IFATCA - The Controller - May 1976 by IFATCA

D 21003 F

JOURNAL OF THE INTERNATIONAL FEDERAT I O N OF Al R TRAFFIC CONTROLLERS ASSOC I ATIO N S

In this Issue:

The Air Traffic Control Evaluation Unit, Hurn, U.K. Air Traffic Control In Sweden

FRANKFURT AM M A I N

, f11

M A Y 19 76

VOLUME 15

N0 . 2

1700 reasons for choosing the IAL colleQe of air traffic services Since 1958 we have trained more than 1.700 students of 71 nationalities as Air Traffic Controllers for overseas Governments to ICAO standards. The high standard achieved and maintained by our instructional staff of experienced controllers is one of the many reasons for IAL being selected by these authont1es. Flexibility and economy are added attractions. Courses can be tailored to meet 1ndiv1dual requirements. incorporating national ATC leg1slat1on if necessary. At compet1t1ve pnces. All the courses are approved by the Civil

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College ofAir Traffic Services The Administrator. IAL College of Air Traffic Services, Oxford Airport. K1dhngton, Oxford, OX5 lSH. England. Telephone: K1dhngton 6168.

IFATCA

JOURNAL

AIR

TRAFFIC CONTROL

THE CONTROLLER Frankfurt am Main, May 1976

Volume 15 • No. 2

Publisher: International Federation of Air Traffic Controllers' Associations, P. 0. B. 196, CH-1215 Geneva 15 Airport, Switzerland. Officers of IFATCA: J-0. Monin, President, 0. H. J6nsson, Vice-President (Technical), H. H. Henschler, Vice-President (Professional), E. Bradshaw, VicePresident (Administration), T. H. Harrison, Executive Secretary, H. Wenger, Treasurer. Editor: G. J. de Boer,

P. 0. B. 8071, Edleen, Kempton Park, Tvl., 1625 South Africa, Telephone: 975-3521 Conlrlbullng Editor: V. D. Hopkin (Human Factors) Managing Editor: Horst Guddat, Otto-Bussmann-StraBe 7, D-6368 Bad Vilbel 2, (Federal Republic of Germany). Telephone: (06193) 85299 Publishing Company, Production, Subscription service and Advertising Sales Office: Verlag W. Kramer & co., Bornhelmer Landwehr 57 a, 6 Frankfurt am Main 60, Phone 43 43 25 and 49 21 69, Frankfurter Bank, No. 3-03333-9. Rate Card Nr. 6. Printed by: W. Kramer & Co., Bornheimer Landwehr 57 a, 6 Frankfurt am Main 60 (Federal Republic of Germany).

CONTENTS

The Controller's Legal Liability (II) • . . .

Subscription Rate: OM 6.- per annum for members of IFATCA; OM 10,- per annum for non-members (Postage will be charged extra)

The ATC Evaluation Unit, Hurn Airport, U.K. •

Integration of SST in the Non-Sophisticated ATC Environment

Contributors are expressing their personal points of view and opinions, which must not necessarily coincide with those of the International Federation of Air Traffic Controllers' Associations (IFATCA).

The Provision and Use of Information on Air Traffic Control Displays (I)

International Law (IX) . . . . .

Air Traffic Control In Sweden (I)

The Controller's Responslbillty as viewed by the High Court of Australia • . • • • • . . . • •

Air Route Surveillance Radar System ARSR-3

Social Stress and the Air Traffic Controller .

Birds In Flight: Radar Observation and Avoidance Procedures which can be emplo)ted by Air Traffic Controllers

IFATCA does not assume responsibility for statements made and opinions expressed, It does only accept responsibility for publishing these contributions. Contributions are welcome as are comments and criticism. No payment can be made for manuscripts submitted for publication In "The Controller". The Editor reserves the right to make any editorial changes In manuscripts, which he believes will Improve the material without altering the Intended meaning. Written permission by the Editor is necessary for reprinting any part of this Journal.

Cartoons: Helmut Elsner. fotos: Archiv, L. Allwin, Directorate of Civil Aviation Bahrain, IAL, M. Laty, J. Lawrence, P. Smith, Stansaab'. K. Board of Trade.

Advertisers In this Issue: International Aeradio Ltd. (Inside Cover), T-VT (page 3), Hollandse Signaalapparaten (page 7), Ferranti Digital Systems (page 25/ 25), Racal Thermionic Ltd. {back cover).

Airports and their Control Towers (4) The Dallas-Fort Worth Airport

News from the Federation • . • • .

The Controller In Aircraft Accident Investigation

The Piiot's Point of View . • • . .

News from Member Associations .

Publications Review • . . • . .

49 1

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From The Tower

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How To Advance The Controller's Profession: Internationally, Or In Isolation?

"I personally believe that International air traffic Is a very strong force for promoting world peace and improving the understanding and ties between nations." "We no longer felt that the international body could best serve the continuing Interest of our membership as it Is currently structured." These two phrases from one and the same letter written by John Leyden, President, Professional Air Traffic Controllers' Organisation (USA), to the President of IFATCA in which the organisation announced its withdrawal from our Federation, are contradictory in nature. If international air traffic is so beneficial to us all, even more so is personal contact, collaboration between national groups on an international level, and participation in the work of a body such as IFATCA. . For a number of years now, our Federation has advanced the air traffic controller's cause m the international aviation arena. IFATCA's representatives sit in at !CAO-meetings and have a direct say in the drawing up of the world's aviation regulations which are of concern to th? controller in his daily work. The Federation represents the controller at international meet~ngs such as medical symposiums safety seminars human and environmental study meetings • meermgs on labour and health• problems in aviation • on airport and airspace matte~, etc. The list is endless. ATC is an international professi~n. Air traffic controllers are a ~niq.ue group in world society, international through and through. Isolationism is utterly ore •g.n to th~m. An air traffic controller holds an international (ICAO) licence, and he cont ro 1s mternat1onal traffic. And yet, the question sometimes arises: is our involvement in the international aviation are~a, through IFATCA, really necessary? Is it not possible to advance our profession by cutting out our attendance at and our involvement in International gatherings and matters, to do away with IFA"fCA, and to advance our interests singly, in isolation? And, in doing so, save some money? The answer, I'm sure, no thinking air traffic controller would say lies in isolating our~elves. ~ost of us would say that this is a silly question; of course we must band together internationally to have any say in aviation at all. How then, I ask, can you explain that this group of air traffic controllers in one of the most airminded countries in the world, decides to withdraw from effective international involvement, turns its back on their fellow controllers in other parts of the world, and instead now goes it alone, in isolation? Have these people got their priorities right? It is sad to answer that they have not, and that their action is dlvisory rather than uniting at a time when we most need to stand together. It is to be sincerely hoped that our friends who have taken that unfortunate decision to go it alone, will come back on their move which is detrimental to the interests not only of their own supporters but to the interests of all air traffic controllers the world over. It is possible that PATCO as a whole might change its mind in due course. One thing won't change and that is the need for controllers to unite around the world so that we can look after the poorer members of the family who in their depressed environment and .with poor equipment are doing their best to look after all the modern aircraft the manufacturers pour out. They in particular are bound to look on PATCO's withdrawal as an act of desertion. Our Federation is proven to be effective. We strive constantly to improve IFATCA's performance, and no-one, but no-one has said that the Federation fails to take its chances. On the contrary. IFATCA's record over 15 years speaks for itself. For that reason alone, the PATCO decision, after six years of affiliation to the international body, will never be understood by the world's controllers.

J-0. M.

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Aerosat: How Final Is Final? ATC is as international as flying. Yet, instead of following the precedents set so s fully 路, n th e f"1e Id o f 路in t_er~at"1ona1 c~-operation concerning the flying side of civil aviation, uccessin ATC w~ have yet again 1ust experienced the exact opposite. This time it was the future of th:~mted States/ Eurkopea~/Can~dian experimental aeronautical satellite (Aerosat) venture w 1 once more oo ed like being bedevilled. The problem was a financial disagree t between the Federal Aviation Administration and Comsat General, the U.S. manage::~t company, on the cost of the space segment which comprises the two satellites with their telemetry and the ground-control stations.

One of our IFATCA Vice-Presidents used to say: "nothing is final except death" a philosophy which he advanced during Executive Board meetings. Although the final decislon to go ahead with Aerosat was made a long time ago, none of us were therefore surprised to hear recently that the development of this important project, which was held up for so many years by financial and other disagreements, was again placed in serious doubt. How come this time? In 1974, the European Space Agency (ESA) selected Comsat General to finance the U.S. share of the space segment, and it was envisaged that the American company would regain its outlay and achieve a comfortable profit-margin from circuits which It would lease to the FAA. Comsat General thought that it would need about $125 million for equipment such as launch facilities, satellite tracking, and data processing, maintenance tasks, etc. But the FAA disagreed, and believed that the total cost need not exceed the order of some $ 75 million, and the net result was that Comsat General was not prepared to go ahead until the FAA had revised its original estimates to somewhere near Comsat General's more realistic $125 million. While this was going on, Europe was twiddling its thumbs in increasing exasperation. The Old World has none of the difficulties which are experienced in the New World, because the European share of the programme is being financed by the Governments of the ESA countries. But the lack of progress in getting to the equipment stage was raising serious doubts among ESA members about America's will - in its present isolationist mood - to overcome the difficulties and honour obligations entered into officially in,1974 and in spirit even long before that year. Obviously, cancellation at this late stage would have adversely affected future multinational commercial space programmes for a very long time to come. tt was said that the U.S. congress objected to the allocation of the large amount of money that is involved in a non-operational exercise like Aerosat. There is no point in repeating the benefits to us which Aerosat would produce, as these have been clearly outlined in THE CONTROLLER. In actual fact, it is not so much the benefits of Aerosat, as the benefits of later aeronautical satellites air traffic controllers are looking forward to receiving as we can expect other parts of the world (Africa, Asia, Pacific) to be covered eventually after the successful outcome of the Aerosat experiment. So it seemed we were back to square one, and that even a final decision wasn't final. To us' it is discouraging, and demoralising, that money invariably seems to be available for all sorts of improvements in flying, but so often when it comes to improving the tools of the trade of those involved in the control of air traffic, the money isn't there. With the apathetic attitude of the airline segment, which has never shown enthusiasm for the Aerosat project and with no help to be expected from that quarter, we could not help remembering those words of our former Vice-President. 路 ht Just when the picture began to look really black, the Aerosat Council announ. .. How ng . ced in Paris that the difficulties had been sorted out, and that the final dec1s1on had been made to proceed with the scheme. The first of the two satellites is expected to fly before the end of 1979. But how final is final?

GdB

Some Words 路Of Praise From One Who Knows Mr. Walter Binaghi, retiring President of the Council of the International Civil Aviation Organisation, has written to IFATCA's President as follows:

"Throughout my years as President of the Council and, previously, as Chairman of the Air Navigation Commission, I always strove for fruitful co-operation between ICAO and international organisations devoted to civil aviation. I am glad to say that IFATCA has always rated high among those who made excellent contributions to our work." The Federation wishes Mr. Bi nag hi the very best in his future commitments and private life. 4

The Controller's Legal Liability by Andreas Avgoustis, LL. B. (Lond.), Chairman of IFATCA Standing Committee VII (Legal Matters)

Part II Increased Liability Courts recognise that aviation safety requires the efforts of the air traffic controller on the one hand and the efforts of the pilot on the other; their efforts are complementary to each other. The public travelling by air have no alternative but to rely on the efficiency of both the controller and the pilot for their safety in flight. The magnitude of controller responsibility to the air user can never be overestimated. Errors in judgment could result in disaster. This great responsibility however does not in any way reflect the extent of the lack of protection afforded to the controller, although it may be indicative of the underlying stress imposed upon him. Despite assurances from the Aviation Authorities that such liability is purely theoretical and of no practical effect and that in no circumstances does it create an imminent cause for alarm, evidence however confirms that the controller's concern is real enough, and that his liability increases steadily. Increased liability incurred by the controller creates even more pressure in a profession which is already subject to much stress. It is absolutely a conjecture to suggest that any increase of the controller's liability will encourage a correspondingly more careful and exact performance of duties. The Aviation Authorities and the general public are aware, as a result of publicity during the last decade, of the stress experienced by controllers in their efforts to preserve safety in the air by constantly having to take rapid, sometimes split second decisions. But recognition in itself is not sufficient to relieve the controller of his anxieties or legal liabilities. Assurances received from officials do not determine legal protection especially when judicial precedents contradict such assurances. Certainly, the general practice with regard to civil liability may well be that the controller's negligent act will hold the employer vicariously liable and therefore any compensation awarded will have to be met by the employer. Yet, there may exist a country, or the case could arise somewhere when the employer - almost invariably the State - would be immune, or there could be a remote possibility at some occasion when the employer would seek reimbursement from the employee-controller if the Courts determine that the negligent act of the controller had been outside the ambit of his defined duties. Though it may seem illogical and impracticable for the employer or the aggrieved party, where large amounts of money in damages are involved, to sue the controller as he will in most cases be insolvent, nevertheless it will not be a sufficient reason to disregard them. The question that may naturally evolve in our minds from this legal perplexity is when such negligent acts do not come within the course of the employee's duties. It is somewhat difficult if not impossible to think of an instance in the case of a controller, though one may come across numerous Court precedents involving other professions. An average of twenty aircraft accidents occur annually in

which the Air Traffic Control element is alleged to have contributed to them. Fortunately none have so far had this 'personal' factor. The only case that could spring to mind at this stage is the case of an off-duty controller who happens to visit his control unit for some reason, and who takes the microphone to issue a clearance which is the cause of an aircraft accident. French Law calls this "personal liability". The employer in the above illustration is liable to the aggrieved and will compensate. Such employer, however, may consider that the use of the microphone by the off-duty controller was outside the performance of his normal duties and may seek reimbursement. Of course, this argument is purely hypothetical since there is no Court precedent that may confirm this. In order to make things more clear, allow me to give you another example, this time based on a Court precedent from which you may draw your own conclusions. The driver of a bakery van decides to divert from his prescribed route of delivery to visit his home in a nearby town. Along the way he is involved in a road accident. Undoubtedly, the accident occurred outside the course of his duties, and should the employer be sued he will have to pay damages, but he can claim back such damages from the employee. 'Personal liability' of the controller should not cause grave concern because that possibility is remote. On the other hand, the possibility of criminal or administrative liability is constantly present in aircraft accidents or incidents if the controller's act should be judged criminal or wrong administratively. As stated above any assurances as to the employer's liability is strictly confined to civil liability, i. e. payment of compensation, and has no bearing whatsoever on criminal liability. The law is very specific and any form of guarantee against criminal liability is ipso facto illegal unless the national law expressly provides for such immunity.

Controller Concern The controller, through his Federation (IFATCA) in his attempts to achieve some form of security has never tried to secure immunity from intentional negligence, which IFATCA has repeatedly stressed. What the controller has sought and is insisting upon, is that once negligence has been proved to be unintentional, he should not be further persecuted. IFATCA's concern is indicated by the fact that a â&#x20AC;˘Standing Committee (VII) has been created to study among other things the legal liability of the controller and the desirability of drawing up, through ICAO, an international convention by which the controller's status and career is safeguarded. Furthermore, clarification sought by individual controllers or by national Associations from their employers regarding the extent of the controller's liability in cases of aircraft accidents tends to strengthen the view that controllers are not protected under the law. To illustrate this, permit me to produce brief extracts from correspondence seeking such clarification, firstly, by a controller; secondly, by an Association; and lastly, by a lawyer.

To G. Goodall, of the Australian Association: "At each and eve~ stage of your very likely brief career in this game you are in a dangerous state of compromise with the law ~s an impartial judge sees it, and the law as the AIP sees and at no stage of the game will you be pronounced innocent." [See also the judgment delivered in the Jandakot accident as reported in our August 1975 issue - Ed.] "I take it that the Association is moving hell and high water to ensure that no innocent Air Traffic Controller spends the greater proportion of his life behind bars because someone ends up in charge of an aeroplane and is incapable of carrying out the responsibility which goes with the licence." From the Canadian Association to the Canadian Director of Civil Aeronautics: " ... I also request your assurance that in the event of a suit claiming such responsibility on the part of the controller, the Crown would deny that such a responsibility existed and would exhaust every avenue of appeal if a contrary ruling were received." In his letter to the U.S. Federal Bar Association, Attorney J. B. Hill says: "There is a group of Federal employees whose exposure to tort liability is far greater than law enforcement agents and the possibility of personal litigation has - in at least one instance in my personal experience resulted in a near collapse of an individual's personal, financial and psychological life." These statements, which relate to Court suits against air traffic controllers, tend to contradict the assurances so often given by officials, and have had the effect that controller concern in this matter has increased steadily. The U.S. Government being aware of this unjust treatment of the controller by the law has not long ago introduced two Bills before the U.S. Congress which, if adopted, will severely limit the controller's liability. Until now the law in the U.S. (possibly in most States) holds liable to damages anyone who has contributed to the cause of a tort. As a consequence, the controller could be sued under the various States' laws for millions of dollars in damages. These two Bills aim at eliminating such suits, though they equally apply to other Federal employees.

~tructio~s and guidance to controllers providing air traffic services. "However", it continues, "nothing in the MATS P~even~s a qualified controller from using his or her own d1scret1on and initiative in any particular circumstance." In my opinion, such discretionary powers afforded to the controller increase the State's liability. The State empowers the controller, as he deems fit, to deal with particular situations which cannot be covered in a single manual. Nevertheless, it must be borne in mind that where standards ar7 established, viz. separation, etc., his discretion can be said to be limited in that he cannot use that discretion to decrease these standards, but he can increase them for r~ason~ of safety. Should he, however, decide to use his d1scr~tion to decrease such standards, he may find himself m the embarrassing situation of being 'personall liable'. Y Is such discretion, however, working to the controller's advantage? Should he exercise discretion where standard procedures are established? How do Courts view such Procedures and the controller's discretion? These answers can only be given by controllers themselves and by the Courts. G. Goodall, controller-member of the Australian Association, says: "Doing your job exactly according to laid down procedures and not putting as much as a toe out of place as far as air navigation procedures are concerned is painfully obviously not enough." In 1971, the Canadian Air Traffic Controllers' Association, in an enlightening leaflet to its members on controller liability on the occasion of an article written by captain R. H. Jones, commented that despite the fact that the various manuals are..the controller's bibles, they nevertheless "may not offer sufficient protection ..." Justice Kerr in pronouncing judgmen! in the "Wabush Case" - Churchill Falls Corp. v. The Queen & nine Controllers - said: "There are the air regulations and manuals which have, I would think, as one of their objectives - and a most important one - the promotion and provision of safety of air operations, although complete safety cannot be guaranteed and the Crown and the air traffic controller are not insurers of such safety. The regulations and manuals are not a code governing civil liability in the event of Legal Effect of A I Ps an airplane accident, but in my opinion they represent a Before going through cases of aircraft accidents which reasonable standard of care to be observed by air traffic the controller is alleged to have caused, or has contricontrol units and pilots in the carrying out of their activibuted to, it will be of benefit at this stage if we examine ties they have undertaken.'' the legal status of Aeronautical Information Publications According to U.S. Law as pronounced by various Courts and instructions issued to the controller by the Aviation of Law, simple adherence to the directions provided for in Authorities for his guidance or authority. It should be the manuals is not sufficient to relieve the controller of emphasised right from the outset that Government directhe responsibilities under certain special circumstances. tions in the form of circulars or otherwise are administraDiscretion is claimed by these Courts to be exercised tively binding upon the controller unless national legislawhere it will increase the factor of safety in addition to tion provides for otherwise. The general public, and pilots, the published procedures. To illustrate this strong view are not bound by such administrative instructions. reference is made to the decision in the case of FURU~ International Conventions, unless ratified by a State's MIZO v. U.S. (9th Cir. 1967). In this case a light aircraft Legislature, are not valid law in the State concerned. So crashed as a result of wingtip vortices. The Court held are Annexes which deal with Air Traffic Control proceduthat since no standard was set forth for separating airres. some countries however have adopted these Annexes craft on intersecting runways under conditions when wingto the ICAO Convention in toto: others have notified vatip vortices prevail, the matter of separation was therefore riations and others again, like the United States, have their left to the discretion of the controller. The Court held the own exclusive procedures. Added to these procedures, cicontroller responsible for the accident - although he h8 d vil aviation authorities have endorsed wide discretionary warned powers upon the controller in their efforts to preserve . the pilot about the existence of vortices - be cause he did not exercise any form of judgment. Such wa Âˇ safety in the air, additional to or independent from such "d b .. . rnrng local procedures. For example, the British Manual of Air was sa1 to e simply a slavish purported followi f Traffic Control Services (MATS) states that it contains in'the book' with no attempt to exercise judgment."ngThoe

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Court further alleged that the holding back of the clearance would have been a good example of exercising such judgment. The Court in rejecting the State's contention that the controller had done what was required of him and that he had no further responsibility, declared: "We do not think that this directive was fully complied with where, although a first warning was given, it becomes clear to the controller that another warning was needed and none was given." By this decision the U.S. Courts hold the controller to a standard of care greater than what is set out in his manuals. Care must also be exercised by the controller when using non-standard phraseology. Variation of such phraseology may entangle him in legal implications as happened to the controller in the Case of HARTZ v. U.S. (5th Cir. 1965) who warned the pilot of "prop wash" instead of "caution, turbulence". Such warning was found to be inadequate under the circumstances and the controller was held liable.

Essential Definitions For Those Who Do Read This Magazine Air Traffic Control Officer (ATCO) A shocking type who rushes round a place called a Control Tower or Operations Room, making strange noises and telling flying men what to do. He is, of course, quite incapable of doing it himself and is therefore an expert. He lives in fear of cross winds, weather, clutter, and men ·n cloth caps who earn their living by repairing runways. is a natural pessimist and considers every aircraft a potential 'prang'. For this reason he has little hair, lots of insurance, and no finger nails.

Runway Controller A fast disappearing type (due to the high 'chop' rate) who sits at the end of the duty runway arm.ed with a ~un whose one aim in life, apart from drawing a pension, an d . H · · t prevent two aircraft landing at the same time. e 1s :isoo armed with a red light which he uses during the hours of darkness, and is rather like a traffic signal although most . . dogs would detect a difference. H" un called a Verey Pistol is a cannon-like article i; a lethal weapon if given to idiots. It is .usually accessible to all and sundry. It causes a goodly noise and a considerable smell.

whic~s

He has maintained controllers' equipment all over the place and can remember nights so hot that they had to put water in the petrol, and so cold that even brass monkeys did not like them. Moreover he can remember the time when they flew at night by the light of a blow lamp and a couple of glow worms.

Airport Electrician This type spends most of his time repairing lights and other repairs on the airfield. He is often called out in the middle of the night by the duty ATCO because the lights have gone out on the airfield. After a long drive (he usually lives some distance from the airfield in order to avoid being called out at night), he finds that the night cleaner's duster has caught in the controller's equipment and thus switched the lights off. The Airport Electrician has had more electricity shot through him than an electric railway line owing to the duty ATCO pulling switches while he is mending the lines. He smells strongly of amps and volts and has to wear rubber shoes to insulate his circuit.

