England The Decca Navigator Company Limited, London ELLIOTT Brothers (London) Limited Borehamwood, Herts., England IBM World Trade Europe Corporation, Paris, France ITT Europe Corporation, Brussels, Belgium Jeppesen & Co. GmbH, Frankfurt, Germany The Marconi Company Limited Radar Division Chelmsford, Essex, England N.V. Hollandse Signaalapparaten Hengelo, Netherlands N. V. Philips Telecommunicatie lndustrie Hilversum, Holland Selenia - lndustrie Elettroniche Associate S. p.A. Rome, Italy The Solartron Electronic Group, Ltd. Farnborough, Honts., England Telefunken AG, Ulm/Donau, Germany Texas Instruments Inc., Dallas 22, Texas, USA Whittaker Corporation, North Hollywood, California, USA

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.

TYPE 1500 MILITARY/CIVIL TRANSPONDER The simultaneous use of common airspace by civil and military aircraft intensifies the critical necess ity for more efficient A .T.C. systems. Secondary Surveillance Radar provides this improvement. Civil Aircraft fitted with transponders already benefit from the advantages of such a system, as do the ground control stations. Military aircraft can now flt transistorised transponders embracing the entire rang e of performance features for operation in any A.T.C. Secondary Radar area in the world . The Cossor SSR.1500 t ransponder is designed to meet the divers requirements inherent in civil and military operations. The equipment reliability is extraordinarily high; yet the transponder is designed for continuous operation at temperatures up to +140 째C and altitudes up to 100,000 ft. It is extremely compact, weigh in g only 27 lbs, yet incorporates all military and civ i l modes (1, 2, 3/ A , B, C and D), and functions in 2 and 3 pulse side-lobe suppression environments. The small s ize is achi eved by unusually high component density; whilst retaining sufficient flexibility and accessibility for rapid maintenance. The SSR.1500 compli es with the requirements of Annex CCB. to 29/69 CANU KUS (military), l.C. A .O . Annex 10, and relevant sections of Arinc characteristic 5320.

IFATCA JOURNAL OF AIR TRAFFIC CONTROL

THE CONTROLLER Volume 5 · No. 4

Frankfurt am Main, October/November 1966

Publisher: International Federation of Air Traffic Controllers' Associations, 40 Park House Gardens, East Twickenham, Middlesex, England. Officers of IFATCA: L. N. Tekstra, President; G. W. Monk, Executive Secretary; Maurice Cerf, First Vice President; Roger Sadet, Second Vice-President; Herbert Brandstetter, Hon. Secretary; Bernhard Ruthy, Treasurer; Wolter Endlich, Editor. Editor: Walter H. Endlich, 3, rue Roosendael, Bruxelles-Forest, Belgique Telephone: 456248 Production and Advertising Sales Office: W.Kromer&Co., 6 Frankfurt am Main NO 14, Bornheimer Landwehr 570, Phone 434325, 492169, Postscheck Frankfurt (M) 11727. Rote Card Nr. 2. Printed by: W.Kromer&Co., 6 Frankfurt am Main NO 14, Bornheimer Landwehr 570. Subscription Role: OM 8,- per annum (in Germany). Contributors ore 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 mode and opinions expressed, it does only accept responsibility for publishing these contributions. Contributions ore welcome as ore comments and criticism. No payment can be made for manuscripts submilled 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 reprinting any part of this Journal.

CONTENTS

ATC Highlights of the lowan ION Meeting ............... .

by Tirey K. Vickers

Sixth Convention of the U. K. Guild of Air Traffic Control Officers ............................ · · · · · · · · · · · · · · · · · · · ·

The ARSR Weather Surveillance System

by T. J. Simpson

.............. · · · · · · · ·

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Austrian Controllers visit Budapest Wake Turbulence

IFATCA Annual Conference 1967

Laying of the Foundation Stone of the Eurocontrol Upper Area Control Centre at Beek-Maastricht Airport ......... .

The S.R.T. Daylight Display System for ATC . . . . . . . . . . . . . . . .

by S. Skaraeus Advertisers in this Issue: Cossor Electronics Ltd. (2); The Decca Navigator Company Ltd. (Bock Cover); Dr.Ing. Hell (12); Marconi Company Ltd. (7, 8); N. V. Hollands Signaalapparaten (17); Plessey Electronics Group (13); Selenio S.p.A. (Inside Bock Cover); Telefunken AG (Back Cover). Picture Credit: Brandstetter (12); Eurocontrol (22); Federal Aviation Agency (9, 10, 11, 14, 15); Geneva Tourist Centre (19); SEL (5); SRT (24, 25); Vickers (4, 5).

International Symposium on Civil Aviation Safety

by Roger J. Sadet

The Problem of Air Traffic Control

by Roger J. Sad et

Letters to the Editor ...................... .

IFATCA Addresses and Officers ..

ATC Highlights of the lowan 1.0.N. Meeting Background

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It was late afternoon, the nicest time of the doy for hedge-hopping, and our United DC-6 flew unusually low across the gently rolling farmlands of eastern Iowa. Perhaps the Captain was interested in sightseeing, for it was the first day of summer and this part of the country was as lush and lovely as we had ever seen it. Velvety green pastures and freshly combed cornfields rolled on and on like the background of a Grant Wood painting. We were on our way to the 22nd Annual Meeting of the Institute of Navigation (ION). The site this year was Cedar Rapids, a quiet little city in the heart of the Iowa corn country. Cedar Rapids is the home of the Collins Radio Company; and Collins was the host for the ION Meeting, which lasted three days and attracted 270 people from 8 different countries. Although the program covered new developments in the entire field of air, marine, and space navigation, the following review covers only those portions which were most closely related to the field of air traffic control.

Human Factors

R = Desired Miss Distance A = Initial Pick-up Point of Intruder Target Note : Assuming constant speed and heading, Intruder must stay out of triangle ABC, in order to provide desired miss distance.

In his paper, "Man and Radar Display", Dr. HansChristian van Freiesleben of the German Hydrographic Institute described recent human-factors research in marine radar operation. The average time required by a large group of operators, to detect a moving target on a marine PPI and determine whether or not it was on a collision course with their own ship, varied approximately as shown in Fig. 1, over a four-hour watch period. If the results of this program can be applied to air traffic control, they would indicate that a controller is sharpest when he first sits down at a radar scope, and that his efficiency gradually declines over an extended period; however, partial but temporary recoveries may be expected around the 11/i hour mark and again at 3 1/2 hours. The moral to this story appears to be that personnel should be rotated to other jobs, or at least given a short recess, after a couple of hours of continuous duty at a radar scope.

Collision Avoidance

Fig. 2

Collision Avoidance Concept

In a paper "Marine Radar Collision Avoidance", Floyd Scripture of Raytheon described the requirements of an automatic alarm system to worn of targets on a possible collision course with one's own ship. Applying some of his concepts to the operation of on airborne collision avoidance system (CAS) that would display target range and bearing information, we find that the relative bearing of an intruder must change continuously with range, as shown in Fig. 2, in order to provide an adequate miss distance (such as 3 miles, for example) . It is also fairly obvious that the higher the closing speed, the greater the initial target detection range needs to be. Speaking of automatic CAS equipment, Mr. Scripture expressed the interesting viewpoint that a few false alarms ore healthy for the system, in order to keep the operator alert and to show him that the equipment is working.

La nding Instrumentation As a part of the ION program, we were taken through the factories of Coll ins Radio. One of the most interesting demonstrations they showed us was a flight simulation of their latest Flight Director System, which is designed to permit manual approaches down to Cate gory 3 lim its. With th is type of instrumentation, interceptions of the ILS localizer and glide slope con be made smoothly, without overshooting the cente r lines. ATC controllers at airports which have parallel ILS approach procedures will appreciate this feature. We were a lso impressed with another feature of the Collins system - an a utomatic flareout command which is initiated by a radio altimeter, as the aircaft approa ches the runway surface. Incidentally, one of the French delegates told us that in his country, a soft, gen tle touchdown is known as a " kiss " landing. Romant ic, yes? But some of our landings only sta rt with a kiss!

SST Radiation Hazard One of the most eminent speakers on the ION program was Dr. Henry Van Allen, one of the real architects of the space age, and the man for whom the Van Allen Radiation Belts a re named. As he probably knows as much about solar radiation as any man alive, we asked him for some off-the-cuff comments regarding the possible radiation hazard which might be associated with higha ltitude SST operations. He said that at 70,000 MS L, over most of the earth's surface, the average radiation level would be equivalent to on ly about 1O milliroentgens per 24 hours, on intensity which he regarded as insignificant. He added that over the polar cops, the intens ity at 70,000 MSL would be several times thi s level, but still insignificant a s far as any haza rdous effects were concerned. At 100,000 MSL, he said, the radiation level would be correspondingly higher. We then asked Dr. Von Allen about the hazard of solar flare conditions. He said that these rare occurrences could produce several times the norma l radiation intensity, but that adequate warning time would be available so tha t SST's could descend to lowe r a ltitude levels if desired. The warning time wou ld vary from 30 minutes to lwo hours, depending o n the type of solar particles involved in the e ruption .

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plined fly ing by the pilots, but provided them with the means for precise navigatio n so that the navigation function cou ld, for the most part, be returned to the cockpit. This concept agrees with the curent views that have been expressed officially by both IFALPA and IFATCA. Mr. Pike emphasized that there is no technical reason why such a system could not permit overtakes with 6000 feet of lateral separation, or slopel ine (profi le) navigation wilh 3000 feet vertica l separat ion between adjacent climb or descent lanes, as shown in Fig . 3. With an ATC system built around these capabi lities woul d be requ ired to deal on ly w: th unus ual situations, and the great mass of aircraft would be navigated from the cockp it, using a pictorial display based on highly accurate pos ition da ta from an advanced navi gation system.

1966 Thurlow Award

Terrain Avoidance E.W. "Ted" Pike, who choired IATA 's Flight Techn ical Group for ten yea rs and is now Director of General Precision, Ltd., pointed out that during th e past seve n years, 718 airl ine passengers and 121 c rew members have been killed in collisions of aircraft w ith the ground, in bad weather. He advocated the modification of present air· borne weat he r radars to provide the capabi lity of detect· ing terrai n obstructions, and tr igge ring off an alarm whenever such intrus:ons are detected within some prese· lec ted distance ahead of the aircraft.

Air Traffic Control Concepts In anothe r paper, "Consequences of Current ATC Trends", Mr. Pike questioned the wisdom of the current ATC policy of p!oc ing more and more o f the navigation responsibi lity on radar contro llers. He pointed out t he ultimate need for a sys tem which required more disci -

Fig . 4

Dr Kramer with the Thurlow Awa rd

The highest honor bestowed by the ION is the Thurlow Award, which is made annually. This year it went to Dr. Ernst Kramer of Germany, in recognition of the many contributions to air navigation which he has made during his long career. Dr. Kramer is credited with the invention of the VOR, the ILS, and the Sonne (Consolan) long-range navigation system. As Dr. Kramer could not be present at Cedar Rapids, the award was received by Dr. Karwath of Lufthansa, for subsequent delivery to Dr. Kramer in Germany.

Clear Air Turbulence (CAT) Dr. Paul Rosenberg, who had chaired the ION/SAE National Meeting on Clear Air Turbulence, which was reviewed in the April l 966 issue of THE CONTROLLER, presented an up-date report on CAT problems. He said that no CAT detection technique or device has yet shown a high enough confidence factor to be used operationally. However, simply because so much still has to be learned about CAT, he feels the current development program is justified; a good CAT sniffer would be an extremely useful research tool, in gathering data which could lead someday to a better understanding of the conditions which generate CAT.

