IFATCA JOURNAL

OF AIR TRAFFIC CONTROL

D 20418 F

In this Issue

Welcome to Geneva

Data Exdiange iii MC

Recent DavalopmerdS in Collision Avoidanaa

Eul'OCOlllN1 - ........

NO . 2

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z Ill

:1111:

z ::a II. Ill ~

Ill

I-New 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 antennas for control of approaches to diffe rent runways In consequence landing facilities are greatly improved for poor visibility conditions

In addition we supply :

airways surveillance radars · terminal area radars · radar remoting systems · data processing systems · data transmission systems

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

THE SHAINl{ING Sl<V

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 ::'\ IC!\ P the systnn helps n·linT s train a nd pressure on th\' contrnlln allo\\'i1w him m ore time r 1 . . ' '"' 1or c ce1s10 11 mak ing»

At the heart of tilt' system the FC'rran ti / frmtrs computer ha ndles a ll asp<'cts of procedura l contrn l, including 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 flig 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. ·

.\ s ai~ - t r~llic dcnsit iC's incrcasc Ferran ti rc<'<H~nise the grOl\'ll l!{_ 1mpnrta11~'{' or l'Clcasi 11!{ the C'<Hll rnllcr from co11 ,·c11t 1om~l n iut 11 1cs. c11alili11!{ him to ro11cc111 ratc more nn 1 ~1~ .t ntc f'tm c· tion of sttpc1·, ·isi11g ,·ita l a11d co1nplrx .\ 1 C. pron·d11rcs.

Ferran ti , the first com pnny to apply a computer to :\ ir Traflic Control in the L'K - thc .ljm!lo computc!· al Prcst\\'ick - a re respo nsible for three of the lour .\TC comp11tn systems installed. or about 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 Trn_ffer (i111tml, /1/ens1· ;1•rite lo Fc-rrnnti Ltd .. Di~ita l Sys1cms Dc·parlmcnr, \ Vcstern Road , Bracknell, Bcrkshin-.

T elephone: Brnckncll 3232

in Air

059

AIR TRAFFIC CONTROL DATA PROCESSING SYSTEMS

now largely being realised in

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SMR-124, Sign_aa l's high-sp~ed micro-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 disposa 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 software -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

1 a

Marconi Touch-wire displays provide finger­

tip access to a computer for instantaneous

insertion and extraction of information.

Europe's largest manufacturer of air traffic control radar systems The Marconi Company Limited, Radar Division, Marconi House. Chelmsford, Essex, England

AN ' ENGLISH ELECTRIC ' COMPANY LTD/SSS

Marconi Touch-wire displays

Displays based on the Marconi Tabular 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.

Marconi High-definition displays

Displays giving the highest resolut ion of any ava ilable. Suitable for P.P.I, Height, Label­plan and Synthetic applications.

Marconi Bright displays

Displays employing Direct View. Storage Tubes for dayl ight viewing with full faci l ities for Distance­from -Threshold, P.P.I or Height ­finding applications.

4

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.

!he Marconi Myriad Computer is the most powerful tool avail­able to Air Traffic Control today.

~ersatile - Myriad's sophisticated interrupt facility and excepti onal high speed make 1t ideal for Fl ight Plan Processing or Radar Data Processing or both simultaneously. Economic- Myriad rental scheme saves high capita l outlay and enables economic updating of equipment. Small size saves space.

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

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 automatic presentation o f 1dent1ty. height. pos1t1on and course of all aircraft to ranges of up to 250 miles. g1v1ng max imum effectiveness to secondary radar system.

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

Marconi air traffic control systems The Marconi Company Limited. Radar Division. Chelmsford, Essex, England

AN 'ENGLISH ELECTRIC' COMPANY LTD/S5/

6

Technique of to-morrow? Yes ! Available to-day from SRT!