Meteorological Forecaster This is another strange type who is beset by charts, coloured pencils which are usually stored in his breast pocket (you can recognise this type off-duty by the coloured streaks on the front of his jacket), and by observers with strange instruments. He is the most consulted man on the airfield after the canteen cook, the most insulted man after the duty ATCO, and the most disbelieved person since Noah. He is considerably hindered by Met. Union rules which forbid him ever to see the weather he forecasts, and for that reason he works in a windowless dungeon. Off-duty he wears dark glasses and is led by an Alsation dog. Met. men base their forecasts on many strange laws such as the one which states that if you stand with the wind blowing to your left you need not put your right hand in your pocket (Austin Reed's Law). There was once a Met. man who gave a correct forecast. His picture hangs in the Met. Head Office, and all forecasters make an annual pil~rimage to gaze on the face of the master to draw inspiration. (Mike Burlyn In 'Transmit')

Luton Tower (female controller): "Roger, Monarch, may I turn you on at five miles?" Monarch captain: "I don't think I have had the pleasure, madam, but you may certainly try." (FLIGHT International)

Senior Maintenance Technician (Avionics) A pretty big shot around the place. He is in charge of the hundreds of white-coat workers who s~arm over th.e He 1s often an Air d uty ATCO tinkering with his equipment. . h . typ e who 1·oined when the Wright Brot ers were in F orce , . f e1·· h' music hall turn, and who did the inspecti~n o 1!a. s chariot before it flew him to heaven. The Senior Techn~c1an does not think much of the duty ATCO - - and considers him to be an unfortunate product of technological developmen. t He has a sleeping dog which he does not like to let lie in case it might wake up, and he applies the same tender logic to the duty ATCO's equipment with interesting results. 8

FAA's Air Traffic Control specialists can look back on 1975 with pride at the 2,877 flight assistance services they provided to distressed aircraft carrying almost 4,800 people. Announcing the statistics, Acting Administrator Dow said many of these people "might have suffered" serious injury or death except for the professional competence of air traffic controllers and flight service specialists who guided them to safety". FSSs logged 1,341 assists, while Towers made 1,114 and Centres made 422. Lost pilots accounted for 1,723 assists, with equipment failure, bad weather, low fuel, and landing gear failing to extend responsible for the others. (ATCA Newsletter)

The Air Traffic Control Evaluation Unit, Hurn Airport, U. K. B. A. Turner, AFRAeS, Superintendent, ATCEU.

The Air Traffic Control Evaluation Un it, Hurn Airport, Bournemouth, U.K.

"The role of the Evaluation Unit is similar to that of a team of pilots and development experts testing a new aircraft. Bringing a complex ATC system or piece of equipment into operation without proper evaluation and familiarisation for the operators would be as logical as loading fare paying passengers into untested prototype aircraft."

Introduction The Air Traffic Control Evaluation Unit (ATCEU) is a branch of the National Air Traffic Services (NATS) of the British Civil Aviation Authority (CAA) . The Unit was originally established as an Experimental Unit at Heathrow in 1947. Work increased and the Unit continued to expand until in 1963 it was moved to larger premises at Bournemouth (Hurn) Airport and its name was changed to the ATC Evaluation Unit. Since then further buildings have been added to accomodate additional facilities, stores and offices. The Unit is established to evaluate and develop techni-

que~ and equipments for future air traffic systems ; to in~estiga~e methods of control necessary to cope with everincreasing ai r traffic density and aircraft performance; to undert.ake the. initial checks of new primary and secondary radar in~tallat.ions; and to collect, record and analyse data concerning aircraft operations into and out of major ai rports in relation to such aspects as minimum noise routes and the flight paths of aircraft over particular local ities. As the number of aircraft under control increases and they f ntrol using extend their capabilities, new method h" t" t d s 0 co more sop is ica. e equipments are required in order to ensure a safe, reliable and timely service. More automation, too, is being progressively introd uced to relieve the workload on human controllers and to improve their traffic handling capacities. But, of course, all devel opments must first be thoro ughly evaluated so that their usefulness and

cost effectiveness can be assessed. It is the task of the ATCEU to carry out these evaluations in t he context of the conditions estimated to prevail over the period when the particular procedures or equ ipments may be in operational service. The evaluation tests can be car ried o ut in one of two ways, either by real-t ime simulation or by fast-time simulation wh ich is a c omputer technique of very quickly running traffic samples through diffe rent airspace set- ups and comparing the delays, conflictions , sector loadings and so on so as to select the most promising ones for further consideration. Real-time s imulation involves the construction of a mock-up ATC system in t he Operations Room. The various sections of t he Unit put together the hardware, softwa re and organisational el ements of an A TC system so as to create, as nearly as possible, a replica of an operationa l system in which everythi ng works as it wou ld do in a real situation. Most of the air traffic control evaluation is done on a real-time simulation basis, and the task of reproducing artificially the many different conditions that might arise in a complex air traffic control system is a maj o r operation involving automatic data-process ing and both e lectronic and human engineering. Associated with simulation exerc ises is the measurement and analysis of wo rkloads on the participants so as to detect any undesirable features or trends. Human factors are becoming increasingly important and are the subject of individual questionnaires.

The Unit also provides facilities for the training and familiarising of existing control staff in the more advanced methods and systems of ATC as they are introduced. It remains in close touch with MOD Research and Development establishments and with equipment manufacturers to ensure that no opportunity is missed to improve the facilities available to Air Traffic Control. In order to carry out its various tasks the ATCEU has installed a great deal of complex modern electronic equipment, and is accepted as one of the most advanced centres in the world for air traffic control simulation and evaluation. The College of Air Traffic Control which is on the same site also makes use of the telecommunications facilities and simulation staff in its vital job of training Air Traffic Control Officers from the United Kingdom and many countries overseas. The programme of Unit projects is controlled by a Programme Review Committee consisting of 11 members from Directorates in CAA and MOD under the Chairmanship of the Director of Control (General). This Committee meets every six months to consider the Unit's current and future programme, and to allocate priorities. Normally a new projeettor the Unit is sponsored at Director level, and the proposal listing the objectives is passed to the Unit for an appraisal as to its acceptability and probable cost. After the proposal has been fully discussed with the sponsor or his representatives, the project in its final form is then added to the Unit programme.

Functional Organisation The operational work of the Unit is split into two main divisions, Executive and Support. The Executive Division carries out most of the projects placed on the Unit and is, in turn, divided into two Groups. One of these is responsible for simulating ATC systems and procedures in realtime in the operations room, and the other for evaluating sub-systems and equipments in the field with particular emphasis on radar calibration. The Heads of the Groups are responsible for the allocation of project leaders and team members to particular tasks. The Support Division, headed by the Projects Manager, provides and co-ordinates all the services and facilities that are necessary for the preparation and conduct of projects. This division includes the Automatic Data Processing Group which looks after computer programming and fasttime simulation and the Scientific Group which analyses data recorded during realtime simulations and supplies observers to record particular controller activities so as to build up total pictures of inter-sector co-ordination and individual workloads. In addition the Scientific Group is responsible for operational research studies of ATC systems in the field. It also uses a mobile tock-follow radar to obtain for later analysis data on the patterns of aircraft performance in the vicinity of major airports. The Support Division is also responsible for the secretarial work of the Programme Review Committee and the promulgation of reports on completed projects. Outside the Executive and Support Divisions are the Telecommunications Group and the Administration Group. The Telecommunications Group provides and maintains all the technical equipment used by the Unit and has a link with the Support Division through the Project Facilities Officer.

Administration The Head of Administration is directly responsible to the Superintendent for the day-to-day administration of the Unit and the provision of all general and domestic support services. The Group is concerned in some way with most of the activities of the Unit and therefore the requirements to be met and the services to be supplied are many and varied. The Group comprises executive, clerical, typing and industrial staff, and their duties include estate, staff housing and restaurant management, works and domestic services the supply of shorthand, typing and photocopying services: and the provision of non-technical stores facilities. Certain delegated financial powers are vested in the Superintendent, and the resulting responsibilities concerning finance, cash, costing and accounting are within the province of this Group. Responsible locally to the Administration Group, but forming part of the CAA Library, is the ATCEU Library. Herein are kept some 600 books covering aviation, telecommunications and automatic data processing; a regular supply of 130 periodicals; 25 continuously updated manuals; a considerable collection of maps; and copies of reports issued by the ATCEU, other government departments, and international organisations.

Executive Division This Division consists of the two Operations Groups which are responsible for the design and conduct of Unit projects. The broad function of Operations 1 is to carry out simulation exercises concerned with new systems, techniques and procedures in as near real life conditions as possible. Operations 2 is concerned with associated subsystems and with radar evaluations in the field.

Operations 1 This Group is mainly concerned with the mounting of real-time simulations designed to examine proposals put forward by NATS Headquarters involving new or revised air traffic control equipments, operations room layouts, techniques and procedures destined after refinement for use at operational ATC Units. Much of the work is concerned with the introduction and development of electronic computers as aids to the air traffic controllers, and is carried out in conjunction with the Automatic Data Processing Group. The Group is staffed by widely experienced Air Traffic Control Officers, both civil and military, one of whom is appointed Project Leader for each project. It is his responsibility to maintain a continuous contact with the Project Liaison Officer appointed by the sponsoring Director so that the simulation satisfies the latter's requirements. He is able to call upon the services of the Project Management, Telecommunications, Scientific and Administration Groups of the ATCEU for advice and assistance in the preparation for, and later in the running of, a simulation. The basic equipment for simulation is the digital simulator incorporating the Ferranti Hermes computer which provides up to 80 controllable simulated aircraft radar responses, together with secondary surveillance radar (SSA) labelling. In some of the more complex projects it is used in conjunction with the Elliott 502 computer which provides the controller with flight data using input and output devices such as touchwire displays, flight progress strip printers and dynamic electronic data displays updated by radar information. It is

The Operations Room of the . RDPS Simulation carried out between April and June 1975. The ob jectives of this si mulation were: ..to investigate the accomodation and ergonomic aspects of the provision of controller operated i nput devices on horizontal suites and the controller workload arising from the input task."

also possible now to use the Elliot 502 computer as a simulator for projects of comparatively limited scope, and ! he ADP Group is providing this service for Operations 1 on an inc reasing number of occasions when the Hermes is engaged on other tasks. The most sophi sti cated si mul ations require three computers working together. A Modular 1 computer drives synthetic Labelled Plan Displays from d ata received both from the Ferranti Digital Radar Simul ator and from the Elliot 502 Flight Data Processor. The Modular 1 also enables a controller to use additional input devi ces such as light pens, rolling ball s, touch sensitive digitise rs and keyboards f~r varying map and l abel content, and for changing label positions. The actual simul ations usually consist of a programme of exercises lasting several weeks and designed to compare a number of alternative organ isations usually arrived at by prior fast-time simulation, or to subj ect a particular org anisation to ever-inc reasi ng traffic and co-ordination loads so as to determine pressure points and capaciti es. The operating positions are manned by personnel in c urrent operational practice who are loaned by field units. Every important aspect is carefully documented, measured and recorded. Much of the data is collected and analysed by the Scientific Group. However, to complement this scientific analysis the ATC officers participating in the simul ation are debriefed verbally, and are required to complete carefully prepared questionnaires. In this respect much valuable assistance is g iven by the RAF Institute of Aviation Medicine in the preparation of questionnaires involving human factors and subjective opinion, and in the su bsequent analysis of answers. Finally, the project is completed by the issue of an official ATCEU Repo rt which sets out the ori inal objectives of the tri al , and describes the equipment ~sed and the ATC system under test, together with its governing rules. It al so exam_ i nes and b~lances s~bj ective opinion in relation to num~ri cal analysis, then discusses the results, draws conclusions and makes recommendalions. Some projects und ertaken by the Operations 1 Group f a number of methods of overcoming are : . t. a) An examina ion o

the problems of SSR label overlap, using a variety of input devices. . b) In conjunction with Eurocontrol , to determine the optimum distance between self-navigated parallel aircraft tracks when radar monitoring techniques are employed to detect and rectify e rrors in navigation. In this project a system which automatically alerts the controll er when an airc raft deviates more than a predetermined distance from its allocated track was also examined. c) Further wo rk designed to provide computer assistance to controllers in determining co nflict free flight paths for aircraft c limbing to or descending from cruising levels. d) A se ries of simulations concerned with the move of certain ATC functions from Preston to the London Air Traffi c Co ntrol Centre. e) An examination of proposed revised procedures consequent upon the provision of a new runway at Zurich Airport was carri ed out on behalf of the Swiss Authorities. f) Vital work co ncerned w ith the desig n of the new Scottish ATC Centre and the progressive development of the London ATC Centre. g) The provision of a realistic ATC environment in which cockpit workloads can be studied in flight simulators. In thi s co nnectio n ATCEU personnel have worked w ith the Concorde Flight Simulator at Toulouse and with Loughborough University of Techno logy in a British Airways Trident Flight Simulator. Operations 2

This Group is responsible for the evaluation of ATC subsystems and for initial flight checks of radar installations at different sites in the U.K. A sub-system is a part of an ATC environment which can be investigated and evalu ated separately, but which can only be effectively used as p art of the whole environment. Examples of this are radar displays, touch di spl ays, headsets, lighting, and the layout of displays, switches and keyboards on ATC consoles. The proced ure for flight checking a new radar installation is briefly as fol lows : First, general cover is investigated for which an aircraft is flown on a specific radial from the radar head at a number of flight levels and to the limit of radar cover. The 11

strength of the echo is assessed for each sweep of the aerial as shown on the display, and a vertical polar diagram (VPD) is drawn. This part of the exercise can involve some 700-800 readings for each run (out and back); usually from 10 to 20 runs are made. The VPD enables the general efficiency of the installation to be assessed, and a typical VPD indicates the zenithal gap (loss of cover when the aircraft flies overhead). The second part of the procedures consists of monitoring itinerant air traffic flying normal patterns, i. e. cruising, climbing, descending, turning, etc. Thus it is possible to evaluate the capability of the radar in an operational role, to note areas where aircraft echoes may be lost because of ground clutter or sub-clutter visibility fading, and to indicate where loss of signal may be expected due to tangential fading. Checks of aerodrome approach radars include observation of aircraft in holding patterns and on approach to each runway direction. In the case of secondary surveillance radars, particular attention is paid to side lobing and the locations of reflecting surfaces liable to cause spurious responses. At the end of a flight inspection a report is produced which states the objectives, summarises the conduct of the trials, comments on any problems encountered and draws conclusions from a study of the observations made. The Group is now increasingly involved in the R.D.P.S. programme and new techniques for evaluation are being evolved. A new development is the u~e of colour to diffe~entiate between types of information on radar and data displays, and this was the subject of an evaluation underta~en by the Group. Various methods of utilising colour displays were tested in a simulated operational environment and the results were sufficiently promising to encourage furt~er experimentation. The colour displays used in the evaluation have been retained by the ATCEU and have been succes~Â fully incorporated in several subsequent tasks not specifically designed to assess the use of colour. In 1974, the Group took over the responsibility for monitoring Concorde sonic booms from R.A.E. Farnborough. This work involves taking recordings of the boom with sophisticated recording equipment placed close to the flight path of Concorde and has been carried out both within the U.K. and overseas. The Group also mans an SSR cell at the London Air Traffic Control Centre at West Drayton which carries out checks of individual aircraft transponder performance when faulty operation is dis~overed. and also checks transponder operation when ~i~o~hmess Division so requires in relation to aircraft cert1f1cat1on.

Support Division The Projects Manager co-ordinates the support services provided by the Automatic Data Processing Group, the Scientific Group and the radar simulator teams, including any of these services that may be required for use by the College of Air Traffic control. He also coordinates the preparation of schedules of operational requirements for the technical facilities to be provided by the Telecommunications Group. In addition the Projects Manager is responsible for co-ordinating simulation and technical s~rvices in the operations room where Unit facilities are being used by the London Air Traffic Control Centre for the training of both new and experienced air traffic control .pers~n~el in the various aspects of the Mediator system. This trammg commitment takes up over half the time availa~le in the operations room, and will continue to do so until the pro12

posed reorganisation of the Unit facilities permits the transfer of this training commitment to the College of Air Traffic Control. The Simulator Services branch of the Support Division is responsible for manning the ATCEU digital radar simulator and the two radar simulators used by the College of Air Traffic Control. Another very important part of the work of the Simulator Services is to devise and compile representative traffic samples in an appropriate form for ATCEU simulations. These must meet the exacting requirements of the Project Sponsor in relation to, for example, numbers of aircraft on specified routes and their various flight profiles, and must also achieve the maximum illusion of reality for the participants. Since these simulations are normally concerned with future events and proposed changes, this work demands a great awareness not only of current practices in aviation in general and ATC in particular, but also of anticipated developments in those fields. All aspects of simulation work require a judicious blend of experience accuracy and imagination. ' The Secretariat of the Programme Review Committee is part of the Project Manager's organisation.

Scientific This Group has two separate responsibilities: a) The numerical evaluation of simulation exercises carried out at the Unit. b) Operational research studies of ATC systems in the field. c) The collection and reduction of data on aircraft behaviour, especially in and around the London Terminal Area. The former Âˇresponsibility results in involvement in the planning, design and conduct of projects from their acceptance until the issue of the final report. In numerical evaluation the Group is concerned to find criteria which allow valid comparisons to be made between various ways of presenting and utilising Air Traffic Control information appropriate to each experiment. Account has to be taken of the inevitable variation in the skill of subjects and the effect of learning during the simulation. The numerical data selected to permit assessments of system efficiency vary with the setting of the exercise. The occupancy time and message count of RT, intercom and Post Office telephone channels are standard sources of data for work-load measurement and are recorded automatically. 'Eavesdrop' facilities aided by closed circuit television enable controllers to be observed so that the amount of direct verbal liaison between controllers can be inserted manually into the automatic recording system. Data on aircraft behaviour (position, speed, height, handover points, etc.), and in some cases on the utilisation of the display and computer input facilities available to the controller, are retrieved from magnetic tapes compiled by the real-time computers. In analysis the Group utilises both in-house and bureau computer facilities, and a library of standard analysis programs is being developed, but these are subject to constant revision and extension to suit new work and improved methods of analysis. The Group has an interest in fast-time simulation which in some cases can be used to extend the findings of the real-time work carried out by the Unit. The Group provides a conventional operational research capability and carries out studies in satisfaction of projects placed upon the ATCEU which are appropriate to that treatment. A recent

Automatic Conflict Detection/Resolution Simulation carried out at the beginning of 1975. This work was done on behalf of the Eurocontrol Agency. The Superintendent of ATCEU, Mr. Basil Turner (right) raises a query with the Project Officer Mr. Phil. George.

example is a study of special Visual Flight Rules (SVFR) operations in the London Control Zone (CAA Paper 75030). The collection and reduction of aircraft flight data varies from the observation of the general pattern of aircraft traffic, to the highly accurate determination of individual aircraft profiles. The equipment which is used in a large part of this work is the RTS1 radar system. This is an X-band lock-follow precision radar with a range of some 50 nm and an accuracy of the order of 3 minutes of arc and 13.7 m (15 yards) in range. Output from the radar is in the form of punched paper tape for computer analysis as well as by automatic plots of aircraft tracks in plan and elevation. This equipment is ideally suited to the examination of aircraft profiles, and typical examples of its application are the examination of take-off flight paths in connection with noise investigations and the determination of track-keeping accuracy between beacons. The equipment is also applied to the examination of traffic patterns when large numbers of individual tracks are built up into a general picture. The Group also accepts ad hoe tasks of a scientific nature such as the continuation of RAE's routine analysis of sonic boom pressure waveforms. To be effective the Group requires a range of knowledge and skills. The members of the Group possess or develop some familiarity with the electronic techniques used in simulation, a general appreciation of aeronautics with particular reference to ATC mathematical knowledge with an emphasis on statistics, ~ome skill in systems analysis, and the ability to program in high and low level co mputer languages.

e. g. those concerned with the implementation of the IBM 9020 D at LATCC West Drayton. b) The investigation of new concepts in the automation of future ATC systems, particularly concerning the means of input and display. c) The routine processing of data for statist ical and analytical purposes. The ADP system is based on a high-speed Elliot 502 digital computer specially designed for real-time, o n-line operations. Linked to t he central processor via a peripheral equipment control unit, the system elements are made up of electronic data-display consoles and teleprinters. Communication with the computer is effected mainly by touch displays and keyboards. The Flight Data Processing System (FOPS) operates as follows : Flight plans are prepared in advance and are entered into the system, either before or during an exercise, by means of punched-paper tape or keyboards. Amendments to stored flight plans may be made through t he touch displays. Information is updated, spread th rough t he system automatically, and cancelled when no longer requi red. Other features of the system incl ude the p rov ision of automatic liaison between certain control positions and the ability to subject clearances to test fo r possible conflict. Some of the activities of t he Group have been: a) The development of t he system in order to simulate flight data and radar data p rocessing for successive stages in the IBM 9020 D development p l an. b) '.h.e investigation of to uch wire displays as input and liaison devices.

Automatic Data Processing

c) The examination of computer derived solution to assist control.lers, such as flow .c,ontrol, outbou nd c ruis ing level allocat1on, computer assisted approach sequencing, track. deviation and conflict predi ction/ reso lution. d) Off-I.me processing of data and statistics, especial ly ai r traffi c movements and airport weather minima infringements.

The Unit's Euc lid computer installation was designed as a self-contained experimental system for investigating im~rovements in data-processing and display, and for carrying out practical work on man-machine relationships. In addition, the system has proved invaluable as a generalpurpose installation for all ATCEU activities requiring computer support or assistance. The pattern of work for the ADP Group may be stated as follows: a) On-line computer support for major si mul ation projects.

e) A small amount of non-ATC work such as stores accounting records. f) The ~xamination of a variety of ATC problems using fast-time s imulat ion techniques. By excluding air traffic controller intervention the simulation process can be 13

made to operate many times faster than in real-time, allowing a traffic sample covering a period of several hours elapsed time to be processed in a few minutes. Numbers of conflictions at crossing points, route loading, etc. can be measured, and comparisons between a variety of route structures can eliminate unsatisfactory organisations at an early stage, thus paving the way to real-time simulations of a small number of alternative solutions to ATC problems.

Telecommunications The Telecommunications Group is responsible for providing, developing and maintaining all the technical equipment used by the ATCEU and the College of ATC. The whole of the telecommunications installation has been planned to give the maximum flexibility of layout of the operating positions. This allows rapid changes to be made in the operations room to cater for the requirements of successive simulations. Eighty distribution panels are located under the floor of the operations room. Each operating position is connected to an adjacent distribution panel by means of a short tail through the floor. The required combination of facilities is provided at each distribution panel by means of relatively simple cross-patching on jackfields. In the operations room up to.190 positions can be provided with simulated RT and telephone facilities. Each position can have access to up of five preselected RT channels; any line on any telephone keyboard can be connected to any other line, and parallel connections can also be made. A 1000-channel digital magnetic tape recording system automatically samples and records, every 0.25 second, the utilisation of all communication facilities at the operating positions. Simulated aircraft responses on the synthetic radar displays are produced by three simulator systems. The largest of these is a digital simulator based on the Ferranti Hermes computer which provides up to eighty aircraft responses as seen by a maximum of four separate radar stations. The aircraft are 'flown' under the control of thirteen 'pilot' positions. This simulator is normally used by the ATC Evaluation Unit and when not required for simulation the Hermes can be used as a general purpose digital computer. It is a 32.000 word machine with a cycle time of 2 microseconds. The system includes a 300 lines-per-minute printer, a four-deck magnetic tape unit and a magnetic drum with a capacity of 256.000 words. The system is interfaced to both the Modular 1 and Elliott 502 computers to allow the simulation of advanced flight plan processing and radar data processing facilities. Aircraft responses for the training of area radar controllers by the College of A TC are provided by a 20-target analogue system capable of simulating three separate radar stations. Training for approach radar controllers utilises a digital simulator based on the Ferranti FM 1600 B computer which provides 18 targets in up to six separate exercises. The system has 24.000 words of 1 microsecond core store backed by 128.000 words of drum storage. Access is available to a 4-deck magnetic tape system and line printer. Secondary radar responses can be simulated on the aircraft generated by all simulators. The 80 target digital simulator can provide labels via 'Digitrace' or the Labelled Plan Display system. The radar display facilities include conventional fluoride-coated displays, scan-converted (or bright tube) monitors, and the 'Digitrace' scan-converted system which is 14

capable of displaying 'labels' indicating aircraft identity and height alongside the aircraft responses. Video maps, angle marks, synthetic aerial turning data and trigger pulses are generated for use by all these systems. A recent addition to the display facilities is an advanced system in which both primary and secondary radar data from multiple sources are fed through a computer and associated with flight plan data to produce a fully-processed picture in which different categories of aircraft are represented by various symbols and on which radar and flight plan derived data can be displayed at the command of the controller. This equipment comprises 12 Cossor type CSD 1000 Labelled Plan Displays with a Computer Technology .Ltd. Modular One computer as the display processor. This computer has 56.000 words of store with a cycle time of 750 manoseconds. A further stage of equipment flexibility is provided by the use· of the systems input changeover rack the use of which allows signals from any of t~e synthetic aerial turning units to be distributed to any simulator, and the outputs from the simulators and video map generators to be connected to any display system. The Elliott 502 computer is used to simulate a flight data processing system . . • to evaluate ATC appl"1cat"ions o f electronic data displays (EDD) and as a . 9enera 1 purpose mach1m~. It has ~4.000 words of one microsecond core store with magnetic tape, and exchangeable magnetic disc s~stem as back-up storage. The EDD system has thirty-six displays of various sizes, including a coloured d" I . sixteen of the displays can be fitted with k isp ay' 't h · •. mas s and used . as ouc wire mput positions Other per"1phe I . · ra equipments include · . . two autonomous EDD • five flight pi an ·mput pos1t1ons, five teletypewriters, used for printing fl" ht . . 19 progress strips .·· . and. a 300 Imes-per-minute printer. Oth er fac1ht1es available include a graph plotter, audio record d · •t . . ers an two c Iose d c1rcu1 telev1s1on systems The Grou 1so controls · P a . a d rawlng office and a workshop with fac·11·t· f d . 11es or wood an metal-working, and for servicing mechanical devices. The Group includes a programming sect· ion responsible for the software of the digital radar simulat d . or an processed display computers, and of technical evatuat"1on . t ·· d ata processing facilities. pro1ec s requmng . The requirement to carry out complex real-time simulations. of, for example ' radar data proces smg . an d conflict detection and resolution systems has result d . • • • e m a necessity to msta1I improved computer facilities. Plans are now well advanced for the Introduction of modern, fully compatible hardware and a high level language (Coral 66) which will offer greater overall capacity, much enhanced realism reduced exercise preparation times and improved facilitie~ for quick _scientific analysis of recorded data.