Dr. Rosenberg said that in order to allow for pilot decision time, it is now believed that the desired operational range for a CAT detector should be at least 30 miles for subsonic jets and 150 miles for SST's. He also indicated that people were beginning to get concerned about the public safety hazard which could result from one proposed method of CAT detection - beaming laser energy ahead of the airplane. Proponents of the CO 2 laser claim that emission from this type of device will not cause eye damage if it is viewed through a plexiglass window. Although this type of filter may automatically protect pilots and passengers of other aircraft, it does nothing to protect citizens on the ground. With a laser powerful enough to detect CAT at the ranges specified by Dr. Rosenberg, a slight wobble of the beam below the horizontal could spray large numbers of people on the ground, many miles ahead of the aircraft. Personally, we feel that the use of lasers for CAT detection should be outlawed internationally. Pending any further breakthroughs in CAT research, Dr. Rosenberg advised us of an interim technique which he recommends highly, in coping with the problems of clear air turbulence. For the faithful readers who have followed us this far, we will repeat Dr. Rosenberg's advice in full, below: FASTEN YOUR SEAT BELT!

*** Soxth Convention of the United Kingdom Guild of Air Traffic Centro~ Officers The U. K. Guild of Air Traffic Control Officers held its Sixth Convention in Bournemouth, from 4th to 6th October 1966, under the chairmanship of the Master of the Guild, Mr. L. S. Vass. Two main themes were discussed: "ATC in the Upper Airspace" and "Displays for ATC". On the first theme, the Guild, Eurocontrol, U. K. National Air Traffic Control Services, British Airline Pilots' Association, and the U. K. Guild of Air Pilots and Navigators all presented papers. The fact which seemed to emerge most strongly was the lack of uniformity in the statues of the airspace and the procedures applied, not only in the U. K. and Europe but throughout the world - an additional workload on the airline captain wo has to suffer all the systems, compared with the average controller who is only concerned with one or two. There was an obvious desire to see positive control, on the FAA style, introduced on this side of the Atlantic in place of the existing civil and military ATC systems with their varying amounts of co-ordination. As Captain Taylor of BALPA observed: "If it needs a SUPRAnational organisation to get what is required - let us have it." Papers on Displays for ATC were presented by C. L. Hynam, and E. C. Dyer, on behalf of the Guild of ATCOs; by J. N. Toseland, NATCS; and by V. D. Hopkins, M.A. Psychology Dept. I. A. M. and Dr. G. Castle, Medical Officer i/c ATC Affairs, Board of Trade, who lectured on "Human Factors and ATC Displays". Contributions to the Convention Themes were also presented by Corporate 6

Members of the Guild, who, with others, had exhibits in the conference hall. For many present, the NATCS paper presented by J. N. Toseland was a first opportunity to learn of the first of the types of electronic displays which are envisaged for the later stages of the semi-automated ATCC at London. One hoped that the psychological aspects, outlined by Mr. Hopkin of the I. A. M., would be applied before implementation of future projects and not just used as explanations of why - once again - controllers were working incorrectly designed equipment in inferior conditions. Mr. Eric Dyer made a plea for proper design of equipment for controllers at the non-state airports which are growing in number and in the amount of traffic handled, and suggested that there was on adequate market if all possible users joined together. Many of these airports are handling considerable traffic using the minimum of equipment and manpower and something better than obsolete government surplus equipment is essential. As usual at these occasions, the social functions a Guild Cocktail Party, a Reception and Dance given by the Mayor and Corporation of Bournemouth, plus two official luncheons - gave excellent opportunities for renewing friendships and exchanging experiences and ideas. At an observer's estimate, there were about 200 people present throughout the Convention, and a large number of wives and friends also spent a very pleasant three days in reasonably sunny Bournemouth. FPC

Marconi complete air traffic control data handling and display systems

Broad daylight storage displays Scan conversion bright d isp lays Transistorized PPI displays T rans istorized height dis plays Trans istorized tabular displays Col our projection displays S ynthetic displays Co mposite display consol es Comp uters Radar links Video map generati on

Marconi air traffic control systems The Marconi Compa ny Li mited, Radar Division, Chelmsford, Essex, Eng land

LTD SS2

Marconi AD210C automatic VHF direction finder

IN HIGH DENSITY TRAFFIC AREAS

IN LOW DENSITY TRAFFIC AREAS

VHF OF is an invaluable adjunct to radar f or positive identification of aircraft in high density air space and on b1.1sy airways.

The most useful single, all- weather, ground navigational aid providing air traffic control facilities at low cost and requiring no special equipment to be fitted in aircraft, apart from the basic VHF communication equipment. Easy to operate and maintain.

Push - button se lecti on of five frequencies Automatic presentation of bearings on 8-inch indication meter Facilities for repeater display u nits up to 500 ft from main display a nd control units Remote control up to eight miles from aerial site Small display units, suitable for desk or main control desk mounting Simplified aerial system QDM o r QTE -50 kc/s channel spacing -frequency range: 100-156 Mc/s Bearings and triangulation can be superimposed on Marconi rad ar displ ays

M 路a rconi air traffic control systems The Marconi Com pany Limited, Radar Division, Chelmsford, Essex, England

LTO ISSO

The ARSR Weather Surveillance System by T. J. Simpson Chief, Rodar Systems Section, SRDS Federal Aviation Agency

The Clutter Problem The introduction of radar provided the air traffic controller with one of his most versatile tools, by giving him an "eyeball" view of the air traffic situation. But it also gave him two very special problems - ground clutter and weather clutter - which interfered with the display of aircraft targets and sometimes made the radar useless for ATC. Early radar improvement programs were aimed at eliminating all such extraneous information from the display, under the belief that the ideal radar display would be one which showed only the aircraft targets and the video map, against a perfectly clean, dark background. The cleanup efforts were, generally, quite successful. Improved Moving Target Indicator (MTI) circuitry eliminated all but the most severe ground clutter. Circular Polarization (CP) techniques removed nearly all the weather clutter, though severe storms could still punch through even the best CP. The closest approach to the clean-scope ideal came in the high-altitude control sectors, where all pertinent traffic became transponder-equipped, so the primary radar inputs were turned off. Without primary radar, there could be no ground clutter nor weather clutter to mar the view.

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Soon, however, in this sanitary-scope environment, it was realized that something important was missing. The pilot fraternity began to complain that they were being vectored through severe turbulence and precipitation. To this the controller had to reply that with his clutter protection, he didn't usually see the weather; though with it off, he didn't always see the airplanes.

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In 1964, Dave Atlas of AFCRL suggested a way out of this dilemma. He proposed a method of displaying the location of the weather areas by drawing contours or outlines around them. The contour would show the controller "where the action is" without obliterating the aircraft targets in the vicinity of the weather. To try out this concept, the necessary equipment was designed and installed on the Suitland, Maryland ARSR-1 E radar of the Washington Center. In the ARSR Weather Surveillance System, as diagrammed in Fig. 1, a special polarizer in the antenna feed retrieves the energy of the storm returns, which are rejected by the circular polarizer. The energy is then fed to a separate radar receiver. The receiver output is run through a contour generator, which is simply a threshold detector. During any radar sweep, if the amplitude of this output reaches a preselected threshold level, the con-

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tour generator reads out a single pulse which prints out a dot on the PPI, as hown in Fig. 2. Subsequently, when the amplitude drops through the selected level again, another pulse is read out, painting another dot on the same sweep radial.

Storm video Preselected Threshold Level

Single sweep

Fig . 2 Contour-dot readout from single sweep.

Fig. 3 Two-level contours.

As the radar beam moves in azimuth across th e storm area, e a ch pair of dots along the sweep adds to those previously painted, to outline that portion (or slice) of the sto rm wh ich is showing the preselected level of signal intens ity. As shown in Fig . 3, additional signal thres hold levels can be selected, to outline storm slices which are showing higher or lower intensity levels. All of the threshold levels can be ad justed independently, and ca n be coded to show either solid, dotted, o r dashed outlines.

range of th e Suitland radar. Th e high-altitude display presented aircraft targets only on secondary radar, on a 200-mile range. The operational test program was conducted between July 15 and September 1, 1965. It was found that the usefulness of the contour presentation was limited by problems of ground clutter, anomalous propogation, contour display and interpretation, as described below.

Ground Clutter Test Program The contour system, al so known as t he "weather flx ", was fed to the RBDE-5 displays o f two low-al ti tude secto rs and on e high-al titude sector o f Washington Center. The low-altitude displays presen ted primary (normal and MTI} and secondary (beacon) rador returns, with in a 60-mile

On no rm a l video, the area within 20 miles of th e Suitland radar wa s covered with groun d clutter. To eliminate th is problem, the low-altitude sector di splays were operated with MTI from 0 to 36 miles range; with normal video beyond. Usua lly th e MTI was free of clutter. Howeve r, when the weather channe l was turned on to display wea th er contours, it also generated co ntours arou nd the ground clutter which had previously been invisible. These co ntou rs were objectionable in that they obsc ured targets in the Washington departure handoff area. Th ey a lso merged at times with the wea th er contours, p reventi ng a clear definition of weather areas wi th in the boundary of the ground clutter pattern.

Anamolous Propogation (AP)

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Contoured AP

AP in the Washington area is often due to temperature inversions produced by la rge bodies of water in the vi路 cinity. On normal video, the AP clutter pattern has the some appearance as CP punch-through on th e normal video channel. However, an experienced rada r controller con recognize AP and e limi nate it by use of MTI. When the wea ther chann e l was in operation, it processed the AP returns and presented them in contou red form as on extended ground clutter pattern on all displays. General ly, the AP contours were intricate in design, as shown in Fig. 4. Alone, they were easily recogn iza ble. However, they cluttered the display and mode it impossible to distinguish weather contours during storm activi ty.

Fig. 5 CP Punch.through bordered by contours.

Fig. 6 High altitude sector display showing isolated storms a t left and two-level contouring of large storm area at right.

Contour Display

played ". As far as the pilot is concerned, however, it is better to avoid the ball park altogether than to get tangled up in a rough game. Much work sti l l needs to be done to improve the operation of the contour system. Ground and AP clutter must be eliminated from t he weather chann el, and weather clutter eliminated from the main radar channel. Th e presen t type of con tour circuitry cannot distinguish between weather signa ls and clutter signals, but simply draws lines around al l areas of equal signal strength. Fig. 4 points up the difficulty of determining where the ground clutter leaves off and the weather beg ins. A radar sees a storm only because of the precipitation inside (rain, hail, or sn ow). In the pa st, it has been assumed that the intensity of the reflected signal was a natu ral ind icator of the potential hazard of the storm; the more intense the return, the greater the hazard to air

In the low altitude sectors, whenever storms became severe enough to cause weather signals to get past the protective devices in the main weather channel, the CP punch-through showed up as bright clutter on the displays. Although this clutter cou ld obliterate aircraft targets, controllers cou ld usually vector aircraft around it. Use of the lowest level weather contour in these cases was of little va lu e because th e contour simply fenced in the weathe r echo, as shown in Fig. 5 and was not readily visible. When ~igher-level contou rs were tried, they wer e totally hidden in the most intense portions of CP punch-through area. In the high-altitude secto rs, where controllers normally had no display of weather unless they deliberately introduced primary radar to " burn-in" the storm, the contour techniques proved useful. It eliminated the need for " burn-in ", as well as the annoying afterglow of the clutter. During periods of isolated thunderstorm activity, the contours aided controllers by showing corridors between the elements of the storm formation as shown in Fig. 6. If wide enough, such corridors were often used as vector routes. During storm activities such as frontal passages which covered larg e areas, the entire a rea was enclosed by the c~ntour, which thus failed to show any corridors w hi ch might have existed. Th is pointed up the desirability of having additiona l contours to outline the most intense storm cells. Twalevel contours are shown in Fig. 6. . Co.ntours on ly outlined the areas of equal reflection intensity, and provided no in formation as to the height of the storms.

