IFATCA JOURNAL

OF AIR TRAFFIC CONTROL

Determinants of Our Air Traffic Control Systems: Improved Equipment Performance

Redevelopments Toward Future Requirements

TE LE FUNKE N developed a new Precision Approach Radar System improving the range coverage from 10 NM to 12 NM.

The transmitter power was increased and the receiver sensitivity improved. The elevation reflector provides coverage in the

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IFATCA JOURNAL OF AIR TRAFFIC CONTROL

THE CONTROLLER Frankfurt am Main, April 1966 Volume 5 · No. 2

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

Officers of IFATCA: L. N. Tekstra, President; G. W. Monk, Executive Secretary; Maurice Cerf, First Vice President; Roger Sadet, Second Vice-President; Ernest Mahieu, Hon. Secretary; Henning Throne, Treasurer; Wolter Endlich, Editor.

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

Production and Advertising Sales Office: W.Kramer&Co., 6 Frankfurt am Main NO 14, Bornheimer Landwehr 570, Phone 44325, Postscheckkonto Frankfurt am Main 11727. Rate Cord Nr. 2.

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

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

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

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

Contributions ore welcome as are comments and criti­cism. No payment con be mode for manuscripts submitted for publication in •The Controller•. The Editor reserves the. right to m.ake 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 port of this Journal.

Advertisers. in this Issue: Aeroplastic H. Pfutzner (11,39); Decca Navigator Co., Ltd. (Inside Back Cover); Marconi Co., Ltd. (3, 4); N. V. Hollandse Signaalopporoten (2); Plessey Radar, Ltd. (Bock Cover); Selenia S. p. A. (17); Solartron Electronics Group, Ltd. (15); Standard Elektrik Lorenz AG (l); Standard Radio & Telefon AB (22); l ele­funken AG (Inside Cover).

Picture Credit: Air Transport Association of America (14); Dr.-lng. Hell (33); Federal Aviation Agency (34); U.S. Weather Bureau (7); Tirey K. Vickers (6, 8, 9, 10, 24, 25, 26, 27).

CONTENTS

We're learning more about Clear Air Turbulence .. · · · · · · · ·

Tirey K. Vickers

l 6th Annual Conference of the IANC

Some News on Airborne Collision Avoidance Systems · · · · · ·

Status of Airline Radar Beacon Transponder Capability

IFATCA Corporation Members

Airborne TV tested as ATC Aid

Max Karant

.....................

.......... . . . . . . . . . . .

6th Annual Conference of the Austrian Air Traffic Control-

lers' Association .................................. .

Radio Communication Failure Procedures Reviewed

New Council of the Danish Air Traffic Controllers' Associa-

tion ....... · · · · · · · · · · · · · · · · · · · · · · · · · · · · · ·

Wind Shear Problems in Terminal Operations

Tirey K. Vickers

Separation Minima Reviewed .................. .

New Control Tower and Runway at Orly

· · f I f t' o Marginal Weather Rapid Dissemination o n orma ion n

Conditions at Airports · · · · · · · · · · ·

Book Review ......... · · · · · · · · · · · ·

IFATCA Adresses and Officers

6

10

12

13

16

18

19

20

22

24

28

31

32

36

38

We're learning more aboutClearAirTurbulence

Significance Clear Air Turbulence {CAT for short) costs the US air­

lines over 818 million per year in personal injuries, flight diversions, extra training and aircraft inspections. And not so long ago, the CAT problem came very close to grounding a large portion of the USAF deterrent fleet. Consequently, a large amount of money and effort is be­ing poured into CAT research projects.

On February 23 and 24, 1966, in Washington, the In­stitute of Navigation and the Society of Automotive En­gineers sponsored a National Air Meeting on Clear Air Turbulence, to review the progress which has been made in this field. The meeting attracted a total attendance of 335, including 23 visitors from 10 other countries. In the following article we will summarize the information which was presented at this meeting.

Characteristics CAT is presently defined as any atmospheric turbulen­

ce above 20,000 feet MSL which is not associated with convective-type clouds or thunderstorms. More CAT is found in winter than in summer, more over land than over sea, and relatively more over mountain areas than over flat country. The latter characteristic implies that terrain irregularities can trigger off the turbulence; this is cer­tainly the case with the most violent form of CAT, the mountain wave, which is shown in Figures 1, 2 and 3. Here the initial disturbance and the additional waves which form downwind resemble the eddies and ripples which form downstream from a submerged rock in a swiftly

flowing river. Nearly a million miles of high-altitude flying by U-2

aircraft indicates that a greater amount of CAT is found between 30,000 and 40,000 MSL, than in any other layer above or below. The probable reason is that the jet

by Tirey K. Vickers Director, Air Traffic Advisory Unit Decca Navigator System, Inc.

stream, a potent generator of CAT, operates within this band of altitudes. The U-2 data indicates that turbulence decreases both in intensity and amount at the higher altitudes. For example, above 50,000 feet, less than 2% of the U-2 flight distance was in turbulence.

Scientists of Douglas Aircraft believe that CAT is a direct result of wind shear {differences of wind direction or velocity in adjacent layers of the atmosphere); when the shear reaches a critical value, the flow becomes tur­bulent in the form of cells or eddies which drift away from the source region and gradually dissipate downstream.

However, some so-called CAT may not be turbulence at all, but may simply be the result of a flight path which happens to skim through an undulating or wavelike boun­dary between two slightly dissimilar air layers, as shown in Figure 4. If the two masses are moving at different speeds or in different directions, the aircraft encounters an abrupt change in airspeed each time it crosses the boundary. An increased airspeed produces more lift and a positive (upward) acceleration, while a decreased air­speed produces the opposite effects. If there is a differen­ce in wind direction between the layers, the aircraft will experience lateral accelerations also.

CAT is an elusive thing, impossible to detect from the ground, using present radiosonde techniques. When CAT occurs, it is often scattered through areas 50 to 100 miles long. Within these areas it is patchy and highly localized in nature. In most cases the individual patches are seldom more than 2000 feet in depth, and a fairly small change in flight level may enable the aircraft to avoid the distur­bance entirely.

Many air traffic controllers have noticed that during periods when CAT is present, there is often a wide varia­tion in the CAT intensity reports from successive aircraft passing through the same airspace. Part of this difference is due to the patchy nature of the disturbance itself, but there are other reasons as well.

r-w~ L L

Fig. 1 Mountain waves (also known as lee waves or gravity waves)

Legend: w .CC° Wave length (normally 1 to 30 miles); L = Lenticular (lens-shaped) cloud; R Rotor zone (often marked by rotor cloud)

6

Fig. 2 Lenticular cloud of mo untain wave, with small rotor clo ud beneath U. S. Weather Bureau Photo

Just os o Rolls-Royce, o Volkswagen, ond o Hondo will respond diffe rently to the chuckholes ond undulations of a given roadway, different types of aircraft will respond differently to the same CAT conditions. Also, aircraft re­sponse may vary with different airspeeds, and with diffe­rent gross-weight conditions. Sometimes individual crew members do not agree on the intensity encountered. Each

Fig. 3 Televised photo fro m Tiros 5 sate ll ite showi ng mountain wa ves genera ted in lee o f Appa lachia n Mo unta ins. La ke Erie and La ke O nta rio ore visi ble near top o f p ie· lure. Coasts of New Jersey a nd Maryland are v isible just be low center crossmork. Dots show position o f W a ­sh ington (W), Pittsburgh (P) and Hunt ington (HJ. Wove· length o f the moun tai n wa­ves was about 12 nautical miles.

U. S. Weather Bureau Pho to

pilot tends to judge the intens ity on the basis of his train­ing, experience, ond individual me ntal reactio n.