Automatic up-dat ing of flight plans on elec- Handling D Visible Transfer of control between tronic Tabular Displays D Automatic Tracking adjace~t ~entres D Narrow-Band ra dar picture 0 Symbol- and Alpha-numeric lndentification t r_ansm1ss1on D . Sy~tem Concept taking any of all aircraft under contro l D D aylight D isplay kind of ATC Situati on into cons iderati on D on ordinary PPl's O Exact Electronic Maps Technique of tomorrow, ava ilable to-day from stored on tape or in data memories D Conflict Standard Radio & Telefon AB, Barkarby, Search and Prediction D Flight plan Data Sweden.

ITT 51C1ndard l?ctdlo & !el~fon AE

IFATCA JOURNAL OF AIR TRAFFIC CONTROL

THE CONTROLLER Frankfurt am Main, April 1967 Volume 6 · 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).

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

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)

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 (10, 11)

CONTENTS

IFATCA Corporation Members

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

Address by the Swiss Minister of Transport, Communica-

tions, and Power, Mr. R. Gnagi ................ . ...... .

Address by the Director of the Geneva Airport Authority,

Mr. G. Bratschi ..................................... .

Air Traffic Control in Switzerland

by Walter Tanner

Data Sources for Automated ATC Systems

by Peter Reavely

European Meeting "Semiconductor Research"

Some Thoughts on Data Exchange

by J. S. Smit

NADGE Defence Electronics System

Inauguration of the Eurocontrol Experimental Centre

Recent Developments in Collision Avoidance

by Tirey K. Vickers

Dipl.-lng. Walter Watzek retired

by H. Brondstetter

Greek ATCA Press Conference

IFATCA Addresses and Officers

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10

14

19

20

21

22

25

28

30

31

7

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

La convocation d 'une reunion onnuelle des membres de l' IFATCA me poroit repondre a deux besoins impor­tonts. Le prem ier, d 'ordre professionnel, vous donne I' occa­sion de discuter des questions d'actuolite et d ' inter et mon­diol pour lo secu rite o e rienne en genera l. Le deuxieme besoin est d 'etobl i r et de mointenir les con tacts person ­nels essent iels a une profession dont l 'octivite es t inter­notionole et basee, pour une large port, sur une etroi te

col laboration mutuel le. Vous ovez Messieurs l'in si gne ovontoge d 'apporten ir

a une profes:ion p locee' a l 'avont-gorde de la technique et de ses developpements. Ce qui hier encore ne poraissoi t etre qu 'utop ie, ne l'es t deja plus oujourd 'h ui et fera, de­mo in de ja, portie integrante de votre vie journaliere et de VOS habitudes . Je pense ici avant tout a l'automation du contr6le de la circu lation aerienne et a l'utilisotion des sa tellites pour les communi cations, lo navigation, lo trans­

miss ion de donnees radar. La complexite et !' importance de vos toches comme de

vos responsobilites dons l'accompl 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 consi ­derab les investies choque onnee pa r les Etots en vue de completer, vo ire de renouve ler les equipements de l ' infro ­st ructure, afin de vous donner les moyens et les outils necessaires 6 !'execution de votre trava il. Ce travail, igno­re peut-etre des non-ini ti es oux choses de l'oeronoutique, qui consiste a assurer, nuit et jour, la secur ite de vol a des milliers d'oer onefs et po rtent ce lle de mi llions de per­sonne l. Ce n'est d e ja p lus un travai l mai s une miss ion.

Le Ch ef du departement fede ra l d es Transports, des Commun ica tio ns et d e l'Energie et ses co llobo rateurs sont

8

heureux de vous souhoiter un e cordio le b ienvenue en Suisse et a Geneve et formulent des voeux Ires sinceres pour un plein succes de votr e reunion. lls esperent ego le­ment que vous conservercz le meilleur souveni r de votre sejour dons noire pays.

* The holding of on Annual Conference of IFATCA mem-bers seems to me to fu lfi l two impo rtant functions. The first, professional, gives you the opportun ity to discuss cur­rent matter s of world interest in the field o f safe ty in the air. The second is the opportunity to establ ish and main­tain those personal contacts which ore essential in a pro­fession w hich is internationa l in na ture and largely based on close mutual cooperation.

