IFATCA The Controller - April 1967

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IFATCA JOURNAL OF AIR TRAFFIC CONTROL

In this Issue Welcome to Geneva Data Exdiange iii MC

Recent DavalopmerdS in Collision Avoidanaa

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INew TELEFUNKEN precision approach radars improve landing safety Why? Range increased from 10 NM to 12 NM Indicator screens enlarged from 10 in . to 16 in .

Separate screens for 4 and 12 NM range Modernised a ntennas for control of approaches to diffe rent runways In consequence landing facilities a re greatly improved for poor visibility conditio ns In addition we supply : airways surveillance radars · terminal area radars · radar remoting systems · data processing systems · data transmission sys tems

ALLGEMEINE ELEKTRIC IT ATS-GESELL SCHAFT AEG-TELEFUNKEN Export Department 79 Ulm (Donau) Elisabethenstral3e 3 Germany

THE SHAINl{ING

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In l !J66 f'c rrant i insta lled a conqrntcr systc ni at the L onclun J\ii· T railie Control Cen tre, \ \ 'est Dra yton, \\' hie h \\'as dcsi"ncd to ta ke oYcr mam· of th\· routine " .

ATC tasks \\'h ich a rc lioth tedious a nd time consuming.

Kno\\'n as :\11 ::'\ I C!\ P the systn n helps n·linT s train a nd pressure on th\' contrnlln allo\\'i1w him m ore time r . .0 11 mak ing» ' '"' 1or c1ce1s1 At the hea rt of tilt' system the F C'rran ti / frmtrs computer h a ndles a ll asp<'cts of procedura l contrn l, includi ng takc-<;ff da ta, and au tomatica lly prnn·ssl's and prints o ut 01g ht p~·ogr~ss sti-i ps. Thc computer also produces a1~d lrans1;nts fli g ht prngrl'SS s tri ps ,·ia Fc 1Tan ti Data Link to C.rouncl :\ lon·1rn·nt Planning at I lea throw Ai rpon. ·

F er ran ti , the first com pn ny to apply a computer to :\ ir Traflic Control in the L'K - th c .ljm!lo comput c!· al Prcst\\'ick - a re respo nsible for three of the lour .\TC comp11tn systems installed. or abou t to b~ installed. in th is countn·. T he ,-en· latest 1s a R adai Simid;itorS,·,; tcm. dc,·cl«i ped ll\· Fe1.-ra11ti li1re,·a l11at ion or 11C\\' 1eci111iq11cs a11d trai11 i11g of' . \TC: ofTiccrs at I l 11m . \irport.

FERRANTI SYSTEMS FOR AIR TRAFFIC CONTRO L

Fur more i11fM111nlio11 011 Ferrn11ti's m1T1•11/ progress in Air .\ s ai~- t r~llic dcnsit iC's incrcasc Fe rran ti rc<'<H~nise the grOl\'ll l!{_ 1mpnrta11~'{' or l'Clcasi11!{ the C'<Hll rnllcr from Trn_ffer (i111tml, /1/ens1· ;1•rite lo co11 ,·c11t 1om~l n iut 11 1cs. c11alili11!{ him to ro11 cc111 ratc Fc-rrnn ti Ltd .. Di ~ita l Sys1cms Dc·parlmcnr, more nn 1~1~ .t ntc f'tm c· tion of sttpc1·, ·isi11g ,·it a l a11d \ Vcstern Road , Bracknell, Bcrkshin-. co1nplrx .\ 1 C. pron·d11rcs.

T e le ph one: Brnc kncll 3232 059

AIR TRAFFIC CONTROL DATA PROCESSING SYSTEMS now largely being realised in I

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SMR-124, Sign_aa l's high-sp~ed mi cro-min realtime general purpose computer incorporated 1n )'.Our ATC data processing system does not only mean that you will have at your disposal a highly modernyrocesso~. It also m~,af!s that you will have at your di sposa l Signaal _s ,,expe~1ence-p l us tn ATC-automation, ranging from pioneering days into tomorrows requirements.

Signaal's experience accompanies all elements of ATC systems, for example t~e micro_-min digital d i.splay sub-system for radar video, synthetic dynamic and electronic tabular data display.

S ignaal also produces primary and secondary radar video extractors.

Signaa l's system covers the entire range - hardware and soft ware and offers you the advantages of long experience too.

SIGNAAL radar, weapon control, data handling ~ .. a_n_~d_a1_r__ tr_a_ff._ic~c_o_n_u_o_l~s_ys_t_e_m_s_.~~~~~~~~~ N .V . HOLLANDSE SIGNAALAPPARATEN, HENGELO, THE NETHERLANDS

Marconi Touch-wire displays

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Displays based on the Marconi Tabul ar Display, w hich provides direct alpha-numeric read -out from a computer, but w ith the added facility of touch -wires for instant communication w ith the computer.

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Marconi High-definition displays

Displ ays giving the highest resolu t ion of any ava ilable.

Suitable for P.P.I, Height, Labelplan and Synthetic applications.

Marconi Bright displays Marconi Touch-wire displays provide fingertip access to a computer for instantaneous insertion and extraction of information.

Europe's largest manufacturer of air traffic control radar systems

Displays employing Direct View.

Storage Tubes for dayl ight viewing with full faci lities for Distan cefrom -Threshold, P.P.I or Height finding applications.

Th e Marconi Co mpany Limited, Radar Division, Marco ni House. Chelmsford, Essex, England

AN ' ENG LISH ELECTRIC ' COMPANY

LTD/SSS

Corporation Members of the International Federation of Air Traffic Controllers' Associations The Air Traffic Control Association, Washington D. C., U.S.A. Cessor Radar and Electronics Limited, Harlow, England The Decca Navigator Company Limited, London ELLIOTT Brothers (London) Limited Borehamwood, Herts., England IBM World Trade Europe Corporation, Paris, France ITT Europe Corporation, Brussels, Belgium Jeppesen & Co. GmbH, Frankfurt, Germany The Marconi Company Limited Radar Division Chelmsford, Essex, England N.V. Hollandse Signaalapparaten Hengelo, Netherlands

N.V. Philips Telecommunicatie lndustrie Hilversum, Holland The Plessey Company Limited Chessington, Surrey, England Selenia - lndustrie Elettroniche Associate S.p.A. Rome, Italy The Solartron Electronic Group, Ltd. Farnborough, Honts., England Telefunken AG, Ulm/Donau, Germany Texas Instruments Inc., Dallas 22, Texas, USA Whittaker Corporation, North Hollywood, California, USA

The International Federation of Air Traffic Controllers' Associations would like to invite all corporations, organizations, and institutions interested in and concerned with the maintenance and promotion of safety in air traffic to join their organization as Corporation Members.

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

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!he Marconi Myriad Computer is the most powerful tool available to Air Traffic Control today. ~ersatile - Myriad's sophisti cated interrupt facility and excepti onal high speed make 1t ideal for Fl ig ht Plan Processing or Radar Data Processi ng o r both simultaneously.

Economic- Myri ad rental scheme saves high capita l outlay and enables economic updating of equipment.

Sma ll size saves space.

Software Service - Complete programmes prepared - programme advice service - customers' program mers trained - programme library.

The new London Air Traffic Control Centre is to have a triplicated Marconi Myriad computer Flight Plan Processing system with instant access touch displays, which will make it the most advanced centre in the world.

Secar + Myriad Secondary Radar SystemCompletely automati c presentation o f 1dent1ty. height. pos1t1on and course of all aircraft to ranges of up t o 250 m iles. g1v1 ng max imu m effecti veness to secondary radar system.

Myriad Controlled AFTN Systems - Automatic message switching speeds transfer of vital information fo r a1 1 trnff1c control.

Marconi air traffic control systems The Marconi Company Limited. Radar Division. Chelmsford, Essex, England AN ' ENGLISH ELECTRIC' COMPANY

LTD/S5/

Technique of to-morrow?

Yes !

Available to-day from SRT! Automatic up-dat ing of flight plans on electronic Tabular Displays D Automatic Tracking 0 Symbol- and Alpha-numeric lndentification of all aircraft under contro l D D aylight D isplay on ordinary PPl's O Exact Electronic Maps stored on tape or in data memories D Conflict Search and Prediction D Flight plan Data

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Hand ling D Visible Transfer of control between adjace~t ~entres D Narrow-Band ra dar picture t r_ansm1ss 1on D . Sy~tem Concept taking any kin d of ATC Situati on into cons iderati on D Technique of tomorrow, ava ilable to-day from Standard Radio & Telefon AB, Barkarby, Sweden.

51C1ndard l?ctdlo & !el~fon AE

IFATCA JOURNAL OF AIR TRAFFIC CONTROL

THE CONTROLLER Frankfurt am Main, April 1967

Volume 6 路 No. 2

Publisher: International Federation of Air Traffic Controllers' Associations, 40 Park House Gardens, East Twickenham, Middlesex, England.

Officers of IFATCA: L. N. Tekstro, President; G. W. Monk, Executive Secretary; Maurice Cerf, First Vice President; Roger Sodet, Second Vice-President; Herbert Brandstetter, Hon. Secretary; Bernhard Ruthy, Treasurer; Wolter Endlich, Editor.

Editor: Woller H. Endlich, 3, rue Roosendoel, Bruxelles-Forest, Belgique Telephone: 456248 Production and Advertising Sales Office: W.Kramer&Co., 6 Frankfurt am Main NO 14, Bornheimer Landwehr 57a, Phone 434325, 492169, Postscheck Frankfurt (M) 11727.

Rote Card Nr. 2.

Printed by: W.Kramer&Co., 6 Frankfurt am Main NO 14, Bornheirncr Landwehr 570.

Subscription Rote: DM 8,- per annum (in Germany).

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).

CONTENTS

IFATCA Corporation Members

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Welcome to Geneva ....................................

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Address by the Swiss Minister of Transport, Communications, and Power, Mr. R. Gnagi ................ . ...... .

Address by the Director of the Geneva Airport Authority, Mr. G. Bratschi

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

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Air Traffic Control in Switzerland

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by Walter Tanner Contributions ore welcome as arc 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 in~ended meaning.

Written permission by the Editor is necessary for reprinting any part of this Journal.

Advertisers in this lssuo: Cossor/Ellioll Brothers (London) Ltd. (Inside Bock Cover); The Decca Navigator Company Ltd. (Back Cover); Ferranti Ltd. (l); Dr.-lng. Hell (12); The Marconi Company Ltd. (3, 5); Plessey Rodar Ltd. (24); N. V. Hollandse Signocdopporoten (2); SE LEN IA S.p.A. (29); Standard Elektrik Lorenz AG (13); Standard Radio & Telefon AB (6); Telefunken AG (Inside Cover)

Data Sources for Automated ATC Systems

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by Peter Reavely European Meeting "Semiconductor Research"

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Some Thoughts on Data Exchange

by J. S. Smit

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NADGE Defence Electronics System

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Inauguration of the Eurocontrol Experimental Centre

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Recent Developments in Collision Avoidance

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by Tirey K. Vickers

Dipl.-lng. Walter Watzek retired

by H. Brondstetter

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Picture Credit: ATCA of Greece (30); ATCA of Switzer lond (8, 9); Decca Navigator Co. Ltd. (15, 16, 17); Eurocon:rol (26. 27); Kucera & Vinck (30); Walter Ton11c1

Greek ATCA Press Conference

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(10, 11)

IFATCA Addresses and Officers

31 7

Address by the Swiss Minister of Transport, Communications, and Power, Mr. R. Gnagi

heureux de vous souhoiter un e cordio le b ie nvenue en Suisse et a Geneve et formul ent des voeux Ires sinceres pour un plein succes de votr e reu nion. lls esperent ego lement que vous conservercz le m eilleur souveni r de votre sejour dons noire pays.

