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C A N Y O U S E E T H R O U G H A C L O U D ? A S E A K N O W S H O W

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Our laser ceilometer YLAMB can normally penetratethe lower cloud strata and indicate high clouds atheights well over 15,000 ft.YLAMB with an oscilloscope will furnish the

.> meteorologist with a picture of cloud structure,multiple cloud layers and temperature inversions,while the basic unit precisely records height of cloudbase on a strip chart. YLAMB is a small, ruggedunit with low installation and operating costs.

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WE ALSO MAKE LASER RAKGE-FINDERS FOR TANKS. AEROPLANES AND LONG-DISTANCE APPLICATIONS. WRITE TO MILITARY DEPT. , ASEA, VASTERAS, SWEDEN

Runway: Atphaltl

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Instantaneous communication.

A comforting thought for the aeronaut.Anyone knows that flight without communication is almost impossiblenowadays.Communication - instantaneous communication - only comes into its ownwhen used in the form of a carefully worked-out project.For that you need a firm like Philips which combines an extensive range ofproducts with expert project engineering. The result is a turn-key projectlike the one at Accra International Airport in Ghana.

That project comprised the supply and installation of HF and VHF equipment for Accra and outlying stations, extended range VHF. operators'positions, a telegraph centre, TMA radar, VOR and a passenger-handlingsystem.But also the training of personnel to operate and maintain all that equipment. A training you take for granted if you think in projects.

N.V. PHIL IPS' TELECOMMUNICATIE INDUSTRIE - HILVERSUM - THE NETHERLANDS

M a r c o n i

c o m p l e t ea i r t r a f fi cc e n t r o i

T H E Q U E C fi a A W A H D 7 0 I N O U S T I

T h e M a r c o n i C o m p a n y L i m i t e dA N ' E N G L I S H E L E C T R I C C O M P A N Y

Radar Division, Marconi House, Chelmsford, Essex, England

Airways Surveillance RadarTerminal Area RadarSecondary Surveillance RadarSignal Processing SystemsRadar Data Processing SystemsFlight Plan Processing SystemsAutomated A.F.T.N SystemsRadar Display SystemsData Display SystemsBright (Daylight) DisplaysDistance- f rom-Threshold

I n d i c a t o r sVideo Map GeneratorsR a d a r L i n k s

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RADAR DATA EXTRACTION

m e a n s :

Digitizing of signalsSelecting the radar information onprese t c r i te r iasF r e e d o m f r o m d i s t u r b a n c e s

requ i r emen t f o r :Narrow-Band real-time transmissionCompatibility with data handlingequipment involving:Auto-trackingFlight plan calculationDaylight digital display presentationComprehensive symbol display

ach ievements :Installations of military and air trafficcontrol centres in many places inEurope illustrate the flexibility of theSRT Radar Data Handling System.

STANDARD RADIO & TELEFON AB o BARKARBY • SWEDEN ITT

I F A T C A J O U R N A L O F A I R T R A F F I C C O N T R O L

T H E C O N T R O L L E RF r a n k f u r t a m M a i n , O c t . / D e c . 1 9 6 8 V o l u m e 7 • N o . 4

P u b l i s h e r : I n t e r n a t i o n a l F e d e r a t i o n o f A i r T r a f fi c C o n -trcllers' Associations, S. C. M; 6 Frankfurt am MainN.O. 14, Bornheimer Landwehr 57a.

Officers of IFATCA: M. Cerf, President; J. R. Campbell,First Vice President; G. Atterholm, Second Vice President; G. W. Monk, Executive Secretary; H. Guddat,Honorary Secretary; B. Ruthy, Treasurer; W. H. End-lich. Editor.

Editor: Walter H. Endlich,3, rue Roosendael,Bruxelles-Forest, BelgiqueTelephone: 456248

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

Contributors ore expressing their personal points of viewand opinions, which must not necessarily coincide withthose o f t he I n te rna t i ona l Fede ra t i on o f A i r Tra f ficControllers' Associations (IFATCA).

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

Contributions ore welcome as are comments and criticism. No payment con be made for manuscripts submittedfor publication in "The Controller". The Editor reservesthe right to moke any editorial changes in manuscripts,which he believes will improve the material withoutaltering the intended meonina.

Written permission by the Editorprinting any port of this Journal.

is necessary for re-C O N T E N T S

Advertisers in this issue; ASEA (Inside Cover); The DaccaNavigator Co. Ltd. (Back Cover); The Marconi Co. Ltd.' )/ N. V. Hollandse Signcalopparaten (Inside Back

qpi^cm' Telecommunlcatie Industrie (1);bbLbNIA S.p.A. (6); SOTRAMAT S. A. (25); StandardRadio & Telefon AB (4).

Picture Credit: Board of TracAssociates (11. 19. i? lA)

de (7, 8); Glen A. Gilbert &

The Role of the Touch Display in Air Traffic ControlN. W. Orr and V. D. Hopkin

VOR/DME Area NavigationGlen A . G i l be r t

ATC and the AirportT h e U . K . G u i l d o f A T C O s

ATC and the Supersonic TransportThe U. K. Guild of ATCOs

ATC and the Supersonic TransportCopt. A. G. Payne

5

seleniaair traj^c controlr a d a r s

Twenty-three Selenia air traffic control radars have been ordered by Austria, India, Italy, Norway,Rhodesia, South Africa and Sweden. Selenia microwave links, analog PPI displays and digital displaysystems are used in many of these installations. Television-type scan conversion bright display and SSRcan also be added. Where performance, reliability and quality count, Selenia air traffic control radarsare regularly selected.

T h e R o l e o f t h eTouch Display In Air Traffic Control

By N. W. Orr and V. D. Hopkin

A b o u t t h e A u t h o r s

N. W. Orr is an Operations OfFicer I at the United Kingdom Board of Trade. Hegathered first hand experience with the touch display as project manager in thecomputer (EUCLID) group of the U. K. Air Traffic Control Evaluation Unit, Hum.Mr. Orr is now Head of Section CP 7 (Planning of Future ATC Systems) in the Directora te o f Cont ro l P lans, Nat iona l A i r Tra ffic Cont ro l Serv ices.

V. D. Hopkin is a Principal Psychologist at the Institute of Aviation Medicine, RAFFarnborough. One of his main areas of interest is Human Engineering Problems inAir Traffic Control and Air Defence Systems; this has included work on the evaluation of Touch Display principles. He is now preparing a study of Human Factors inG r o u n d C o n t r o l o f A i r c r a f t f o r A G A R D .

I n t r o d u c t i o n

At the present stage of its evolution the application ofautomation to Air Traffic Control is, in large measure, amatter of using computers to drive or print tabular trafficdisplays. The current state of the art is such that much ofthe updating and amending of these displays has to bedone by the controller or his assistant, through the computer, so that the success of any automated system depends to a considerable degree on the effectiveness of thecommunications between the controller and the computer.This man/machine interface is generally regarded as oneof the weakest points in the Controller-Aircraft-ComputerLoop.

Communication between controller and computer hashitherto relied heavily on the electro-mechanical keyboardin one form or another — a medium which may set themaximum pace at which information can be handled bythe system. R/T messages normally cannot be passed to thecomputer in the form in which they are received but haveto be converted, by the controller, into terms acceptableto a particular keyboard format. For example, items ofATC data such as aircraft callsigns may have to be codedby designating them with a letter or numeral. This conversion process is time consuming, adds ta the Controller'sworkload and is subject to human error. Additionally, thecharacters/symbols available on an orthodox keyboardare limited and inflexible. These characters and the key-

Figure 1Operator using Touch Display.

7

board layout hove to be learned by the operator and itmay take a considerable time to acquire operating proficiency. Another limitation is that the feedback from thecomputer, which allows the operator to check the accuracyof his input, has to be presented on a display remote fromthe keyboard and this may lead to problems of headmovement and v i sua l accomoda t ion , and in t roduce amb ient lighting difficulties.

The Touch Display principle offers the means of overcoming, or at least reducing, all of the above limitations.

The Touch Display, in its original form, was inventedat the Royal Radar Establishment by Mr. E. A. Johnson,and the first evaluat ion of i ts use in an air t raffic controlcontext was carr ied out at the Board of Trade's ATC Evaluation Unit at Hum in 1965/66. Since then several furthereva lua t ions in va r ious ATC env i ronments hove been conducted at the ATCEU in conjunction with the RAF Instituteo f A v i a t i o n M e d i c i n e .

The advantages of the Touch Display as an input devicefor some ATC tasks appeared so self-evident that certainplans for including it in future systems were formulatedbefore the eva lua t ion t r ia ls had confirmed i ts wor th . For

tunately these decisions hove largely proved sound as theevaluations have confirmed that the Touch Display functions very efficiently as an input device and, in the main,is preferable to the conventional keyboard for most inputting tasks.

Description of the Touch DisplayA Touch Display is a touch sensitive electronic data

display designed to exploit the operators' body capacityin such a manner that a finger touch on an electronicalcontact — a "touch-wire" — produces a capacitance andresistance to earth which unbalances an inductance capacitance bridge. This produces a signal which can be used

to activate a digital computer. In the version illustratedhere (Figs. 1 to 3), twenty-four touchwires ore arranged infour rows of six wires per row.

A Touch Display coupled to a computer con be regarded as a keybord, the "key" labelling of which may bevaried by computer program to suit any particular requirement. In addition to the key labels, further informationmay be presented on the display, by the computer, as andwhen required. A Touch Display therefore combines thefunc t i ons o f keyboa rd and d i sp lay. I n o the rwords — the input and output functions ore integrated..

A simple example of its use in a suggested ATC role isillustrated in Figs. 2 and 3, and the touch display functioninvolved are described in the captions.

Advantages of the Touch Displayover the Conventional Keyboard

The first evaluation conducted by the ATCEU comparedresults obtained by operators using the Touch Display withthose obtained in an earlier trial in which a conventionalkeyboard had been used in an otherwise identical operational role ("en route" Sector Radar Controller). Amongthe findings of these trials were the following:1. The training time necessary for operators to reach an

acceptable level of proficiency using the Touch Displayis significently less than that for the conventional keyb o a r d .

2. Most of the searching and coding problems hithertoassociated with locating displayed information areavoided. Only information essential to the operator'simmediate requirements need be displayed — the restis stored but can be made instantly available whenrequired. Information on touchwire labels can be written in full or with only partial abbreviation. This dis-

5ARPZ OiJ03 A1 138 GARP.4R/ir EAST

SARPZ T/OFF NOK 'TRI LEFT TURN FAI *2

RADAR 128,5

E N I S B A C J C I K

GAR^ OA 408 AI 108 GARP.H

Figure 2 and Figure 3

Suggested Use of the Touch Display for Aerodromes Control.(A method of meeting the requirement to inform the computer In a central processing complex, of the "airborne" times of aircraft departingfrom an aerodrome.)in Fig. 2 (the "REST" picture) an Aerodrome Controller is presented withthe callsigns of aircraft about to depart from his airfield. These callsignshave been "fed" to the display by the Ground Movement Controllershortly before they reached the runway holding point.The take-off direction is also displayed and a digital clock appears inthe top right hand corner of the display.If the controller touches the touchwire under any collsign he will bepresented with the aircraft's relevant flight data (Fig. 3: GARPZ).When the aircraft takes off he touches the wire under "ENTER" and this

action immediately informs the main processing computer of the time oftake-off and initiates the necessary action to notify the "en-route" controllers of this event. The aerodrome controller's display then returns tothe "REST" position — but the aircraft which has just departed willnow be omitted from the list of callsigns (which will all move up to theleft to "fill the gap").Should the controller at any time wish to return to the "REST" positionfrom the "Flight Plan" display (Fig. 3), before the aircraft concernedbecomes airborne, he may do this by touching the wire under "BACK-T R K " .

It will be seen that this Touch Display format also provides the aerodrome controller with the means of notifying the computer of changesof take-off direction (Fig. 2).

8

penses with the clumsy data line and field identificationprocedures necessary in some systems which use orthodox keyboards in conjunction with independent displays. Both these features effectively contribute tolightening the operator's workload by substantiallyreducing the search aspect of the task.

3. The operator can be "led'' through any desired sequence of displays by appropriate computer programming — by presenting him with the set of touchwirelabels which must be used next. (This is one of thefactors which helps to reduce operator training time).

4. By showing only information directly relevant to agiven input both on the display proper and on thetouchwire labels, it is possible to present an identicallayout on each. This avoids the problems associatedwith a fixed keyboard of making its layout logicallycompatible with the other displayed data.

5. Because the orthodox keyboard requires mechanicaldepression of the keys it is slower and demands moreeffort to operate than a touchwire system. Potentiallytherefore the Touch Display can provide a faster rateof input.

6. The Touch Display is silent in operation.Perhaps the most important finding of these trials, how

ever, was that the operators seemed to derive genuinepleasure from using the Touch Display, and all of themwere extremely enthusiastic about it. This contrasted markedly with the attitude encountered in the trials using theconventional keyboard.

In a later project (North Atlantic Oceanic Controlenvironment) operators worked at their own pace ratherthan at the rate set by incoming messages. The superiorityof the Touch Display over the keyboard in this role wasconfirmed, and the trial also showed that performancewith the Touch Display could be further improved by suitable computer programming designed to reduce the number of touches required to input any given message.

In addition to the updating of controllers' traffic displays, an important role to which the Touch Display maybe applied is that of liaison between one controller andanother, through the computer. Any system which mighthelp to lessen the ever growing volume of ATC verbalcommunications — already near saturation point — cannot be lightly dismissed.

Employment of the Touch Display in the "liaison" datat rans fe r r o l e has been eva lua ted a t t he ATCEU i n bo thControlled Airspace and Middle Airspace environmentsand these evaluations have produced encouraging resultswhich give reasonable grounds for optimism that theTouch Display's contribution to this aspect of ATC will bean important one. The points which most impressed thosewho witnessed these projects were, once again:a) the speed, ease and accuracy with which data could be

transferred and displayed;b) the relatively small amount of training and practice

needed by operators to acquire proficiency with theTouch Display;

c) less susceptibility to human error than a system relying on verbal communications;

d) the silence of the operations room.

A Note on Operator TrainingExperience on a series of trials has shown that it is pos

sible to introduce operators to the principles of using the

touch display by employing books of illustrations of thevarious display sequences, in which the turning of a pagecorresponds to the touching of a wire. By this methodoperators can be familiarised with the way in which thetouch display works and has been programmed. It is thuspossible for potential operators to become familiar withtouch display formats and routines without having to usethe actual device itself, thus effectively reducing theamount of costly computer tim.e otherwise necessary during training. It has been found that after such introductorytraining it is possible for operators to become rapidlyproficient on the touch display itself.

