TELEFUNKEN

-T E L E F U N K E N radar for safe

guidance from take-off to

landing

Visit Telefunken at the Hanover Fair 1962

You will find us in Hall 13 at Stand 106

and at the German Aviation Show in Hall Bat Stand 1408

rr !

L

IFATCA JOURNAL OF AIR TRAFFIC CONTROL

THE CONTROLLER Frankfurt am Main, April 1962

Publisher: International Federation of Air Traffic Con­trollers' Associations, Cologne-Wahn Airport, Germany.

Elective Officers of IFATCA: L. N. Tekstra, President; Maurice Cerf, First Vice President; Roger Sadet, Second Vice President; Hans W. Thau, Secretary; Henning Throne, Treasurer.

Editor: Walter H. Endlich, 6 Frankfurt am Main 1, Roi­mundstrasse 147, Phone 20821 or 521710.

Production and Advertising Sales Office: W.Kramer&Co., 6 Frankfurt am Main NO 14, Bornheimer Londwehr57a, Phone 44325, Postscheckkanto Frankfurt am Main 11727. Rale Cord Nr. 1.

Printed by: W.Kramer&Co.,6 Frankfurt am Main N014 Bornheimer Landwehr 57a. '

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

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

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

Contributions are welcome as are comments and criti­cism. No payment can be made for manuscripts submit­ted for publication in "The Controller". The Editor re­serves the right lo make any editorial changes in manu­scripts, which he believes will improve the material with­out altering the intended meaning.

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

Advertisers in this Issue: Gilfillan Bros. (Back cover). Morconi's Wireless Telegraph Company (Inside back cover). Standard Elektrik Lorenz (21). Telefunken GmbH (Inside front cover).

Picture Credit: British Features (23). Curtiss Wright Corp. (29, 31, 32). Decca Radar Limited (24). Ernst Heinke! GmbH (21). Telefunken GmbH (25).

Volume l · No. 2

CONTENTS

Separation of Aircraft in the Approach and Departure Phases W. C. Woodruff

2

Psychological Aptitude Tests for Air Traffic Control Officers 5 Dr.-!ng. Hans Zetzmann

Human Factor Analysis of Voice Communication Practices in Air Traffic Control 8

Air Traffic Control in the Netherlands 10

Sensitive Aircraft Altimeter with Linear Subscale calibrated in Values of Altitude Units

Prof. Dr.-lng. E. Roessger and G. Raenike

Project Beacon, Evaluation and Summary

New International Aviation Organization formed

Must the VHF Omni-Range make Way for a Hyperbolic System?

Doppler VOR in Service in the United States

Hannover Air Show 1962

ATC News from the U.K.

Maiden Flight of the Potez-Heinkel CM 191

IFATCA Member Associations

Survey:

Modern Equipment, Installations and Systems for Air Traffic

Control and Air Navigation

As we go to press ...

13

15

18

19

20

20

21

22

22

23

32

Separation of Aircraft in the Approach

and Departure Phases

W. C. Woodruff*

Paper presented at the Three-Nations-Convention, DOsseldorf 1961.

Introduction

There are two ways in which collision-avoidance in the

air may be initiated - by the pilot and by a ground organisation. In keeping with the theme of this meeting and because I am here representing the United Kingdom Guild of Air Traffic Control Officers, that is to say a ground organisation, I shall deal mainly with the Air

Traffic Control aspect. Pilot-initiated collision avoidance has been the subject

of many studies in the United Kingdom and in other coun­tries, and present indications are that there is no reliable way of presenting a pilot with information or instructions on which he can act with an assurance that a threatened collision can be avoided. The normal rules of the air may be considered adequate, though not ideal, only for low performance aircraft in good weather conditions. For low performance aircraft in poor weather conditions and for high performance aircraft in any weather conditions, the lack of accurate information on the relative position of the threatening aircraft and the lack of knowledge of the intention of the pilot of the threatening aircraft, both essential to the initiation of avoiding action, can be re­medied only by elaborate equipment in both aircraft. The ability of such equipment to solve any but the simplest confliction between only two aircraft, is doubtful. More­over, it seems preferable that collision should be avoided by advance planning and regulation by a ground organi­sation rather than by last-minute action on the part of

the pilot. If these premises are accepted it follows that the

ground organisation - that is, Air Traffic Control -should provide adequate separation between all high per­formance aircraft in a!! weather conditions, between high performance aircraft and all other aircraft in all weather conditions, and between all aircraft in poor weather con­ditions. In most countries this service is provided only over specified areas, but it seems inevitable that in the future it will have to be provided over all areas where flying takes place. Given an adequate route structure it is not difficult to provide an Air Traffic Control collision-avoid­ance service to en-route traffic. Such traffic is usually fly­ing clearly defined tracks at constant levels and separa­tion in the vertical plane for those tracks which are too close, will provide the necessary safety. In a terminal area however, the provision of safe separation is a much more difficult and complicated task. In such an area, arriving aircraft are converging on to the various reporting points and descending from their cruising levels. Both the arriv­ing and departing aircraft will need to be separated from each other and from other aircraft which are overflying the terminal area. Thus there is a complicated and rapidly changing situation in which it is necessary constantly to employ all three methods of separation - longitudinal,

lateral and vertical.

United Kingdom Guild of Ai1· Traffic Control Officers.

2

Separation between Departing Aircraft

Let us consider first the various methods of providing separation between departing aircraft. The simplest me­thod is to space them longitudinally by the imposition of the necessary take-off interval. Without the use of radar, two aircraft of the same speed flying the same route at the same level will, under present international standards, require 10 minutes separation. If they will be flying at different levels it may be possible to reduce this to 5 minutes. If radar is employed, 2 minutes may be possible but in the case of aircraft flying the same route at the same level, radar control will be necessary for the whole of the flight. This is as yet rarely possible since radar handovers between adjacent countries are not yet feasible. Bilateral and multilateral agreements for such procedures will, it is hoped, be made as soon as adequate radar coverage is available.

The basic figures given for longitudinal separation of departures assume aircraft of the same speed. With the rapid increase in high performance aircraft and the con­tinued employment of the older types, successive depar­tures will, more often than not, have different speeds. If the second of any pair is faster, the separation will clear­ly need to be increased. It soon becomes obvious that the employment of longitudinal separation only, is far too restrictive in all but the least busy terminals. It is there­fore necessary to use another form of separation - ver­tical. If several aircraft are to fly the same route at diffe­rent levels, it is convenient if vertical separation can be applied not only at cruising levels but throughout the climb. In the ideal situation, the aircraft cruising at the higher level will take off first followed by the second highest and so on.

In this way a departure interval of about two minutes may be achieved by stepping up each aircraft 1,000 feet below the one ahead. Moreover since the aircraft at the higher levels will usually be the ones with the higher speeds, longitudinal separation will increase with the pro­gress of the flights. This ideal order of take-off - highest and fastest first - occurs only at the national airport of Utopia. Elsewhere, although such a sequence of two or even three aircraft may occur occasionally, the reverse situation will occur with equal frequency. A slow aircraft wanting a low cruising level followed by a fast aircraft wanting a high cruising level is a particularly difficult operation to carry out with the least possible restrictions. Not only are the speeds and rates of climb of the two air­craft different, but both these factors are varying with hight, and thus the relative speeds - both forward and vertical - of the two aircraft are not constant. The pro­blem of ensuring the requisite longitudinal separation at the time the second aircraft climbs through the level of the first, is one which - in the absence of radar - is usually solved by the judicious combination of arithmetic, experience and caution. The result is often a separation

in excess of that required and an unnecessary delay to the second and subsequent aircraft.

Radar cannot offer any assistance in the prov1s1on of vertical separation per se since its use can permit reduc­tions of separation only in the horizontal plane. However, by reducing the longitudinal separation standards, radar can shorten appreciably the time during which vertical separation is necessary. It may even, by the same means, avoid the necessity for any vertical separation to be given.

We have seen that the useful applications of longitu­dinal and vertical separation are limited by the relative speeds, forward and vertical, of pairs of departing air­craft. Neither of these forms of separation, nor the combi­nation of the two, is sufficient to avoid excessive delays at a busy airport. We must therefore bring in the third form of separation - lateral. In an uncontrolled and un­restricted environment, a considerable measure of lateral separation between departures is provided by the natural segregation of routes. In a controlled environment, it is necessary not to lose too much of this natural divergence of tracks by artificial canalisation. A certain amount of restriction to departure routes is necessary to avoid con­flictions with the routes of other traffic, but a reasonable balance between the two needs can usually be found. Lateral separation, although probably the most useful and rewarding separation to apply to departing aircraft, is also the most difficult. The main reason for this difficulty arises from the fact that to apply this separation to air­craft taking off from one runway, it is necessary for them to fly on divergent tracks. This in turn gives rise to the use of a greater volume of airspace than would be required if they all followed the same track. From this stems two problems. Firstly, either these tracks must be marked by a suitable navigational aid, or aircraft must be vectored along them under radar control. If the former way is chosen, then unless the navigational aid is suitable for defining any track in space, there is a loss of flexibility that may seriously limit the benefits of lateral separation. If the latter way is chosen, the load on the Air Traffic Control unit will increase and with this increase will come the difficulties of co-ordination caused by an increasing number of controllers dealing with aircraft in the same airspace. Secondly, with the present division of airspace into controlled and uncontrolled, any increase in the con­trolled, especially in a small country with a large military air force, may be impossible without severe penalties to those who fly in the uncontrolled areas. The only satis­factory answer to this problem is to abolish the division between the two types of airspace and to have an Air Traffic Control system which can make the optimum use of any piece of airspace at any time according to circum­stances. There are many difficulties to be overcome before this can be done and it is not (fortunately!) my task to discuss them here.

In the last two years the rapid build-up of civil jet traf­fic has again emphasised the need to avoid delays to the climbs of departing jets and the best way to do this is the provision of discrete laterally separated climb tracks. Each generation of aircraft is more uncompromising and more unforgiving than the last; and supersonic civil transports may be flying in less than ten years' time.

From what has been said, it would be seen that the dis­advantages involved in the use of lateral separaton are organisational rather than operational, and every effort

will have to be made to overcome them because the re­wards are great and the penalties for failure are harsh.

So far, the three forms of separation which can be applied between departing aircraft have been considered on the assumption that all the aircraft take off from one runway. A terminal area however will have several aero­dromes generating departing traffic and some of these aerodromes will have several runways in use for depar­tures. In the Utopian terminal area there are only two aerodromes - one west of the capital for aircraft which fly on routes west of the Utopian meridian and one east of the capital for the others. As traffic increases there are plans for two more aerodromes - one north of the capi­tal and one south, and when these are built, traffic will fly to and from the aerodrome applicable to the quadrant in which its route lies. Moreover, the aerodromes will be 20 miles from the centre of the capital and therefore near­ly 30 miles from each other. The Utopian Aviation Autho­rities considered this a reasonable compromise between the need for quick access to town and the need to avoid the airports' traffic patterns interfering with each other. But life there is duii and every Utopian Air Traffic Control Officer prays for the day when an aircraft from the nor­therly aerodrome will want to fly south. In our world such prayers are unnecessary.

!t is extraordinary how much trouble and delay to traf­fic can be caused by a single aircraft departing an aero­drome in a terminal area and wishing to fly a route which takes it across the area and through the pattern of other aerodromes. Longitudinal separation from other traffic is possible but is difficult to apply with accuracy even when radar is employed. Vertical separation is rarely pos­sible unless each aerodrome is allotted specific heights. This is wasteful of airspace and does not necessarily solve the problem when one aircraft has to climb through the height of another. And so we are back again to lateral separation. The provision of tracks laterally spaced so that confl iction between traffic from adjacent aerodromes is deferred until another form of separation is possible, is again mainly an organisational problem.

If it cannot be arranged that aircraft at aerodromes in the north of a terminal area fly to and from the north and those in the south to and from that direction, at least one might expect that1 such a schema could operate at a single aerodrome with parallel runway. When two such runways can be used for take-offs, then provided_ they are more than a minimum distance apart, the theoretical take­off rate for a single runway can be doubled provided departure routes are arranged so that every aircraft turns away from the parallel runway after take-off. For many reasons this theory can rarely be put into practice. These reasons include: different noise regulations for the two runways, different runway lengths, different aids, and ground routeing variables. Thus when two parallel run­ways are used for take-off there are usually additional separation problems to be solved. When one aircraft is turning across the take-off path of another, longit_udinal separation is normally the only form that it is possible to employ. Radar can assist materially by seeing when one aircraft has cleared the proposed path of the other.

A similar problem and solution applies to the use of two runways which cross each other. In such a case there is another and obvious problem in that the runways and therefore the paths of the departing aircrnft, cross. The resolution of this problem is simple - one aircraft is not

3

has recently read a paper to traffic psychologists, which deals especially with psychological aptitude tests for pilots. Through his kindness, this paper has been placed at my disposal').

To quote from Dr. Seifert: "What about the required knowledge and the individual qualification for the pilot's profession? To decide on these prior conditions, the licens­ing authority depends solely on the results of the official theoretical and practical pilot's examination. When ap­proached from a psychological standpoint, this informa­tion on which a pilot's licence is to be based, does not at all suffice to guarantee the highest possible safety in pri­vate and commercial air traffic."

I perfectly agree to this opinion when considering the aptitude tests for air traffic controllers, and I think that apart from a general bodily fitness, the air traffic control officer has to meet certain special psychological require­ments.

As far as I know, applicants for the air traffic control service are tested at the various ATC-offices in the fol­lowing way. They are shown a sheet of paper, on which there are 20 different words in the English language, in different sizes and prints, some coloured, some in negative plate. The applicant is allowed to look at this sheet for 2 minutes, whereupon he is given another 2 minutes' time to put down these 20 words from his recollection. In the second test, a sheet of paper with some geometrical figu­res may be looked at for 2 minutes. Then these figures have to be drawn by heart; time allowed 2 minutes. Then a labyrinth has to be followed with a pencil in 2 minutes, and the applicant will undergo an intelligence test consist­ing of a navigational question: Where does an aircraft arrive finally, flying at a constant angle to each successive meridian? (I consider this question to be a psychological failure, because it will confuse anybody who has no navi­gational training.) Then there is a T-test and a laying test, the latter of which is controlled by a stop-watch, and the examinee has to read off the times himself. During this test distracting questions may be asked, which must not impair the result of the test.

I do not know when these psychological methods of investigation have been developed, but I suppose there has been no intensive participation of a psychologist.

In contrast to these methods, 44 written and oral tests within 8 hours are used by the Americans to scan the ability of their applicants. I want to quote from the que­stionnaire that is employed to test the ability of rapid conception. The paper contains 50 lines of 29 figures each. At the beginning of each line, one figure is placed in brackets:

(6) 7 8 4 5 3 7 6 4 3 6 8 5 3 1 0 2 5 6 7 3 3 5 2 3 7 9 0 1 1

The candidate has to cross out all figures that are iden­tical with the one in brackets. Then he has to check the next line. The time allowed for this test is 21h minutes. (Nobody has made it up to now.) In this way the ability is to be tested to distinguish quickly a known object from a number of insignificant surrounding objects. This is very important for an air traffic controller who has to spot the object, which he is going to supervise, in a mess of blips on a Radar-screen, or who has to distinguish one aircraft from another at a short glance during dense traffic hours.

') Rudiger Seifert, Ergebnisse fliegerpsychoiogischre Untersuchungcn.

6

It is equally instructive to know the method of testing how to see completeness in a plurality of details. The point is to find out something intellegible without knowing what to look for. On a page of 22 lines containing a medley of letters some 4-letter-words are to be distinguished. The following line is a typical example:

QDGPOETJHSTOPJSZVAUTO

NIJKJREWZNPUGOKAYZYAP

The 4-letter-words in this line are "poet", "stop", "auto", and "okay". This problem has to be solved in 2'h minutes as well.