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La convocation d 'une reunion onnue lle des membres de l' IFATCA me po r oit repo nd re a deux besoins importonts. Le prem ier, d 'ordre professionnel, vou s donne I' occasion de discuter des questions d'actuolite et d ' inter et mondiol pour lo secu rite o e rienne en gen era l. Le deuxiem e besoin est d 'etobl i r e t de mointenir le s con tacts p erson nels essent iels a un e profession dont l 'octivite es t internotionole e t ba see, pour une large port, sur une etroi te col laboration mutuel l e.

Vous ovez Messieurs l'in si gne ovontoge d 'apporte n ir a une profes:ion p locee' a l 'avont-gorde de la techniqu e et de ses developpem ents. Ce qui hier encore ne poraisso i t etre qu 'utop ie, ne l'es t deja plus oujourd 'h ui e t fera, demo i n de ja, porti e integrante de votre vie journaliere e t de VOS habit udes . Je pense ici avant tout a l'automation du contr6le de la circu lation aerienne et a l'utili sotion des sa tellites pour les com muni cations, lo n av igation, lo trans mi ss ion de donnees radar.

La complexite et !' importance de vos toches comme de vos responso bilites dons l'accomp l issement de votre tra va i l journo l ier n 'echoppent pas oux outorites competen tes .

Preuves en son t les efforts constants et les sommes con si derab les investies choque onnee pa r les Etots en vue de comp le ter, vo ire de reno uve ler les equipements de l ' infro st ru cture, afi n de vous donner les moyens e t les outils necessaires 6 !' exec ution de votre trava il. Ce travail, ignore peut-etre des non-ini ti es oux choses de l' oeronoutique, qui con siste a assurer, nuit et jour, la secur ite de vol a des milli ers d'oer onefs et po rtent ce ll e de m i llions de perso nn e l. Ce n'est d e ja p lu s un travai l mai s une miss ion.

Le Ch ef du dep artem ent fe de ra l d es Transports, des Commun ica tio ns e t d e l'Energi e e t ses co llob o rateurs sont

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Th e holding of on Annua l Conference of IFATCA members seems to me to fu lfi l two impo rtant functions. The first, profess ional, gives you the opportun ity to discuss current matter s of world interest in t he field o f safe ty in th e air. The second is the opportu nity to estab l ish and main tain those persona l contacts which ore essen tial in a profession w hich is internationa l in na ture and largely based o n close mutual cooperation.

You ha ve, gentlemen, the ou tstanding advantage of belonging to a profession which is in the forefront of technical developmen ts. That which, yester day, looked l ike Utopia, is a lready no longer so today, and tomorrow wi l l be an integral port of your daily li fe and practice. I am think ing, in partic ul ar, of automation o f air traffic con trol and of the use of satellites for commu ni ca t io ns, for navigation and for the relaying of radar data.

The comp lexi ty and importance of your tasks as wel l as your r esponsibi l ities in your everyday work is recognised by the competent aut horities . Thi s is show n in the constan t e ffort s and th e considerab le amoun t of money inves ted each year by the States to complete, even to re new, equipment in the infrastructure in order to provide the means and the tools necessary for you to carry out your work.

This work, unknown maybe to those outs ide the av iation field, provides sa f ety in fli ght, nig ht and day, to thousands of aircraft a nd mi l lions of peop le. This is no long er work but a mission.

Th e H ead of the Federa l Department o f Tronspo r t, Commun ica tions and Power and his staff a re happy to extend to you a worm welcome to Switzerland and to Geneva and their very sincere wish es for the success of your meeting . They hope that you w ill take away w ith you happy m emories of your stay in o ur co untry.

jours avec l'apparition d'oeronefs volant 6 des vitesses toujours plus grandes et qui deposseront bientot, celle du son, dons le damaine commercial. L'enorme copac ite des fu turs avions, a vec l a possibilite d 'emporter p lusieurs cen taines de passagers, ojoute encore l'ocuite du probleme.

Vos travoux, 6 Geneve, traiter ont, 6 n'en pas douter, de tous les aspects de ce dernier notamment du main tien du niveou eleve atteint pa r les services de contr o l e de lo circulation a eri enne. J'e n souhoi te d'heureuses conclusions.

Qu' il me so i t permis de remercier ici tous Jes contr6leurs en service ou ayan t p ris un repos bien merite, de lo Ires houte conscience profess ionne ll e opportee dons l'occomp lissement d 'un service souvent harossont et plein d 'embuches mois par celo meme d路une rare grandeur.

Bienvenue Geneve et pleine reuss i te 6 lo sixieme con fer ence annue ll e de votre federation.

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Address by the Director of the Geneva Airport Authority, Mr. G. Bratschi

lo f ederation internotionole des associa ti o ns de co ntroleurs du trofic oerien o d ecide de tenir so sixieme conference onnue lle dons noire ville. l e choix est flotteur et Geneve se re jouit d'occueilli r une organisatio n toucho nt de si pres au domoine d e l'oviotion, en genera l, et de lo securite de lo circulation oerienne, en port iculier.

En effet, berceou des oiles suisses lo cite du bout du lac o, de tout temps, marque un vif interet !'evolution de lo tech nique oeronoutique et oux tran sports par ovions.

Au cours de ces ving t dernieres onnees, les outorites genevoises on! ceuvre ovec une oudace et optiniotret e au d eve路 loppeme nt de l'aeroport d e Cointrin et de so n adaptation co nstante aux ex i gences d'un trafic aeri en moderne. L'on prochain un e no uvelle oerog ore, d' un e concepti on o ri ginol e en Europe, sero m ise en service et pourro trai l er un trofic de plusie urs mi l lions possogers o ttendus des 1970.

D 'outres projets son! encore sur l e metier dont certains consisten t 6 doter Geneve-Cointrin des ins tallations les mei lleures pour ass urer lo securite de lo circulation aerienne.

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Toutefois, une infrastructure oussi poussee soit-el le et repondont oux derniers perfectionnements d'une science et de techniques en continuelle expansion ne sourait donne les resu ltots ottendus si elle n'etoit pas desservie par une equipe non seu lement de specio l istes mais oussi de personnes devouees 6 un ideal, celui de l'oviation.

Yotre federation rassemble les enfan ts de cette famille dispersee sur tous les continents se lon le trace des reseaux oeriens locaux et interno tionnaux, mois tous unis dons la mem e pens ee d'ossurer la protection eff icace des usagers d es lignes a erienn es. Cette t6che n'est d e ja pa s faci le en soi, mais ell e se co mpli q ue encore serie use ment d e nos

The International Federa tion of Air Traffic Control lers' Associations has decided to hold its Sixth Annual Conference in our city.

Th e choice is flattering, and Geneva is very pleased to receive an organizat ion concerned in the field of aviation and air traffic contro l in particular. Indeed, the city o f Geneva, cradle o f Sw iss flying , ho s always shown the highest interest in t he evol ution o f ae ronautical techniques and air tra nsport. Duri ng the lost twen ty years, the Geneva authoriti es hove worked with ski ll and tenacity in the development of the ai r port of Cointrin, keeping it constantly adopted lo modern traffic r equirements. Next year, a new terminal building of original conception in Europe will be opened and will allow us to deal with an estimated traffic of many millions of passengers from 1970 onwa rds .

Other studies ore being carried out to give the Geneva a irport the best equ ipm ent for assuring the safety of air traffic.

However, the finest infrastructu re, answering the latest improvements of sience a nd techniques in con tinuous expansion, wou ld not give the hoped for results if it was not served by a teom, but of people devoted to an ideal aviation.

Your Federation groups together the members of a fa mil y wh ich is spread over all continents, following the lines of air traffic, local or intercontinental, but oil closely link ed in the some thought, that is effective protection of airline users. The task is not so easy in the first p lace, but gets more complicated in our days with the introduction of aircraft flying even faster and soon to r each supersonic speeds in the commerc ial field. The enormous capaci ty of future aircraft, able to carry many hundreds of passengers, adds more to the acuteness of the problem.

Your proceedings in Geneva will undoubtedly cover oil aspects of these problems, in particular, how to maintain the high level reached by the air traffic control services.

I hope they will arrive at a satisfactory co nclusion Please, let me take this opportunity to thank all controllers, on duty or on leave, taking a well earned rest, for the very high p rofessional conscien ti ousness brought to the accomplishment of a service , often exhausting and full of pitfalls, but, for these very reasons, of such importance.

Welcom e to Geneva and a happy outcome to Sixth Annual Conference of your Federation .

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Air Traffic

Control in Switzerland

by Walter Tanner Zurich ACC â&#x20AC;˘

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/j, INTERSSCTION

Organisation The organisation of the Swiss Air Traffic Services, the Rules of the Air, and the ATC operating procedures are generally in conformance with ICAO Standards and Recommended Practices, and such regional ICAO regulations which are affecting the EUM-MED .Region.

The airspace over Switzerland is subdivided into two Flight Information Regions and, above these, two Upper Information Regions: the Zurich and the Geneva FIRs/ UIRs. There is no upper limit of controlled airspace in

The range of these radars is, of course, affected by the surrounding mountains, depending on the relevant flight levels of the aircraft under control.

The Raytheon ARSR 1 radars, combined with a telecomputing 64-code SSR, are only used by the area control centres. The 1Ocm radar equipment is used by the approach control units, whilst the Marconi radars serve as stand-by equipment for APP and ACC, and at Zurich, the 264 is also used to control the outbound traffic.

Switzerland.

Control zones have been established at Bern, Geneva, and Zurich airports, including the appropriate approach

Some Traffic Figures

and landing aids.

At the Franco-Swiss airport Basle-Mulhouse, the operation of which is governed by a French-Swiss agreement, the air traffic control service is provided by French ATC units.

Various radars are available to aid in the control of traffic in the Geneve and Zurich FIRs/UIRs. These are at Geneva: Raytheon ARSR 1, 23 cm, range 200 NM, vertical cover. 50.000 ft Thomson-Houston, l 0 cm, range 60 NM, vertical cover. 40.000 ft Marconi 264 H, 50 cm, range 90 NM, vertical cover. 40.000 ft at Zurich: Raytheon ARSR 1, 23 cm, ronge 200 NM, vertical cover . SO.OOO ft Cossor ACR MK VI, 10 cm, range 60 NM, vertical cover . 25.000 ft Marconi 264 H, 50 cm , ronge 70 NM . vertical cover. 40.000 ft 10

As Switzerland is located in the centre of Western Europe, we are controlling, in addition to the in and out~ound traffic, overflying aircraft from nearly everywhere in Europe. They are coming from as far as North of 46° latitude, bound for the Mediterranean region, and vice versa. There is, of course, very heavy seasonal traffic to the Southern holiday resorts.

The following is a brief description of the activities of the various ATC units.

Bern Tower had 5.473 movements last June; it is occupied during daytime only. Four controllers are sharing the shifts.

At Geneva Tower, 23 Controllers have been responsible for 10.492 landings and take-offs in June 1966.

Zurich Tower, with 29 controllers, took care of 16.282 movements during the same time period.