You have, gentlemen, the ou tstanding advantage of belonging to a profession which is in the forefront of

technical developments. That which, yesterday, 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 particul ar, of automation o f air traffic control and of the use of satellites for commu nica t io ns, for navi­gation and for the relaying of radar data.

The complexi ty and importance of your tasks as wel l as your r esponsibi l ities in your everyday work is recognised by the competent authorities. This is shown in the constan t effort s and th e considerab le amount of money inves ted each year by the States to complete, even to renew, 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 aviation field, provides sa fety in fli ght, n ig ht and day, to thousands of aircraft a nd mi l lions of people. This is no longer work but a mission.

The Head of the Federa l Department o f T ronsport, 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 wishes for the success of your meeting . They hope that you w ill take away w ith you happy memories of your stay in o ur country.

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

lo federation internotionole des associa tions de con­troleurs du trofic oerien o decide de tenir so sixieme con­ference onnue lle dons noire ville.

l e choix est flotteur et Geneve se re jouit d'occueilli r une organisation touchont 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 a !'evolution de lo technique oeronoutique et oux transports par ovions. Au cours de ces ving t dernieres onnees, les outorites gene­voises on! ceuvre ovec une oudace et optiniotrete au deve· loppement de l'aeroport de Cointrin et de so n adaptation constante aux exigences d'un trafic aeri en moderne. L'on

prochain une no uvelle oerogore, d'une conception o rigi­nole en Europe, sero mise en service et pourro trai l er un trofic de plusieurs mi l lions possogers o ttendus des 1970.

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

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 resultots 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 enfants de cette famille dispersee sur tous les continents selon le trace des reseaux oeriens locaux et internotionnaux, mois tous unis dons la mem e pensee d'ossurer la protection eff icace des usagers des l ignes aerienn es. Cette t6che n'est deja pas faci le en soi, mais elle se compliq ue encore serie usement de nos

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 copacite des fu turs avions, avec la possibilite d 'emporter p lusieurs cen­taines de passagers, ojoute encore a l'ocuite du probleme.

Vos travoux, 6 Geneve, traiteront, 6 n'en pas douter, de tous les aspects de ce dernier notamment du maintien du niveou eleve atteint pa r les services de contro le de lo circulation aerienne. J'en souhoi te d'heureuses conclusions.

Qu' il me soi t permis de remercier ici tous Jes contr6-leurs en service ou ayant p ris un repos bien merite, de lo Ires houte conscience profess ionnell e opportee dons l'oc­complissement d 'un service souvent harossont et plein d 'embuches mois par celo meme d·une rare grandeur.

Bienvenue a Geneve et pleine reuss i te 6 lo sixieme con­ference annuelle de votre federation.

*

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

The 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 the evol ution o f aeronautical techniques and air transport. Duri ng the lost twen ty years, the Geneva authoriti es hove worked with ski ll and tenacity in the deve­lopment of the airport of Cointrin, keeping it constantly adopted lo modern traffic requirements. 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 onwards.

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

However, the finest infrastructure, answering the latest improvements of sience and techniques in con tinuous ex­pansion, would 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 family wh ich is spread over all continents, following the lines of air traffic, local or intercontinental, but oil closely linked 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 reach 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 conclusion

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 tiousness brought to the accomplishment of a service, often exhausting and full of pitfalls, but, for these very reasons, of such importance.

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

9

Air Traffic Control in Switzerland

by Walter Tanner Zurich ACC

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

Switzerland. Control zones have been established at Bern, Geneva,

and Zurich airports, including the appropriate approach

and landing aids. At the Franco-Swiss airport Basle-Mulhouse, the opera-

tion 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

• VOR 0 NOB /j, INTERSSCTION

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 1 Ocm 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.