As the first step toward a more standardized method of reporting CAT, the National Ae ronautics ond Spa ce Administration (NASA) has suggeste d the criteria listed in Table 1.

7

Description

Very light

Light

Moderate

Severe

Extreme

Table 1 - CAT Intensity Criteria

Symptom

Perceptible

Slight discomfort

Difficulty in walking

Airspeed Fluctuation in Knots

Less than 5

5 to 15

15 to 25

Loose objects dislodged Over 25

Aircraft violently tossed Over 25 with around, impossible to rapid changes control, possible structural damage

Detection Problems

A large percentage of the present CAT research ef­fort is being directed toward the goal of developing an airborne device which will detect CAT far enough ahead of the aircraft to give the pilot time to initiate action in evading the disturbance or in alleviating its effects. This warning function implies that the device needs a detection range of at least 20 miles for present subsonic jets and

Warm Air

about 50 miles for SST aircraft. Meeting this requirement is an extremely difficult scientific problem; clear air does not contain the concentrations of particulate matter (rain, hail, and snow) which enable present radars to detect the most turbulent areas of thunderstorms. Consequently, CAT is as invisible to a conventional radar as it is to the naked eye.

Side effects or clues which might be used to differen­tiate turbulent clear air from non-turbulent clear air are difficult enough to detect at close range; to be able to do this from 20 to 50 miles away is fantastically difficult. But even if adequate detection range can someday be attained, there comes another problem equally important - to be able to determine whether or not this turbulence will affect the intended flight path of the aircraft.

Here is a significant difference between the problems of thunderstorm avoidance and CAT avoidance: Thunder­storms may extend through 30,000 feet of altitude, while CAT is usually limited to less than 3000. Unless the air­craft passes through the same strata, the disturbance will not affect it. The point here is that pilots cannot be expected to rely on an airborne warning system unless it can demonstrate a high rate of successful warnings a n d a low rate of false alarms.

~ ~ ~ ::7 -- ~ ----~-~-~~Flight Path

Cold Air Fig. 4 Warped interface between air layers

CAT Sniffers Perhaps the simplest technical approach to CAT de­

tection is the one being tried by Eastern Air Lines. This approach exploits the fact that jet streams (a primary source of CAT) are usually accompanied by a temperature change of the surrounding air. In this approach, the pilot uses a very sensitive, compensated free-air thermometer system called TRAPCAT (Temperature Rate Alarm for Predicting Clear Air Turbulence). At constant altitude and cruising speed, a temperature change of on_e ~egr~e Cen­tigrade in one minute is a fairly accurate 1nd1cat1?n ~hat the aircraft is headed for a CAT area. Eastern Arr Lines characteristically flies north-south routes which tend to cross the jet stream. It will be interesting to see wheth~r the TRAPCA T principle will prove sufficiently accurate in determining the proximity of other forms of CAT as well.

A number of CAT detector designs employ some form of electronic radiation to scan the airspace ahead of the aircraft. Various bands of the frequency spectrum are being tried, including VHF, UHF, microwaves, infra-red, and visible light waves. Such systems emit a pulse of radiation and then hopefully search the return for some

evidence of CAT. Some of these systems monitor the intensity of the

return some measure the Doppler shift of the reflected signal: while other systems depend on such _exotic techn_i­ques as measuring the absorption properties. of certain types of molecules in the atmosphere to determine the tem­perature of the air ahead of the arcraft; detecte? ~hanges in air temperature are then used for CAT predrctron.

At the high end of the frequency spectrum, optar (opti-

8

col radar) systems scan the airspace ahead of the aircraft, with a powerful laser beam. However, the proponents of this technique apparently have given little consideration to the fact that the output of a high-powered laser is a baby Death Ray which can permanently damage the eyes of ~nyone within range who happens to be looking direct­ly into the beam. Spraying this kind of energy around in today's traffic environment appears to be a highly que­stionable practice.

All CAT detectors which scan the airspace ahead of the aircraft to determine air temperature probably will require a highly stabilized antenna to insure that the scanning beam will remain horizontal at all times. A slight deviation from the horizontal would cause the beam to scan through other altitude layers which could have a to­t~I tempe~ature gradient much larger than the tiny gra­dients which the system depends upon for detecting CAT.

Stanford Research Institute has discovered that electri­cal d'.scharges from the aircraft's wingtips and tailtips s~n:ietrmes occur near CAT areas, particularly in the vi­cinity of the jet stream. It remains to be seen whether this principle can provide a reliable remote indication of CAT, and a sufficiently low record of false alarms.

On.e particularly far-out technical approach to CAT detection would use an automatic star-tracker to monitor the scintillation of a star on the horizon ahead of the air­craft, on the theory that any intervening CAT area will change the refraction of the light waves and cause the star to twinkle. As shown in Figure 5 however the tracker inevitably is looking a vast distan~e through the atmo-

(

Relevant CAT

( Irrelevant CAT

* ~;ta

~

-

/ Fig. 5 Star-tracking CAT detection concept

sphere; it is also looking through a vast range of altitude levels besides its. own. Conceivably, air turbulence at any point along the line of sight could cause the star image to scintillate. Thus it appears that the false-alarm rate of such a system would be very high indeed. (Twinkle, twink­le, little CAT, I wonder where you're re a 11 y at?)

Forecasting

Most of the CAT detection schemes under development appear to be tremendously complicated and expensive to implement. Individually, they may be so limited in ap­plication that it would be necessary to combine two or more different sensing schemes, with their outputs proper­ly weighted by a computer, in order to maintain an ade­quate score of successful warnings versus false alarms .

. Because of this inherent complexity, the most practical approach to CAT avoidance may lie in the field of im­proved forecasting, rather than inflight detection. For example, Eastern Air Lines has found that the reliability of their CAT forecasts can be improved considerably by taking into consideration any trough of minimum tempe­rature which appears on the 200 to 300 millibar charts. Where such a trough intersects either the jet stream, or a pressure trough, or the edge of a large shield of hi~h cloud cover, CAT is highly probable; in most cases its altitude will coincide with the altitude level which has

the greatest amount of wind shear. In recent years, United Air Lines and Northwest Air

Lines have made extensive studies of the mountain wave conditions which prevail on some of their routes. This work has culminated in the publication of a new rep~rt, which contains an analysis of 169 different mountai~­wave generating sites. It is expected that the mountain wave situation can now be predicted accurately, ov_er a wide range of meteorological conditions, so that flights can be given altitude and route revisions which will ke~p them out of the most turbulent areas. A familiarity with this report, by pilots, dispatchers, and air route traffic controllers, should help greatly in reducing the exposure of aircraft to mountain wave turbulence.

Before long it may be practical to confirm mountain wave forecasts through the use of satellite photographs similar to the one shown in Figure 3. This technique is not used operationally yet, because 6 hours are present!~ re­quired to process and distribute the satellite data in a form suitable for forecasting purposes. Within a year, however, it is expected that the delay can be cut to l-1/i hours.

Horizontal line of sight to star

Flight path

Flight Techniques

As the result of a series of jet upsets in turbulence a few years ago, piloting techniques were modified to cope more adequately with all types of turbulence.

The higher the airspeed, the greater the strain on the aircraft when it encounters rough air. Thus it is prudent to reduce airspeed when an encounter with turbulence is imminent, or in progress. An analysis of early jet upsets showed that pilots were occasionally getting the aircraft into a stall buffet condition in rough air, particularly at high altitudes, where there is relatively little spread be­tween the high-speed buffet and the stallspeed buffet condition.