Additionally, the ability how to remember information is tested. A story is read by an instructor. During the next 5 minutes, two completely different tests are carried out. Then each applicant has to answer questions from this story. The answers and the time needed will show the ability to register information, to "store" it, then to do something quite different, but to have the information handy afterwards without much reflection>). These ex­amples will do.

. I want now to discuss certain important groups of func­tions that have been especially stressed by Seifert: Alert­ness, psychomotorics, impression of, and orientation in, sp~c:. Let me also mention the sense of time, which in my opinion plays an important role, too.

-~he ways how to investigate piiots' alertness, their ability to concentrate themselves, and the quickness to change. their attention from one object to another, have been given_ special consideration by Kirsch. A particular test to strain concentration has been developed by him, because, as i understand, conventional methods - like the Bourdon-test') - did not result in sufficient values of v_alidit_y. The same applies to other methods of investiga­tion, I 1 ke the Pau Ii-work-test, etc.

The Kirsch concentration test consists of a number of figures that are composed of brackets and added symbols like Plus, Mi_nus, Inverted Commas, Colon, Full Stop etc., :he l~tter being placed right or left of the brackets point­ing r'.ght ~r left respectively. Each of these figures has a certain value; the values of every two figures following each other have to be decoded from a tabula and summed up. The te.st, therefore, means to remember figures and to perfor_m si':'1pl~ additions. Seifert thinks this test of finding and digesting information to be quite suitable with regard to the assimilation of d t · · f' k · J . . . a a 1n an aircra t s coc pit. n my opinion, this applies in o far higher degree to the data­digestion at the control-desk of the ATC-service so that ~t least the Kirsch concentration test should be 1included in t~e controiiers' aptitude tests as well. Additionally, the strain on memory should be increased because especially controllers' decisions are based on their ability to store a rather lmge number of data. Therefore, a more intensive test of mental strain should be developed for this purpose.

. As for the _investigation of three-dimensional imagina­ti_on, the requirements regarding an ATC-applicant's effi­c1~ncy ~xce_ed those required from a pilot. Apparently orientation in space is based on information on the hori-

') According to "Controllers in Air Traffic", by J. H. Winchester, ,,Air Facts" - Monthly.

') Siegfried Fichtbouer (DVL), Untersuchungen zum Bourdon-Test im Roh men der Fliegerouslese. Physiologische Rundschou, Bond XI 1/3, 1961.

zontal and vertical planes and on the position in relation to certain fixed points and reference lines on the earth's surface. Relying on this sensation of space and on an orientation derived from it, a pilot will confine his navi­gation exclusively on himself; on an instrument flight, he need not calculate his relation in space to other aircraft (as he will do on a visual flight by means of his forward visibility). This duty is imposed upon the air traffic control officer who, by means of data primitively represented on his flight progress strips, has to develop for himself not only the same "egocentric" orientation in space as the pilot, but additionally the relation in space of individual aircraft to each other•).

I am therefore of the opinion that the new space- and symbol test mentioned by Kirsch is a first step into this direction, namely, to test an applicant's fitness regarding orientation in space. As this test, however, is said to have a rather small correlation of validity regarding aeronauti­cal judgement, it has to be further developed in order to be used in the controllers' aptitude tests. In this matter, apparently, a certain role is played by the unsolved pro­blems of psychological reasons for human efficiency in respect of space feeling and orientation.

Concerning psychomotorics I want to point out the following. According to Seifert, the backside-drawing-test has to be considered as unsatisfactory because of its vali­dity of 0,20. He points out that in an aircraft controlled movements, i. e. coordinated movements, are required fre­quently, but that normally there is no pattern to be fol­lowed. He mentions only the countermeasures against ab­normal attitudes or movements in reference to the hori­zontal plane.

This refers obviously to flying along radio courses. There is, however, quite a number of navigational pro­blems that require certain defined patterns to be followed, e. g. in Decca-navigation where using the flight-log means using a genuine backside-drawing procedure, and in fly­ing all those holding- and other navigational procedures, where in each specific case defined patterns in space have to be followed repeatedly. Obviously, this means to ac­complish coordination of predetermined movement. Al­though there is no direct relation to the controllers' tests, I thought it necessary to point out the items where my opinion is different.

In regard to psychomotorics in particular, I cannot ~ay_ much for the time being, as I am no trained psycho­og1st. I cannot answer the question whether those sensory

or t-.;~-hand coordination instruments- perhaps with some additional distracting irritation - are sufficient for con­trollers. Methods based on unrhythmical irritation. coming off with variable speed, and leading to overstra.in seem t b . ' . 0 e quite adequate, because they are equivalent to the 1ob done by a controller at his control desk.

It need not to be mentioned specia!!y, that all those

') Here the fact has lo be stressed again that complete pilot's training IS a prerequisite for the ATC profession. In principle, VFR-controllers should own at least a VFR-pilot's licence whereas all !FR-control personnel should have an !FR-pilot's ratin~. Apart from good physical condition, the following is required for employment as an ATC officer by the American FAA: 2 years' service as a military ATC-officer or 350 hours' flying time os a pilot, or '

21h years' practice as air/ground communicator.

tests that are being developed in regard to diagnosis of personality and breaking strain, will be doubtl~ssly of great importance for the examination of ATC applicants.

As a number of air traffic control officers will be trained and employed chiefly as Radar controllers, a special ability test in regard to Radar duty should be provided for. In my opinion, such a test need not be con­ducted right at the beginning, i. e. during the basic ex­amination, but more properly as a special assignment during the training period. Most conveniently, the problem should be dealt with together with the annual medical check-up, because here physiological and psychological overcharges effected through continuous Radar duty will be discovered, ond any special individual efficiency will be determined.

Finally, I want to say a few words about time-sense. In the United States the air traffic controller's job has been compared with a juggler's trick: Everything has to be kept moving in precise chronological order. This means that time-feeling is essential in ATC. This capacity is a natural endowment. It cannot be taught, but it can be trained and intensified, and then it will be kept and maintained like the ability of riding a bicycle. However, this capacity has to be kept "warm", as every controller will experience when taking up his job again after an interruption like leave. It will take him a certain running-in period to adapt himself to his normal rhythm.

To sum up: Without doubt, the present methods of screening ATC applicants require improvement when seen from a psychological view-point. It is rather unsatisfactory that these examinations are not held by a central autho­rity but by personnel of different ATC units. This results in considerable discrepancies in evaluation. The interview following the examination is conducted by ATC experts who are presided by a government's representative, but there is no psychologist with his scientific methods of ana­lysis present. As the training period is rather long and personnel is in permanent employment by government later on losses have to be kept to a minimum. Therefore, the results of the basic tests have to be as watertight as possible, and for this purpose the methods employed have to be made more objective. I believe that German con­trollers will fully agree to this opinion.

Much is to be said about the annual medical check-ups, but this does not quite seem to be the place. This 1s a matter rather for a physician specialized in labour safety provisions, who will have to i_mprove and intensify t~e check-up, which has to be considered as a mere farce in

its present form. I think that the prob!em of how to in­

clude a number of special psychological tests 1n these medical examinations is as important as the controversial question of how to evaluate colour-blindness, which may arise in the course of years, and whether to conduct a generally intensified ophthalmological inspection.

What I am driving at is that a well-compiled check-up is not only to eliminate e. g. Radar controllers becoming unfit for duty, which would mean a financial loss for them. On the contrary, it is rather meant to find out the causes of complaints and their consequences as ea1·ly as possible, so that a controller will keep his working capacity for a long time; if necessary, with certain medical or other re­

strictions.

7

Human Factor Analysis of Voice Communications i/

Practices in Air Traffic Control

The fol lowing summary of an extensive study has been reprinted with kind permission of the Federal Aviation Agency. The complete 321-page report was prepared by the Convair-Pomona Company for the Aviation Research and Development Service, FAA, under Contract No. BRD 44.

It presents the result of a survey of air communications from the standpoint of equipment utilization, procedures, and information flow. The major portion of this report is based upon radio and interphone communications recor­ded in air traffic control facilities at Miami, Florida. Both high and low density periods were studied and compared.

The report has been broken up into two parts. Voiume 1 contains a presentation of analyses and findings within four major areas of effort: communications equipment, communications intelligibility, communications procedures and practices, and operational system analysis.

Volume 2 contains a complete compilation of processed data based on a series of communication measures defined for the purpose of analyzing the Miami ATC complex. These data will prove useful in problems of system ana­lysis, automation, and simulation.

It is intended to reprint several parts of the report in future issues of "The Controller", because of the world­wide significance of the investigated subjects.

The editor wishes to express sincere thanks and appre­ciation to the Federal Aviation Agency for their support and cooperation.

An analysis of the voice communications system at the Miami ATC complex was based on recordings of a re­presentative sample of 12 positions in the Miami Center and all positions in the Miami Tower and International Flight Service Station. The total project effort included the following major areas of emphasis:

Analysis of Miami ATC voice communications.

Analysis of voice communications content.

Analysis of time-related voice communications measures.

Analysis of voice communications reliability.

Analysis of voice signal intelligibility in ATC.

Analysis of voice communications procedures a. practices.

Analysis of voice communications equipment.

The Miami data provided (1) a sound empirical descrip­tion of the voice communications process in representative ATC facilities, and (2) provided a basis for integrating the finding of the major task so as (3) to permit the formula­tion of operationally oriented recommendations.The major findings are evident in the following list of conclusions

and recommendations.

l. Traffic flow is not significantly affected by variations 1n voice signal intelligibility because experienced, well­trainecl controllers can cope with poor signals. However, effort should be devoted to improving signal intelligibility

8

to aid in reducing the drain on controller attention and energy, to increase controller comfort, and thus to provide a higher system safety factor. Specific recommendations include:

Formulate policy to permit assignment of relative im­portance to system needs in order to compute payoffs accruing from investments in equipment techniques ver­sus those resulting from procedural techniques.

Institute a program for improving communications ef­fectiveness using the class of techniques indicated as optimum with respect to the above policy.

For highest return on investment, place major emphasis on procedural techniques such as:

Build "controlled redundancy" into phraseology and increase message expectancy:

Position reports should be made by first giving present fix and identification to direct a controller's attention to proper bay and strip with a minimum of searching.

Specific words should always be associated with a given control instruction. For example, "climb to" and "cruise at" could always be used in instructions to climb, deleting the present "and maintain". Then, "de­cend to" and "and maintain" could be retained for descents.

Associate verb tense and control instruction. For ex­ample, one might always use future tense in advisories, as in "your traffic will be ... ", and always use the participal form for runway identification, as in "land­ing on runway inner right".

Develop a phonetic system of number designators or else use letter call signs for aircraft instead of the pre­sent numbering system.

Eliminate those required procedures which satisfy no system need (so long as no legal requirements are in­

volved).

In general, rewrite present standard phraseologies to maximize expectancy by structuring the phraseology to correspond with the sequence of actions required.

For increased controller comfort, improve signal qua­lity with equipment changes and modifications such as:

Provide controllers with noise-cancelling microphones. Provide controllers with headsets for both quite and noisy environments. The former should be comfortable light-weight, and of the hearing aid type. The latte; must provide both comfort and ambient noise attenua­tion. Both types must be capable of reproducing 120-db sound levels without exceeding a 100% distortion level and should have a frequency response of 200 to 6000 cps.

Provide peak clippers with a level adjustment (120 db maximum) available to each user of a headset to en­courage the use of higher gain levels when pilot trans­missions are weak, and to give hearing protection.

I I

Initiate action to obtain adequate legal specifications to cover pilot microphones and earphones.

In general, institute a program to improve transducer quality from the standpoint of fidelity and user com­fort. Evaluate future frequency requirements and explore bandwidth compression techniques for application, if required.

If increased channel capacity is required, investigate the hybrid combination of the vocoder with multiplexed single-sideband propagation.

Reduce mutual interference (or "feed-through") through careful antenna siting and equipment location.

Investigate and.monitor multicoupler development for implementation possibilities.

Provide the controller with a break-in capability so that impending incidents can be more easily avoided, repetitious communications can be terminated, imme­diate verification can be obtained when needed, and congestion can be more adequately handled.

Institute closer liaison between FAA engineers and users in the field.

Provide increased local option for minor equipment purchases when standard equipment is not suitable or satisfactory, pending standard replacement.

Provide increased emphasis to the application of human engineering principles in equipment design, to include consultations with users in the field.

Streamline the procedures for evaluating equipment modifications made in the field. Both national and regional evaluations should be made simultaneously so that negative regional evaluations will not prevent evaluation in Washington.

2. The proposed program should be supplemented by the following training considerations:

Provide speech training to all controllers during initial training.

Continue speech training at the local level with a con­tinuing program wherein each controller is required to listen to a recorded sample of the transmission he makes during both high traffic density periods and periods of very low traffic density.

Make provision for remedial speech training at the local level by providing adequate speech training lite­rature and recordings.

Provide speech training for designated personnel who will evaluate the speech of other controllers.

Emphasize the need for careful enunciation of numbers and fix names.

Emphasize the need for added care when handling military and general aviation aircraft. In particular, note the need for relatively slow and clear instructions to pilots not familiar with the local area or ATC pro­cedures.

Establish liaison with military training authorities to ensure that pilots will be aware of UHF signal deficien­cies which require careful speech and good enuncia­tion.

Make wide application of a simple and remarkably effective device (Designed and fabricated by a Miami Tower controller several years ago) used in the Miami Tower which permits an instructor to over-ride a trai­nee's communications at critical points or when an error has been made. The device is presently used at the local control position and permits training during peak traffic conditions from the very beginning of training.

3. Communications effectiveness can be further enhan­ced by reducing facility ambient noise levels as follows:

Facilities, and centers in particular, should be sound­proofed as much as possible through the use of acoustic tiles, acoustic floor coverings (where feasible), and draped walls (in centers and stations).

Emphasize the need for sound-deadening acoustical properties in the design of new facilities.

Encourage the use of interphone and visual coordina­tion to discourage shouting in centers.

Encourage soft-voice speech in all facilities to avoid speech volume "competition", particularly during high density periods.

Eliminate loudspeakers wherever possible.

Teletype machines should be placed in insulated cover boxes or behind insulating barriers.

4. Additional research programs which will provide a good payoff on investment and/or which will provide needed basic data for planning include:

An analysis of the signal quality of ground transmis­sions in the air environment.

The formulation of a generalized articulation index (or signal quality index or intelligibility index) which will include the effects of distortion, type of material transmitted, expectancy, and experience, in addition to the effect of noise. Such an index would provide o unique means of specifiying equipment characteristics in terms of man-machine measures - i. e., in terms of operational user requirements.

A definitive study of the effects of the continuing stress and ambient noise levels associated with the control­ler's job should be mode by the Environmental Health Division of the Office of The Civil Air Surgeon.

Extension of the DIN concept for the purpose of pro­viding more detailed planning data for the evaluation and design of automated systems. This program should include recording small data samples at about five high traffic density complexes.

A program to determine the relationships between air­space saturation, communications saturation, and con­troller saturation as a function of route structure, fre­quency utilization, human factors, etc.

Research into the factors necessary for success in con­trolling air traffic, to include adequate testing, o care­ful multiple-factor analysis, a sound program of valida­tion, and the development of o set of realistic criteria for personnel selection.

9

Air Traffic Control in the Netherlands

Although Air Traffic Control is being conducted in accordance with uniform rules and regulations - i. e. !CAO Standards and Recommended Practices - in most countries, a number of individual particularities exist, especially in regard to civil/military coordination, control in the upper airspace, etc. Therefore, it is considered an interesting programme to run a series of articles

Air Traffic Control in IFATCA Member States in our Journal.