Some Traffic Figures

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~n­cerned 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)

:I: I­::> Oc (/) z

I :::> O'> 0 ~m :I: :I: I- l­a: a:

M-;--------lf-

~ ~ KLO-r-----1'----

TRA/ZUE-+-------"'----~--'--------1 :I: l­a: Oc Zz

I :::::> O> 0 ~m :I: :I: I- I­::> :::> oo

M-r-----~

U> U> CEN FRO-+-----L--i...-------4---r---~

t­en w 3: ~

I :::> LO 0 <.? m I- I­(/) (/) <( <( UJ UJ

I-­en <( c wz '::>

LO 0 '?m I- 1-(/) (/) UJ w ;t ~

WIL ZUW+-~=----t---L----r-t-----71

WIL-1-~~~-1--~+---t---:r--~-i

BER

FRO -+--~---+-----+------t 0930 0920 0910 0900

Graph of civil troff1c

11

ZETFAX

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

ZETFAX

arrival and departure announcements to the fl ight controller flight plans to the control tower airport weather cond itions to MET and AIS aircraft seat reservat ions freight vo lume and weight cate ring requirements for passengers technical servicing instructions airmail and parcel weights as well as all rapid ly chang ing require­ments in everyday airline operations

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 formation

(HELL)

DR.- ING. RUDOLF HELL Kl EL GR ENZSTR . 1-5 GER MANY

Telephone· 2011 - Telex · 292B5B - Cables : HELLGERAETE

12

and A 9 South (M-CEN). On weekdays, from 0700 to 1100 and from 1230 to 1600 GMT, all known civi l traffic operat­ing 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 centre there are three civil con­trollers whose task it is to evaluate and process the 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 on the civi l t raffic is received at the coo rdination 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 controller, who plots the movement of the aircraft, includ ing callsign , flight level, and num ber, on a band of transparent paper which is automatically fed and time-synchron ized. One copy of the original strip is then forwarded to the civi l and one to the military radar controller.

Five minutes prior to the time an aircraft is est imated to overfly the first beacon w it hin this system, the p ro ce­dural controller blocks the relevan t flight level by man i­pulating o keyboard which controls an optica l disp lay in the military control room. The graph ical p resentation of the c ivil flight on the transparent paper is transmi tted via closed circuit TV to the mi lita ry radar contro ll er in the coordination centre and to the mil itary contro l room.

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 the procedural controller obtains information that the aircraft has 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 time the a ircraft was est imated to c lea r that route segment.

The civil radar controller, working on a horizon tal p lo t­ting table in front of a ve rtical, scan converted radar d is­p lay, maintains survei llance of the civil t raffic on A 9. H is part icular task is to ident ify civil aircraft by rela ting th eir radar echoes lo the pos ition reports wh ich he can mon itor on the Zurich sector frequenc ies. On the p lotting table, he associates each identified aircraft with the number th at has been assigned lo it by the a ss istan t controller. The num bers on the plott ing 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 converted rada 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 crossing clearances regarding airway A 9 lo military aircraft and suppli es them with traffic informa­tion .

A mi l itary VFR controller, sitting nex t to the civil proce­dural controller, issues crossing clearances and traffic in­formation in r espect of G 5 East, based on the graph ica l presentation of the civi l tra ffic and on the levels occupied, as indicated on the optical disp lay whi ch is operated by the civi l procedural controller.

An addit ional mi litary radar controller is working a t the Geneva Center and issues 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, VORTAC, VOR/D ME, TACAN equipment, Non­Directional Beacons NOB and, as latest develop­ment the DVOR which features a course tolerance of on

1

ly ± o.so. Further the l nstr~ment Landin~ . System ILS including the Localizer LK 22 which 1s capable of Cat. 11/11 1 performance. T_h~ Radar Relay System FAB 6072 is used for transmitting radar pictures over great distances on ~ar~ow-band . channels t o evaluation cent res. Within the national space p rogram, SE L part icipates in fu~damental electronic research and in the production of . electronic equipment for the recoverable sounding

rocket, t he German communications satellite, and the German research satellite. The company's co~tribution to international programs extends to active partic ipation in numerous project studies . and. manufacture of the highly specialized 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. Standard Elektrik Lorenz AG Transmission and Navigation Division 42 Hellmuth-Hirth-Strasse 7 Stuttgart-Zuffenhausen, Germany