Last Juli, Geneva Centre controlled 4.352 in and outbound, 8.543 overflying and 164 crossing aircraft. 27 controllers and 16 assistant controllers are operating 3, during slack traffic periods 2 vertically established sectors.

The following airways and upper airways are penetrating the Geneva TMA: UA 1 North, UA 24, UB/B 4, UA/ A 1, UR28, UG/GS, UA/A15, UG32, 816 Northwest, 816 Southeast, and UW 4.

In the Zurich TMA, UA/A 9 and UG/G 4 are crossing tracks; UG/G 5 is diverging to the Southwest, and G 31 to

the Northeast. To control the traffic on these routes, 34 controllers and 21 assistant controllers are operating 4 sectors, which have been established geographically. In the early afternoon, the fourth sector is operated as a radar departure sector. During periods of low traffic density, the four sectors may be merged into three or even two (during nighttime). In July 1966, Zurich AC C controlled 8.485 arrivals and departures and 6.053 overflying and crossing aircraft.

Local Problems Most of our problems result from the very small airspace available over Switzerland. As no airspace user is prepared to accept a restriction of his flying activity, it is very difficult to find a suitable compromise for accomodating all civil and military traffic, VFR and IFR flights, glider activity, etc.

The entire airspace has therefore been subdivided into civil airways, military VFR and IFR sectors, military supersonic routes, soaring and cloud flying zones for gliders, firing areas, and so on. There are even some glider areas within the Zurich CTR three of which are located 15 NM North, 8 NM West, ~nd South of Zurich airport. These areas have to be avoided by civil IFR traffic and do, of course, complicate the departure procedures.

Similarly, due to the small dimensions of our country, the short distances available for establishing procedural separation between aircraft before handing them over to an adjacent unit, have a considerable bearing on the complexity of our task and add to controllers' workload. The~e coordination problems can only be reduced when we will be able to affect radar handoffs with the adjacent centres.

In so far as military gun firing affects controlled airspace the traffic concerned is coordinated with the military e~ercise planners through the "Office of Coordination for Firing and Safety of Air Navigation", the Chief of which is a former ATCO. The A I p s, very attractive for tourists, are not so much appreciated by pilots and contr.ollers, unless t_hey are enjoying the mountains during holidays. At Z~ric~, the lowest usable flight level for southbound traffic 1s 150 (QNH value 1013-1031 mb), at least flight level 140 must be passed 30 NM South of the airport.

The lowest usable flight level from Geneva towards Milano is 180, piston engined aircraft have to pass FL 170 at least 35 NM East of the airport; turboprops and jets have their own company minima. In summertime, with its high seasonal traffic, it is often ~uite difficult to have enough flight levels available .which are accepta?le. to piston engined aircraft for cross1~g the Alps. By ass1~ning opposite direction flight levels, with t~e c~nsent of Milano ACC, or, if the weather permits, by 1ssueing ~MC on top clearances, enroute holding can mostly be avoided.

At Zurich we had the disadvantage of a different flight level system North of our FIR, as all aircraft a~ove FL 250 had to fly quadrantal leve!s in Germany. ~II aircraft c~n足 cerned had to change level within the Zurich TMA, w~1ch caused quite some difficulties as the northbound flight levels over Switzerland corresponded to ~he quadrantal levels for southbound traffic in the Federal Republic of Germany. The introduction of the semi-circular system hasn"t changed the picture significontly.

Coordination of Civil and Military Traffic As military VFR and IFR training flights may be conducted in the entire area outside controlled airspace, without any notification to the civil ATC units, the following procedures have been established for reducing the risk of collision between civil and military traffic: civil IFR flights, whether in visual or instrument meteorological conditions, shall in principle be conducted within controlled airspace only. Exceptions to this rule may be granted by the appropriate ACC, with the consent of the military air traffic services unit concerned.

Since, however, military aircraft must cross the airways A 9 and G 5 when flying from the western to the eastern part of Switzerland, and vice versa, a special coordination centre has been established. To facilitate coordination, G 5 has been divided into G 5 West (FRO-BER) and G 5 East (BER-ZUW), and airway A 9 into A 9 North (KLO-M)

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Graph of civil troff1c

11

ZETFAX

and A 9 South (M-CEN). On weekdays, from 0700 to 1100 and from 1230 to 1600 GMT, all known civi l traffic operati ng within these route segments has to be notified to the coordination centre by Geneva or Zurich ACC, respectively, ten minutes prio r to the time an aircraft is estima ted over the first reporting point.

At the coordination centr e t here are three civil controllers whose tas k it is to evaluate and process t he data forwarded by Zurich and Geneva ACC, and to display it in a suitable way to the military staff. This is done in the following manner: the informat ion o n t he civi l t raffic is received at the coo rdi na tion centre by on ass istant controller, who writes it down on a double-carbon-copy-strip, together with a number for each movement on A 9. Thi s strip is then passed on to the civil procedural cont roller, who plots the movement of the aircraft, includ ing callsign , flight level, and num ber, on a ba nd of tran spa r en t paper which is automat ically fed and ti me-synchron ized. One copy of the o riginal strip is then forwa rded to the civi l and one to the military rada r controller.

Five minutes pr ior to the time an aircraft i s est ima ted to overfly the first beacon w it hin this system, the p ro cedural controller blocks the relevan t flight level by man i pu lating o keyboard which controls an optica l disp lay in the military control room. The graph ical p resentation of the c ivil flight o n the transparent paper is transm i tted via closed circuit TV to the mi lita ry rad ar contro ll er in the coordination centre and to the mil itary contro l room.

The picture shows a ZETFAX transmitter with control unit and two ZETFAX receivers in the ATC tower of a large airport.

ZETFAX

equipment is used by airport authorities, ATC centres airlines, and meteorological services for the transmission of arrival and departure announcements to the fl ight controller flight plans to the control towe r airport weather cond itions to MET and AIS aircraft sea t reservat ions freight vo lume and weigh t cate ring requirement s for passengers technical servicing instructions airmail and parcel weights as well as all rapid ly chang ing requirements in everyday airline operations ZETFAX

wi ll also transmit via lines or radio links any other kind of written message - rapidly - securely - faultlessly Please write to us for detailed in for mation

(HELL)

DR.- ING . RUDOLF HELL GR ENZSTR . 1-5 Te lephone路 2011 -

12

Telex 路 292B5B -

Kl EL

GER MAN Y Cab les : HELLGERAETE

The civil procedura l cont roller and the c ivil radar controller are monitoring the flight progress of the civil tra f fic on the appropriate sector frequencies of Zu r ich ACC. As soon as th e procedural controller obtains information that the aircraft ha s vacated one section of the ai rway, he releases the rel evant flight level in that area. If no pos ition report is received , he r eleases the flight level three minutes after the tim e the a ircraft was est imated to c lea r t hat route segmen t.

The civil radar controller, working on a horizon tal p lo tting table in front of a ve rtical, scan converted rada r d isp la y, maintains survei llance of the civil t raffic on A 9. H is part icular task is to ident ify civil aircraft by r ela ting th ei r radar echoes lo the pos ition reports wh ich he can mon itor on the Zurich sector frequenc ies. On the p lotti ng table, he associates each identified aircraft with the num ber th at has been assigned lo it by the a ss istan t contro ller. The num bers on the plott i ng table are picked up by a TV camera, converted, and p resented together with the radar blips on the d isplays.

The mi litary radar controller is equipped with a scan co nverted r ada r disp lay and a TV tube showing the graph of the actual civil traffic situation. As ide of th e other duties, he issues cros sing clearances r egarding airway A 9 lo military ai rcraft and supp li es them with traffic information .

A mi l itary VFR controll er, sitting nex t to the civil procedural controller, issues crossing clearances and traffic information in r espect of G 5 East, based on t he gra ph ica l presentation of the civi l tra ffic and on th e levels occupied, as indicated on t he op ti cal di sp lay whi ch is operated by th e civi l procedural controller.

An addit ion al mi litary radar controller is working a t th e Geneva Cent er and issue s traffi c information in respect of G 5 W est to m ilitary traffic operating in the Geneva FIR. Owing to this system, it is an extremely rare o ccas io n that we have an a irmiss with a military aircraft.

P 358E • 367

... I

Navigation, Air Traffic Control, Space Electronics SE L radio navigation and landing aids are in serv ice all over the world. The wide program of the company inc ludes VHF Omnidirectional Ranges VOR, VO RTAC, VOR/D ME, TACAN equipment, NonDirectional Beacons NOB and, as latest development 1 the DVOR which features a course tolerance of on ly ± o.so. Further the l nstr~ment Landin~ .

System ILS including the Locali zer LK 22 which 1s capable of Cat. 11/11 1 performanc e. T_h ~ Radar Relay System FAB 6072 is us ed for transmitting radar pictures over great distances o n ~ar~ow-band . channels t o evaluation cent res. Within the national space p rogram, SE L part icipates in fu~damental electronic resea rch and in the production of . electronic eq uipment for the recoverable sounding

Please visit us at the 27 th Salon Internat iona l de l'Aeronautique at Le Bourget, ITT Stand, Hall B 2, Stand 2, from 26 May to 4 June 1967.

rocket, t he Ge rman communications satellite, and the German research satellite. The company's co~tribution to international programs extends to active p artic ipation in numerous project studies . and. manufacture of the hig hly specia lized electronic equipment. The company is equipped with the most modern p roduction facilities to meet the stringent requirements imposed by these projects.

A n~mber ~f positions are open to qualified . engineers inte rested in these activities. Please write to our Personnel Department.

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ITT 13

Data Sources for Automated ATC Systems

by Peter Reaveley Decca Navigator Comany Ltd .

At the forthcoming Sixth IFATCA Conference in Geneva, the topic und:r review during the Discussion Panel on 20th April will be "Data Exchang.e 路 The purpose of this article is to promote thought prior to and discussion during the Panel Session.

Introduction This paper discusses some of the problems likely to be encountered in the acquisition, processing and display of data in a computer-based ATC system. Many of the shortcomings in the accuracy and reliability of present data sources will be highlighted by their application to ATC computers; there is an adage in the computer industry "Garbage In, Garbage Out" (GIGO), which simply means that the output of a computer can be no better than the data input. Having reviewed the problems, a solution is proffered, utilizing radar - both primary and secondary - and air/ground data links, as separate and independent data sources having complementary characteristics.

Automated A TC Processes The a~tomated facilities currently planned for ATC systems will perform some or all of the following functions: flight plan processing, real time tracking computation on all targets (either from secondary, or primary and secondary radar data), conflict detection and resolution (from knowledge of aircraft intention, position, velocity and the separations required). They will also perform flow control and automatic hand-off functions, generate digital displays and provide human/computer interface units.These may be keyboards, rolling balls or touch display devices.

All computer-based ATC systems currently envisaged are aimed at assisting, rather than replacing, the human controllers ; and at all stages of development the controller is retained as the essential decision maker.

14

Data Inputs to the Computer Aircraft Intent An ATC computer must have knowledge of the intention and capabilities of all aircraft in the system. At the present time this may range from a full IFR_ flight plan fo~ General Air Traffic, to a brief statement of intent for Ope rational Air Traffic. The latter may be as simple as: callsign, type, endurance and "as cleared to Danger ~,re~ W78, then l hour air-to-air frring, as cleared to base 路 must be accepted, however, that a vague term such as "operational VFR'' is not acceptable as a flight plan to 0 computer .