Subsequently, the recommended turbulence penetra­tion speeds were revised slightly upawrd. They now form what should be the best compromise between the follow­ing factors:

High speed Good control Maximum stress

Versus

Low speed Poor control (Danger of stall) Minimum stress

In a strong updraft as shown in Figure 6, the wingtips of a swept-wing jet tend to bend and twist to a lower angle of incidence, thus producing less lift. Meanwhile the center section of the wing (which is farther forward than the swept-back tips) continues to lift normally. Thus, the aircraft temporarily becomes tail-heavy, and starts to pitch up. In early encounters with this phenomenon, pilots used full forward stick and then tried to bring the nose down by retrimming the aircraft with the stabilizer. When the nose finally started to come down, the now nose-heavy aircraft accelerated into a screaming dive before the pilot could re-trim the stabilizer. Some of the wrecks were found with the stabilizer still in the full-nose-down-trim position.

Consequently, pilots are now taught to avoid any use of the stabilizer trim switch in such encounters; and some jet aircraft have been modified to limit the amount of stabilizer control available to the pilot, when using the handy "pickle switch" on his control column.

It was found that in severe turbulence, pilots could receive false pitch clues if they concentrated too much on the altimeter. As a result, pilots are now taught to fly the attitude indicator as the primary instrument during turbulence encounters. They are also taught that, under such conditions, the "Three As" of instrument flying

9

should be considered in the following order of impor­

tance: 1. Attitude 2. Airspeed 3. Altitude

Conclusion So far, no CAT detector has demonstrated a confi­

dence level sufficient to justify its operational implemen­tation. The physics of CAT are still poorly understood. Much has yet to be learned about the basic parameters (there are at least 55 of them) which influence the genera­

tion of CAT. However, if we consider how much has been learned

about the subject during the past three or four years, we

Wingtip Section

Center Section

Fig. 6 Deflection of swept wing in updroft Updraft

can still be optimistic. Maybe we'll never get a foolproof CAT detector. But meanwhile, further improvements in forecasting and piloting techniques could greatly reduce the operational hazard of clear air turbulence.

* * *

16th Annual Conference of the International Airline Navigator's Council

The 16th Annual Conference of the International Air­line Navigator's Council (IANC) was held in Paris from lst to 3rd March, 1966. IFATCA Vice President Maurice Cerf attended the Conference, and the following are some

highlights of his report: -

"The reduction of lateral separation over the North Atlantic is a very timely subject and, naturally, ranged on top of the agenda items. The IANC is opposed to this re­duction of separation, as long as there is no fully quali­fied navigator on board the aircraft flying the North At­lantic. Thus, there is quite a difference in opinion between the International Federation of Airline Pilots and the In­ternational Airline Navigator's Council, although both or­ganisations are aiming at the same goal.

In fact, IANC advocates that the lateral separation could well be reduced, even below 90 NM, provided that the navigation accuracy was checked by a professional

navigator. As a result of these discussions, the Conference trans­

mitted the following telegram to ICAO: 'With reference to the reduction of lateral separation in the principal areas of the NAT from 120 to 90 NM, IANC strongly pro­tests the implementation of this standard consistent with our position at the special NAT/RAN meeting on separa­tion standards in February/March 1965 and again at the 4th Al R/NAV Conference in November 1965.

IANC believes that if all operators concerned em­ployed I icensed navigators and provided adequate air­craft equipment, using existing aids, the 90 NM would

become acceptable. IANC is convinced that not all NAT operators are con­

sistently navigating to an accuracy compatible with a

90 NM standard. Until such time, IANC urges that 120 NM lateral sepa­

ration be reinstated. (Letter to follow.) The President."

In the letter sent further to the telegram, IANC suggest that operntors should be classified into two categories -one being approved for 90 NM, unrestricted in the prin-

10

ciple area, the other category being restricted to 120 NM, limited to flight levels below 290 in the principal area, operating at off-peak periods or on tracks outside the principal areas.

Throughout the meeting one could note some diffe­rence of opinion between airline pilots and airline navi­g?tors. ~or instance, while IFALPA requests a pictorial display in the cockpit, to monitor the accuracy of the flight, IANC maintains that this accuracy could be gua­ranteed by a man: the navigator.

The meeting also concerned itself with proper crew complem~nt. The present needs for pilots, it was conclu­ded, particularly in the USA, is a direct consequence of the decision to dispense with the services of flight navi­gat~rs and flight engineers, and many pilots are not available now because they are being trained as naviga­tors.

IANC is of the opinion that it would be more economi­c~! to re~erse this trend by resuming the recruitment of flight navigators and flight engineers.

The Conference had a world-wide attendance, some delegates coming from as far as Australia and Japan.

The British Ministry of Aviation was represented by Mr. Brown, and Mr. Boisseau represented the French Se­cretary General for Civil Aviation.

The following Officers were elected by the Conference to serve the International Airline Navigator's Council dur­ing the coming year: -

Chairman

Ex. Vice Chairman

Executive Secretary

Honorary Treasurer IFATCA Liaison Officer

- Mr. R.H. Savage (QUANT AS)

- Mr. R. Waldman (Al R CANADA)

- Mr. C. Gullen {BRITISH UNITED)

- Mr. Archer - Mr. A. Magnee (SABENA)

The next Annual Conference of the International Air­line Navigator's Council will be held in London.

M.

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Some News on Airborne Collision Avoidance Systems

According to the Air Transport Association of America (ATA), long time airline goal to find a suitable airborne device to help prevent mid-air collisions is now closer to realization than at any time in the past. The device would be used to complement the air traffic control system and reduce even further the present low risk of mid-air colli­sions.

One manufacturer - McDonnell Aircraft of St. Louis, Missouri - has developed a collision avoidance system for use in specialized flight test operations with its air­craft. The McDonnell development is a cooperative system: the "intruder" aircraft must carry cooperating collision avoidance equipment so that the equipment aboard the "protected" aircraft can determine the collision threat posed by the intruder. The system uses the time-frequency technique, which ATA claims to be the most promising technique for cooperative collision avoidance systems. In a time-frequency system, each aircraft is assigned its own individual time to transmit on a common, shared fre­quency.

In its present form, the McDonnell system is not suit­able for airline use, but for over three years the airlines and McDonnell have been examining ways to make it suitable.

Airline interest in collision avoidance systems goes back many years. In 1955, the ATA asked the electronics industry to submit proposals for a non-cooperative colli­sion avoidance system. In 1965, the airlines accepted a manufacturer's proposal and placed orders that would have ultimately resulted in an airline outlay of 810 mil­lion. Later development work showed that a non-coope­rative system was beyond the current state of the art and the manufacturer withdrew the proposal.

Since then, the airline goal has been to find a coope­rative collision avoidance system that is suitable for in­stallation in civil and military aircraft, and compatible with the air traffic control system operated by the FAA. The attempt to find suitable techniques has been a coope­rative effort involving the airlines, the manufacturers and the FAA's Research and Development service.

Some background information

A collision avoidance system (CAS) is a device carried on board an airplane to assess the probability of collision with other aircraft in flight. Its purpose is to provide an assessment of collision risk that is independent of the pilot's visua I assessment and independent of the ground­based air traffic control system.

A collision avoidance system detects a potenial colli­sion hazard, calis a pilot's attention to the hazard, and displays the evasive action he should take to avoid colli­sion with the intruding aircraft. CAS should not be con­fused with a pilot-warning indicator (PWI), which merely tells the pilot where to look and leaves to the pilot both the detection of the intruder and the choice of evasive action.