Contour Interpretation A lth ough the use of contours in l ieu of row weather v ideo sig nificantly reduced the competition between target data and unwanted clutter, it did not provide any better interpretation capabi lities than the raw weather v ideo. As one co ntroll er stated , "I t shows us w here the ball park is, but it doesn 't tell us what kind of game is being

traffic. Recent data shows that this is not necessarily the case, as severe turbulence can be encountered inside, or near, storms whose moisture content is so sma ll as to be hardly visib le to a radar. On the other hand, controllers have traditionally assumed that the intensity of CP punch-through is a measure of storm hazard. Th is is not always true, because ground mirror effects and side lobing can greatly in crease the i ntensity of CP punch-through and thus exaggerate the apparent hazard.

Related Research The FAA hos a continuing contract w ith NSSL, to in vest igate techniques for the detection and diagnosis of aviation weather ha zards . One object of this program is to see whether the radar reflect ivity factor (Ze, the strength of a rada r return from a storm) can be manipulated to determine: (a) w hether a specific storm is hazardous, (b) the location and altitude of t he hazardous portion, and (c) the na ture of the hazard (hai l, turbu lence, etc.). Data indicates that severe convecti ve turbulence may be confined to storms in wh ich cores have a Z,. of 1Qâ&#x20AC;˘ or

higher, though the turbulence is not necessarily limited to the cor e area s. A " hot core " of thi s va lue " flags" the sto rm as possessi ng severe turbulen ce somewhere in its makeup; the exact location cannot be pinpoi nted yet with any degree of accuracy o r consistency. It has also been found that in storms w hich have a Zc of l OS or high er, t here is be tter than a 90% chance of seve re hail; w hen t he Zc foils to 10• or below, ha il encounters are rare and hail diameters are less than '/ • inch.

Th e 1966 NSSL program involves more in strumented penetration flights in conjunction with g round-bosed and airborne radar observations, and makes greater use of computer facilities for data reduction and analys is. Someday the ground-based air traffic controll er may hove the means to determ ine the location, alt itude, severity and nature of any storm hazard, a nd the sa fest fl ight route around it. Until then, avoidance is the best policy.

*** Austrian Controllers visit Budapest During th e pa ssed years a ir tra ffic control lers in many countries hove formed notional ATC associa tions or guilds, wit h the objective of promoting th e air traffic control professio n and to further enh an ce a safe, efficient, and regular flow of air traffic. Most of thes e associations hove jo ined the ir efforts by beco ming members of the Internati onal Federation of Air Traffic Controllers Associations. At the Vienna Co nference, for th e first t ime in IFATCA history, t he Annuol meeting included fellow contro ll ers from Czechoslovakia, Bulgaria, Roumo nio, Yugoslavia, and Hungary. To continue these new relation s, and especially since Yugoslavi a hod applied for IFA TCA membership at t he Annual Conference, the Austrian Air Traffic Contro llers Association was charged to take over the r espo nsibi l ities of a Regional Lia ison Officer. Attempting to smoothen som e prob lems a ris ing out of different rules for th e assignment of flight levels and in order to exchan ge views on other current opera t ional matters, a delegation of Austria n ATCOs recently visite d Budapest, fo llowing on invitation of their H ungarian fellow controllers. The controllers from Budapest ATC sho wed con side rab le interes t in I FATCA. It is hoped that they will be able to attend the Geneva Conference a nd wi l l soon affiliate wi th the Fed erat ion. H. Brandstetter IFATCA Liaison O fficer

The Au strian Delegat ion at Budapest

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Z ETFAX equipm ent grants a ma ximum of sa fety. Di st ingu ished air lines could not imagine th eir working w i tho ut ZETFAX. It is a rel iab le, trustworthy and rapid help for t he air traffic control. - Pl ea se ask for information and references! DR.-ING. RUDOLF HELL · 23 KIEL· GRENZSTR. 1 - 5 ·TELEPHONE: 2011 ·TELEX: 0292858

Plessey AR-1, the most versat ile surveillance radar Plessey A R-1 is a high defini ti on , general pu rpose ai r surveillance radar designed to fulfil all air-traffic cont rol functions w ithin a range of 75 miles. A ll these operat ional roles are carried o ut accu rately, reliably and effectively: T erminal area surveillance/ Approach control/ Radar sequencing control I Parallel r unway appro ach control / O utbo und co ntrol from takeoff I G CA surveillance elemen t / PPI approac hes / Fighter recovery / Low flying local traffic survei llance. The performance of t he AR-1 in these many roles has bee n st ringent ly evaluated b y civi l and mi litary authorities resulting

in over 50 equ ipments being adopted by authorities in all parts of t he world. For full data on the AR-1 or information on the P lessey range of rada rs, displays and data hand li ng equipment w rite to:- Plessey Radar Limited, Davis Road , Chessin gt on, S urrey, England. Tel: 01-509 5222. Telex: 262329

PLESSEY RADAR PLESSEY ELECTRONICS GROUP ~P E( R )33A

Wake Turbulence The article "Living with Vortices" by Tirey K. Vickers, which we published in the January 1965 issue of THE CONTROLLER, was probably the first comprehensive treatise on the subject, specifically written for the air traffic controller and the general aviation pilot. Today, nearly two years after the publication of Mr. Vickers' article, the question of "how to avoid the twist" has not lost any bit of its actuality. In order to bring home to every pilot the dangers arising from vortex generation, the Federal Aviation Agency has embarked on a large scale safety programme. We have in this journal already reported about the excellent FAA film "Turbulent Wake". This is probably one of the

best films ever made by the FAA, and since its European premiere at the 1966 IFATCA Conference in Rome it has been shown to numerous pilot/controller forums in several European states. We have had reports from Maurice Cerf in Paris, Horst Guddat in Frankfurt, and Roger Sadet in Brussels that the Turbulent Wake film has become a smash hit and that it meets with the greatest interest. The FAA have also published a very instructive pamphlet on the same subject: Advisory Circular 90-23 A*, in which the phenomenon of wake turbulence is explained and examples ore given of how to ovoid it. For the benefit of our readers we are reprinting the booklet below, with kind permission of the Federal Aviation Agency.

For years turbulence generated by aircraft was attributed to "prop wash". The "prop wash" behind other aircraft caused some pretty rough rides, "go-arounds", some accidents and was the subject of a lot of "hangar flying". With the advent of the large jet transport and helicopters, the dangers associated with vortex turbulence were greatly emphasized and the so-called "prop wash" problems enlarged to include "jet wash" and helicopter "down wash" turbulence . By this time, however, the problems associated with aircraft wake turbulence had been broken down into two categories - "thrust stream turbulence" and "wing-tip vortices". What was once thought to be "prop wash" was in fact vortex turbulence. "Prop/jet wash", i. e., thrust stream turbulence, can be a hazard to aircraft operating on the ground and pilots should take normal precautions to avoid taxiing closely behind larger aircraft making an engine runup or running up when other smaller aircraft are close behind them, as the case may be. At distances of 400-500 feet "prop" or "jet wash" normally will not constitute a serious hazard to other aircraft operating on the ground. Also, it should not be a hazard to aircraft in flight except possibly in the case of a takeoff or landing in the immediate area of an aircraft making a ground run up. A vortex core is the center of a trailing mass of disturbed air created by the wing of an aircraft as it produces lift. An aircraft creates two such vortices with rotational air movement. As a lift-producing air foil passes through the air it leaves a continuous sheet of unstable air behind the trailing edge. Due to spillage about the wing tips, the air rolls into two distinct vortices, one trailing behind each wing tip. The rollup process is normally complete at a distance equal to about two to four times the wing or rotor span of the aircraft - about 200 to 600 feet behind Copies moy be obtain ed from Federal Aviation Agency Europe, Africa, and Middle East Region United Stoles Embassy Bruss els , Belgium o r dirr,ct fro m th e FAA Headquarte r s in Washington , D . C. 20553 , U .S.A .

Induced Flow

Figure 1. Example of wing-tip vortices initial formation. (Once formed , vortices extend and may be hazardous for an undetermined distance behind the generating aircraft.)

the aircraft. If visible, formation of the vortex cores would appear approximately as shown in Figure 1. Vortices generated by the rotors of a helicopter are shed and trail along the track behind the aircraft in the same manner as those generated by a fixed wing aircraft. These vortices have the same internal air circulation as those generated by fixed wing aircraft and have the same effect upon other aircraft. When an air foil passes through a mass of air and creates lift, energy proportional to the weight being lifted is transmitted to the mass of air. Generally, the greater the lift, the greater the energy transmitted to the air mass in the form of turbulence. The turbulence is directly related to the weight, wing span, and speed of the aircraft. Its intensity is directly proportional to the weight and inversely proportional to the wing span and speed of the air craft. The heavier and slower the aircraft, the greater the intensity of the air circulation in the vortex cores. Thus,

it can be seen that modern large transport aircraft will create vortices having maximum rotational velocities during takeoff and landing at or near maximum gross weights. There is no current practical knowledge that can be used as a yardstick to accurately measure the period of time vortices will be a hazard to other aircraft. Studies have been conducted and measurements made of the size of vortices and velocity of the air within them up to nearly 3 minutes after passage of large aircraft. Pilots have reported what they believed to be vortex turbulence 5 minutes and more after passage of another aircraft. No practical rule involving a time interval for one aircraft behind another will assure avoidance of the vortices generated by the first. However, other methods of avoiding the hazards associated with aircraft vortices are known and can be applied by pilots.

wind condition until reaching a height equal to approximately one-half the wing span of the generating aircraft. At that point they start to curve outward and spread laterally away from the track of the aircraft. There is one thing that must be remembered, that is - both the vertical and lateral movement of the vortex cores will be affected by and move with the encompassing air mass. A crosswind will displace the vortices from the vertical in their downward travel and affect the lateral rate of travel. A crosswind component of approximately 4 to 6 knots, depending upon the lateral rate of vortex travel, is sufficient to cause one core to remain laterally stationary over a line on the surface while the opposite core will travel at its own lateral rate plus that of the effective crosswind.

"Why should I avoid flying in or through the vortex turbulence behind large aircraft?" is a question that a pilot might ask if accustomed only to the turbulence created by light single- and twin-engine aircraft. Perhaps the best answer, and the most impressive one, is that the aerodynamic forces applied upon the light aircraft by the circulation of air in the vortices and the pilot's attempt to counteract it could result in the airframe design limits being exceeded and possibly structural failure.

4 I

And then there is the pilot who has always been able to control his aircraft through any "prop wash" he has encountered. His excellent ability may mean nothing because the forces he encounters behind a heavily loaded large aircraft could exceed the control capability of his aircraft. A roll, descent, or combination of the two could continue even though full control travel or power is applied. The forces of the air in wing-tip vortices can well exceed the aileron control capability or the climb rate of some aircraft. For those who want figures, the air in a vortex core can produce a roll rate of about 80 degrees per second which is about twice the roll rate capability of some light aircraft when using full aileron deflection. If the light aircraft stayed directly between the center of the vortex cores from a heavy jet transport it could encounter a downward flow of air of about 1,500 feet per minute. A light aircraft with a continued climb capability of 1,000 to 1,200 feet per minute could go only in one direction - down. Caught in such a position the pilot who altered his course could get caught by the roll forces or a combination of downward and roll forces. These forces have been sufficient to cause aircraft to do one or more complete rolls, to force them into the ground and in some instances a combination of the two actions.

' I I I

I I

The best way of avoiding the vortices hazard is to know where they are most likely to be encountered and act accordingly. Since vortices are not formed until lift is produced they will not be generated by an aircraft taking off until just before lift off - at the point where rotation is made. Vortices cease to be generated by a landing aircraft when its wing ceases to produce lift when it has actually landed. However, remember that a large aircraft could have taken off and be out of sight, or landed and be on the ramp and the vortex turbulence could still be present near the runway. Another factor to remember is the vertical and lateral movements of vortices. Vortices generated more than 100 feet above the surface will drop nearly vertically in a no-

GROUND PATH

--+--+

SMALL AIRCRAFT

LARGE AIRCRAFT TAKEOFF at X I LAND at Y

figure 2.