Primary Radar Data Primary radar as an aircraft position input has the following advantages:

a) It can deal with non-cooperating aircraft. b) It is possible to design a powerful radar with a narrow beamwidth and short pulse length giving a well defined blip. Such a target enables the computer to discriminate between adjacent aircraft in high density areas.

Its disadvantages are: a) The echo strength is dependent upon the power of the radar, the distance between radar targets, the effec-

tive reflecting area (size and attitude of the aircraft) and the presence of ground and precipitation clutter. b) The lack of positive identification. c) The fixed data rate, depending upon the rotation rate. d) The severe practical problems of automatic tracking in high density areas as a consequence of a) to c) above.

Neither manually initiated nor manually rate aided tracking is acceptable for continuous operation with high density traffic.

Secondary Radar Data Secondary Surveillance Radar (SSR) can provide positive target tracking through all types of weather conditions, out to much greater ranges and somewhat lower elevation angles than is possible with primary radar "skin points". Also, the SSR target return is independent of aircraft size. From the ATC standpoint, the big functional advantage of SSR is that both the interrogations from the ground and the replies from the aircraft are coded. Consequently the aircraft can respond to requests for different kinds of information - identity or altitude, for example and different aircraft can be assigned different identity codes for positive target identification and selective display.

Extending the positive-tracking and target identification capabilities of the basic 64-code SSR, the 4096~code SSR, with automatic altitude reporting, and theoretically with discrete code allocation to each flight, will make a major contribution to an automated system. This ~ill normally become the main data input to an automatic trac~­ ing system. Problems will occur, however, because of basic system parameters of secondary radar: a) The data rate is dependent upon the turning rate of the primary radar when the SSR is co-located. b) SSR antennas have a wide beamwidth (over 3°) as there are several modes in each beamwidth (A, B, C). Wh~n ft are within one beamwidth of each other. in . two aircra . d. . azimuth, the computer will have difficulty in 1scr1m1nating between targets . c) Garbling, or mixing of the reply pulses f~om different · ft , 1s · an ·in herent SSR problem. It 1s caused by a1rcra

TYPICAL

+A A/C 'A' CODE 3000

Jl

+

two factors: the SSR ground station is not selective but interrogates all transponders within its beam; the transponder reply is a series of pulses which are strung out over a period of 20.3 microseconds (3.3 nms. in radar terms). When any two transponder-equipped aircraft are within 3.3 nms. of each other in slant range and are swept simultaneously by the same interrogation beam their reply trains will overlap within the decoder. Depending on the exact amount of overlap, garbling may produce: false target between normal targets, false emergency alarm (Fig. 1), cancellation of all, or part of, one or both targets, false data readouts of identity and/or altitude (Fig . 1), false identity responses when the ground decoder is set to display Identity (Bloomer) targets and when two aircraft ore within 4.0 nms. in slant range. d) The highly directional (beamed) ground antenna and strong aircraft replies of SSR can produce spurious targets by reflection from large flat surfaces, such as buildings, in the vicinity of the antenna. The receiver is unable to discriminate between the direct and reflected replies from the aircraft and will display both. The result is false targets which appear on the PPI and may even become garbled with other SSR targets. e) The allocation of a discrete code for the duration of each flight will present difficulties. In the 1970s there will be over 50,000 aircraft in the USA fitted with transponders and complex code allocation plans are being evolved so that no two aircraft are in the same area on the same code. One such plan involves the assignment of a block of codes to each Centre. A code would be allocated by the computer to each departure and passed to the aircraft by the controller. Under this system a long distance aircraft would experience several code changes, each one involving the computer, controller and pilot.

SSR is in many respects a far better data source than primary radar and its introduction should be accelerated, but it is not, due to its inherent system design, a fully dependable data-source. As traffic density increases, the problems will intensify to the extent that the computer may either cease to maintain tracking, or even worse, transpose

'GARBLING'

SITUATION

B

n n IL Jl n n n n

A/C 'B'

CODE 7100

A/C 'A' CODE 7700 (EMERGENCY) AS RECEIVED AND DECODED Figure 1

_Jl_ni----11

n_

n n n n.___.nl..--_n_ A/C 'B' CODE 7300

identites between tracks so that all subsequent computer routines are compromised.

Valid automatic tracking in high density areas is the basis of almost all subsequent computer routines and its reliability must be proven before acceptance into the ATC system. Although undoubted advantages will accrue from the growing use of 4096 code SSR, the shortcomings previously described will tend to limit the degree of confidence which can be placed upon its unsupported use as a source of tracking data.

An Air/Ground Digital Data Link Solution The data link gets away from the SSR's beamwidth, garbling, and reflection problems by using a non-directional interrogation, and by interrogating only one aircraft at a time. It can serve as a means of automatically reporting the position of an identified aircraft, by sending the position data obtained from the aircraft's navigation system back to the ground station, in the reply message. It can also send back the altitude data obtained from a barometric transducer in the aircraft.

As an independent source of flight data, the data link can serve to identify primary radar targets, und verify SSR identity and altitude data when garbling is suspected.

In this manner, complementary ground and air derived data inputs could be used to ensure the validity of the automatic tracking process and to enhance the reliability of the system as a whole. It would be in the best interests of the Aircraft Operators to fit the airborne data link if, by so cooperating with Air Traffic Control, the reliability and capacity of the control system could be increased and delays thereby reduced.

The success of such a method depends to some extent on the quality of navigational data. However, future requirements for greater navigational accuracy have. already been stated and equipment to meet them ex1~ts.

Eurocontrol have specified an operational track keeping capability of Âą 2 nms. with a 95% probability. This includes the combined tolerances of ground transmitters, radio propagation, aircraft receiver and computer, pilots pictorial display and autopilot coupling. The position fixing data to the airborne computer must therefore have a higher degree of accuracy, at least of the order of Âą l nm., ground level to 80,000 feet. Positional information of this quality, available in the aircraft, coupled with discrete identity, could be of considerable assistance in the automatic tracking process. The data link can further complement the primary and secondary radar by furnishing position and altitude data in airspace outside the coverage of the other two systems, or under conditions when such systems are inoperative. It would also help in the accurate ground referencing of long range radars and multiple mosaic radar inputs .

ATC System Operation Using Data Link The ATC computer will be looking through the flight plan and track store, building up track histories. As it does this it can also interrogate each aircraft by digital data link. The aircraft will individually reply with identity, flight level and position Flight level will be in the standard

16

ICAO height reporting code and position will be defined by the aircraft navigation system. This entirely automatic sequence of interrogation and reply takes approximately l /3rd of a second per aircraft on normal VHF frequencies.

A ground transmitter VHF aerial is omnidirectional and, as the computer interrogates aircraft individually by discrete address, it can change the rate and the sequence of interrogation of any aircraft depending upon its priority in the system. Direct access to this digital information will enable the computer to track automatically on both ground derived and air derived data. One frequency will give over 30 automatic position reports in l 0 seconds (over 200 a minute) and frequencies would thus be allocated on an "area", rather than an "airway" basis.

To solve code allocation problems, the computer could use aircraft registration as the address; this is on the flight plan, is discrete to each aircraft and is never changed in flight. It is feasible to define almost any aircraft registration in the world by the use of five alphanumeric characters, e. g. G-ALWH, 4X-YAE, 33296. The combination of 0 to 9 and A to Z provides 36 5 , i. e. more than 60 million possible aircraft addresses. The use of airframe registration also enables the computer to do a correlation from store on type of aircraft and a sense check on all its subsequent information. The computer may display to the controller on his PPI the flight number, mission number or R/T callsign. The controller is, however, not concerned with the precise method of communication between the computer and the aircraft. An automatic position-reporting data link, using airframe registration as address, will increase tracking validity without involving the pilot or controller in additional workload.

Controller/Pilot Automatic Communications It is generally accepted that, in a terminal or transition sector (20 to 120 miles from the principal airfield) an experienced controller can handle four to six aircraft under active control on the frequency at any one time, increasing to eight or nine aircraft during peak five minute periods. An accepted distribution of controller workload is 50% R/T, 50% liaison, with peak 5 minute periods of up to 70% R/T. However, simulation studies of 1970 ¡ 1972 traffic have shown that some sectors may have to handle 12 aircraft on the frequency at any one time, peaking to 15. The sheer volume of voice communications at this traffic level in the simulation saturated the R/T to the extent that some aircraft had to wait 2 1/2 minutes to initiate 0 message.

One possible solution, when the 25 kc/s frequency spacing becomes available is to increase the number of control frequencies, thus sharing the workload amongst more controllers. This implies a reduction in the size of the existing sectors with a corresponding increase in the number of controllers, thus aggravating the problem of inter-controller coordination. A more efficient solution would be the use of a digital data link to reduce the time each controller spends communicating. As an example the average voice ATC message and read-back takes 5 to l O seconds; when transmitted by digital data link it would take about 1/4 second.

Excluding position reports and flight level checks (which would be automatic), analysis of R/T message content has shown that a very high proportion of all R/T is composed

of standard messages, e. g. climb, descend, turn left, turn right, contact. It is noticeable that the busier the frequency the more standardised the R/T becomes. If all these standard messages could be sent automatically voice could be retained for the non-standard and emergency situations.

sage as the airborne unit will not accept the address of any other aircraft. Typical routine ATC messages as displayed to the pilot may be:

t

FL 150

DESCEND

t

FL 140

TURN RIGHT

-090

CLIMB When high validity automatic tracking becomes possible, computer assisted conflict prediction and conflict resolution will become practicable. The computer could generate instructions on the PPI as part of the target alphanumeric information block. The controller would have the responsibility of accepting or modifying these instructions.

The aircraft information block on the PPI could take the following form: GAL WH t 150 110

.._ identity .._ present level computer instruction --"climb to FL 150"

TURN LEFT

~270

CHANGE FREQUENCY

124.65

STANDARD ROUTEINGS

SR 322

OCEANIC CLEARANCES

c 350 82 (Oceanic clearances are given as Track Charlie, Flight Level 350, Mach. 82)

available on demand

i.

Flow Diagram of Future ATC System

With the present communications system the controller would transmit "GWH climb to Flight Level 150" verbally (if he could get a word in on the frequency!). However, the identity of the aircraft and the message to be sent, i. e. t FL 150, is already in the computer store. This could be sent automatically via the data link, on the approval of the controller, which he could signify by pressing a "send" button. A display would then show in the aircraft concerned: t FL 150 It is possible to display almost all standard routine ATC messages, with n 0 Ian g u age pro b I ems, using six in-line, symbolic, alpha-numeric indicators in the cockpit. There is no need for the pilot to copy the message since it will stay in view until a new instruction is transmitted. Only the aircraft addressed will display this mes-

The radar and data link interface between aircraft and computer, pilot and controller is shown in the flow diagram of a future ATC system (Fig. 2).

The left hand side of the diagram shows ground derived data (primary and secondary radar and flight plans), flowing into the computer. The right hand side of the diagram shows air derived data (identity, position and flight level) flowing into the computer via the air to ground data link. The central data processor correlates this information and generates digital displays for the controller. The controller can send, via the ground to air data link, digital messages to the aircraft; these messages could be generated by the ATC computer or by the control team. Voice communications could be retained for non-standard or emergency messages.

j~

.A

DECCA/HARCO

VOR/DME

_,;.:, -,4

DECTRA/LORAN

=~' ._J ,

FLIGHT LEVEL AIR DATA

'c'I I

· ~ ~' .,.-~INERTIAL /DOPPLER · . "'

VHF/UHF COMMUNICATIONS

ATC CENTRAL DATA PROCESSOR

o; ••

ffil HE

. .... . 111111

0 0

....