ErgonomicsThe angle of slope of the face of the Touch Display

presents the most important of the ergonomic problemsassociated with this equipment and has been examined bythe ATCEU/IAM. It would appear that an angle of between 30° and 40° to the horizontal is the optimum angle,which is a compromise between treating the Touch Displayas a keyboard — when it should be nearly horizontal —and treating it as a display — when the face should beperpendicular to the operator's line of sight (usually about60° to the horizontal for a seated observer with the display at desk top height).

N. B. The angle of the face of the Touch Display shownin Fig. 1 (62V2°) although ideal for viewing purposes wasfound by the majority of operators to be much too steepfor comfortable touching.

However, any display at 30° —40° to the horizontalnormally presents considerable problems of lighting andreflections. One possible solution to this dilemma is todetach the touchwires from the display. This would allowtouchwires (keyboard) and display each to be set at itsown optimum angle although retaining their same relativepositions In the other planes. Thus other ergonomic problems such OS lighting difficulties could be largely overcome. If such a system-were to be adopted, then conventional keys m.ight be used instead of touchwires — the layout of the keys corresponding to the layout of the labelson the display above, thus preserving most of the advantages of the Touch Display principle. However there aresome obvious operating difficulties in such an arrangement and these are to be examined experimentally in thenear future at the ATCEU.

I n Conc lus i on

This article has covered only a few of the possibleapplications of the Touch Display to ATC of the future,and everyone who has been concerned with the evaluationof this device is convinced that many other ways will befound of exploiting its latent potential. The evidence todate suggests that the touch display principle representsa major advance in the field of man/computer communications, and that it is particularly suited to Air Traffic Control. The few problems associated with its use should beovercome fairly quickly.

The enthusiasm commonly shown by those who haveused the Touch Display may indicate an appreciation thatthe application of automation to Air Traffic Control, atleast in this instance of its evolutionary progress, can helpto make the controller's task an easier and more congenial one.

9

VOR/DME Area NavigationBy Glen A. Gilbert

i n t r o d u c t i o n

Although area navigation has been recognized for thepast some twenty years as being desirable, it has not gained significant usage for two principal reasons:

1. The Air Traffic Control System had not been organizedin a way such as to give most effective application toarea navigation-equipped aircraft; and

2. Airspace users were reluctant to spend money for theinstallation of airborne area navigation equipment unless they were assured that the Air Traffic Control System would permit them to achieve the various capabilities provided by area navigation.

In more recent years, this sort of "impasse" has beenrapidly changing. For example, the U.S. Federal AviationAgency in a 1965 Advisory Circular said: "It is the FAA'spolicy to encourage orderly progression towards the further development and operational use of airborne areanavigation equipment."

The U.S. Airline Pilot's Association in a 1966 symposiumon Air Traffic Control problems stated: "To achieve maximum efficiency in the utilization of the air space, it isdesirable that pilots and controllers be permitted tochange or assign routes respectively on an area basisrather than be restricted to the use of certain prescribedroutes." The same report went on to say: "Unnecessarynavigational instructions not required for separation ofaircraft are being given which causes controllers to devoteless time to approach planning, and distracts pilots withunnecessary radio communications and workload."

The report of the ICAO Fifth EUM/RAN Meeting conducted in 1966 urged that "States be encouraged to continue studies and experiments intended to improve andfurther develop the use of VOR/DME, especially with regard to its use as an area type navigation and that anyresults of such studies or experiments be made availableto ICAO for transmission to other interested States".

In June of this year, the Air Transport Association ofAmerica pointed out that "area coverage navigation (fromVOR/DME stations) can offer distinct advantages throughthe capability to fly routes using cockpit navigation whichwould otherwise not be practical without radar vectors orother navigation from the ground".

W h e r e w e a r e n o w

In the United States, the Federal Aviation Administration, in cooperation with airlines, general aviation and themilitary services, as well as with avionics manufacturers,is developing standards for "approved" area navigation— "ARNAV" — airborne equipment. Along with thesestandards, the FAA is establishing the operational procedures to be followed as area navigation becomes incorporated into the U. S. Air Traffic Control System. AirborneARNAV equipment of several different manufacturers isnow being used by various airlines for operational application. It is clear that introduction of area navigation inthe United States — particularly using VOR/DME (andTACAN) facilities — is well under way, both as to airborne

ARNAV equipment and as to introduction of area navigation concepts into the Air Traffic Control System.

In Europe, the U.S. Federal Aviation Administrationhas demonstrated area navigation capability using VOR/DME inputs on a significant basis during the past twoyears. Eurocontrol also is giving considerable attention toarea navigation concepts in its ATC planning.

Thus, the stage now has been pretty well set to moveinto the age of area navigation on an increasing basis inmany parts of the world, and it may be expected that theseconcepts will be the basis for the development of Standards and Recommended Practices by the InternationalCivil Aviation Organization at a relatively early date.

Advantages of Area NavigationA number of different concepts for area navigation

have been developed, including such self-sufficient systems as inertial and Doppler, and others based on inputsfrom hyperbolic transmitting chains. However, the widespread installation of VOR/DME (VORTAC-TACAN) groundstations in North America, Western Europe, and otherparts of the world, would appear to give this system thegreatest capability to the largest number of airspace users

airline, general aviation, and military — as a commonreference input source for economical airborne area navigation equipment.

One of the area navigation systems using VOR/DME(or TACAN) inputs is the Vector Analog Computer, orVAC , manufactured by Butler National Corporation of

the United States. This equipment is the result of over tenyears of research, development, and successful evaluation,with many thousands of hours of flight time experience. Itis now in production on on off-the-shelf basis for use byairline, military, and general aviation aircraft. The militaryversion can operate from pure TACAN facilities (as wellas from the VOR/DME input). The general aviation versionwill be produced at a price sufficiently low so that itshould be attractive to a large segment of this class ofai r t ra ffic .

An explanation of how the VAC equipment functionsand its application in different air traffic environmentsshould be representative of the manner in which areanavigation equipped aircraft may be expected to operateand the resultant implications to the Air Traffic ControlSystem.

Such an area navigation airborne system will permitaircraft to be flown on the most direct routes, along closely spaced parallel tracks or other routings which the ATCSystem may prescribe, so long as the aircraft are in receiving range of a VOR/DME ground station. Fig. 1 shows thetheoretical altitude/!ine-of-sightrelationship forVORsignalcoverage; elevating the ground stations by appropriatesiting will, of course, improve the line-of-sight coverage.In any event, depending upon the altitude levels at whichsignals from VOR/DME stations should be received, it isobvious that proper location of ground stations on amore or less "grid" basis would permit significant areanavigation coverage over any desired ground area with amin imum of VOR/DME fac i l i t ies .

1 0

Economic benefits will accrue to the airspace users byvirtue of their ability to fly more direct routes and saveflight time. In addition, thousands of airports — and unprepared landing areas — can be given some level ofinstrument approach capability, without the need for localinstrument landing facilities. Thus, numerous communitiesand areas can be opened to more reliable air services,both commercial and private, and by both conventionaland V/STOL a i rc ra f t .

The Air Traffic Control System will benefit by beingable to increase efficiency in the utilization of airspace; itwill have greater flexibility in providing lateral separationbetween aircraft through assignment of multiple flightpaths and closely spaced parallel tracks; diversified routestructures will help reduce the possibility of midair collisions. Routine communications workload of controllers —and pilots — will be reduced substantially, particularly interminal areas, by transfer of navigation from the groundinto the cockpit. Controllers will thus hove more time todevote their attention to their primary function of coll i s i o n p r e v e n t i o n a n d e x p e d i t i n g t r a f fi cflow; air safety, consequently, will be raised and delays due to traffic congestion will be reduced.

H o w t h e " VA C " w o r k s

The Vector Analog Computer System permits flight overany desired path in the airspace, as well as to any location on the surface (if within receiving range of a groundVOR/DME station) by selecting one or more locations onthe surface, called "waypoints". Each waypoint is definedby its distance and bearing from a VOR/DME station.These distance (Rho) — bearing (Theta) "coordinates" aredialed into the waypoint selector control illustrated inFig. 2, and the desired track to be flown to the waypointis then set into the cockpit instrument known as the Symbolic Pictorial Indicator (SRI) shown in Fig. 3.

The Symbolic Pictorial Indicator incorporates two cross-pointers — horizontal and vertical. The vertical pointerdisplays distance to the left or right of the selected trackwhile the horizontal pointer displays distance to or fromthe waypoint. In addition to the crosspointer indicator, adigital indicator (see Fig. 4) is provided to continuouslydisplay distance in nautical miles to and from the way-point. A rotatable aircraft symbol in the center of theSymbolic Pictorial Indicator shows the relative heading ofthe aircraft with respect to the waypoint. Keeping the vertical pointer centered means that the aircraft is on the

S I G H T D I S TA N C E I N M I L E S

Figure 1

Theoretical Linse of Sight Coverage of VOR/DME Facilities in Relationto Aircraft Altitude.

Figure 3

Symbolic Picforial Indicator (SPI).

11

Figure 4

Digital indicator Showing Distance (up to 200 n.m.) TO and FROM aWoypo in t .

desired track; when the horizontal pointer intersects thevertical pointer at the center of the indicator, the aircraftis over the woypoint. Vertical and horizontal hash-marksrepresenting "deviation lines" ore provided on the face ofthe SPI. Each hash-mark can be equivalent to 1, 2 or 10nautical miles, depending on the scale factor selected bythe pilot.

An optional feature provides that two waypoints maybe set into the computer at the same time by means of adual woypoint selector control, as illustrated in Fig. 5.When the pilot wishes to use the next woypoint, he merelyswitches over to the other preset woypoint selector. Thus,waypoints can be "leap-frogged", giving the pilot time toset in the next woypoint leisurely as the flight proceeds.An optional feature permits pre-progromming as manywaypoints and tracks as may be desired. When the aircraftis at predetermined points in space during the flight, thenext woypoint and new track ore set in automatically atthe some t ime tha t the a i rc ra f t ' s VOR/DME rece ive rs o re

automatically tuned to the new ground station.The drawing in Fig. 6 shows how simply the pilot can

interpret his position on the SPI once he has set in a desired woypoint and track to be flown. In this illustration, thfwoypoint is 45° to the right of the pilot (1); the woypoinis 3, 6, or 30 nautical miles ahead of the pilot (2), depending upon the scale set into the woypoint selector; the pilois flying 4, 8, or 40 nautical miles parallel to and to th(left of the track to the woypoint (3), as per selected scaleTo reach the woypoint, the pilot would turn the aircraft t(the right, heading towards the intersection of the crosspointers, and the vertical pointer would start moving tc

, , f j1'

rFigure 6Representation of a Waypoint on the SPI.

Figure 5VAC Dual Waypoint Selector

Figure 7

Rectangular Pattern for VAC Approach to a Runway Showing RelativeS P I R e a d o u t s .

1 2

As the vertical pointer approaches the aircraft symbol, thepilot would commence a left turn and get the aircraft backon the previously selected track by centering the verticalcrosspointer. At the same time, the horizontal crosspointerwould be moving downward continuously showing distance still to go to the waypoint.

another waypoint set in at the runway threshold. Fig.shows the type of ''software'' in the form of approodcharts that might be developed for selected airports awhich VAC approaches would be planned on a regulob a s i s .

Approaches to AirportsIn making an approach to an airport (or any landing

area) without the need for a local landing aid, such as anILS, the pilot may place the waypoint in the center of therunway to be used (refer to Fig. 7). In this illustration, theaircraft is approaching the airport on a track of 45°, andobviously would remain at whatever the minimum approachaltitude was established for that particular location untilover the waypoint.

Once over the waypoint (center of the runway), thepilot would change to the track or bearing of the runway[in this illustration shown as 00° — or 360°). A standardpattern is then followed involving a downwind leg, a basel a a . a n d t h R fi n n i n n n r n n r h I r h : a t f ; e l e c t e d D o i n t s a l o n a

Holding PatternsIn the event that ATC requires an aircraft to hold

either enroute or on approaching a terminal area, th(controller would identify to the pilot what waypoint he ito use as a holding point. This may be done by giving th<coordinates of the waypoint, or by reference to predetermined waypoints shown on charts. Fig. 9 illustrates th(simplicity and accuracy with which a pilot may carry oua holding pattern (in this case circular) by orbiting arounca waypoint. Alternatively, a "racetrack" holding pattencould be carried out readily using the same flight technique as that illustrated in Fig. 7.

i n T e r m i n a l a r e a o p e r a t i o n s , r n e v e c t o r A n a i o g c o m

puter will permit pilots to follow pre-organized arrivaland departure flight paths laid out in accordance with themost efficient traffic patterns. These patterns also couldspecify "standard" altitudes to be followed at specificpoints along the flight paths. Fig. 10 illustrates this concepton a hypothetical basis for departure flight paths usingone waypoint at the end of a departure runway. A similartechnique would be followed in setting up arrival flighto a t h s f o r a o n r t i r u l n r r t i n w n v

Concep fua l Gu ide fo r VATerminal Area Operat ions.

Pre-Orgonized Depar ture F l ight Paths in

The pre-organized flight paths would be shown on specially prepared terminal area charts, and each path wouldbe given a discrete identification. It would then be possible for the controllers to supply precise routing instructions to pilots, merely by stating the desired flight pathidentification. Each pilot would follow, on his own responsibility, his assigned flight path by reference to his Symbol ic P ic tor ia l Ind icator. The cont ro l ler would do no d i rectvectoring unless, by radar monitoring, he determines thata particular aircraft is not following the specified path, orthat some modification to the standard traffic pattern isn e e d e d .

If desired by a particular user, the VAC can drive various types of pictorial displays of X-Y plotters with mopbackground to supplement the Symbolic Pictorial Indicatorduring terminal area operations. With such a supplemental display, the pilot con double-check track being madegood by occasionally referring to the position of the tracing or cursor showing his location on the background map.Such combination of the VAC with a pictorial display isbeing used by the U. S. Federal Aviation Administration intheir area navigation demonstrations in Europe, referredt o e a r l i e r .

AccuracyThe Vector Analog Computer Area Navigation System

provides unique accuracy because of the high grade computer used in the system, the large scale which may beshown on the Symbolic Pictorial Indicator (as great as4 nautical miles to the inch) and its special distance-proportional filtering feature which minimizes the effectsof reflections, course bending, and scalloping in the radiated signals of the VOR ground stations. Operationalaccuracy of the VAC System (exclusive of any errors whichmay be generated by the ground station or aircraft receivers) permits track accuracy within 1% (RSS) of the aircraft's distance from the computed woypoint.