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. Stoodocd Elektclk loce0< AG · St"ltg•rt . Gecmooy 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 · 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 · 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 t . ft are within one beamwidth of each other in wo aircra . d. . . azimuth, the computer will have difficulty in 1scr1m1-

nating between targets .

c) Garbling, or mixing of the reply pulses f~om different · ft · · herent SSR problem. It 1s caused by a1rcra , 1s an in

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

TYPICAL 'GARBLING' SITUATION

A/C 'A'

CODE 3000

AS RECEIVED AND DECODED

Figure 1

+A + B

Jl n n IL A/C 'B' Jl n n n n n_ CODE 7100

A/C 'A' CODE 7700 (EMERGENCY)

_Jl_ni----11 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 ± 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 ± 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 365 , 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.

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 .._ identity t 150 110 .._ present level

i. computer instruction --- "climb to FL 150"

available on demand

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-

ATC CENTRAL DATA PROCESSOR

sage as the airborne unit will not accept the address of

any other aircraft. Typical routine ATC messages as dis­

played to the pilot may be:

CLIMB

DESCEND

TURN RIGHT

TURN LEFT

CHANGE FREQUENCY

STANDARD ROUTEINGS

OCEANIC CLEARANCES

t FL 150

t FL 140

-090

~270

124.65

SR 322

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

Flow Diagram of Future ATC System

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 deriv­

ed 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 con­

troller 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~ DECCA/HARCO

.A VOR/DME

_,;.:, -,4 DECTRA/LORAN 'c'I · ~ ~' .,.-~INERTIAL /DOPPLER I

· . "' =~' _J FLIGHT LEVEL . , AIR DATA

VHF/UHF COMMUNICATIONS

ffil HE o; • • . .... . 111111 0 0 .... . .

GROUND

DERIVED

DATA

_)

.....--~t-i;:;-;~r~~_:.' :1

PLAN POSITION DISPLAY

111111 0 ••• I I I I I I 11 11 I ....

O • • •

CONTROLLER

TABULAR DISPLAY

DIGITAL IDENTITY POSITION

FLIGHT LEVEL

VHF/UHF COMMUNICATIONS

AIR

DERIVED

DATA

17

Figure 3

Satellites

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.

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.

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

Conclusion

PICTORIAL DISPLAY

LANDLINE OR MICROWAVE LINK

OCEANIC CONTROL COMPUTER

TABULAR DISPLAY

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

I . h are comp ementary in c aracter and, being independent, tem-porary 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:

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 uc-tion 1n R/T loading and hence p ' I t/ t II k I d

/ , 1 o con ro er war -Oa I

d) a continuous display for the Airline 0 f the . . f II . f . perators o

pos1t1on o a a1rcra t in which they . t d are 1n ereste .

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

The Design of on Air to Ground Asynchrono D. . I Communica-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-tion, Bournemouth, October, 1966. · · · · s

3. VICKERS, T. K. (1966) :

Beaconry for Beginners, The A.0.P.A. Pilot, October , 1966

_

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

5. SULLIVAN, W. F. (1965) :

Dato Transfer Experimenlation for (ONUS, FAA System Research and Development Service , NAFEC, Atlantic City , Report No. RD-65-110/Dec 1965.

Data Exchange

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 in­

formation if it takes a laborious, time consuming key~oard sequence to change, amend, up-date, or call-down infor-

mation. · · 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

f · t ·s likely to be provided now. We should sort o equ1pmen 1 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) K b d are provided where absolutely necessary; ey oar s . . . c) Rolling Ball/Joystick marker or light pen 1s available.

by F. J. Crewe El I iott-Automalion

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 Re-

h" ·11 be held from l 6th to 22nd April, 1967, at the searc w1 . W ·11 · c Kerckhoff Institute, Bad Nauhe1m, Germany. 1 1am . . The meeting is jointly sponsored by the Institute .of ~lec-trical and Electronics Engineers, the Deutsche Phy~1kal1sche Gesellschaft, the Verband Deutscher Elektrotechn1ker, and the Nachrichtentechnische Gesellschaft, under the chair­

manship 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

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

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

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

. h . d . ore ace wit a m1xe en~1ronment of data exchange between con-trol centres - via AFTN only, via direct telepho 1· k

d . d 1· k b ne in s, ~n via ata in s etw.een automated centres with vary-ing degrees of automation. One point howeve · I . . , r, 1s c ear: 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 · d · · ICAO 0 we are in a goo pos1t1on. established the ATC Auto-