Conclusion During the last 10 years the Unit has carried out and reported upon some 200 projects, most of them sponsored by NATS Directorates. However, others were sponsored b for instance, the Eurocontrol Agency, Ministry of Defe y, foreign ATC Authorities, the Royal Radar Establishmen~c=~ Malvern and the Department of Trade and Industry. The current staff strength is about 270 of whom 60 vide services to the adjacent College of Air Traffic Co ~rol lt can reasonably be claimed that they represent a br n ~~h of expe~ien~e of real and simulated Air Traffic c:~trol work which 1s a powerful force for the sound development of future systems, procedures and new facilities.

Integration Of SST Operations In The Non Sophisticated ATC Environment~ by B. J. Plimmer, Controller Air Traffic Services, International Aeradio Limited

BAHRAIN FIR

CONTROLLED AIRSPACE

BAHRAIN/DHAHRAN CTA 1000 FT.-Unllmltod BAHRAIN/DHAHRAN CTR MSL-3500 FT. ABU DHABI. DOHA fr DUBAI MSL-Fllght Level 05 SEED CTR MSL-Rlght Level 75

CTirt

-t Much has already been written about ATC and the Supersonic Transport. It is not Intended to try to offer a new approach to the problem, presented by the requirement to Integrate this new generation of aircraft Into the existing system. On the contrary, It Is Intended to relate actual experience already gained from integrating an SST aircraft into an existing non sophisticated ATC System.

SST Routes It is accepted that due to the restrictions imposed by the need to comply with various national requirements to avoid supersonic flight over populated areas, significant portions of the proposed world-wide SST routes will be over water, deserts and sparcely populated land areas. Inevitably these will be areas in which the ATC environment is comparatively non-sophisticated. One of these routes is the likely British Airways Concorde route to Australia from London via Bahrain and Singapore to Melbourne. Thus Concorde, the first of the Supersonic Transport aircraft, will begin and end its London to Australia journey in a sophisticated ATC environment. At the London end in particular, it will have been the object of much pre-planning and special ATC handling, a very necessary requirement in a high density air traffic area. By comparison the greater part of this route is through non-sophisticated ATC areas. * Revised version of a paper which was presented at Convex '74, the Convention and Exhibition held at Bournemouth In October 1974 under the auspices of the British Guild of Air Traffic Control Officers. It is published in this Issue of ,,The Controller" as a follow-up to the article in our February 1976 issue, describing the SST simulation work which was carried out In a hlghly sophisticated ATC environÂˇ ment (Western Europe).

The specific portion of the Concorde's eastern route, that it is intended to cover, is that part which passes through the Bahrain FIR and particularly at the transit refuelling stop which will be made at Bahrain's International Airport.

IAL's Involvement in the Bahrain FIR You may well ask, what is IAL's involvement here? The answer is that we are in the unique position of managing the Bahrain FIR. We do this by operating, on behalf of the Government of Bahrain, the Air Traffic Services at Bahrain International Airport, including the running of the ACC, hence we have the overall ATC responsibility for this FIR. The importance of the airways system which runs through the Bahrain FIR is great. This forms part of the major routes from Europe to the .Far East and is currently used by almost 100,000 aircraft a year. Our first exposure to SST operations was in June 1972, when Concorde 002 transited in Bahrain on its flight from the U.K. to Japan. Prior to this flight, information on SST operations was comparatively scarce and almost wholly theoretical In respect of hot airfield operation. Transonic acceleration and deceleration phases were unfamiliar terms and the questions were firstly, how would we fit this totally new concept of passenger aircraft operation into the existing system, and secondly how would we integrate Con15

Controllers at work at Bahrain Area Control Centre.

corde with the normal subsonic air traffic during the inflexible transonic phase of its flight without the benefit of radar cover? To amplify the problem with which we were faced, perhaps it would be as well to briefly describe the airways structure, general traffic flow and navigational facilities within the Bahrain FIR which existed at that time.

The Bahrain FIR The orientation of the airways system was and still is, east/west. East of Bahrain .thege airways are mainly over the waters of the Arabian Gulf and, in the east they converge over the Dubai VOA. The majority of eastbound, long distance flights occur at night, having departed from Europe in daylight, a nu mber of these transiting at airfields within the FIR. This flow is reversed during the morning and the main traffic becomes westbound. The majority of navigational aids within the FIR are sited on airfields serving both an enroute and approach function . In 1972 these consisted mainly of VORs with a sprinkling of NDBs. The only radar east of Kuwait was the approach radar at Bahrain. This radar having a maximum theoretical range of 75 nautical miles, the critical transonic acceleration phase would commence outside radar cover and this appeared to present the major problem. The transonic deceleration phase would be co nducted at levels above subsonic aircraft cruising levels and Concorde would be subsonic before reaching these flight levels. The first encounter with the SST is summed up in the following extract from a report on the operation. "Concorde 002 arrived in Bahrain subsonic from Teheran. On departure for Bombay the Area Controller had the 'interesting' experience of being one of, if not the, first ATCO to have to provide a procedural clearance for a SST for the inflexible transonic acceleration stage into a supersonic climb on Airways. 002 passed Mach One about 85 miles out passing FL 295. A very short time later it crossed Dubai passing FL 495, and passing Mach 1.9, it shot out of our airways into the Bombay FIR at FL 520 at just over Mach Two.ÂˇÂˇ

1974- Second Exposure to the SST With the 1972 experience behind us, we faced the prospects of the Concorde's high ambient temperature flight trials which were carried out, in Bahrain, in August and September 1974, with less trepidation. The programme, in addition to the trials included supersonic demonstration flights from several airfields within the FIR. We had available to us now, a wealth of information on ATS planning for SST operations. In addition there had been a vast improvement in the navigational aids within the Bahrain FIR, with the introduction of VOR/DME's at Bahrain, Doha and Seeb, an airport which had barely existed in 1972. The most important innovation was the long range surveillance radar at Dubai, with a range of 150 nautical miles. In planning for these SST operations it was decided that we wou ld endeavour to comply with a preference tor an INS departure track. In addition it was planned that the trial flights would take place during the quiet afternoon period, and the demonstration f lights would be timed to take place in the morning, after and before the east- and westbound "rush" respectively. Because of the fuel penalties which would be imposed by delays on the ground it was decided that start-up clearance, taxi- and take-off clearance wou ld be issued by the Area Control Centre in conjunction with Bahrain Aerodrome Control. Start-up clearance was to take into account, not only the entire clearance for the transonic acceleration phase but also an unrestricted taxipath and take-off. The instruction issued to cover this was qualified by the " tongue in cheek" comment, "other aircraft should be delighted to delay and observe the high speed take-off". In order to achieve this it was to be assumed that the aircraft was "in the system" 15 minutes before start-up.

Separation It was planned to allow the aircraft an uninterrupted climb on a steady track. With the high rate of climb and preferred INS track offset from Airway Amber One, coupled with the use of Bahrain radar it was hoped to be able to achieve this. On Airway Amber One in the Sector Bahrain

- Quebec, separation would be achieved by the use of the VOR, Radar or DME in the case of eastbounds only. Westbound aircraft routing Airway Amber One and east of Dubai at ETD would be vectored by Dubai radar on to a s uitable Bahrain VOR radial until vertical separation was achieved. Radar separation, normally 5 n. m. would be increased to 10 n. m. whenever Concorde was involved.

Communications Âˇ Despite an extended range VHF system beamed eastwards from Bahrain, air/ ground communications are normally difficult in the eastern extremity of the FIR, since they rely on HF R/T. This presented a problem and it was decided to use the ATS SSB HF network, if it was found difficult to maintain contact on HF R/ T, when the aircraft was outside VHF range. As this network is an internal FIR one, Bahrain being the master station, this had the advantage that a number of ATSUs, in various locations would also be listening out on these frequencies thus improving communication prospects. Another problem presented by the peculiarities of HF, was the possibility of not being able to effect adequate liaiso n with contiguous FIRs to east of the Bahrain FIR. The planned demonstration flights from Dubai and Abu Dhabi Airports were to enter both the Bombay and Karachi FI Rs.

Concorde at Bahrain"s International Airport.

Initially, problems were encountered in maintaining contact with the aircraft but these were resolved. As an additional back-up to the communications system, it was arranged to use the RAF HF flight watch frequencies on the Gan, Akrotiri and Masirah network, particularly if an emergency s ituation occurred; fortunately it was not found necessary to resort to this alternative.

Conclusion Outcome The flight trials presented few problems, primarily because their timing enabled them to be carried out after the busy morning traffic period. When the occasional potential confliction occurred it was found easier to resolve than we had anticipated, by using standard longitudinal and VOR separations for which, in the case. of the former, the unfailing accuracy of the aircraft's estimates was a great help. When applying VOR separation, it was necessary to in struct Concorde to establish on the required radial, otherwise it would fly the preferred INS track. The expected fifteen minutes warning of start-up was not always given. For example, following one engine ground run , clearance was requested with the aircraft ready to taxi immediately; on this particular occasion DME and the Concorde's high rate of climb ability was used to ensure the aircraft had an uninterrupted climb through other eastbound aircraft levels. Take-off, in this case, being within five minutes of the clearance request being received . The preplanned preferred INS track was found to satisfy the requirement to comply with noise restrictions, to avoid inconvenience to other airspace users and to keep the aircraft with in controlled airspace during the critical transonic acceleration phase. In all , Concorde proved to be much more flexible than was expected and its performance bettered the figures given in the Flight Profiles in !CAO Circular 109-AN/82. A number of the supersonic demonstration fl ights, from airfields within the FIR, were provided with radar service by Dubai Radar. Separation during both the transonic accelerati on and dece leration phases was provided and to quote from their ATC Report "proved most interesting". One pi ece of information derived from these flights was th at the radar upper cover is at least 60,000 feet!

One must not lose sight of the fact that we were dealing with a single SST aircraft, so that many of the procedures which were adopted may not hold good where more than one SST is involved. However, we have shown that those non-sophisticated FIRs faced with the prospect of limited SST operation through their airspace can introduce procedures for handling the aircraft which will be acceptable to all airspace users. As far as the Bahrain FIR is concerned , by the time we are faced with the task of handling a number of SSTs, the essential additional secondary and primary radar cover will be avail~ble. This is planned for implementation in 1976 when Bahrain will have a modern long range radar.

Postscript During 1975 Bahrain's Air Traffic Control Units have had further opportunities to gain additional experience in handling the SST, as Concorde has been a regular visitor to the Gulf, being based at Bahrain's International Airport in July 1975 as part of the proving and endurance trials. The following extract from a report made at this time reads "Concorde has been operating In and out of Bahrain during the month and the more it is handled the easier it appears to fit in with subsonic flights in the Area". This additional experience In handling the SST has provided the ATC units at Bahrain with the opportunity to consolidate the experience gained earlier and will ensure that the scheduled Concorde services, which will have started by the time this article is read by readers of "The Controller" , are integrated into this relatively non-sophisticated ATC environment in a safe, expeditious and orderly manner. 17

The Provision And Use Of Information On Air Traffic Control Displays (I) by V. David Hopkin, R.A.F. Institute of Aviation Medicine, Farnborough, U. K.

Summary

Task Design

Several kinds of mismatch can occur at the inanmachine interface in Air Traffic Control systems. One, often overlooked, concerns the provision of certain essential information in a form which is unusable. A technological advance need not convey human factors benefits. Novel display techniques may embody relatively obscure human factor problems which emerge only at a late stage in display development. Evaluations of innovations may inadvertently be biased by emphasising known merits without revealing hidden inadequacies. The traditional reliance on the man's strengths of adaptability and flexibility in order to match man and machine in the system is thwarted if he cannot use the information presented to him. Changes from qualitative to quantitative information, incomplete automation, and the apparent retention of decision-making rolesÂˇ which in fact have been greatly modified, all pose problems of ensuring that the displayed information has been adapted successfully and can still be used. Because such changes alter the role of human memory and attention, these must be aided and supplemented in new ways. It is hoped that problems of this kind will arise less frequently in the future, if their existence is demonstrated now.

The Purpose of the System

Introduction

Definition of Tasks

The purpose of drawing a distinction between the provision of information on Air Traffic Control displays and the use of that information by the controller is to demonstrate that this distinction exists and is important. Numerous problems in current systems originate in failures to acknowledge this distinction or to take account of it. Many proposals for future Air Traffic Control systems, and especially for automated assistance to the controller, blur this distinction to the extent that information may be presumed to be usable just because it is provided. As a system evolves, the role of each man in it, and the demands of the system on him, may change. Information of proven adequacy in a previous system may not remain so after the system has been revised, because of quite subtle changes in the man's role or in the demands on him. He may have to match the machine in different ways to fulfil the same functions as before. Providing information and using information are separate functions. Information must be compatible with man's abilities and limitations if it is to be used as planned. Information which has hitherto been used satisfactorily may become inadequate if the man must acquire new skills in order to adapt to system changes, with the result that the form and content of displays may have to be revised. The incomplete automation of a function may entail the overt display of supplementary or explanatory information, formerly acquired as part of a manual process. Such implications of system changes become apparent when a distinction between the provision and the use of information is drawn. but may go unrecognised without it.

Once such difficulties have been overcome, a process of refinement takes place whereby the tasks and the equipment necessary for each function are progressively defined in more detail in relation to human capabilities on the one hand, and to the already available, or potentially available, equipment on the other. During this stage, too, it may become apparent that certain tasks cannot be done well enough to reach acceptable operational standards, with the result that some limited system re-design to remove or modify such tasks may be needed. Alternatively, a decision may be taken to reduce the operational standards, or to accept human limitations in performing functions which cannot be fulfilled In any other way. For example, a human monitoring function may be retained in the full knowledge that man is relatively inefficient as a monitor, because no alternatively practical way exists of fulfilling the monitoring function. Also, it may be decided that supervision of a particular task is desirable, even though it is conceded that none of the facilities necessary for effective supervision, such as more accurate, fuller, or more up-to-date information, greater knowledge or skill, or access to additional data sources, are likely to be present, and that fully effective supervision cannot therefore take place.

The procedures which should be followed in designing tasks for new Air Traffic Control systems are now well established and are described in references on task design (1 ), although they are not always adopted in practice. Beginning with the stated purpose of the system, it is possible to deduce the broad functions which must be performed within the system in order to fulfil its purpose. Knowledge of the technical facilities which will be available, and knowledge of the basic capabilities and limitations of people, together enable decisions to be reached on which functions are suitable for a man and which for a machine. Such decisions are of course substantially determined by the current state of reliable and cosH~ffective technological development, and are not solely or even mainly determined by human factors. As a result, some of the functions allocated to the man may not be those which he can do well, but merely those which a machine cannot do at all. At this early stage in the system design, it may become apparent that certain functions can never be fulfilled to the required operational standards within the envisaged system, and the principles for designing the system may therefore have to be re-cast to exclude such functions.

Grouping of Tasks After the preferably in the grouping a task refers

tasks to be performed have been specified, relation to the facilities needed for each one, of tasks into jobs take place. In this context to a function prescribed by the system, and a

job refers to all that one person does. Almost invariably in an Air Traffic Control context, each job consists of several tasks and often of many tasks. Numerous factors have to be considered in the grouping of tasks into jobs. There is no point in designing a job which would require far more facilities than could be physically accomodated within the workspace of one man. An obvious preference is to group together tasks requiring similar equipment and facilities, since this will enable one man at a single operating position to perform many functions with a limited range of equipment. This ideal may be difficult to attain if it conflicts with another important factor, the relative timing of various tasks. Often certain functions have to be performed in a fixed sequence, while other functions have to be concurrent with them. If a system is to be efficient, its design must not allocate to one man two functions which must be performed concurrently but which he would have to do sequentially. However, if two tasks could be done by one man at the same time, either because one of them is over-learned or because frequent attention-switching between them is possible, it may then be advantageous to allocate both to him. A further requirement is that the functions allocated to one man should not demand skills and abilities which are incompatible, or sufficiently disparate to occur rarely in the same person. Problems of this kind have occurred, and still occur, in Air Traffic Control, particularly associated with jobs which combine a large element of routine data entry through a keyboard or similar device with the occasional need for correct, urgent and highly responsible decisions that cannot then be revoked. The skills and abilities required for the former function, such as manual dexterity and a tolerance of routine work, are very different from those needed in the decision making role: a man saddled with such a job may be either good at decision making but frustrated by the routine data entry task, or good at data entry but inadequate at decision making. Being good at both requires a rare combination of talents. Therefore, whenever possible, it is prudent to design jobs so that all the skills and abilities which they require have a high probability of being found in one person.

Existing Skills Designing a new or revised Air Traffic Control system is not done in isolation. Most of those who will have jobs in the new system are already working in existing ATC systems. They have been selected because they possess certain abilities, interests and aptitudes; they have been trained to use these and to acquire relevant skills; they meet the norms and standards expected by their professional colleagues. Their existing jobs are sources of job satisfaction, responsibilities and status. One issue which is not always considered is how far the designs of new tasks should be modified to enable existing skills to be perpetuated in them or adapted to them. If a task is designed solely according to criteria of system efficiency, where efficiency is assessed by direct and quantitative measures relating the input to the output, resultant changes in skills and responsibilities, and hence in job satisfaction, may go unrecognised until it is too late to retain them (2). Thus in the initial design of tasks, in the allocation of tasks to man or to machine, and in the grouping of tasks into jobs, it is important to bear in mind the implications of any changes on skills and on opportunities to exercise skills. System dependent measurements may not acknowledge the relevance of

these factors or may be inadequate to assess them, and so no relevant quantitative data on these factors may be available to influence decisions on whether changes should be introduced. Almost all proposed task changes affect skills and responsibilities, and therefore they should be evaluated in these terms as well as in terms of system efficiency (3).

Established Traditions Some procedures and standards of performance have become established traditions. They may therefore remain unquestioned. Many originated in systems which were primarily manual, in circumstances when human factors advice was not available. At the present time and in the context of modern knowledge, they can seem odd, irrational and inefficient. However, people cherish traditional ways, which should not lightly be disrupted or discarded. This does not imply that traditions should never be changed, but it does imply that such changes need to be well-founded and persuasive. Their proposed introduction may encounter stiff resistance and be interpreted as unwarranted interference with established rights and responsibilities.

Workspace Design When tasks have been correctly grouped according to the whole range of relevant factors, the design of the workspace for each individual controller can be undertaken. The processes of designing the tasks and of grouping them into jobs reveal what information must be displayed at each working position, which controls are necessary to perform the tasks and what communications are needed. The facilities required by each controller depend not only on the grouping of tasks into a job, but also on the intended relationships among jobs. If some operators are expected to work as members of a team, their jobs must be designed accordingly. If some operators are expected to share facilities, the workspace layout must enable this to be achieved. If an operator is expected to be self-sufficient, his workspace must be designed to enable him to work independently of others. In some jobs operators may in principle communicate either via the machine using displays and controls, or verbally by telephone or R/T facilities, or face-to-face. How they do communicate depends on task design and workspace layout. The designs of tasks and of jobs are influenced by the ways in which the jobs interact. Whether a function can be performed by a team is determined by the relevant task and job designs; the efficiency with which the function is actually performed depends on the specification of the workspace of each individual controller and of the facilities essential for him. When all the decisions have been taken about the f ._ ac1 . d . lities needed, the workspace is es1gned. The broad _ pects of the workspace are decided first. These include ~se size and shape of the room, the number of operators . th . relative . Io.cat"ions, the provision Of in e room and their 路 d"1sp 1ays f or severa 1 people and of a general information .t b . t . h' h . su1 a le physical env1ronmen m w 1c to view and use them, the arr~~gements .for .watch ha~dover, for maintenance and for training, the lighting, heating and ventilation n d f I heme d 路 ee ed, the h 路 c 01ce o co our sc s an visual textures, and aesthetic factors. Further factors associated with the k" . . . . wor mg environment but not within 1t, such as off-watch fa ... should also be considered. ciltties, It is then possible, having established th b d 路 . . e roa principles for the design of the workspace, to plan the work-

space of the individual operator. The layout and profile of suites and consoles are determined on the basis of anthropometric data Displays and controls are located in the console according to standard principles for workspace layout, reflecting the influence of utility, previous experience, proficiency in use, and display-control relationships. Checks are made to verify that all controls meet the ergonomic requirements for reach distances, that displays are at optimum viewing distances in relation to their contents, that the lighting levels of all surfaces and of general and individual displays are acceptable and compatible with the ambient lighting in the room, that the location of individual displays and controls reveals the relationships between them and their relative importance, and that any functions to be done by teams are fostered by the workspace layout. At this stage, the effects of other factors on individual workspace are considered more specifically. These include seating, airflow, and the optimum positioning and adjustment of each light source to match the displays and the environment, and to minimise undesirable glare and reflections. Only after all this has been done is it worth embarking on the final phase of workspace design, which is to optimise the detailed design of each item of equipment in relation to its known location, use and physical environment. Therefore problems such as the optimum design of an input keyboard should be tackled last, after its location in the console, its physical environment and its intended use are known. Similarly, the designs for the content and layout of information within each display, such as the size and font of alphanumeric characters, can be optimised only when all broader issues about workspace have been settled (4,5). The above protocol refers to the correct sequence for stages in design: it does not entail the building of each stage before the next can proceed.

Mistakes in Design If the above procedures are followed correctly throughout, the outcome is a system '-de~ign which fulfils the basic functions within the system successfully, and which contains a series of correctly related jobs, each of which consists of a sensible clustering of tasks. Each job is placed in a congenial and efficient working environment where all the necessary facilities are to hand. By using the operator's existing skills and abilities and by not expecting him to perform functions which are fundamentally unsuitable for him, each job provides an approximation to an optimum work situation in terms of functions, tasks, physical workspace and well-being. Obviously even if these procedures are followed correctly and conscientiously, mistakes can be made. Since many of the procedures are seldom followed at all, mistakes can be expected. This paper, in tracing some of the mistakes which do occur, puts particular emphasis on some which often go unrecognised but which nevertheless are predictable.

Evaluation Procedures Simulation When a system has been designed, several evaluation procedures can be applied to it during its evolution (6). The simplest of these are pencil and paper studies to establish whether envisaged tasks can in principle be done or will encounter basic limitations, associated for example with information processing, or perceptual judgements.