SummaryOne of the most pressing problems in the field of air

transportation is how to use the airspace more efficiently,both as to conventional fixed wing aircraft and as toV/STOL s. Multiple airports and other landing areas mustbe made available for reasonably reliable service in allweather conditions without the necessity of having expensive ground landing aids at each such location. En-route flying must be possible using direct routes, ratherthan circuitous "airways", so as to reduce unnecessary,costly flying time to the minimum. Delays due to air trafficcongestion now costing millions of dollars every month-- must be sharply reduced. More capability must be provided to the ground-based air traffic control system andthe pilot to effect precise lateral separation by being ableto follow pre-established parallel and multiple flight pathsbetween airports and within airport terminal areas. Newconcepts of super-highways" of the air, over-passes andunder-passes, will greatly improve protection against midair collisions. Area navigation effectively meets thesechallenges.

VOR/DME area navigation can economically serve allclasses of airspace users. The challenge is for States toprovide more effective coverage of VOR/DME groundfacilities the ICAO approved short range navigationaid — so as to give greater area navigation capability toall significant airspace over their national territories; forairspace users to install suitable airborne area navigationequipment with all possible speed; and for the Air TrafficControl Systems of the different countries to adopt theirprocedures for the early introduction of area navigationconcepts.

About the AuthorA principal organizer and founder of the U.S. Air

Traffic Control System, Gilbert became the first head ofthe Federal Air Traffic Control Service when this activitywas assumed by the Government in 1936. He served inthis capacity until 1947 when he was named as a SpecialAssistant to the Administrator of Civil Aeronautics in thedevelopment of United States air policy in the post-waryears. During the next five years, he served on numerousUnited States delegations to international aviation con-ferences throughout the world os delegate or head ofdelegation. After 15 years of service, Gilbert left theGovernment In 1951 to enter the field of aviation consulting. During the next six years he served as an AviationAdvisor in the United Nations' Technical Assistance Program, and amongst other activities In this capacity heorganized and directed a civil aviation training center InMexico, serving all of the Latin American countries. In1957 he established his consulting headquarters In Miamias Glen A. Gilbert & Associates, specializing In studiesand analyses, product evaluations and operational problems on a broad basis In the field of aviation — airline,general aviation, and military. An active pilot for over30 years with multi-engine and Instrument ratings, Gilberthas written many papers and articles on various aviationsubjects but with considerable emphasis on the problemsof Air Traffic Control. Gilbert Is now completing a book,soon to be published, which will treat the subject of AirTraffic Control In all of Its diverse aspects and will beinternational in scope.

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ATC and the AirportPresented by the U. K. Guild of AirTraffic Control Officers, at the Guild'sAnnual Convent ion, Bournemouth 1968,

I n t r o d u c t i o n

This Paper attempts to highlight some of the ATCaspects at the airport, and The Guild recognises that theneeds of airports are as varied as the airports themselvesand the traffic flow they generate. It is on this occasionimpossible to cater specifically for the smaller aerodromes, and a bias will inevitably be directed to the requirements of a major international airport. The emphasisis upon the operational problems, but we do not forgetthe inseparable association existing between air trafficcontrol, the Airport Authority, airport users and thoseother agencies necessarily involved in overall airport operation; we are all aware that aircraft delays can ripplefar beyond the airport boundaries and hence the needfor every effort to avoid them. This is a vast and absorbingsubject, some ATC aspects in themselves, for instanceGround Movement Control at large terminals, provideenough subject matter for a full symposium. We will startwith a short history.

The Early DaysAirport ATC in this country has made a considerable

advance from 1st introduction by the Civil Aviation Department of the Air Ministry at certain civil aerodromes during the 1930s. Those were the days of grass aerodromes,with little more than Aldis Lamps and Very Pistols to assistthe civil controller and his military counterpart — the"duty pilot''. He had to position the landing Tee, and theparaphernalia contained within the Signals Square, andlay a Flare Path at night as near into wind as his experience and that of his Met. colleague could predict. Later hewas able to communicate with some aircraft by means ofW/T and a device called the "Q" code; this enabled himto advise "engines overhead", an early form of CAT 3!

In 1938, the situation was still much the same, thougha number of Control Towers had been built — as opposedto the early wooden huts on stilts — HF/RT was enteringthe communication scene, and early forms of StandardBeam Approach underlined the future trend. No AreaControl Centres existed, but some major international airports were beginning to provide an Air Traffic Service onroutes established by scheduled airline services (e. g. Croydon — Le Bourget).

Considerable advancements were made between 1939 —1945 in equipment and facilities to serve ATC and theaerodromes. VHF/RT was the standard communicationlink when the next generation airports, such as Prestwickand Hum, were opened, but the "Q" Code continued to beused for a few more years for W/T purposes.

Some MF Radio Ranges were available for navigational and approach use and GCA radar followed shortly.Airports had hard surfaced runways and taxyways withapproach and runway lighting. These improvements con

tinued through the introduction of ILS, Surveillance Radar,PAR and ASMI to the present day.

ATC has developed, in parallel — although not alwaysin step — with the growth of airports from grass fields toconcrete jungles, and from the days of elementary localcontrol, progressing from the provision of separate Aerodrome and Approach Controls to the complex TerminalArea systems which exist today. This has been dictated byan aviation growth rate far in excess of that in otheri n d u s t r i e s .

M o v e m e n t I n c r e a s e s

An immedia te ind ica t ion o f annua l movement increaseis obvious by the fact that the movements for Heathrow in1947 (29,590) were nearly met within one month this summer. The sustained increases over the following twentyyears indicate a trend which allows a forecast movementrate for 1977 of over half a million, but the saturation ceiling is considered to be nearer 400,000.

Having mentioned this much, however, ATC and theairport are primarily concerned with the hourly rateof movement, as it is on this factor that capacities areestablished — but more of this later.

In keeping with the increased movement rate, transportaircraft have changed dramatically in both size and performance over the last 20 years, and more is yet to come!The normal commercially healthy game of airline economics sets the pace, and we who are operationally concerned desperately try to keep up, but never quite makeit .

Development of Radar SequencingThe Approach Control Service provided procedural

separation to the traffic circuit which aircraft normallyjoined in the Downwind position. The introduction of GCAradar techniques within the local traffic zone demonstratedthat aircraft could be marshalled more expeditiously thanby pilot or controller-applied visual methods. The civilATC at Northolt (I think) can take the credit for being thefirst to introduce radar sequencing procedures as we nowknow them. Subsequently improved radars and instrumentapproach aids have enabled the approach separationsbetween aircraft to be reduced to cope with higher landing rates demanded by increased traffic. Correspondingly,the excessive intervals between departing aircraft havebeen considerably reduced by the use of Area/ApproachC o n t r o l r a d a r s a n d t h e a l l o c a t i o n o f n o n - c o n fl i c t t r a c k sbetween arrivals and departures as much as possible.Hindsight indicates a lack of foresight in some respectsconcering ATC planning, and the introduction of radarsequencing is a good example of a procedure being introduced through sheer necessity by the controllers on thejob seeing the problem and providing their own solution.

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The Present

Today, civil aerodromes in the United Kingdom areoperated either by the British Airports Authority, localauthorities or by private companies, ATC service is provided by the National Air Traffic Control Services, butmany local authorities and larger private aerodromesemploy their own ATC personnel. Controllers at all licensed civil aerodromes ore required to hold a Boardof Trade ATC L icence.

The Guild stated, at its last Convention, the operationaldesirability in the United Kingdom for this "mixture" ofGovernment, Local Authority and private company airtraffic control to be brought within one independent national Aviation Authority embracing all flight safety aspects.It is not the purpose of this particular paper to pursue thispoint but we would emphasise the need still exists for ATCloyalties to be channelled within one "Trinity House -typestructure able to meet the flight safety demands of the dayand age with vigour and operational flexibility.

In Terminal Areas, where military or small civil aerodromes ore located sufficiently close to the major airporteither to warrant the co-ordination of all or some airtraffic, or the provision of Approach Control Service bythe major airport, the air traffic controllers concerned,whether Government-employed, non-goverment or military, are all working to a common aim —- the safe movement of air traffic within and adjacent to their own areas.

All controllers must first qualify at an Aerodrome Unit,although within the NATCS some will subsequently transfer to Area Control duties. It is probably true to say thatthe majority of controllers, if given the choice, would prefer to work at an airport because it is only there that theycan actually see the aircraft they are controlling.

At airport there is a sense of "involvement" from seeing the effect of a cross wind component or water on therunway to the provision of RVR, the effect of snow clearance action, bird strikes, and full emergencies — it's allh a p p e n i n g ! . .

Another aspect which is not generally appreciated isthat no airport is ever complete — it is always being maintained or under development — and ATC have to operatein spite of the work in progress. Area units do not have tosuffer 5 miles of Amber One being dug up!

Probably because Aerodrome Units are on the spot asopposed to the normally remote Area Unit, there is greater contact between pilot and controller, although not tothe extent that the Guild would wish. There is also a closetie with the operating companies, though a disadvantageof this is that the airport ATC has to shoulder the first blastwhen delays occur.

Current and Future AspectsATC at most airports is inextricably interlocked with

the Area Control system and is the essential link betweenthe Terminal Area complex and the runway — that valuable piece of real estate which is so expensive to lease forG very short period, and when you do manage to get onit, sometimes after waiting in a queue, ATC are immediately serving you notice to quit. The technique of TerminalArea Control is properly the subject of a separate study,but the Airport Approach Control is very directly concerned with arrival and departure tracks, holding proceduresand the availability of airspace. The volume of movementsat an airport is influenced by a number of contributory

factors, not the least being the ability of the en-route system and adjoining systems to accept departures from theairport, and the airport's competence to accept arrivalsfrom Area Control. This competence in turn is affected bya number of things — the number and direction of runways, the taxyways layout, the aircraft apron complex,approach and ground aids, the method of handover fromone control function to another, and so on.

It is stating the obvious but the conclusion drawn hereis that the airport, TMA and Area Control systems must beplanned as an integrated system and not in isolation; onefactor which can have an adverse effect on the spacing ofthe inbound flow at an airport concerns traffic overflyingthe TMA at slow speeds in the lower flight levels. Intelligent new aerodrome siting and careful consideration ofnew routeings to prevent this are necessary.

This then leads us to runway utilisation and capacity.Runway utilisation is something which has changed considerably over the years. Once upon a time airports had aconventional 3-runway layout and aircraft took off andlanded on the duty runway, then there came a trend tomake greater use of the main instrument runway due to itsbetter facilities and improved aircraft performance, andless use was made of the subsidiaries. This has been followed by the construction of parallel runways, and nodoubt "London's No. 3" will have at least two sets of parallels. But whatever the layout, the utilisation of single,dual, parallel, tangential or crossing runways depends ona n u m b e r o f f a c t o r s :

Preferential direction procedures, distance apart, pointof runway intersections, compatible lengths, availability ofaids, effect of development and maintenance work on theairport, to name but a few. At busy airports with a hightraffic offering ATC must make the best use of all available concrete, bearing all these factors in mind.

Runway capacity in turn is infinitely variable. If allaircraft had a common performance, if there were noequipment unserviceabilities, if the weather was alwaysgood, and if everything went just right, very high movement rates could be achieved — but life's not like that, forindeed we have to consider the following factors:

— Aircraft from high performance jets to single enginedprivate and executive aircraft with widely differentapproach speeds,

— Noise abatement procedures leading to less flexibletechniques.

— At international airports the language factor.(At O'Hare everybody speaks American)

— Availability of good turn-on and fast turn-off taxyways,and adequate holding areas,

— Wa k e t u r b u l e n c e .— Requirement to cross active runways by aircraft under

tow positioning to/from maintenance areas, and airport vehicles.

So what can ATC do? Radar sequencing with speedcontrol on approach is used to achieve the minimum spacing and the highest landing rate. Use of subsidiary runways and short take-off techniques from intersections canincrease the departure rate, but the greatest contributionto high runway capacities is slick operation by pilots toachieve the minimum runway occupancy. Pilots used tobusy airports will accept this situation because they havebeen conditioned to the high tempo, but pilots normallyoperating in quieter zones need to be urged to "get on

16

and off" without delay. Similarly controllers need to appreciate that it is only they who can initiate the tempo. Certainly the mutual programme of education at Heathrowover the post two years has paid off, and hourly rateshave increased. A final word about parallel runways, thecur rent t ra ffic demand wi l l dec ide whether i t i s be t te r touse them in a dual configuration but as traffic increasesand all hours become peak hours, parallel operations mustapply to a for greater degree.

And so to the FutureMuch has already been published about All Weather

Operations, but our purpose here is to see what part ATChas to play, and what problems we may have to face. Onthis basis AWO are split into two phases: (1) from commencement of final approach to end of roll out, and (2)taxying from runway to apron and vice versa, using CAT3C cr i te r ia .

For the first phase it seems likely that a "Final Controller" position will need to be established in ApproachControl for communication with the pilot during the extent of this phase, though not "monitoring" the approachas the PAR controller does now. Whilst his precise functions and responsibilities have not yet been established,the Guild is aware of a proposal that the position beequipped with displays indicating the availability and serviceability of all the essential guidance systems requiredfor this operation, so that in the event of a total or partialfailure of any one of them the pilot would be immediatelyadvised. Rather than make the "Final Controller" becomea systems analyser, we suggest that any such display panelincorporate a computing device which would simply indicate a down grading of category, and would in effect raisethe minima for the approach. A nice balance needs to bestruck over the amount of information that can be passedon on R/T frequency; pilots naturally want as much information as possible, whilst controllers ore naturally concerned about frequency loading and question whether thepilot can assimilate it all. A flight deck datalink TV displayof information would assist pilots and reduce R/T congest ion.

In progressing towards the CAT 3C era, experiencewill show the extent to which spacing on final approachmust be increased to allow sufficient time to "pick-up" therunway turn off system (instrument or visual), and be clearbefore the next aircraft is at the threshold.

The single runway airport would be further penalisedif the CAT 3C ILS is sufficiently critical as to prelude adeparture being over the locoliser whilst on arrival is onapproach due to interference set-up. In this event no aircraft could be positioned on final approach until the preceding departure was airborne and upwind of the locoliser; i.e. runway sterilisation for about 6 to 7 minutes.Aircraft must continue to be held as close to the runwayas possible to preserve maximum utilisation. If future glidepath restricted areas become extended so that the departure holding point is compromised, the glide path elementwill need to be resited further upwind and a displacedlanding threshold introduced.