12

Working Principles: The system must gather informa­tion about other aircraft in nearby airspace. The system must sort out this information and determine which air­craft, if any, pose a potential collision threat. To detect a potential collision, the equipment must determine that an intruder is, or will be, at the same altitude, and is fly­ing a path that - unless changed - will produce a colli­sion. Even when both planes are flying straight and level, the technical problem of collision detection is compli­cated, but when one or both aircraft are turning, climbing or descending, the technology becomes even more com­plex. Some form of airborne computer is required to as­sess the problem, predict the possibility of collision in a matter of milliseconds and, at the same time display to the pilot the evasive action he should take.

System Types: Two general types of collision avoi­dance systems have been considered since the airlines began their study of techniques 11 years ago.

Non - cooperative : where the threat of an in­truder can be determined without requiring the intruder to carry CAS equipment.

Cooperative : where cooperating equipment in the intruder aircraft is essential for determining the colli­sion threat posed by the intruder.

Ideally, a non-cooperative system is most desirable, because it gives immediate CAS benefits to its users. They can get CAS service without having to depend upon the equipment carried by other aircraft. It is universally a­greed that, with the current state of the art in collision avoidance, a practical non-cooperative system is nowhere in sight. For this reason, ATA interest in the past few years has focused on techniques for cooperative systems.

Range-Altitude Techniques: A variety of CAS techni­ques have been proposed and some cooperative systems have been tested experimentally under FAA contract. The more promising family of cooperative techniques mea­sures range, the rate of change in range (range-rate), and altitude. All equipped aircraft transmit and each one picks up transmissions from all the others. If the range of any two aircraft is less than a predetermined maximum dis­tance, and the two altitudes are within specified limits, the computers in those aircraft process the rest of the trans­mitted message and each determines if the other aircraft is an intruder. The computer determines the intruder's "time to go" before a collision will occur unless evasive action is taken. The computer also advises what escape maneuver to use, and tells when the potential collision has been avoided. Known as the "range-altitude" method, this family of techniques does not try to measure - or take into account - the relative bearings of the two air­craft. ~he resul'. is a method that is far less complex than one using relative bearings.

Time-frequency System: With this range-altitude fami­ly, there are three often-discussed techniques. One uses a transpond~r in the protected aircraft to interrogate equip­ment earned aboard each intruder. The intruders reply

with their range and altitudes. In another technique, alti­tude pulses are transmitted simultaneously from each in­truder to the protected aircraft (1) directly and (2) by re­flection from the ground. This "ground-bounce" signal reaches the protected aircraft later than the direct signal. The time difference is used to measure range of the in­truder.

In the best range-altitude technique, aircraft transmit their altitude on a common frequency at very precise times. These times are assigned, and known to the air­borne CAS computers. So the difference in microseconds, between assigned time of transmission and actual time of receipt by the computer is used to determine distance to the transmitting aircraft. At the receiving aircraft, the fre­quency of the received signal is observed to have under­gone a slight but measurable shift from the common fre­quency used for all transmissions. This shift varies with the relative speeds of the two aircraft and therefore gives their rate of closure. The computer divides distance by rate of closure, to predict "time to go until collision".

This "time-frequency" technique requires great preci­sion in both time-keeping and frequency used. Each air­craft must carry an accurate frequency standard and the system requires a practical method for synchronizing the timekeepers aboard the aircraft at appropriate intervals. What is needed is a way for all airborne units to agree on zero time within one part in ten million, or better. The use of ground stations with time standards to synchronize airborne timekeepers is less attractive operationally than air-to-air synchronization because it precludes universal use of CAS - i. e., over ocean areas beyond the commu­nications range of ground stations.

What makes the time-frequency technique attractive is that it greatly simplifies the computation problem. It also holds down the communications load. With time-frequen­cy, the communications load increases as a linear function of the increase in number of equipped aircraft. By con­trast, with the transponder technique the communications load increase exponentially with number of aircraft using the system. ATA

* * *

Status of Airline Radar Beacon Transponder Capability, based on January, 1966 ATA Survey

To determine the current status of airline programs to fit their aircraft with various elements of the airborne portion of the air traffic control radar beacon system, the Air Transport Association of America recently con­ducted a survey among US airline operators. These ele­ments are building blocks that begin with the simplest 64-code transponder and end up with equipment that makes possible automatic reporting of the aircraft's identifica­tion and altitude. The building blocks that must be added to a 64-code transponder to achieve this capability are:

4096 code capability;

electronic circuitry for altitude reporting;

digitizers for digital encoding of altitude informa­tion so it can be transmitted to, and used by a computer receiving it at the air traffic control cen­ter; and

3-pulse side lobe suppression (SLS) - electronic circuitry to suppress interfering signals and give clearer target on controller's radar scope.

Response: All 42 ATA member airlines were contacted. Those replying (28) include the domestic trunks, interna­tional carriers, and most of the local service airlines -in short, virtually all airlines using the ATC Radar Beacon System in the continental U.S. replied to the survey.

Existing Fleet: 1645 aircraft reported on. Of these, 1323 (81 per cent) are now equipped with ATC radar beacon

transponder.

64 code capability operational 4096 code capability operational

Total

924 399

1323

Altitude reporting capability now operational - 92. Of the 1323 transponder-equipped aircraft, 742 now

have altitude reporting electronics in their transponder and 875 have 3-pulse SLS operational.

Retrofit Plans: Airlines expect to retrofit 4096 code ca­pability and 3-pulse SLS in additional aircraft in the pre­sent airline fleet, on the following schedule:

1966 - 99 1967 - 121 1968 - 311 1969 - 59

Altitude reporting is planned to be operational on these aircraft on the following schedule:

1966 - 9 1967 - 33 1968 - 320 1969 - 183 1970 - 59

Plans for New Aircraft on Order: 626 aircraft, mostly turbojets, are on order by the airlines responding to the survey. Virtually all will have 4096 codes and 3-pulse SLS operational on delivery.

Their altitude reporting plans at this time are:

79 will have altilude reporting operational on deli­very (date unspecified).

122 will have altitude reporting operational in 1967. 165 will have altitude reporting operational 1n 1968.

43 will have altitude reporting operational 1n 1969.

No frrm plans yet for the remainder.

13

4096 codes,

Alt. Reptg.

Alpha

Numerics

1500

~ 1000 ~

~ Cl)

c: -.:: ~

0 ~

..0 E

z

500

CJ c Cl)

u ..Y.

0 >-~ Cl)

z

Jan '66

E 0 0

0:::

~ c: 0 E E 0 u >-z

Jan '67

< <n < z x ~

Jan '68

a; co

-0

0 ~ 0 .D Cl) 0 CJ ·= <n c

"' c: olS 0 Cl)

~ :;:

c c: Cl) 0

0 u UJ .=

/

/-•

Jan '69

Jan '70

0 "' ·= Cl)

E x

~ Cl)

a. I- e Cl)

~ > u: ::.E

4096 Code Capability

Altitude Reptg. Operational

64 Code Capability

U.S. Airline Survey

ATC Radar Beacon, Present Capability and Plans

The chart shows how the airline program to improve the radar beacon capability of airline aircraft matches current FAA plans to provide ground facilities that will use the information from the airborne equipment. The 4096 code capability will allow controllers to assign each flight an identifying code number which will be automatically recognized by the air traffic control computer and dis­played alongside the target. Altitude reporting capability will allow the airplane's altitude, plus a symbol to show if it is climbing or descending, to be also displayed auto­matically beside the plane's radar target. Portions of this ground system capability will be available in 1966 at the New York Center: the complete capability will be ope­rational when the New York Common IFR room (for ter­minal area control) is completed in 1967.

14

"JAX NASA" refers to the Jacksonville, Florida, Air Route Traffic Control Center installation of Stage A, Na­tional Airspace System (NAS). This is the frrst operational application of the advanced radar beacon system to high, medium and low altitude en route traffic. This en route application will spread later to other traffic control cen­ters on the Eastern seaboard and along the main trans­continental air routes.