FLIGHT PATH

TAKEOFF'

B, D, C, A

A, C, E, B

Example Takeoff1Landing

LANDING'

D, C, B, A

A. B, E, F

alternative

cou1 ses

action

How to Avoid Wake Turbulence Unfortunately, the best advice is not always the most practical. In the case of vortex turbulence hazards avoidance, to insure 100-percent success would require pilots, particularly those flying relatively smaller aircraft, to refrain from operating in areas where the very large and heavy aircraft regularly operate. It would produce the desired result but would not be practical. The following suggestions are therefore offered on how best to avoid wake turbulence:

you out of the vortices of an aircraft that has just landed, it could place you in the vortices shed by one that took off several minutes before on the same or a parallel runway. (b) Intersecting runways. The precautions to heed when taking off after another aircraft has just landed on an intersecting runway are the same as those for a single or parallel runway. But don't forget the "heavy" that may have taken off from either your runway or the other one within the past several minutes.

General Rule

Traffic Pattern

When it is necessary to operate behind a large heavy aircraft try to remain above the flightpath of that aircraft. Remember that vortices settle toward the surface and also that they are affected by the wind and move with the air mass down to within 100 or so feet from the ground before spreading laterally away from each other and that the wind will continue to affect the vortex cores until dissipation occurs. Because of the infinite number of different circumstances that can exist, it is not practical to establish a set of inflexible rules. Therefore, we have outlined several possible courses of action and included their depiction in the following Figure 2, which, depending upon existing conditions and types of aircraft, pilots may wish to consider .

Don't fly below and behind a large aircraft in the traffic pattern. If practicable, plan your pattern to stay laterally separated from large aircraft by at least several hundred feet. When on the final approach, an above and behind position should keep you clear of the turbulence created by the preceding aircraft.

Takeoff/T akeoff (a) Same or parallel runway. Start the takeoff roll at the end of the runway so that your takeoff will be before the point where the previous aircraft's takeoff was made. Make a normal performance takeoff and climb and you should be behind and above the settling vortices of the preceding aircraft. Don't depend upon the wind to dissipate the vortex core circulation appreciably unless it is 10-15 knots or higher and even then it could take several minutes . Also, remember that the lateral movement of vortices, even in a nowind condition, may place a vortex core over a parallel runway. With a light crosswind one vortex can remain stationary over the ground for some time, or even move upwind, before dissipating to any significant degree. (b) Intersecting runways. If the large aircraft was still on the ground until well past the intersection and your takeoff will permit climb to approximately 100 feet or more before you pass the intersection, you should not encounter either the vortices or any appreciable thrust stream turbulence. Remember the general rule and make certain that you cross above the flightpath of larger aircraft. Also remember that the larger aircraft will probably have a high gross weight at takeoff and thus will generate vortices of maximum intensity. Also, consider the lateral movement of vortices and the possible effect the wind will have upon that movement.

Takeoff/Landing (a) Same or parallel runway. When taking off after another aircraft has just landed, plan to become airborne beyond the point where the other aircraft landed. Remember, while starting takeoff from an intersection may keep 16

Landing/landing The same above and behind position on final approach will place the light aircraft pilot in a good position to touch down beyond the point where a preceding large aircraft landed, length of runway considered. If the runway has a visual approach slope indicator (VASI) system, a flightpath in the "red and white" or with the top bar appearing a bit pink will keep you on or slightly above a normal glide slope. The Airman's Information Manual contains a complete description of the VASI system.

Landing/Takeoff When landing after the takeoff of a large aircraft, make a normal landing near the approach end of the runway and be solidly on the ground before reaching the point where the large aircraft took off. Although vortices from the departing aircraft will not be formed until the point of rotation, remember that the wind can cause the turbulence to move down the runway toward you. When operating in the vicinity of an airport, you may receive an advisory, "CAUTION WAKE TURBULENCE", etc., warning you that it may exist because of an aircraft that recently made a takeoff or landing. When you receive such an advisory, don't hesitate to request further information if you believe it will assist you in analyzing the situation and determining the course of action you wish to take. Remember, even though a clearance for takeoff or landing has been issued, if you believe it safer to wait, use a different runway, or in some other way alter your intended operation, ask the controller for a revised clearance. Sometimes air traffic clearances include use of the word "IMMEDIATE". For example, "CLEARED FOR IMMEDIATE TAKEOFF". In such coses, the word is used for purposes of air traffic separation . The clearance may be refused if you believe another course of action would be better suited to your intended operation. The controller's primary job is to aid in the prevention of collision between aircraft. However, he wil I assist you in any way he can while accomplishing his job.

SATCO

AUTOMATIC AIR TRAFFIC CONTROL SYSTEM

fli g ht p rogr ess c heck

c onflict r esolutio n

CClordinatio n

conflict search

radar, we a pon control, data handling, air traffic control systems N .V. HOLLANDSE SIGNAALAPPARATEN HEN GELO THE NETHERLAN DS

I FATCA Annual Conference 1967 Geneva, 17th - 21st April

The Sixth Annual Conference of the International Federation of Air Traffic Controllers Associations will be held from 17th to 21 st April, at the Geneva Intercontinental Hotel. As the preparations for the Conference are in full swing, it is considered suitable to review the purpose and meaning of IFATCA's annual meetings. One of our fundamental aims as a professional organisation is the advancement of international air traffic control in all its aspects. The Annual Conference constitutes a very useful instrument in the realisation of this objective, indeed it is during this assembly that IFATCA policy is finally established. In addition, the Conference provides an excellent opportunity for the participants to update their knowledge on current ATC matters and to study the latest equipments of IFATCA's Corporation Members. The panel session, which is conducted with the assistance of the Corporation Members on the last day of the Conference, and the exhibition of ATC equipment thus provide a suitable means for exchanging views on technical matters. Cooperation with other aviation organisations, particularly those engaged in air traffic control, is another constitutional aim of the Federation. We are always pleased to flnd among the observers to the Annual Conference representatives of national and international aviation administrations, the International Federation of Airline Pilot's Associations, the airlines, the electronics industry, aviation research institutes, the Air Forces, human engineering specialists and aviation psychologists, IAOPA, and fellow controllers from countries where an ATC association has not yet been founded, or associations which are not yet members of IFATCA. Their wide range of aviation expertise prevents us from working in on ATC vacuum, and the participation of a variety of observers is also an indication of the deep concern that the aviation world shares with air traffic control. Another gesture of recognition of the Federation's efforts is the sponsorship of the Annual Conferences by Municipal and State Authorities. Last, but certainly not least, the Annual Conference is an occasion for meeting socially with those whom we see only once a year. The exchange of ideas on professional matters and comparison of experiences do not stop after the working sessions, but often continue over a friendly glass of beer or during the more formal receptions. The Swiss Air Traffic Controller's Association, being host to the Geneva Conference, will take every effort to provide the machinery for an efficient and successful working meeting and also to organise a number of social events, to make our stay a most pleasant one. On behalf of the Organising Committee, I extend a hearty invitation to attend the 6th Annual Conference of the International Federation of Air Traffic Controllers Associations. The venue of the Conference, Geneva Intercontinental Hotel, is conveniently located (approximately 1 mile from Geneva airport), and there will be special transportation from the airport to the hotel. Geneva is also easily accessible via interstate highways, so that you may even consider travelling by private car. Early spring is a delightful season to visit Switzerland, so don't miss this occasion; and if possible, take your wife with you. There will be a programme of varied activities for the ladies, and you can be assured of a lively and most interesting meeting. Herbert Brandstetter Hon. Secretary, IFATCA

Genevo loke o nd fountoin

Geneva airport and ci ty

Genevo l ntercontincn tol Hotel , venue of th e Conference

laying of the Foundation Stone of the Eurocontrol Upper Area Control Centre at Beek-Maastricht Airport On 4th October the foundation stone for the l st Upper Area Control Centre to be built by EUROCONTROL on the Airport of Beek-Maastricht, in the South of Holland, was laid by Mr. Roy Mason, M. P., Minister of State, Board of Trade of the U. K. and President of the Permanent Commission of EUROCONTROL. This ceremony took place on the same spot where a little over one year ago the land on which the building will be constructed, was officially handed over from the Government of the Netherlands to the former President of the Permanent Commission, Mr. Bertrand, Minister of Communications of Belgium. A number of officials from the seven Member Coun-

tries of EUROCONTROL convened for the ceremony on that wind beaten but glorious morning on the Western part of the Beek Airport, cheered up by a parade concert by the band of the Dutch Air Force. Before the date at which the Centre will be taken into operation is reached, a number of problems will still have to be solved. Of this the organisation is fully aware, but since the date of its Convention in 1960, it has aimed high and has secured the assistance of the highest officials in its Member Countries. Therefore it holds great promise in the achievement of international co-ordination and standardisation in that part of Europe where these are urgently needed for greater safety in air navigation. R. Sadet

*** UAC Maastricht First International Upper Area Control Centre Within the tasks assigned to Eurocontrol notably of providing for the common organisation of air traffic services in the upper airspace of the Member States, this first jointly ftnanced Eurocontrol upper area control centre has been planned to be responsible for a coherent region of approximately 200,000 km 2 (approximately 75,000 sq. miles) formed by the upper airspace of the Netherlands, Belgium and Northern Germany. Free of restrictions imposed by regional frontiers, the UACC Maastricht will render air traffic services to all civil aircraft and part of the military air traffic in its area of responsibility. A considerable proportion of this air traffic wil I comprise aircraft registered outside the three countries whose airspace will be served by the Maastricht Centre. Flying characteristics of modern high-performance aircraft, including supersonic transport, together with an ever increasing density of air traffic in the upper airspace require an air traffic control system employing sophisticated means of col lccting, processing and distributing all kinds of data at the speeds necessary for ensuring the safety of air navigation at all times and under any conditions. The system envisaged for the UAC Centre Maastricht will employ the most recently conceived automated techniques. Primary and secondary radar information, giving the position, height and identity of all aircraft throughout the centre' area of responsibility, is to be extracted from three peripheral radar stations, near Bremen, Amsterdam and Brussels, and transmitted in digital form into the Centre. Similar remoting techniques will be used to maintain constant radar contact with all aircraft in the region, as well as land lines for the exchange of information with neighbouring control centres, plus computer to computer links where appropriate. The controllers will then be presented with a continuously up dated real-time and predicted air situation. T_he requirement of the system to give uninterrupted service 24 hours per day for the life of the centre demands on extremely high built-in reliability of the equipment to be employed. Therefore the equipment to be used, as well 20

as the operational procedures to be employed, will undergo a rigid and extensive evaluation in Eurocontrol's Experimental Centre at Bretigny-sur-Orge near Paris. This evaluation of air traffic control systems and procedures will ensure that neither new techniques nor procedures will be employed until their reliability and efficiency for air traffic control have been proven. The UAC Centre will be located in a building with a volume of approximately 40,000 m 3 and a floor space of approximately 9,000 m 2, which area is functionally divided into operations, technicals and administrative units. The operations unit comprises mainly the operations room and the equipment room. The operations room, which has a floor space of 800 m 2 constitutes the nerve centre of the air traffic control system. It accommodates the air traffic control officers and the telecommunications, radar and other electronic and non-electronic equipment placed at their disposal. The equipment room houses telephone, radio, radar data processing equipment, and is located on the ground floor below the operations room. About 180 air traffic control staff will be working at Maastricht UACC, supported by further maintenance and administrative personnel. All these personnel will mainly be recruited in the countries concerned, namely, Belgium, Germany and the Netherlands. Extensive training will be required for this air traffic control and maintenance personnel, to make them fully familiar with the advanced technology employed. Once Maastricht upper area control centre becomes fully operational in 1972, it will be the ftrst example of an executive unit of the European public service established by the Organisation for the Safety of Air Navigation EUROCONTROL. The creation of this centre also demonstrates the determination of the Member States of EUROCONTROL to realize the main objectives of the EUROCONTROL Convention, signed on l 3th December 1960: strengthening European co-operation for the benefit of air navigation. Reprinted with kind permission of the Eurocontrol Agency

Opeinong Address by Mr. Rene Bulin Director General of Eurocontrol A little over a year ago, on the 11 th of June 1965, on this same spot, Mr. Posthumus, Secretary of State for Transport and Public Works handed over, in the name of the Government of this country, to Mr. Bertrand, Minister of Communications of the Kingdom of Belgium, then President of the Eurocontrol Permanent Commission, the deed placing at the disposition of the Organisation the ground on which we have met today. This was the prelude to o most important European achievement in the field of air traffic control. The stupendous development of air transport created the need to set up centres for controlling traffic in the upper airspace operating over wide areas, unrestricted by the framework of notional frontiers. On such a scale, international co-operation had become indispensable and, it was the resolve of the seven States which form Eurocontrol: the Federal Republic of Germany, Belgium, France, the United Kingdom, Luxembourg, the Netherlands and Ireland, that the first international control centre should be set up here at the crossing of the roads linking the Netherlands, Belgium and the northern part of the Federal Republic of Germany. The new Eurocontrol Centre will directly serve the users of the upper airspace over this extensive area. It is of interest to note the international character of the air traffic concerned. Forecasts for the early 1970s indicate that approximately 50% of this traffic will have been registered in countries not members of Eurocontrol. Of the remaining 50%, that is of the aircraft registered in Eurocontrol countries, - and here is a point which may be of particular interest to you Mr. President - about 250/o will be aircraft of British registration; a further 25% will be registered in the Federal Republic of Germany, 25% in the Netherlands, 12.5% in Belgium and 12.5% in France.