.... . .

111111 0 ••• GROUND DERIVED DATA

_)

. . .- ~t-i;:;-;~r~ _:.'

I I I I I

I 11 11 I

DIGITAL IDENTITY POSITION FLIGHT LEVEL

O• ••

AIR DERIVED DATA

PLAN POSITION DISPLAY

TABULAR DISPLAY

:1

VHF/UHF COMMUNICATIONS CONTROLLER

17

LANDLINE OR MICROWAVE LINK

OCEANIC CONTROL COMPUTER

Figure 3

PICTORIAL DISPLAY

TABULAR DISPLAY

Satellites

Conclusion

A digital data link would have an immediate and valuable application on the North Atlantic where radar coverage is not available. The data link, via a communications satellite, could provide aircraft position data on a continuous basis to the Oceanic Control Centres. If aircraft were carrying an accurate navigation system (probably a combination of Inertial or Doppler with Dectra or LoranC) then this positional information could be used by ATC, both for actual and relative position monitoring on the North Atlantic track structure. The Oceanic ATC computer could generate a digital PPI display to assist the reclearing of aircraft on the standard tracks and also ease the problem of clearing aircraft on routes which cross the organised track structure.

In a future computer-based ATC system the use of radar, both primary and secondary, together with an automatic position reporting data link, would greatly increase total system reliability. The two data sources . h are comp I ementary in c aracter and, being independent, temporary unserviceability or unreliability in any one input will n.o~ cause f.ailure of the ATC system. In summary, by exploiting an airborne capability to improve total system performance, the following benefits would be derived:

Mode of Operation The Oceanic control centre would send the aircraft callsign to the communications satellite which would relay this to the aircraft. The aircraft would transmit identity flight level and position back to the satellite for retransmission to the oceanic computer. It would be feasible for the computer to acquire over 50 aircraft position reports per minute. Thus, the oceanic computer could acquire accurate data at a high rate and would then be able to monitor safely much closer separation standards. The resultant higher utilisation of the airspace over the North Atlantic would be a most worthwhile system gain.

a) increased system reliability, b) increased system performance and hen

't I d ce capac1 y ea ing to both operational and economic benefits, ' c) a bonus, conferred by the data li'nk f d . . . o a great re uction 1n R/T loading and / hence , p 1 ' Io t/con t ro II er war k IOa d I

d) a continuous display for the Airline 0 f the . . f II . f . perators o . t d pos1t1on o a a1rcra t in which they are 1n ereste .

References 1. PARKER, B. D. (1967) :

D. . I CommunicaThe Design of on Air to Ground Asynchrono tion_s Sys.tern for A.T.C. l.E . E. Conference on Au_sT igito Engineering, London, March, 1967 _ .C. System Design & 2. GROVES, W. E. J. (1966) : Airborne Doto for A.T.C. Displays, U.K. Guild of ATC O . Conven路 路 路 路s tion, Bournemouth, October, 1966.

3. VICKERS, T. K. (1966) : Beaconry for Beginners, The A.0 .P.A. Pilot, October ,

Airline Operational Control The data link provides a further bonus to Airline Operators in _the ability to monitor aircraft replies to ATC interrogotions. The replies could be used to generate a display showing the position of the Company 's aircraft.

18

1966

_

): 4. FAA!C0t:-1MUNICAT~ONS SYSTEMS INC. ( 1965 t Future A1r/Ground/A1r Communication S l u )System lnvr.stigation . Repor No. CSl-66-TR-2144/1965 .

5. SULLIVAN, W. F. (1965) : Dato Transfer Experimenlation for (ONUS, FAA System Research and Development Service , NAFEC, Atlantic City , Report No. RD-65110/ Dec 1965.

Data Exchange

by F. J. Crewe El I iott-Automalion

The Controller and the Computer The term Data Exchange when applied to Air Traffic Control covers virtually every aspect of the controller's task. To attempt to cover such a wide field in an article of this nature would be foolhardy and at the best only scratch the surface of the problem. I have chosen therefore an area which permits a fairly broad approach, but nevertheless requires very careful examination in order to make the most effective use of the computer as a tool of the Air Traffic Control Officer. let us briefly look at what the controller requires of a computer or data processing system. a) First and foremost it must be reliable in terms of hardware and software. b) Secondly it must provide the right informati~n at th_e right time, for the right length of time, at the right position or positions and be easily readable. c) Thirdly it must be easy to communicate with.

Although I have listed ease of communication a~ being third this is the feature with which the controller is most clos:ly associated. This is the area which can cau_se th_e greatest amount of delay, error, discomfort, and fatigue 1f not properly designed and manufactured. .

Unless this area achieves the highest possible degree of effectiveness the real power in a data processing system is wasted. Obviously it is little point in h_avin~ a f~st and reliable system which provides good ra!1onal1sed information if it takes a laborious, time consuming key~oard sequence to change, amend, up-date, or call-down information. · · d What methods are available now, and what is require_ of future systems to ensure that thi~ port of the sy~tem 1s as good as the rest? Before attempting to answer this question (which will depend very much upon what sort of information is available and from what sources), we must first list some of the facilities we expect to find and what · t ·s sort o f equ1pmen 1 likely to be provided now. We should assume that a) the display sub-system has the capability of prov_iding Alpha-Numerics and symbols on the PPI and will be used in conjunction with one or more EDDs (the latter using touch-wire); b) Key b oar d s a re provided where .absolutely. necessary; . c) Rolling Ball/Joystick marker or light pen 1s available.

Having made such an assumption, we should continue to state that information is available from: Flight Plan/Estimates, Primary Radar, Secondary Radar.

It is not our concern for this purpose to worry whether the information is transmitted from another ATCC or is derived from the ATCC's facilities, what we are concerned with is how con we ensure that all unnecessary chores are eliminated from the controller's task.

For the purposes of communication with the computer, planning controllers and executive controllers need to be provided with similar facilities. Although certain planning functions may make more use of special function keys on a keyboard than those controllers carrying out executive roles, the simplest and quickest method of entering information into the computer must be provided. Today the use of the touch-wire Electronic Data Display goes a long way to meet such a requirement. Although it is flexible enough to permit a wide variety of information to be displayed and permits the amendment of any field, a sequence of operations still has to be performed by the operator. Todate, this is probably the quickest and most effective method of amending and calling-down information particularly when used in correlated form with the PPL Of course read-back of data about to be entered is provided so that the controller can see what form of "message" he has composed.

For the future, however, work is proceeding along "character recognition" and "voice recognition". There is a future for both these systems . The former however is expensive in terms of storage and in spite of reduced costs and smaller computers it is not yet viable for general application. Further, the greater use of standard format message keys used in conjunction with the Data Link to aircraft holds promise if adopted in wider fields.

In conclusion it is considered that the most effective use of modern computers should be made in Air Traffic Control to relieve the controller of as much tedious and time consuming work as possible. The system providing automatic initiation and tracking on primary and secondary radar, automatic conflict prediction for both planning and executive controllers, rationalised alpha-numeric data on the PPI which clearly indicates future conflicts will come about. It is not yet here but it is on the way; let us hope soon.

European Meeting "Semiconductor Device Research" A European meeting on "Semiconduct~r Device Researc h " w1·11 be held from l 6th to 22nd April, . 1967, at the ·11 · c Kerckhoff Institute, Bad Nauhe1m, . Germany.

W 1 1am .

The meeting is jointly sponsored by the Institute .of ~lectrical and Electronics Engineers, the Deutsche Phy~1kal1sche Gesellschaft, the Verband Deutscher Elektrotechn1ker, and the Nachrichtentechnische Gesellschaft, under the chairmanship of Prof. Dr. W. J. Kleen.

The following topics are on the agenda, and on each subject, several papers will be read: Effects using majority carriers;

Surface problems field-controlled devices; Piezo-electric sem'iconductor devices, including phonon interactions· Semiconduc~or problems in power electronics; Optoelectronic devices; Microwave generation and amplification; MIS and thin field effect transistors; Galvanomagnetic devices.

Further information on the meeting may be obtained from: Dr. K.-H. Riewe, 645 Hanau (FRG), Heraeusstr .12 ~~6 Telephone Hanou 24571

19

Some Thoughts on Data Exchange

by J. S. Smit N.V. Hollondse Signoolopporoten

The topic chosen by IFATCA for discussion on the last day of the Annual Conference is not an easy one. The subject "data exchange" may appear to be clear and well defined in scope, but further consideration reveals that it is very wide and affects air traffic control very deeply.

This paper is not meant to discuss all aspects of data exchange. It is merely meant to indicate some relative considerations in the hope that these may stimulate discussions at Geneva. The operational rather than the technical (engineering) aspects are considered, as this is thought to be appropriate for an IFATCA meeting.

Firstly, of course, in ATC there is the obvious division to be made between air-ground-air and ground-ground data exchange. Both are equally important, as ATC cannot work and cannot exist without either of these. Today, these types of data exchange take place by use of radio-communications and land-lines (telephone and telex). In addition, the internal intercom lines should not be forgotten. Dato exchange between various control positions within the same centre is a part of data exchange which must not be overlooked, for the communication between two sectors within the same centre does not differ greatly from the data exchange between two centres.

The present situation implies that the operational requirements for data exchange are specified in terms of radio channels or lines (with some differentiation as to whether the line must be hot or not so hot). As to content, format, coding and data rate (speed), the engineer will not ask difficult questions to the operational staff. The true situation, today, is that there is a "specification" for airground-oir message content (R/T phraseology), but for ground-ground messages there is, in many cases, nothing but a guidance, if anything at all. I agree that this portrays a situation worse than it really exists, as for operational application there are usually bi-lateral agreements which define in greater detail what information is to be exchanged at what time. Even so, these usually refer to the type of information to be exchanged rather than to its precise content, how it is formatted and, if applicable, how it is coded. The present "guidance" (as opposed to a specification) has so far proved to be adequate, as the exchange takes place between human beings, who are sufficiently intelligent and flexible to interpret the data when it varies in format or code .

A completely different situation arises when data exchange is to take place by use of "block boxes" between two computer-equipped centres, and even more difficult may be the situation in mixed environments when very detailed operational rules will be required for the programming of the computer. This is inevitable, because regardl~ss of the degree of flexibility which may be available rn a modern data processor, the modification of a data exchange program cannot as easily be effected as in a man-to-man link system. Therefore, it is most essential that the data exchange requirements for computer-tocornputer links be specified with the greatest of care in every possible detail to prevent any possibility of ambiguity. The computer in an automated centre plays the role :)f a centrnl information bank for the entire centre. With-

20

out excluding the possibility of verbal coordination, the intent of automation is that such coordination should be limited to extraordinary cases, for instance emergencies.

In other words, ATC must normally be able to work with the data available in the common store, i. e. the computer.