We plan to use a certain frame as a basis for each article, the details of which will probably be discussed at the 1962 IFATCA Annual Conference in Paris.

The following report has not yet been prepared along this line. However, it constitutes a iiveiy review on the development of Air Traffic Control in the Netherlands after the war. We reprint it with kind permission of the Netherlands Guild of Air Traffic Control Officers, which published this article in the last issue of their excellent journal SCANNER. . .

The editor, at this occasion, wishes to express his sin­cere thanks for the cooperation and the encouragement offered to him.

Area-Control in the Netherlands after 1952

The reason that 1952 was chosen as a starting point for this short survey, is the foct that in this particular year some important change in the procedures for Air Traffic Control in the Netherlands took place. Until then, the Netherlands Control Area consisted of the area that now constitutes the FIR and the representation of the air traffic in this area was done by means of the time/distance dia­gram. Looking back on those days, we can only feel ad­miration for the people who made this system work so surprisingly well. It certainly was no simple task ~o ~ro­vide Air Traffic Control in an area with few rad10-a1ds, where most of the accurate fixing had to be carried out in telegraphy by the DF stations of the Amsterdam centre. One of the standard message addressed to Amsterdam by aircraft entering the area read: "Will you accept control?" and naturally always an affirmative answer was given. The consequences of this responsibility were most apparent during the Berlin air lift, when the amount of traffic between the U.K. and Western Germany reached unknown heights. The development of the Netherlands Air Fo1·ce and the demands for military air space (by 1950 nearly all local airfields used for domestic KLM service.s had been taken over by the Air Force) made a fully posi­tive control in a responsible manner in the Netherlands Control Area virtually impossible. Of course, there was always the magic instruction: "maintain VFR'', that, when confirmed made the controller relax, but it was generally felt as a ~ign of impotence in controlmanship, when one had to revert to this last resource.

A system with specified routes, marked b'.. radio aids as compulsory reporting points and clear of m1l1tary areas, seemed the only solution, and the Netherlands Con.trol Area ceased to exist as such and became a mere Flight

10

Information Region in which the airway system was intro­duced, geographically very little different from what it is today. The upper limit was 15000 feet, which 10 years ago was considered sufficient for the civil air traffic of those days. The only radio aids were NBD's, which did not always assure too accurate a navigation, but the air­ways were wide enough to allow for 5 miles drift on either side of the centreline.

After some time various NDB's were supplemented by VOR-stations and as in the course of ye.ors more and more aircraft were fitted with VOR equipment, track guidance along the airways became quite accurate.

The implementation of airways called for a rapid means of direct communication between controller and pilot. It was here that radio-telephony proved a necessary and integrated part of an efficient airway system. In this respect it is quite remarkable that in the early days of civil aviation, radio communication between aircraft and ground stations was carried out on MF radio-telephony, to be replaced after some time by MF and HF radio-tele­graphy. After many years, radio-telephony, in the perfect­ed form of VHF, regained its place, which is now so im­portant that present day air traffic control is unthinkable without R/T.

With the termination of WIT as a means of communi­cation the medium frequency-OF service came also to an end. It was replaced by automatic VDF, situated at various positions and working on the airways frequencies. The controller was now able to get an idea of the relative positions of aircraft by a mere glance at the various VDF­clocks during the time aircraft were giving routine mes­sages, while it aiso made a check on reporting points possible. The automatic VDF proved to be a valuable means of identification when in 1953 the search radar was introduced. This 10 cm radar equipment, first on experi­mental basis, soon became a welcome means to observe airways traffic and appeared to be in many cases a very useful aid to navigation. In combination with VDF bear­ings for identification, this radar system proved quite reliable and after some time it resulted in a considerable improvement to expedite in- and outbound traffic. Air Traffic Control no longer had to wait for opposite traffic to check passing the same reporting point, for within a radius of nearly 100 km around Schiphol, the controller could actu­ally see when aircraft were clear of each other and even effected sufficient separation by instructing aircraft to turn on a suitable heading. This resulted in a very speedy and efficient handling of traffic. Holding en route and level­ling off during climb or descent- until then normal proce­dures - were reduced to an absolute minimum. Inbound traffic could be radar-checked for position and speed, which resulted in a better prediction of the approach sequence. Overflying traffic could be observed clearing the holding area, so traffic in the holding stack could be released for descent. Yet, this 10 cm search radar was a specific terminal radar and proved most effective on the 30 miles range. It was therefore modified and made suit­able for simultaneous use by approach control and air­ways control. This resulted in a still more efficient hand-

r

ling of inbound traffic and a closer cooperation between the two units.

With increasing speeds and higher cruising levels of aircraft, area control began to notice the limitations of the 1 O cm radar and the appeal to the Netherlands in­dustry met with response: Philips developed an air route surveillance radar with a range far beyond the lateral boundaries of the airways and a coverage in height suffi­cient far the civil jet liners that would soon come into service. The main equipment was built by "Philips Tele­communicatie lndustrie" at Hilversum. The huge antenna system was designed by "N.V. Hoiiandse Signoal Appa­raten" and constructed by the Fokker Aircraft Factory. Various other Dutch firms contributed to the completion of the equipment, while Marconi supplied the only com­ponent parts of foreign origin: the 15 inch amber coloured displays with video mapping and CRDF.

At the end of 1959 the airway surveillance radar was in full operation and ready to meet the ever increasing demands of jet traffic. All aircraft in controlled airspace could now be provided with radar control and one of the fundamental demands of air traffic control, namely to maintain a safe and efficient flow of air traffic, could now be fully satisfied, especially as far as efficiency was con­cerned. The airway's upper limit however, no longer cover­ed the operational levels of the aircraft types that had come into use. Jet aircraft and even turbo-props demand­ed cruising levels far above the 15000 feet limit and so the airway upper limit was changed accordingly. The actual airway was lifted up to 20000 feet, while on top of the airway predetermined routes gave the same control fa­cilities up to 25000 feet.

The need for more airspace, however, was not restrict­ed to civil air traffic. Military traffic demanded large areas for climb-out, descent and holding procedures and various levels in the predetermined routes had to be placed at the disposal of military aircraft, often for a considerable time. The result was that civil aircraft could only make limi­ted use of the newly acquired air space, urgently needed in order to operate economically. This situation still exists today and it goes without saying that it would make pilots and controllers a lot happier if some solution could be found to make ail required levels available at al! times to all civil aircraft designed to operate at such levels.

With the increasing airspeeds, the controller was faced with the problem of analysing and predicting traffic situ­ations in an ever shorter time. It was generally recognised that it would considerably lighten the controller's task if a means was found to aid him in the clerical work and which would provide him with an accurate forecast of the traffic situation at any given moment. The answer was given by the electronic industry: Hollandse Signaal Appa­raten introduced its automatic air traffic control system. This system was planned in three phases: the first phase which reduced clerical work to a minimum and automati­cally produces data on printed strips, has been in opera­tional use at Schiphol for some time. Phase two will bring automatic flight progress boards, with automatic display of flight progress data. It is planned to have this second phase on operational test some time this year, so 1962 may well be another importani'·year in the history of air

traffic in the Netherlands. Ten years of steady development in area control may

be concluded with probably the most important happen­ing since the airway system was introduced in 1952.

May the next decade be marked by a continuous in­terest in air traffic control by the industries that can contri­bute so enormously to its further development.

Schiphol approach One day in 1955, time 20.00, the following instructions

were passed to an inbound aircraft "PHLKN this is Schi­phol Tower, Roger, maintain 7500 feet to OA beacon ex­pected approach time 20.45, you are number 7 in traffic for runway ... etc".

After receiving this message, the captain of the Super Constellation PHLKN was fully prepared to join holding pattern ond would have been quite happy to make a landingtime af about 20.50. He knew he would be cleared down in six successive steps to the final approach altitude of 1500, while holding in the OA-stack. Runway 23 was the only instrument runway, approaches under instrument me­teorological conditions for all runways were initiated with an ILS approach on 23, if necessary followed by a circ­ling procedure if the wind was unfavourable for using 23. Approach times were arrived at by simple arithmatic: the lowest aircraft to enter the terminal area was number one to approach, and 6 minutes were added as standard landing interval for the next higher aircraft to enter the TMA, regardless of speed and other flying characteristics. Within the lateral boundaries of the TMA only vertical separation could be used for inbound traffic converging on the holding beacon. Thus an aircraft sometimes had to hold to wait for another aircraft to arrive over the beacon and make its approach, simply because the other aircraft occupied a lower altitude upon entering the TMA. Th is was approach control as performed, in accordance with internationally laid down procedures, which still apply today. It was carried out like this for years and still is in many places all over the world. For low traffic density this is perfectly acceptable and safe, but for efficiency, when traffic builds up to a rate of more than 8 or 10 air­craft per hour, this system imposes severe penalties on the budget of airline companies. Let's therefore make a com­parison 6 years hence.

On a day in 1961 the following message could be overheard:

"KLM 644 this is Schipho! Approach, turn right heading 160, descend to flight level 65, you are number 7 in traffic, PPI approach for runway 06, there is no delay". The cap­tain of this DC8 is preparing for a hectic 8 to 10 minutes, in which he will be radar-vectored through other traffic to the runway in use, loosing height at a steady rate of descent, he will be reminded to perform his cockpit check and be given heading and distances to touchdown on final approach until he reports "Runway in sight" - in most cases adding: "Thank you very much"! Compared to the obovementioned Superconny, the DC8 has saved approxi­mately 40 minutes precious flying time in the holding pattern and that is just one of many aircraft, making their approach and landing without delay. The landing rate on

. . . . .- - . ft any one runway is increased to approximately :L'.J .a1rcra. per hour, direct approaches are normal and delay is ~egli­gible. This change has been brought about. by the intro­duction of radar to approach control. With the intro­duction of the airways system in September 1952, the task of Approach control was split up between the Area Con­trol Centre Amsterdam and Sch iphol Tower, the latter only being responsible for handling inbound traffic released to it by ACC in a given sequence on course to, or over

11

-

the holding beacon. Spacing of outbound aircraft was effected by time separation on take-off, determined by ACC. Conflict between in- and outbound traffic was met by doglegging outbound traffic until it was clear of or on top of the aircraft in the holding, consequently inbound traffic in those circumstances was released over the hold­ing beacon.

Fortunately Schiphol-traffic in any one period was most­ly confined to either inbound or outbound traffic, which simplified the situation enormously. Delays in approach or on take-off were accepted as a matter of fact.

The only radar equipment available was a Precision Approach Radar, believed to be the first one built on a permanent site and yet capable of serving different run­ways, by turning the complete PAR hut on its basement. (CFTH)

In 1953 a General Electric ASR 2 surveillance radar was installed. Controllers were trained in England, first on PAR fol lowed later by a traffic directors course. The first ope­rationa i trials on the search radar in 1954-55 were merely training circuits, lining up aircraft for final approach on ILS or PAR. This already speeded up traffic by eliminating procedure turns and sometimes holding patterns. Learn­ing on the job the controllers enjoyed experimenting with their new equipment. After some time simple procedures were approved by the department of civil aviation, radar separation was introduced and by summer 1957 sufficient controllers had been trained and procedures worked out to iet traffic benefit fully from radar-vectoring. Unlike the development in other countries, emphasis was laid on ex­pediting inbound traffic, most probably because the Tower, to which the Director was operationally attached, could not influence clearances given by ACC to outbound traffic.

In September 1957 a completely new unit was intro­duced, the separate Approach Control Office. The Ap­proach Controller, although equipped with a radar display, was intended to work basically as procedural controller, radar-vectoring should be left to the director. In practice however, the approach controller soon became his own no. 1 director, effecting the initial approach sequence by applying radar separation, leaving the final line up on ILS to the Director, who also conducted PPI approaches to non-instrument runways.

At the same time Amsterdam Control was equipped with ASR 2 consoles: the effective range of this equipment is only about 50 NM, whilst the radius of the TMA is about 30 NM. The ASR2 at the ACC unit proved useful for hand­offs to APP and for the coordination of outbound traffic in the TMA between the two units.

The two surveillance radar displays for approach con­trol were enormously improved by the replacement of the original 1 O" (green)tubes with overlaymaps, by Decca 12" (amber) tubes with interscan facilities for a pair of run­way centrelines, a distance and bearing line and CRDF.

In the last four years Schiphol Approach has become an indispensable link in the Air Traffic Control setup. Pro­cedures have been developed for coordination between APP and Amsterdam Radar; this coordination has greatly increased since the Philips Long Range Radm was installed a\ the area control centre. At the present time outbound as well as inbound traffic benefits from the efficient use made of the existing radar-equipment. Outbound traffic is mainly routed directly to the transferpoints on radials from the airport-VOR. The procedures for inbound traffic

12

are very flexible, mainly consisting of continuous radar guidance from the transferpoints, steering clear of out­bound traffic and using radar-separation to effect an effi­cient landing-sequence. Normally the holding beacons are not used, except in marginal weather conditions when some aircraft may try to land, whilst others prefer to wait for weather improvement. Even in those conditions radar proves to be of great help to identify aircraft in the hold­ing, who wish to make an approach; after identification such aircraft are routed clear of the holding traffic to the final approach of the instrument runway in use, without necessity to divert traffic below its level to another beacon. Serviceability of the equipment is extremely good, but no amount of care by the technical staff can overcome the clutter experienced in conditions of heavy precipitation. In those rare instances when the scopes are completely cluttered no radar control can be given, and it is then that aircrews and companies notice the effect on operational efficiency. Hundreds of hours of flying time are yearly saved by the efforts of the controllers, for no matter how good the equipment, it is the man behind it who translates the movement of blips into moneysaving moves of the traffic under his control.

What about the future? If traffic is going to build up to more than 25 inbound aircraft per hour, the present flexibility cannot possibly be maintained due to the human limitations of the controller and the limited airspace in the TMA. Most probably off-centreline holding techniques will then ?e. used to effect the most efficient landing sequence. The l1m1t of movements per hour will be dictated by the m1n1mum allowable distance between aircraft on final, which in turn depends on the runway-occupancy time, which at present is an average of 11;, to 2 minutes. With the possibilities of the new airport now under construction, (parallel runways and high speed turnoffs) this time may well be ~educed to 1 minute. In practice this may increase the landing rate to about 40 aircraft per hour.

. !n about 1965 the new terminal area at Schiphol airport will be ~ompleted. The ATC units will then probably be housed 1n a modern building, with due attention being given to future developments.

The move from the old tower to the new building will coll for a good amount of improvisation and most pro­bably for. completely new equipment to replace the pre­sent terminal area radar, which may afterwards be used as. stand-by. Specifications for this new equipment are being worked out. It will certainly need greater height coverage t.han the present ASR2 (10.000 ft), effective anti­clutter devices, MTI without the handicap of blind speed, and probably a greater range whereby it can serve as stand-by for the Long Range Radar. Would it be too much to hope t~at this equipment be fitted with daylight scopes? And that 1s does not produce low or high frequency sound­waves and a lot of heat which is circulated in the control­room? These are the most disturbing il!effects of radar on controiiers; if these can be cancelled out, they will pro­bably be able to handle more traffic more efficiently, with less fatigue and eyestrain. In the few years of its existence "Schiphol Approach" has earned itself a very good name with pilots of al! companies frequenting our airport.

The many sincere "Thank you"s from pilots reporting the runway in sight are becoming a matter of routine but would'nt we miss them if no longer given? '

May "Schiphol Approach" continue to deserve the grati­tude of all aviators who avail themselves of its services.