Next may come the simulation of chosen functions to establish their feasibility, to gain some inkling of the attainable standards of performance, or Jo develop training, instructions or procedures conductive to the efficient performance of each task. The concept of simulation itself covers a wide range of complexity. At its simplest, only the rudiments of one task forming part of an operator's job may be represented. At its most complex, a whole system, or a very substantial part of a system, may be replicated with great fidelity to answer questions about relevant interactions and cumulative effects which may occur when the system becomes operational. Simulation has some fundamental limitations: it is never possible to replicate every aspect of an operational system; random variations in real life usually must be constrained in simulation to enable the effects of experimental variables to be demonstrated; operators participating in simulations may have no real-life experience of the system being simulated. Since these flaws in simulation usually are present under all circumstances, it often proves to be a tool which is more valid for comparative assessments, for example between alternative displays, controls, instructions, or procedures, than for absolute measures, such as attempting to determine the traffic capacity which an operational system will have.

Field Studies Beyond simulation are field studies, using real aircraft for the purpose of gathering data about the Air Traffic Control system. Such studies are comparatively rare; they are very costly, administratively unwieldy, and constrained in the factors which can be studied by the need to maintain safety and efficiency while measurements are being taken. Whenever studies in Air Traffic Control are conducted using real aircraft, difficulties are encountered in controlling variables suffici~ntly well to enable any discovered effects or differences to Âˇbe ascribed correctly and without ambiguity to their causes. However, evidence from operational systems, often initially in an anecdotal form, may give the first indication that a mistake, undetected in previous evaluation procedures, has been made in the design of the system, of jobs, or of tasks.

Descriptive Techniques Other evaluative techniques are available which do not rely on real-time experimental methods. These include fasttime simulation by means of which the implications of a change in a single variable or group of variables can be predicted. The most important variables can thus be defined and the interactions among variables explored. Usually the human operator has to be represented in over-simplified terms, and the variability he introduces both in improving and degrading system performance is often underestimated. Techniques such as the compilation of flow diagrams permit the envisaged or actual functioning of the system to be described in a form which is reasonably intelligible to everyone (7). These techniques may be used with great ~enefit to obtain definitive statements and descriptions of Jobs and tasks, and to reveal functions which appear to be redundant. A seriously neglected technique in Air Traffic Control is the compilation of detailed job descriptions. The need for these is often expressed and their lack deplored, but

the impetus to compile them appears to be lacking, perhaps because a good job description demands a great deal of painstaking work jointly by controllers and human factors specialists.

Standard Recommendations Another evaluative procedure consists of the testing of proposals by comparing them with established objective recommendations. The correctness of many ergonomic aspects of the workspace of an air traffic controller can be verified using handbook data (4,5). Some data, for example on reach distances, viewing distances and the location of displays and controls, can be applied in a straightforward way. Other data need to be interpreted with caution if the conditions in the ATC environment differ from those envisaged by those who compiled the handbooks. The main sources of differences which discourage an uncritical acceptance of handbook recommendations include factors associated with the operators, such as eyesight requirements; factors associated with the physical environment, such as specialised lighting; factors associated with the tasks, such as consultative and team decisions; and factors associated with working conditions, such as shiftwork. Nevertheless these factors would generally require a modification of existing ergonomic recommendations rather than completely invalidate them. Evaluative techniques associated with ergonomic requirements include ·physical measurements, e. g. of lighting levels; photography, e. g. of typical postures adopted while working; and film or videotape, e. g. of head, eye, and hand movements.

Subjective Assessments A further evaluative procedure is subjective assessment. The most common form is questionnaires, but case studies, interviews, de-briefing, and discussions may also be used. More general information on the subjective attitudes of the controllers may be obtained less directly by studying factors such as their relations with managements and the recurrent themes in their professional literature.

Further Techniques Finally, evaluations may employ numerous other kinds of relevant data. Physiological or bio-chemical indices may disclose effects in terms of the effort which a controller has to make, when no corresponding effects are apparent according to performance measures. The incidence of stress-related illnesses may reveal effects of system changes on the controllers. Data on absenteeism, morbidity rates and mortality rates may also be relevant. Certain reoccurring medical problems, associated for example with elaborate visual corrections or with postural difficulties, may point directly to the effects on the controller of ergonomic deficiencies in his workspace.

Findings from Evaluation Evaluation can show if a task is feasible and can suggest what level of performance will be attained. It can verify that the information needed for the task is present at the workspace. It may also show that although the necessary information is present, the man apparently cannot use it. Possible explanations are that he does not understand it, that its relevance has not been explained, that his instructions have been inadequate, that his training has been in-

complete, that some aspects of his procedures are wrong, or that he cannot process or interpret the information in the ways which had been envisaged. It is therefore not enough to show in the task design that all the information needed for a task is present. It is also necessary to ascertain that it is in a form which the man can use sufficiently well to meet the required operational standards.

Mismatches Between Man and Machine Inadequate Information If failure to perform a task adequately can be traced to inadequacy of the displayed information, this can occur at various stages in the evolution of the ATC system and in several ways, some of which are much better known than others. At the simplest level, a task analysis may reveal a mismatch between the man and the machine because the machine does not present to the man all the information which is necessary to enable him to do his task. Many examples of this have occurred in the past, often associated with the detection and identification of information on primary radar displays, where the man was expected to act on subtle differences within the information presented in the absence of unambiguous visual counterparts of those differences. A more common example nowadays occurs at intermediate stages during the development of various forms of computer assistance, when the limitations of software or of hardware do not enable all the distinctions and classifications to be made which the man needs to know and which he has come to rely on in the performance of his task. If this happens the man may view the aid as inadequate because it fails to draw distinctions which he is accustomed to make, or because it adopts a classification of data with which he is unfamiliar. Because it is almost impossible to automate any manual function in its entirety certain information is likely to be no longer available when an automated aid is first introduced. This applies most commonly to qualitative information. It .may not be immediately apparent that such information has been inadvertently omitted since in any relevant evaluation the findings will have been expressed primarily in quantitative terms. The outcome, however, is that the machine does not present to the man all the information which he needs, since it is mainly restricted to the information which can readily be quantified.

Changes In Decision .Making A further source of mismatches between the man and machine derives from the generally incomplete automati . ft . on of functions. This problem 1s o en associated with attempt to assist the man's decision making and problem solvin s Numerous specific examples of such attempts occur at thg. present time in ATC system development, includin t e · · g au 0 mat ed con ft"1ct d et~ct1on an d reso Iu~1~~· computer assisted approach sequencing, auto-alert fac1llt1es, flow cont 1 the provision of alternate or parallel tracks. Thes r~d· and . t d d . 'd t h e a1 s are m en e to g.'v~ gu1 an~e o t e man, and sometimes to formulate dec1s1ons for him. Often they replace h" · · d ec1s1on ma k'mg w1·th a so 1ut·ion presented by th is human which the man may accept or reject It is co et computer, . · n ended that this stratagem enables the man to retain his d .. • 1 b t · f · ec1s1on making ro e, u in act ~ different decision making function . . . has replaced the previous one. This has ma· JOr 1mpllcat1ons for the man, and new problems arise in mat h' h" bilities with those of the machine. c mg is capa-

If a man reaches a decision unaided, for example about approach sequencing or conflict resolution, he knows and remembers which factors he took into consideration in arriving at his decision. Because the decision itself is the product of an active weighing and manipulation of the variables which he believes to be relevant, he recalls not only his decision but also his reasons for it, and the factors which did or did not influence him. If this function is replaced by a solution presented automatically, he may accept it or reject it. If he accepts it, he may have difficulty later in recalling what it was, as he took no active part in formulating it. If new information subsequently becomes available, he has no means of knowing whether it warrants a re-examination of the decision. To judge this, he would require an understanding of all the factors which have influenced the computed solution, together with a knowledge of their relative importance and of the conditions which must be met before each is included. The man cannot know whether new information has already been allowed for in the proposed computed solution: for example, has a proposed conflict resolution which he had already accepted taken account of a new aircraft which is being handed over to him? His functions have thus been radically changed: his role may no longer be clearly defined in relation to the Âˇ machine, or fully compatible with it. The man may be unable to make sensible judgements on whether he should accept, reject or modify solutions or decisions by the machine because he is not well enough informed about the factors which the machine has included or omitted. It is not apparent to him from the appearance of the displays, or from the way in which the machine performs, how it reaches its decisions. A man who is matched with the machine needs to know a great deal about how it works, much more than he normally knows now. This information is available within the system but is not accessible to him and therefore cannot be properly used by him. Little thought appears to have been given to how it might be displayed in a usable form.

A Residual Problem Many of the commonest sources of human factor problems in Air Traffic Control systems have been mentioned above in relation to task design, evaluation procedures, or mismatches between man and machine. However, it is possible to overcome all the above problems and still to find that the man does not use as envisaged the information presented to him on his displays. Situations can occur in which all the information shown by a task analysis to be necessary is depicted on displays, in which the man is given an adequate knowledge about the machine to enable him to respond sensibly to it, in which all the information is presented in an ergonomically acceptable form, in which due acknowledgement is paid to the need to make the displays and the job acceptable to the man, and in which still the man apparently cannot use the information. Usually when this happens the information is being presented in a wrong form for the man to understand and interpret in relation to his tasks. (The second and concluding part of this paper will be published in our next issue)

References 1. H. W. Sinaiko & E. P. Buckley: Human factors In the design of systems. In H. W. Slnalko (Ed.): Selected papers on the design and use of control systems. New York: Dover Publications, 1961. Pp. 1-41. 2. V. D. Hopkin. Conflicting criteria In evaluating Air Traffic Cor1trol systems. Ergonomics, 14, 5, 1971, 557-564. 3. V. D. Hopkin. Designing controllers' tasks in relation to human capabilities. Munich, 1973: Paper to 21st International Congress of Aviation and Space Medicine. Also: Farnborough, RAF Institute of Aviation Medicine Sc. Memo. No. 114. 4. E. A. Bainbridge. Human factors In the design of consoles. UK Flying Personnel Resean:hÂˇ Committee FPRC Memo. No. 179, 1962. 5. H. P. Van Cott & R. G. Kinkade. Human engineering guide to equipment design. Washington DC: American Institutes for Research, 1972. 6. D. Meister & G. F. Rabideau. Human factors evaluation in system development. New York: Wiiey, 1965. 7. V. D. Hopkin. Flow diagrams. In R. K. Bernotat & K. P. Gartner (Eds.): Displays and controls. Amsterdam: Swets and Zeltlinger, N. V., 1972. Pp. 191-212.

Acknowledgement

Deficiencies of Presentation A further mismatch occurs when there are deficiencies in the ways in which information is presented. In such cases all the information needed to perform a task may be present, but unsatisfactory features of the workspace design may render it unusable. Perhaps there is simply too much information, with the result that some tasks which could be done would take so long that they are never done at all or are skimped. Perhaps information sources overlap, as with labels on radar displays, so that the information becomes unsuitable or subject to error although it is present. Disparities may appear among displays purporting to show the same information. Information which can readily be found may still be presented in an inefficient form: it may be alphanumeric when it should be pictorial, or vice versa; it may employ characters or symbols which are too small, badly formed or misleading in their positioning. Poor display contrasts and brightnesses may reduce legibility so much that errors are made. A mismatch between the display illumination and the ambient lighting may have similar effects. Whatever the cause, the result is that certain information which is present is not used because it cannot be seen, or cannot be read, or is too cluttered, or too inconsistent.

This paper was first published by the Advisory Group for Aerospace Research and Development (AGARD), NATO In the Proceedings of the 20th Meeting of the Guidance and Control Panel on "Plans and Developments for Air Traffic Systems". Cambridge, Massachusetts May 1975.

Have you noticed the trendy American use of the word 'Sir' in R/T speech? One of the trendy-speakers, after hearing "Thank you sir, Alpha Bravo over Abbeville at fife niner, sir, estimating Chorley Wood at zero niner, sir, good day, sir" started punctuating his pattern with "Madam." There was an embarrassed silence, followed by a French voice saying "C'est vrai, je suis dame!" (FLIGHT International)

* * * "What do I think of the F-16? Let me tell you a little historical story. In 1928 the French Air Force, equipped with Nieuport fighters, decided to escort Gen. Balbo's flying-boat formation across France, but they could not keep up. France quickly re-equipped. Now in 1976, a new aircraft has departed from London for Singapore and Belgium has bought itself a fighter which will be incapable of keeping up with it." (M. Dassault)

International Law - Part IX by E. McCluskey

The International Court of Justice During the course of these articles we have frequently referred to decisions of the Courts at International level. Although the tendency has been for ease of understanding, to talk of the World Court there are several methods of International Judicial settlement which are of interest. In the case on the Status of Eastern Carelia it was affirmed "No State can, without its consent, be compelled to submit its disputes with another or other States either to mediation or arbitration, or to any other kind of pacific settlement. Such consent can be given once for all in the form of an obligation freely undertaken, but it can on the contrary also be given in a special case apart from any existing obligation." Let us look then at the kind of mediation or arbitration which has existed and which still exists. The first method used in International Law was the appointment of a person who might have been a Head of State, e. g. King George V of the United Kingdom, acceptable to both States with full or limited powers to mediate in a dispute. Prior to 1914 this system was very successfully used but it became increasingly complicated to mediate without a vast knowledge of International Law and the ad hoe tribunal arrived on the scene of International Law. This type of tribunal is entirely dependent on the provisions of a Treaty which gives it its jurisdiction. The Treaty may declare that in case of dispute the States will present their case to arbitration either by an individual, a commission, or a mixed commission with a person chosen from each side plus an independent umpire. Except on very rare occasions, it is usually the umpire who makes the decision which becomes rather like a majority vote. Principles, as well as how the umpire is chosen, may ba set out in the Treaty but, if not, the Hague Convention of 1907 lays down a code of procedure. Normally such a decision is binding on the parties unless a system of appeal is provided for in the Treaty or there is a proven case of fraud. Something more permanent was needed and the 1907 Hague Convention set up a Permanent Court of Arbitration. The Signatories to the Convention set up a panel of jurists appointed by themselves and the Court could delegate hearings to a tribunal on which sat selected members of the Court. It is clear from the fact that the Court still exists but that the last case was heard in 1932 that the States no longer seem to have a liking for this method. Three permanent bodies have come into being, the first of those being the International Court of Justice. Although this is the subject of the article, we will nevertheless mention the other two as they could be more likely to affect at least some of IFATCA's members. As the International Court of Justice can hear cases only between International Persons, the only possibility of a controller ever being involved might be as a witness. The case taken to the International court must have exhausted all the normal channels in municipal courts with an unsatisfactory result whereupon one State brings a case with the agreement of another. In aviation, this would have to concern a breach of Treaty responsibilities. Again it could be the case that our

Federation might be involved in a law suit with a Government. All the normal processes of Law having been unsatisfactorily concluded, a case could go to the International Court of Justice but one of the parties on the side of IFATCA would then have to be Switzerland, the State in which the Federation exists as a corporation. Again a member of the Federation might be a witness but these are extreme cases. The main interest we have therefore in the International Court of Justice is how its decisions add to, change or declare the Law because - as we have seen in each of the preceding articles - the air traffic controller is affected by principles of International Law and remember that we have not yet touched in detail International Aviation Law. The International Court of Justice was set up in 1946 to replace th~ Permanent Court of International Justice, a League of Nations organ, by an organ of the United Nations Organisation. The seat of the Court is in The Hague. The Court consists of fifteen judges. They are elected from among the Members of the Permanent Court of Arbitration by a majority of both the UN General Assembly and the Security Council. They are elected for nine years and five retire every three years. Only one judge from any one nationality is permitted. Normally the cases heard are between States but the UNO can ask for advisory opinion. If request~d other International Organisations with International Personality may make submissions and these must be heard. The consent of the General Assembly and the Security Council of the UNO is required for non-UNO members to bring a case. States must consent to go before the International court of Justice unless all parties have accepted the "optional clause" of Article 36 of the Statute of the court. The "Optional Clause" has been accepted by about half of the World's States but many have added severe reservations to their acceptances. So in order to have compulsory jurisdiction the Court must first examine whether the reservations mutually correspond. This as the reader may well imagine limits the Court's actions considerably and it is exactly this point which has been underlined throughout these articles. There is no World Police Force and the World court has limited jurisdiction. The main trouble is that the reservations put forward by the States are wide open to many differen~ interpretations. This may or may not be deliberate. As this happens in the case of many States we cite the case of the United Kingdom to illustrate the point. The reservation states: "disputes arising after the ratification of the present declaration with regard to situations or facts subsequent to the said decl _ ration". Of course many international disputes contin:e over long periods and the. real cause of a dispute could well have occurred a long time before the ratificafi M t . I . on. OS States, as 1s correct nt~rnat1onal Law, reserve to themselves cases of a purely internal nature some 1 • h .d th t .t . . • eavmg t e a 1 1s internal. The USA h Court to d ec1 e · th " r ,, as a reservation o.n e op 1ona.1 c 1aus~ disputes with regard to matters wh1c~ are essentially within the domestic jurisdiction of the United States as determined by the u ·t d s " Th · · th · nt e tates. ere 1s m 1s case no doubt on interpretation but the Court is again limited in its jurisdiction. The United King23

Ferranti simulators put years on your student controllers

' I

Our A TC training simulators give controllers the experience they need to do their job - before they start doing it. This is due to the detailed and comprehensive realism of Ferranti digital simulator systems. The trainee controller's radar displays are identical with those used operationally, and simulated RT and intercom are provided. With this equipment th~ trai!1ee learns h.ow to cope . with aircraft identification, separation, sequencmg, the allocation of levels, routing, stacking, and other problems. . . . Ferranti have studied air traffic control m depth and have an understanding of current and future needs as realistic as the sim!-1l~tors themselves. We know the economic importance of

handling heavy air traffic with minimum delays. It's hardly surprising therefore'that Ferranti ATC simulators have been chosen for the largest and smallest requirements and are currently in service or on order for London Heathrow, Amsterdam Schiphol, Rome Ciampino, Copenhagen Kastrup, Taiwan Taipei, Sydney Australia, and at the College of Air Traffic Control at Hurn. And a Ferranti simulator is used at the CAA ATC Evaluation Unit for their real time traffic control studies. Ferranti Limited, Digital Systems Division, Western Road, Bracknell, Berkshire, RG12 IRA. Telephone: 0344 3232. Telex: 848117.

FERRANTI

The real thing in simulation

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...

'.... ·.:,/·; . . .. .. . I ··~1 ··

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dom uses another reservation which was a subsequent addition, "national security". The Court has been silent on the legality of such reservations. However judges and writers throughout the World have roundly condemned the practice. In the face of this criticism such States as France and India have abandoned such reservations. The United Kingdom has abandoned for any events occurring after 26th November 1958. Faced with this sort of situation the Court must still act justly and so in 1957 when France still had reservations "in her opinion essentially within her domestic jurisdiction" and Norway had no such reservations, in the Norwegian Loans Case, the Court ruled that Norway could use the French reservation on the grounds of reciprocity. Under Article 38 of the Statute, the Court must apply in order of precedence, international Conventions, international customary law and the general principles of law recognised by civilised nations. There is no rule of precedent but previous cases can have a great influence as can the writings of recognised international lawyers. The cases are heard in public after written pleadings have been made and the States are represented by "agents". Judgement is by majority with a minimum quorum of nine judges. Dissenting opinions may be expressed. Once the parties have agreed to the proceedings, the judgement binds the States concerned, except that a State may return to the Court within ten years for reinterpretation or revision if some unknown decisive fact comes to light. It should be noted that at the time of writing attempts are being made to reach agreement between the United Kingdom and Iceland on the renewed "Cod War". The decision of the International Court was given only in 1973. This brief resume shows clearly that there is still a long w_ay to go in the establishment of a really satisfactory judicial system which is accepted world-wide. However more concrete powers seem to be developing in Europe with the Court of Justice of the European Communities and the European Court of Human Rights. The Court of Justice of the European Communities is the only legal ÂˇSafeguard against the ever increasing powers of the political control of the European Coal and Steel Community, the European Economic Community and Euratom. It is necessary as the "Common Market" countries lose some of their freedom of action. It may hear appeals from the member States against a High Authority or a Com~ission. It cannot question the judgement of such Authority or Commission on economic matters. The Court applies a common denominator of the municipal law of the members as Well as its own community law. Our main interest must as yet be in the future as the EEC Ministry of Transport has embarked on a policy of broad based developments Which already are touching on aviation in the EEC and associated States. Ten of IFATCA's Member Associations could in the future face a new form of law in aviation which is somewhere between International Law and Municipal Law. The Convention for the Protection of Human Rights and Fundamental Freedoms 1950 set up a European Commission and a European Court of Human Rights. The Court consists of a number of judges equal to the number of members of the Council of Europe. Cases are heard before seven judges of which one must be a national of a State involved in the proceedings. The first election of judges took place in 1959 and a number of cases have since been heard. From our point of view the importance of this Court 26

is the possibility for an individual to appeal when even in his own State he appears not to have received justice after the normal process of law. Individuals are therefore protected in the right to life, prohibition of torture or inhuman punishment; prohibition of slavery or forced labour; right of liberty and security of the person, to fair and public hearing, among other safeguards, in civil and criminal trials. There are other protections on discrimination and on family life but we are more interested in this series of articles in the case of an air traffic controller having the correct safeguards in a civil or criminal trial. Some States made reservations on the rights of civil servants to bring a case against their employer i. e. the Government, especially on breach of contract and in some cases no rights existed at all in the State. Now, happily, in most cases civil servants have the same right of appeal as other citizens. The Convention came into force when ratified by Denmark, Federal Republic of Germany, Greece, Iceland, Ireland, Luxembourg, Norway, Saar, Sweden and the United Kingdom. Both Denmark and ireland have accepted decisions of the Courts against them. The Re Lawless case was important as it concerned imprisonment without trial. Other signatories are Belgium, France, Italy, the Netherlands and Turkey. At the time, the United Kingdom signed on behalf of dependent territories and the Convention still applies to the following IFATCA Member Associations: Channel Islands, Cyprus, Malta, Rhodesia, while Denmark's accession includes Greenland. The Eurocontrol Guild is covered by the fact that all seven Member States are signatories to the Convention. Thus in Europe, there is a final court of appeal for an air traffic controller who has a prima facie case of not receiving adequate judicial protection in his home State. IFATCA believes however that more realistic and less time consuming justice can be available to the controller, and not only to European controllers, by the signing of an International Convention on the Limitation of Legal Liability of the Air Traffic Controller which, when ratified, would give him adequate protection in his home State. This course of action, subject to a decision of the 1976 Lyon Conference, will now become our Federation's most important topic for discussion with the International Civil Aviation Organisation which will be the subject of the next article in the series. For ~u~her study: - Law of Nations, Brierly O.U.P., Part VIII. Oppenheim s International Law, Lauterpracht Longmans, Part 11 Chap XIV. l~pact of the Universal Declaration of Human Rights. UNO. Oster~e1ch~sche Zeltung tor ()ffentliches Recht 1 (1952), pages 166-191. University of Western Australia Annual Law Review 2 (1952), pages 65-79.

The first Court decision on a wake turbulence accident ~n which both planes were flying ILS approaches under instrument conditions has been handed down in favour of FAA. The U.S. District Court judge for Maryland ruled that the controller at Baltimore Washington International Airport provided proper separation between the two aircraft a.nd -Âˇthat .the pilot of the Piper Commanche which crashed was improperly conducting his approach by flying w~ll below the glide slope. Expert testimony during the trial . showed that wingtip vortices from the 727 jetliner landing ahead of the Piper would have descended 240 feet below the glide slope by the time the Piper encountered them. (ATCA Newsletter)

Air Traffic Control in Sweden (Part I) by Hakan Westermark

Automation And Integration Mainstreams of Swedish ATC* Sweden has taken the first important moves in a giant leap toward large scale automation of its Air Traffic Services. Although some operational centres are already using computer processed data, notably the military Ostgota Control Centre near Norrkoping, and earlier the Malmo and Stockholm ACC's, the opening of an integrated ATS Training Centre at Malmo's Sturup Airport in September 1974 marked the beginning of a new era. This new school trains both military and civil controllers in readiness for the advanced computerised systems planned for the new Air Traffic Control Automated System (ATCAS), now in the planning and production stage and designed to meet all future requirements, and which will cover the entire Swedish airspace. By training the personnel who will use the equipment in the future, the training centre at Sturup acts as a springboard for a big move forward. The new school, which wilt be described in more detail in a following article, has replaced civil and military ATS schools previously located near Stockholm. In practice, the integration of civil and military ATC has been proceeding at an increasing pace in recent years, but it will become final reality in 1976 when the present military controllers, now employed by the Air Force, become part of the Luftfartsverket - the Swedish Board of Civil Aviation (BCA). It would be an exaggeration to say that Sweden is one of the big countries in aviation - if traffic density is considered as the criterion. On the other hand, Sweden certainly has a reputation for high standards in technology, air safety, and also Air Traffic Control. Having been in the same situation as most countries, with the BCA desperately trying to catch up with a permanent shortage of personnel, inadequate equipment and always lagging far behind the growing amount of traffic, the current development of Swedish ATC is not only intended to overcome these problems, but also to reverse the underdog situation by the mid-1980's. This, despite the fact that the range of services offered will be greatly increased by, for instance, the implementation of active control in all airspace below a certain, gradually reduced flight level, thus permitting true point-to-point navigation.