Le Gouvernement neerlandais n'a cesse de poursuivre ses efforts afin de faciliter, dons toute la mesure du possible, l'instollation du Centre sur cet emplacement de !'aerodrome de Beek-Maastricht. Nous lui en sommes tres reconnaissonts et sommes heureux de constater que les Etats membres de !'Organisation cooperent activement lo reussite de cette oeuvre collective qui s'inscrit dons le cadre nouveau des grondes realisations communautaires en Europe. Sans aucun doute, les moyens electroniques les plus modernes de traitement de !'information qui seront mis en oeuvre dons ce Centre, le premier du genre, accroltront encore l'efficacite du contr61e de lo circulation d'avions ayant une capacite de plus en plus grande et une vitesse de plus en plus elevee, qui deviendra meme iargement supersonique pour les plus rapides d'entre-eux. Augmenter cette efficacite, c'est augmenter la securite et la vitesse d'ecoulement des mouvements aeriens qui est la raison d'etre de la Convention internationale du 13 decembre 1960 par laquelle Eurocontrol a ete institue. Aussi, l'Agence prend-elle toutes les dispositions afin que la mise en service du Centre soit aussi proche que possible. Le Centre de Beek-Maastricht sera done !'expression de la cooperation au sein de notre communaute, cooperation qui s'etend egalement a l'industrie de nos sept Pays membres. We are very honoured to have in our midst Mr. Roy Mason, Minister of State responsible for Civil Aviation in the United Kingdom, who, since July 1966, has assured the office of President of the Eurocontrol Permanent Commission of Ministers. On behalf of all here present, I welcome him on this European site and I would like to ask him to lay the foundation stone on which will be raised the important edifice of the first new Eurocontrol Centre.

*** Inaugural Speech by Mr. Roy Mason, M. P. Minister of State, Board of Trade and President of the Permanent Commission As my first official duty as President of the Permanent Commission of Eurocontrol I am very honoured and pleased to welcome you here today on this part of the Beek-Maastricht aerodrome which the government of the Netherlands has graciously placed at the disposition of the European Organisation for the Safety of Air Navigation. Thanks to this gift it will be possible to hove on Upper Airspace Control Centre, situated at the cross-roads of the Netherlands, Begium and the Northern part of the Federal Republic of Germany, the first such European Centre to be set up by a community of sl路ates. Furthermore, this Centre will be operated by staff of several nationalities working to uniform control procedures laid down by an international organisation. Thus Eurocontrol is moving towards a major achievement, in taking account of the increase in the volume and speed of air traffic, and the improvement of techniques , over a large area of Europe.

This, indeed, is further important evidence of a Europe in which the spirit of common endeavour and achievement is growing stronger every day. The site for the Centre is, I feel, particularly appropriate in that, apart from the technical advantages it offers over other possible sites it is only a stones throw away from the highest point of the Netherlands, Drielandenpunt, which commands a view over the dutch, belgian and german countrysides . Telecommunication lines cutting across these three territories will bring information to the Beek-Maastricht Centre from three radar installations which are to be located in this international region, one at Brussels, one at Bremen and one in the heart of the Netherlands. In addition, through a network of very high-frequency radio telephone stations, aircraft flying in the upper airspace will be able to remain in permanent contact with the Beek-Moastricht Centre whatever their position 111 the re-

M i n ister of State Roy Moson (middle) loying founda t ion stone of Moastricht UAC; assisted by Euracontrol Director General Rene Bulin (left) and Mr. P. Nottet, Directo r of Belgian Administration de l'Ae ron autique (right) .

gion. From it they will rece ive the necess ary instructions and information which will protect them from the risks of collision and wil l ensure o rapid and regular flow of traffic w h ile flying at speeds approaching that of sound and, in o few yeors time, even surpassing it. In this area measuring about 200,000 square kilometers the new Centre will not only ensure the safety of traffic on 35,000 kms of air routes but also of traffic flying off these routes. There wi l l therefore be very close co-ordination between the Beek-Moastricht Centre and the services responsible for controlling military aircraft. To be able to fulfil all these tasks, it is estima ted that the Centre will employ 180 specia l ised controllers operating in 4 sectors. With the electronics engineers maintaining the eq uipments in peak working order and t he officials handling the administrative work, th e total number of posts to be filled in the Beek-Maostricht Centre wil l be about 300, so that including families , over a thousand people will be making their homes at the cross-roods of three differen t nationalities. I feel that they stand to gain much from such on enriching experience. The main building to be erected on thi s site wi l l be in the shape of th e letter T, comprising a block measuring 40 metres by 25 and o wing measuring 70 metres by 12. It wi ll not be a high bu ilding, hardly more than fifteen metres, for although there is ample surface area available on the site, we ore building o n on aerodrome subject to he ight restrictions. The block wil l house the operatio ns room : this wil l cover on area of 800 sq. metres, which could, if required , be considerably exten ded without difficulty. The controllers working there will sit at co nsoles containing the most advanced types of control facilities available 1 and below them, in on extension technical room, will be insto lled oi l the requisite basic and sup porti ng equipment. The block 22

wi ll be air condit ioned both to ensure the best working conditions for the staff and because th is is essential for the operation of the soph isticated electronic equipment, which is highly se nsitive to changes in temperature and humidity. The 70 metre wing wi ll contain not only oil the administrative services but wi ll also house various ancillary installations such as class-rooms, con ference rooms, canteen facilities, and so on. All the e lectronics equipment in the Beek-Moostricht Centre wi ll be designed to permit, eventual ly, the highest d egree of automation. There ore still many preparatory studies to be carried out in this connection. Eurocontrol hos on Experimental Centre already at Bret igny-sur-Orge, south of Paris, which I visited recently, whe re the installa tion of on ATC simu lator which wil l be one o f th e most powerful in the world is nearing completion. It wi ll hove on important port to ploy in developing the operationa l techniques for the Beek-Moostricht Centre and will undoubtedly contribute considerably towards advancing the dote of th e Centres entry into service. This is o major pro ject, on w hich there is still mu ch work to be done. However, we con hove every confidence in M . Bu lin, Director General of Eurocontrol, who hos consistently shown remarkable energy under oil circumstances, and I believe therefore that we shou ld continue to adhere to the most optimi stic dote, the year 1971. Befo re concluding, I should to express the Organisation's thanks both to the services of the Netherlands ministerial administration and to the authorities of the province of Limburg and the towns of Moo stricht and Beek, who hove been of such great assistance in preparing th is ceremony. I now have great pleasure in laying the foundation stone of the first Eurocontrol Air Troffic Control Centre.

The S. R. T. Daylight Display System for ATC by S. Skaraeus Standard Radio & Telefon AB, Sweden

Background In todays Air Traffic Control system concept a radar display is used mainly for monitoring purposes. The displayed radar picture on the PPI consists of blips which are built up from several hits on the target and integrated in the phosphor coating of the CRT screen. As each blip is only painted once per antenna revolution and the storage effect of the screen is poor, the light output from the blip exceeds normal ambient illumination only during a fraction of a second. During the rest of the antenna revolution time the radar controller has to watch the afterglow of the blip. As a consequence the radar screen has to be observed in a practically dark room in order to get good contrast on the screen. These ambient conditions increase the psychological loading on the controller. Therefore, a display with greatly improved brightness capable of being viewed in daylight is required. A modern Air Traffic Control system requires data handling in various forms including alpha-numeric tags associated with each radar blip. In high traffic density areas the output from the data handling system will probably be presented on synthetic PPI displays. Aircraft will be indicated by plots with identity and flight level shown as alpha-numeric characters. As these data are computer derived with a rather high repetition rate, a conventional PPI display gives sufficient high brightness. But for many reasons it must be possible to present on the same screen raw radar information and thus we are back at the basic problem - to achieve a bright display for radar information. The conventional PPI where a CRT with a fluoride phosphor coated screen is used, has by far the best defln ition of any type of display. It is capable of great flexibility and is well suited to both raw radar and computergenerated data presentorion at low cost. The problem is to make it brighter (the afterglow of a radar blip is in the order of 1 to 2 ft. lamberts but ought to be 50 to 75 ft. lamberts). If this could be made there is no doubt that the conventional PPI would supersede other bright display systems . In the past, various bright display techniques have been suggested. Some success was achieved by using a television camera equipped with a special vidicon tube. The camera was pointed at a radar display and the picture obtained presented on television monitors. However, the system showed certain drawbacks due to insufficient resolution. Far better results were obtained when a special scan conversion tube was introduced. This system is fairly simple if only raw radar information is to be displayed. Television monitors can be used even if the resolution is not as good as on a conventional PPI. The brightness is good enough for use in a moderately lit room. However, it is difficult to achieve flexibility. The monitors connected to one scan converter are obliged to display the same

range, degree of off-centring and signal content. In a concept where monitors with different presentation are demanded one scan converter is required for each monitor position. The system is further complicated when data handling is introduced, which results in a considerable degree of complexity at the same time as difficulties arise when a high accuracy has to be maintained in order to display alpha-numeric characters correctly. An interesting approach to the bright display problem is the development of the direct-view storage tube since this type of tube provides a brightness level that would satisfy the requirement. Many problems are associated with these type of tubes and their manufacture. Especially larger tubes (16" and above) which are required for most ATC applications show a resolution, which is not satisfactory. Moreover, the application of data handling leads to complex circuits in order to avoid smearing of the screen when alpha-numeric characters are presented.

Obiectives In a modern ATC system it is a demand to establish each sector according to operational requirements. Thus, the radars must be located at right geographical sites in order to obtain the required coverage. The present system for transmission of radar data - primary and secondcry - with the broadband microwave link can be very expensive. The introduction of digital techniques offers a unique advantage to handle the radar information content over telephone lines. At the ATC the information is received as plots which are in a suitable form for presentation on conventional fixed coil PPI (Random plot presentation). A single PPI can at the same time accomodate plots from more than one radar thus giving a composite display which offers the traffic controller the required radar coverage. Digital technique is also used in the ATC for flight plan calculation including correlation and updating with radar track data . Data derived from the computer can be displayed on the same PPI as mentioned above. Thus digital technique is involved in the ATC field to a great extent and in the Standard Radio & Telefon AB (SRT) development it has been a logical step to utilize this technique by adding necessary units to achieve daylight presentation on a conventional PPI with its original type of CRT. This approach also gives the reature that, if the special daylight presentation device fails , the controller can still continue his duty and observe the PPI but under darkroom conditions. The SRT system also includes the possibility of presenting under daylight conditions an electronic map of very good quality. By adding a conventional two track audio tape recorder all radar data can be recorded and used ot later ploy-back for investigation and training .