Phase 2

Taxyway guidance systems, including runway turn offs,fall into two categories, visual and instrumental. The first

is a high intensity centre line lighting system which shouldbe adequate for conditions down to about 50 metres. Thesecond, still very much in the development stage, includesleader cable, and radio active isotope systems, and it issuggested that instrumental guidance will be necessaryfor conditions below 50 metres. V/hichever system is used,ATC will be concerned with controlling ground movements, selecting route guidance and generally monitoringthe progress of all traffic. Monitoring can be done fromASMI displays, but as movements increase under very lowvisibility conditions it will be necessary to identify individual aircraft on the display, perhaps by some meanssimilar to SSR.

Route guidance by centre line lights would in all probability be installed in all taxyways of the airport, andselection and protection of routes can be undertaken byATC using established methods. It is not known whetherthis would applyto an instrumental system, but the requirement remains the same.

In addition to aircraft movements, ATC ore also concerned with the movement of emergency services and otheressential vehicles. If a visual guidance system is installed,route indication con be given by ATC as for aircraft. Vehicles can similarly be monitored on ASMI, but at thesame time such vehicles should be able to navigate independently on a system contained within the vehicle —several of these have already been evaluated.

Next Generation AircraftThree new types of aircraft need to be considered to

gether with their effect on ATC and the airport in general;these are the 747, the SST which is the subject of the nextGuild paper and the Airbus (L.lOll, DCIO, A300 etc.). TheGuild considers that the 747 will have no significant impact on ATC — in fact for a short while there may be aslight reduction in movements as one 747 capacity equalsthat of about three 707's and its performance characteristics would appear closely to resemble those of the latest707 variants. Its size however, with gross weight more thantwice the 707, will provide a considerable impact on theairport; runway, taxyway and apron LCNs, taxyway curves, clearance limits etc., all need to be revised to establ ish whether mod ifica t ions need to be car r ied ou t be fo rethe first one arrives. The SST is another matter though, andwhilst the major ATC problems are likely to exist in theen-route phase, the following aspects need to be considered in the airport environment:

— High approach speeds mean that greater spacing mustbe given between the SST and aircraft of lower (conventional) performance. One early simulation at theAir Traffic Control Experimental Unit established thatone landing was lost for every SST on approach.

— A t w h a t m i n i m u m d i s t a n c e f r o m t o u c h d o w n c a n o n

overshoot be executed? Runway capacity may need tobe reduced to "ensure" a landing.

— If any special minimum noise procedures on arrival ordeparture become necessary, this would also affect runway capacity.— Capability of executing turns on the ground when following a centre line taxyway system, with the flightdeck a very considerable distance ahead of the mainwheels — particularly in poor visibility.

V\^hen the SST arrives the airport will hove had perhaps

1 7

two or three years experience of 747 operations andshould by then be able to take both SST and the Airbus ini t s s t r i d e .

It seems likely that the next mutual concern will beabout the civil version of the Lockheed C5 and SuperJumbos .

Inter-Airport Helicopter ServiceThe New York and Los Angeles areas currently operate

inter-airport helicopter services with connections to "city-terminals", and it is possible that scheduled services willbe introduced at some time in the future in the LonaonA r e a .

At the moment, in the United Kingdom terminal areas,helicopter movements ore light and present no real pro-blem.s. If regular thirty minute shuttle services are to beplanned between Heathrow, Gatwick the "No. 3" andLondon, the establishment of on acceptable route systemwill depend on the location of the airports in respect ofthe city, the proximity to densely populated areas, theseparation from each airport's arrival and departuretracks, the method of navigation, the ability to operateunder IFR, and finally the capability of integrating increased helicopter movements with fixed wing operations without undue effect on airport capacity. These are some of theaspects that need to be considered in detail before such asystem could be introduced.

AT C F a c i l i t i e s

Having considered some of the ATC aspects of airportcapability and requirements pertinent to present and forecast operations, aids and runway utilisation, perhaps it isappropriate for us to reflect upon the provision of facilitiesto enable the controller to effect his task. It must be remembered that the number one principle is that at alltimes the relationship between safety and expedition mustbe maintained. It is now generally recognised that ATCexperience can provide a significant contribution to airport design and layout, but co-operation should be reciprocal. Airport design authorities should ensure that ATCis accommodated where it can provide the most efficientservice, compatible with the airport layout of runways,taxyways, aircraft stands, foreseeable movement ratesand essential equipment. The two major ATC services associated with an airport are Approach Control and Aerodrome Control, both self explanatory terms, and Aerodrome Control may be further divided into two functions— A i r C o n t r o l a n d G r o u n d M o v e m e n t C o n t r o l .

Aerodrome Control should be sited to provide a clearunimpeded view of all traffic patterns for efficient visualcontrol of the primary runways and the subsidiaries, basedon the premise that at most airports, for a very high percentage of the year, traffic problem and conflictions onthe manoeuvring area can be resolved by visual referencewithout the need to interpret displays. Thought should begiven to the number and configuration of the runways,their dimensions, turn offs and holding areas, taxywaysand the airport terminal area and apron layout. Oneshould not lose sight of long term requirements and mustallow a space contingency within the Aerodrome ControlRoom to house equipment for automatic data processinginputs, electronic data displays and whatever the allweather operation requirements will be. Operationaldesks, consoles and display equipment and the desk con

figuration should be tailored for the specific operationsand physical characteristics of each individual airport. TheAir Controller wants an unimpeded view of the approachand departure paths and the length of the runways forwhich he is responsible. In the case of an airport havinga parallel runway layout with the Control Tower buildingin the middle of the runway layout, and where there arehigh movement rates, it may be necessary to effect a division of the Air Controller's responsibility between twocontrollers to achieve and maintain high runway utilisation. Regardless of whether parallel landings and depar-tures or a dual runway mode is in operation the practicaldivision is for each controller to have jurisdiction over oneof the parallel runways. The controllers should be locatedclose enough for rapid physical liaison without obstructingthe view of their respective areas of responsibility — mostcommunication systems do not have the capacity to alertas quickly as a sharp tap on the arm. Where a separateGMC function is provided the same requirement for anunimpeded view exists, in this case through 360°. Thelocation for the Aerodrome Control building and theoperating desk and equipment layout should be the resultof full consultation between the airport design authority,ATC, the technical furniture designer and those responsible for the installation and maintenance of the operational equipment.

Reverting to the "Island Site" with the provision of twoAir Controllers and GMC, a conflict of interests for anunimpeded view exists. If we accept the principle that theMir Controllers should be positioned for close liaison, thiscan be effected by locating the controllers facing theirrespective areas of control side by side but looking inopposite directions, affectionately known as a "love seat".Ideally this should be centrally placed above floor level toprevent cut-off from the sills and to permit movementaround the room and withdrawal of equipment for maintenance. If we assume that the Air and Ground MovementControllers with their closely related functions, are to beaccommodated in the same room to effect liaison and toshorten communication links, a compromise can be madewhereby the Ground Movement Controller — or Controllers — are so placed that it will be necessary to standto view that segment of the taxyway complex in line withthe Air Controllers but will not impede the Air Controllersview of the runways, and approach and departure paths.This is the type of problem one encounters when attempting to decide the most efficient layout for an Airport AirTraffic ^^ontrol Unit. It is too easy to fall into the trap ofsuggesting the use of CCTV to cover "blind spots" or evenASMI. It is not an economically sound practice to runASMI twenty-four hours a day throughout the year and itis difficult to monitor a radar tube or CCTV picture properly and maintain visual surveillance of aircraft andvehic les.

Nothing has been said up to this point about the location and design of Approach Control. Approach Control,like Terminal Area Air Traffic Control methods is basedfor the most part on a radar concept. There is doubt insome quarters whether this reliance on radar vectoring,with the heavy communication work load between controller and pilot is the most efficient method for control in theTMA and Approach phases. The TMA and airport navigation capability perhaps should play a greater part, withradar performing a predominently monitoring function.

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Approach Control is responsible for the critical approach phase, and in some circumstances the initial departure phase of on aircraft's flight and because of its radarenvironment has no requirement for visual reference tothe airport manoeuvring area or the runway approach anddeparture path. Its location is therefore, not so critical asthat of Aerodrome Control but the Aerodrome and Approach Control functions are very closely linked and traditionally are generally located within reasonable distanceof each other. This effectively achieves short communication links, and permits the controllers to alternate betweenAerodrome and Approach positions without incurring administrative and economic penalties. Very briefly the layout in Approach Control will vary according to the demands of the airport it is serving but should follow insequence the phases of the aircraft's flight path from theposition of transfer from the TMA control until establishedon final approach and transferred to Aerodrome Control.

Inevitably reference must be made to ATC instrumentation and displays, the Guild's paper on ATC Displayspresented at the 1966 Convention emphasised that withany equipment the use of the information available willonly be as good as the quality of the controllers using theequipment. Controller calibre and equipment quality aretwo distinct items but one is obviously complementary tothe other and the two together will determine any flightsafety factor within on Air Traffic Control system. Thedegree of equipment and displays will have to be economically justified with regard to the airport configurationand the density of aircraft movements. In short the systemshould be geared to provide the airport with the ability toaccept and dispatch aircraft within a standard of rulesto achieve maximum runway utilisation. The requirementscan range from a one man band Approach-cum-RadarController to a complete dual system of radar directors forthe intermediate and final approach sequencing phasesfeeding parallel runways independently and simultaneously, with further radar controllers for general aviation andspecial VFR traffic added for good measure; and masterminding the traffic flow, spacing of landing aircraft inrelation to departures and integrating General Aviationinto a predominently air carrier environment, a co-ordino-tor, flow manager, crew chief, call him what you will buta key man nevertheless.

Aerodrome Control and Approach Control capabilitymust be matched, and efficient data links established.Nothing con be more frustrating or designed to decreaserunway utilisation than baulked landings due to insufficient separation on final approach or wasted runway timedue to unnecessarily extended separation. The most essential displays and instruments must be, as far as is possible,directly in front of or near to the hand of the controller.It has been said before: equipment and displays should bedesigned and located to present information to the controller in such a manner that it is readily assimilated, requiring the minimum interpretation or physical effort andleaving the controller free to arrive as quickly as possibleat an executive or planning decision. It should be theiT^inimum amount of data consistent with the ability toca r ry ou t on ATC func t i on and de tec t unsa fe s i t ua t i ons .The controller should be able to acquire further information quickly, this will range from physical contact with anadjacent controller to more advanced technologies withrapid address and retrieval of data.

In addition to air-ground communication. ApproachControl will require radar equipment, or whatever supersedes it, to sequence aircraft and a means to identify theaircraft. Radar is used here as a generic term and includesprimary, processed, labelled and bright displays. Data andcommunication links between Approach and parent ATCCand Aerodrome Control ore essential. Displays should include amongst other things information on all traffic coming under their control, weather information and facilitiess t a t e .

Where precision approach radar is provided the controller will want displayed the next aircraft identity, continuous descent glide path checks when there is no elevation data, obstacle clearance limits, clear to land indicator, RVR and wind speed and direction.

Aerodrome Control, which includes Air and GroundMovement Control, require equipment to communicatewith aircraft and vehicles on the manoeuvring area. Theamount of "natter'' in the U. K. with regard to servicevehicles on the manoeuvring area is overdue for reviewand revision of procedures. The facility to check aircraftposition on final approach or during the departure phasecan be supplied by equipment such as the distance fromtouchdown indicator and/or a SRE using Bright Displaytechniques. By the use of Direct View Storage Tube techniques the DFTI is capable of being viewed in open daylight. This is an essential specification for any radar to beviewed in Aerodrome Control. In restricted visibility cond i t ions on A i rfie ld Sur face Movement Ind ica to r w i l l ass is tin the direct ion of aircraft on the surface but a means ofincorporating identification is on outstanding need. TheGuild has, over the years, pursued a policy for the widerintroduction of Bright Display techniques and we wouldvery much like to see the development of a daylight viewing display for the type of ASMI equipment installed atH e a t h r o w.

Other requirements for Aerodrome Control are thedisplay of data for identification of departing aircraft,landing sequence of arriving aircraft, allocated parkingarea, meteorological data, a compact back indicating Runway and Approach Lighting Panel, and a taxyway routeselection system, preferably miniaturised with no delaybetween selection and activating in the field and protection against the selection of conflicting routes.

A u t o m a t i o nThe speeds and numbers of aircraft using the United

Kingdom Airports have been steadily increasing and willcontinue to do so, particularly at the major internationalfields. It is recognised that the basically manual systememployed is likely to impose limitations on the processingand transfer of essential data and introduce what couldwell become a high potential for human error. A greatdeal has been written and talked about the use of highspeed computers for collecting, processing, transferringand automatically displaying flight plan and profile datato provide a safe and effective ATC system. It is refreshingthat some of this energy and expertise has now turnedtowards Terminal Area and airport problems. These cannot be isolated and arrival and departure capability is asignificant factor in the overall system. The ability of theairport to maintain, or not, its acceptance and departurerate can have a marked effect on the en-route phase. Theintroduction of modern electronic data processing, transfer and display techniques at airports maintaining highmovement rates wi l l re l ieve the contro l ler of some of the

routine tasks and communication load, leaving more timeto arrive at executive or planning decisions. We must,however, be carefu l not to use a steam hammer to cracka nut, and use a computer as an end in itself. Consideration must be given to the demands of the particular airport and its potential. At fields with relatively low movement rates sophisticated techniques could well slow downthe processes, whereas a sharp crack on part of the anatomy or a well directed finger, dirty or otherwise, couldwell be the most efficient data link. Perhaps this story ispertinent "A British Diagnostician was touring a gleamingnew hospital in the States to see the practical applicationof computers in diagnosis. Each patient was given a datasheet on which every detail of his condition was listed. Thecomputer then diagnosed the complaint. The visitor wasduly impressed but asked how the trainees coped whenthey left the hospital and set up practice in small townand village hospitals where there were no computers toaid diagnosis? What in fact happened to the patients? Theanswer was as positive as it was resigned. "Ah, they diedoctor, they die." Getting back to automation and airtrafFic control at the airport a developm.ent we look forward to is the computer assisted approach sequencing ofaircraft to the landing runway. The rational spacing ofaircraft at touchdown will achieve a high degree of runway utilisation. It is envisaged that the computed tracksand speeds to be flown to make good the desired separation at touchdown can be displayed either by an alphanumeric label on the radar screen with symbols for anycomputed turn onto another leg or by an electronic display with the callsigns tabularly displayed in sequencewith other pertinent information such as type, adjustedairspeed, track, applied separation and runway; this lastitem is particularly significant when the parallel landingand departure mode is in operation. For Radar Directorsthe labelled display would be a better choice because itrequires no correlation of the radar picture and data display. It can also be readily assessed if the aircraft has leftthe computed leg and if necessary adjusted for up-dating.An electronic tabular display of the landing sequencecould be displayed to the Air Controller together withtype, runway and spacing. This would effectively form adata link between the Approach Radar Director and theAir Controller. To further the process where there is aseparate ground movement control unit, the callsign ofarriving aircraft could be displayed on an EDD to theGround Movement Controller together with the aircraftstand designator as allocated by the Airport Authority.The problems posed for processing an approach sequenceonto parallel runways from more than one holding stockor gate while departures from the same runway are inoperation present an ideal set of factors for using a digitalcomputer to assess the control strategy. The holding areasor approach paths to the commencement of approachsequencing to the runway should be treated as a joint

queue for both runways and runway assignment computedto permit departures from both runways. It is likely thatthe computer could assess a dual runway operation as themore efficient strategy for a particular spread of departing and arriving traffic. The use of a multi-track navigational system for Area and TMA, based on a pictorialcockpit presentation of an area navigational capabilityof given accuracy limits could be integrated into such asystem to meet the demand for increased airport movem e n t s .