If it cannot, there is something wrong. Conversely the data available in the data store is - at least to a large extent - decisive for the working method of ATC. This data is very much associated with, and cannot even be considered separate from, the specifications for data exchange: it is the content of the initial data received which determines what can be done with it, and the data which has to be made avail~ble to the next centre defines at least part of the processing to be done while the flight is under control. . Lo.oking ~t the reality of ATC, an additional complication 1mmed1ately becomes obvious: a great number of centres e~ist, and will continue to exist for some time to come, which are not automated, whereas those which are automated .often have different degrees of sophistication or, al.ternot1v~ly, have automated different aspects of the total information processing. This means that we f d ore ace .h . d . wit a m1xe en~1ronment of data exchange between control centres - via AFTN only, via direct telepho 1· k 1· k b ne in s, . d ~n d via ata in s etw.een automated centres with varying degrees of automation.

One point , howeve r, ·1s c Iear: . . there 1~ a necessity for a more detailed specification of the operot1onal data exchange requirements.

Air Traffic Control has not always been in the h 't' h t d d 'C! appy post ion w ere. s an or spec111cations are available as and when required. At present, however, I believe th t 0 ·· ICAO established the ATC Autowe are ·in a goo d pos1t1on. mation Panel (ATCAP). already many years ago. Its task was to defin~ the requirements and specifications for data exchange. This was far from easy, but eventually_ ft th . a er a ... d f muc h crit1s1se ?ur report in 1964 - ATCAP produced in March 1966 its fifth report which, hopeful! ·11 b . t' II h y, w1 e accepte d interna 1ona y as t e firm basis for future work in this field .

ATCAP tried to include in one set of sp ·r. · h ec111cat1ons t e cases of data exchange between centres by use of AFTN messages as well as automatic data ex h b . c onge etween automated centres, applicable to the hum II . . . an as we as to the machine data link (with different de d f · man s or exacti. . tude), thus including a growth potential Th · d d f · e report contains a stan or set o messages suitabl f d · · I · ' e or a aptat1on to the part1cu or requirements and poss·b ·1·t · T . .

1 1 1 1es. o use an expression of American origin / ATCAP d d I pro uce a too . box. From this box, the standard tools t b h ·n . . mus e c osen 1 accordance with the 1ob to be done and the abilit to operate the tools.

Y . k · The situation as concerns air-grou d · d n -air ata 1in s 1s not as yet so. far . advanced. This is pa r tl y d ue to t h e f ac t that the engineering problem is far g t h h t'll . . ... rea er, a 1t oug s 1 within the capabilities of present day t h · dd' . . ec n1ques. 1n a 1tion, and this 1s perh~ps an even greater hurdle, there will be the need for more international ogre t F d emen s. or groun grou~d data _exchan~e, once the message content is standardised, neighbouring countries can link their computers by mutually agreed methods . It is of very little internatio-

nal importance whether, for instance, they use 600 or 1200 Baud links. However, for air-ground-air links only one technical solution is acceptable (or at least, although less attractive, compatible solutions). In other words, in addition to operational specifications, very detailed engineering specifications have to be agreed internationally. We are not ready for that yet ...

Finally, coming back to ground-ground data exchange, two important aspects are left:

1. data exchange between users of the same computer, 2. the possibility of continuously providing current traffic information to a third party, which could be a military unit which has to be kept informed of air traffic.

The first subject I have already touched upon. A computer in an ATC system is the central information bank. This implies two things, both of equal importance, as one cannot exist without the other. In an automated system, all flight data relevant to the level of automation, must be inserted into the computer. From here every control position concerned receives the appropriate information, either automatically or on request. In other words, the direct con-

troller-to-controller exchange of routine data is replaced by lwo-way controller-computer links. This is a change in working method, which requires a mental adaptation of the controllers and is an essential element to be kept in mind in the system design, in particular as related to the computer programming. When automatic displays are used, there is a choice between continuous display and onrequest display. The on-request display is a new element which computers offer, but it may require some time before this may be exploited to maximum advantage.

As regards the second subject, the provision of current traffic information, this was not dealt with by ATCAP. This panel was concerned with data exchange between centres for the purpose of eventual transfer of control. Possibly, these messages can, at least partly, also be used for the purpose of current traffic displays, but depending on what is to be achieved, a completely different approach might well be a better solution to this problem.

I realise that this paper leaves the reader with many loose ends. But it may contribute to a fruitful panel discussion at Geneva. If so, it has suited its purpose.

NA D GE Defence Electronics System HUCO, an international consortium led by Hughes Aircraft Company of the U.S.A., has been selected as the lowest bidder to construct the giant ÂŁ 100 million NATO Air Defence Ground Environment (NADGE) project. In addition to Hughes, the consortium consists of Compagnie Francoise Thomson-Houston of Paris, France; The Marconi Company Limited, Chelmsford, England; Selenia S.P.A., Rome, Italy; Hollandse Signaal Apparaten, Hengel?, Netherlands; and Telefunken AG, Ulm, Federal Republic of Germany.

The NADGE programme will be the biggest electronics project in Europe, and will produce for the NAT~ countries the most modern air defence system yet devised. It will also be the first project ever to be organized o~ balance of payments basis, a scheme whereby pa.rtic1pation by individual notions is shared on the baSIS of their contribution to the cost of the project.

In terms of knowledge and experience in the air defence, electronics and military systems fields, HUCO c~n­ stitutes the world's most important group of companies.

The selection has been made after two years of exhaustive

?

evaluation of the proposals.

The NADGE system, estimated to tak.e four to five years to complete, will provide NATO with o co~ple!e early warning and weapon control system, extending in depth from Norway to Turkey. Composed of radars, dot?handling and communications equipment, NADGE will be used to detect aircraft and to receive and process data that is passed on to NATO weapons installations and to fighter aircraft and missile batteries.

The nuclei of the NADGE system ore real-time gene.rolpurpose computers. The system takes advantage of h1ghspeed computers to provide display for command and control of air defence weapons.

Advanced data-display equipment serves the functions of data gathering (detecting, tracking, height-finding, target identification and target-size analyzing); and data

utilization (threat analyzing, weapons assigning, and weapons controlling).

Once a target is acquired by radar, the information is electronically transmitted by data link to the Command Centre where it first appears on a display console in the form of a target 'blip'.

At the same time, the information is transmitted to a video processor special electronic equipment which determines whether the ' blip' is an actual target, enemy jamming efforts, or simply video clutter.

The information is next transmitted to a correlator, or a computer memory unit, whose job is to record and remember a particular 'blip ' among other targets, remember whether it is a real target or clutter, and remember, as the 'blip ' moves - whether it is the same target or a new one.

From the correlator, the information is sent back to the ~rigi~al console in the form of digitized 'track symbo~ogy ¡ This symbology is superimposed over the raw video input, providing the operator with two means of tracking the target - the raw incoming video data and the track symbology from the computer.

The entire sequence of events must transpire within thousandths of a second. . Actual identification of the target may be accomplished ~n se~eral different ways, including voice identification, 1dent1fication through comparison of coded electronics or by computer-compared information about the target; or t~e Air Defence Commander may call upon interceptor aircraft for on-the-spot-visual identification.

Here, too, the system makes manual operations obsolete . For surface-to-air missiles, the precise location of an airborne target is transmitted immediately to the se lected missile site, or the air defence Comnwnder may electronically scramble, or launch, interceptor oircroft and, through any type of weather , guide them safely on their mission.

IV1 -1 L I "'

Inauguration of the ....,, Eurocontrol Experimental r

I

2

On 17th January 1967 Mr. Ray Mason M . P., Minister of Defence (Equipm ent) of the United Kingdom and President of the Permanent Commi ssion of M inisters of the European Organisat ion for the Safety of Air Navigation Eurocontrol and Mr. Edgord Pisani, French Minister of Equipm ent, inau gu rated the Eurocontrol Ex perimental C entre at Bretigny sur Orge near Paris, the first international air traffic control experimentation and evaluation establ ishment in Europe.

Mr. Roy Mason and Mr. Edgard Pi sani w ere assi sted

by Mr. Ren e Bulin, Director G eneral of the Eurocontrol Agency . Among st th e audience who we re given a demon stration of an a ir traffic control simulation exercise by th e per sonn el of the Experimental Centre, using its powerful air traffic simulator, w ere th e minister ial coll eag ues of Mr.

I

1 The Eurocontrol Experi mentol Centre ot Bretigny路sur-Orge.

2 Control ro om - Equipment loid ou t fo r inougu ro tion o f cen tre.

3 Pilafs room. 20 Plessey pilot" s consoles eoch oble to ha ndle up to 15 a i rcra f t.

4 High speed printer, Telefunken TR 4 computer ond contr o l d esk, Plessey moni tor disploy, punch cord unit.

5 Supervision posit ion - two rodor conso les, o ne pi lofs console.

3

I 22

I

5

Centre at Bretigny sur Orge, France

7

Ma son ond Mr. Pisani on the Eurocontrol Permanent Commission and other representatives of the seven Member Sta tes of Eurocontrol and of t he States which hove entered into co-operation agree ments with the Orga nisation, as well as representatives of other international organisations of European industry and of aviation.

The Experimental Centre 's air traffic control simulator is the first of its kind and i ts size in Europe. It was constructed ond in sta ll ed by a Consortium of European electron ic firms and is designed to make a major contribution to the common aim of the Eurocontrol Community of providing improved air tr affic services over Europe. A detailed repo rt on the tasks and activ ities of the Eurocontrol Experimental Centre will be pub lished in one of the next issues of THE CONTRO LLER .

- L

8

6

Contro l room -

7

loyo ut.

Plessey pilot's c o nsole , e lectronic to bulor disp loy ond keyboard ,

8

9

Bruss e ls Up per Areo Co n trol Cen tre simulo tion

w ith SAIT commu nications .

Syn t he tic traffic picture on Plessey radar d isplay showi ng repor ting points, aircra ft posi tions, 2 minute p red ictio n vecto rs , a b b re v iate d collsig ns, Oigh t leve ls .

Plesse y ho rizo nta l ra d ar d ispl a y show ing video mop, m ic ro to bulo r disp lay, c ontrols, and keybo ard.

9 6

23

Plessey AR -1, the m o st versatile surveillance radar P lessey AR-1 is a h igh d efinition , general pu rpose air surveillance radar designed to f ulfil all ai r-traffic co n t rol fun ctions w ith in a range of 75 miles. A ll t hese ope rat io na l roles are carried out accurately, r eliably and effectively: Ter minal area su rvei llance/ Approach control/ Radar seq uen cin g control I Parallel runway approach control / Outbou n d cont ro l from take-of! I GCA surveillance element / PPI approaches I Fig hter recovery I Low flying local traffic s urve illance.

The performance of the A R-1 in these man y roles has bee n stringently evaluated by civil and military au t horit ies resu lti ng

in over 50 equi pm ents being ado pted by a uth orities i n all parts o f th e wor ld. For f ull data o n th e AR-1 or info r matio n on the Plessey range of radars, displays and data h andli ng equi pment w rite t o:- Plessey Radar Lim it ed , Davis Road , Ch essin gton, Surrey, En g land. T el : 01- 3975222. T e lex: 262329

PLESSEY RADAR PLESS EY ELECTRO NICS G RO U P ''~PE(R)33A

24

Recent Developements in Collision Avoidance

by Tirey K.

V~ckers

Decca Navigator System, Inc.

Background The possibility of having mid-air collisions all began in Dayton, Ohio, one fateful day in 1904, when Orville Wright suddenly turned to his brother and said, "Wilbur, let's build another airplane" !