Basis Principle of the System The basic principle of the SRT Daylight Display System is that the radar video signals are passed through a data processor (video correlator). Output data from the processor in the form of target plots are stored in a ferrite core memory. The contents of this memory are scanned at a high repetition frequency and fed to the PPI. As this frequency is much higher than the normal radar presentation frequency, which is in the order of 1/ , c/s, a high brightness is achieved, suitable for daylight presentation . In a system concept for a sector within an ACC let us assume that the radar coverage is formed by two remote radars and one local radar. As mentioned above, narrow bond transmission is used to bring radar data in to the sector from the remote radars. We will then hove a layout as indicated in figure 1. At each radar site a video correlator is situated which processes the radar video signal. First of all the signal has to pass a threshold circuit to get rid of all noise, after which it is digitized. The following data process can be formulated as a method where the air space scanned by the radar is divided into a number of "windows" projected on a horizontal plane through the radar station. Each window has a length which is equal to a quanta received by dividing the radial range as seen from the radar site into small parts, the size of which corresponds to the radar transmitter pulse length. The width of a window corresponds to an angular increment of the same order as the radar antenna beam width. For each transmitted radar pulse the received video signals within op-

RADAR

SITE A

,-- - - · -

I CENTRE

proriate windows are stored separately in a ferrite core memory. With special logic circuits the stored information is examined as the radar antenna sweeps over a target and compared with correlation criteria. . '.hese criteria are set up to accept signals only from distinct targets thus removing signals from unwanted targets such as clutter etc. In other words, by extraction of wonted signals from the signal content delivered by the radar receiver a reduction of the necessary bandwidth is achieved. The extracted data can then be adequately handled over telephone lines. A buffer unit may be inserted to adapt the data flow to the line capacity. For the local radar similar equipment as described above is used . We have now radar plots which can be displayed on a conventional PPI either as originated from one radar or after passing a display combiner as interlaced from all radars (composite picture). The PPI has to be observed in darkroom condition. The Daylight Rack takes care of all radar plots and through address circuits they. ~re w~itten int~ a ~errite core memory. For each plot add1t1onal information 1s stored to determine the age of the plot. The memory in the Daylight Rack is scanned continuously at a rote of about 16 times per second, and the output is coupled to the PPI. The information of the plot's age is used to control a video logic circuit to generate video signals with different amplitudes. As seen from figure 1, the traffic controller is provided with a switch by means of which he can select at will between presentation in darkroom or in daylight.

~ -

~-~ - ~ · - ·

-·-·--· -

RADAR (LOCAL) VIDEO CORR.

NARROW BAND

--1r~ BAND RX

NARROW

DISPLAY ,_ __.. COMBINER

1--4--i

DAYLIGHT TAPE RACK i----• READER

MAP

I RADAR

SITE B

INFO

I I DAYLIGHT COMPOSITE

I ciO

NARROW BAND TX

NARROW BAND

COMPOSITE ) LOCAL RADAR DARK RADAR A ROOM RADAR

RX MODE

OF OPERATION

Fig. 1 Layout of ACC w1·1h SRT Doyl1ght . . Display System .

CONVENTIONAL FIXED COIL PPI WITH FLUORIDE PHOSPHOR CRT

Operational conditions It is wel l known that the radar video contains many signals from obstacles etc. close to the radar head, depending upon its siting. The correlation criteria in the video correlator must for severa l reasons be set within rather great tolerances, which results in the possibility for certain obstacle signa ls to pass through the correlator. In order not to overload th e memory in the Daylight Rack, it is organized in such a way that the air space covered by the radar is divided into two parts, an inner zone ond an outer zone. The radius of the inner zone depends upon the ground clutter area for the radar in question. In the inner zone all echoes are presented as plots with a flickerfree frequency during three antenna revolu tions. In the outer zone all echoes from a maximum of 30 antenna revo lutions are presented as plots with a flicker-free frequency. The brightness of the two latest plots is higher than that of the older plots, wh ich is guided from the stored age. Thus eoch target forms a trail with the two latest plots being the brightest and the others the fointest. To further emphasize the heading of the trail, a pulse is used to brighten the plots from the oldest to the latest plot in sequence in o cycle of approximately two seconds. It is also possible to switch for a 路presentation of only 16 plots for all echoes. If the capacity of the outer zone is almost fully utilized due to a large number of echoes, the trails of the targets wil l automatically be shortened in order to allow for presentation of all targets. In the inner zone the oldest targets will be cleared from the memory when the number of targets in this zone is rea ching the maximum value. If the radar is equipped with MTI it may be possible to reduce the radius of the inner zone a great extent, thus allowing most of the area to be displayed as an outer zone.

Map presentation It is obvious that the traffic controller must have a geographical reference when studying the PPI picture. Normall y an electro-optica l device is used but as it has a slow data renewal rate (the same as the revolution of the radar antenna) its displayed brightness is not always sufficient for daylight conditions. A sim ilar technique as described above can be utilized for presentation of a bright electronic map. The map or var iou s geometrical configurations (airways, symbols, reference points) to be displayed can be expressed in a number of coordinates (x and y) in digital form. The coordinotes for a contour or lin e con then be converted to a footpoint togeth er with incremen ts which gives the direction of a vector w ith a smal l fixed length. This data (footpoint and increments) can be recorded on a tape for feed ing to the memory in the Daylight Rack wi th a tape reader. When the stored data are scanned at a high rate and fed to the PPI a footpoint is handled as a radar echo plot. The increments gear the electronic beam in the CRT from the painted plot and by adding several increments, a polygonial picture is formed on the PPI screen. The traffic control ler is offered a mop presentation which can be viewed in daylight conditions. Th e thickness of t he map's lines is independent of selected range on the PPI. W ith

Fig. 2

Daylight p i ctu re of PPI display, photographed under normal amb ien t l ight conditions.

an adress system va riou s informa tion can be displayed at the controller's will. A new map can easily be inserted through the tape reader. Figure 2 shows a daylight picture of a PPI d isplay photographed under normal ambient lighting. On the screen are shown radar plots with tra il s and map information.

Recording of radar data It has been stated above that the output from t he video correlator has an information content suitable for tra nsmision over a telephone line. Thus the required bandwidth is quite low and can be adequately handled by an audio two track (stereo) tape recorder using normal magneti c tape. Each radar plot expressed in digital form is fed in serial form to the r ecorder. In o rder to achieve correct play-back a monitor signal is also recorded o n the second track. Th e r eason for this is that conventional tape recorders show variations in speed from time to time. The monitor signal is used to control t he speed. If a recorder with multiple tracks is used the speech communication can simultaneously be recorded. For play-back the same PPI as discussed above is used.

Conclusions The preceding sections discuss in some detail the design of a bright radar display system. It is obvious that the digital techniques used throughout in the SRT design offer a great deal of flexibility. Together with radar plots, additiona l information d erived from othe r so urces such as SSR (identity and flight level) can be stored. In a more ela borate system the supp lementary information can be used for colour presentation.

An American Airlines Captain reports that he overheard an unusual conversation on an ARTC radio channel the oth er day. We reprin t it below, having changed the flight numbers to protect the innocen t: Controller: " TWA 940, how is the turbulence at FI igh t Level 290? " TWA 940: "As a matter of fact, we are trying to serve dinner, and I just stuck the fork in my nose! " Controller: " Roger . United 722, how is the turbulence at yo ur level? " United 722: " I real ly can 't say. We haven 't eaten yet! "

International Symposium on Civil Aviation Safety

by Roger J. Sadet Second Vice President, IFATCA

On 27-28-29 April 1966, the Swedish Society of Aeronautics organised a symposium on civil aviation safety in Stockholm. The symposium was a tentative meeting towards an organised international co-ordination of the efforts spent in improving safety in civil aviation. Since this is a worldwide problem of utmost complexity involving a variety of technologies and sciences, the host society had thought that a presentation of the many aspects of the activities for an increased safety in aviation would be highly beneficial. The purpose of the symposium was certainly very ambitious and had grouped a large number of specialists in different fields concerned with the main topic. The great merit of the Swedish Society of Aeronautics in organising this meeting has been to have highlighted the necessity for closer international co-ordination in research and development of aviation safety and to have brought together people of various countries who can contribute effectively to better co-operation in achieving the aim. The international attendance represented a wide scope of interests. No less than 26 papers were read by speakers representing international aviation authorities, research institutes, aviation industry, pilots and air traffic controllers. The symposium was subdivided into different sessions: General Aspects on Aviation Safety; Current Research on Aviation Safety; Human Factors; Material Factors; Environmental Factors; Transition from the Subsonic to the Supersonic Civil Aircraft; Lessons learned from Incidents. It is impossible to even briefly summarise all the papers here. The following, however, will give an idea of the quality of the lectures, and the people who gave them. One of the first speakers was Mr. A. Spooner, Chief Operations, Accident Investigations and Airworthiness Section of ICAO. He explained the structure of ICAO and stressed that the organisation gives full possibility to Member States to collaborate and to express their views. He further said that the success of regional plans is compromised by the shortage of funds and skilled personnel. The efforts to make good these shortcomings were described and reference was made to the dedicated work of the Technical Assistance Bureau. The facilitation, legal and economic and statistical Branches of ICAO were also explained . Mention was made that the entire budget for ICAO for 1966 is somewhat less than the cost of one fully equipped modern aircraft. Mr. Arne Aagaard, Asistant Technical Director / IATA described the IATA/ ICAO relationship in respect of th~ development of internationally agreed Standards and Recommended Practices which affect the safety of air trans~~rt operations, as well as the work being done by IATA c irectl.y with Governments, Manufacturers and other International Org an1sa 路 t'ions on all aspects of the overall sofety problem.

Captain Arne Leibing, representing IFALPA, highlighted some significant factors that for long time have caused grave concern within the pilot-population of IFALPA and which have been neglected by authorities and operators for years. The paper indicated the necessity of realistic action to be taken now in view of the tremendous economical investments going on within the air transport industry and the increasing economical influence this industry will have in the future on the world's trade. The paper closed by pointing out that there is no substitute for safety. The following papers were read on aviation safety research: "Aeronautical Research and Development in Support of Civil Aviation Safety" prepared by the Department of Civil Aviation, Commonwealth of Australia and read by H. E. Mr. B. D. Ballard, Ambassador of Austra~ lia to Sweden; "Ensuring Flight Safety in USSR Civil Aviation", by Mr. l. V. Joludev, Head of General Inspection of Safety, Civil Aviation, U.S. S. R.; "FAA Safety Research and Development Programs", by Mr. Allen D. Hulen, Deputy Assistant Administrator, Europe, Africa and Middle East Region, of the Federal Aviation Agency of the USA. Mr. Bosko R. Stanojlovic, Overseas Representative of the Guggenheim Aviation Safety Center at Cornell University, explained in his paper "European Aearonautical Research Concerning Aviation Safety", how the increased amount of research for improving the standards of air safety called for an international scheme for exchange of information in air safety research projects. This information is collected from throughout the world and published by the Guggenheim Aviation Safety Center in a volume entitled "Survey of Research Projects in the Field of Aviation Safety" yearly. This book is then distributed, free of charge, to all aviation organisations: Civil Aviation Administrations, universities, laboratories, institutes, airlines, aircraft manufacturers, etc. The speaker briefly listed the most outstanding achievements of European research in the field of aviation safety which have found their practical application in aviation industry. He .then ~xamined a few of the most interesting research pro1ects in progress at present in various European countries. Mr. Bosko Stanojlovic who is well known to IFATCA was granted a special award by the Swedish Society of Aeronautics, the Thulin Medal in bronce, for his outstanding merits in the field of civil flight safety. During the sessions Human, Material and Environmental Factors, most various papers were presented ranging from the assessment of flying skills in relation to accident liability to visual presentation of aircraft information . from airline evolution of survival equipment to the possi~ bility of reducing the bird strike hazard. Three papers were presented on air traffic control. In his paper: "The Problem of Air Traffic Control", Roger Sadet, representing IFATCA at this Symposium reviewed the operational, technical and human problems that still

need to be solved. He explained the role IFATCA intends to ploy in the improvement and development of ATC. Mr. Sven Skoraeus of Standard Radio & Telefon AB and Consultant to the Royal Boord of Civil Aviation of Sweden, explained that if automation in ATC was necessary to give the controller more time for his essential duties, this has to be done very carefully and progressively. He discussed the progress of automation with handling of data and updating derived from radar information. Mr. J. N. Toseland, Linesman - Mediator Project Authority, Ministry of Aviation, London, spoke about "the Future Trends of Air Traffic Control". After pointing out

the problems arising from automation and data processing, he considered the philosophy of displaying, correlating and actioning ATC data. He further described the impact of automation on the role of the air traffic controller and the man-machine relationship in ATC. Finally, the speaker gave some thoughts to the eventual evolution when ultimately full automation will be reached. Those wishing to receive the integral papers of this very interesting symposium can order a copy of the proceedings from the following address: The Swedish Society of Aeronautics, Stockholm 70, Sweden.