The frve metroplexes, or large terminal areas with multiple airports and heavy air traffic, are slated to get an improved version of the ground equipment installed earlier for New York. As one of the frve metroplexes, New York will also have improved ground equipment in the post-1970 time period.

A-A

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L_ i6

Corporation Members

of the International Federation

of Air Traffic Controllers' Associations

The Air T raffle Control Association, Washington D. C., U.S.A.

Cossor Radar and Electronics Limited, Harlow, England

The Decca Navigator Company Limited, London

ELLIOTT Bros. Ltd., London

IBM World Trade Europe Corporation, Paris, France

ITT Europe Corporation, Brussels, Belgium

The Marconi Company Limited Radar Division Chelmsford, Essex, England

N.V. Hollandse Signaalapparaten Hengelo, Netherlands

Philips Electronics, Netherlands

Selenia - lndustrie Elettroniche Associate S. p.A. Rome, Italy

The Solartron Electronic Group, Ltd. Farnborough, Honts., England

Telefunken AG, Ulm/Donau, Germany

Texas Instruments Inc., Dallas 22, Texas, USA

Whittaker Corporation, North Hollywood, California, USA

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

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

field of air traffic control.

... four hund1·eds years ago ...

the British Is les were saved from the Spanis h Arma da by smoke signals · Indian type. In this age of ours, when modern jet-ai rcraft fly fas ter than sound, there is no be lier solut ion to Air Defence problems than

instantaneous handling of coded messages, automat­ically ex tracted from rada r and other senso rs , digitaliL­ed, processed by computers and t ransmitted to O].Jera­t iona l cen lers where vita l decisions a re to be taken.

S ele11ia will solve yo11r Air De fence problems by e111ploy ii1g a 1Vide range of field tested, consolidated equip-111e111 to form the building blocks of you r Air Defence S y stem.

Selenia Air Defence Ground Environment Systems

DATA HANDLING Solenla's engineers have acquired first closs experience in appl ying dB· ta handling In Air Defence and Na· vnl Operations projects. Thei r knowledge and experience Is devoted at the present time In solv­ing the automation problems posed by 11 variety of military and civilian apphcotlons. (see center column: A Solcnla Spacial Purpose Digi tal Computer. The Hawk PAR acquisi tion radar) .

A Solenla high -power, L·b ond rador Is housed In this Interesting struc· ture (photo above). It provides long range as well as high altitude close ronge coveroge thus meeting the most stringent rcqu1rements posed by su· personlc olrcrah .

TELECOMMUNICATIONS From Sweden to Omon, f rom Sardi· nia to Molayslo the paraboloids or Salonia radio llnks span the coun· trys1de. They are but one evidence of the vcrsat lllty nod f lexlbfllty ol our development and mal"lufacturlog

sot up. rsee left obovel.

~~S1~!~o~~t1on 01 Hiawk btHtorl es In western Europa w.'ls on lmport~nt step forword for the dotencc of the Free World. Sclenlo has been Instrumental In setting up nnd canylng out a con-31dor~blo portion of the H~wk

gnun In Europe.

CONSOLES A t ype of console and associated control units provided by Sclcn1a are shown In rhe ptcrures abo .. ·e and on the right. On our 12· · CRT displays the radar video blips can bo made to oppear simultaneously or >'1811ernatlvely with various synthet ic alphanumeric sym· bols. with greot accuracy (bener thnn I thousondth ol tube dlamelerJ and speed (7 .usec for any symbol displacement) . The translsto rls311on and dlgitallsa· t ion techniques applied allow the OP· t imum in simplicity of operation. m.ilntenance and space saY1ng togeth· er with o very high degree of re· lloblltty. lsee below: the CRl d fsplay) .

ALREADY ON RECORD: . . I I a1tdlmg Prese11 t Seleniti's backlog of orde~s I!' tlte fi eld of 0 ata.11

1 dol­eq11ipmcnt for Military project s 1s 1n excess of 2 '$1£~0'( Data /ars o Selenia ltas developed a11d manufactured

1 f t

Se/e11ia lws take11 part i n tlte develop111e111 of tlte SIDA ,;yste111 ( f 11t e~ rated Air Defence Sys1e111) for ll1e I w/ia11 Air _Force . Sele11ia has also been awarded a co111rac1 by tlte l ta/1m1 Navy tu develop mu! 111m111facture SADOC. a shipborne data process1118 syste111 for ai r \Varuing ruul conunaud of navnl 1act1cal oper atio11s.