Thus, it was altogether fitting that Dayton should be the site of the National Air Meeting on Collision Avoidance, which was held February 23-24, 1967. Sponsored by the Institute of Navigation and the Flight Safety Foundation, the meeting provided a progress report on the entire field of ADSA (Air-Derived Separation Assurance). ADSA is a generic term which covers four different areas of effort:

1. Visual Capabilities (human factors for unaided visual detection),

2. P a s s i v e V i s u a I E n h a n c e m e n t (aircraft paint and lights), 3. V i s u a I A v o i d a n c e A i d s (pilot warning instruments - PWI), 4. N o n - V i s u a I A v o i d a n c e S y s t e m s (collision warning systems - CAS).

Following is a review of the developments which were reported in each area.

Visual Capabilities Douglas Aircraft psychologists have found that with special training, pilots at all experience levels can greatl_y improve their ability to detect other aircraft targets. This training is pointed toward two objectives: a) more efficient instrument scanning patterns, to give more time for looking outside the cockpit; . b) more systematic outside scanning techniques to increase the probability of target detection . . . .1s d one .1n a spe c'al 1 a·ircroft simulator. .

Th e training Pilots ore trained to read more and more instruments in~ · I scan, before looking · singe outs1·d e agat·n · When there 1s nothing outside to look at except a big blank em.pty sky, the Douglas-trained pilots start their target scannin_g pat. . · Th· allows their eyes is .. terns by looking first at a wing tip. . . b f ng the cond1t1on to refocus at infinity, there y preven i . h Id known as altitude (or empty-field) myo~i~, whic cou keep them from seeing an intruder until it got dangerously close. In scanning for targets, the pilots are encouraged to use swivel-neck techniques. · I d an increased accur. . · ..

Th e results o f t h 1s training rnc u e acy in instrument flying, as well as an increased ability to detect intruder targets. Follow-up tests made several months after completion of the training show that these increased proficiencies are retained .

Passive Visual Enhancement Paint FAA-sponsored studies of various aircraft color schemes show that fluorescent paint can increase aircraft conspicuity, but only when the aircraft gets close enough for the color to be detected (normally, about four miles away).

The tests also show that the all-important factor in longrange visual detection is the degree of contrast between the target and its background. Obviously, no single aircraft color can provide maximum contrast under all background conditions.

The final recommendation of this study was that the upper surfaces of the aircraft be painted a light highreflectance color, and the undersides a dark, low-reflectance color; to provide a visual cue as to flight direction, it was recommended that the entire tail be painted a solid fluorescent red or orange. However, the resulting visual improvement was not large enough to justify compulsory use of the recommended color scheme.

Lights Unquestionably, present types of rotating or flashing anti-collision lights greatly increase the visual detection range, compared to the standard red-green-white position lights. Unlike the latter however most of the anti-collision lignts provide no cue ~s to the ~spect of the aircraft being encountered (and consequently its direction of motion).

Perhaps someday the many different types of anti-collision lights presently in use may have to be standardized to provide this directional cue.

Altitude coding for aircraft lighting hos been tested as a possible means of providing a cue as to the relative altitude of other aircraft. One suggested flashing -code scheme is arranged in a cycle which repeats itself every 5000 feet, in the following order: Level

Code

5000 4000

3000 2000 1000 Initial tests indicated that the flashing code was more useful in showing altitude changes, rather than relative altitude, of other targets. Further modifications and tests are planned.

Aids to Visual Avoidance Several years ago, FAA researchers announced the pro · found discovery that a pilot has a much better chance of spotting a distant aircraft if he knows where to look . Fol

25

lowing this principle, NASA is studying the possible design of a Pilot Warning Indicator (PWI), to detect other aircraft by means of infra-red radiation, and then show the pilot where to look, in i"erms of relative bearing and elevation angle. However, the concept doesn't appear very promising. System capability will be handicapped by the fact that infra-red radiation fades out very rapidly in precipitation, clouds, or haze. In addition, the infra-red sensor probably will be useless whenever it is looking towards the sun.

3. The system must exchange altitude data between aircraft.

4. The preferred avoidance maneuvers will be short climbs or descents, rather than turns; the desired vertical separation or miss distance (at least at altitudes below 29,000 feet) will be 650 feet. This distance must be great enough to provide nominal separation under the worst conditions, yet small enough to keep any normal avoidance maneuver from triggering off a chain reaction with aircraft at other assigned altitude levels. Allowing for a possible altimeter error of ± 250 feet, the actual miss distance under the worst conditions would be 150 feet, minus the height of the aircraft. The 747 jumbojet (already nicknamed the "Boeing Hilton") will be about 60 feet tall, in level flight. This leaves a "guaranteed" safety margin of at least 90 feet!

Non-Vcsual Avoidance Systems Justification Higher aircraft closing speeds require correspondingly higher target detection ranges. As speeds increase, the point is reached where the relatively limited visual ranges available, in any visual or optical collision avoidance concept, cannot provide enough warning time in which to carry out the sequential functions of target detection, threat evaluation, maneuver selection and execution. This limitation is the reason behind

5. The CAS will be a Tau system. Tau (t) is the Greek letter which in CAS terminology stands for time-to-minimum-range. Tau ~ystems measure target range (R) and rate-of-closure (R) to determine this closure time, in accordance with the following equation: t = R/R. The desired Tau value is set into the CAS computer as a criterion for deciding whether or not any target is a threat. Fig. 1 shows the various combinations of target range and rate-of-closure which will trigger off a Tau alarm set for 40 seconds. However, when aircraft closure rates are very low, as shown in Fig. 2, an intruder could slip in dangerously close, without violating the Tau criterion. For this reason, the Tau alarm is supplemented by a range proximity warning. Fig. 3 shows the combined criteria for a typical Tau value of 40 seconds, and a range of 3 miles.

a) the implementation of positive control procedures by the ground-based ATC system; and b) the current development effort for an airborne electronic collision avoidance system {CAS).

Since 1955, the U.S. airlines have wanted a CAS. Ideally, they want it to provide an additional measure of protection against traffic not controlled by the ATC system, and to provide a last-ditch escape in cases of ATC system error.

CASorNAS?

6. The CAS will be a T/F system. T/F stands for Time/ Frequency, an exotic new principle which may prove to be the most revolutionary development since radar. Not only can it form the basis for CAS, but it hos the potential capability of taking over all functions which are presently carried out by SSR and DME. You will be hearing much more about T/F applications, in the years to come.

The airlines have stated carefully that they do not intend for CAS to be replacement or substitute for the ground-based A TC system. Also, they do not want their in1erest in CAS to be regarded as a signal to reduce efforts to improve lhe present A TC system, nor to predicate any new ATC system design on the possibility that some day airline aircraft might be equipped with CAS. System Characteristics The U.S. airlines are studying the possible characteristics for a CAS design which will meet their functional requirements. The characteristics and requirements are also being coordinated with those of other civil and military agencies, through a committee known as Collision Prevention Advisory Group (COPAG). Ideally, the ultimate gaol would be a common system design which would meet the requirements of air corrier, military and general aviation users, and thereby receive the widest possible implementation .

The committee:; are still a very long way from a common system design. As far as the airlines are concerned, however, several of the basic system characieristics are now firmly established:

1. The present stot .:: of the electrnnics ori dictates that the CAS will hav ~ to be a cooperative sysJ-em. As a result, only equipped oircraft wiil b8 able to participate; unequipped aircraft will not be detected by the system.

2. The CAS must opercite with in the frequency band of 1540 lo 1660 MHz, which has been allocated for this use . '.._() )'

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------------+- ------- ------T/F is based on the idea of carrying a very precise caesium or rubidium (atomic) clock in each airplane. These clocks are reset at suitable intervals to a master time signal, so that all clocks are synchronized with each other to an accuracy of 0.2 millionths of a second! This extremely precise common time reference permits the reservation of a definite time slot for each aircraft to transmit, while all others listen. This orderly procedure prevents garbling of transmissions from two or more aircraft. The reservation techn :que, called time-multiplexing, is diagrammed in Fig. 4.

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McDonnell Aircraft Corporation has already developed an operational T/F CAS for aircraft in their flight test area. It is expected that the proposed airline CAS wili utili ze many of the operating principles of the McDonnell system, as described below.

The output of the stable oscillator (the heart of the atomic clock) is multiplied to provide the UHF radio transmission frequency. At the beginning of its assigned time slot, an aircraft transmits a burst of UHF CW energy, followed immediately by the a i rcraft's encoded altitude data.

When this message is received by any other aircraft in the system, ihe range is measured by noting the time difference between the start of the time slot and the start of the CW transmission. The rate-of-closure is measured by noting the Doppler deviation from the standard CW frequency. The altitude data is decoded by the receiving aircraft, which then compares the intruder's altitude against its own altitude, as well as the altitude strata it expects to pass through within the Tau warning period. This screening procedure immediately eliminates from consideration

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27

a large percentage of the irrelevant targets. All other aircraft signals are examined to determine which of them imply threats, in terms of range and rate-of-closure. The entire process is repeated for each aircraft every two seconds.

When any R/R combination shows that the intruder hm reached either the Tau line or the minimum range line (see Fig. 4), the CAS computer triggers off an audio alarm in the pilot's earphones, examines the altitude situation, and lights an appropriate UP or DOWN arrow in the cockpit as a command for the avoidance maneuver. The light continues to flash until the threat is eliminated. The system logic is designed so that the intruder pilot will receive the opposite indication in his cockpit. The system can handle situations involving three aircraft; in this case the middle aircraft receives a "hold altitude" signal while one aircraft passes over and the other aircraft goes underneath.

The concept of having a pre-assigned time slot for each aircraft also forms the basis for an add-on system feature which someday could become a very useful aid for ATC. Known as station-keeping, this feature would enable a pilot to maintain a preassigned separation distance behind a designated aircraft ahead. The pilot would simply dial in the time-slot number of the aircraft which ATC told him to follow. The CAS equipment would provide a direct readout to show the distance from the designated aircraft, in miles. A rather simple left-right indicator could also be provided to show the relative direction of this aircraft.

With pilots able to space themselves, a long chain of similar-speed aircraft could be cleared along the same route with little more controller workload than that required for a single aircraft today. This technique could be especially useful in oceanic traffic control operations where no ATC radar coverage is available.

Economic Factors The one big catch in T/F technology is that it is still very expensive. The clock alone costs more than a number of small aircraft on the market today, and the complete

CAS will cost initially between 30 and 50 thousand dollars per aircraft. This will prohibit its adoption by most general aviation aircraft, and may severely restrict its adoption by the military.

Thus, the airlines must choose between a) the desire to obtain some protection immediately from other airline aircraft, with the proposed T/F system, or b) the desire to obtain, ultimately, protection from a much larger percentage of the entire aircraft population.

The latter objective can be met only by a much-lower-cost system. Technologically, however, such a system may be many years away.

Category of Aircraft Involved

Collisions

Air carrier versus air carrier Air carrier versus military Air carrier versus general aviation Total

6 8 20 34

Table 1

Midair Collisions -

U.S. Carriers 1938 through 1966

Table I shows that if it had been available, a CAS used only by airlines could not have prevented more than six midair collisions during the past 27 years. Does this record carry sufficient justification for the airlines to invest up to 100 million dollars in a CAS now, knowing that the equipment can provide no protection against 100,000 other U. aircraft that can't afford it?

s.