The assignment of a runway for departing traffic is notso flexible since, for example, a northbound aircraft departing from a south runway sterilises the take-off path ofthe north runway until it is clear of that path.

We consider the programme should be extended toinclude part of the ground movement environment; it hasparticular significance at Heathrow. When parallel landings are taking place a closely knitted network of taxyingtraffic could evolve around the Central Terminal Area ifaircraft landing on the north runway are proceeding toaircraft stands to the south of the Control Terminal Areaand v ice-versa.

There are many ways in which a computer can be usedto effect data transfer but there is one other field in whicha high speed computer could assume a significant role;the automatic route selection for ground taxyway routeing.Very briefly the requirement is for busy airports with acomplex taxyway system and multi-runway landing anddeparture procedures, to have the capability of requesting from a computer store the most expeditious route fromthe point of leaving the runway to the aircraft stand orfrom the stand to take-off point, graphically displaying theroute with conflictions indicated, automatically selectingthe appropriate lighting or taxyway guidance system andresolving or protecting against conflictions at intersections.

C o n c l u s i o nTo conclude we must stress the futility of ignoring the

interests of other airport agencies; recriminations andaccusations will not help to solve the type of airport saturation crisis which affected the New York Area this summer. The lessons to be learnt are there for all to see,particularly their delay in selecting a fourth airport. Atleast one of their major problems does not exist atHeathrow, where for some years the hourly movementrates have been stated by ATC, and then filled by an efficient Airline Operators Scheduling Committee.

However the overall problems could perhaps best bemet in this country by the formation of a "Board" — ofworkable size — incorporating all interested parties suchas Airport and Local Authorities, Airline Operators, theNATCS and independent ATC, and surface transport organisation. The purpose of the Board would be to develop aNational Airport plan to provide for the present requirements of air transport and general aviation in the U. K.

fotgQf March 19698th Annual IFATCA Conference

Belgrade, Yugoslavia

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ATC and the Supersonic TransportPresented by the U. K. Guild of AirTra f fic Con t ro l O ffice rs a t t he Gu i l d ' sAnnual Convention, Bournemouth 1968.

It was not without some misgivings that the Guildadopted as a theme for this Convention "ATC and theSupersonic Transport", for it is recognised that there aremany experts in this field, and probably in this audience,some of whom may disagree with each other on certainaspects of the subject. However, on one thing, all mustagree: that air traffic control systems throughout the worldmust be sufficiently flexible to meet the requirements ofall operators and that standardisation of operating procedures and facilities should be vigorously pursued in orderto facilitate transfer of control responsibility, co-ordination of traffic and the preservation of safe separation atall times.

This may seem to be a strange introduction to the subject but, OS each new aircraft with more advanced facilities and capabilities comes into operational service, thecry is heard that it cannot be integrated into the existingATC system and therefore new procedures and facilitiesmust be provided to ensure its safe and expeditious handling. This, of course, might result in specialist and prioritytreatment being provided for those aircraft able to comply with the new requirements and a second class servicefor those unable to comply. Is a two-tier ATC servicereally what is wanted? The Guild does not think so. Aircraft operational performances have increased remarkably since World War II, and have strained almost tobreaking point the resources of the air traffic controlorganisations of the world which never quite manage tokeep pace with the rate of development of new aircraft.The rate of progression from sub-sonic to supersonic performance in the case of jet transports con be expressed interms of speed as being from Mach 0.8 to Mach 2.2, astaggering increase which must inevitably result in a careful reappraisal of existing ATC systems to determine theirweaknesses and to ensure that steps are taken in time toimprove, and where necessary change, facilities and systems to enable the air traffic control organisations to integrate these new generation aircraft with those at presentin operation.

This paper is concerned with supersonic transportaircraft and the impact of their introduction on air trafficcontrol. In this connection, a great deal of work has already been done both in the UK and the USA, and thispaper is based largely on UK and USA dynamic ATCsimulation results so for, plus what might be called "Guildcrystal-ball gazing". In addition, through the medium ofthe Guild's military members, operational experience inthe handling of military supersonic aircraft has beenmade available and, whilst it is appreciated that militarysupersonic aircraft operate in a virtually unrestricted environment and are concerned with achieving maximumoperational performance and flexibility rather than economy of operation, nevertheless such experience may well

indicate some of the problem areas to which ATC attention should be directed. For example:

a) In military experience, the weather factor on the climbis not significant, a combination of meteorological forecast and radar CRT "look-see" having proved adequatebefore the commencement of climb.

b) Precise positional and time estimates are essential topermit straight line descent to Terminal Area FinalApproach for stroight-in landing, delays and decisionsregarding diversion being determined before any descent is commenced.

c) Radar surveillaince is required throughoutsubsonic andtransonic stages into the supersonic profile and similarly on recovery.

d) Speed control of military supersonic aircraft on recovery has been found to be unacceptable.In considering the applicability of this practical ex

perience to the supersonic transport aircraft, due accountmust be taken of the different environment in which it willbe operating, i. e. integrated with sub-sonic aircraft ofwidely differing performances in busy Terminal ControlAreas, of the different roles of the civil and military aircraft and of the significantly greater stresses acceptableto both airframe and occupants in the case of militarya i r c r a f t .

By 1971, the frst Concorde aircraft are likely to be onthe air routes. The Boeing 2707 is forecast for regularservice in 1975 and a Russian built SST with characteristicssimilar to the Concorde will concern ATC in WesternEurope during the some time scale. The options currentlyannounced indicate that, for Concorde and Boeing SSTs,a total of 133 aircraft have already been ordered. Themajority of these, during the first few years' operation,will be utilised on North Atlantic services. The need for ahigh and economic utilisation of each individual aircraft,and the knowledge that the options are far from complete, makes it reasonable to assume that by 1976/77about 150 SST aircraft will be operating daily in theWestern Europe airspace. This will give a total of approximately 300 SST departure and arrival movements per day.

Routes and Separation StandardsThe movement of supersonic aircraft presents certain

problems to ATC, and it has been necessary to suggestdiscrete routes and increased separation standards evenfor a single movement. The operation of larger numbersnecessitates a complete re-appraisal of current ATC techniques and procedures. It has to be recognised that theSST has distinct and unique requirements for the variousphases of its flight, particularly those concerned with the

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climb and descent to and from the cruising levels involving subsonic, transonic and supersonic speeds and perf o r m a n c e s .

A typical SST FlightIf one now looks at a typical flight, starting at the

ramp, the first problem is encountered. lATA have saidthat a stated departure time is required for the SST whichmust be made good within plus or minus five minutes. Thiswill clearly cause problems to ATC who are currently quiteunable to predict precisely what the traffic situation willbe in the next fi f teen minutes. I t is d i fficu l t therefore forATC to assess at this stage how the lATA requirement canbe implemented unless a high degree of preference isgiven to the SST and, even if this is accepted, then taxi-ways and holding areas will have to be wide enough toallow SST aircraft to by-pass other aircraft.

Assuming that our SST aircraft has moved onto thetake-off runway, it will be necessary to provide a clearance to climb, without restriction, to FL 260 or thereabouts.This is difficult to arrange even now during periods of hightraffic density, and later it will undoubtedly become amajor problem.

Af ter take-off the a i rcraf t wi l l have to c l imb wi th in the

airways system through conventional traffic with all theattendant problems imposed by the current width of airways of 10 NM — this will undoubtedly give rise to restrictions to the SST. One other factor which may introducerestrictions on SST operations at this stage, is that concerning the sonic boom. Despite the intensive experimentscarried out, so far mainly in the USA, by subjecting populated areas to sonic boom over-pressures, no clear indication has emerged of what is likely to be an acceptablelevel of noise from SSTs. Further tests will undoubtedlyhave to be made with an aircraft of at least Concordedimensions in order to gain conclusive evidence which willlead to a sound basis for determining what, if any, restrictions have eventually to be applied to the subsonic climbof the SST. Due perhaps to the inconclusive nature ofresearch to date, no firm policy has yet been stated by theUnited Kingdom on whether the boom can be permittedover land. In considering the routeing of the SST for itstransonic climb, therefore, it is assumed for the purposeof this hypothetical flight that the boom must be projectedo v e r t h e s e a .

Track SystemsThe SST wi l l w ish to commence i ts t ranson ic c l imb to

cruise/climb conditions as soon as possible, and then takeup its North Atlantic track. A standardised track system isrequired with alternative tracks to take account of adverseweather conditions, and these tracks must be promulgatedto all interested ATC and other operational agencies. Itis essential that aircraft on these routes are afforded theprotection of controlled airspace with no upper limit.Radar cover is considered to be essential for at least 180nautical miles from the furthest point at which the transonic climb will normally commence.

R o u t e S t r u c t u r e

The simple route structure for the early days of the Concorde operations requires only single west- and eastbound

tracks, and it will be possible to ensure — by liaison between Paris and London — that the westbound track structure will receive aircraft at intervals appropriate to thelongitudinal separation standards. It should be noted,however, that the use of a cruise/climb technique wouldseverely restrict the capacity of each track in the routestructure, due to the inability to utilise several separateflight levels simultaneously. As the number of supersonicaircraft increase, therefore, a greater number of routeswill be required, and the route structure will become morecomplicated.

For example, an increase in the number of departureairports on the Continent will prohibit any simple form offlow control liaison, and aircraft may have to be delayeden route in order to enter the NAT tracks at the appropriate times. This may be achieved without any greateconomic penalty to the operators by requiring the aircraftto remain at subsonic speeds for a given number ofminutes. However, it might result in westbound Concordesgoing out of radar coverage whilst still at subsonic levelsand thus being required to climb using procedural separation standards. I t seems doubtful that th is s i tuat ion wouldbe either acceptable or practicable. As numbers of supersonic aircraft increase, so the numbers of NAT tracks mustbe increased. These will inevitably become further awayfrom the great circle tracks, and may therefore be outsidethe coastal radar coverage for the initial climb or finaldescent phases of flight. For increased coverage, therefore, it may be necessary to provide an ocean radar platform. Additionally, there may be a requirement for stepc l imbs and Mach. number l im i ta t ions in o rder to con ta inthe traffic safely. Once the supersonic aircraft is at itscruising level, ATCproblems diminish, but unknown factors(for example solar flare radiation, CAT, or loss of oneengine) may require the immediate descent of the aircraftto levels occupied by subsonic traffic, which would, ofcourse, present considerable problems to ATC. But however interesting it may be to speculate on these things,time does not, unfortunately, permit further discussion ina paper of this length.

When decisions on SST routes have been taken, theproblems of R/T communication and radar coverage willalso have to be reviewed. The points of handover betweenvarious authorities will have to be agreed — certainly thecurrent short route segments with frequent handovers willhave to be modified or abandoned, since already thespeed of aircraft has overtaken the speed of groundliaison and communications. It will be necessary, therefore, to arrange for the projection of information wellahead of the aircraft's arrival at a given point, and itwill probably be necessary also to have a central authority for the co-ordination of all traffic in the critical areaof the UK south-western approaches.

The abandonment of short route segments and therequirement for increased sector lengths means that RadarControllers will have considerable areas under their surveillance. It will be necessary therefore to decide on theoptimum size of radar displays, the scale and the area tobe controlled by a Radar Controller, and the method ofdisplaying traffic data.When one realises that on a 16-inchradar display representing a 200 nautical miles radius, fivenautical miles separation is represented by one fifth of aninch, it is evident that one of the problems to be investigated will be the ability of Controllers to work down to radarresolutions of this order. Radar beam width is relevant to

2 2

this problem and will determine, to some extent, the radarseparations which can be applied in practice, especiallyat long range.

With regard to inbound flights, some 120 nautical milesfrom landfall the SST will require descent to become subsonic before reaching land. Here again, provided adequate radar coverage can be given, this requirement canprobably be met by Air Traffic Control in a low densityenvironment, as this presents a less critical problem anda less sensitive phase of the flight than that concernedwith the t ransonic c l imb.

Integration of SST and Subsonic AircraftIt is not anticipated that any new problems will be

encountered in the integration of SSTs, once they are subsonic, into the general pattern of airways traffic provided,as previously mentioned, the width of current airways isincreased. Difficulties will arise however if and whendiversions are required, the earlier decisions of this naturecan be made, the more efficient service the Air TrafficControl authorities can provide, the more economical willbe the operation of the SST aircraft concerned. For thelanding phase, ATC seems to be in a somewhat "greyarea" as far as the knowledge of aircraft requirement isconcerned. Because of congestion in busy terminal areas(e.g. 2V2-hour wait recently at Kennedy) and the highrunway utilisation necessary at major airports in order tohandle the ever increasing traffic. Air Traffic Control willbe vitally concerned with any special arrangements orrequirements necessary to accommodate supersonic transport aircraft. The difference in the supersonic transportapproach speed and that of the slowest conventional aircraft will be extremely significant, and this differential willcomplicate ATC sequencing problems. Terminal Area control must therefore always be flexible enough to permitSST integration with conventional aircraft. It must also beclearly understood that ATC cannot guarantee priorityapproaches for all inbound SSTs, as the efficiency of anyATC system depends on the ability of all airspace users tofollow the same procedures. Once on the runway, the SSTwill be required to clear it at speeds no less than thoseapplicable to current types, if delays to subsequent trafficare to be avoided.

W e a t h e r E f f e c t

Many theories have been presented (some of themquite alarming) concerning the impact ofweather upon theSST in the critical phases of transonic climb and descent,and mention has already been made of military experience in this area. In UK latitudes it is unlikely that precipitation or turbulence, associated with Cu Nim, will beencountered above PL 400; the effect of weather on SSTshould be confined mainly to the transonic climb untilabove FL 400, and to a lesser extent to the transonic descent. Alternative solutions may lie in the use of airbornedetection equipment and ground based radar, but, in thecase of the latter, the following questions arise:

1. Who operates it and what presentation is required?2. Will the particular radar see all the weather or only

certain selected parts of it?3. Will the pilot of a SST be prepared to accept delayed

climb or rerouteing on weather radar advice only, and

what will be the responsibility of the controllers in thisrespect?