Sensitive Aircraft Altimeter E. Roessger and G. Raenike

with Linear Subscale calibrated in Values of Altitude Units

(Brief comprehensive report from the Institute for Pilotage and Air Traffic, Technical University Berlin)

Nowadays, the subscale of a sensitive aircraft altimeter is of logarithmic kind and calibrated in terms of pressure units.

At the Institute for Pilotage and Air Traffic, Technical University Berlin, a sensitive aircraft altimeter was deve­loped the subscale of which is linear and calibrated in values of altitude units.

A report (in English and German languages) about this instrument has been published by the Director of the Institute, Professor Dr.-lng. Edgar Roessger [l].

In this report the system used at present of long dist­ance flights on flight levels and of take-off as well as landing by QNH altitudes is explained on basis of nume­rical data .

Moreover, the usual method of indicating the amount of vertical displacement of the calibration curve of a baro­metric altimeter in the altitude-pressure diagram by pres­sure values is described.

Then it is shown that there exists also another simple way of indicating the amount of the vertical shift of the calibration curve by values of altitude. Finally, some methods as well as indicators and slide-rules for ascer­taining of special subscale values which are analogous to the QNH are stated.

The followi ng rule is valid for obtaining the amount and correct sign of the subscale pressure value of a cur­rent altimeter after a vertical shift of the calibration curve re lat ive to the ICAO Standard Atmosphere is carried out by turning the adjusting knob :

When the calibration curve lies by the altitude H be­neath the ICAO Standard Atmosphere in the altitude­pressure diagram then the pressure reading , corre­sponding to the altitude + H (plus H) from the ICAO Standard Atmosphere is to be read off the subscale . When the calibration curve lies by the altitude H above the ICAO Standard Atmosphere in the altitude-pressure diagram then the pressure reading, corresponding to the altitude - H (minus H) from the ICAO Standard Atmosphere is to be read off the subscale.

On the other hand, without any difficulty it is possible to characterize the amount and sign of the vertical shift of the calibration curve with respect to the ICAO Standard Atmosphere not by pressure values but directly by that altitude value which equals the amount of vertical shift in the altitude-pressure diagram .

The following rule for obtaining the amount and cor-rect sig n of the subscale altitude reading is valid:

When the calibration curve lies by the altitude H be­neath the ICAO Standard Atm os phere in the altitude­pressure diagram then the altitude reading - H (minus H) is to be read off the subscale. When the calibration curve lies by the altitude H above the ICAO Standard Atmosphere in the altitude-pressure

Fig . 1.

' -0-0

Convent iona l subscale calibrated in pressure un its (mb).

0 -:;;;

Fig . 2. Subscole calibrated in altitude units.

Fi g . 3.

A lti tude units anal ogo us to pressure units o f Fig. l ore cor re­

spond ing to ICAO Standard Atmosphere, bu t eng raved wi th

opposite signs.

ETIJ •cd

D ·s•oon .

Subsco le corresponding to Fig . 2 but w i th al t i tud e units the

sig ns of w hich dist ing u ished by th e colour gree n for posi t ive

and red far negative va lues respectivel y

13

--

diagram then the altitude reading + H (plus H} is to be read off the subscale.

As the positive or negative signs conveyed by HF or VHF radio telegraphy or telephony could, under circum­stances, be either mixed up or lost, it is advantageous to substitute positive and negative signs by green or red colours, respectively').

Fig. l illustrates the subscale of a current aircraft alti­meter {non-digital subscale, calibrated to pressure values}.

Fig. 2 illustrates the subscaie of an aircraft altimeter calibrated in terms of altitude units the signs of which are characterized by + (plus} and - (minus) respectively.

Fig. 3 finally illustrates the subscale of an aircraft alti­meter calibrated in terms of altitude units the signs of which are characterized by the colours green or red re­spectively.

Only for simplification of drawing in Figs. l, 2, and 3 the subscales extend over a smaller angular range than the usual 360°. ·

The following are the advantages of a subscale cali­brated to altitude readings:

l. Linearity of the subscale resulting in a sim:1lified con­struction of the altimeter and eliminating the compli­cated and expensive logarithmic distorting mechanism of digital subscale altimeters. Consequently, it is not difficult to get a subscale, having a range from+ l OOO m to -5000 m which could be read off with an accuracy of ±0,5 m (corresponding to 0,05 mb}. Using this type of altimeter, it is possible, independent of the airport elevation and of meteorological conditions to land and to take-off by the QFE (altimeter needle indicates air­port elevation as 0 m) and QNH methods (altimeter needle indicates airport elevation as H,.i) 2).

Such an altimeter (with digital altitude calibrated sub­scale and a 1 :1 ratio linear translating gearing) could possibly lead to a renaissance of the QFE method, as the disadvantage of malfunctioning at high situated airports is obviated. The calibration of a non-digital subscale in altitude readings has neither advantages nor disadvantages in reading range and reading accuracy because the scale circumference is 360° in either case. As the digital subscale altimeter is a newcomer on the market, and as most of the present altimeters have non-digital sub­scales, the apparent (from the viewpoint of the instru­ment designer) advantages in the method of calibrating the subscale to altitude values has not invoked any interest, up to now. To carry out the above mentioned method with a non-digital subscaled altimeter, it is only necessary to change the subscale, the whole other constr"uction is not to be altered.

2. The subscale reading renders a clearer interpretation by the pilot. The subscale reading -50 m (red 50 m) perhaps signifies a system of flight levels that lie 50 m below the system of QNH altitudes. As the QNH alti­tude approximately equals the altitude above mean sea level, a long distance flight with a subscale setting O m

'I In ever·yciay life red numbers signify negative values, too. The blue/ yellow colou1· combination does not come in question, as it is used for the Instrument Landing System (ILS). -

1 1 The QFE method is therefore known as "Lero method" and the Q"JH method as ,.elevation method"

14

corresponds to a QNH altitude of 50 m less than that indicated by the altimeter. The essential disadvantage of the pilot having no proper knowledge of his actual terrain clearance while flying in flight levels is in this manner ruled out. The pilot must only add the subscale value. to the flight level reading (pressure altitude) to get his actual QNH altitude. In the case of subscale reading -50 m = -164 ft he gets HQxrr = pressure altitude -164 ft. With a subscale setting 0 m in a long distance flight the pilot attains a knowledge of his QNH altitude as :veil as of the tendencies of the changes of the same in a greater area. It is only necessary to obtain the QN~ analogous readings - (QNE - Hci}. When the readings are increasingly negative, the logical con­clusion is that the flight levels are stacked further and further below the QNH altitudes, i. e. the aircraft ap­proaches a low pressure region, and extra caution is called for, as the terrain clearance diminishes. In this case,. permission to seek a higher flight level should be obtained from Air Traffic Control. Consequently, the old pilotage axiom of flying into a low_ pressure region is dangerous, is a logical and obvious conclusion.

3. The ph.ras.e "altimeter setting -50 m (red 50 m}" per­haps s1gn1fies to the operators in Air Traffic Control, that aircr~ft flying the flight level system approach the QNH altitude controlled aircraft and the ground by 50 m. On the other hand "altimeter setting +50 m (green 50 m)" signifies that flight levels withdraw from the syste~ o~ the QNH altitudes and the ground by 50 rTI_· This kind of altimeter settings render the Air Traffic Controller a vivid picture of the relative vertical position of aircrafts in the airspace controlled by him.

Flight Captain Willibald Part! of the Deutsche Luft­hansa ~.G., Hamburg, earns the merit of being the first, ~ccording to the authors' knowledge, of bringing atten­t~on to and making suggestions [2] for the above men­tioned calibration of the altimeter's subscale in altitude values.

Naturally, there is a lot to be done for this method of subs~ale calibration - which has many advantages -to displace possibly the present system. The change would hardly flounder on technical or economical dif­ficu!ties. a~ the instrument with non-digital subscale o~dinarily in use today, need only a change of subscale without any altering of the main construction.

* The aut~ors wouid appreciate any kind of suggestion, critic, and remarks concerning the ideas laid down here. - Please address your letter to:

Bibliography

Professor Dr.-lng. E. Rof3ger, Technische Universitat Berlin

lnstitut !Ur LuftfahrzeugfUhru0ng und Luftverkehr, (l) Berlin-Charlottenburg 1, Ma rchstraf3e 12-15

E. Roessger (Editor), G. Raenike

Contr!bu.ti~~s. to Aircr~ft lnstrumentation, Some Remarks concerning the Possrbrlrtres of Calibrating the Subscale of an Altimeter in Terms

of Altitude, Report Na. 62/1, Institute for Pilotage and Air Traffic, Technical University Berlin, Berlin-Charlottenburg, March 1962

W. Partl

Why do we not have QNH-Seitings in Feet? (Deutsche Lufthansa, Hamburg, 6. Dez. 1960)

PROJECT BEACON Evaluation and Summary

The Project BEACON report hos been widely discussed on oil levels and by o great variety of users.

The following is a comment by the Air Traffic Control Association published in the ATCA Bulletin and reprinted with kind permission of it~ editor.

ATCA's Executive Director attended the user symposium BEACON held in Washington March 5-9. Spear-headed by Mr. Al Brown of the FAA Systems Design Team, the meeting gave users an opportunity to make informal com­ments on Project BEACON. On request, ATCA's comments w~re made available to the Design Team for its study prior to the symposium. An invitation has been extended to the Association to work with these committees, and recommendations are solicited on a continuing basis.

Mr. Richard R. Hough and his BEACON task force pro­duced a report that should prove of value to the Air Traf­fic Service in the years ahead. Any traffic controller can find faults with the report from the standpoint of practical application, but the real goal of the Task Force was to develop broad guidelines. It is also important to note that President Kennedy, in his instructions to Mr. Halaby, asked the FAAAdminstrator to "begin at once to carry out those recommendations of the report which you believe will move the airways program forward rapidly and effi­ciently." The BEACON report is not a mandate. It is a guide for a system to be implemented within the realm of pr.a~ticality. Mr. Hough's committee was helpful in d~scrib.1ng as futuristic certain programs being pushed with h 1gh hopes for a breakthrough to solve the ATC problem.

In addition, the Task Force lent authority to those op­posed to the use of the SAGE system for air traffic control. It pointed out that the system was not economicolly adapt­able to long-range planning for the job. They did recom­mend the use of ADC radars as an integral part of the FAA system. A sense of direction in planning for the ATC system was contributed by the group when it recognized that planning is a continuous function not adequately served by high-level committee reports. The Task Force also recognized that all planning for system improvement has to be funneled through one group to insure compati­bility.

Establishment of the Systems Requirement Division (AT-40) within the Air Traffic Service by Mr. Halaby is expected to insure compatibility during work on the ope­rational part of BEACON implementation. The Systems Design Team has been established within the Aviation Research and Development service. Between them, these two teams have the responsibility of carrying out Project BEACON, within the realm of reality, under Mr. Halaby's

direction. An analysis of Project BEACON was written by a work­

ing group in the FAA headed by Ed Barrow. Others in the group were L. I. Pierce, George Robertson, Bob Martin, Charles (Red) Stephenson and Jack Wubbolding. Their re­port proposed a course of action to implement BEACON. The group was permanently established as AT -40. Excerpts from the analysis are printed below. Presentation of this material is for educational purposes and does not re­present the position of the Association on the technical

problems involved.

SECTION 1:

Summary, Project BEACON Recommendat" S . . . ions cope: The purpose of this section ;s to summarize, as briefly as possible, the air traffic control system concept which was recommended for adoption in the reports submitted b th Project Beacon Task Force. In this section we h y te , ave a -tempted to describe the Beacon REPORT system c t . . oncep s and philosophy 1n the broadest possible terms and to make b.rief comments as appropriate. We have also listed the ma1or recommendations of the Task Force.

For simplicity and clarity, the Project Beacon Task Fo · REPORT wiii be referred to hereafter as: the REPORT.rte

Organization and Utilization of Airspace: The REPORT e~visi?ns an AT~ system based on the philosophy of eli­mination of the see-and-be-seen" concept wherever pos­sible and required. In broad terms, the concept advanced in the REPORT would organize the airspace so that high performance and/or high density traffic would operate in a positive separation environment, to the maximum ex­tent possible, without imposing undue operational re­strictions on any user. A positive separation environment is one in which all aircraft are provided with separation by the ATC system and see-and-be-seen separation eli­minated.

The REPORT calls for the establishment of a positive separation area throughout the conterminous U.s: above 14,500 feet MSL, except over mountainous terrain, where the base of the positive separation area would be 24,000 feet MSL. In addition, certain heavily travelled airways below the base of the positive separation area would be designated as positive separation airways. A positive se­paration environment would also be established in the airspace around major terminals.

In the remainder of the airspace, the see-and-be-seen concept of separation would be permitted; however, safety would be enhanced by increasing the present VFR visibility minima and by establishing a speed limit in airspace con­taining a high aircraft population.

Finally the REPORT recommends that most of the lowest stratum of airspace, from the surface to 3,000 feet above terrain, be reserved exclusively for uncontrolled (VFR) traf­fic, except around terminal areas. In this airspace IFR flight would be prohibited and al! traffic would operate within an established speed limit.

Controlled Visual Rules: In its advocacy of the elimi­nation of see-and-be-seen flight and in its organization of the airspace to that end, the REPORT follows closely the concept of the FAA positive control program. However, the REPORT introduces an innovation to positive control by proposing that the system provide positive separation to pilots not qualified for IFR flight. Such pilots, main· taining aircraft attitude visuaiiy, but being separated by the ATC system, wou Id operate under a new category of flight rules, in addition to and distinct from VFR and !FR. This new category would be termed Controlled Visual

Rules (CVR).

CVR - Positive Control vs. Positive Separation: I nas­m uch as the concept of CVR is extremely important in analyzing the REPORT recommendations, it would be well to outline the difference between positive control of air

15

traffic as practiced today and positive separation ~s pro­posed in the REPORT. In this regard, there are sections of the REPORT wherein the term "positive control" is used; however it is used with a different meaning.

Positi~e controlled airspace in today's system is air­space where traff1c is controlled in accordance with Spe­cial Civil Air Regulation (SR) 424C. In the two types of positive control routes and positive control areas SR 424C prohibits VFR flights and requires among other things that:

1. All pilots be \FR qualified;

2. All aircraft be !FR equipped.

In the positive separation environments envisioned by the REPORT, these two requirements would not hold true. The VFR pilot of today could operate in the positive sepa­ration environments proposed in the REPORT provided he could meet certain airborne equipment requirements. In so doing, he would operate CVR. VFR (uncontrolled) flight would be prohibited in positive separation areas.

Thus, the two concepts, positive control and positive separation, are similar in that each eliminates see-and-be­seen separation, but vastly different in the pilot qualifi­cations required for operation in the ATC system. The philosophy behind the REPORT recommendations is that the system should provide positive separation to all pilots, including those not qualified for IFR flight, provided the pilot has the necessary airborne equipment to participate in the system. On the other hand, the REPORT's recom­mendations concerning the organization of the airspace allow ample room for VFR (uncontrolled) flight by aircraft not equipped for CVR operations or by pilots who do not desire to participate.

ATC Equipment Environments and Control Information Source: The ATC ground environment proposed in the REPORT would be automated with computers linking all enroute facilities. The computers would take over the bulk of the "bookkeeping" duties and would be the source of appropriate information to aid the controller.

The primary source of air traff1c control information would be raw radar and radar beacon data displayed to the controller on a display which would also present alphanumeric data. The alphanumeric data on a parti­cular aircraft would be normally correlated or associated by the controller with the appropriate video return. The radar data would be displayed raw, in contrast to a system in which radar and beacon returns are computer-processed and then displayed as symbols.