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

h . . . d f th . a er a muc crit1s1se ?ur report in 1964 - ATCAP produced in March 1966 its fifth report which, hopeful! ·11 b

d . t' II h y, w1 e accepte 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 con-tains 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

The situation as concerns air-grou d · d 1. k · n -air ata in s 1s

not as yet so far advanced. This is pa tl d h f t . . r y ue to t e ac that the engineering problem is far g t

1 h h t'll . . . . . rea er, a t oug s 1

within the capabilities of present day t h · 1

dd' . . ec n1ques. n a 1-tion, 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 stan-dardised, 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 £ 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.rtic1-

pation 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 de­

fence, electronics and military systems fields, HUCO c~n­stitutes 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.rol­

purpose 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

I 2 I

3

I I 22

Inauguration of the ....,,

r

Eurocontrol Experimental

On 17th January 1967 Mr. Ray Mason M . P., Minister of Defence (Equipment) of the United Kingdom and President of the Permanent Commission of M inisters of the European Organisat ion for the Safety of Air Navigation Euro­control and Mr. Edgord Pisani, French Minister of Equipment, inaugu rated the Eurocontrol Experimental Cen­tre at Bretigny sur Orge near Paris, the first international air traffic control experimentation and evaluation estab­l ishment in Europe.

5

Mr. Roy Mason and Mr. Edgard Pisani w ere assisted by Mr. Rene Bulin, Director G eneral of the Eurocontrol Agency. Amongst the audience who were given a demon­stration of an a ir traffic control simulation exercise by the personnel of the Experimental Centre, using its powerful air traffic simulator, were the minister ial colleagues of Mr.

1 The Eurocontrol Experimentol Centre ot Bretigny·sur-Orge. 2 Control room - Equipment loid ou t for inouguro tion o f centre. 3 Pilafs room. 20 Plessey pilot"s consoles eoch oble to handle up to

15 a i rcra f t. 4 High speed printer, Telefunken TR 4 computer ond contro l desk,

Plessey moni tor disploy, punch cord unit. 5 Supervision posit ion - two rodor conso les, one pi lofs console.

Centre at Bretigny

6

sur Orge, France

Mason ond Mr. Pisani on the Eurocontrol Permanent Com­mission and other representatives of the seven Member Sta tes of Eurocontrol and of the States which hove entered into co-operation agreements with the Organisation, 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 insta lled by a Consortium of European elec­tronic firms and is designed to make a major contribution to the common aim of the Eurocontrol Community of pro­viding improved air traffic 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

6 Control room - Brusse ls Upper Areo Control Centre simulo tion

loyo ut. 7 Plessey pilot's co nsole , e lectronic to bulor disploy ond keyboard ,

with SAIT communications . 8 Synthe tic traffic picture on Plessey radar d isplay showi ng repor ting

points, aircra ft posi tions, 2 minute pred iction vecto rs , a bbreviated

collsig ns, Oight leve ls . 9 Plesse y horizonta l rad ar d ispl a y showing video mop, mic ro to bulor

disp lay, controls, and keybo ard.

7

8

9

23

Plessey AR -1, the m ost 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 control functions with in a range of 75 miles. A ll these operat iona l roles are carried out accurately, reliably and effectively: Ter minal area survei llance/ Approach control / Radar sequencing control I Parallel runway approach control / Outbound cont ro l from take-of! I GCA surveillance element / PPI approaches I Fig hter recovery I Low flying local traffic s urve il lance. The performance of the A R-1 in these man y roles has been stringently evaluated by civil and military au thori t ies resu lti ng

24

in over 50 equipments being adopted by authorities in all parts of the wor ld. For full data on the AR-1 or information on the Plessey range of radars, displays and data handling equipment w ri te to:- Plessey Radar Limited , Davis Road , Chessington, Surrey, Eng land. T el : 01- 3975222. Te lex: 262329

PLESSEY RADAR PLESSEY ELECTRONICS GROU P

''~PE(R)33A

Recent Developements in Collision Avoidance

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.