Elabora1io11 Syste111 ) 1vllicl1 enlta11ces the contra o nava operations 011 i1oard \Varsllips

~~~ INDUSTRIE ELETIRONICHE ASSOCIATE S.p.A.

~

ROME CITALYl

17

"Airborne TV tested as ATC Aid" by Max Karant

This article was first published in the February 1966 issue of "The AOPA Pilot" and is reprinted with kind permission of its Editor, Mr. Max Karant. Mr. Karant recently participated in an evalution of airborne television as a control­navigation aid. His conclusion: Leave traffic controlling to the professional controllers.

Can a TV-relayed FAA radar screen, displayed in a plane's cockpit, be of any appreciable help to the pilot?

There are at least two schools of thought on the sub­ject. One believes it can, and was responsible for a month­long test of such TV transmissions in the Boston, Mass., area. The other doesn't think so, and would rather leave the necessary control of traffic (which is what these radars are used for) to professional controllers.

I am a member of this second school, because I re­cently participated in the experiment with my TV-equip­ped Twin Comanche. And I might be expected to be fairly objective about the test, because I already have the TV and think I would welcome the opportunity to use such an aid - if it really was an aid.

Accompanied by a representative of the Air Transport Association, I flew all around the Boston area for 0121 on November 6, tuned to Channel 2 (WGBH-TV), an edu­cational TV station there that participated in the month­long experiment with the FAA. Much of the time the pic­ture was unstable and substandard; I checked the air­borne installation on six other channels in the area to make sure it was not a defect in the plane installation. Another plane in the air, also participating in the test that day, suggested the poor picture might be due in some measure to interference from WCBS-TV, the New York station on Channel 2.

The picture was good at times, particularly directly to the east of the Boston airport, to the north and northwest. But even when it was good, what did I have? The radar screen being transmitted by the TV station was the stan­dard 16-inch airport surveillance radar scope used by the FAA throughout the country. It was received in the plane on a five-inch Sony TV screen.

Yet, it was possible to locate your "pip" on the screen (which covered a radius of 30 miles) if you had the proper help. In my case, I used a VOR receiver and DME to esta­blish my position. Then I looked in that area on the TV screen and, sure enough, there I was.

But if you didn't use VOR and DME to locate your­self that way, you'd have to ask the controller to do it for you. And once he did, you hadn't better lose track of yourself among all the other pips, landmarks, air~ays a~d fixes prominently displayed on the radar. If you did, ~ou d have to ask the controller to locate you all over again -unless you wanted to do some turns yourself, always watching for one of the pips to do what you're doing in the oir. If you had a transponder, of course, it would be eosier

1 because your pip would stand out. And if you

lost yourself temporarily, you could punch the "ident" but-

18

ton and see your transponder bloom on the radar. This could interfere with the work of the controller himself, but you could do it.

See weather in the area? Not on a traffic-control ra­dar. The FAA usually has everything turned on to do everything possible to eliminate weather on their scopes: MTI (moving target indicator), and CP (circular polariza­tion). And in a bad weather situation they certainly won't turn off either of these (which would automatically clob­ber all the scopes in the FAA facility) just so you could see weather on your TV.

The Boston layout was perhaps too good for the test. The Vortac and the radar antenna are virtually in the same spot. So it's easier to first locate yourself on the Vortac, then transfer to the TV, than it is in most other places in the country.

What about locating other traffic on the radar, then flying your pip so as to avoid it? Not hardly. You see pips everywhere on a busy day. They're coming at you from all sides. You sometimes overtake others, and if you concentrate on that TV information for collision avoidan­ce you'll be airsick before you're through. All the pips ap­pear .on the same plane on a radar scope, even though the a1rplanes themselves could be miles above or below each other. Experienced controllers are quite accustomed to sorting out such discrepancies; pilots are not.

Then there's the business of looking out the windows, watching for other planes. To use that TV presentation in my plane to actually position myself, and watch out for what I might thin.k '.s conflicting traffic, my head would have to be down inside the cockpit quite a bit of time. Or you'd need a copilot - someone who could keep an eye on ~he tube, and try to figure out what you should try to avoid, and what you should ignore.

As a.n overall co~ment I would say that, whenever control 1s necessary, leave the controlling to the control­lers". And for the same reason we ourselves so often say to the controllers "leave the piloting of the plane to the pilot". Th.e co~troller on the ground is a skilled professio­~al, working ":'1th the best tools money can buy. His sole job 1s concentrating on that 16-inch scope, in a dark room, with little or no interference. He's had a lot of training in the use of radar. I would much rather have him use his expertise to interpret what he sees, then tell me what he deduces from it all. A five- or seven-inch TV set, being scanned in daylight by an inexperienced pilot, is not by any stretch of the imagination a substitute for any phase of our present traffic control system.

Even the FAA itself, so often accused of looking favo­rably on anything that would build up their traffic-control empire, has been turning down this TV suggestion from many outsiders for years. But the idea just wouldn't die. Latest exponent who kept persisting was Crocker Snow (AOPA 64966), Massachusetts state aviation director, who persisted so tenaciously that D. D. Thomas, FAA Deputy Administrator, finally ordered the Boston test "to find out, once and for all".

Several things have now been "found out". First, the month-long test cost the taxpayers about SB,500 out of pocket; how much more in time and manpower is not

known. Then, quite early in the project, the Federal Com­munications Commission shot down any thought that such a thing could ever be implemented cheaply. The FCC in­formed the FAA that not a single TV channel in the present VHF or UHF bands could be made available for this pur­pose. Therefore, while the network of ground stations could perhaps be standard transmitting stations, they would have to be purchased completely for this purpose, and could not "ride piggyback" on the existing TV station network. And - even more important - the airborne receivers could no longer be the mass-produced small sets like my Sony; they'd have to be costly special units, built just for this purpose.

* * *

Considerable Foreign Participation in 1966 German Aviation Show

Judging from figures available at the beginning of March, about 300 firms from some 13 countries will display their latest products at the 1966 German Aviation Show, which will be held at Hannover Airport from 29 April to 8 May. Of these, more than 170 are manufacturers. There will be 101 West German exhibitors as well as a further

nine indirectly represented. The display area covers more than a million square

feet. Net exhibition area is 120,000 sq. ft. of which nearly 90,000 sq, ft. are hall space.

Close to 100 aircraft will be on display, including 72 fixed-wing aircraft, 15 rotary-wing aircraft and 3 gliders. 33 of the fixed-wing aircraft comprise single- and twin­engine sport, business and executive aircraft as well as 14 executive types with jet or turboprop engines. The group also includes commercial and transport aircraft, utility aircraft, VTOL experimental aircraft as well as a

number of military machines.

Executive aircraft will be particularly well represented at Hannover, and herald the development of a sizeable European market in this mode of travel.

The Show will be officially opened at Hannover Air­port on the afternoon of 28 April. The guests will be ad­dressed by the President of the FRG, Dr. Heinrich Lubke, the Prime Minister of Lower Saxony, Dr. Georg Diederichs, as well as by Prof. Karl Thalau, President of the Federation of the German Aerospace Industry (BOLi). On 29 April the Show will be thrown open to the general public and will close on Sunday, 8. Moy. Opening hours are 9.00 a. m. to 6.00 p. m.

Hannover is on ideal venue for the Germon Aviation Show. Running concurrently with the Hannover Fair, it al­lows visitors to combine a study of the products of the aerospace industry with on examination of the wider field of industrial enterprise represented by the Fair.

BOLi

* * *

6th Annual Conference of the Austrian Air lraffOc Controller' Association

On 19th January 1966, the Austrian Air Traffic Con­troller's Association held its 6th Annual Conference in Vienna. Various technical and operational subjects were at the agenda, centred on the topic "Mon in the Air Traf­

fic Control System".

A great number of representatives from other Control­ler's Guilds and Associations participated in the gather­ing, among them Jakob Wachtel, the Chairman of the l~­rael Association, and Drago Zivkovic of the Yugoslav Air

Traffic Controller's Association.

I FAT CA Vice President Maurice Cerf attended on be­half of the Elective Officers of the Federation and, in his address, conveyed the greetings of President L. N. Tekstra

to the Conference.

The Annual Conference elected the following Boord of Officers: -

President 1. Vice-President 2. Vice-President Secretary Deputy Secretary Treasurer Deputy Treasurer Press Officer

Sub-Committee

Herbert Brandstetter Alfred Nagy Helmut Kihr Rudolf Obermayr Hons Bauer Wolfgang Chrystoph Konrad Hirsch Kurt Told

Chairmen Walter Seidl (Human Factors) (Professiona I Matters) Kurt T ornicek

19

Radio Communication Failure Procedures Reviewed