The Problem of Air Traffic Control The title of this paper is called "The Problem of Air Traffic Control". From the start it is suitable to correct this and a plural form should be used at the word problem. For it is true that in Air Traffic Control the problems are numerous and various. As a profession, ATC is a young one, and therefore not well known, and then only known to people and organisations that are actively engaged in aviation. For the layman paying an occasional visit to an airport the air traffic controller is a man who is vaguely connected with the aircraft movement and no further thought is given to him when the idle eye wanders from the Control Tower to the powerfully engined intercontinental airliner. Of course, he stays on one side of the barrier, on the public side, where the product is offered, well advertised, to scores of people, from businessmen to holiday-maker, for a quick and safe flight to their destinations. If he were to penetrate beyond the barrier he would be able to find a group of people, sitting in semi darkness, in front of huge flight progress boards or working at radar scopes. This image really characterises the air traffic controller. He is a man working in the dark, but at the same time, through his essential role, holds a key-position in civil aviation.

Operational Problems The Objectives of Air Traffic Control The objectives of ATC, as defined by ICAO, are to prevent collisions between aircraft and to expedite and maintain an orderly flow of air traffic. To achieve these objectives ICAO has evolved rules, recommendations and procedures the implementation of which is the responsibility of States organising the air traffic control services. The problem of organising and operating these services has been approached by States in different ways using different methods. At the time ICAO published its rules and procedures, shortly after World War 11, the business of flying, backed up by an ever developing aviation industry, progressed with giant's steps. Already in the early years of air traffic control, people in the service had the uneasy feeling that their methods were not adequate enough to cope with the rapid growth of civil aviation. It grew clear that the

Paper presented by R.J.Sadet, at the International Symposium on Civil Aviation Safety

air traffic control system could not keep abreast with the rapid technical development in the aircraft industry encouraged by national prestige and demands for more modern and faster means of transportation. In the best cases air traffic control could only adapt itself to the ever changing situation and, consequently, was lagging behind. This is the first problem in Air Traffic Control. The gap that was apparent in the beginning has been deepening and may eventually become ominous. ICAO has also become aware that a system based on rules devised for speeds between those of the DC 3 and the DC 6 could not be considered realistic in the second decade of the jet age. This is reflected by the results of the RAC/OPS Divisional Meeting held in Montreal in 1963. New criteria of horizontal separation minima have been laid down, based on distance rather than on time. The new concept will permit greater flexibility in the use of airspace for air traffic control purposes regardless the speed of the aircraft. Since the introduction of radar in ATC this flexibility is reached to a great extent in that it assists the controller in expediting the flow of traffic, reducing the separation minima and vectoring aircraft, to effect an efficient traffic sequence. However, radar has its inherent shortcomings and all individual cases cannot be solved. This is only one of the reasons for which both IFATCA and IFALPA adopted the policy that the navigation of the aircraft must be left in the cockpit, and that radar should only be used as an aid to ATC.

Organisation of Airspace As you know the airspace is divided in controlled airspace where positive control is provided, and uncontrolled airspace where only flight information service can be given. Althought different rules govern flights in these two different airspaces, this did not create too great a problem when aircraft were flying only at the iow and medium levels. However, since the jet operations started, flights were conducted at much higher levels and the upper airspace was no longer the realm of military aircraft. It is not generally known that the modern airliners, transporting a great number of passengers at very high speeds, are, in great parts of the world, flying above the vertical

limits of controlled airspace, thus in uncontrolled airspace together with other aircraft that are not necessarily known to the ground services. Although most of these aircraft are flying above the weather and must therefore follow the rule of "to sec and to be seen", they cannot rely on their own to avoid other traffic because of the restricted view from the cockpit and the high dosing speeds of these aircraft. Pilots flying at these levels continue reporting their times over reporting points, their flight levels and estimates to the next point, on the normal control frequencies, as if they were flying in controlled airspace. As mostly all other jets do the same, air traffic control is able to give the pilots the best service possible, which in fact, is only advisory service in this case. This creates a problem in which dubious situations may arise where the pilot believes he is being controlled when in fact he is not. The answer to the problem is probably the complete integration of civil and military traffic especially at these high levels. In several countries this has already been achieved with good results but in many other States no progress is made and great difficulties still exist due to military sovereignty. Military operational traffic by reason of its very nature escapes from the rules followed by other traffic . An ever growing problem is the relation between public and private air transport. General aviation claims freedom in the air whilst airlines claim maximum control. A compromise between these two contrary opinions is necessary but difficult to achieve.

Co-ordination The consequence of the increased volume of traffic and ensuing heavy workload is the splitting up of control in sectors thus creating a problem of co-ordination. The division of airspace in horinzontal slabs and vertical portions multiply the co-ordination difficulties which in turn are increased by the high speeds of the aircraft. It has been experienced over and over again, that the most critical phase in the control of traffic is the co-ordination between air traffic control units both nationally and internationa I ly.

and industry. But the problem of equipment remains one that must be taken into consideration carefully and the controller should be consulted when specifications are to be drawn up for new equipment so that the hardware yields maximum service. The general use of secondary radar will help to increase the capacity of ATC. Similarly the possible implementation of data links transferring flight data and ATC communication frequencies thus allowing the controller more time for his essential duties.

Automation Air traffic control is an activity which in its essential parts escapes from automation. Of course there exist a number of parameters, though extremely variable, that are known to ATC from the flight pion, such as routes of flight, air speeds, performances of aircraft, etc. These can easily be processed by computors and an automated display system of flight data is necessary in a busy ATC Centre. This is needed in order that the air traffic controller can concentrate on his job of maintaining the necessary separation between aircraft and to ease the co-ordination problem. However, the decision making part of the job, hos to be left to the human being. Conflict detecting computers can be devised giving the most immediate solution to the problem, or even a number of solutions. However, a human controller is needed to select the most suitable solution in the given circumstances compatible with the economic operation of the flight. Perhaps a major question is: Can a fail safe system be built; what would happen if the human being would have to take over from the machine when it stops functioning. In air traffic control unexpected factors are too many to make a successful and completely automated system possible in the near future. It will be necessary, anyhow, for the human being to control the machine at all times and to be in a position to take over should the system fail. Another problem is the requirement for compatibility of the different automated systems as in the coordination of traffic between adjacent units in different countries using different automated systems of data handling.

Human Problems Technical Problems

Recruitment, Training, Career

Equipment

Since the air traffic control function is to guarantee rnfe air navigation, the selection and training of ATC personnel is extremely important. This proves to be a great problem in many countries and depends also on the degree of development in each

To perform his exacting duties the air traffic controller needs adequate tools enabling him to handle the traffic regardless of the traffic density and the high speeds at which the aircraft are flying. In the early years of air traffic control lhe area controller had at his disposal a sheet of paper and a few coloured pencils . Rapidly, as traffic increased and workload built up, he was given better tools which in some cases reached a high degree of sophistication. Gradually the tool became a machine that drew more and more attention and the human being tended to be neglected. lnsiances are known where air traffic controllers were to work with equipment that was designed by ~eople who technically speaking were skilled but had no .1de. a o f air 路 t ra ff'1c control, so, their product, rather than assisting the controller, increased his workload. Fortunately great progress has been made in this field thanks to better co-ordination between administrations, controllers

of them. In order to have a great choice in the selection of candidates it is required that, firstly, the job is well known and, secondly, that the job is made attractive enough. We have seen that in general the firsr condition is not fulfilled. National administrations could improve this to some extent by interesting more young men at an early age to a career in aviation and by providing an advanced education scheme directed to such career. The second condition, of course, is closely related to the prospects of career and salary offered. In less developed countries there are a lot of attractive jobs that seem more essential to the economy of the

State than the one of air traffic controller. In highly developed countries a problem is created as a consequence of the high demand for personnel in all branches of the nation's economic life. In most countries with a high standard of living, university training is now considered a normal stage in the education of a young man. Also those who economically are less fortunate are given access to academic training through students funds and foundations. So, a promising hard working young man having the necessary moral and mental qualities will most probably turn to other branches offering better possibilities in career making. The ICAO physical requirements laid down for ATC personnel in Annex 1 call for persons meeting the same physical requirements as for commercial pilots. No criteria however are laid down as regards character and moral qualities. In many countries psychotests are used in selecting ATC personnel. In other countries scepticism exists toward the reliability of this method, a significant fact noted being that in many countries different criteria are used. So far no standard method has proved to be fully and universally acceptable. The duties of an air traffic controller require from the individual a high degree of morality, a very good nervous and emotional balance, a sound critical judgement, a readiness for decision, and an instinct for路 team work. Obviously it is difficult to find these qualities combined in young men around twenty years of age. Experience in one of the countries of Western Europe shows that out of 60 ATC applicants 1O are admitted and of these only 5 successfully pass the first basic air traffic control training. A more successful selection can probably be made if the candidates are recruited among young men with a university background of 2 or 3 years. Their college-level education should normally give the individual a number of the qualities that are basically required. Age is another problem in the training of air traffic controllers. Statistics compiled in the U.S.A. show that age is in negative proportion to success in becoming a satisfactory controller and that the chances are 1 in 4 or 5 when the training is started after the age of 33. This discussion proves the importance of recruiting young candidates, and at the same time the difficulty of finding the physical and mental capabilities in them. The chances of success in recruiting suitable individuals are naturally proportional to career possibilities, terms of employment and working conditions, which, unfortunately in many countries, are inadequate. In most cases, air traffic controllers are civil servants. Although their duties and responsibilities cannot be compared, they are linked up as regards terms of employment with those of the administration. This is an unsatisfactory situation increasing the problem of finding personnel able to qualify satisfactorily for the job of ATC.

Environmental Factors The safety of air navigation is critically dependent on the human being. The air traffic controller occupies a key-position in that he carries the responsibility of human lives the safety of which depends on his judgment and skill in making the correct decision at the correct time. When he experiences a critical situation he cannot refer to a higher ranking man for advice in solving the problem

nor can he defer the matter to a later moment and take the decision after mature reflection. This immediate decision making is rendered more difficult by his acute sense of responsibility and the high demand of concentration when following an ever changing three dimensional traffic situation. Decisions have to be made under stress when working in a dense traffic environment. Adverse physical conditions as unsuitable lighting, high noise level, inadequate working space, obsolete or poorly designed equipment, all of which combined or single, may reduce his capacity dangerously especially when the mental strain continues over a period in excess of one or two hours. These adverse working conditions, together with knowledge that the system he is serving is falling behind the present day requirements, the fact that he is alone and in case of error may not get support from his superiors, can lead to a state of dissatisfaction detrimental to the safety in the air and in extreme cases to nervous breakdowns. The human problems encountered have certainly suffered under the attention given to technical and operational problems. It is clear that much remains to be done in the field of human engineering.