Th . . . d . c'al a·ircroft simulator. e training 1s one 1n a spe 1 . Pilots ore trained to read more and more instruments in~ · I · ·d ·n When there 1s singe scan, before looking outs1 e agat ·

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 terns by looking first at a wing tip. is .. . . 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 encour­

aged to use swivel-neck techniques. Th f h. . · · I d an increased accur-e results o t 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 .

by Tirey K. V~ckers Decca Navigator System, Inc.

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

5000 4000 3000 2000 1000

Code

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.

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

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?

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 .

')' .. _()

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!

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.

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.

(J) 12 ...,-;-v-0

.. ::)

~ I~ ':~i!~•il!ll lll 6t----r----1t----:-7":~~~~~:;:;:

~l-----+--7':-'.~;.;.;.;.;.;.;.,;.w;~

2 ~-----:'-

u 2()() ·WI! ()()() KOO l()l)()

Figure l Ronge 'Rote of Closure Criteria for 40-Second Tou

1200

Figure 2 Need for Range Proximity

Warnin!'.j

4

-------------+ --- ---

I ni:1~: ~ i 1)11 11f r~:: · n !n· 1 •. -"i t!11..:r ~lir..:r~1tr 1.: ou.l i...l 1..: r ... :~1r'--· 1...bn:-'."-·n,li:-: :-; it U~ H i 11 11

------------+- ------- -------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.

System Operation

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 utilize 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 ircraft's encoded altitude data.

0 200 ·WO 600 800 1000 LOO

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

Figure 3 Combined Criter ia fo r 40-Second Tau and 3 miles Range

Figure 4 Time-Ordered Reporting Scheme. Shaded boxes indicate aircraft message reservation time. Blank boxes indicate reception time .

j ()(Jl i

""" ~1-----t----;-----i-----'--+

• :::: :::: :::: :::: : : :::: : /: ~ ·_:_:=:·. ·.:_: :_:: ·.:_:~.:-_::_~_: =-:~.:~_::_:· :_::·.:::_:: ~.:~.:~_:=::-~_:=::_··::. ~.:~.:~.:~::_::~-:::._~:. ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~: ~ :

'...,_ , ( . \·,' ! 1. -'1~-----~

( ....., ~ II I ~ 1 r · , l ·, J : i ; · 1 ". ) 1 • ' : 1

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

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

Collisions

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. s. aircraft that can't afford it?

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 1 OOO

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.

~- ~ ~ ~i ---- -~,~· . .-r - ~ ~ ~- ~ ~- .;\ (·' 1 · - h :_ -~ A "!..u1 '1LlillL~·. ··~ _ _illjL.Jllll A' •: .. ·.;..C,:· .. Ji;~·. . I