The stakes are getting higher. Airline aircraft arc getting larger and more expensive. A collision involving two fully-loaded SOO-passenger jumbojets over a metropolitan area could amount to a national disaster. As Mr. Lincoln Lee stated at the 1966 GA TCO Convention, "The enormous number of passengers on board will make imperative not only the provision of positive control but of fail-safe positive control" .. CAS may be that fail-safe backup, especially in high-altitude operations. We think the airlines will buy it.

IDopl. ~ng. Walter Watzek, Chief of the Austrian Federal Office of Civil Aviation retired On 31 st December 1966, Dipl. Ing. Walter Watzek retired from his post as Chief of the Austrian Federal Office of Civil Aviation (Bundesamt H.ir Zivilluftfahrt). Dipl. Ing. Watzek had been responsible for the development of the Air Traffic Services in Austria and thus, ultimately, for the safety of every airline passenger. Born in Vienna on 18th March, 1901, Watzek studied Technical Sciences at the Technical University of Vienna. After his graduation he joined the Siemens and Halske research laboratories in 1930. In 1934, he became a member of the civil aviation administration, and since then his main concern was aviation safety.

When the Auslrian Air Traffic Services were re-established after WW II, it was under his leadership that the "Bundesamt hir Zivilluftfahrt" developed from a nucleus of ien staff to the present Agency with its nearly 1OOO

28

employe:s, comprising air traffic controllers, engineers, communicators, as well as meteorological and administrative personnel. It might be a point of interest that about 10% of the total Agency staff are air traffic controllers.

Amo~g the numerous projects initiated and implemented by D1pl. Ing. Watzek are the establishment of full radar coverage throughout the country, the improvement of airport facilities, and the introduction of new navigational aids. The introduction of a new area control centre goes also to his credit, and he has been a promoter of automatic data processing in air traffic control.

The first. ~DP equipment will be installed during this year at the 101nt ACC/APP at Vienna. This will provide for the capability to show automatically alphanumeric information along with aircraft positions at controllers' radar displays.

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selenia air traffic control radars enhance air safety under all envir onmental conditions.

Italy , Norivay, Sueden, India, Rhodesia and Austria are all relying upon the Selenia L Band A TCR-2 long range radar and displaJ' equipment. The radar is available in single or dual channel versions, the latter uith optional frequency diversity. An extens.ive ~·ange ?f analog and digital displa~s. is also available. Where automation is possible the SELENIA - !DP Digital Displays are the best solution for present and future Air Traffic: Control needs.

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INDUSTRIE ELETTRONICHEASSOCIATE Sp A,

Rome - Italy P. 0. BOX 7083

The development of on optimum A TC system, capable of meeting a wide range of requirements posed by varying local conditions is by no means on easy task, porti· culorly in countries with a difficult topography, such as Austria. In planning such a system, any decision on how to utilise large amounts of the taxpayers' money to the best advantage, implies heavy responsibilities. Some people question heavy investments on aviation projects by claim· ing that the benefits of air travel ore only available to a fortunate few. Air transport, however, of which air traffic control is a v ital component, is a fu lly int egrated port of the economy of any modern country.

The role which a highly developed and efficien t air traffic services system ploys in ensuring the safety of air transport cannot be overestimated. All branches of the aviation community in Austria, commercial air transport, militory air traffic, as we ll as the private pilot depend upon and benefit from its services and facilities.

Th e fact that this system works wel l today, despite of the enormous growth of air traffic (t he annual rote of increase is more than 25% in Austria) is to a large degree due to the untiring efforts of Wolter Wotzek. Careful and timely planning and implementation of the ground facilities, thorough training of the air traffic control staff, the

Dipl. Ing. Watzek (centre) in discussion with same of his staff al Vienna Tower

provision of services to a 11 a irspace users, civil and mili tary, these ore some of the achievements of the long career of the popu lar and highly esteemed Chief of the A ustrian Air Traffic Services, whom many of the JFATCA Delgotes hod the pleasure of meeting on the occasion of the Vienna Conference.

H. Brandstetter

Greek Air Traffic Controllers' Association discusses Air Traffic Control Problems with Aviation Experts and with the Press

A meet ing and press conference was recently held by the Air Traffic Controllers ' Association of Greece at the Grand Bretogne Hotel, Athens.

Nick Gonos, President of the Greek Association, de· livered a paper " The Air Troffic Control System and the Ai~ T~o ffic Control ler". He emphasized the significance of aviation in a modern society and stressed the importance of 0 proper utilisation of the airspace for the benefit of oil users - the airlines military aircraft and General Aviation. ' '

general and technical press, and many oth Th d·. I · · ers. e au 1 ence active y port1c1poted in the quest.ton 0 d n answer session that followed Mr. Gonos ' speech , and th e w h o Ie even t . con be considered as a successful cont ·b t• t f · rt u ion o om 1liorising a greater number of people w ·th th · • • • 1 e OJms on d object ives of Arr Troff1c Control.

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Air~roft, crew, airports, navigation, meteorological in· f?rmation, etc., all these are vita l components of any ovia · ~ton environm ent, Gonos said, but it would be difficult to imagi ne 0 gre.a.ter number of aircraft, operating und er all weather cond1t1ons ' without the A.1r Tro ff"1c Serv1ces. · Referri.n g ta. I.CAO and sim ilar bodies, and reporting about the1.r ?ct1v1t1es, Gonos illustrated t he great import· ~nee that is rnterno~ionally attached to the effici ent opera· lion of the Arr Troff1c Services. He then presented a detailed descrip t ion of the A. T ff. . .

1r ro 1c ontrol Syste m rn Greece, w ith particular mention of the excellent air safety r ecord of that country. Specific a ttention was also devoted to th e human element in the system - t he pilot and the con · troller .

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.Th e meeting was attended by a great num ber of high off1c1o ls of the Greek aviation administration the Air Attaches of many States, the ai r l ines, represe nt~t ives of the

30

Pres. Nick Ganas (second from right) and other Officers of the Greek ATCA a l the press conference in the Grand Bretagne Hotel.

The International Federation of Air Traffic Controllers Associations Addresses and Officers AUSTRIA Verband Osterreichischer Flugverkehrsleiter A 1300, Wien Flughafen, Austria President First Vice-President Second Vice-President Secretary Deputy Secretary Treasurer

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

BELGIUM Belgian Guild of Air Traffic Controllers Airport Brussels National Zaventem 1, Belgium President Vice-President Vice-President Secretary Secretary General Treasurer Editor

A. Maziers R. Sadet M. van der Straate C. Scheers A. Davister H. Campsteyn J. Meulenbergs

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

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

Secretary Treasurer I FAT CA Representative Deputy

Heikki Nevaste Aimo Happonen Andre Remy Viljo Suhonen

FRANCE French Air Traffic Control Association Association Professionnelle de la Circulation Aerienne Northern Area Control Centre Paris Orly Airport France President First Vice-President Second Vice-President General Secretary Treasurer Deputy Secretary Deputy Treasurer

Francis Zammith J.M . Lefranc M. Pinon J. Lesueur J. Bocard R. Philipeau M. Imbert

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

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

DENMARK

GREECE

Danish Air Traffic Controllers Association Copenhagen Airport - Kastrup Denmark

Air Traffic Controllers Association of Greece Mersisis St. 8 Athen, N. Filadelfla, Greece

Chairman Vice-Chairman Secretary Treasurer

E. Larsen A. Frentz F. Fagerlund P. Breddam

President Vice-President General Secretary Treasurer

N. Gonos E. Petroulias E. Karagianides C. Theodoropoulus

FINLAND Association of Finnish Air Traffic Control Officers Suomen Lennonjohtajien Yhdistys r.y .

Air Traffic Control Helsinki Lento Finland Chairman Vice-Chairman

Fred. Lehto Veino Pitkonen

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

Valdimar Olafson K. Simonarson Einar Einarsson Guolaugur Kristinsson 31

IRE LAND

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

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

Secretary Treasurer

P. W. Pedersen A. Torres

SWEDEN

Swedish Air Traffic Controllers Association Luftva rtsverket Brom ma 10, Sweden Chairman Secretary Treasurer

E. Dahlstedt B. Hinnerson C. A. Starkman

ISRAEL

Air Traffic Controllers Association of Israel

Swiss Air Traffic Controllers Association

P. 0. B. 33

V. P. R.S.

Lod Airport, Israel Chairman Vice Chairman Treasurer

Jacob Wachtel W. Katz E. Medina

ITALY

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

Senator P. Caleffi C. Tuzzi L. Belluci

LUXEMBOURG

Luxembourg Guild of Air Traffic Controllers Luxembourg Airport President Secretary Treasurer

Alfred Feltes Andre Klein J.P. Kimmes

NETHERLANDS

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

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

NEW ZEALAND

Air Traffic Control Association Dept. of Civil Aviation, 8th Floor, Dept. Bldgs.

Stout Street Wellington, New Zealand President E. Meachen Hon. Secretary R. G. Roberts

Lufttraflkkledelsens Forening Box 135

Lysaker, Norway

32

Air Traffic Control Zurich-Kloten Airport Switzerland Chairman Secretary

J. D. Monin Walter Tanner

UNITED KINGDOM

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

L. S. Vass W. Rimmer E. Bradshaw

URUGUAY

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

U. Pallares

J. Beder M. Puchkoff

VENEZUELA

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

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

YUGOSLAVIA

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

NORWAY

Chairman Vice Chairman

SWITZERLAND

F. O!e K. Christiansen

President Secretary

I. Sirola A. Stefanovic

COS SOR

R-ELLIOTT INTO THE 70 's

The most fl exible SSA system available providing full ICAO faci lities w ith 4096 codes in all modes.

COSSOR ELECTRONICS LIMI TED. The Pinnacles. Elizabeth Way. Harlow, Essex . England Telephone : Harlow 26862 Telex : 81228

Active and Passive decoding available at all control positions

Maximum reliability 1s ensured by ca reful desig n and the use of advan ced techniqu es

Proven in operation

A l RSPACE CO NTROL DIV I S I ON Elliott Bros. (London) Ltd Borehamwood, Herts. England Telephone 01-953-2040 Telex 22777

The answer to increasing air traffic confusion is an accurate, comprehensive, automatic and reliable Nav/ATC syst em. Decca-Harco is the only system that can meet the navigation and A TC demands of both suband supersonic air t raffic. And only Decca-Harco can provide the fl exibility and acc uracy t hat p mit s close lateral separation of aircraft t hroughout the route structu re.

ON THE FLIGHT- DECK Decca O mnitrac-the world's most advanced lightweight digital computer-provides the pilot with undistorted pictorial presentat ion and automatic chart changing.

The 'ghost beacon' facility gives him bearing and distance to any point. Omnitrac al so rovides auto- pilot coupling and automatic altitude control which maintain spectively any required flight path and flight profile. The ET A meter indicates either time to destination or ETA.

AT THE CONTROL CENTRE Th e Decca Data Link provides the controller with accu rate displays of t he identity, alt itude and precise position of all co-operating . airc raft, usi ng th e com mon referen ce of a high acc uracy area coverage system. The use of speech is reduced and routin e.reports a~e el iminated by mean s of unambiguous, highspeed two-way si gnals.

It is on ly through an i ntegrated system, operating from a common reference, such as Decca-Harco, th at a great many ai rcraft of different types fl yin g at various s~eed s a.nd altitudes can be efficient ly co-ord inated mto a si ng le disci pl ined traffic pattern.

DECCA-HARCO The comprehensive Nav/ ATC system

The Decca Navigator Company Limited 路 London