In order to attain the positive separation environment, the REPORT makes specific recommendations with regard to the requirement for airborne radar beacons which will have not anlycade capabilitybutalso an altitude reporting feature. In addition, instantaneous discrete two-way com­munications would be required in positive separation air­space.

Implementation of the Proposed ATC System: The REPORT recommends that the system outlined above be implemented gradually in evolutionary phases over the next five years as the required ground and airborne en­vironments become ovaiiable. !t is stated that for the most Part, the ground environment can be established through use of "off the shelf" items, without research and develop­ment efforts, i. e., the technology to accomplish the system goals is already in existence-all that is required is design specifications for the displays and computers. The REPORT estimates that implementation of the recommended system

16

will require capital expenditures of S 500 million (S 250 million above the current FAA Five-Year Plan), and the current FAA R & D budget of S 65 million per year will be adequate.

Major Project Beacon Recommendations: The following recommendations in the area of air traffic control are quoted verbatim from the REPORT. We have made a ~o­tation after each recommendation, indicating the Section of this report where related comments and recommen­dations are found.

l. Control should be based on aircraft position infor­mation continuously available on the ground and independent of the pilot's navigational information.

2. On certain high-use airways and in congested ter­minal areas, controlled and uncontrolled traffic should be segregated and speed limits instituted for VFR traffic.

3. All traffic above 24,000 feet MSL in and adjacent to high mountainous areas of the country and above 14 500 feet MSL in the rest of the country should be un,der positive area control. On certain high-use air­ways, the positive control requirement should be ex­tended down to 8,000 feet MSL.

4. To enable the non-instrument rated pilot to use these positive control areas under VFR conditions, a new category of flight should be established. This might be known as Controlled Visual Rules (CVR). Under these rules the pilot would enter the traffic control system and receive separation service but would maintain aircraft attitude by reference to the ground.

5. Below 8 000 feet MSL on the certain high-use airways referred' to above, a speed limit should be established for all traffic.

6. All aircraft above 12,500 lbs. gross weight should be required to carry altitude reporting beacon transpon­ders for use both enroute and in terminal areas.

7. The combined SAGE/FAA radar network should be employed for enroute control and a long with flight plans, provide the basic control information.

8. In the congested terminal areas, aircraft should be segregated in accordance with performance, and spe­cial arrival and departure ramps designated.

9. All aircraft landing at controlled airports within these designated terminal areas should be required to contact approach control at a specified distance from the airport.

l 0. Altitude information should be obtained through use of altitude reporting beacon transponders carried in the aircraft. Task Force studies indicate that a short range beacon satisfactory for termina I area use should be obtainable for no more than S 500. When such a beacon becomes available, it should be required in all aircraft landing at controlled airports within the designated congested terminal areas.

11. Special corridors and tunnels should be provided for unequipped VFR aircraft landing at uncontrolled air­ports or transiting the terminal area.

12. With complete position information available on the ground, pilot reports should be reduced drastically and controller and pilot load and frequency usage therefore held ta reasonable levels.

13. Genera! purpose computers should be employed in both the enroute and terminal area portions of the systems to process flight plans, issue clearances, make

conflict probes, generate display information, esta­blish landing sequences and perform other routine tasks of assistance to the control function.

14. Special express routes must be established in terminal areas to accommodate the greatly increased heli­copter traffic envisioned in the near future.

General Comments: In general, we agree with the broad concepts expressed in the REPORT, and with the major REPORT recommendations listed above. We cer­tainly agree with the elimination of the see-and-be-seen separation whenever and wherever possible consistent with the operational requirements of the users. We also agree with the philosophy of an organization and utilization of the airspace that would take advantage of any existing natural segregation by type and performance capability of aircraft. We can frnd no fault with the idea of IFR/VFR integration in terminal areas through positive separation. We frnd the idea of reserving some airspace at lower strata for VFR activity commendable. The extent to which the Task Force recommendations can be applied, however, will vary by location. Airspace availability, navigation aids, and user operation requirements are considerations which may affect the implementation of certain REPORT recommendations. In this regard, we are aware that the Beacon Task Force had time limitations which precluded the full investigation of all operational problems or imple­

mentation details.

SECTION IX:

Proposed Course of Action: In implementing the ATC system recommended by the REPORT, it is not possible at this stage to develop a defrnite schedule of actions for establishment of the recommended equipment environ­ment. In attempting to develop a plan to design, procure, and install the necessary equipment, there are many inter­related factors which must be considered. First ATS must develop the basic system requi1·ements within the REPORT's broad guidelines. The development of the hardware must, of necessity, be geared to availability of funds.

On the other hand the organization of the airspace along the !ines suggested in the REPORT is an area which lends itself to frrm scheduling and planning. The REPORT states that the recommended ATC system can become a reality in frve years, assuming that the necessary funds are forthcoming. We believe that the recommended air­space environment can be attained in this time period. We realize that the organization and utilization of the air­space is directly tied to equipment in a sense because the safe passage of a flight through airspace is predicated to a degree on the ATC control techniques and equipment. However, as we have pointed out in this report, the Agency "pre-Beacon" plans for the organization of the airspace are, fore the most part, compatible with the REPORT's

recommendations. Therefore, we have been able to go into some detail

on the plan to organize the airspace, although the plan­ning for the attainment of the equipment environment must remain quite broad at this stage of development. As men­tioned in this report, we should go ahead with our current plans for the expansion of area positive control, adapting these plans to the recommended airspace organization. Concurrently, we should be moving toward the establish­ment of the equipment environment. Accordingly, the fol­lowing plan of action is recommended.

Equipment

1. Pending a frnal decision on the use of SAGE facilities for ATC, review our current radar and beacon pro­grams to determine what must be done to attain the radar and beacon coverage recommended in the REPORT. The coverage should be attained through joint FAA/ADC use of existing ADC radars to the maximum extent possible. The initial objective is to provide coverage at and above 14,500 feet throughout the conterminous U.S. at the earliest possible date, and subsequently, coverage below 14,500 feet as re­quired.

2. Develop the basic system equipment requirements for the ATC system recommended by the REPORT as modi­fred by our recommendations. In accomplishing this task, close liaison will be maintained with the ARD System Design Team.

All of the above actions should be pursued concurrent­ly and completely before June 30, 1962. In setting dead­lines, we realize there may be slippage because of the complexity of the task. However, we believe that we must establish a deadline to strive for in order to organize the task. In this connection, as soon as a frrm determination is made on specifrc items of equipment, it should be im­mediately translated into a revision to "The FAA Plan for Air Navigation and Air Traffic Control Systems" in order to avoid lag time.

After completion of the above tasks, the following actions should be accompiished concurrently:

1. Establish an implemer.tation schedule for the equip­ment environment. This should be developed to cover the frveyear period FY 1963 - FY 1967, with the appro­priate Services participating in its development.

2. AT-40 and the ARD System Design Team jointly deve­lop a program to implement the REPORT's recommen­ded short-term improvements. Care must be taken to insure that these short-term improvements wi!! be com­patible with the ultimate system to the extent possible.

The above plan is quite broad, however, details will be added as we proceed with its development.

Airspace Organization and Utilization 1. Develop a detailed plan to establish an area posrt1ve

control system throughout the U.S. above 24,000 feet MSL. This plan is currently being developed as follows: a) Operation Topside - Establishment of a positive

control area in the continental control area, flight level 410 to flight level 600, inclusive.

b) Expansion of area positive control system in the continental control area above 24,000 feet. The frrst expansion is scheduled in the Detroit; Cleveland/ Pittsburgh, and possibly Oakland center areas. Sub­sequent expansion will be on a phased basis, sub­ject to equipment availability and allied with the center building program.

The target date for simultaneous implementation of Operation Topside and the Detroit, Cleveland/Pitts­burgh, Oakland package is March 1962. The establish­ment of a positive control area in the continental con. trol area from 24,000 to FL 600 should be accomplished before January 1964.

2. Develop a plan to establish a positive separntion system in high activity ter·minal areas rn consonance

17

with the concepts of the REPORT. We recommend the following sequence of actions:

a) Develop an operational concept. Deadline January 15, 1962.

b) Select a terminal area for establishment of a proto­type environment. Deadline January 15, 1962.

c) Complete simulation study. Deadline June 1, 1962.

d) Implement a Terminal Radar Control Service. Dead-1 i ne September l, 1962.

e) Phase into terminal positive separation based upon the results of the above evaluation.

3. Initiate action for a study to be conducted to obtain the required data outlined in Section II of this report.

4. It should be noted that the completion of the terminal evaluation will coincide with the completion of the expansion of positive control, 24,000 feet and above. Assuming that the terminal program and the traffic study provide the answers to the questions of CVR, accomplish the following:

Establish the airspace between 14,500 feet and 24,000 feet as positive separation area with CVR and IFR flight and with appropriate altitude adjust­ments in mountainous areas.

New International Aviation Organization formed

Formation of a new international organization to re­present general aviation owners and pilots was recently announced by J. B. Hartranft, Jr., president of the U.S. Aircraft Owners and Pilots Association and interim head of the formative worldwide group.

Known as the International Council of Aircraft Owner and Pilot Associations (ICAOPA), the new organization expects, among other things, to make it easier to fly from one country to another in private airplanes, thereby pro­moting greater international friendship, and to work with the United Nations-affiliated International Civil Aviation Organization in development of flight standards that will foster the growth of general aviation throughout the world.

The idea of an international confederation of general aviation, or non-airline, associations has been under dis­cussion between pilots from more than 50 nations during the past two years. As a result of interest expressed by many countries, the U.S. AOPA agreed to spearhead the formation of an autonomous international group, Hart­ranft said.

Senior vice president of ICAOPA is Douglas Wagner, president of the Canadian Owners and Pilots Association. Leslie H. Ford, president of the Aircraft Owners and Pilots Association of Australia is interim vice president for the Pacific Region of the organization and Charles S. Logsdon has been named temporary secretary. Logsdon is well known in international aviation circles through previous work with authorities responsible for rules and regulations governing the estabiishrnent of international air records and the conduct of sporting aviation competitions.

It is anticipated that ICAOPA will represent at least 15 national flying groups with a joint membership of more than 250,000 in the nem future, Hartranft revealed. Asso­ciations that have already signed the organizational char­ter are the Australian and U.S. Aircraft Owners and Pilots Associations, and the Canadian Owners and Pilots Asso­ciation. Signatures by the South African Aircraft Owners and Pilots Association and the Philippine Airmen's Organi­zation appear to be imminent, he added.

One of the basic aims of the new organization, Hart­ranft said, wil! be to provide general aviation with a stronger voice in the formulation of international flight standards.

18

."Commercial pa.ssenger and air transport interests now wield the bulk of influence international! " h 'd "G -. . y ' e SOI • e neral 0~1at1on, on the other hand, has heretofore had little to say 1n matters of policy formulation, even though it accounts for the greatest percentage of · t ffi th h air ra 1c roug -out the world. We hope to have the JCAOPA I . . serve genera av1at1on much as the International A'1r T t A · . ranspor ssoc1a-t1on (IATA) serves the airlines and the I t t' I F d . . . n erna 1ona e e-ration ?f Airline Pilots (IFALPA) serves the airline pilots." . Unl1~e some ?r~anizations that presently participate in international av1at1on activities ICAOPA ·11 t · I d . ' w1 no 1nc u e non-flying groups, Hartranft said Each t' b . · no ion may e represented in ICAOPA by only one 0 · t' . . ssoc1a ion or re-cognized group of aircraft owners or pilots, he added.

Headquarters for the new organization · I d . 1s ocate at 4650 East-West Highway, Washington 14 D c M b

· b ' · · ern ers of the executive oard will hold regular meef S . I . ings every

two years. pec10 meetings will be scheduled to d 1 . . bi H . ea with

specific pro ems, artranft said, but routine matters . be handled by correspondence. Wi II

Purposes of the international body are red·- d : · · · · U<.e rn its

const1tut1on to a s1x-po1nt program These · · points are:

1. To facilitate the movement of aircraft · t . f f I . in ernatronally or peace u purposes, in order to d I f . .

d d ~ d' eve op r1endsh1p Tan un d~rs.an ing .among peoples of the world.

2. o coor inate the views and opinio f · · ns o member orga-

nizations as expressed by memb f h . b d · h ers o t e executive

oard ,dw1t r~spect to proposed requirements recom-men e practices, procedure< rule ! ·1· . ' · f · . · -, ' s, 1 0Ci1ihes and ser-vices or 1nternatronal aviation. ·

3. To represent the views and inter t f h · . es s o t e board on

general av1atron matters as app · f h I . ' ropriote, at meetings

o t e nternatronal Civil Aviation 0 . . . rganrzat:on

4. To develop and promote desirabl d · d d . · f e an usable stan-

ar 1zation or the regulation 0 d 'd 1 aviation. n gui once of genera

5. To encourage the implementatio f 1 ! .,. . . n o p anned systems, 1ac111l1es, services and procedure . d fl · h s in or er to promote

1g t safety and efficiency for ge I . . nera av1atron.

6. To collect from and disseminate . . . . among member orga-

n1zat1ons 1nformatron data and st t' t' 1 . t . . . ' a 1s 1cs re at1ng o general av1atron, including inter al' th .. . 10 ose perta1n1ng to the progress of air navigation corn . t' f . . . , mun1ca ions, ac1-l1tres and the operation of general · t' · ft av1a ion 01rcra .

Must the VHF Omni-Range make Way for a Hyperbolic System?

For several years this question has occupied the atten­tion of those who reflect on problems of air navigation and air traffic control now and in the future. The rivalry between polar (rho-theta) and hyperbolic systems waxed keener than ever when ICAO had to recommend a world standard for short-distance aids which committed the future for a good many years. Finally, it was VOR/DME which won recommendation, and its replacement as a standard aid will not normally be contemplated before 1 January 19751). Considerable sums have now been expended, both in Europe and in the United States, on financing VOR/DME or VORTAC installations. All the more significant, in this light, is the following passage from the "Project Beacon" report published by the Federal Aviation Agency (Report of the Task Force on Air Traffic Control, p. 8) 2):

"Our present nationwide system of very high frequency omni-ranges, with the addition of DME, will be adequate for many years over most of the country. However, special navigation facilities will be required in the very near future to permit efficient helicopter operations in some terminal areas.

"In addition, over a few very high density routes a more precise navigational means will be required to permit closer paralleling of airways."

We submit those two remarks to our readers' reflexion.

Before going on to analyse, briefly, the reasons de­tailed in support of those recommendations, we may recall that the "Project Beacon" report was established in answer to a request from President Kennedy for a review of air navigation and air traffic control facilities leading to pre­paration of a long-range plan "to insure the efficient and safe control of the Nation's air traffic".

In the chapter on "Navigation" the authors of the Re­port have the following to say about VOR accuracy:

"When installed on a level site free from reflecting ob­iects, the VOR-airplane combination provides bearings accurate to about ±2°. When there are reflecting objects, such as power lines, metal stacks and towers, and major terrain features, what is known as scalloping appears in courses. As the plane flies along a radial, the course appears to swing back and forth by as much as ±2° in addition to the normal instrumental and installation er­rors ...

"An improved version known as the Doppler VOR which reduces scalloping to a marked degree has been deve­loped and is being installed as a replacement at trouble­some sites ... "

"The distance (rho)-bearing (theta) system provides a satisfactory navigation system as long as the traffic does not get too heavy. Our basic method of separation of traffic, VFR and IFR, and traffic in opposite directions has been by altitude as measured by the aneroid altimeters aboard the aircraft. This has been done because our mea­surement of altitude is more accurate and much smaller separations can be specified safely than could be hori­zontally by the VORTAC system.