Sweden's ATC Organisation Today, Sweden has four Area Control Centres, namely Stockholm, Malmo, Gothenburg and Sundsvall (some 350 kilometers north of Stockholm). The airway pattern is rela* The first of a series of three articles describing the modernisation process which is underway to update Sweden's ATC facilities. In our August issue, we shall describe the new ATC S~o~t at ~atmo Airport, while in our November edition, a full description will be given of the ATCAS I system. The August issue will also contain an article on the activities of Stansaab Elektronik AB, IFATCA's Swedish Corporation Member.

Legend -·-·-Flight Information Route Major Civil Aerodrome

Military Aerodro·me

COPEN HAGEN I

Kaatrup

tively simple with the bulk of traffic flying between Copenhagen ~nd Stockholm. This route was extended up to parallel airway status in 1974 to permit one-way traffic flow About half of the traffic in these airways depart or land . · Co~enhagen, thus forming a climb/descent and co-or~~ nation problem for Malmo. For Stockholm, only a small percent~ge are overflights, and these are mainly to and fro Helsinki As . m of Fli h~ a co~plement to the airway system a number g Information Routes have been established wh'ich connect min or airports · • and those military airfields open to . sch ed u Ied civil t ff' AFIS r~ 1c. ~ost of the minor airports provide t bl'o~ly. Special Flight Information units have been e~ _a is ed. in Stockholm and Malmo ACC's for the superv1s1on and inform r . t a ion services for traffic along these rou~ es and for other uncontrolled IFR and VFR. 27

The integrated ATS Training Centre at Malmo's Sturup Airport, which was opened in September 1974, and where both military and civil controllers receive training.

Sweden has a long tradition of close co-operation between civil and military ATC. Since the end of the 50's, special units that include both civil and military controllers, operate in two air defence centres for the control of military aircraft crossing airways and flight information routes. For the control of military aircraft in some busy TMA's, special units have been virtually, if not formally, integrated into the civil terminal control organisation. Stockholm TMA, in close proximity to three military air bases - four up until a few years ago - is actually a joint civil and military TMA. However, in practice, the mi litary controller responsible for the flight must obtain a clearance from the civil sectors concerned. In most cases, the clearance involves conflicting c ivil traffic, which is indicated on the PPI, and for which due radar separation shall be maintained. Civil and military separation standards are the same. These special ATC units will be formally integ rated into a new ACC/TCC organisation during the course of this year.

Table 1 Traffic Volume May, 1975 max 24 hour average 24 hour FIR 676 500 FIR 468 389 FIR 211 168 FIR 173 117 The figures represent the number of flights controlled by ACC .

ESSA ESMM ESGB ESNN

As can be seen from Table 1, Stockholm and Malmi:i ACC's have the major portions of the traffic. Despite the fact that Sundsvall FIR covers nearly half of Sweden, radar is not yet used. The reason for this is, of course, that the t raffic density has not yet made radar necessary. It will , however, be introduced when a new centre comes into full operation this year. Gothenburg has a small FIR and also a small portion of the traffic. A new centre was opened in the spring of 1975, when SSR was introduced as a complement to the primary radar which has been in use for some considerable time. Th e equipment in Gothenburg and Sundsvall will be identical and at a rather simpl e stage of automation with features such as raw and synthetic presentation, code-calls ign correlation and labels, but with no tracking or flight plan handling facilities. Stansaab Elektronik AB, Sweden's I FATCA Corporation Member, have developed and produced the systems. 28

Stockholm ACC at Arlanda Airport is now 11 years old. When opened in 1965, the centre was thought to be very advanced in technology and environment. Time passes very quickly in ATC, and it has been obvious for many years that the process of partial extensions which started after only a few years, must be replaced by a new integrated system. When Malmi:i ACC was modernised in 1972, it was clear from the beginning that this could only be a short-term solution and that a new permanent centre would be required in the near future and that this should be located at the new airport of Sturup.

Government Investigation and Recommendations In 1966, a Public Commission was formed by the Government to investigate the organisation and provision of Swedish Air Traffic Services and to make proposals for the rationalised use of personnel and equipment. The first part of the Commission's Report - entitled "Training of ATS Personnel" - was published in 1969. The proposals were eventually accepted by Parliament in 1973, and provided a basis for the new ATS Training Centre at Sturup, .subsequently opened in 1974. A significant recommendation which was welcomed by all active controllers, was the move toward more time spent at school and less at on-the-job training. This principle led to the requirements for advanced equipment for the simulation of traffic situations at any centre or tower with its individual characteristics for geography, sectorisalion, regulations, etc. From a distribution of half school and half on-the-job training, the percentage is now approximately 60 Ofo at school and 25 Ofo on-the-job. The remaining 15 Ofo is flight training, now compulsory for all students, which is carried out at the Air Force training base at Ljungbyhed. The total training time up to complete rating is 26 months, including holidays etc. Training is common for all students, with the exception of the final six months when the student specialises in the type of duty for which he - or she - is going to be rated. The second part of the Commission's Report - "ATS 1980, System and Organisation" - was published in 1971 . This time, stress was laid on the phased reduction of the number of ACC's from four to two, achieved by the integration of Gothenburg and Stockholm ACC's into a " Greater" ACC planned for Sturup. Later, Sundsvall ACC will be replaced by a new "Greater" ACC in Lulea, in the very

Controllers at work at Gothenburg Air Traffic Control Centre, which was opened in the Spring of 1975.

north of Sweden. Another important proposal ~as for the complete integration of c ivi l and military air traffic, both in function and organisation. Armed with the proposals made by the Commission which had been accepted by Parliament, BCA began a detailed study of the future based upon the expected annual growth of traffic. The study resulted in a proposal for a series of Air Traffic Control Automated System (ATCAS} projects and the new Gothenburg and Sundsvall centres mentioned earlier. The ATCA's program can be considered in five clearly defined principal phases, as listed below. System ATCAS 1 ATCAS 2

ATCAS 3 ATCAS 4 ATCAS 5

Location Stockholm (Arlanda) ACC/TCC Malmi:i ACC/TCC (Gothenburg ACC inc.) Gothenburg TCC ACC "SOUTH " , Malmi:i ACC " NORTH", Lulea

Operational 1977 1979

1980 ca.1987 ea. 1990

This indicated time scale represents a delay for the later projects of approximately seven years, compared with that originally envisaged by the Commission. This is partly due to the recent knowledge of future traffic growth which is less than that foreseen in the late 1960's.

Modernisation Process in Full Swing The ATCAS I is now in production after a long and involved spec ification, tendering and evaluation phase. Stansaab Elektronik AB was awarded the main contract for the ACC/ TCC by the Telecommunications Administration on behalf of the BCA. The contract value totals approximately 30 million Swedish Crowns (about $ 6 million}. This will utilise the Stansaab Censor 900 Data System and will replace the present equipment supplied in 1964. Specifications for ATCAS 2 and 3 are also ready. Features of these systems are very much the same as those of ATCAS 1. In real terms, the cost for ATCAS 2 is estimated to be slightly higher than for ATCAS 1, and ATCAS 3 is expected to cost about half. A number of civil and military aerodromes and air defence centres will be directly linked to the systems for the exchange of flight plan and meteorologi cal data. All three systems will have fac ilities fo r corn-

puter to computer exchange of different kinds of flight plan messages. This type of data exchange is also planned between ATCAS 2 and Copenhagen. From now until 1982 nine new medium and long range radars will be installed in the sout hern half of Sweden . A ll radars will have duplicated SSA and plot extractor facilities. Digitised radar data w ill be transmitted ove r narrow band data links to the centres.

Prnent stage

ACC Sundsvall

Stage 2

Stage 3

ACC Stage 4

" NORTH"

How Sweden has planned the phased reducti on of the present four Area Control Centres to two in four stages. Eventually, only two ACC's will remain, namely ACC " South" (at Sturup , Malmo) and ACC " North" (at Lu lea, in the very north of Sweden).

With the ATCAS proj ects and the ATS T raining Cent re as the nucleus, t he present extension of the Swedish AT S means not only a great effort by the author ities to improve the standards of ATS in Sweden, but also the recognition of the importan ce of ATC and the necessity for f irst class equipment for effi cient and safe control. In giving active c ontrollers an important role during the evaluation and design of the systems, it has been recognised that operational and not technical req uirements must provide the basis for the design of any ATC system.

Did you hear about the wife who was most convincingly denying a divorce court allegat ion that she had com m itted misconduct with , o r even that she knew, an air traffic controller, until she replied to a direct question relating to the alleged miscondu ct by using the term "NEGATIVE". (IFALPA News Bulletin)

The Controller's Responsibilities As Viewed By The High Court Of Australia by R. J. Garlick, Industrial Officer, Civil Air Operations Officers' Association of Australia.

Editor's Note: Our Australian Member Association has sent a claim to the Chairman of their Public Service Board seeking a 75 O/o pay increase for ATC trainees, air traffic controllers and some other categories of personnel. The claim is based upon changes in work value, in particular upon increased legal responsibilities arising out of a Judgement in the High Court of Australia. Mr. Garlick's Paper on that case follows below. â&#x20AC;˘ IFATCA Member Associations are advised to take note of the principles involved in this Court case, which could well be applicable to controllers in other parts of the world.

The Facts of the Case On 29 August 1975, Mr. Justice Mason in the High Court of Australia handed down his judgement in the case of Australian National Airlines (T.A.A.) v. the Commonwealth of Australia and Canadian Pacific Airlines Ltd. The Court found that there was negligence on the part of all three Parties to the action which contributed to the occurrence of the collision and to the damage which was sustained. The greatest proportion of the responsibility for the damage was attributed to the Commonwealth (in respect of negligence by Air Traffic Control). I shall discuss the facts as the Court found them. At 2136 hours, approximately, on 29 January 1971 at Sydney Airport, T.A.A.'s Boeing 727 VHTJA, taking off in a southerly direction along runway 16 in accordance with a clearance for take-off given by A.T.C. struck a Canadian Pacific DCB, CFOPQ. The latter aircraft was stationary on the runway at the time of impact, having come to a halt after proceeding to backtrack in a northerly direction along the runway on the completion of its landing roll. Although no one was injured in the collision, each aircraft was extensively damaged. T JA had reported ready at the holding point of runway 16 and received from A.T.C. the instruction "TJA, DCB on short final, line up behind that aircraft." The crew of TJA saw CPQ pass in front of them as it came in to land. T JA then moved out on to the runway with its engines idling. At 2134:53 when CPQ was in its landing roll, Aerodrome Control called CPQ "E301, take taxiway right, call on 121.7" Âˇ (121.7 was the Surface Movement Control frequency). Although the message was acknowledged by the First Officer of CPQ, the words "take taxiway right" were understood by him as "backtrack if you like". CPQ made a 180 degrees turn on the runway and began to taxi to the north. Its 180 degrees turn was not observed by the Tower which assumed that it had left the runway by taxiway India. At 2135:3B Aerodrome Control instructed TJA "TJA, radar departure turn right heading one seven zero cleared for immediate take-off." This instruction was acknowledged at 2135:44 by the Captain who turned on his headlights, applied the power and sent TJA into its take-off roll. Neither he nor any other member of the crew observed CPQ on

the runway at that time. The Captain and the First Officer assert that they did not observe CPQ during the course of the take-off roll until rotation. Shortly after the aircraft became airborne it struck the tail fin of CPQ at 2136:34. As the hydraulic syster:n of the aircraft was put out of action it returned to the airport and landed, after jettisoning Its fuel at sea. Meanwhile, as CPQ had turned through 110 degrees of its turn, CPQ's Captain became aware that an aircraft was facing him at the northern end of the runway with its headlights on. However, he thought that it was being held at the threshold until the runway was clear. As CPQ taxied north, the crew realised that the aircraft (TJA) was approaching them. The Captain then veered to the eastern side of the runway facing thirty degrees to the right of the direction of the runway so as to minimise the risk of a collsion. CPQ was stationary at the time of impact. The Tower was unaware that a collision had taken place until TJA reported subsequently. In the meantime CPQ was advised (at 2136:45) to "continue straight ahead along that taxiway cross runway zero seven", to which CPQ replied at 2136:50 "Roger, you got a guy on final right now?" This was a reference to another aircraft, a DC9, which was coming in to land on runway 16. At 2136:54 the Tower said to CPQ "E301 confirm you are on the taxiway" and CPQ responded at 2136:57 "Negative Sir, we're on the runway, we were cleared to backtrack on the runway." CPQ was then instructed to take the next taxiway left, but at 2137:05 the Tower had to instruct the incoming DC9 to "go round".

The Judge's Comments The Judge questioned the reliability of the oral evidence given by the crew members of TJA, and said: "I regard the account which they have given of the events leading up to the collision as unsatisfactory and unreliable." He also said of the crew of CPQ "they did not impress me as accurate witnesses." The Judge found that the Captain of TJA saw CPQ on the runway shortly after he commenced his take-off roll - ,.it sufficiently appears that the Captain became aware at a time when TJA was at a speed of no more than thirty-five knots some nine seconds after TJA had acknowledged the clearance for immediate take-off that CPQ was ahead and apparently still on the runway." The Judge then turned to A.T.C., commencing: "Although the Officers in the Tower thought that CPQ, which executed its 180 degrees turn in the vicinity of taxiway India, had turned into that taxiway and had left the runway, it is acknowledged that they were mistaken in this view. The A.T.C. Officers whose function it was to give directions to CPQ and TJA on the night in question were inexperienced . . . In fairness to them it should be said that there were several factors which operated or may have operated to impair their vision of an aircraft on runway 16 in the vicinity of taxiway India." (The Judge then mentioned as such factors a hump in the runway, rain, a tendency for the Tower windows to become misty).

The Judge said: "In my view, the Controllers saw CPO commence its turn and assumed that it was the beginning of a turn into taxiway India and that such a turn would be executed in accordance with the instruction given without ver!fying the fact by visual observation or radio c~mmuni cation · · · A.T.C. was negligent, not only in failing to keep CPQ under proper visual observation so as to ensure it was clea~ of the r~nway before clearing T JA, but in failing to establish CPQ s position by radio communication in particular on its failure to call SMC (Surface Move~ent ;~ntrol) thirty seconds aft~r t~e instruction at 2134:53 ... e errors made by A.T.C. indicate deficiencies in the procedures which it then followed." . The Judge then referred to the Department's Aeronautical ~nformation Publications and Airways Operating Instructions. He quoted the "relevant provisions of A01 ", as follows (from RAC-0-5): "2 - In providing ATC service in accordance with this section of A01, the prime responsibility of air traffic controllers is the ever important safety function of preventing collisions and advising known weather hazards. Traffic expedition, although important, must always take second place." "5 - Whenever there is the slightest doubt or even a suspicion of doubt as to the actual traffic situation, which could mean there may be a conflict between aircraft, then air traffic controllers are to assume that such a condition does in fact exist, and they are to act in a manner which will remove the possible conflict ... " Paragraph 7.1.1 (under the headings "Functions of ATC" and "Aerodrome Control") states: "Aerodrome Control is the exercise of the functions of ATC arising from ANR 144 (b) or ANO Part 95.2 as appropriate. This service is provided (a), to authorise aerodrome traffic to taxi, take off or land, and (b) to ensure the safe, orderly and expeditious flow of this aerodrome traffic." He then quoted from AIP: "4.5.1 - An aircraft will not be permitted to commence its take-off: (b) until a preceding landing aircraft using the same runway or path has vacated it and is taxying away from the runway or path." The Judge continued: "It was therefore the duty of A.T.C. and of Aerodrome Control in particular not to clear T JA for take-off until CPQ had vacated runway 16 and was taxying away from it ... A.T.C. and the first defendant (the Commonwealth) were negligent in that take-off clearance was given to T JA when CPQ was still on the runway because adequate visual and radio observation on CPQ with a view to establishing its whereabouts was not maintained." The Judge then considered the actions of the crew of CPQ. He reiterated his view that their oral evidence was unreliable. He found that CPQ in particular through its First Officer and the Captain had paid insufficient attention to the Tower communication at 2134:53 and thereby had failed to understand and comply with it. He noted that the Captain had not flown into Sydney since 1962; the First Officer had been to Sydney only once or twice previously; another Pilot (a Captain) had last flown into Sydney in 1967; and the Second Officer not at all. "In this respect, the second defendant (CPQ) was in breach of reg. 215 (1) (b) of the Air Navigation Regulations which required that the Officer in command should have flown into the airport not more than twelve months before."

The Judge found the First Officer of CPQ was negligent in failing to seek confirmation of the A.T.C. instruction of 2134:53 (there being elements in the message understood which should have excited inquiry - e. g. it appeared to suggest that A.T.C. was giving taxying instructions on an active runway; as understood by CPQ, it required CPQ to change to Surface Movement Control frequency whilst the aircraft was backtracking on an active runway" - a procedure fraught with potential danger and contrary to good practice.") "Moreover, the Captain should have perceived T JA at the northern end of the runway with its landing lights on when CPQ had turned through 110 degrees, that is at about 2135:42. He should then have appreciated that a situation of potential danger existed, for the presence of an aircraft at the end of the runway with its landing lights on indicated that it was taking off or about to take off. At this stage CPQ should have reported its position to the Tower. Had it done so, the collision would probably have been averted as TJA was cieared for take-off at 2135:38." The Judge then referred to certain requirements in the Aeronautical Information Publications and the Air Navigation Regulations 'AIP RAC/OPS-0-12 par. 9.4 under the heading "Traffic Clearances" provides: "An air traffic clearance proposed by ATC does not relieve the pilot in command from complying with statutory requirements nor from his responsibility for the ultimate safety of his aircraft." The relevant provisions in the Air Navigation Regulations are as follows: "138(7) - An aircraft that is about to take off shall not attempt to do so until there is no apparent risk of collision with other aircraft." "139(1) - An aircraft shall not be operated on the ground in such manner as to create a hazard to itself or to other aircraft ... " "143 - The pilot in command of an aircraft which is being operated on or in the vicinity of an aerodrome shall a) observe other aerodrome traffic for the purpose of avoiding collision." "238 - Immediately prior to take off, the pilot in command shall manoeuvre his aircraft so that he is able to observe traffic on the manoeuvring area of the aerodrome and incoming and outgoing traffic, in order that he may avoid collision with other aircraft during the takeoff." These provisions make it clear that the ultimate responsibility for the safety of his aircraft lies with the pilot in command and that he has a duty before and during takeoff to observe other aircraft so as to avoid a collision.' The Judge continued: "In addition, according to the evidence of experienced pilots called by the plaintiff (T.A.A.), it was the duty of the crew of T JA as a matter of good airmanship to keep a proper lookout down the runway from the time when T JA was lined up for take-off through to rotation ... The Captain and the First Officer of T JA failed to keep a proper look-out before the commencement of the take-off roll and immediately after that commencement. The Captain was therefore in breach of the direction contained in AIP RAC/OPS-0-12 par. 9.4 and of rags 139 (1), 143 (a) and 238. What is of more importance is that the Captain became aware nine seconds after receiving the take-off clearance that CPQ appeared to be ahead of him and still on the runway ... T JA had ample opportu-

nity to brake and bring itself to a halt in time to avoid the collision. It is a fundamental rule of good airmanship that the pilot of an aircraft taking off should stop his take-off roll if he sees an aircraft or obstruction on the runway ahead of him or if he sees what appears to be an aircraft or obstruction on the runway ahead of him. The Captain took a calculated risk that CPQ would leave the runway in time or, more probably, that he would be able to overfly it. In fact had CPQ not been moving north along the runway it is possible that TJA would have overflown CPQ without striking it. However, the risk was considerable and it s~ould not have been taken."

The Verdict His Honour then stated: "On any view it seems to me that the culpability of the first defendant (the Commonwealth) was greater than that of the other parties. Safety in prevention of collisions is the primary responsibility of A.T.C. and the duty of Aerodrpme Control to keep a proper lookout and to ensure that a landing aircraft is clear of the runway before he gives a clearance for take-off is of fundamental importance to the safety of operations at an airport. The failure of ATC to keep a proper look-out and the issue of a clearance for immediate take-off without maintaining adequate visual and radio observation of CPQ was,

in the circumstances, a serious departure from the standards of the reasonable man." His Honour then effectively apportioned responsibility as 40 % for the Commonwealth and 30 O/o for each of the airlines.

Controllers' Responsibilities Now Dramatically Increased This High Court decision marks a dramatic increase in the responsibilities of air traffic controllers. His Honour in effect found that the pilots of both aircraft had information reasonably available to cause a judgment to adopt a different course of action, but then found A.T.C. more responsible for the accident than each of the crews. His Honour states that the ultimate responsibility for the safety of an aircraft lies with the pilot in command, but afterwards states that safety in prevention of collisions is the primary responsibility of A.T.C., placing greater culpability on A.T.C. than either of the crews, even though the crews' actions did not appear to "be motivated by judgements based on information reasonably available." The High Court decision has thus dramatically increased the legal responsibilities of air traffic controllers working in Australia, after comparing the officially held local viewpoint that pilots and controllers must carry their responsibilities in concert, with the decision now given by the High Court of Australia.

Air Route Surveillance Radar System ARSR-3 Introduction The U.S. Federal Aviation Administration has awarded Westinghouse Electric Corporation a $ 30 million contract for 14 fixed site ARSR-3 radars and 2 Mobile Enroute Radar Facility (MERF's). The FAA also has an option to order 8 additional fixed site systems and 2 additional mobile systems. The first of theÂˇ new ARSR-3 L-band radars will be delivered in mid-1977, with the rest following during 1978 at a rate of two sets per month. The first unit to be delivered. will be installed at the FAA Aeronautical Center at Oklahoma City for training purposes, and the next three will go to New York City, Chicago and Washington D.C. Two of the 16 units on order are mobile models which will be used to quickly replace any other radar temporarily unserviceable, for example by severe weather or by an accident. The ARSR-3 will be the prime sensor for the Automated NAS Stage A System for enroute Air Traffic Control. The ARSR-3 is designed to detect even very small aircraft, and to greatly reduce or eliminate radar returns from objects other than aircraft. These returns, usually called false alarms, can be created by weather, ground objects, and electronic interference. False alarms can overload the data processor and prevent transmission and display of desired aircraft returns.

What the System has to Offer To reliably detect aircraft in adverse conditions, the ARSR-3 features: Dual channel, diplex operation; - Dual-beam receivers;

Sharp cut-off on the underside of the elevation pattern; Coherent, ultra stable, high-power klystron transmitter; Range-azimuth-gating (RAG) system; Constant false alarm rate (CFAR) receivers; Digital I and Q moving target indicator (MTI); Weather receivers. A number of elements contribute to the availability of the radar: Du~drive pedestal; Solid-state modular transmitter modulator; Solid-state frequency generator; Solid-state transistorized microwave receiver; Solid-state IF receiver; Digital circuitry. When a fault does occur, the ARSR-3 will automatically select the available operating channel. A broad array of built-in-test equipment (BITE) will permit the quick location and elimination of faults to enable the ARSR-3 to return to full diplex service. In addition to the equipment, the ARSR-3 includes facilities for maintaining the equipment and supporting the personnel who live with the radar on a permanent basis. The conception of the ARSR-3 is as follows: A modular tower is provided. The base section is approximately 7.6 meters tall. With additional 3.8 meter sections, it is incrementally extendable to a height of 22.8 meters. The radome is approximately 19.8 meters in diameter. In addition to the identical radar channels, the ARSR-3 contains a Common Equipment Module with storage and maintenance areas, an Administrative Module with personnel facilities, and an Engine Generator Module for emergency power, should the prime power source fail.