After the 1963 RAC/OPS Divisional Meeting in Montreal, IFATCA's Standing Committee I hos discussed the present regulations concerning radio failure procedures and the additions to these procedures as proposed by !CAO. The following is a summary of a Working Poper prepared by Standing Committee I, and will be discussed at the forth­coming IFATCA Annual Conference in Rome. It is, there­fore, not yet to be considered as official IFATCA policy. IFATCA Member Associations, having received the origi­nal paper of S. C. 1, will be forwarding their comments through normal IFATCA channels. Any additional comment, be it from individuals or from organisations, would be appreciated and should be addressed to:

Mr. Arnold Field, OBE Chairman, IFATCA S.C. 1

14 South Street Pork Lone London W. 1 England

At the 1963 RAC/OPS Divisional Meeting, ICAO com­munication failure (hereafter abbreviated to "R/F") proce­dures were re-considered, and a number of revisions to existing regulations was proposed.

It was recommended that action should be taken to improve the reliability of airborne radio equipment.

It was recommended that at each international aero­drome one VHF and one LF/MF aid should be speci­

fied for instrument approaches.

It was also recommended that States should publish in their AIP's full details of R/F procedures applicable

to their national airspace.

On the other hand, it was agreed that R/F procedures should be as brief and simple as possible, and that national deviations and supplementary procedures

should be eliminated.

The Air Navigation Commission of ICAO have accepted all these recommendations and will, in due course, im-

plement them.

In its discussions, the RAC/OPS meeting did not con­sider how the increased availability of surveillance radar at terminal airports might be used to simplify R/F proce­dures in order to allow greater freedom of action to all

aircraft concerned.

ATC experience shows that when radio failures occur, pilots do not normally rigidly adhere to published proce­dures. This may be due to difficulties in applying the basic ICAO procedure to the particular circumstances prevail­ing at the time of R/F occurrence, or to the complexity of additional procedures published by States in the attempt to cover every foreseeable circumstance.

It seems appropriate therefore for I FAT CA to take a close look at R/F procedures in the existing air and ground environments with a view to their overall simplification and to the provision of greater freedom of action to pilots.

20

Radio Failure Procedures

ICAO Procedures

The basic R/F procedures to be followed by IFR flights in controlled airspace is detailed in Annex 2, para. 5.3.4.2.

This procedure appears to be deficient in three re­spects,

a) it does not permit an aircraft which is outside control­led airspace under ATC along a Predetermined Route on an IFR flight plan to follow the ICAO basic proce­dure,

b) it gives no alternative procedure for a pilot to follow under IMC if unable or unwilling to continue to desti­nation,

c) it does not specify what other aircraft flying outside controlled airspace should do.

It seems that these deficiencies should be made good by ICAO itself for world-wide application rather than to be supplemented by contracting States by publishing va­rious national procedures.

Regional Procedures

As it is left to individual States to promulgate what supplementary procedures they consider necessary, there are wide variations in the degree of detail they incorpo­rate. Aircraft on international routes have to carry with them considerable documentation concerning the rules over foreign territory, and the ability of pilots to comply precisely with each and all of these requirements is great­ly reduced when a case of radio failure occurs.

ATC Environment

Uninterrupted R/T communication is required between ATC and aircraft in all stages of flight, because this is the only system at present available for issuing instruc­tions and information necessary to guarantee the safe, orderly and expeditious conduct of flight of any one air­craft in relation to other aircraft flying under air traffic control.

Climb and Descent Phase

Speaking of R/F procedures, we are concerned only with those terminal aerodromes at which departing and arriving aircraft fly in controlled airspace after take-off and before landing. Except in predominantly VMC areas of the world, there are now only very few international airports which are not equipped with surveillance radar - and in many cases some form of PAR covering the final approach sector.

As a general rule, these ASR's have a minimum range of 40 nm and a vertical coverage of 10-15 OOO feet. At a number of these fields, radar is used systematically to speed up the rate of departure and arrival of flights and is manned on a continuous basis.

En-Route Phase

Generally speaking, separation between en-route air­craft is effected by procedural (or "conventional") me­thods, i. e. vertical or time separation. Therefore, if a radio failure occurs en route, all that can be done is to safe­guard the level(s) at which the R/F aircraft is assumed to be flying. Only in certain areas where radar is used also during the en-route phase, a greater freedom of action can be given to other en-route aircraft in relation to the R/F aircraft.

Incidence of Radio Failures

The types of radio failure arising from aircraft equip­ment failure may be classified as follows: a) Complete loss of receiver and transmitter. b) Partial loss of R/T contact due to either transmitter or

receiver failure. c) Temporary loss of receiver and/or transmitter (for

example due to changing to the wrong or an unservi­ceable frequency). Practical experience shows that most radio failures are

partial or temporary. Although this type of failure may be embarrassing to ATC, it is rarely necessary for pilots or ATC to follow the full R/F procedure.

A complete radio failure is so rare that many control­lers have never in their career had to deal with one.

ATC Experience in dealing with R/F Aircraft

As said above, ATC experience shows that for one reason or other, R/F aircraft will, in general, not follow precisely the procedures which are laid down basically by ICAO and supplementarily by individual States. Thus - as "conventional" separation cannot safely be based on the assumption that the R/F aircraft will stick to rules - air traffic control officers attempt to protect every possible variation of a R/F aircraft's flight profile.

This unfortunately defeats one of the main objectives of published R/F procedures, namely, to minimise delay and restrictions to other traffic. The controller's philoso­phy, however, must always be "better safe than sorry".

These delays and restrictions do not so much affect en-route aircraft. But at a terminal aerodrome, while a R/F aircraft is believed to be in the vicinity, the safe con­tinuation of landlings and take-offs in IMC can only be achieved by use of radar.

Considerations and Conclusions

Regrettably one cannot say that aircraft no longer ex­perience radio failure, although it is certain that sue~ cases occur less and less frequently. Some form of R/

procedure must therefore be retained. The very fact that R/F procedures permit an airc'.·aft

to continue in controlled airspace necessarily penalises al I other users of this airspace. The only way in whicl~ ATC can achieve any sort of flow of traffic, particul~rly .'" th.e vicinity of the R/F aircraft's aerodrome of destination, is

by a) extensive use of radar, b) use of VMC, or c) taking calculated risks based on the assumption that

the R/F aircraft will strictly adhere to published proce­dures. From the viewpoint of ATC and other airspace users,

R/F aircraft would ideally be allowed only to continue in VMC or leave controlled airspace. From the viewpoint of the pilot of a R/F aircraft, however, he would ideally be allowed to do whatever he thought best for the safety of his (and other) aircraft in the circumstances prevailing.

Any R/F procedure must therefore strike a balance

between these two requirements.

The ICAO Basic Procedure­Suggestions for Improvement

Taking into consideration what has been said above, it is suggested that the IMC procedure would be broken

down into three phases: a) Departure and climb to cruising level. b) En route. c) Descent from cruising level, and landing.

To simplify the procedures in phases (a) and (c), the systematic use of radar at most terminal airfields should be recognised and utilised to give pilots of aircraft more freedom of action than they enjoy now. It will, however, be necessary for States to notify in their AIP's those air­fields at which the radar based procedures for phases (a) and (c) are to be employed. In addition, the requirement for aircraft to "land, if possible, within thirty minutes" should be clarified, as it is not now, for practical pur­poses, worth the paper on which it is written.

It is suggested that the ICAO Basic R/F Procedure might be re-written as follows:

l. If in visual meteorological conditions, the aircraft a) continue to fly in VMC, and b) land at the nearest suitable aerodrome, and c) report its arrival by the most expeditious means

to the appropriate ATC unit.

2. If in instrument meteorological conditions or when weather conditions are such that it does not appear feasible to complete the flight in accordance with 1, the aircraft shall take the following action according to the phase of flight at which the radio failure occurs:

a) Take-off and Climb to Cruising Level (i) If the departing aircraft is operating under a radar departure clearance, the aircraft shall, after reaching the limit of any initial basic zone depar­ture clearance that has been received, either con­tinue to climb on the flight plan route to the cleared cruising level, thereafter continuing as at (b) and (c) below, or level out and return to the departure airfield's designated navigational aid and effect a

landing as under (c) (i) below. (ii) If the aircraft is operating under a non-radar departure clearance, the aircraft shall in all cases continue flight in accordance with the clearance received, thereafter continuing as at (b) cmd (c) below.

b) En route (i) Proceed according to the current flight pion to the specified clearance limit ond, 1f the clearc111ce limit is other than the aerodrome of intended lond-

21

ing, thereafter according to the intentions specified