The problem is therefore a joint pilot/ATC one. On theone hand pilots will wish to monitor their flight throughthe use of airborne radar; on the other hand ATC shouldequally be in a position to have continual sight of theweather picture, so far as it can reasonably and realistically be portrayed on radar. This combination of "weatherwatch" will complement the en-route forecasting service.The Guild would therefore like to see a system introducedby which Radar Controllers would have immediate refe rence to radar -der ived weather in fo rmat ion ava i lab le a ttheir operating positions. Whatever decisions are taken inthis respect, however, the Guild is convinced that pilots ofsupersonic transport aircraft will not wish to commencetranson ic c l imb un less there is some firm assurance tha ttheir flight path is clear of unsuitable weather.

Navigational RequirementsIt is clear that, for reasons which will become apparent

later in this paper, ATC considerations will have a majoreffect on the operational requirements for SST navigational capability.

The principal factors governing these navigational requirements may be stated as follows:

Flexibility, Accuracy, Reliability, Profile guidance.Common reference. Data display. Automation.

From the preceding it is possible to draw some firmconclusions as to the type of system needed. The term"system" is used deliberately since navigational functionswill need to be performed by a combination of navigational aids operating through a digital computer, out-putting data to a comprehensive flight deck navigationaldisplay and to the auto pilot. Flexibility can be achievedthrough the medium of an area navigational system, derived either from a ground radiated pattern of a true areacoverage type, or from "self-contained" data computed inthe aircraft. In the latter event, the information will requireto be updated periodically by an external reference aid.The accuracy requirement will be dictated by the horizontal separation standards to be employed, which inturn are a function of the ATC system capacity and operating economy.

Reliability is a pre-requisite, again in terms of separation standards, since their safe adherence depends to alarge extent on the elimination of gross errors. As an illustration of the combined roles played by accuracy andreliability in their application to separation standards, alateral separation of 60 nautical miles between tracks inthe North Atlantic will require an across-track error having a standard deviation of approximately 8 nauticalmiles, with a capability of maintaining track within 30nautical miles for 99.95% of the time. Precise profile guidance is dictated by the need to conform to the air trafficcontrol clearances issued for the flight and to any changesto profile necessitated either by reclearances or by meteorological conditions. Additionally, noise and sonic boomconsiderations may impose a strict limitation on the areaover which transition to supersonic flight is permitted. Precise 3-dimensional data is therefore essent ia l . Concerninga common reference, it is obvious that for a high proportion of the supersonic phase of flight, certainly acrossthe North Atlantic, the supersonic aircraft will be outside

2 3

radar coverage and therefore outside one of the commonframes of reference used by air traffic control to preserveseparation. It is therefore essential that any navigationaldevice used as a basis for a horizontal separation musthave a common reference, both to absolute ground posit i o n a n d t i m e , t o m i n i m i s e t h e a c c u m u l a t i o n o f r a n d o merrors between the representation of different aircraftpos i t ions .

The requirements for data display and automation ofthe navigational functions can be considered in combination since essentially both aspects are most pertinent tothe flight crew; also both have a consequential effect uponATC. Cockpit pictorial displays are currently gaining wideacceptance and these should be associated with a distance, time-to-go and required track to any desired point,plus along/across track readout. Associated with thesedisplays should be an autocoupling facility on any seriesof predetermined tracks with a facility to over-ride oramend the preselected tracks to accord with changes inair traffic control routeing instructions. The ATC purposein both cases is to achieve minimum flight error whilstadhering to the track and profile. Automation of the navigational functions is required in order to provide moretime for concentration upon operational (including airtraffic control) aspects of flight management. Additionally,automation by digital computer will provide for the transmission of aircraft positional data by an automatic digitalair/ground data link to a central ATC data processor.

There are other areas in which ATC will have to relymore on automation and computer aid and less on thetraditional empirical approach. Apart from the requirements for en-route control the ATCO needs help to tellhim the optimum time at which to turn an aircraft in anapproach sequence and the amount of turn necessary.Work has already commenced in this field, and it is hopedbefore long that a suitable approach control aid will become available. (We shall certainly need one!) Furtherout from the airport, some sixty or seventy miles away,there is a requirement for speed control and sequencingto start — this will have to be done initially by "guestima-t ion " and the ove rworked Con t ro l l e r w i l l we lcome any relief from this difficult chore, but it is hoped that in thenot-too-distant future he will be able to obtain from acomputer the speed control requirements and the optimumsequencing for any circumstances.

In simulation exercises concerning supersonic transportaircraft combined with subsonics and military traffic, ithas been found necessary to devise special techniques inorder that the Control Officer may have sufficient warning of the intention of the pilot of the SST to carry out aparticular manoeuvre. Equally, the air traffic control officermust create sufficient lead time to warn the pilot of theSST of a requirement to carry out any m.anoeuvre necessary for ATC reasons. It will clearly be necessary to specify adequate lead times in order to enable SSTs to level offat specified levels.

Radar CoverageThe main considerations regarding separation stan

dards applicable particularly and peculiarly to the SST,require intensive study before a satisfactory solution canevolve. In test separations during simulation, 4000 ft. vertical and 10 nautical miles spacing on radar have beenapplied, but these may not necessarily be the optimum

requirement. It is certainly our view that a much moreexpeditious ATC handling for SST is possible where parallel one-way tracks can be provided, but if even as i n g l e S S T h a s t o b e s e p a r a t e d f r o m t h es u b s o n i c t r a f fi c fl o w , t h e w h o l e t r a f fi cs i t u a t i o n m u s t b e u n d e r c o n s t a n t r a d a rs u r v e i l l a n c e d u r i n g t h e c r i t i c a l c l i m bf r o m s u b s o n i c t h r o u g h t r a n s o n i c t o t h esupersonic phase. In addition to the suggestedparallel one-way tracks, consideration should be given tothe provision of ultra-high sectors. These will be sectorsabove the normal subsonic jet operating or cruising levelsand will possibly extend from 40,000 upwards. Althoughwe mentioned previously the requirements for navigational equipment for SST, air traffic control are equally concerned that protection for these aircraft by all means atour disposal can and must be afforded. In the early 70sthe primary instrument for this purpose will be the extended use of radar and an increase in radar coverage. This,coupled with the intensive use of secondary radar, whichcan be utilised to its maximum efficiency when the carriage of transponders is made mandatory for all aircraft,should considerably assist ATC in controlling and protecting the supersonic aircraft.

Civil/Military Co-OrdinatlonThe UK authorities concerned with planning the ATC

system for supersonic aircraft operations have been considering for some time how best to co-ordinate, in theairspace available, movements of civil and military aircraft capable of following a flight plan with those movements of military aircraft on operational missions whichare not answerable to such a plan. Hitherto, these twotypes of traffic have been controlled by different authorities and experience has shown that this is not an entirelysatisfactory state of affairs.

Military and civil co-ordination in the upper airspacehas, however, already been developed to a high degree ofefficiency at the Joint Air Traffic Control Radar Units, andthe future ATC system (Linesman/Mediator) planned forthe United Kingdom, will create an integrated civil/military organisation designed to cater for the needs of allusers of the airspace in which air traffic services will beprovided.

Mutual appreciation of each other's problems in ajoint planning organisation, which was the intention behind the formation of NATCS, must provide the answer toconflicting requirements to ensure that SST operationswill be afforded the same high standard of ATC protection that operators have come to expect of the NationalAir Traffic Control Services of the United Kingdom inrespect of current operations.

Automation of Navigational Facilitiesfor ATC and Pi lots

So far m this paper the Guild has stressed the importance of radar as the Controller's primary tool to solve theimmediate ATC problems of threading individual SSTs insmall numbers through the present main flow of subsonictraffic. It is the Guild's view that this is a short-term expedient which will break down when the density of SSTt r a f fi c i n c r e a s e s .

Let us consider an instantaneous forecast traffic situation in the UK south-western approaches on a day in 1974

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when tracks are south-about. In such an environment, using present control techniques, it seems likely that thelimitation on system capacity will be the number of aircraft which each individual Controller will safely be ableto monitor for the purpose of predicting and avoidingpossible future conflict situations, and the number of individual controllers between whom responsibility for such acomplex situation could be efficiently sub-divided, without creating impossible liaison problems.

In this environment, and wherever else over the face ofthe earth two or more SSTs may wish to accelerate, decelerate, cruise, climb or descend, in the same area at thesame time, the real ATC requirement is for informationon position, altitude and intention from all aircraft, tospecified tolerances of accuracy in relation to a commonframe of reference, at specified intervals of time, togetherwith 0 system for collecting and processing this information for purposes of conflict detection and resolution.

Since it is inconceivable that the long-term solutionwill be to carpet the earth, and particularly the oceans,with extended secondary radar coverage, it is absolutelyessential that the aircraft's novigotionol system must beutilised to provide the required data, and it is primarilyfor th is reason that i t is the Gui ld 's v iew that i t is theseATC requirements and not the comparatively simple taskof getting from A to B which dictate the accuracy andnavigational capability required by SSTs. In high densityareas of operation, ATC will require computer processingof this moss of incoming four-dimensional data to plan an

efficient traffic flow and to detect and display specific confl i c t s i t u a t i o n s f o r C o n t r o l l e r i n t e r v e n t i o n . I n t h e l o w e r

density and en-route environments, there is a functionalrequirement for designated pairs of aircraft to be able toexchange navigational information, for the purposes ofmaintaining their own separation in relation to each otherduring specified periods, if large and possibly uneconomicseparation minima are not to be imposed by ATC in orderto prevent the possibility of conflict outside areas of available radar coverage.

To sum up, therefore, it is the Guild's view that ATCwill not be able to offer safe, orderly and expeditiousservice to SSTs and subsonic aircraft unless:

a) in the short term, adequate radar coverage and sufficient controlled airspace is available, even for an individual SST which requires to climb or descend throughexisting subsonic traffic, and

b) in the longer term, all SSTs and long-distance subsonictraffic flying the same route sectors ore equipped withan airborne navigational capability to fly specifiedtracks and profiles, to specified accuracy tolerances, inrelation to a common frame of reference, with thecapability to communicate this navigational information to each other and to ATC Centres, and that theseCentres are equipped to process this information forpurposes of conflict detection and resolution. Bearingin mind the gap between concept and implementation,the longer term in this context means yesterday!

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32331

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A i r Tra f fic Con t ro land the Supersonic Transport

Presented by Captain A. G. Payne* atthe Guild's Annual Convention, Bournem o u t h 1 9 6 8 .

Mr. Chairman, Ladies and Gentlemen,

1 am here to talk to you about the SST and its likelyimpact upon ATC, that is from the pilot's point of view.

Although we all have a fair idea where the problemareas are likely to lie, until a considerable number ofhours have been spent on flight deck and ATC workloadstudies with Concorde prototype in flight, it is unlikelythat any firm conclusions on new problems will emerge.

We do, however, even in the subsonic age, have certain problems which concern the Air Traffic Controller andthe pilot. It is unlikely that the introduction of the SST,combined with a new generation of subsonic jets, wouldmoke these problems any easier to live with. I am sure thatthe reverse would be true. It is for this reason that I hopeno effort or expense will be spared to investigate the present problems and find the answers to them now. If this isnot done, then I fear that the whole situation will snowballand may end in chaos, as evidenced by the state of affairswhich have existed over the New York Terminal Areas inr e c e n t m o n t h s .

What are the problems? The one which immediatelysprings to mind is that of maintaining verbal communication between the controller and the pilot.

My first experience of civil ATC was back in 1944 whenI was on flying boots. The controller, in his pinnace, andthe pilot, in his flying boot, maintained communications bymeans of loud hoilers, oldis lamps, semaphore and occasionally, when the situation called for it, the controllerwould fire a rocket. Later on we were ftted with VHP R/Tand we then thought what a marvellous innovation, andindeed, it was compared with our flags and lamps. As itsuses have developed, however, and with the phenomenalgrowth of air traffic over the lost 25 years, one could saythat VHP R/T has become a two edged sword.

I am sure it would be illuminating for any one of youto sit on the flight deck of a large jet aircraft, wearingearphones and listening as she approaches terminal areassuch as New York, Chicago and Detroit. Only then wouldyou appreciate why I say that VHP R/T has become a twoedged sword. The pilot is coping with the terminal areanavigation, weather, descent approach and landing checklists and, at the same time, frequently finding himself involved with communications from and to the controller.As you know, the descent, approach and landing phasesof a flight can be fairly critical, particularly when the terminal area is busy. It is at this stage of a sector that theflight deck workload really "hots up". The pressure startsmildly when the pilot is instructed to start his descent atan earlier point than that shown on his flight plan. This, ofcourse, is done to separate his aircraft from outbound orover-flying traffic, and in North America is the rule ratherthan the exception. The pilot s first thought is for the extra

fuel which will be consumed as a result of the early descent. Again, because of the presence of other traffic, thedescent profile usually bears no resemblance to that whichwas planned about nine hours earlier. The pilot is askedto level out at various stages of the descent frequentlychange VHP frequencies and wait his turn to establishcontact on the new frequency, change transponder codesand in the latter stages of the descent, vary his aircraft'sairspeed either up or down. During these operations theconstant flow of VHP patter, to and from all aircraft, hasto be monitored, and, thrown in as it is to the flight deckarena, relentlessly punctuating the orderly progression offlight deck work, seems to have the effect of disproportionately increasing the workload. I am sure that the needfor the ground controller to constantly transmit and receive on VHP R/T results in his also having a high workload. The controller is there to ensure that there is a safe,smooth and expeditious flow of air traffic, but, with thingsas they are, he has to constantly interrupt his real workwith the need to talk and listen. In this respect, his job ismore exacting than that of the pilot, and sometimes, bythe tone of his voice, one can tell that things are gettingrather hect ic down there.

Am I telling you all this because I want to enlist yoursympathy for the pilot and the controller? No, ladies andgentlemen, I am telling you all this because I think that,the way it has gone, the present system is wrong. I wouldlike to see us have done with it.

V\/hat is the alternative to the present system? We leavethe details to the experts, but BALPA would be only toopleased to help.

If we had equitably staggered scheduling between airlines, airborne pictorial displays, alpha-numeric identification, data link, good autopilots coupled to accurate navigation equipment, good statutory approach patterns andprofiles involving accurate speed and height keeping oneach section of the approach, the controller would be freeto monitor the traffic and only need to speak when an aircraft begins to stray from the published pattern, speed orheight.