Since the overall system design is modular, many alternate configurations are possible. Some specific alternates are: Identical system in hard buildings; Two channel radar with combined Common Equipment and Administrative Module (4 total buildings); Single or Double Channel in hard building without tower (Antenna/ Radome mounted on building); MERF - Mobile Emergency Radar Facility houses in vans, both land and air transportable ; Combinations of the above. In addition to the above configurations, systems with either broadband or narrowband output hardware (rather than both) with integral single or diplex Digital Target Extractors (DTE); without displays or with other displ ay types are also easily provided.

System Description Antenna

The ARSR-3 antenna includes a number of sig nificant features which enhance the overall radar performance. A '.lual, upper and lower, elevation beam configuration is employed. The radar transmits on the lower beam but receives on both the lower and the upper beams. Since no transmission occurs on the upper beam, this configuration is sometimes referred to as the " passive" horn system. A more common name for it is the "scan-down-onreceive" system. An important feature of the ARSR-3 is the incorporation of the integrated beacon or SSR feed into the primary feedhorn assembly. The large radar reflector produces an azimuth and elevation pattern far superior to that of a separate small antenna. Provisions are made to all ow limited tilting of the SSR elevation pattern relative to the primary radar pattern. The outputs from the dual-beam receivers are range and azimuth gated. The gating is optimized for each particular site. At close range, the upper beam is the source of target information, and for long range detection, target echoes are derived from the lower beam. The dual-beam configuration improves close-in aircraft detection, since the upper beam receives less ground clutter than the lower beam. Considering a conventional radar receiver, the dualbeam arrangement is equivalent to tilting a single beam pattern up at short ranges and then tilting it down at longer ranges to optimize coverage. The combination of the beams provides the target detection capability shown in

3• 24 O iplu Mod•

T•ro•t

2m' 0 0

40 Approxinuno Slan t Range

Figure 1 ARSR-3 Target Detection Capability

Figure 2 The Antenna System of the ARSR-3. Providing a detection range to over 430 kilometers, the dual-beam radar employs this 13 metre wide by 6,9 metre high reflector with a scan rate of 5 revolutions per minute.

figure 1. The antenna system is shown in figure 2. The passive horn antenna system is also valuable in reducing false alarms due to radar returns of an unknown or not fully known nature, often called "angels". Usually, " angels" are found at low a ltitude and their echoes are much weaker in the upper or passive horn beam. To optimize dual-beam performance, a relatively high crossover between the upper and lower beams is selected and maintained within close tolerance over the operating frequency band of 1250 to 1350 MHz. Another desirable feature of the ARSR-3 antenna is the unique underside of the elevation beam or pattern. The underside is very "sharp" with very low sidelobe levels in this region. In operation, this feature reduces the " vertical lobing" of the antenna pattern at the low elevation angles which, in turn, enhances the long-range, low angle coverage. The sharp underside of the elevation pattern also improves the circular polarization weather rejection performance of the radar by reducing reflections. Reflections can prevent cancellation of rain echoes. Additional features of the ARSR-3 antenna system which distinguish it from other surveillance radars are improved circular polarization lower azimuth sidelobes at all elevation angles, low back~ radiation , and a minimum of beam broaden ing as a function of elevation angle. Either linear or circular polarization can be selected. Orthogonal circular polarization provides weather c lutter cancellation in the receiver which is attempting to detect aircraft and concentrates the weather echoes in the receiver which is generating weather co ntours. Lower azimuth sidel ~bes red_ u ce the possibility of receiving aircraft returns m the s1delobe which , in turn . reduces the possibility of generating false target information. A consistent azimuth beam-width as a function of elevation ang le results in improved angular resolution and acc uracy.

The ARSR-3 antenna is specifically designed for excellent vibration characteristics. This ensures that the MTI performance will not be affected by antenna vibrations. The antenna is a horn-fed, shaped reflector forming two cosecant squared beams with a high elevation "thumb". The beams provide coverage to a 42-degree elevation. The two beams are formed with two feedhorns placed above and below the focal axis. The antenna reflector is a seven-panel assembly which permits quick erection of the antenna, and repair of the reflector should it become necessary. The reflecting surface is an expanded mesh screen. The mesh dimensions have been carefully selected to avoid leakage through the mesh. and to eliminate polarization sensitivity. The reflector and dual-horn feed are mounted on the pedestal in such a way as to allow adjustment of the low beam vertical -3dB point ±3 degrees above and below the horizon.

siderably to the reliable operation of the transmitter. A transmitter improvement also, is the multi-module solidstate modulator. A limited number of modules can be removed from the modulator without impairing transmitter performance. The solid-state, redundant design significantly improves availability over other long-range radar. Reverse switching rectifiers (RSR) are employed as high current switches. If silicon controlled rectifiers (SCR) were substituted, over three times more switching devices are required, reducing reliability. In recognition of the need to rapidly return the ARSR-3 radar system to full operational status after a momentary loss of primary power, each radar channel is equipped with an uninterruptable power supply (UPS). The UPS provides power to the transmitter filaments. The UPS essentially consists of a battery bank, a battery charger, and controls.

The rotary joint is one of the few units in the radar chain which is not dual or redundant. It is designed very conservatively. Bearings have been selected to provide long life. The rotary joint is mounted so as to minimize pedestal loads from being transferred to the rotary joint. BITE is. also incorporated in the antenna. A test horn is mounted behind a hinged section of the center reflector panel. The test horn is mounted in a fixture which allows the horn to be rotated about its axis. The horn is used for microwave power measurements and to check the ellipticity of the primary feed.

Dlplex Operation

Pedestal . A key contributor to total system availability is the dualdrive pedestal. One drive can be replaced while the other continues antenna rotation. The splitting of input power ~etween two drives also reduces gear tooth loads and increases service life. The pedestal is arranged so that full ac.cess is available to the drives, rotary joint, slip rings, and azimuth change pulse generator from underneath the tower Platform. Routine maintenance and/or repairs can then be made without stopping antenna rotation or turning off the transmitter as '1t is required with existing radars. If the very ~onglife main azimuth bearing must be replaced, it can be e~o~ed with the aid of hand tools and a few pieces of built-in equipment. This feature is not found in other longrange radars.

Transmitter The ARSR-3 transmitter is a pulsed microwave amplifier gener r ' to a mg 5 megawatts peak output power. In addition en amplifying, the transmitter also filters the microwave AR~~~; reducing the possibility of interference between an~ other electronic equipment. The last stage in the t microransmitter chain is the klystron. As a high-power wave sour th . . other ty ce, e klystron transmitter 1s superior to Pes, such as magnetron transmitters. The klystr · (such as th on 15 an amplifier rather than an oscillator

than is po ~ mag.netron), and offers far greater stability transmiss· ssible with oscillator type transmitters. Since the ion frequency · · filters can b . is well defined optimum receiver noise and e eh implemented to effectively eliminate excess is increasedn_ ance target detectability. Clutter cancellation characteristi~~ t~e MTI, by the ~xcellent short-term stability visibility (SCV). f the transmitter enhancing subclutter

~ 1 9~~ icant characteristic of the ARSR-3 transmitter is

its rehabihty. The selection of a proven klystron adds con-

The ARSR-3 consists essentially of two radars, referred to as channels sharing an antenna. Each transmits at a different frequency and polarization. Target echoes are first processed by both receive channels and then are combined to yield a dramatic improvement in the ability to detect a target. Aircraft detectability is improved since if an aircraft echo fades in one channel, the aircraft is likely to be detected in the other. The marked reduction of these troublesome fades is a characteristic of diplex operation. For an 80 percent probability of detection, diplex operation results in over a 25 percent increase In detection range over single channel operation • When the ARSR-3 is transmitting circular polarized energy, echoes from rain are sorted into one channel receiver and are used to generate weather contours. The other channel receiver rejects rain echoes to a much greater degree than aircraft echoes, so it is utilized for the detection of aircraft. Since one of the channels transmits right-hand polarized energy, while the other transmits lefthand polarized energy, target, and weather information is available from both channel receivers. Diplex benefits are available in both linear and circular polarization operation. Receiver

The receiver group package includes the maintenance . display and the digital signal processor. The microwave (RF) receiver is completely sohd-s~~te. . . d without adjustments. Prece mg Noise figure is mamtame 'd t te digitally controller the low noise RF amplifier is a so.':. ::ya c~n be programmed RF gain control. Receiver seTnhsi ·~~humb" in the elevation II duce clutter. e to op ti ma Y re . duction of receive sensitivity antenna pattern permits re without degrading high-angle coverag~. . The ARSR-3 is equipped with 1ogar~t~m1c and MTI pro. b th featuring CFAR capability. The log-CFAR cessmg, o . . . h the advantage over the conventional receiver . . • receiver as in that it can reduce or ellmmate false a~arms due to weather clutter which is not cancelled by circular polarit . n (often termed punch-through). za10 . . The CFAR action is particularly valuable when operating into a radar digitizer, since false alarms could readily overload or saturate the system. weather echoes are processed by logarithmic and MTI receivers. These outputs are available for weather contouring the processor digitizer.

Digital Signal Processing In the ARSR-3, desired aircraft echoes are separated from clutter and other undesirable signals by digital processing. Digital equipment is inherently more accurate and reliable, offering predictable performance. â&#x20AC;˘ The digital range-azimuth-gating (RAG) generator can be programmed to provide precisely defined range-azimuth g~tes. These gates are utilized to control RF gain, select either the upper or the lower receive beam, and to select either logarithmic or MTI output videos. The digital MTI is a three-pulse canceller which processes all the echo energy (l&Q). This enhances aircraft detectability over ground clutter, as well as in a noise environment. Digital storage permits the ARSR-3 to employ either fixed or variable interpulse periods. Several variable interpulse programs are available, and designed to eliminate the serious MTI insensitivity to specific aircraft velocities (blind speeds). A smooth MTI velocity response is provided to. over 3500 kilometers per hour. Digital CFAR circuitry compensates for a variation in intensity of background interference {noise, weather, etc.). This circuitry is present in both MTI and non-MTI receivers. All alignment and destaggering operations are accomplished digitally. Similarly, a digital feedback integrator improves the quality of the PPI display without degrading either accuracy or resolution. The processing control functions for diptex combining and selection are also digital. The ARSR-3 incorporates the digitizer or plot extractor as an integral part of the radar. For a radar such as the ARSR-3 where the majority of the receiver processing is digital, integration of the plot extractor into the radar offers both improved performance and a tower ~ost. System Control and Monitoring Common controls for both channels and monitoring of both status and performance are accomplished in the Control Group. The maintenance display is equipped with both instant and a continuous filming capability for PPI data. The ARSR-3 utilizes a sophisticated control system, based on the concept that diplex and simplex operation is established by video selection and mixing, and not by controlling transmitters and receivers. The various outputs from the two channels are cross-connected to combiners/ selectors in each channel. Either channel can provide diplex outputs. The system control also incorporates a variety of automatic channel switching features.

Characteristics The following tabulation highlights the key differences between the ARSR-3 and other long-range, dual beam radars: Detection range is increased by transmitting 5-megawatt peak pulses; No missing pulses because magnetron is not used; Coverage is increased because upper/lower beam separation is less than 4 degrees; Weather cancellation is improved because both beams offer an ICR greater than 18 dB; Clutter rejection is improved by extremely sharp elevation pattern underside and low sidelobe levels; Upper angle coverage is improved by "thumb" at high elevation angles; Polarization diplexing permits both channels to operate on the same frequency, if desired. No minimum channetto-channel frequency separation required; Wide channel-to-channel frequency spacing unneces-

sary because the ARSR-3 is a coherent system. Clutter will cancel no matter which channel receives it; Separate RF receivers for low beam, high beam, and weather channels; Receiver protector operates even with system turned off. Requires no external power; Wide-band (1250-1350 MHz) RF receivers, with tuneable preselector filters; Digital STC generator programmable to decrease RF attenuation at selectable rates from RO to R6, as a function of range. RAG controlled RF attenuation can be added to combat point clutter. MTI and l&Q processing to 192 nautical miles (370 kilometers); Nine-bit AID converters sample video every 1/16 nautical mile to improve range resolution and reduce sampling losses; Smooth MTI velocity response to 2,000 knots. Critical first blind speed null depth, near 75 knots, less than 8 dB. Feedback not utilized in MTI. Feedback results in poor impulse response, requiring a long blanking interval. Also vulnerable to interference. Feedback also varies the width of the first blind speed null, reducing sensitivity.

Performance Characteristics Detection Range Coverage Target Cross-Section Blip-Scan Ratio False Alarm Rate MTI Improvement Factor Dual Beam Receiver Integrated Cancellation Ratio Azimuthal Resolution Distance Resolution Azimuthal Accuracy Distance Accuracy

435 kilometers minimum in diplex mode To 18,600 meters altitude 2M 2 (Swerling Class I) 0.8 10-6 39 dB 16 dB suppression of clutter (low beam on horizon) 18 dB minimum 2 degrees better than 0.5 kilometer 0.2 degree Better than 0.25 kilometer (0.5 percent of true range)

Electrical Characteristics Transmitted Frequency Pulsewidth Average PRF Antenna Gain Azimuth Beamwidth Azimuth Sidelobes (Principal Plane) Elevation Beam Underside Sidelobes Relative Gain of "Horizon" Transmitter Stability Stalo Stability Coho Stability Data Rate Noise Figure Low-Beam Receiver High Beam

1250 to 1350 MHz 2.0 microseconds 310 to 360 pulses per second Low Beam High Beam 34.5 33.5 1.2 deg 1.2 deg 26 dB maximum 24 dB maximum

24 dB maximum 23.5 dB maximum 19 2 dB 3 dB SCV limit 42 dB minimum SCV limit 50 dB minimum SCV limit 50 dB minimum 12 seconds (5 rpm) 4.0 dB maximum 3.5 dB maximum

Full Diplex Mode Availability Reliability System MTBF

750 hours

Maintainability System MTTR System MPMT

0.46 hours (mean) 2 hours maximum 0.44 hours in 168 hours

Availability Availability

0.996

Social Stress And The Air Traffic Controller by Robin Soar, New Zealand Air Traffic Control Association.

Introduction In March 1969, a Heron aircraft flew into a hillside, whilst being directed by a radar controller who was under training. There were many other contributing factors but for the purposes of this paper it was particularly significant that the controller had considerable domestic problems. Owing to the unavailability of accomodation, and to delays in the shipping of his furniture and personal effects from his previous location, he was camping in unfurnished rooms with his wife and four children, sleeping on mattresses on the floor, eating off a card table, and sitting on folding chairs. Obviously in his home environment he was under stress. This is noted in the accident investigation report (published in our August 1975 issue - Ed.), together with other psychological factors. How much the stress of the home environment contributed to the accident is not clear, nor, I submit, could it have been assessed then or now on the basis of existing knowledge. There have been studies of stress in the home, notably 'Social Stress' by S. H. Groog, and studies of stress on air traffic controllers, but there is no known authoritative literature on the relationship between stress in the home and the controller at work. We, as air traffic controllers, believe this to be a medically neglected problem with unbeknown safety implications. Air Traffic Control is by nature a high stress occupation. The controller is responsible for the 'safe, orderly and expeditious' flow of air traffic. To fulfil this responsibility, the controller must make rapid decisions, drawing on multiple information sources. There is rarely time to refer to written 'standards', and therefore he relies greatly on memory and experience. He is often unable to control his workload, and even when trame :is light he experiences tension from always having to remain alert and ready to handle traffic conflictions of unknown complexity. The ever-present stress in his work is compounded by normally working a rotating shift system in a physical environment of semi-darkness and extraneou~u10ise. How does such a man react when additional stress situations are generated by his family and home? How does the controller in a state of stress behave towards his family? How much does stress in the home affect the controller at work and impair his efficiency? Let us consider just some facets of the problem, namely shift work, financial problems, relationships and matrimonial problems.

Shift Work This is necessary to provide an extended service, normally required 24 hours a day, seven days a week. Shift lengths and types of shift cycle vary by country and even by unit, but they often clash with normal diurnal body rhythms, and with the establishment of healthy stable sleep patterns. To change shift cycles to conform more to diurnal rhythms might provoke resentment from controllers as being socially unacceptable, and might be resisted as apparently giving less free time away from work. However,

shift work does lead to disruption of family life, particularly when there are children in the family. Shift work may be considered sociologically advantageous in as much as it permits more contact with preschool children, but once the children reach school age any advantage is lost, and the effects of duty times and essential sleep periods coinciding with weekends are felt to th~ full. When considering rest and sleep, the presence of young children may lead to sleep disturbance and result in tiredness. Family life can be affected because the children are forever being admonished to keep quiet. Even when no children are present, normal daytime environment noise may cause sufficient disturbance to lead to excessive fatigue. The beginnings· of longer term problems may be traced to the choice between accepting such fatigue or seeking relief with a mild sedative drug. These are only a few of the factors which add to the complexities of everyday life when one of the partners in a marriage is a shift worker. It must be remembered however that these complications are aggravating an existing problem for anyone whose work Is In itself stressful.

Financial Problems Controllers, like others, feel entitled to reasonable remuneration for their work, and like others they judge what is reasonable by the maintenance of differentials as well as by absolute amounts. ~ersonal ~lrcumst~nces vary, and we 11 have financial worries from time to time. The controller, : nature highly responsible, can be expected to be cons~ ntious about remaining fin an cl ally solvent. It follows cie t when he experiences f"manc1a • I d"ffi th 1 1cuIt Ies he ·1s likely t a be subject to stress. In addition, the controller has a 0 stant worry about job security, since he must pass an con ual .medical examination, and he knows that with lnann ing-• age he will find it harder to cope with his job. creasmajority of countries • st'll · · The 1 have Insu ff'1c1ent saf eguards, eh as provisions for early retirement or second career su • Consequently, any temporary financial problem tra1mng. viewed in a context of long range financial insemus t be d t' t . t .. curity. Such worries are not con uc 1ve o mam ammg an untroubled home environment.

Relationships 8

use of the nature of his work, a controller may

ec~ome after •a bad day at the office', with the assor~t~r~ symptoms reflected in his relationships with his wife crade family. He may be irritable, listless, and generally to adjust to normal family activities. As he starts and finishes work at odd hours, these problems may become especially apparent when compared with those of the rest of the family. Social life Is often disrupted by shift work, particularly where such regular activities as clubs, evening classes, and sports are concerned. As a result, the families of controllers may tend to become isolated from their neighbours or each member of the family may be driven to individual activities so that both the partnership and the family be-

~~able

come less cohesive. A controller's social life may be centred on other controllers, because they share the problems of shift work and odd working hours, but this may· not improve relaxation if it means that much of the controller's leisure time is spent talking about his work.

Matrimonial Problems Shift work and high tension may disrupt sexual relationships, and this may lead to increased stress and mutual recriminations. It is unreasonable to expect that the typical controller's wife can endure marital problems which can be traced to the controller's job, without reacting against his work and working conditions, and ultimately against him. There are no figures available to show whether controllers as a group have more matrimonial problems than other professional groups, but there is a strong impression among controllers that matrimonial problems figure prominently in many controller's lives and careers. In most countries, matrimonial laws dictate that the break-down of a marriage is followed by a period of at least three months and often up to four years or more of intense pressure while legal problems are settled. As a result, an emotionally charged situation with all its associated anxieties is prolonged. Naturally, individual cases vary a great deal, but there must be concern over the extent to which the efficiency of a controller caught up in such a situation can be impaired by his preoccupation with it. The problem of the risks posed by a harassed or emotionally disturbed controller can be expressed in terms of flight safety: is it still as safe for the public travelling by air if key personnel controlling their flights may be preoccupied with impending bitter divorce proceedings?

Steps Towards a Solution Further examples could be quoted, suggesting the cumulative effects of family stress and work stress on the controller, but the points already made should suffice to demonstrate the existence of a problem. The task now is to find a solution. . An air traffic controller cannot be cocooned to protect him from normal social problems, but a way must be found to prevent the stress from such problems affecting him so much that he becomes dangerously inefficient. Perhaps an answer lies in the appointment of welfare officers working in close cooperation with the medical profession and trained to gauge the degree of stress present and its' cau~es. In any event, such welfare officers must be sufficiently independent of normal management to give advice without attracting any stigma from the controller or from management. Naturally if there were any suspicion that seeking or being given advice could affect a controller's career adversely, the effectiveness of the advice could be seriously jeopardised. However, before management can b~ a~proached with a proposal to set up any sort of organisation to cope with these problems, more information is ne:ded. Controllers themselves can hardly initiate a study which would be accepted as truly unbiassed; in any case they are not qualified to carry out such a study or to evaluate its findings. It is to the aviation medical profession that controllers must turn to initiate a study and present to the relevant authorities the findings and recommendations as a matter of urgency. This paper is based mainly on a combination of close observation and personal experience. It is hoped that it will stimulate to further study. Lives may depend on it. Footnote: Mr. Soar's paper was prepared for and presented to the XXlllrd ICASM Meeting held at Acapulco, Mexico, September 1975.

Birds in Flight: Radar Observation And Avoidance Procedures Which Can Be Employed By Air Traffic Controllers by Marc Laty, Biologist. S.T.N.A. 2. N., France General Birds in flight constitute a dangerous hazard which is of growing concern to air navigation. The present characteristics of air navigation make it necessary to locate this hazard accurately in space. Radars of 23 cm wave length, used for the surveillance of air traffic, provide the necessary indications which are often sufficient for the detection, under certain conditions, of birds flying either in isolation or in a group. If the controller is properly trained he can, from the image displayed on the radar screen in a control room, identify the echoes caused by birds. He can then transmit this information to aircrews. The information can possibly be supplemented by advice on the appropriate avoiding action to be taken.

Radar ·Observation Identification of Bird Echoes on a Radar Screen Many. luminous signals appear on the surface of 8 panoramic radar screen and there are no absolute cr't . f d t · · 1 ena ohr : erm ining those which correspond to birds. However t e s1mu 1taneous presence of certain data allow s th e ob-' . . server t o d 1stmguish bird echoes from other ph · w1"th su ff'1c1ent accuracy for the information t 0 benomena mitted. These are: e trans· positrons .. the type of distribution of the echoes and th err on t h e surface of the radar screen; .. . the persistence of the echoes in time, and their the rate of movement of the echoes across t mobility· of the screen; he surface . t ence of echoes the .effect of . MTI in relation to the pe rs1s during their movement; and

Migratory fligh t, the radar scr een is saturated by bird echoes.

the similitu de of appearance and disappearance on the screen at a distance which is a characteristic of the altitude of flight. P.n echo due to a bird, or birds, will appear on the surface of a radar screen in the form of a luminous spot which is persistent, locally suppressed or not by MTI , and w hose slow movement is made along a characteristic path at a speed of less than o ne hundred kilometers per hour. It should be noted that the characteristics of radars are not fully understood. Apart from the normal problems assoc iated with the choice of equipment . and calibration o ne may except two other phenomena, one being saturation at the centre of the screen (multiplying effect) and the other being differentiated detection, fo r the same targetanten na thus distorting reality. It has been proved that, in t he case of saturation, controllers have a tendency to reduce the d.etilc;ion power in orde r to eliminate echoes other than -those caused by aircraft.

In both the wintering area and the breeding area local movements may become established which are geographically well defined althou gh limited in distance. Local movements are determined in time and space by the position of the scource of food, the nest or colony and the dormitories or sheltering areas. They are characteristi c of a given species. As long as the same food source is used and the occupation of day or night dormitories occurs in a regular manner so the traverse of echoes of local flights wi ll follow the same paths from day to day. The distribution area of a species is constituted by the breed ing area and the wintering area between which migratory movements are made. The characteristics of migratory movements vary from day to day according to the species of the bi rds, their home territory, their destination, their fitness for fl ight and the weather condit ions. When migrations are observed the echoes belonging to the same migratory movement travel along tracks which are perceptibly parallel. The essential difference between local movements and migrations, when observed by radar, lies in the fact that the echoes associated with local movements are located in narrow portions of the screen whereas those connected with migrations are widely distributed over the whole screen surface.