"At a distance of 100 nautical miles an error of ±4° in bearing amounts to ±7"' nautical miles. !n other words, the width of a given radial course may be as much as 14 miles

'~0 Council decision of 8 April 1960 in favour of amendment 35

to Annex 10. ') An anolysis of this report will appear in the ITA Bulletin.

at !~at ~istance. Of course, it drops directly as the VORT AC st~t1~n 1s a~proached. Even if the scalloping effects are el1m1nated, 1t appears that reducing errors dependabl below ±2° with either VOR or TACAN would be very diffi­cult."

"Th~s, small lateral separations permitting closely spa­ced air"."ays are hard to achieve with rho-theta systems."

Having thus shown the limitations of the VORTAC system, the report goes on to say:

" ... with the inauguration of IFR helicopter operations comes the need for more accurate navigation facilities to mok~ these operations commercially feasible in congested ter~inal ~reas .. By 1965-1970 there will be as many as 60 heliports, including fixed-wing airports, in the greater New York area, and the number of helicopters operating at low altitudes will be such that perhaps 50 of them may be airborne at a given moment. As an example, the heavily traveled segments between Newark, La Guardia, ldlewild, and the Manhattan heliports may have several bound each way at a given time. Since the operations will be conducted at low altitudes with little opportunity for alti­tude separation, it will be necessary to provide accurate means of maintaining horizontal separation between heli­copters and between them and the obstructions in the New York area.

"Flying with a very low frequency hyperbolic navigation system has been done for evaluation purposes by New York Airways and by FAA's experimental all-weather heli­copter line between Bridgeport and Atlantic City. This system has given reliable service with adequate accuracy although it does have some presentation problems."

The authors report briefly, next, on studies with a system based on multiple DME measurements giving near­ly simultaneous distance measurements to two VORTAC stations. The conclusions of the studies are that positional accuracies of ±1 nm are easily obtained, ±0.5 nm is possi­ble, and that in certain critical areas with properly located facilities, ±0.2 nm is possible in the critical direction.

Progress in oscillator frequency stability seems likely to make distance measurement possible by one-way trans­mission of radio signals (the airborne time standard being extremely accurate) rather than by two-way transmission as at present.

This type of system, the report concludes, has the same type of presentation problem as hyperbolic systems.

The conclusions reached as regards helicopters, it notes, are equally applicable to V/STOL or to the whole class of "steep gradient" aircraft.

If we compare the conclusions pointed to by the Task Force and those reached by the Systems Engineering Team formed to study the question of "Modernizing the National System of Aviation Facilities" and assist Mr. Curtis in the task then entrusted him by President Eisenhower, we can­not fail to remark that to a fair extent they coincide. We shall not return here in detail to the Systems Engineering Team's report, which has already been discussed in an ITA Research Paper3), but for present purposes it will suffice to recall the essential conclusion, that at all points of the airway network where great accuracy and flexibility are required of navigation aids, VORTAC will prove inade­quate and should, for that reason, be replaced as emly as possible by a hyperbolic system•). As emly as 1957, that means, US experts believed that VORTAC would have

19

shortcomings both in accuracy and in flexibility for certain situations in future air navigation and air traffic control -in particular in congested terminal areas and high-density en-route areas.

If we recall, too, that as far back as 1956-1957 the !CAO Jet Operational Requirements Panel recommended adop­tion of a short/medium-range navigation aid based on area coverage and providing the pilot with a pictorial display of his track, we cannot fail to note the persistence of expert opinion in a great many circles in favour of

') No. 318, January 1959: "VORTAC or a Hyperbolic System?" ') Hyperbolic systems already tried out, in addition to Decca which

has been operational far same considerable time, include "Radia­Mesh" (Radio-Maille) in France and Cytec in the United States.

Doppler VOR in Service in the United States In the second half of last year, the first Doppler-type

VOR was put in service in the USA at Marquette (Michi­gan), followed by a second at Rikers Island near New York.

Now approved by the Federal Aviation Agency, this navigation aid will be installed wherever the cost of re­moving buildings, gasometers, metal bridges, etc., for a standard VOR site is prohibitive. (Ordinary VOR is sensi­tive to parasite echoes and frequently calls for consider­able site preparation : removal of trees, displacement of power lines, etc.)

Doppler VOR can be used with standard airborne equipment, so that no duplication is necessary.

In its ordinary form, the VHF Omnidirectional Radio­range transmits two signals: a reference signal which is frequency-modulated and fixed in phase, and an ampli­tude-moduated signal the phase of which varies with azi-

*

future replacement of "point" navigation systems by a more accurate system ensuring area coverage. In the inter­val, the VHF omni-range will nonetheless have rendered signal service, but it is interesting to observe that it is in that country which developed its use most widely that it is likely to be first replaced, in certain parts of the airway system and progressively, by a navigation system based on measurement of distance rather than angles. The que­stion then arises, whether VOR/DME can carry on for long as a duplicate, or whether the new system eventually chosen from among the alternatives offering will not be selected precisely because it can cover, with a single type of airborne receiver in use, the requirements of naviga­tion and air traffic control en route and in terminal areas.

(ITA)

muth. Comparison of the phases of the two provides 0

measurement of bearing.

With Doppler VOR, the two types of signal change roles. As the frequency-modulated signals are less sensi­tive to echoes reflected from nearby obstacles, Doppler VOR can be used on sites unsuitable for the standard equipment.

Doppler VOR stations are housed in buildings measur­ing about 35X35 ft. Instead of a central antenna, abo t fifty antenna units are laid out in a circle of some 45 ft ~ diameter around the building. Mechanical means are u 1dn . . se to feed the antennas in su_c~ess'.on so ?s to set up a rotat-ing field. More counterpoising 1s required than with stan­dard VOR. (IT A)

(Reprinted from ITA-Bull~tin, February 1962, with kind permission the lnstitut du Transport Almen.) of

International Aviation takes great Interest in Hannover Air Show 1962

The Hannover Air Show, jointly prepared and organised by the Bundesverband der Deutschen Luft- und Raumfahrt­industrie and the Deutsche Messe- und Ausstellungs-AG will take place from 29th April through 8th May at Han­nover airport, Germany. The applications which have been submitted so far by domestic and foreign firms reflect the significance attributed to the fair by national and inter­national exhibitors.

The display area will be twice as large as in 1960. A new exhibition hall has been constructed, and the total display surface is now 8900 squ.mtrs.

Nearly all of the German aviation and space industry wi II be represented as we! I as space and aviation research. In addition, a large number of European and overseas nations will participate in the exhibition through their major aviation and electronics manufacturers. Particular interest in the fair has been shown by France, Great Bri­tain, and the United States.

In both exhibition halls aircraft components and en­gines will be displayed, as well as aircraft hydraulics and

20

the most recent developments of the avionics indu t . Communication and navigation equipment, radar s ryd.

k · · t" I t I ' an coc pit instrumenta ion. ns rument anding system . I. h · d · t ff" I s, a 1 r-port 1g ting an mr ra 1c contra equipment will al b

on display. Other items are rescue equipment se ~o e . , mi-pro-ducts and material of subcontractors especially d ' mo ern plastic products.

Spacecraft propelling systems as well as comm · . . . . un1cat1on and nav1gat1on equipment for lunar and space h" 1

f h . d" 1 d ve 1c es are part o t e items 1sp aye in the space t h 1 sector.

ec no ogy

The open air display area is mainly for gro d d . f un ser-

vices equipment an a1rc_ra t. About 100 aircraft will be demonstrated, almost twice as much as d · h . . . uring t e ex-h1b1hon two years ago. Among others the fi t G . . 1rs erman-bu ilt Fiat G-91 and Lo~kheed F l 04 G "Starfighter" wi 11 be presented to the public.

A special flight operations office will prov"d th . . 1 e smoo traffic handling for the extensive number of h"b"f aircraft. ex 1 1 ion

ATC News from the U. K.

The Guild of Air Traffic Control Officers has elected John Macdonald to be its Master for the Ninth Court of the Guild. Macdonald, currently serving at Ministry of Aviation Headquarters in London was a Royal Air Force pilot during World War II from 1939, having flown with Fighter and Flying Training Commands. Joining the then MTCA in 1946, he has been an ATCO at SATCC when at Uxbridge, London Airport Southern Division, Ministry of Aviation prior to his present appointment and holds a Commercial Pilots Licence and current Instrument Rating. A Founder Member of the Guild, Macdonald has served on successive Courts of the Guild since 1954 and was Guild Treasurer during the preformation years 1952-4 until 1958.

The retiring Master, Arnold Field ARAeS, duly invested the new Master with the Regalia of Office at the Annual General Meeting of the Guild on April 7th.

The Wardens for the Ninth Court are: N. Alcock, ACIS AMlnstT, J. N. Toseland, G. C. Burch, MBE., N. Vernon,

I. M. Lucas.

L. S. Vass was pre-appointed Clerk of the Guild and is also Chaiman of the Guild's Convention Committee.

G. C. Burch, MBE continues as Guild Treasurer and N. Alcock as Editor of the Journal of the Guild of Air Traffic

Control Officers.

E. Bradshaw was appointed Assistant Clerk of the Guild.

Consequent upon the Guild's decision to join the In­ternational Federation of Air Traffic Controlers' Asso­ciations, the Court of the Guild has appointed Arnold Field ARAeS and L. S. Vass to be its Delegates in the first in­stance and these two members will attend the forthcoming

IFATCA Conference in Paris this month.

Masters of the Lodges of the Guild for 1962/3 have

been elected thus:

Midlands Lodge T. R. Newton

Northwestern Lodge A. Round, AFC

London Lodge P. D.S. Mealing

Wessex Lodge N. Ward LLB

Scottish Lodge W. E. Thompson

Aircrews ond all those interested in discussing mutual problems of Air Traffic Control are cordially invited to do so through the medium of Lodge Meetings within their areas of interest or residence. The Clerk of the Guild will forward all such requests to the appropriate Lodges for

action.

The Hunt Trophy: Following due consideration of all applications received, the Wardens decided the Guild

would not make an Award for 1961.

The Trophy is awarded in respect of the most outstand­ing cont1·ibution to Air Traffic Control during the preced­

ing year.

LORENZ seit mehr als 25 Jahren bahnbrechend in der Flugnavigation durch Funk

VOR I LS

FBI! ZFB

VD F 1

U D F 1 TA CAN

CONSOL

VH F-Drehfunkfeuer nach FAA Richtlinien Landefunkfeuer dem Dusenflugverkehr angepal3t Facherfunkfeuer und Z-Marker Mittelwellenfunkfeuer fUr Zielanfluge GroBbasis-Doppler-Peiler im VH F-Bereich GroBbasis-Doppler-Peiler im UH F-Bereich Rho -Theta-System fur Mittelstrecken Funkfeuer fUr Langstrecken

~SEL Standard Elektrik Lorenz AG Stuttgart

21

The Potez- Hein ke l CM 191 wi ll be on display at the Hannover Air Show.

Maiden Flight of the Potez-Heinkel CM 191 On March 19, 1962, the CM 191, developed jointly by

Ernst Heinkel Flugzeugbau GmbH and the French aircraft manufacturer Potez took off for her first flight. The Potez­Heinkel CM 191 is a four passenger executive and liaison aircraft, equipped with two jet engines . The first fl ight was carried out by Potez chiefpilot Jaques Grangette and

I FATCA Member Associations

In reply to many enquiries of our readers we are pu­blishing the addresses of IFATCA Member Associations, and the names of their presidents .

They offer their advice and cooperation in all matters regarding air traffic control. Interested parties are cordial­ly invited to establish relations with their national asso­ciations .

Austria

Verban d Osterreichischer Flugverkehrskontrollore, Wi en Schwechat Airport, Flugsicherung, Ottokar Schubert, I FAT CA Director

Belgium

Guilde Be ige du Contr61eurs du Traflc Aeri e n Samenwerkersplein 7, Sint-Agatha-Berchem, B'russels, Roger J . Sadet, IFATCA Director

Denmark

Dan sk Fl yve leder Forening, Copenhagen-Kastrup Airport, A ir Traffic Control, A . G . T. Niel sen, IFATCA Di rector

Finland

Suomen Lenonjoh ta jin Yhdistys r. y., Hel sinki Airport, Air Traffic Control , Fredrik Lehto, I FAT CA Director

France

Association Professio ne lle de la Circulation Aerienne, B. P. 21, Aeroport du Bourget, J. Flem ent, IFATCA Director

22

lasted more than half an hour. Grangette who took off from Toulouse-Blagnac airport under unfavourable wea­ther conditions - strong, gusty winds - commented enthu­siastically on the flying characteristics of the aircraft.

The CM 191 will be demonstrated at the Hannover Air

Show.

Germany

Verband Deutscher Flugleiter e.V., Cologne-Wahn Airport, Hans W. Thau, IFATCA Director

Iceland

Felag lslenzkra Flugunferdastj6ra, Reykjavik Airport, Air Traffic Control, Valdimar Olafsson, IFATCA Director

Ireland

Irish Air Traffic Control Officer's Association, Shannon Airport, Air Traffic Control, J . E. Murphy, IFATCA Director

Luxembourg

Guilde Luxembourgoise des Controleurs de la Circulation Aeroport du Luxembourg, Air Traffic Control, [Aerienne , A. F. Feltes, IFATCA Director

Netherlands

Het Nederlandse Luchtverkeersleidersg ilde, Nieuwe Prinsengracht 9, Amsterdam-C J . van Ginkel, IFATCA Director '

Norway

Lufttrafikkledelsens Forening, Stavanger-Sola Airport, Lufttrafikktjenesten, 0 . Saboe, IFATCA Director

Switzerland

Verband des Personals der Radio Schweiz AG Zurich-Kloten Airport, Flugsicherungskontrol ldtenst, Bernhard Ru thy, I FAT CA Director

Survey:

Modern Equipment, Installations and Systems for Air Traffic Control and Air Navigation The following descriptions have been extracted from manufacturer's system specifications. The publication of such data is for educationol purposes and should not be construed to the effect that IFATCA

prefers this to other equipment not described herein.

Contents

I RADAR I Radar Equipment and Systems

Decca Transistor Display Mark V

WF2 Radar for High Altitude Wind Measurements

Navigation

Self-conta ined Doppler Navigation

Systems

Decca Transistor Display System Mark V

The Decca TDS Mark V is a fully transistorised display and data handling system. It is based on a new concept in transistor engineering known as environment stabilisa­tion. This technique, in which an integral liquid cooling

Envi ronment Stabili sation , 0 new concept in tran si stor eng ineering ,

is employed i n th e TDS Mork V equ ipment.

PI L

MET

Pilotage

VIPS Warning System

Meteorology

C-Band Meteorological Radar Set AN-FPS 68

system maintains all circu its at constant temperature, over­comes the temperature sensitivity of transistors and per­mits their use in high performance equ ipment. A com­pletely new order of reliablity is also achieved because no components are subject to heat cycl ing.

Both equipment size and power consumption are redu­ced by a factor of about 10 compared to equivalent tube equipment. A small trailer, for example, suitable for trans­

port by air, can house th e TDS Mark V drive circuits for a complex military data handling system w hich might require a bu i lding of the size of a small cinema if conventional engin eer ing were employed .

Decca says that the improvement in reliability is such that the availability of a large display and data handling system using TDS Mark V techniques can be confidently expected to exceed 99,50/o over running periods in excess of 10,000 hours.