The pilot would have to leave the holding point righton his appointed time, and if he failed to achieve the timeexactly, he would immediately adjust his speed by a pre-computed amount to quickly regain his station in the pattern. This would require disciplined flying on the part ofthe pilot but, with his improved equipment and with theabsence of the need to communicate leaving him free toconcentrate, would not be beyond the capability of anypresent day pilot who is checked out to fly to any of these

Chairman, Concorde Evaluation Team,British Air Line Pilots Association.

2 6

busy areas. In other words, let the whole operation beproperly planned; let us look after the navigation and youlook after the monitoring, and away with the need forcontinuous radar vectoring, with its attendant surpriseelement and workload.

Likewise, the departure aircraft would be released ontime and then expected to maintain an accurate, butground radar monitored, departure profile.

This all sounds as if I am asking for Utopia, and is onlyone suggested alternative. One thing is certain, the present system cannot survive.

You may say: ''All that he has told us refers to NorthAmerica." This, talking of the present, I acknowledge. Iam pleased to be able to say that the ATC in and aroundthe British Isles is second to none. What pilot, of any nationality, can say nay to this when he is taken over by thefinal controller at London Airport. He gets the same sort oftreatment that he would expect from a Harley Street specialist, and that without the expensive bill at the end ofthe treatment.

The North American airspace does, however, at present, have more traffic but the reasons for the relative calmwhich exists in the British airspace need to be examinedso that the better facets of our system can be developedand built upon.

T h e r e i s o n e Te r m i n a l A r e a i n t h e M e d i t e r r a n e a nwhere the controllers, when there is a little weatheraround, and when there are more than three aircraftapproaching, give one the impression that all hell hasbeen let loose. In fairness to the controllers, one has tosay that for years their VHP equipment seems to havebeen consistently bad. The airfield in question shall benameless, but this does serve to illustrate that even inareas which are not busy, the quality of ATC can be poorand will require improvement before the introduction ofsuperson ic a i rc ra f t .

Still on the subject of communication, I would like tosee the areas in the cruise phase, which are not easilycovered by VHP, served by something other than our present archaic H. P. R/T. At the very least, the controller andthe pilot will need very much improved single side bandH. P. Even this will probably be subject to static interference when it is most needed. If a blanket of solar radiation descends unheralded, there will be static interference, and there may be a need for several SSTs in closeproximity to ask for descent clearance at the same time.

Airborne radio teletype is a form of communicationwhich I feel has never had a fair crack of the whip. I wouldlike to see manufacturers encouraged to develop suchequipment for use on supersonic aircraft. The airborneradio teletype could be used for receiving a whole host ofinstructions and information. Such equipment would needa Seical type warning to go with it and easy means for thepilot to acknowledge receipt of the message. The advantage of radio teletype is that it needs little attention, anddoes not seem so susceptible to interference as do otherforms of communication.

VHP satellite communication will probably be availablewhen the SST comes into service, but it is not likely to workin the polar regions across which some airlines are already planning their routes.

Please forgive me if I hove laboured the subject ofcommunications, but believe me, release the controller andthe pilot from the bulk of this time-consuming and sometimes irksome chore and you will find a marked increase

in their capacity to effectively carry out their proper respective functions.

Now let us have a look at the supersonic aircraft, totry to see how its operation will differ from that of a subsonic jet and how this may affect ATC.

We do know that the SST will use considerably morefuel during taxy than will the subsonic jet and other aircraft types. Its pilot will therefore not want to spend muchtime on the ground after start up. There seems to be arequirement for the time between start up and take-off tobe not longer than 15 minutes. If this were accepted, andI hope it will be, there would hove to be a by-pass taxi-way to moke it feasible. This by-pass taxiway would leadto a direct access loop at the take-off point thus allowingthe SST to circumnavigate the other aircraft in the queue.

Por the first few years of SST operation, this prioritywould not excessively penalise other aircraft and couldsubsequently be modified in the light of experience.

Airport noise abatement techniques have since theirintroduction, plagued the lives of pilots of large aircraft,especially at a place like Zurich in the middle of summer,with the aircraft at top weight. A high airfield, mountains,high temperature, thunderstorms and a heavy aircraft ona flight, say, to Nairobi, all spell trouble if you are caughtwith an engine failure whilst carrying out a noise abatement procedure. These techniques ore, of course, the concern of airport authorities rather than ATC, so I hope youwill forgive me for using this platform to state plainly, onbehalf of all pilots, that when the SST comes along, noiseabatement techniques must not become any more complicated or difficult to execute. Remember, that pilots, bythe very nature of their work, ore subject to a lot of noisethemselves, and are therefore very sympathetic towardspeople working and living close to airports. Sympathy,however, must be tempered with safety. I have heard thatsome backroom specialist is looking at the possibility ofasking SST pilots to fly the approach glide path in twosections, i.e. starting with a 6° glide path and convertingit to a 3° glide path close to the airfield. This sort of "trickcycling" is not on. The best way to minimise the effect ofnoise from landing aircraft and, incidentally, the best wayto keep passengers alive, is to get into the slot of a glideslope, which is not more than 3V2 , early on and staythere. Approach profiles which required any significantchange of glide slope would inevitably result in a largeincrease of engine power at the changeover point, andwhat is more important, could result in serious undershooting.

I w o u l d l i k e t o n o w l o o k a t a C o n c o r d e c l i m b o u t .Quite soon after she is airborne, her speed will be 400knots, the variable nose will be up, the glazed shield willbe up and her rate of climb will be high. It will not beeasy, in this configuration, for Concorde's, or for thatmatter any SST's pilot, to see ahead. I do not think thathe will expect to have a permanent climb out corridor, asexists today for some military aircraft, but I know that hewill be grateful for a straight uninterrupted climb from apoint not too far from his departure airfield. He will wantto be doing around Mach .93 at 25,000 ft. as soon as possible after take-off, where he can then wait for the transition to supersonic. This will also be desirable from a performance point of view.

During climbs on subsonic aircraft, some of you, travelling as passenger in the past, must have experienced whatI will call "weightlessness" when your pilot has desperate-

2 7

ly complied with a late instruction by ATC to level out ata given altitude. This is nearly always caused by theground controller having been caught by the unexpectedbehaviour of another aircraft in your vicinity. If you havehad this experience, I am sure that you will be right behind me when I say that the SSI pilot will need about5,000 ft. lead warning from ATC if he is going to berequired to level out at an intermediate altitude. The SSTwill have a much higher rate of climb, and lead time in thisrespect, will be important.

I will now turn to the question of military traffic. Therewill have to be a much greater liaison than exists at present between the civil and military over the U. K. andEuropean airspaces. If politics will allow it, I would like tosee one body controlling civil and military air traffic flying in the airspace of Western Europe and the British Isles.Military security is an obvious stumbling block to this, butas supersonic and faster subsonic aircraft appear on thescene, means will have to be found to increase the size ofcontrol areas and all traffic in those areas should, regardless of classification, be under one control.

The Air Traffic Control authorities are not the onlypeople who need to put their house in order, to preparefor the arrival of the supersonic and large numbers of news u b s o n i c a i r c r a f t . A i r l i n e s a n d m a n u f a c t u r e r s w i l l h a v e t o

take a long cool look at flight deck equipment and operational methods to see how best future operational efficiency can be improved. This, not only for economic benefitsbut also so that life will be made easier for the pilot andground controller, which in turn will moke for safer flying.

One item of equipment which every pilot would liketo see in a prominent position on his panel, is a pictorialnavigation display. Some airlines seem to be lukewarmabout ordering the pictorial display, other airlines, whoare not so lukewarm, do not seem to know where to putit. We, the British Air Line Pilots Association, want a pictorial navigation display and we want it positioned on theflight deck so that both pilots, in their correct operatingpositions, will easily be able to interpret its information.

When one considers the early need to evaluate equipment and methods connected with supersonic flight, itseems incredible to me that there is no truly representativeConcorde simulator avai lable in the Bri t ish Is les. Al l of uswho are in any way concerned with the Concorde project,must wish to see this serious omission speedily put right.

Sonic boom and oceanic track selection are two questions which will bedevil the planners and the airlines. Theairlines and the manufacturers of supersonic aircraft obviously hope that no sonic boom or track selection restrictions will be made. It is nevertheless necessary to look ats o n i c b o o m a n d t r a c k s e l e c t i o n i n o r d e r t h a t w e c a n s o o nd e v i s e m e t h o d s t o m i n i m i s e t h e n u i s a n c e t o r e s i d e n t s o f

populated areas, and also minimise the economic penalt ies to operators.

As far as supersonic aircraft flying west from the BritishIsles are concerned, the acceleration to supersonic can,with a slight utilisation and fuel penalty, take place overt h e s e a . S o m e a c c e l e r a t i o n a r e a s l o o k m o r e a t t r a c t i v e t h a n

others, for Instance, the area to the west of the Scilly Islesand south of Eire appears to lend itself ideally to the operation. However, weather and other considerations, on theday, may make it necessary to break the sound barrier inother than the ideal areas. This non static aspect of theoperation may make the provision of ground based radar,to regularly monitor the transition, very difficult to achieve.

I hope that the difficulties will not be insurmountable, because there seems to be a definite requirement for thisphase of the flight to be adequately radar monitored fromthe ground. In all cases where ground radar monitoring isfeasible, pilots would like to see a meteorological radaroperator sitting side by side with the ground controller,operating his own cloud detecting radar, so that he caneasily advise the ground controller. This we would alsolike to see set up in terminal areas. Last year I was radarvectored, on a climb out of Chicago, straight through aminor line squall over Lake Michigan. I am only too pleased to say that it was not as severe as the one which caughtthe BAG 1 —11 a month or two later.

If the airlines are going to be allowed to fly on themost favourable track of the day there will be new problems. On most occasions the best track is likely to benear the great circle, which will take the SST over themaritimes and possibly into sonic boom restrictions. It willalso take the SST over lower flying subsonic aircraft, theyalso favour the great circle, and then the problem of unscheduled SST descents crops up. As far as lower flyingtraffic is concerned, on the rare occasion that the SST mayneed to descend due to a high level of radiation, the SSTsdescent problem does not look too serious. According tothe prophets, she should be clear of damaging radiationat 42,000 ft. This would only just put her in the flight levelbonds of subsonic traffic. If, however, the SST had to descend due to an engine failure at cruising level, she willneed to come down to a sufficiently low level to enableher to slow down to a speed which will allow the failedengine to stop windmilling. Once the engine has stopped,the next consideration will be the continuation of theflight on three engines. In the case of Concorde, and itwon't be very much different for other delta shaped SSTs,the optimum three engine cruise will be between 29,000 ft.and 33,000 ft. depending upon her weight at the end ofthe drift down. I think I am correct in saying that if, froma fuel consumption point of view, she is going to reach herintended destination on three engine cruise, she will haveto fly at these lower levels. Although we all know howremarkably reliable the modern turbo jet engine can be,and I see no reason for the Olympus 593 or other supersonic engine to be any less reliable, the possibility of anengine failure can never be ruled out. It is for this reasonthat track allocation for the supersonic aircraft, overoceans, may be governed by the need to keep them awayfrom the areas where subsonic aircraft are flying. Thiswould give the SST greater freedom of movement in thevertical plane.

On long sea crossings the Mach 2.0+ aircraft will needto have consistently accurate navigational and coursesteering equipment. It will also be highly desirable forATC radar coverage to extend well out over the ocean inorder to quickly detect any inadvertent departure by thesupersonic from her intended track. Because of the speed,any inadvertent excursions from track will be highly significant and will require early detection.

From what we have been told, it does seem likely thatthe supersonic aircraft will have very accurate and reliable navigational equipment. Nevertheless, we in BALPAwould like to see such equipment well tested and routeflown on the Mach 2.0+ aeroplanes before there is anymove to reduce the present lateral separation over theo c e a n s .

2 8

Later in the supersonic programme lateral space athigh altitudes is likely to be at a premium and it maywell be that vertical space will have to be used moreeconomically than is at present envisaged. Altimeterswhich derive their information from pressure ore notoriously inaccurate high up and this is one reason that wehave to think in terms of large vertical separation. Hasanybody thought of developing a high level radar altimeter? If it is feasible, it should indicate height veryaccurately over the sea. The other reason for large vertical separation is that, on most high speed aircraft, thepilot's pitch information on his panel has been relativelypoor. We look for a decided improvement in this field,for both the pilot's and Air Traffic Control's sake.

On the question of airborne equipment, the situationexists today where numbers of aircraft are flying in thesame areas with widely different equipment, e. g. the VCIOflying with precision altimeters, which derive their information from pressure and an air data sensor, alongsideother aircraft flying on the old fashioned "steam" jobs.As we introduce new aircraft, I think that it would be wisefor the licensing authorities to keep a much tighter rein onairborne equipment, especially with such items that cangive you a different story, on each aircraft type, for thesome set of parameters. This should apply to private, military and airline operators.

The supersonic pilot will need to know his position veryaccurately when he is approaching the point where hestarts his descent to his destination. Long range DME willhelp, but he will also need clearance from ATC to descendwell in advance of his flight plan descent point. Before heleaves his cruising level he will need adequate landinginformation pertaining to his destination. Europe is fairlywell covered in this respect by VHP for weather, but thelanding information which we now receive from VOR/voice is just not good enough. Colts Neck and Deer Parkin the New York terminal area, are prime examples. In

order to gather information from most VOR stations, it isnecessary, even at close range, for one crew member toclamp his earphones with both hands to be able to hearthe speech. Broadcasts giving landing information withsufficient range and clarity will be a must for the SST.

So that she will not be heavily penalised on fuel consumption, Concorde will need to fly the initial approachand holding patterns at 300 knots. She will waste a lot offuel if she has to fly these patterns at the present slowermandatory speeds. To allow for possible flight deck errors,it may be that the present ICAO holding areas will haveto be enlarged or repositioned further away from otherholding, departure or approach areas.

Ladies and Gentlemen, most of you ore probably already well advanced in your thinking on the problemswhich I hove raised in this paper, you no doubt hove beenaware of them as long as I have. My main purpose in thepreparation of this paper was to try to highlight someareas which I am sure will be of concern to the supersonicpilot and Air Traffic Control. There ore more, but mytime here is running out.

From what I know of the thought, money and workwhich has gone into the Concorde programme, and theamount of test flying which is planned for Concorde, I amsure that she is going to be a winner. Let us also not forgetthat she is well ahead of her rivals, at least, the ones thatwe know about. So that her introduction into passengerservice will not find us unprepared, I will end this paperagain expressing the hope that urgent investigation of theproblem areas will continue, and that no effort or expensewill be spared to modify or change existing systems thatmay be found wanting. The penalties for an unnecessarilyrestrictive operation for the supersonic will be high, especially in terms of aircraft utilisation. The rewards for onunrestricted and successful operation will be economicallyhigh, and should amply recompense us for the effort andmoney spent in making ourselves prepared.