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selenia air traffic control radars enhance air safety under all environmental 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.

~~~ ~ INDUSTRIE ELETTRONICHE ASSOCIATE S p 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 integrated port of the economy of any modern country.

The role which a highly developed and efficient 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.

The fact that this system works wel l today, despite of the enormous growth of air traffic (the 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 popular 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 T roffic 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. ' '

Air~roft, crew, airports, navigation, meteorological in· f?rmation, etc., all these are vita l components of any ovia · ~ton environment, Gonos said, but it would be difficult to imagi ne 0 gre.a.ter number of aircraft, operating under all weather cond1t1ons without the A. T ff" S · ' 1r ro 1c erv1ces.

Referri.ng ta. I.CAO and sim ilar bodies, and reporting about the1.r ?ct1v1t1es, Gonos illustrated the great import· ~nee that is rnterno~ionally attached to the effici ent opera· lion of the Arr T roff1c Services. He then presented a detail-ed descrip t ion of the A. T ff. c · . . 1r ro 1c ontrol System rn Greece, w ith particular mention of the excellent air safety record of that country. Specific a ttention was also devoted to the human element in the system - the pilot and the con· troller .

. Th e meeting was attended by a great number of high off1c1o ls of the Greek aviation administration the Air At­taches of many States, the air l ines, represent~t ives of the

30

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 ses-sion that followed Mr. Gonos' speech and th h I t . , e w o e even con be considered as a successful cont ·b t• t f ·

rt u ion o om1-liorising a greater number of people w ·th th · d

• • • 1 e OJms on object ives of Arr T roff1c Control.

-r

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

BELGIUM

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

Belgian Guild of Air Traffic Controllers Airport Brussels National Zaventem 1, Belgium

President Vice-President Vice-President Secretary Secretary General Treasurer Editor

CANADA

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

Canadian Air Traffic Control Association

56, Sparks Street Room 305 Ottawa 4, Canada

President Vice-President Managing Director Secretary-Treasurer IFATCA Liaison Officer

DENMARK

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

Danish Air Traffic Controllers Association Copenhagen Airport - Kastrup Denmark

Chairman Vice-Chairman Secretary Treasurer

FINLAND

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

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

Air Traffic Control Helsinki Lento Finland

Chairman Fred. Lehto Vice-Chairman Veino Pitkonen

Secretary Treasurer I FAT CA Representative Deputy

FRANCE

Heikki Nevaste Aimo Happonen Andre Remy Viljo Suhonen

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

GERMANY

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

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

GREECE

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

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

President Vice-President General Secretary Treasurer

I CELANO

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

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

ISRAEL

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

Air Traffic Controllers Association of Israel P. 0. B. 33 Lod Airport, Israel

Chairman Vice Chairman Treasurer

ITALY

Jacob Wachtel W. Katz E. Medina

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

President Chairman Secretary

LUXEMBOURG

Senator P. Caleffi C. Tuzzi L. Belluci

Luxembourg Guild of Air Traffic Controllers Luxembourg Airport

President Alfred Feltes Secretary Treasurer

NETHERLANDS

Andre Klein J.P. Kimmes

Netherland Guild of Air Traffic Controllers Postbox 7531 Schiphol Airport, Netherlands

President Vice-President Secretary Treasurer Member Member

NEW ZEALAND

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

Air Traffic Control Association Dept. of Civil Aviation, 8th Floor, Dept. Bldgs. Stout Street Wellington, New Zealand

President Hon. Secretary

NORWAY

Lufttraflkkledelsens Forening Box 135 Lysaker, Norway

Chairman Vice Chairman

32

E. Meachen R. G. Roberts

F. O!e K. Christiansen

Secretary Treasurer

SWEDEN

P. W. Pedersen A. Torres

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

Chairman E. Dahlstedt Secretary Treasurer

SWITZERLAND

B. Hinnerson C. A. Starkman

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

Chairman Secretary

UNITED KINGDOM

J. D. Monin Walter Tanner

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

Master Executive Secretary Treasurer

URUGUAY

L. S. Vass W. Rimmer E. Bradshaw

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

Chairman Secretary Treasurer

VENEZUELA

U. Pallares J. Beder M. Puchkoff

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

YUGOSLAVIA

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

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

President Secretary

I. Sirola A. Stefanovic

COS SOR

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The answer to increasing air traffic confusion is an accurate, comprehensive, automatic and reliable Nav/ATC system. 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 exibil ity and accuracy that p mit s close lateral separation of aircraft throughout the route structure.

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AT THE CONTROL CENTRE The Decca Data Link provides the controller with accurate displays of the identity, alt itude and precise position of all co-operating . aircraft, using the common reference of a high accuracy area coverage system. The use of speech is reduced and routine.reports a~e el iminated by means of unambiguous, high-speed two-way signals. It is only through an integrated system, operating from a common reference, such as Decca-Harco, that a great many ai rcraft of different types flying at various s~eeds a.nd altitudes can be efficient ly co-ord inated mto a si ng le discipl ined traffic pattern.

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