The TDS Mark V display system comprises centralised display drive equipment and associated viewing units . The drive equipment is engineered on a modular basis and consists of a number of electronic cabinets operating in conjunction with a power and coo lant cabinet which con­tains power supp li es a nd the liquid cooling system, with associated heat exchanger, employed for env ironm ent sta­bilisation . The viewing un its , which li ke the drive equip­ment are f ull y transistori sed, are norma lly installed re­

motely from the drive equipment. Th e basis of radar data handling and presenta t ion is

simila r to the method emp loyed in the estab l ished Decca lntersca n Display Series of tube sys tems. Essenti a ll y th is method consists in genera t ing su itab le waveform s to con ­trol th e timeboses o f fi xed co i l ty pe v iewing units in such

23

I RADAR I

a way that a composite picture showing all required raw radar information, synthetic data and operator aids is built up and presented on the cathode ray tube. A high speed electronic switching system is employed to drive the waveform generators and the time shoring is arranged to give flicker-free presentation of all required synthetic

do to. The TDS Mork V, in which the fully transistorised cen­

tral complex is extremely compact even in sophisticated systems, greatly extends the role of the Decca lnterscon Display series and is suitable for o wider range of systems.

The basic principle of the TDS Mork V Display System is environment stabilisation. All transistors and compo­nents are contained in cabinets which are maintained at a stable temperature, controlled to within ± 0.25° C of the operating level. In this way the transistor characteristics, which vary widely with temperatures, are stabilised. Heat cycling of all components is also avoided.

The Electronic Cabinets

The cabinets are constructed from an aluminium frame which is moulded into a fibre glass outer case . The frame provides the structural strength, while the fibre glass pro­vides good thermal insulation . Within the electronic cabi­net are mounted three open cold plates, which house the printed circuit boards. The cold plate is of a special form since it contains the ducts carrying the cooling liquid and has a heated blanket as a surround. Flow of coolant to the ducts or power to the blanket is individually controlled by a temperature sensing system in each cold plate, with the result that the surfaces of the cold plates are main­tained to a very stable temperature. The printed circuit boards are mounted in a metal surround, which carries the transistors in metal clips. When the printed circuit boards ore located in the cold plate the surround is in good thermal contact with the cold plate and the transi ­stors ore thereby maintained at o stable temperature .

Hinged transparent perspex panels ore used as inner doors to the cold plates and sliding panels unmask slots in these panels to allow for access to monitor points when setting up. The equipment operates cont inously with the main door open and the slots in the inner door open ; it may be run for 30 minutes with the inner doors open.

The Power and Cooling Cabinets

The power and coolant cabinet contains in the upper part a rect ifier and bulk stabiliser for providing HT power supplies to the printed circuit boa rds in three electronic cabinets . Further close control of HT stability is provided by local stabi lisers fitted into individual cold plates and controlling supplies to t he circuit boards they contain .

In the lower part of the cabinet is a heat exchanger and refrigerator system . Duplicate industr ial refrigerator units supply coolant to the heat exchanger tank, each refrigerator working for part of the required duty cycle . A secondary circuit from the heat exchanger tank provides coolant to the cold plates through a pumping system con­troiled by the temperature control units. Stable tempera­ture is mainta ined throughout a cabinet group in ambient temperatures up to 45° C. Extracted heat can be exhausted to the oir or removed by add itional liquid cooling equ ip ­ment.

The purpose of these specially designed cabinets is to provide a fully stabi li sed environment. The transistor cir-

24

TD S Mork V Viewing Unit.

·t te ·1n an environment which is always tempera-cu1 s opera .

t tant and dust and moisture-proof. ure-cons ,

Viewing Units

The 12 and 21 inch diameter units ore fully transisto­rised with the exception of cathode ray tube and EHT rec-

t .fi These units, which ore suitable for console or table 11er. h . . h" h

top installation, contain only t ose c1rcu1ts w 1c must necessarily be located close to the ca'.hode r~y t_ube and those which are indiv idual to o particular v1ew1ng unit. Performance requirements do not normally coll for full environment stabilisation of the transistors in these units . Instead 0 heat exchange method is employed whereby cooling liquid is circulated through cold plates containing the printed circuit boards in the same way as in the elec­tronic cabinets of the central display drive equipment. A coolant connection is also prov ided to o heat sink asso­ciated to the power transistors employed in the deflector coil drive unit. A small fan and radiator exhaust surplus heat from the rear of the unit but no elaborate air con­ditioning of the comportment or expensive exhaust direct­ing is necessary. In special cases where a number of view­ing units are operating in o confined space or where very high ambient temperatures ore expected, surplus heat can be removed through a separate liquid cooling system.

The viewing units contain their own power supplies and ore self-contained in respect of external services, apart from the waveforms necessary to control deflections and brightness on the cathode ray tubes .

Operational Facilities

1. PPI presentation of radar information from single or multi-beam antennas.

2. Presentation of special types of displays for height­finding and analysis purposes .

3. Presentation of markers and symbols together with selective interconsole marking between displays .

4. Presentati on of target future position .

5. Provision of manual, rate aide or automatic tracking facilities.

L

6. Generation and presentation of interception computa­tions and air traffic control conflict indications.

7. Presentation of alpha-numeric information either on synthetic displays or on labelled raw radar displays.

8. The system is designed for use with any radar equip­ment or equipments, or in association with digital com­puters in sophisticated data handling systems with mul­tiple inputs.

WF 2 Radar for High Altitude Wind Measurements

Efficient and economical operation of high flying jet aircraft requires accurate knowledge of wind velocity in the upper airspace. Generally, and when applying con­ventional measuring devices (Theodolite-Radar combi­nation), regular information on the upper wind condition could only be obtained up to 20 km. However, experience indicates the considerable value of information on the conditions at higher altitudes, up to 30 km. Prerequirement for reliable tracking of the met-balloon is long range radar equipment, because of the great distances such a balloon may travel under the influence of strong winds in the upper airspace.

Studies of the upper wind phenomena, up to now, indi­cate that the strongest jetstreams occur during winter and may reach speeds of 150 knots and more, at an altitude of approximately 25000 to 30000 feet. Considering the high wind velocity, the climbing speed of the meteoro­logical balloon, (1000 to 2000 ft/min.}, and the required altitude of 80000 to l DODOO feet, the slant range me be as much as 130 n. m., in the final stage of the ascent.

These requirements for high altitude balloon tracing can be met by the WF 2 radar if the balloon is equipped with a suitable corner reflector the equivalent echo sur­face of which should be about 2000 m2

, according to

Decca Radar Limited .

A radar of this type will shortly be installed by Tele­funken GmbH in Emden, Northern Germany, for the Ger­man Meteorological Services. The predecessor of this type of radar, the WF l, has been in use in Germany since some time already, It has shorter range than the WF 2.

W F2 Meteoro log ica l Rad a r.

Range Scales Four pre-set ranges, maximum ratio l 0 : 1. Maximum range is equivalent to minimum PRF interval less 60 µ sees. Minimum range is 5 nautical miles per radius. Expansion of picture with selection of range scale maintains registration of mainscans and interscans . Range expansion can be about CRT centre or radar origin

(Decca Radar Limited)

Inside vi ew of th e opera lor ' s hut.

The WF 2 is, like the WF l , a fixed installation . The equip­ment consists of the antenna which is mounted on a rotary deck with the operators hut which contains the electronic equipment, i.e. the scope and the elevation and azimuth indicators . The antenna is of the parabolic reflector type, using a decentrally located rotating feed horn . Th e beam­width is 1° . Conical target sc reening is achieved as the feed horn rotates at 50 revol ./min .

For easier target detection during ascent an auxiliary reflector may be used which increases the rotation dia ­meter from 2° to 10° . The reflected echo is di splayed on a cathode ray tube using J-scanning . It appears as a ring on the scope which, because of the conical target screen­ing , is only the n a c losed circle, whe n th e a nte nna ax is is directed exactly towards the target . Vertical and hori­zontal angle are then indicated with an accuracy better than 0,1 ° . The radial di stance of the ci rcl e on th e scope is equivalent to the slant range and can be read off at video range marks.

The indicators are design ed for one-man -operat ion and can be "frozen" during rnad-off, in order· to lea ve the ope rato r suffi c ient time for noting down the in d ica ted data. When they are released again a ser·vo sys tem re­es tablish es the correct setting . It is also poss ibl e _to read off data automaticall y and feed it in to a n e lectric type ­w riter. As an add itional fe a ture a compute r can be added whi ch computes the mea sured data into rea l va lues an d pr ints th e m. It ma y located a s far as 250 mt rs. fr om the radar. Thus it is possi b le to receive the data ri gh t in the Met office .

(Decca Rada r Li m ited Telefun ken G mbH)

25

jRADARj

ffiIJ Self-contained Doppler Navigation Systems

The principle established in 1842 by Christian Doppler, an Austrian physicist, states that when the distance is changing between a monitor and a source of constant vibrations (such as sound or microwaves), the monitored wave frequently will appear to be more or less than the true frequency, depending upon whether the distance is being diminished or lengthened.

For many years, self-contained navigation systems uti­lizing this principle have been considered. However, practical application of the Doppler principle to aircraft navigation became possible only in the last decade, when the electronic components necessary for such a system were developed.

A precise aircraft navigation system which is inde­pendent of terrestial aids is of inestimable value. In all air activities, there is an acute requirement for exact all­weather navigation and position-determination, especially with the advent of high-speed jet craft and the increasing congestion of air traffic.

For precise aircraft navigation (and air traffic control), the pilot must know: (1) his present ground track and its relation to his desired course-to-destination, (2) his true ground speed (for computation of estimated time-of­arrival, fuel reserve, etc.), and (3) his present position in whatever coordinate system he is using. This data, in addition to its usefulness for pilotage and navigation, is required for transmission by the pilot to air traffic control. in helicopter navigation, exact vertical velocity also must be known.

/ /

/ Figure 1. Typical "T" Beom Orientotion.

----

FORE -------

In accordance with the Doppler principle, all Doppler Navigation Systems transmit microwave beams to the ground which return to the transmitter-receiver altered in frequency. By measuring the frequency shifts of two or more beams having different azimuthal angles, two or more velocity components may be determined. Several systems produced by American and Canadian manu­facturers utilize four microwave beams. However, three beams ore sufficient to determine velocity uniquely in both magnitude and direction with respect to the aircraft. The three beams of LFE systems ore oriented in "T", "}.", or "reserve;." patterns; to simplify discussion, all references to beam orientation in this article will deal with a typical "T" beam pattern, shown in figure 1. The portion of a Doppler navigation system that produces outputs pro-

26

ANTEN"llA RECEIVER

Figure 2. Doppler Sensor Block Diogram.

FREQUENCY ft'EASU~EMENT

·JELOCITY

OUTPUTS

portional to the aircraft velocity is commonly called the Doppler sensor; it is comprised of a microwave trans­mitter, antenna, receiver and frequency measuring devices. These are shown diagrammatically in figure 2.

In LFE Doppler systems, forward, side and rear beams are transmitted from a single dielectric lens or a planar array antenna, and return to the source. These very nar­row beams are oriented so that, for all normal maneuvers of an aircraft, a small portion of the energy will be re­flected back to the aircraft's antenna, changed in fre­quency in accordance with the aircraft's motion. To be specific, the frequency of the forward beam increases with forward motion while that of the rear beam decreases; in the case of a helicopter's rearward motion, the con­verse is true. The side beam provides lateral velocity data to satisfy the orienting required by the computers. Verti­cal velocity data is obtained from the difference resu1 1ing from the cancellation of one longitudinal beam by the other.

The Doppler sensor processes these three signals and puts out digital outputs representing the three orthogonal components of the aircraft's velocity. The forward and lateral components alone, through simple computations, provide ground-speed and drift-angle; the vertical com­ponent provides vertical velocity. Manual dead-reckoning is furnished by combining these two quantities with a heading reference. Certain of these computations require digital-to-analog or analog-to-digital conversion of data.

Positional information with respect to a pre-determined course also can be obtained through a simple computer by combinig the velocity and heading data. The outputs of this ~ositional computer consist of distance-to-go along the desired course, cross-course deviation, ground-track, ground-speed, and time-to-go. During flight, a system thus may visually display the pilot's present position with re­spect to destination by showing in nautical miles the re­maining distance-to-destination as well as the distance right or left of the desired course. With additional ele­ments in a computer, it is possible to determine present position in other coordinate systems, such as latitude and longitude, and to compute courses with respect to arbi-

trary destinations. Wind speed, automatic magnetic­variation correction and other functions also become possible with additional computer elements. The perfor­mance parameters of LFE systems are given in the Para­meter Table. With the multiple outputs outlined above, automatic navigation and flight control become possible since the system outputs may be directly connected to any automatic pilot, or, in the case of helicopters, with an automatic hovering device.

LFE Doppler Navigation Systems Parameters

Operational limits Groundspeed Drift angle Vertical velocity Altitude Geographical range Pitch Roll Yaw

Performance Present position

Computer course-to­destination Computed distance-to­destination

Computed track Groundspeed components System time constant

Physical characteristics Size Weight Power Consumption

Frequency

Functions Available

-150 to 1500 knots ±90° max. ±3000 to ±50,000 feet/min 0-80,000 feet unlimited ±30° per sec. max. ±100° per. sec. max. ±45° per. sec. max.

±0.6 per cent of distance travelled or ±0.2 nautical mile, whichever is greater ±0.3°

0.5 per cent of distance to go, or 0.4 miles, whichever is greater ±0.3°

±0.2 per cent l second

2.10 to 7.1 cu. ft. 55 to 244 pounds. 7 A, 115 V, 400 cps, 3 phase, BA, 28 V DC X-Band (9800 me) and K-Band (13500 me)

Present Position (latitude and longitude) Groundspeed Drift angle Track Course-to-destination Di stance-to-destination Deviation between course and track Alternate destination selection Wind vector components Wind memory Present position fixing enroute Vertical velocity Automatic variation Velocity compensation for north-seeking gyrocompass

In addition to the above-mentioned characteristics, the navigational system may continuously display a course-to­destination. Usually, there are provisions for storing two or more destinations in the computer to allow the pilot to choose alternate courses in mid-flight. Courses-to-destina­tion generated by the computer are the shortest great circle routes.

RF.MOTE ATTITOOE DIRECTOR INDICATOR

CONTROL INDICATOR

VERTICAL POINTER tSteM'lng Error)

MAGNETIC COURSE TO DESTINATION

MAGf£TlC HEADl«i COMMAND HEADl<G

MAGNETIC GR04..Nl TRACK

HORIZONTAL SITUATION INDICATOR

GROUND SPEED-DRIFT ANGLE INDICATOR

Figure 3. Control Box and Display Indicators for one type of LFE Dopp­ler Navigation System.

Figure 3 shows the control box and display units of one of the LFE Doppler Navigation Systems. In operation, the counters are slewed to set in both present position and destinations, with the "Operate" switch in "Fix" position and the "Heading Mode" switch set in accordance with the desired display coordinates. When airborne fix data are available, present position may be slewed-in during flight.

All LFE systems have sufficient memory capacity to permit fix-taking without losing the accumulated change­in-position information during the elapsed fix-taking time. System outputs are displayed on "Ground Speed", "Hori­zontal Situation" and "Remote Attitude Director" indi­cators. The Ground Speed Indicator gives the speed in knots and also displays the angle of drift from the pre­scribed course. The Horizontal Situation Indicator (HSI) displays the magnetic course-to-destination, magnetic heading, command heading, magnetic ground track and distance-to-destination. The vertical pointer of the Remote Attitude Director indicates command heading while the vertical pointer alarm flag indicates "Doppler Off".

While the velocity components furnished by this type of Doppler system are more accurate than the heading information provided by the best magnetic heading refe­rence, the limit of positional accuracy is established by the heading reference. However, velocity output signals may be used to compensate an inertial heading-reference such as a gyrocompass or earth rate directional reference system; in this manner, greater overall accuracy is ob­tained. Errors in Doppler navigation generally are given in terms of a percentage of the total distance travelled,

27

PI L

Figu re 4_ Radar Set AN/ APN-11 6.

inasmuch as such errors are essentially independent of the time in flight ; this is not true of inertial systems.