Altitude Of Movements: Bands Of Altitude Dangerous For Air Navigation The average altitude at wh ich migrations are observed varies from 300 to 2,500 metres. The maximum altitude at which local movements have been observed is 400 metres. However, on local flight certain species may reach higher altitudes. For swifts and certai n birds of prey this can be of the order of 1,500 to 3,000 metres.

Use of Radar By Air Traffic Control Specialisation of Equipment

Characteristic Echo Forms With the exception of some species whose movements occur as massive flights, w hose dimensions exceed that of the radar reso lution cell, most birds move either in isolatio n or in groups of a few individu als. When the dimensions of the flight exceed that of the radar reso lution cell, t he echo fo rm may reprod uce that of the horizontal sectio n of the flight in its largest dimensior.. For example, the massive flights of starlings (sturnus vulgaris) leav ing their dormitory area or those of rooks (corvus frugileus) on migration present a characteristic arc of a c ir c le. Th e size of the echo is proportional to the size of t he f lock. When the d imensions of the flight are less than that of t he radar reso lution cell, the form of the echo is independent of that of the bird or group of birds. The echo form is then ovoid and small in size.

Habitual Forms of Movement Bird movements are marked by seasonal regularity c omprising an outward and inward flight (migration) between th e mot her country of the bird (the breeding area) a nd the living shelter (wintering area) where they spend that season of t he year w hich would be unfavou rable in t he breed ing area.

Control of air navigation and approach control for airports is effected by means of informatio n read off radar screens whose characteristics have been adapted to th e needs of the traffic. With present radars of 23 cm wave length the effective rang e for the detection of bird flights varies from 0 to SO nautical miles accord ing to the parameters approp riate to the targets and the radar station. For en route control the .s of the order of 200 NM and the range of the radars 1 controller normally uses the maximum range. Th is means that any bird phenomena will be fou nd compacted towards the centre of the image. For terminal co ntrol th e radar range is of the order of 100 NM and the controller normally

Your Chance to try for the 1976 writing award for the best article published in THE CONTROLLER. Entries must be received on or before the 1st September 1976. Scope: all original articles relating to ATC, not exceeding 4000 words. Only Air Traffic Controllers are eligible for the yearly writing award. Start writing now!

uses 40 ± 10 NM, a scale of radar coverage which corres ponds with the useful range for bird detection. The evo lution of e n route radar towards synthetisation of images, w ithout any special s ign to repo rt the presence of birds, enta il s the risk that the controller will no longer see the hazard s presented by birds. As a synthetic imag e is not predicted for terminal control the bird phenomen a will remain v isibl e to the controller.

Specialisation Of Personnel Control En Route

The indifferent display of bird phenomena on en route control radar screens which are set to total radar range does not, however, nullify a co ntroll er's interest in the identification of birds. In effect aircraft w hich by reason of their cruising altitude are, to all intents and purposes, beyond any bird risk w ill enter the critical altitude band at the moment of descent. This information w ill then be very useful. Control In the Terminal Area

The controller sees a processed (MTI), but not synthetised, image of air traffic and bird movements simultaneously. However, the landing and take-off rate at ce rtain airports eliminates any permanent possibility of the co~ troller being dist racted from his surveillance of air traffic for more than a moment. Moreover, there is only a short useful tim e margin between th e moment w hen the aircraft passes from en route control to terminal control and th e moment when it penetrates the dang erous altitud e band. When local bird movements in the immediate neig hbourhood of an aerodrome have been th e s ubj ect of sp~ c ia l studies. the terminal controller must be aware of their c haracteri stics (tim es, places, altitude, frequency, etc ....). If he is fully aware of the danger presented he can t~en act with mu ch greater efficiency. Despite the short acti on time availabl e he can transmit t he inform atio n necessary for a manoeuvre intended for the avoidance, or th e reductio n o f the co nseq uences. of a possible co llis io n as soon he notices on the radar screen echoes of birds on local ~~ghts which co uld inte rsect th e fli ght path of the _aircraft. In v iew of the fact that, fo r a given radar station , the the passage Of migrating birds may last severa l hours, . te rmin al con troller shou ld trans mit this information to en ro ute control as soon as he has the tim~ to do so, rath er · ·t at short notice · directly to aircraft on descent. th an give 1. Then t h e en r Oute controll er • w ho does have the necessary . th e various crews concerned a nd give time, can a d v ·se 1 th em adeq uate notice.

Desirable Qualification . . safety in respect of coll isions Imp rovement 1n air . . aft can be gained through instruc tbetween birds an d aire r I This train ing is necesing and trainin g control pe~so nn e . nomena which are sary s in ce it explains certa1~ r~dar pht~e e uipment. It is often attributed to th e fu nct ion in g of q a strange fact th at radars _are _often declared to be un. bi d ·ng major migrations. serv1cea e un . . k"ll ·n the recogn itio n II an acquire a certain s I I A contro er c . of instruction such of bird echoes by undergoing a courne d tw ice each year as is given during the cou rses organis~ . t'on Sud-Est 1 in Fran ce at t he Centre Regional de la aviga .d tT ~ at Aix en Provence. Once bird echoes have bee n i en i ie by the cont ro ller, he can tran sm1·t (o r cause to be trans-

Loca l f l ight of herri ng gulls in the Marseille area. The gulls' echoes draw a "V" on the radar screen.

mitted) information o n the existing danger to crews concerned. The time required for observation and trans mission of the inform at io n is relatively short and can perfectly well be incorporated into the data prov ided by en route control. Where t erminal control is con ce rned , observation and transmission of sudden information reg arding fully known local bird movements can be made w ithout overloading radio traffic. Info rm at io n r elated to mig ration movements can be the s ubj ect of information which is supp lementary to that already disseminated by e n route contrc l.

Appropriate Avoidance Procedures The procedures, assoc iated with the type of contro l. may be put into two general categories: i:ass ive procedures or amendments to the fl ight plan made before or d uring the flig ht and active proced ures carried out in flight when a hazard is positively identified.

Passive Procedures These procedures are quoted for referen ce. They cover two aspects according to w hether t he changes are made systematically or as required. Systemati c changes apply particularly to train ing flights. They co ncern either limitation of flights at times or a ltitudes or else a change of route when the information ava il able to the c rew shows: the presence of a large number of birds in given areas during certain regular pe riods (local movements). or the presen ce of a large number of birds in a ce rtain altitude band (mi gratio n). Special changes app ly either to a cancellation of a flig ht, such as an interruption of take-off due to the presence o f bi rds on the runway, or to a delay as in the case of an interrupted approach or even a d iversion when migrating birds choose a particu lar airport as a staging point.

Active Procedures These procedures apply above all during t he approach phase. They are experimental a nd have not been the subject of systematic evaluation trials . Certain procedures concern changes in present flig ht pro ced u res. For example. a redu ctio n in approach speed

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would tend to reduce the seriousness of damage in case of impact. Radar guidance can also be used in so far as it is possible to determine the height at which birds are flying, the type of grouping and the real importance of the groups. Below a certain flight level (FL 100) use of the landing lights can cause birds·· to change course and so improve safety during the approach phase.

Conclusions The fundamental study of bird movements cannot be made by a radar controller who has neither the requisite training nor the necessary time. It calls for a specialist. The work of the specialist(s) should lead to a better knowledge of bird movement patterns for the purpose of forecasting movements and setting up a system of daily forecasts. All radar controllers could be trained in direct interpretation from an ordinary screen or from any other system stemming from synthetisation of images so as to contribute to much greater efficiency in the prevention of bird strikes. The maximum benefit from this training could accrue to terminal control radar which is concerned with the part of the flight where the risk is greatest and whose equipment is best adapted to the observation of birds. It will be necessary, by means of basic studies, to seek a better understanding of the variable factors which condition the behaviour of birds. In case of risk the attention of the controller could, without elaborate specialisation, be directed towards surveillance of the phenomena in a situation of potential conflict. These studies will likewise aim at the development of display systems, which will be needed when screens are synthetised, so that the controller, freed from routine tasks by automation, will have the time necessary for the resolution of avoidance problems.

Comments on Air Traffic Control Heard Around The World Michael V. Huck, Director, Air Traffic Control Department, Policy and Technical Planning Division, Aircraft Owners and Pilots Association (US), on: "Do we need the new ATC goodies?" One of the great needs for tomorrow's ATC system is increased capaeity to handle the forecast demand which is expected to result in a fivefold increase in operations by the 1990s. There are a lot of promising system components that are under development that show great potential to achieve this phenomenal increase in capacity. Unfortunately, enthusiasm for some of this gear is such that the potential increase in capacity that can be achieved is grossly overstated. Perhaps the greatest "untruth" that has been foisted off on the aviation public is that the plan· ned automation of the ·system can provide the required capacity and still keep the human controller actively in the control loop. This is the same type of propaganda as that passed out to airline captains when they reject autoland capability in modern jet transports. Of course, since they no longer wiggle the stick, their image must change from the crooked smile with straight teeth hairy chested type to that of manager. Well, if that keeps his ego nice and shiny, I'm all tor it, but there is some point in the operation of changing that firebreathing monster from an airplane into the world's fastest tricycle where all the manage-

ment ability in the world wilt be unable to keep a malfunctioning autopilot from bashing him into the ground. For this reason, the autopilot cannot be allowed to fail. It is also thus with an automated ATC system. Are we willing to operate an ATC system where the human controller is reduced to a monitor of the automated system who, when alerted by a flashing malfunction light, sweeps the cobwebs from a microphone lying in front of him and hollers on a universal frequency "You'all be careful, hear?" If we can accept this concept, then we will need all the planned products with substantial redundancy. If we cannot accept the 2001 year philosophy, then some of the new products will be useful as tools for the human controller, but the whole package will be vastly more sophisticated and expensive than necessary. The new goodies that offer operational benefits, therefore, must be looked at very closely to assure that the benefits are worth the costs involved in implementation. The first bridge that must be crossed is the decision regarding the level of automation that we are willing to accept in the system. I, as a pilot, am not willing at this time to accept the premise that the system will ever have so many aircraft operating in it that a human controller will be unable to jump in when the equipment fails and unscramble the mess that is instantly created. For one thing, for such a system to have the necessary redundancy to guarantee a fail-operational capability, it would be so expensive that it could never pass the cost/benefit requirements. Secondly, there are enough common points in even a triple redundant system that it would take a lot of convincing to show me that any system would be truly failoperational. You may have gathered that I have made a decision, at least in my own mind, and you are correct. I feel that the limiting amount of traffic that can be in one hunk of airspace at one time must be related to the amount of traffic that can be safely separated by a control team at a given sector with the amount of aid that can reasonably be expected to be available. If everyone will accept my desire for a requirement for human intervention in tomorrow's system, we have made great strides of progress. I suspect that this may not be the case, however, so let me try to convince you that there is no real need to provide the system with much greater capacity. There is some evidence to suggest that the population of the United States is deploying itself around the country instead of perpetuating our current urban sprawl. If this trend continues, the pressure for greater system capacity may be somewhat relieved; it just might alleviate t~e congestion that occurs today in only a few of our maior terminal areas to the extent that despite a rather rapidly growing number of operations, there might be a lessening of our ATC problems. The thing that will make this possible is the general aviation aircraft. The fastest growing measurable segment of aviation is general aviation instrument operations. A large portion of the growth is the result of an increasing awareness that you can go where you want when you want in a general aviation airplane. I expect that this awareness will spread geometrically, and we will see a very rapid decentralisation of our population. The only reason we gathered in large cities in the first place was to be close to goods and services. With today's attitudes, you can't get a plumber or TV repairman even in the city, so why not be frustrated in a small community where you can at least breathe.

A second limiting factor for the need of increased capacity is the cost of airborne equipment along with the user charges that represent his cost of the ground based equipment. With the price of everything going up in our inflationary economy, the little guy just can't afford extra expense for his aircraft. Not only the pleasure pilot but also people who use their personal aircraft for business will find the cost/benefit trade-off will no longer pay off, and they will no longer be able to use the aircraft to enhance their ability to do business. It seems to me that we are on the verge of an era of technological hysteria. By that I mean that we are inclined to implement "system improvements" as the state of the art allows, without considering whether the "improvements" are actually desirable or even necessary. There is no ques-

lion that some of the new goodies can and should improve safety and operational capability in tomorrow's ATC system. However, each innovation must be carefully cons:dered from a cost/benefit viewpoint, and only those w hi ch clearly come out on the plus side should be considered. At that point, determination as to whether implementation would result in user benefit or system enhancement must be made. If the improvement will result in operational advantage to the user, it should probably be implemented. If, howeve r, it just seems more tidy to change someth ing and no benefits to the user can be realised, it should be scrapped with no regrets. It is only with very careful scrutiny by all part:c:pants in the aviation system that we can be assured that our race horse won 't closely resemble a camel.

Airports and their Control Towers (4) ·- ,--- - ----------·- --··--- ------ ---

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The Dallas-Fort Worth Airport Tower The $ 2,6 million air traffic control tower at Dall as-Fort Worth Airpo rt is the ai rport's focal point and nerve center. Designed by Walton Becket and Associates for the Federal Aviat ion Administration , th e 196 foot structure was designed to be a national standard facility, and the tower represents the first installation of the prototype design. It has become a punctuation mark on the prairie midway between Dall as and Fort Worth. To minimize the costly changes of obsolescence, it was decided to design a stru ctural tower comprised of fo ur ser-

vice co res topped b th t . . . Y e ewer cab, an d eq uipment floors con tain i.ng mi crowave and other essential air traffic control devices. Des· f th t . . . ign o e ewer perm its future modification o.f th is equipment witho ut the necessity of changing the basic structural system This is important c 'd · . · ons1 enng the rapid technologi cal develo pments that have occurred in recent years and which are expected to continue. FAA developed th~ specially designed 11 sided cab configuration as part of its overall new con cept in airport control tower design.

Constructed of locally manufactured concrete, the service cores consist of hollow modular units - 10 feet square and 7 1h feet high - weighing 20 tons each. The archit.ects prnplanned the units to be of a size and weight easily trucked to the site. A 200-foot crane stacked the modules on top of one another; they were then post-tensioned, and grouted into place to form the service cores. These cores house the elevator, exit stairs, and communication and power cables. Cores are connected at 15-foot incremznts by steel work platforms which provide easy access to the equipment inside. Directly below the cab are four quadrants of microwave space containing the discs and equipment necessary for airport control tower functions; these spaces we re des:gned to provide 360-degree visibility for the microwave antennas. This level also is the terminal floor of the elevator with access to the junction level and the cab. This design concept was developed for major activity level airport traffic control towers and is generally applicable for airports with 100,000 instrument operations annually or greater. The massive concrete base building with its glass enclosed courtyard has 26,000 square feet of space and incorporates administrative offices, training facilities, shops, and a reception area. Positioned between earthen berms and retaining walls. the tower's base relates to the surrounding land scaped

areas and airport access roads. All mechanical equipment and support areas are located on the outside perimeters of the base buildi ng to allow easy maintenance, with offices and train ing areas oriented to the tower and an inter ior court. The undecagon design of the cab provides the greatest possible flexibi lity of operating positions and cab configuration for obtaining the best visibil ity at all positions. This design most nearly approaches a circle and provides maximum floo r space with good upward and downward visibility. Noise is reduced by the odd number of sides, as there is no t rue opposite reflecting side to the structure. A double cab, in effect, is accomodated within t he spac ious, low profile cab to serve the dual set of runways. This arrangement perm its controllers to work in dependently in duplicate positions on either side of the cab to handle the traffic using their respect ive runways. Staffing for this Terminal Rada r Control (TRACON) Tower includes 120 air traffic controllers and supporting personnel. Approxi mately 57 electronics technicians work on FAA equipment on the airport and at the two radar (ASR) sites. The new standard design of the Tower, when employed on a national basis, should offer better construction quality control, greater speed of completion and the ability to change economically in t ime as new and different equ ipment is required for Air Traffic Control.

News From The Federation IFATCA Regional Meetings The value of holding Regional Meetings within the framework of the Federation for the discussion of specific regional matters was underlined In November 1975 by two gatherings of representatives from several European countries.

The first meeting took place in Malmo, Sweden, under t he auspices of IFATCA's Regional Councillor for Western Europe, Mr. G. Atterhol m, and was widely reported by the

Swedish media. A well attended press conference concluded the event, where ten European countries were re presented. The second meeting to repo rt was organised in Vienna by IFATCA's Regional Councillor for Eastern Europe, Mr. Erich Schyr, and supported by the Austrian Association. Attending were representatives from th ree countries plus an observer from the Austrian Federal Office of Civil Aviation. Among the points discussed at this meeting were " Regional Organisat ion and Recruitment of new Member Assa-

Seen arrivi ng for the press conference are, from left to right: Oli J 6 nsson IFATCA Vice-President (Technical)': Gunnar Atterholm, IFATCA Regional Councillor (W. Eu rope) ; Hans Stang, German ATCA; Daniel Gorin, President French ATCA; Larry Curry, Master British Guild ; and Phi lippe Rahm, PreÂˇ sident Swiss ATCA.

At a lighter moment of the meeting , shown from left to right : M . Ernst, Editor Austrian ATCA; E. Schyr, IFATCA's Regional Councillor (East Europe) and Secretary Austrian ATCA; I. Zerkovitz, Vice-President Hungarian ATCA; K. Kihr, President Austrian ATCA; A. Zechmeister, Austrian Civil Aviation; E. Voit, President Hungarian ATCA; B. Dujmovic, President Yugoslavian ATCA; A. Petricevic, Regional President Zagreb Area, Yugoslav ATCA; and T . Karner, Secretary Yugoslav ATCA.

ciations" , "Development of Air Traffic and Traffic Flow in the Region", and "Inter-Area Difficulties". It was decided to meet again in November/ December 1976, most probably under the auspices of the Hungarian Association in Buda-

The above Meetings proved to be very successful and attending representatives were in agreement that the discussions held had been useful to both the Federation and the Member Associations concerned.

pest.

The Air Traffic Controller in Aircraft Accident Investigation

by H. H. Henschler, Supervisor Edmonton Area Control Centre, Canada •

Introduction Air Traffic Control, since its inception a little over thirty years ago, like all other aviation-related fields and indeed most fields of human endeavour and science, has gone through a period of continuous evolutionary change and development. Many factors have combined to help enhance and develop the ATC system. They were of an originally military nature such as radar and IFF or arose from the desire to transport people and cargo at a higher rate of speed or in greater numbers or tonnage. The first major enhancement to the ATC system came about in the fifties when surveillance radar was made available to civil Area Control centres and Terminal or Approach Control units. Before the introduction of rad ar • This Paper was presented to the Sixth Annual Seminar of the Society of Air Safety Investigators, Ottawa. 7-~ <;>ctober 1975. on b h If of the Canadian Air Traffic Control Assoc 1at1on (CATCA) and · Air Traffic Controllers Organ ization (PATCO. USA) . e ap f t h e ro ess1ona 1 . The author, who is IFATCA's Regional. Councillor for N.orth and Central America, is also a past Vice-President of the Canadian Association, and has represented Canada at a number of !FAT.CA Conferences in recent years. Since 1973 he has been Chairman of IFATCA Standing Committee VI. . Mr. Henschler began his ATC career in Hannover, Germany , in 1959 where he qualified as an IFR controller In Hannov~r ACC in 1962. In 1967 he emigrated to Canada and was employed first in the E~ monton and Calgary control Towers, to become an IFR contro.lle_r in Edmonton ACC in 1970, and a Supervisor in 1973. His spec1al1~ed training as a controller includes six Electron i~ Da.ta Processing Courses and training on the JETS System which is being introduced in Canada. He has studied psychology and polit ical Science at the University of Alberta, Canada.

Mr. Harri H. Henschler

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and indeed still today in areas without radar coverage, air traffic was and is moved in accordance with rigid procedural separation standards. These standards, when applied correctly, provide safe separation between aircraft but result in "wasted" airspace when the numbers of aircraft which can safely be separated in a given area are assessed. Obviously, by virtue of "seeing aircraft" in the form of a radar return on the screen rather than having to visualize their relative positions, an air traffic controller can accept the responsibility of separating a greater number of aircraft at any given time in less airspace. Radar, however, brought about another important change. For the first time ever the controller, now using radar, was made responsible to provide separation between aircraft and the terrain with the introduction of minimum radar vectoring altitudes which were below either the minimum enroute, or minimum safe altitudes displayed on the pilot's charts. Up to that point It was the pilot's sole responsibility to ensure that descent and climb in close proximity to the ground or water was conducted so as to avoid contact with terrain, except of course the right kind of terrain, the runway. In addition, with the provision of terrain clearance, controllers were charged with providing another, potentially dangerous service. Radar provides a return on the screen f~om cumulus clouds and precipitation. I just said ,.a potentially dangerous service". The reason for this is that because of certain necessary and desirable design restrictions ATC radar systems will not necessarily display all areas of cumulus activity or precipitation. As a result a controller may attempt to provide an aircraft with a steer, called a r~dar v:ctor, around such areas and in reality vector the aircraft mto cumulus activity not displayed on his screen. A few years after the introduction of civil ATC radar systems, the first commercial jet aircraft came on the market. This. major step in aviation history doubled the speed o! a portion of_ the commercial air traffic while the slower piston and turbo..;.prop equipped aircraft continued to be used. T~is mixture of aircraft types and speeds did nothing to alleviate the air traffic controller's problems. It requires a great amount of predictive ability to make maximum safe use .of a given airspace. While the number of large conven~1onal transport aircraft is diminishing, relatively slow ~u~mess ~nd general aviation aircraft are being produced '". m.cre~sm~ numbers and the problem of type and speed mix is still with us, albeit primarily in the terminal areas. . ~any ~ontrollers who worked in the late fifties and early s1xt1es will testify from personal experience to th _ • • wh e over e 1mmg increase in traffic density. Of course statistics ·n'vo Ivement, are h available which, without any personal 1 s ow that the density of air traffic in North America has increased at least threefold with an even larger increase in the total number of passengers carried, both commercial! and non-commercially. Y In the middle of the nineteen sixties the concept of gro~nd-based computerized ATC systems began to become

reality. In the United States, the National Airways System (NAS) was developed, predominantly for enroute control. Later, ARTS (Automated Radar Terminal System) was added .. In Canada, the Joint Enroute Terminal System (JETS) is scheduled to go into operation starting in Eastern Canada and progressively moving west, within the next year or so. These systems are generally based on the use of radar-derived information which is digitized and displayed on the screen together with a computer generated "data

block". This data block, in addition to providing the aircraft identification, type and computed speed, will indicate the aircraft's "real" altitude. The altitude is derived by converting secondary radar pulses, which are carrying information from an airborne pressure altimeter, into digital form. This process allows the controller to keep a check on the aircraft's real pressure altitude rather than relying on pilot-reported altitudes.

The Shift of Responsibility from the Cockpit to the Controller Again, responsibility has been shifted from the cockpit to the controller. The fact of terrain clearance can now more accurately be established. The occurrence of less than minimum vertical separation can be detected. Pilots are bypassed by a piece of hardware which reports directly to the ground facility. Controllers thus have available to them a continuously updated .. real" altitude. This new capability, together with the "traditional" radar display of range and azimuth, changes such a new ATC system into a "real-time" three-dimensional display. We all know that, in addition to being able to transport a greater number of passengers per flight more comfortably, the fairly recently introduced wide-bodied jets and the development of "stretched" versions of first generation jet transports have brought us the problem of wake turbulence. Wake turbulence, its prediction and detection, has itself been the subject of many papers, some of which have been presented at seminars of this Society. So far, however, no practically proven way of detecting or predicting wake turbulence has been found. Until such time as it is, responsibility for providing a specified minimum standard of separation from the possible effects of wake turbulence created by one aircraft on other air traffic rests with the air traffic controller. To assist him with this task, specific and increased minimum separation standards relating to those aircraft types which have been found to generate the greatest amounts of wake turbulence have been introduced, and as a matter of interest the standards have been substantially increased during the last year. These standards, like all ATC separation standards, only indicate the minimum separation required. If, in the controller's opinion, such minimum standard is not sufficient to ensure safety, he is obligated to increase the minimum separation. While such permissive minimum standards are necessary, they carry an inherent danger to the controller applying them. The wake turbulence standards, jn particular, can be cited as examples. Many variable and often unpredictable factors (such as surface wind shears, etc.) influence the formation, duration and direction of travel of aircraftgenerated vortices. The controller has to take all these variables into consideration when deciding on the separation he will use. Sometimes, as evidenced by aircraft accidents due to wake turbulence, his decision is a wrong one, almost always because of some factor or factors unknown to him when his decision was made.