IFATCA In a number of countries air traffic controllers have formed associations with the object of promoting the ATC profession. The objects of most of these associations are purely technical, making available the professional experience controllers have to the sound development and improvement of ATC at a national level. As the problems of ATC are the same all over the world, the necessity was felt for international co-operation between these organisations. This has led to the creation by 12 European Associations of the International Federation of Air Traffic Controllers' Associations, in Amsterdam in October 1961. An extract of the objects of the Federation indicates the role IFATCA intends to play in the furtherance of flight safety: - To promote safety, efficiency, and regularity in International Air Navigation; - To assist and advise in the development of safe and orderly systems of Air Traffic Control; - To uphold a high standard of knowledge and professional efficiency among Air Traffic Controllers. In order to follow these aims and objects, the International Federation of Air Traffic Controllers' Associations will: - Closely co-operate with national and international aviation authorities and other institutions or persons concerned with air navigation; - Assist in the development of new procedures and facilities necessary and useful for the safety of International Air Traffic; Collect and distribute information on professional problems and developments. That the controllers do not know all the answers to the problems is obvious, but here is an international body of controllers possessing a wealth of experience offering its collaboration to national and international aviation organisations and authorities. At the present moment I FAT CA counts 22 member Associations in as many countries on 5 continents. The appli-

cation of the 23rd Association has just been received. International from the start IFATCA is spreading world wide. Although still in its formative years it has fruitful contacts with international bodies like ICAO and IFALPA. It endeavours to increase collaboration with ICAO on those problems that have a direct bearing on air traffic control. The best relationship, based on mutual understanding and esteem of each others responsibilities, exist with IFALPA. Pilots and air traffic controllers require the same basic qualities. These conditions create fertile ground for the discussions tending to achieve a common policy in all aviation matters interesting both professions.

Conclusion Mr. Chairman, Gentlemen, I am fully aware that this paper is deceptive in that it has pointed out a - by no means exhaustive - number of problems without offering

any solution. In this paper I have made on attempt of briefly summing up some of the problems encountered in Air Traffic Control. At a first stage, it is always important to describe the problems clearly, then to examine the reasons underlying them, before a start can be made to solve them. The air traffic controllers ore willing to collaborate in their country with the national authorities responsible for the organisation of the air traffic control services, and internationally through their Federation. In this respect they are pooling their efforts by exchanging their know-how and experience to find a way to the improvement and standardisation of systems and methods. I believe that the objective of this symposium was to highlight the problems in international aviation 路in an effort to prepare the meeting ground for a better co-ordination of the activities in the research of improved aviation safety. I therefore sincerely wish that this paper will have reached its purpose.

*** letters to the Editor I have read with great interest the report in your Journal of the Fifth Annual IFATCA Conference in Rome. What particularly interested me is the reference on page 41 regarding bright displays. I agree with Dr. Benini that, if his remarks are intended to include CRTs only, you cannot have a large bright display for alphanumerics and radar. Also, I found the Marconi representative's remark, stating the limits in size and resolution with the bright screen, very interesting. I would like to say, however, that bright screen radar displays are possible and are used extensively by Merchant Navies and for certain air traffic control applications, and they are eminently suitable for displaying alphanumerics and radar on the same screen. I am referring to the Rapid Access Photographic Display System developed and produced by Kelvin Hughes, a member of Smiths Industries Ltd., in England. This system photographs the display appearing on CRTs, processes and projects the image so obtained on a photographic film in a fully automated instrument with a minimum of time delay. As the final display is a projection of an image appearing on a 16 or 35 mm photographic film, there is practically no limit to the size and brightness of the display obtainable. The processing time can be as short as some 3 seconds after exposure and the renewal rate is equal to the processing time. Positive or negative processing is obtainable at will, and coded colour types are also available. The colour code con represent additional information of arbitrarily chosen groups. Several types are available where the final display is derived from 2 or 3 independent information channels, hence it is quite convenient to combine in proper register alphanumerics and direct radar with the characteristics as required by Dr. Benini. In some very large installations total light flux of some 4,000 lumens has been achieved. The delay occurring in showing the display and the renewal rote must be considered in terms of the information renewal rate of the incoming intelligence. For air traffic control radar, assuming a range of some 100 miles to be ~hown, and with aircraft flying at a speed of some 600 miles per hour, the processing delay time represents

an echo displacement on the screen of 1/400th part of the screen diameter. The photographic process is sensitive enough to record quite clearly the afterglow images of the long persistence screen CRT, hence past history is indicated in the form of a track consisting of a trail or separated dots according to the speed of the aircraft. The records are of full archival quality, therefore represent a full documentation, and con be replayed in real or accelerated time in a very simple projector. According to detailed cost analysis the overall operational system from the economic point of view is compatible on operational cost with magnetic tape recording, and considerably less costly on capital investment. As regards air traffic control applications the system was specified for the large screen display of the Eurocontrol simulator and installed in the Orly centre, and the colour version of it is being planned for the West Drayton installation of the notional air traffic control services in England. Large screen displays of this type have been manufactured and are used for military applications in several countries. for KELVIN HUGHES G. WIKKENHAUSER Chief Development Engineer. Special Director, Smiths Industries Ltd.

The discussion panel on "Air Traffic Control Displays" at the Fifth Annual IFATCA Conference also touched on the comparative accuracy of VOR/DME and DECCA. The statement by a member of the audience, reported on page 41 of THE CONTROLLER, Volume 5, No. 3, that, inter alia, the Scandinavian countries use DECCA for calibrating their VOR facilities is not factually correct so far as Norway is concerned. Such a method for calibrating VOR facilities in Norway has not been used, nor is any airborne installation for such purposes contemplated. B. GRINDE Director, Air Navigation Directorate of Civil Aviation Oslo, Norway

lrlhe h'1lternational Federation of Air Traffic Controllers Associations Addresses and Officers AUSTRIA Verband Osterreichischer Flugverkehrsleiter A 1300, Wien Flughafen, Austria President First Vice-President Second Vice-President Secretary Deputy Secretary Treasurer

Secretary Treasurer IFATCA Representative Editor

Heikki Nevaste Aimo Happonen Andre Remy Viljo Suhonen

H. Brandstetter

A. Nagy H. Kihr R. Obermayr W.Seidl W. Chrystoph

FRANCE French Air Traffic Control Association Association Professionnelle de la Circulation Aerienne

B. P. 21 Aeroport du Bourget, Seine France

BELGIUM Belgian Guild of Air Traffic Controllers Airport Brussels National Zaventem l, Belgium President Vice-President Secretary Treasurer Editor

A. Maziers R. Sadet R. Tamigniaux R. Maitre 0. Haesevoets

President First Vice-President Second Vice-President General Secretary Deputy Secretary Treasurer Deputy Treasurer

Francis Zamith Maurice Cerf J. M. Lefranc Jean Flament J. Lesueur J. Bocard R. Philipeau

GERMANY CANADA Canadian Air Traffic Control Association 56, Sparks Street Room 305 Ottawa 4, Canada President Vice-President Managing Director Secretary-Treasurer IFATCA Liaison Officer

J. D. Lyon J.C. Conway L. R. Mattern E. Bryksa J. R. Campbell

German Air Traffic Controllers Association Verband Deutscher Flugleiter e. V. 3 Hannover-Flughafen, Germany Postlagernd Chairman Vice-Chairman Vice-Chairman Vice-Chairman Secretary Treasurer Editor

W. Kassebohm H. Guddat E. von Bismarck H. W. Kremer D. Rosse K. Piotrowski L. Goebbels

DENMARK Danish Air Traffic Controllers Association Copenhagen Airport - Kastrup Denmark Chairman Vice-Chairman Secretary Treasurer

P. Knudsen

A. Frentz F. Fagerlund P. Breddam

GREECE Air Traffic Controllers Association of Greece Mersisis St. 8 Athen, N. Filadelfla, Greece President Vice-President General Secretary Treasurer

N. Gones E. Petroulias E. Karagianides C. Theodoropoulus

FINLAND Association of Finnish Air Traffic Control Officers Suomen Lennonjohtajien Yhdistys r.y. Air Traffic Control Helsinki Lento Finland Chairman Vice-Chairman

Fred. Lehto Jussi Saini

ICELAND Air Traffic Control Association of Iceland Reykjavik Airport, Iceland Chairman Vice-Chairman Secretary Treasurer

Valdimar Olafson K. Simonarson Einar Einarsson Guolaugur Kristinsson

IRELAND Irish Air Traffic Control Officers Association Air Traffic Control Cork Airport Cork, Ireland President Vice-President IFATCA Secretary Treasurer

D. J. Eglington P. J. O'Herbihy J. Grey P. P. Linahan

IS RAEL

P. 0. B. 33 Lod Airport, Israel Jacob Wachtel W. Katz E. Medina

ITALY Associazione Nazionale Assistenti e Controllori della Civil Navigazione Aerea Italia Via Cola di Rienzo 28 Rome, Italy President Chairman Secretary

Senator P. Caleffi C. Tuzzi L. Belluci

LUXEMBOURG Luxembourg Guild of Air Traffic Controllers Luxembourg Airport President Secretary Treasurer

Alfred Feltes Andre Klein J.P. Kimmes

NETHERLANDS Netherland Guild of Air Traffic Controllers Postbox 7531 Schiphol Airport, Netherlands President Vice-President Secretary Treasurer Member Member

J. van Londen J. L. Evenhuis J. Thuring G. J. Bakker F. J. Stalpers L. D. Groenewegen van Wijk

NEW ZEALAND Air Traffic Control Association Dept. of Civil Aviation, 8th Floor, Dept. Bldgs. Stout Street Wellington, New Zealand President Hon. Secretary

R. G. Roberts

Chairman Secretary Treasurer

E. Dahlstedt B. Hinnerson C. A. Starkman

Swiss Air Traffic Controllers Association V. P. R.S. Air Traffic Control Zurich-Kloten Airport Switzerland Chairman Secretary

Bernhard Ruthy Walter Tanner

UNITED KINGDOM Guild of Air Traffic Control Officers 14, South Street Park Lane London W 1, England Master Executive Secretary Treasurer

L. Vass Mr. Rimmer E. Bradshaw

URUGUAY Asociac;:i6n de Controladores Aeropuerto Nacional de Carrasco Torre de Control Montevideo, Uruguay Chairman Secretary Treasurer

U. Pallares J. Beder M. Puchkoff

VENEZUELA Asociacion Nacional de Tecnicos en Transito Aereo Venezuela Avenida Andres Bello, Local 7 8129 Caracas, Venezuela President Vice-President Seer. Public Rei. Seer. Organisation Seer. Documentation Seer. Finance Vocal Vocal Vocal

Manuel A. Rivera P. Luis E. Lamela del Nogal Rafael Reyes Barreto Luis Bronchi Gonzales Alejandro Pena Luis R. Dominguez G. Jose Ramon Garrido Antonio Sequera Antonio J. Ducarte

YUGOSLAVIA Jugoslovensko Udruzenje Kontrolora Letenja Direkeija Za Civilnu Vazdusnu Plovidbu Novi Beograd Lenjinov Bulevar 2 Yugoslavia

Lufttraflkkledelsens Forening Box 135 Lysaker, Norway

SWEDEN Swedish Air Traffic Controllers Association Luftvartsverket Brom ma 10, Sweden

E. Meachen

NORWAY

Chairman Vice Chairman

P. W. Pedersen

A. Torres

SWITZERLAND

Air Traffic Controllers Association of Israel

Chairman Vice Chairman Treasurer

Secretary Treasurer

F. o;e K. Christiansen

President Secretary

I. Sirola A. Stefanovic

Selenia products are vwarking far safety the air

ATCR systems and METEOR radars from SELENIA have been chosen and are in operation for the Air Traffic and Weather Bureaus Authorities of 15 Countries.

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