Doppler Navigation Systems offer many advantages for fi xed and rotary-w ing aircraft, both military and com­mercial. They provide the most accurate all-weather, auto­matic, global navigation available today. In practical terms this means appreciable increases in navigational accu racy, savings in fuel, and reductions of pilot/ navi­gator fatigue .

For military aircraft, they also provide instantaneous velocity da ta for such functions as bombing, flight control,

VIPS Warning System

There will soon be a woman 's voice in the cockpit of the world 's fasted bombers .

The distinctive, w ell- modu lated feminine tones will come from VIPS, an ingenious "Black box" tucked into the warning system of the U .S. Air Force's B-58 Hustler bombers .

Unlike most airborne female voices which are generally associated with things like "coffee, tea or milk?", the V IPS voice will be an instant w arning to the B-58 crews in th e event of trouble somew here in the aircraft.

" Hydraulic System failure . . _ landing gear unsafe _ . . left manifold press ure low .. _ generator abnormal . _. canopy un locked ... ice forming . .. oxygen quantity low ___ " and some 45 other possible emergencies which might o ccur a board th e strategic air command 's big B-58 bombers w ill be instantl y reported to the crew by the clear, cairn female voice of VIPS.

VIPS, w hi ch stand s for Voice Interruption Pr ior ity System is now be ing prod uced by the Nortronics Division of North rop Co rpora tion under contract to General Dyna-

28

€; . (;,'I. f§J •fit fJ. - . --

-.: -~~- .· ..

fire control and landing. In commercial aircraft, Doppler navigation systems permit the pilot to limit his fuel reserve to 0 minimum, thus increasing the payload. Further, air traffic control could use smaller control blocks in high density areas if commercial airliners had the precise po­sition and veloc ity data provided by these systems. Of equal importance is the fact that pilots could select the optimum course, such as riding the jet stream, with the very accurate wind velocity and direction informat ion given continously by Doppler navigation systems.

(Laboratory For Electronics, Inc., Boston, Mass .)

mics Corporation, Fort Worth, builders of the record. setting B-58 Hustlers.

As a warning or alert system VIPS has a variety of applications. It is, of course, ideally suited for incorpo­ration into the safety systems of commercial transport aircraft as well as other military a ircraft, and can be used at missile launching sites, aboard ships and in conjunction with varied checkout systems.

Selected to record her voice for VIPS was Gina Drazin, a pretty Northrop secretary whose enunciation and pleas ­ant telephone manner made her an obvious choice .

The warnings are recorded on a 20-channel, electroni­cally-controlled, tape message unit for playback on a pre-selected, high priority basis. A woman's voice is used to record the messages to provide instant contrast between

warnings and the interphone conversations of the Hustler 's three crew members.

All messages begin with a different word. The result of human ~ngineerin~ studies is to obtain the most precise and easily-recognizable wording .

Northrop secretary Gino Drozin demonstrates the VIPS.

Northrop engineers designed and developed VIPS to solve the acute problem of effectively and quickly warning pilots in supersonic aircraft more of impending hazards.

C-Band Meteorological Radar Set AN-FPS 68

'"

J --.:.. -......, ---.: -

The VIPS system - a compact, light-weight package that can be held in the hand - represents a sharp departure from other warning devices which include flashing lights, buzzers and bells. For the first time VIPS gives the pilot verbal warning of possible trouble areas.

The VIPS logic network always selects and plays the message of greatest urgency so that the alarm of the most urgent hazard is triggered first, the second-most critical next, and so on.

Words rriost familiar to crew members are used. Mes­sages are short and to the point.

Preliminary flight test conducted at Carswell Air Force Base, Fort Worth, Texas, revealed enthusiastic pilot res­ponse and indicated a reduction in pilot reaction time for an average of 12 seconds, using warning lights only, to an average of three seconds, where VIPS also was used.

VIPS is credited with actually saving a B-58 during the series of flight tests of the warning system. Returning his B-58 to Carswell AFB in rapidly worsening weather the pilot heard a warning voice say "left manifold pressure low" followed by "alternator failure" and finally "hydrau­lic pump failure". The pilot immediately took corrective action soon enough to avert an almost certain crash.

(Northrop Corporation, Beverly Hills , Colif .)

. --·· ' - - -.. ·~( .r:,5 " .• • • i)-• ,, •• & • --

"' .. " • & - . • -- ~

~ :~· .. • •

" - J [ 6

] Iii ~ ...

l b ---- ---- • ---- .

'-'

Meteorological Radar Set AN-FPS 68.

29

MET

High powered, deep penetration prec1S1on Radar

Curtiss-Wright's C-Band Meteorological Radar is a high powered, precision, land-based radar designed to detect and analyze such weather phenomena as clouds, storms, hurricanes and other disturbances. The distingui­shing feature of this special purpose meteorological radar is the increased cloud penetration that develops more accurate data than can now be obtained with standard radar units.

"Unitized" construction for flexible installation

The Curtiss-Wright C-Band Radar set consists of a separate antenna assembly, receiver-transmitter-modulator unit, indicator console and remote indicator unit. This uni­tized construction permits physical separation of major systems and facilitates installation in accordance with specific computer requirements.

The receiver-transmitter-modulator unit may be housed with the antenna assembly or may be separated from the antenna's location by a distance of as much as 100 feet. This not only allows for simplified, economical in­stallations but offers the practical advantage of locating the lightweight antenna in the most ideal location with a minimum of installation problems. These advantages of separate unit location are accomplished without de­leterious effects on radar performance by using a faur port ferrite circulator which obviates the long line fre­quency pulling effects inherent in the more conventional systems.

Versatile modular design

The C-Band Radar was specifically designed with em­phasis on ease of repair, simplified maintenance, low inventory of replacement parts and future design change capability. These advantages have been made possible through optimized design and the use of a minimum num­ber of components.

. Simplified "Trouble-Shooting" Field operation is con­srderably simplified by the division of sub-assemblies into

"plug-in" modules that provide for quick and easy re­placement in the event malfunction. This makes possible the correction of malfunctions by operator technicians instead of specially trained trouble-shooting personnel.

Ease of Maintenance Modular component spares pro­vide an important "plus" where the location of the radar is in a remote or relatively inaccessible area. A centralized inventory assures installation of only pre-tested modules, shorter field maintenance time and tight inventory control. Long life and operational dependability are further assur­ed by maximum use of solid state devices. Completely solid state power supplies exemplify this technique.

Up-Dating Provisions If future requirements necessi­tate design changes to specific sub- systems of this radar, the modifications can be quickly and easily effected by altering only those module boards influenced by the de­sign change. This basic simplicity in design and con­struction eliminates the frequently costly and troublesome problems of design change inherent in present standard

radar sets.

Operational features

Three Scope Presentation Primary control is maintain­ed through operation of the indicator console which is equipped with Plan Position, Range-Height and Azimuth­Range Scope indicators. The Plan Position Indicator deve­lops signals that actuate the Range-Height and A-R Scope indicators. These signals are also reproduced on a second Plan Position Indicator in the Remote Indicator Unit.

Remote Control Capability The Remote Indicator Unit may be located at any position as much as one mile from the radar unit thereby providin,g a sec~ndary viewing station and increasing the radars operatronal flexibility.

Camera Provision By means of a special mounting provision, a record of cathode-ray tube displays may be obtained by mounting a camera on either the indicator console and/or the remote indicator.

Technical Characteristics

Range

Nominal maximum - 200 nautical miles.

Minimum - l nautical mile.

Accuracy of Maximum Range - 0.5%.

Resolution -1100 feet plus or minus 300 feet.

Determination - by interpretation of time difference measured between instant of transmission of the main pulse and arrival of the target echo signal.

Azimuth

Operational - Choice of 360° continuous CW rotation, or manual slewing control. Maximum speed shall be 5 rpm, plus or minus 1/2 rpm.

Accuracy - plus or minus 1°. Determination - By synchronizing PPI sweep with antenna rotation.

Resolving Power - Beam width (3 db points) nominal value of 1.58° at 5450 mes.

30

Elevation Operational - Automatic and Manual scan minus 20 to plus 60°, manual control. Accuracy - Plus or minus one half (1/2) degree. Determination - By synchronizing RHI sweep with an­tenna elevation and associated elevation indicator. Resolving Power - Beam width approximately (listed above) between 3 db points.

Transmitting Equipment Frequency - 5450 to 5650 mes. Peak power - approx. 300 KW. Average Power - Determined by m"gnet-on ef" · . . ~ ' rrcrency and pulse repetrtron rate with reference to peak power output. Pulse Repetition Rate - 324 pps plus or minus 1 pps. Pulse Length - 2 microseconds, plus or minus O.l micro­second. Source of R.F .. Power - Magnetron Oscillator Raytheon RK-7156 or equrvalent.

R.F. System

Antenna Reflector - Paraboloid, 8 foot diameter Reflector Feed - Horn Type Transmission Line - Wave guide suitable for pressuri­zation. Antenna Beam Width (Horizontal and Vertical) - Nominal value 1.58° at 5450 mes (3 db points) . Attenuation: Front to Back Ratio and Side Lobes - 20 db and 18 db respectively. Duplexing - Ferrite-duplexer (four-port circulator), bal­anced mixer and TR tube adequate to prevent crystal burnout.

Receiving System

Operating Frequency - 5250 to 5650 mes. Nominal I. F. Gain - 130 db (nominally). Local Oscillator - Klystron-Raytheon RK6115 or equi­valent. Noise Generator - Argon lamp Kay Electric Co. Catalog No. 271 -A or equivalent. Mixer (Signal) - Balanced crystal type directly coupled to pre i-f amplifier. Intermediate Frequencies (Signal and AFC) - 30 mega­cycles . Band Width (Overall) - 0.6 megacycles at 3 db points. Sensitivity Time Control - Provide 60 db reduction in gain out to 5 nautical miles, with exponential increase in gain.

Plan Position Indicator

Presentation - Standard PPI 12 inch CRT, high resolution, long persistence. Sweep Ranges - 30 60 120 and 200 nautical miles. Range determinatio~ _' 5 1

1

0 25 and 50 nautical miles range markers generated by a

1

controlled crystal blocking oscillator. Azimuth Scale - 0° to 360° around circumference of CRT, cursor for reading target azimuth. Isa Echo Contour - Settings of O to 30 db in 5 db steps, and 30 to 60 db in 10 db steps. Switchable on/off to PPI and Remote Indicator.

' l l ~ I

~-···~···~ Pion Position Indicator Chassis.

Range Height Indicator Chassis .

Range Height Indicator

Presentation - Standard RHI - 12 inch CRT, high reso­lution, long persistence. Sweep Ranges - 15, 30, 60, and 120 nautical miles. Range Determination - 5, 10, 25, and 50 nautical mile range markers generated by a controlled crystal blocking oscillator. Height Scale - 0-40,000 feet in 5,000 foot intervals and 0-80,000 feet in 10,000 foot intervals . Elevation Scale - Illuminated digital indicator.

Range Indicator and Ranging Unit

Presentation - A or R scope, 5 inch CRT, high reso lution . Sweep Ranges - 30, 60, 120, and 200 nautical miles. Range Determination - 5, 10, 25, and 50 nautical mile range markers generated by a controlled crystal blocking osci I later. "R" Range Positioning - Adjustable strobe on A scope sweep. Strobe Range - 0 to 150 nautical miles, with calibrated digital dial.

Remote Indicator

Presentation - Standard PPI 12-inch CRT, High resolution, long persistence. Range Determination - 5, 10, 25, and 50 nautical miles range markers . Sweep Ranges - 30, 60, 120, and 200 nautical miles. Azimuth Scale - 0-360° scale around circumference of CRT. Elevation Sca le - Read directly in degrees (illuminated digital indicator) located in freld of camera . G ain Control Set - Gain setting sha ll be displayed (use of coded pin lights) in field of camera . Time and Data - Digital type display ing time and d ate . Camero Adaptor - Supply trigge r w hen a ntenna faces north , for camera w ith open shutte r configurat ion .

31

" "' . e - ~ -

• • ·[ - ·

96) _ ..,. __ • • - -=-

- . ' . =• J •• -

AIR Scope.

{~~-~ -·~ - .c - 0·- - '• Antenna Positioning System

Azimuth Drive System - Servo controlled motor. Types of Operation - Continuous rotation, automatic and manual sca n. Continuous Rotation Speed - 5 rpm, plus or minus 1 / 2 rpm . Position Indicator - PPI sweeps indicate antenna position on azimuth dials.

Elevation Dr ive System - Servo controlled motor. Types of Operation - Automatic or manual scan from minus 2° to plus 60° in elevation. Automatic Scan Speed - 5 complete scans per minute. Position Indicator - Digital indicator on RHI and Remote Indi ca tor.

Power System

Primary Power Requirements - 115 volts plus or minus 10%, 58-62 cycles, single phase.

As we go to press .

Overload Protection - Circuit breakers, all primary cir­cuits, aircraft confrguration with trip indicators. Personnel Protection - All access doors interlocked with interlocks of the "Cheater" type. Shorting switch-door operated; to discharge capacitors in modulator high volt­

age supply .

Ventilation

Console - Fons with exhaust port to conduct heat from

unit. . RTM _ Lorge blower with separate ducts for magnetron

and local oscillator. . Remote Indicator - Air blowers.

Unit Separation

The R-T-M Unit will be located within 100 feet (max.) of the Antenna Assembly. The console will be remotely locat­ed from the R-T-M up to a distance of 2600 feet max. The Remote indicator shall be capable of operation up to a distance of 5300 feet max. from the console unit.

Antenna Reflector.

l 7th Conference of the International Federation of Air Line Pilots Associations, Stockholm

From March 27th to April 3rd the Internat ional Federa­tion of Airline Pilots A ssociatio ns held its 1962 Annual Conference in Stockholm.

Captain C. C. Jackson , Exec utive Secretary of IFALPA, had already in October 1961 extended a kind invitation to IFATCA to delegate an observer to the Stockholm Con­ference.

32

IFATCA Treasurer Henning Throne attended IFALPA' Conference in Stockholm, and an initial report from hi~ reached the editor just before we went to press . It is

0

ver.y promising one as it reflects the good spirit of coope­ration Mr. Throne encountered in Stockholm. Details will be published in the next issue of our journal.

r~

MARCONI

* Gives longer range for given transmitter power

* Penetrates thick weather without loss of efficiency

*Permits M.T.I. elimination of permanent 'clutter '

* Switches into instant operation

AIR TRAFFIC CONTROL SYSTEMS SURVEYED · PLANNED · INSTALLED · MAINTAINED

MARCONl'S WIRELESS TELEGRAPH COMPANY LIMITED . CHELMSFORD . ESSEX . ENGLAND S6

M e y r i n GE

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In d e r Arkti s und A n tar ktis , , , Osterreich und Australien . . , auf den Aleut e n und in Argentinien , ., bei Flugzeu g ­h e rstellern und L uftverkehrsgesellschaften

Land-, Luft- und Seestreitkrafte sowie der Luftverkehr verwenden sie Hir

Jet-Anflug Jet-Steigflug Lenkwaffenuberwachung Bomben-Zielwurfubungen Rollfelduberwachung Hohenmessung lnstrumentenlandung in Gegenrichtung Anfluge auf verschiedenen Pisten Freun d-Fei nd-Kennung Luftraumuberwachung Praz isionsanflug Ortsfest oder mobil

in Holland Norwegen Jugoslawien Japan Korea Argenti n ien Australien Osterreich Kanada Danemark Irland Finn land Frankreich Deutsch land Israel I ta lien Nordafrika Neuseeland USA auf den Aleuten und am Sudpol

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