Controllers will Face added Problems in Years to Come We find ourselves at the start of a new era in aviation. The British-French built Concorde supersonic transport has commenced scheduled services and training flights have been made in preparation for a scheduled service between

Europe and North America across the crowded North Atlantic. While during the supersonic enroute portion of the flight t~e SSTs will be utilising much higher, and mostly unused, altitudes than present traffic, they will have to be integrated in the stream of other traffic during both the departure and arrival phase of their flights. We predict that the introduction of scheduled SST operations will add to the problems controllers are facing now. The operating characteristics of SSTs do not allow for extended subsonic flight which may become necessary due to other traffic. The SST requires a steady and rapid climb to and descent from its cruising altitude. Any diversion from this profile could have an adverse effect on fuel consumption and schedule. We have been told that, under normal circumstances, the scheduled introduction of SSTs should pose no problems. But air traffic controllers, under normal circumstances, have no problems. It is the everyday, everyhour non-routine situation which makes this profession one of the most critical and which creates the tension and stress and their resultant effect on the controller which is of real concern to us. I am certain the above examples illustrate sufficiently the shift of responsibility from the flight deck to the air traffic controller. Recent accident investigations have led to the NTSB (U.S. Accident Investigation Board) and public pressure for the controller to accept even more responsibility in the areas of terrain clearance, wake turbulence, and go/no go decisions based on weather conditions. In this new and ever-developing role, the air traffic controller is more likely than before to be suspected as the cause or contributor to, however peripherally, an aircraft accident. Therefore, air traffic controllers must assume a new role, namely that of a participant in the investigation of those aircraft accidents where there may be an ATC involvement. Pilots have, through their Associations, traditionally "enjoyed" this right. As long as aircraft accidents could only be caused by pilot error, mechanical malfunctions, or weather, this may have been sufficient. But now a new dimension has gradually been added to the possible cause of accidents and air traffic controller participation in investigating aircraft accidents has become a practical necessity. I will now outline three areas where we believe air traffic controllers, as specialised professionals, can be of immeasurable value when participating in aircraft accident investigations.

The Controller as a Source of Information Air Traffic Control systems in most parts of the world, are now highly sophisticated entities which a non-controller cannot readily understand or even learn to understand given the restricted time frame which accident investigation boards operate under. No longer is the only evidence available relating to Air Traffic Control a transcript of or the actual voice tape recording of radiC? or telephone conversations, the flight progress strips which require manual updating or the testimony of air traffic controllers. With the advent of computer-based Air Traffic Control systems, computer-generated magnetic tapes are now available for a blow-by-blow replay, almost as soon as an accident occurs. In several cases recently where the aircraft flight data recordings have been damaged or destroyed these tapes have been used in their place to reconstruct the final portion of the flight.

Traffic co-ordination between sectors of the same ATC unit is accomplished mainly via recorded hot lines rather than controller-to-controller personal contact. It has been suggested recently that area microphone systems be installed in ATC units. These systems as suggested would operate in a manner similar to the cockpit voice recorder systems now in use in commercial aircraft and would record conversations taking place between controllers in an Air Traffic Control unit. This suggestion originated from an investigative body hearing fragments of controller conversations in the background when listening to the radio and telephone recordings while investigating a recent aircraft accident. While CATCA and PATCO are both opposed to the introduction of area recording systems on the grounds of infringement of the controllers' privacy, the suggestion of their introduction alone proves the value of the controller as a source of information. However, regardless of whether or not we will ultimately be faced with area recording systems in ATC units, the existence already of computerderived magnetic tapes and other related evidence requires that an expert in the field participates in the investigation of any aircraft accident where Air Traffic Control may be involved. Only the expert in the field, the professional air traffic controller, can interpret, translate and explain to the non-controller the intricacies of the system and the situation, control-, stress-, and traffic-wise, which existed at the time.

The Controller as a Factor in Aircraft Accidents I have detailed in the foregoing parts of this paper the substantial and continued shift of responsibilities from pilot to controller. One has only to look at manned space travel, let alone unmanned space travel, to detect startling similarities. In manned space travel, as witness the recent ApolloSoyez mission, all manoeuvres are initiated and directed by the ground-based mission controllers. The task of the astronaut or cosmonaut in the actual manoeuvres of the craft is to add the finishing touches, much like a pilot executing a landing after an automatic approach to the runway. This analogy, although some pilots may resent it, will become more and more accepted as funds are appropriated to develop advanced ATC systems. If these new systems in the future continue to make more information available to the controller, and give him a greater capability to take action, it appears likely that as in the past it will continue to be preferable to have one person with the whole picture make the necessary decisions and take the necessary action, rather than a large number of individuals acting independently with the resulting possibility of chaos. Regardless of these future possibilities and the fact that to date airborne system development has sadly outstripped the capability of ground-based systems to keep pace, one has only to look at the past several years. A large number of aircraft a~cidents in those years have r~sulted in a large amount of time during Accident Investigations. being devoted to the detailed reconstruction of ATC actions, and in some cases long and involved legal battles, with air traffic contr~llers being sued for large sums. A few of the cases of which we are aware are detailed in what followsÂˇ April 22, 1968 Vancouver B. C. Piper Aztec (Wake Turbulence Upset) November .11 â&#x20AC;˘ 1969 Wabush, Labrador De Havilland 125 (Incorrect instrument approach) July 6â&#x20AC;˘ 1970 Toronto, Ontario DCS (Heavy Landing)

January 9, 1971 Edison, New Jersey B707/C150 (Mid-Air Collision) May 30, 1972 Fort Worth, Texas DC9 (Wake Turbulence Upset) December 8, 1972 Chicago, Illinois 8737 (Stalled on Approach) December 29, 1972 Miami, Florida L1011 (Disconnected Autopilot) March 5, 1973, Nantes, France CV880/DC9 (Mid-Air Collision) Juli 31, 1973 Boston, Mass DC9 (Collision with Sea Wall)

Whether investigation of most of those accidents mentioned in the foregoing proved there was no real ATC involvement as a factor is immaterial. Where it was a factor, there remains the question of possible misunderstandings or lack of system understanding on both the pilots' or controllers' part.

The Air Traffic Controller as an Investigation Participant Both CATCA and PATCO, in their respective countries, have been granted by their respective authorities the right to member or party status on aircraft accident fact-finding boards where Air Traffic Control involvement may be indicated. Both associations are actively training selected members, in many cases elected association officials, in the science and techniques of aircraft accident investigation. One of the problems our associations are faced with is that to the best of our knowledge no specialised courses in the science of aircraft accident investigation for air traffic controllers, as it relates to their profession, are available anywhere. Given the increased involvement of controllers, their changed role in aviation and consequent contribution to the investigation of aircraft accidents, there is an urgent need to provide formalised training to air traffic controllers in the science and techniques of aircraft accident investigation. In our opinion there is an obvious necessity for those universities and government agencies which already offer courses in aircraft accident investigation to develop courses tailored to the specific requirements of air traffic controllers participating in aircraft accident investigations. These courses should be aimed at a systematic procedure of gathering the facts available on the Air Traffic Control aspects of the accident. We call upon ICAO and the civil aviation regulatory and investigative bodies of all nations to prepare courses and offer training in the specific field of ATC in aircraft accident investigations and to encourage private institutions to do the same. Controllers must have available to them the experience, the science and the techniques of investigating aircraft accidents, for we will be participating, one way or the other. We call upon you, the established Society of Air Safety Investigators, to render us all the assistance possible to fulfil our aim. To this end we, both CATCA and PATCO, are now or will become members of the Society in the hope that our participation will add to the already awesome body of knowledge and experience evident in it and that we may benefit from that knowledge and experience which you al ready possess. Now we have arrived at a turning point. Your specialised profession, that of air safety investigators, has admitted into its ranks our specialised profession, that of air traffic controllers. In return both the Canadian Air Traffic Control Association and the U.S. Professional Air Traffic ControllersÂˇ Organisation pledge to do their utmost to make our new and changed relationship an enjoyable one, a close one. based on mutual respect and the knowledge that no one person can know or understand everything in all fields.

What A Controller Should Do In The Event Of An Accident 1. Request immediate relief from position. 2. Request immediate Association representation. 3. Listen to tape with the Association Representative take notes. 4. Do not make any statement - written or oral - after first listening to tape. 5. If you are given a direct order by management to make a statement, then only outline the pertinent facts: name, address, control position, time, etc. Because you may not be in possession of all the facts, avoid a detailed statement at this point. 6. Steep on it. The trauma of the crash may interfere with normal memory, judgement, and concentration. An alert, clear mind is a necessity. 7. Next day - relisten to tape with Association Representative and write a rough draft of your statement. 8. Check the rough draft over with your Association Representative before the statement is finalised and submitted. 9. Conclude your final, written statement with the sentence: "I reserve the right to change my statement if further facts are forthcoming." (adapted from a PATCO directive)

'Saves' by Air Traffic Controllers One hundred and thirty seven air traffic controllers of the U.S. Air Force Communications Service were credited with saving 72 aircraft involving 279 persons during 1974. The AFCS air traffic controllers were cited for either warning pilots of dangerous situations developing or guiding distressed aircraft to safe landings through the use of radar or visual sightings. Involved in the 1974 "saves" were 43 military and 29 civil aircraft. The monetary value of the aircraft involved was more than $ 145.8 million. Since AFCS was activated in 1961, air traffic controllers - operating at bases around the world - have been credited with saving 1361 aircraft worth almost $ 1.43 billion and carrying 4988 crew members and passengers. (HQ AFCS release)

Safe Altitude to be Monitored In the U.S. FAA will add a "minimum safe altitude warning" capability to all 64 of its automated radar terminal systems (ARTS Ill) to alert air traffic controllers to potentially dangerous altitude deviations by aircraft under their control. The system will automatically trigger a visual aural signal on the ARTS Ill when an aircraft penetrates or is about to penetrate a predetermined minimum safe altitude in terminal airspace. FAA has awarded a contract to Sperry Rand's UNIVAC Division for the hardware changes to all ARTS Ill units. UNIVAC will also make the computer programme (software) modifications on five ARTS Ill installations and assist FAA with this task at two other sites. FAA will then assume responsibility for making the remaining software changes. The contract schedule calls for hardware deliveries to begin in January 1976 and be completed in August. Among the first airports to get the system will be Los Angeles International, Chicago O'Hare, Washington's Dulles International, Detroit Metro, Oakland International and Houston Intercontinental.

The Pilot's Point of View ATC System Design - Which Way Should It Go? (continued} by Captain L. Zeyfert (Netherlands ALPA). After re-reading Vic King's excellent article (which was published in our February 1976 issue - Ed.), it would appear to me that the correct choice should be self-evident for IFALPA. But first, perhaps a bit of semantics is indicated. Semantics being defined, of course, as: "branch of philology concerned with meanings". System is defined in my dictionary as: "complex whole, set of connected things or parts, organised body of material or immaterial things" and further "system of philosophy = set of coordinated doctrines". Hence "systematic = methodical, according to a plan, not casual or sporadic or unintentional". A system, therefore, invokes in the mind's eye something planned and orderly coordinated, organised and intermeshing. The first option (the present concept) and the last (maximum freedom of operation, wherein ATC intervention is limited to potential conflict situations) do not qualify for the appellation: SYSTEM. The first option partially so and the last option entirely so. IFALPA already has a firm policy on Flight Rules. IFR is mandatory. VFR is rejected. Reliance on the "See and be Seen" concept for collision avoidance ls anathema!!! Philosophically, what difference is there between the last option and VFR? There is a physiological dissimilarity, as in one case human vision is used and in the other complex machinery based on electromagnetic radiations - but principally these concepts are the same: Proceed without coordination; if the traffic density is low enough, the chance of a conflict situation arising is sufficiently remote to permit sticking a map on the sunny side of the windscreen (a la Ernest Gann) or switching off (or accepting the unserviceability of) the airborne APWl/ACA~ and/or TSO devices. If the traffic density is higher, or 1f the pilot's trust in statistical chances more pessimistic, a more continuous visual watch is kept or the gadgetry kept switched on. With very high traffic density or a pilot with a very pronounced instinct of self-preservation, a continuous watch is kept (visual or electronic) and a conto. t .in uous avoiding action procedure has to. be resorted h . th Admittedly, the collision avoidance devices aving e advantage over the eyes of a constant rang~, unaf~ect~d by atmospheric obscuration, and being provided with information denied to the eyes (e.g. horizon reference ~nd accurate ra t e o f Closure assessment) resolve the . solution to a potential collision situation with grea~er c~rtainty. The Mark 1 (or Mark 11 _ i.e. with bifocals) have eyes, however, th tl the great advantage of reliability (assuming e curren Y . f or th e l"f 1e s pan of man .as 72 years actuarially used figure F works out at approximately 6.3 times ten. to the MT B · · · · d electronics the fifth - a figure not yet reached by mo ern . , solid state or not). The philosophy of Tactical .1nterve~t1on (by ATC or Collision Avoidance/Proximity Warning de~1ces) has been equated at a RAC/COM Study Group meeting t~ the provision of efficient bumpers (fenders to North Americans) to surface transport. . The second option, a SYSTEM of virtually full (strategi~) control, in which airspace "slots" are allocated to all air-

craft and ATC intervention is limited to incidental deviations from planned operations, meets all our requirements. "It gives the passenger what you have told him that you would give him, a flight from here to there in so many minutes. It gives the operator what he wants, something close to minimum flight time, and with least cost. It offers the controllers what they want, time to monitor the workings of the system, rather than be so involved as a part of the machinery that they have little left to see that it is working". I would add that it _gives the pilots that orderly, co-ordinated, organized, pre-planned environment so essential for the maintenance and enhancement of the "acceptable minimum level of safety", so inhibitive to producing symptoms of hypertension and gastric ulcers and therefore conductive to achievement of retirement age in the best of health and -due to the improved economics of flight - wealth. In quoting an old and yellowing file: The ATC clearance should be considered to be a contract between the system and the pilot. Presently available technology makes this concept already entirely feasible in the more sophisticated (qua equipment) areas. Forthcoming improvements in communication techniques (data transfer), computerisation in ATC, airborne navigational systems (area navigation facility coupled with INS), etc., make the world-wide adoption of such a system philosophy not only feasible but inevitable. An essential pre-requisite to the development of this system is the adoption of the concept of only controlled traffic being allowed Inside controlled airspace. (This has nothing to do with IFR and VFR as such. However, the presently possible situation in some TMA's of uncontrolled traffic being tolerated under VFR has to be terminated· simi~ar~y the unco-ordinated presence of military or Stat~ traffic in controlled airspace has to be eradicated). A single ATC Authority in any given portion of Controlled Airspace is therefore implied. Another essential prerequisite would be a ~NIQUE Time Standard throughout the world. Also essential would be the capability of co-ordination across boundaries along the whole route of every flight (political factors). In such an environment some sort of APWI equipment could be utilised, perhaps in conjunction with reduced longitudinal separation standards and in the absence of more sophisticated airborne navigation equipment. Present day Air Traffic Control is a mixture of Proce-

~ural (st~ategic) Control with a varying degree of Tactical intervention (Radar). The criteria for Procedural Control are 0 ~~dated and no longer related to the navigational capab1l~ty of . modern aircraft equipment. The procedural separation criteria are therefore reduced, UNDER RADAR ~0.NT~OL/SURVEILLANCE, without due regard to the l1m1tations of Radar, itself (Radar is a hlstorlcal control ~ pictur.e on the Radar screen is, per definition, delayed m true time, Whilst giving the impression of "instantanuity". Thus the Radar screen is most inadequate to detect immediate trends Whenever change in the True track occurs). The reduction in separation under Radar has therefore still to be in fact procedural; and the danger arises tha~ the "historical" Radar picture may be taken as "in real time" by the controller, for the sake of expedition! Also a distance "pad" needs to be provided for the, difficult 0

to define, time lag in the communication link between the controller and the pilot and the reaction time for the effective aircraft response. A hidden adverse factor here is the increased speed of flights and their reduced manoeuvrability. The present practice is rapidly approaching dangerous obsolescence.

Whether the replacing ATC method is a SYSTEM or a MESS will ultimately be decided by the "Powers that Be". IFALPA should be ready with a clear standpoint. Who knows, we may even get, eventually, what we believe is right. Think of North Atlantic lateral separation! (IFALPA Bulletin)

News from Member Associations Australia Some time ago, the Association sent a submission to the Department arguing that they should "take urgent action with the Public Service Board to have administrative arrangements made whereby air traffic controllers who fail to maintain the medical standards of Air Traffic Control and are thus declared unfit, should in all cases be given the opportunity of being superannuated out of the Public Service." The Board's response does not deny the Association's allegation that they have the legal power under Section 67 of the Public Service Act to retire an officer who becomes unfit to perform the duties of his office. However, in such circumstances the Board has the power to retire the officer or transfer him to another position, and the Board's view is that the latter course is the one to be pursued. One controller's case has brought the argument over the principle to a head. After consultation with the controller, the Association has advised the Department that he should be superannuated out of the Service. The consistent medical opinion is that he is clearly unfit for Air Traffic Control, but no doctors have been prepared to say that he is permanently unfit for all other duties. Thus this case has fallen fair .s~re within the principle for which the Association is fighting. In the meantime the Administrative and Clerical Officers Association has written to the Department stating vigorous opposition to the transfer of unfit air traffic controllers into

administrative/clerical positions. The President of that Association has accused the Public Service Board of intransigence and incompetence over the handling of this dispute by the Board. The case is one more argument for the introduction of a world-wide arrangement regarding retirement on medical grounds for controllers who become unfit.

Eurocontrol Guild The Guild has been much concerned of late about the future of Eurocontrol, and has informed the Federation of its disquiet regarding Eurocontrol's continued existence. The Agency has now issued a world-wide press release which categorically states that the continued functioning of Eurocontrol, after the present Convention expires in 1983, is assured. This was announced by the President of the Permanent Commission of Ministers (the Netherlands Minister of Transport, Water and Public Works) at the Commission's 46th Session, held in Maastricht recently. The President delivered a report on the factfinding mission he had undertaken among the Governments of the seven Member States with a view to settling the question of Eurocontrol's future activities and structure after 1983. His findings have shown that there is agreement between the Governments of the Member States on a new Convention for the period beyond 1983 and that it is the Member States' view that Eurocontrol must continue to exist beyond 1983 while the basis of a new Convention

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should be established well in advance of that time. The Member States are of the opinion that Eurocontrol's central tasks should be maintained and, if necessary, extended. This means that the Headquarters in Brussels, the Experimental Centre at Bretigny, the Training Institute at Luxembourg and the Route Charges Office in Brussels should continue to function within the framework of Eurocontrol under the joint responsibility of the Member States. The States which have already entrusted Eurocontrol's Maastricht Centre with Air Traffic Control responsibilities wish this Centre to be retained. Consultations are accordingly to take place between all the States concerned regarding the retention and further development of this Centre beyond 1983 for the benefit of the Benelux States and the Federal Republic of Germany. The Member States consider that the new Convention to enter into force in 1983 should be framed in such a way as to foster the accession of new Member States.

France In one of those splendid actions which other IFATCA Member Associations have taken in the past, APCA has donated a sum of money to both the German and Argentine Associations as a gesture of solidarity to help them overcome the problems with which these Associations are faced. In Germany, as well as in the Argentine, some controllers are still suspended or dismissed as a result of industrial action, and - in spite of the long interval - the situation in ATC in both countries has not yet returned to normal, with all the serious consequences this continued stalemate could have for aviation safety. The Federation is on record that it deplores the present situations.

United Kingdom GATCO decided some months ago to make an Award of the Hunt Trophy, its major Award to a person or group of individuals considered to have made the most outstanding contribution to ATC during the year. The Trophy was awarded to Edward Day, Vice-Chairman of GAPAN's (Guild of Air Pilots and Navigators) ATC Committee, a founder member of this and its associated General Aviation Committee. The Award was in recognition of Mr. Day's outstanding services to ATC generally, and to GATCO in particular, through voluntary effort, enthusiasm and a valued liaison on behalf of GAPAN with GATCO, stemming from his authorship of a 1971 paper containing a number of significant and fundamentally important proposals to rationalise and simplify the lower airspace in the London area. Mr. Day, a private pilot and managing director of a commercial firm, submitted his paper to the Civil Aviation Authority (CAA) for study by the Civil Aircraft Control Advisory Committee (CACAC). Changes were proposed to certain routes and to the status of the London area airspace and TMA in particular. The recommendations of CACAC stemming directly from those originally submitted by Mr. Day, generally were adopted, resulting in changes to the airspace status in the London area and to the route structure within. These changes were brought into effect during 1975.

The British Guild has also decided to award Honorary Membership to Group Capt. D.R.S. Bader of World War II fame. Douglas Bader surely does not need introduction to IFATCA members.

Publications Review A Survey Of Modern Air Traffic Control by Dr. Andre Benoit, published by the Advisory Group for Aerospace Research and Development, Brussels, Belgium; 760 pages in two Volumes (AGARDograph No. 209). These two splendid volumes contain a wealth of historical, technical and environmental Information, making them a "must" for all students of Air Traffic Control and those whose business brings them into contact with the profession and who wish to know more about A.T.C. The material is divided into five parts, covering respectively the general organisation of Air Traffic Control, Human Factors in A.T.C., the automation of control procedures, technical aids to Air Traffic Control and operational ATC systems. This must now constitute the most comprehensive available survey of Air Traffic Control ever published in the world. Seven pages are allocated to a brief outline of the history and activities of IFATCA making our Aims and Objectives available to all national and international organisations and Individual people who receive these books. Thirty-four papers are collected in the two volumes, covering the following main sections: (1) General Organisation; (2) Human Aspects; (3) Automation of Control Procedures (A = Principles and Applications of Automation; B = On-Board and Ground-based Collision Avoidance Systems; C = Flow Control Techniques; D = Aircraft Trajectory Predictions; E = Centerline Spacing); (4) Technical Aids to Air Traffic Control (A = Ground Based Navigation Aids; B = Self-Contained Navigation Aids; C = Landing Guidance Systems; D = Surveillance; E = Visualization; F = The Computer and Processing Facilities; G = The Satellite); (5) Operational ATC Systems. The two books contain Important material for many of IFATCA's Standing Committees for working purposes, and Chairmen of Standing Committees I and IV in particular should order the volumes in question. They clearly categorise themselves into basic documents regarding ATC and their Importance to the Federation are obvious. One article is written by our Contributing Editor (Human Factors), David Hopkin, on THE CONTROLLER VERSUS AUTOMATION, 15 pp, and extremely well presented.

The October 1975 IFATCA Circular gives details of the national distribution centres in a score of countries where the works may be obtained from, but readers of this journal may obtain the address of their nearest stockist from its Editor on request. GdB

The Controller's Social Life

The world of Air Traffic Control is an exclusive one and controllers constitute a "bloc" facing the outside world. This is the case when a threat is coming from outside against a group or an individual. The already existing spirit of solidarity and mutual confidence also prevail inside the social life of the group. ATC remains almost unknown to the public, and particular duty hours emphasize its particularism. In order to succeed In his task, a controller must be mentally serene and his private life must be devoid of any trouble which might beset his mind during work. Thus, his social life must also be a success and prevent him from taking refuge into his sole professional milieu. There must be a balance between control and society. (PATCO Journal)

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