Electronic ScarecrowThe hazard of bird strikes to aircraft has, for some

time, been a matter of concern to aircraft operators andairport authorities.

Various methods of scaring birds away from airfieldshave been investigated, but there does not seem to be asimple solution to the problem. In most cases were acoustical means were applied, the birds got quickly accustomedto whatever noise generator was used.

The firm SABA has recently developed on electronicscarecrow which con produce such a variety of natural andartificial callnotes and distress calls that the birds allegedly to not get accustomed to them. The sound spectrum ofthe colls is partly in the ultrasonic range. It has been composed so as to cause particular discomfort to animals butmin imum d is turbance to the human ear.

The scarecrow is of simple construction and virtuallyfree from wear and tear. Its power consumption is sufficiently low for battery operation over an extended periodof time.

A pulse generator, multivibrators, power amplifier andloudspeaker are the main components of the system. Theloudspeaker is matched to the acoustical impedance of theatmosphere by means of a horn, for optimum sound radia t i o n . S A B A

2 9

T h e I n t e r n a t i o n a l F e d e r a t i o no f A i r Tra ffic Cont ro l le rs Assoc ia t ions

A d d r e s s e s a n d O f fi c e r s

A U S T R I A

Verband Osterreichischer FlugverkehrsleiterA 1300, WIen Flughafen, Austria, Postfoch 36P r e s i d e n t A . N o g yV i c e - P r e s i d e n t H . K i h r

S e c r e t a r y H . B a u e rD e p u t y S e c r e t a r y W . S e i d IT r e a s u r e r W . C h r y s t o p h

B E L G I U M

Belgian Guild of Air Traffic ControllersAirport Brussels NationalZaventem 1, BelgiumP r e s i d e n t A . M a z i e r sV i c e - P r e s i d e n t M . v a n d e r S t r a a t e

S e c r e t a r y C . S c h e e r sS e c r e t a r y G e n e r a l A . D a v i s t e rT r e a s u r e r H . C a m p s t e y nE d i t o r J . M e u l e n b e r g sI F A T C A L i a i s o n O f fi c e r J . A e l b r e c h t

C A N A D A

Canad ian A i r Tra f fic Con t ro l Assoc i a t i on56, Sparks Street

Ottawa 4, CanadaP r e s i d e n tV i c e - P r e s i d e n t

Managing DirectorT r e a s u r e r

J. D. LyonJ. C. ConwayG. J. V^illiamsA. Cockrem

Chairman IFATCA Comm. R. Roy

D E N M A R K

Dan ish A i r Tra ffic Cont ro l le rs Assoc ia t ion

Copenhagen Airport — KostrupD e n m a r k

V. F r e d e r i k s e n

V i c e - C h a i r m a n A a . J a e n i c k eS e c r e t a r y E . C h r i s t i a n s e nT r e a s u r e r P . B r e d d a m

M e m b e r o f t h e B o a r d M . J e n s e n

F I N L A N D

Assoc ia t i on o f F inn i sh A i r Tra f fic Con t ro l O ffice rSuomen Lennonjohtojien Yhdistys r. y.A i r T r a f fi c C o n t r o l

H e l s i n k i L e n t o

C h a i r m a nV i c e - C h a i r

SecretaryT r e a s u r e r

D e p u t y

F r e d . L e h t o

V d i n o P i t k d n e n

H e i k k i N e v a s t eAimo HapponenVi l i o S u h o n e n

F R A N C E

French A i r Tra ffic Cont ro l Assoc ia t ionAssociation Professionnelle de la Circulation AerienneB. P. 206, Paris Orly Airport 94F r a n c e

Pres iden tF i rs t Vice-Pres identS e c o n d V i c e - P r e s i d e n t

General SecretaryT r e a s u r e r

Deputy SecretaryDeputy TreasurerIFATCA L ia i son O ffice r

Francis ZammithJ. M. LefrancM . P i n o nJ . L e s u e u r

J . B o c a r dR. PhilipeauM . I m b e r t

A. Clerc

G E R M A N Y

German A i r Tra ffic Con t ro l l e rs Assoc ia t i onVerband Deutscher Flugleiter e. V.3 Hannover-Flughafen, GermanyPostlagerndC h a i r m a n W . K a s s e b o h mV i c e - C h a i r m a n H . G u d d a tV i c e - C h a i r m a n E . v o n B i s m a r c kV i c e - C h a i r m a n H . V / . K r e m e rS e c r e t a r y H . J . K I i n k eT r e a s u r e r K . P i o t r o w s k iE d i t o r L . G o e b b e l sI F A T C A L i a i s o n O f fi c e r W . G o e b e l

GREECE

Air Traffic Controllers Association of Greece10, Agios Zonis Street, Athens 804, GreeceP r e s i d e n t C . T h e o d o r o p o u l o sV i c e - P r e s i d e n t N . P r o t o p a p a sG e n e r a l S e c r e t a r y E . P e t r o u l i a sT r e a s u r e r S . S o t i r i a d e s

H O N G K O N G

Hongkong Air Traffic Control AssociationHongkong AirportP r e s i d e n t A . A . A l l c o c kS e c r e t a r y R . L . A y e r sT r e a s u r e r R - L o

I C E L A N D

Air Traffic Control Association of IcelandReykjavik Airport, IcelandC h a i r m a n G . K r i s t i n s s o nS e c r e t a r y S . T r a m p eT r e a s u r e r K . S i g u r o s s o n

I R A N

Iranian Air Traffic Controllers AssociationMehrobad International AirportTeheran , I ranSecretary General E. A. Rahimpou

3 0

I R E L A N D

I r i sh A i r Tra ffic Cont ro l Officers Assoc ia t ionATS ShannonI r e l a n d

P r e s i d e n t J . E . M u r p h yV i c e - P r e s i d e n t P. J . O ' H e r l i h yG e n . S e c r e t a r y J . K e r i nT r e a s u r e r T . L a n eAsst. Gen. Secretary M. Durrack

ISRAEL

Air Traffic Contro l lers Assoc ia t ion o f Is rae lP. O. B. 33Lod Airport, IsraelC h a i r m a n J a c o b W a c h t e lV i c e - C h a i r m a n W . K a t zT r e a s u r e r E . M e d i n a

Associazione Nazionale Assistenti e Controlloridella Civil Navigazione Aerea ItaliaVia Cola di Rienzo 28Rome, ItalyP r e s i d e n t D r . G . B e r t o l d i , M . P .S e c r e t a r y L M e r c u r iT r e a s u r e r A . G u i d o n i

L U X E M B O U R G

Luxembourg Guild of Air Traffic ControllersLuxembourg AirportP r e s i d e n t A l f r e d F e l t e s

S e c r e t a r y A n d r e K l e i nT r e a s u r e r J . P - K i m m e s

R H O D E S I A

Rhodesian Ai r Traffic Contro l Assoc iat ionPrivote Bag 2, Salisbury AirportR h o d e s i a

P r e s i d e n t C . W . D r a k eS e c r e t a r y C . P . F l a v e l lT r e a s u r e r W . V a n d e w a a l

S W E D E N

Swedish Ai r Traffic Contro l lers Assoc ia t ionFack 22, Sistuna, SwedenC h a i r m a n L . B e r k e n s t a mS e c r e t a r y A . K a r l a h a gT r e a s u r e r C . A . S t a r k m a nIFATCA Representa t ive G. A t te rho lm

S W I T Z E R L A N D

Swiss Ai r Traffic Contro l lers Associat ionV. P. R. S., P. O. Box 271CH 1215, Geneva Airport, SwitzerlandC h a i r m a n J . D . M o n i n

S e c r e t a r y T . R o u l i n

T U R K E Y

Turk ish A i r Tra ffic Cont ro l Assoc ia t ionYesilkoy Airport, Istambul, TurkeyP r e s i d e n t A l t o n K o s e o g l u

U N I T E D K I N G D O M

Gui ld o f A i r Tra ffic Cont ro l Officers14, South Street, Park LaneLondon W 1, EnglandM a s t e r A . F i e l d , Q B EE x e c u t i v e S e c r e t a r y W . R i m m e rT r e a s u r e r E . B r o d s h a w

N E T H E R L A N D S

Nether land Gu i ld o f A i r Tra ffic Con t ro l le rsPostbox 7590

Schiphol Airport Central, NetherlandsPres ident

SecretaryTreasurerMember, PublicityMember, IFATCA-affairs

J. van LondenF. M. J. MenteP. K a l f f

T. M. van GaalenB. H. van Ommen

NEW ZEALANDAir Traffic Control AssociationDept. of Civil Aviation, 8th Floor, Dept. BIdasStout Street

Wellington, New ZealandP r e s i d e n t E . M e a c h e nS e c r e t a r y C . L a t h a m

N O R W A Y

Lufttrafikkledelsens ForeningBox 51, 1330 Oslo Lufthavn, NorwayC h a i r m a n G . E . N i l s e n^ ' c e - C h a l r m o n K . C h r i s t i a n s e nS e c r e t a r y j . K a l v i kT r e a s u r e r E . F e e t

U R U G U A Y

A s o c i a c i o n d e C o n t r o l a d o r e s

Aeropuerto Nacional de CarrascoTorre de Cont ro lMontevideo, UruguayC h a i r m a n U . P a l l a r e sS e c r e t a r y J . B e d e rT r e a s u r e r M . P u c h k o f f

VENEZUELA

Asociacion Nacional de Tecnicos enTrans i to Aereo Venezue laAvenida Andres Bello, Local 78129 Caracas, VenezuelaP r e s i d e n t M a n u e l A . R i v e r a P .S e e r . G e n e r a l V . A l v a r e z . J i m e n e z

Y U G O S L AV I A

Jugoslovensko Udruzenje Kontrolora LetenjaDirekcija Za Civiinu Vazdusnu PlovidbuNovi Beograd, Lenjinov Bulevar 2YugoslaviaP r e s i d e n t A . S t e f a n o v i cV i c e - P r e s i d e n t Z . V e r e sS e c r e t a r y D . Z i v k o v i cT r e a s u r e r D . Z i v k o v i cM e m b e r B . B u d i m i r o v i c

Corporation Membersof the International Federationof Air Traffic Controllers' AssociationsThe Air Traffic Control Association,Washington D. C., U.S.A.The Air Transport Association,Washington D. C., U.S.A.Wolfgang Assmann GmbH., Bad Homburg v.d.H.Compagnie Generale de Telegraphie sans FilMalakoff, Paris, FranceCossor Radar and Electronics Limited,Harlow, EnglandThe Decca Navigator Company Limited, LondonELLIOTT Brothers (London) LimitedBorehamwood, Herts., EnglandF E R R A N T I L i m i t e dBracknell, Berks., EnglandGlen A. Gilbert & Associates,Washington D. C., U.S.A.IBM World Trade Europe Corporation,Paris, FranceInternational Aeradio Limited,Southall, Middlesex, EnglandITT Europe Corporation, Brussels, BelgiumJeppesen & Co. GmbH, Frankfurt, GermanyThe Marconi Company Limited Radar DivisionChelmsford, Essex, EnglandN.V. Hollandse SignaalapparatenHengelo, NetherlandsN.V. Philips Telecommunicatie IndustrieHilversum, HollandThe Plessey Company LimitedChessington, Surrey, EnglandSelenia - Industrie Elettroniche Associate S.p.A.Rome, ItalyThe Solartron Electronic Group, Ltd.Farnborough, Hants., EnglandTelefunken AG, Ulm/Donau, GermanyTexas Instruments Inc., Dallas 22, Texas, USAWhittaker Corporation,North Hollywood, California, USA

The Internationa! 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 technicalinformation 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 thefi e l d o f a i r t r a f fi c c o n t r o l .

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Schiphol.First airport in Europe

with an automaticair traffic control

data-processingsystem;

Schiphol AmsterdamSATCO automaticair traffic controlin full operation.

Main features of SignaalMain operational featuresflight path calculationc o o r d i n a t i o nclearance processingcorrelation between radar data andflight plan dataconfl ic t r i sk de tec t ionc o n fl i c t r e s o l u t i o ne lec t ron ic da ta d isp laysynthetic dynamic displaydaylight large screen displayflight progress boards t r i p p r i n t i n gautomatic transfer of data via datalinks to adjacent centres

flight plan and radar data-processing systems.Programming featuresm o d u l a r d e s i g nfl e x i b i l i t yreconfiguration capabilitieson-line real-time programmingsoftware and hardware controlledmulti-level programming

Computer featuresmicrominiaturization techniqueshigh operating speed1 microsec. memory cyclemass memoriesfiigh reliabilitygrowth potentialcontinuity of operationeasy servicing.

S I G N A A L

. „ on ROX.12 Hengelo. The Nelherlands.-ply to N V. Htjilandse Signaalapparale ,For further information please apply to

t rhi H«fa handling and air traffic control systems;:.t rOUANDSE SIGNAALAPPARATEN HENGELO

AIR TRAFFIC CONFUSION OR.^'1' miLftgA'.

:>r.

D E C C A H A R C OThe answer to increasing air traffic confusion is an accurate, comprehensive, automafic and reliable Nav/ATCsystem incorporating a Data Link.Decca-Harco is the only system that can meet thenavigation and ATC demands of both sub- and supersonic air traffic. And only Decca-Harco can provide theflexibility and accuracy that permits close lateral separation of aircraft throughout the route structure.At the control centre the Decca Data Link providesthe controller with accurate displays of the identity, altitude and precise position of all co-operating aircraft,using the common reference of a high accuracy, areacoverage system. The necessity for R/T communicationis reduced by the use of two-way Alpha-Numeric messages and routine reports are eliminated, reducing theworkload and increasing the reliability of the ATC system.

On the flight-deck Decca Omnitrac—the world's mostadvanced lightweight digital computer—provides thepilot with undistorted pictorial presentation and automatic chart changing. The 'ghost beacon facility giveshim bearing and distance to any point. Omnitrac alsoprovides auto-pilot coupling and automatic altitude control which maintain respectively any required flightpath and flight profile. The ETA meter indicates either timeto destination or ETA.

It is only through an integrated system, operating from acommon reference, such as Decca-Harco, that a greatmany aircraft of different types flying at various speedsand altitudes can be efficiently co-ordinated into a singledisciplined traffic pattern.

DECCA-HARCOThe comprehensive Nav/ATC systemThe Decca Navigator Company Limited • London