in the current flight plan. (ii) The last assigned and acknowledged cruising levels shall be maintained to the points specified in the clearance, or to the point at which these le­vels are operationally unacceptable to the aircraft. Thereafter the cruising levels specified in the cur­rent flight plan shall be maintained.

(iii) Arrange the flight so as to arrive over the ap­propriate designated navigational aid serving the aerodrome of intended landing at, or as closely as possible to, the estimated time of arrival specified in the current flight plan.

c) Descent and Landing (i) If the destination is notified as a radar environ­mental airfield, commence descent on arrival over the designated navigational aid serving the air­field. Thereafter effect a landing at destination using any available instrument approach aids or proceed to the alternate airfield specified in the flight plan, or adopt the procedure for other flights.

(ii) If the destination is not notified as a radar en­vironmental airfield, commence descent at, or as closely as possible to, the expected approach time last received and acknowledged or, if no expected approach time has been received and acknowled­ged, at or as closely as possible to the estimated time of arrival specified in the current flight plan. Complete a normal instrument approach procedure as specified for the designated approach aid.

If unable to land within 30 minutes of the estimated time of arrival or the last acknowledged expected approach time (whichever is the later), proceed to alternate airfield, or adopt the procedures for other

flights.

ATC Procedures

From the time at which it is assumed a R/F aircraft commences descent over the designated navigational aid until 40 minutes after that time, ATC at a non-radar en­vironment destination airfield should

a) prohibit all landings and take-offs, except in VMC, and

b) freeze all levels in the holding pattern of the desig­nated navigational aid at and below that at which the R/F aircraft is assumed to arrive.

At published radar environment airfields,. landings ~nd take-offs may be continued and those levels '.n the ~aiding pattern of the designated navigational aid which. are within radar coverage may be allocated to other traffic.

ATC procedures for separation of other traffic from a R/F aircraft in the en-route phase should, so far as prac­ticable, protect both those levels included in the AT~ clearance acknowledged by the aircraft and those detai-

led in the current flight plan.

Recommendations

I FAT CA should invite the appropriate international pi­lot and operator associations to discuss ~he ~allowing o~t­linc proposals, which are intended to s1mpl1fy and ratio­nalise existing ICAO radio failure procedures for both,

aircraft and ATC.

22

1. The scope of the ICAO basic R/F procedure should be extended to include those aircraft flying outside con­trolled airspace which are being provided with advi­sory service.

2. ICAO should specify the R/F procedures for flights comprising a) aircraft flying under IFR within controlled airspace

which are unable or unwilling to adopt the ICAO basic R/F procedure, and

b) aircraft flying under IFR outside controlled airspace which are not being provided with advisory service.

3. The ICAO basic R/F procedure for IFR flights unable to maintain VMC should be rearranged to cover the following three phases of flight: a) Departure and climb to cruising level. b) En route. c) Descent from cruising level, and landing.

4. Where radar is used by ATC on a systematic basis for departure or arrival control, special procedures should be detailed in order to give greater freedom of action to R/F aircraft.

5. Provided the ICAO basic R/F procedure is modified as proposed above, the supplementary procedures pro­mulgated by individual States should do no more than detail the following in respect of each terminal air­field sited within a control zone:

a) Whether or not the special radar environment procedures are to be used by arriving R/F aircraft.

b) For all airports the designated navigational aid to which a R/F aircraft is to proceed before commenc­ing descent.

c) For non-radar environment airports the designa­ted VHF and LF/MF aids to be used for the purpose of executing an instrument approach.

6. ATC R/F procedures promulgated within individual Sta­tes should not be based on the assumed rigid adherence of R/F aircraft to detailed supplementary procedures specified for use within a State's airspace - particu­larly in the descent and landing phase of a R/F air­craft's flight. Maximum use should be made of surveil­lance radar to facilitate the continued safe flow of other air traffic.

*

New Council of the Danish Air Traffic Controller's Association

At the Annual Conference of the Danish Air Traffic Controller's Association, which was held in January 1966, the following members of the Council were elected: -

Chairman Vice Chairman Treasurer Secretary Member of the Board

P. Knudsen A. Frentz P. Breddam P. Fagerlund E.T. Larsen

Mr. P. Knudsen has been appointed IFATCA Director and Mr. Larsen Deputy Director. Messrs. A. Mortensen and Aa. Jaenicke have been appointed advisers to the Danish IFATCA delegation.

The Stockholm Area Control Centre at Arlanda Airport Background Close proximity to several civil and military airports, requiring positive coordinat ion.

General layout The centre comprises twenty control desks, eight of which are used for radar control. To the right in the picture are the ACC and APP posi­tions for civil traffic. The military control, to the left, occupies nine desks, four of which are used for radar control.

Connected to the centre are : Two primary radar stations (Arlanda 1 O cm, and Bromma 23 cm) One secondary radar (in order) One DF station, with eight channels

Processing equipme"nt The Censor, a high speed multi­purpose computer, enables simul­taneous automatic tracking of forty targets and the administration of in­formation from video correlators and for alphanumeric generators.

Presentation equipment The PPl's are of 16 " digital type, where raw, processed and composite pictures, video maps for Arlanda and Bromma radars and sixteen runway extension lines for five airports can be selected. Tabular displays for each radar con­trol position present flight and track data for six aircraft simultaneously, and also distance and bearing for a vector l ine control led by keyboard and rolling bal l. For further information on the most exacting ATC systems, avai lable to­day, apply to the Swedish ID-asso­ciate, Standard Radio & Telefon AB, Barkarby, Sweden, wfio developed, manufactured and put the above in­stallation in operation.

Standard /lac/lo & 'Nie/on Afi

Wind Shear Problems in Terminal Operations by Tirey I{. Vickers Director, Air Traffic Advisory Unit Decca Navigator System, Inc.

Introduction

Long suspected as a contributing factor in a number of runway undershoot and overshoot accidents, the subject of wind shear is receiving increasing attention these days. The concern this time is centered mainly on the possible increase in wind shear hazards which may result from the proposed reduction of landing minima to ICAO Category 2 limits, at certain major airports.

Definition

Wind shear - or more specifically, vertical wind shear - is the change or difference of the horizontal wind, with height. It is sometimes expressed as a vector change. It may also be resolved into its longitudinal and lateral components relative to a specific flight track or runway. Each component of the shear is expressed in terms of knots per 100 feet of height.

Characteristics

Although wind shear may occur at any altitude level, the zone of concern these days is that portion of the atmo­sphere which is most critical to the landing operation -the layer from the ground up to a height of about 300 feet. During the past few years, considerable knowledge has been gained about the characteristics of wind shear in this zone. This has been done by the simultaneous record­ing of wind, temperature, and humidity data at a number of different heights, on tall towers at Upton, Long Island, Washington, D. C., Dallas, Texas, Philadelphia, Pennsyl­vania, and Lopik, Netherlands. In general, good agree­ment has been found between the data collected at the different sites.

The tall-tower data shows that strong wind shears often occur under conditions when the surface wind is

L

very low but a strong temperature inversion is present. Such conditions are most likely to occur under clear skies, during the late evening and early morning hours. The temperature inversion (cool air at the surface, with war­mer air aloft) results in a stable, stratified air mass, with relatively little tendency for mixing or turbulence. The result is a smooth, decoupled, laminar flow, in which the air aloft can be moving at a speed considerably greater, and sometimes in a completely different direction, than the air at the surface.

The stronger the inversion, the greater the wind shear can be, before the smooth, streamlined, laminar flow breaks into turbulence and mixing begins. In extreme cases, the shear can reach 10 knots per 100 feet of height, before appreciable mixing takes place. Once mixing starts, however, the wind shear tends to disappear, as the tur­bulence speeds up the airflow at the lower levels. The tem­perature inversion also tends to disappear as the air from the various temperature layers gets churned up together.

The tall-tower data shows also that a considerable wind shear can develop when the surface wind is over 17 knots and an overcast is present. When an air mass is moving across country, the airflow near the surface is slowed by skin friction and pressure drag. As a result, the greatest amount of shear takes place at the lower levels, with progressively less shear in the levels above. Typical example: if the average shear from the surface up to 300 feet is 5 knots per 100 feet, the average shear from the surface up to 150 feet may be 8 knots per 100 feet.

Effects on Aircraft

Longitudinal (Headwind or Tailwind) Component. Dur­ing steady flight, lift equals weight and drag equals thrust. If the aircraft encounters a sudden change in the longi-

L

INCl?EAS/N6 HEADWIND

IN STFADY FL/6HT, LIFT = W£/GJ.IT, DRAG= THRUST.

v~,

OR DECREAS/(VG TAILWINO INCREASES AIRSPEED, WlllCH JNCREAS'ES LIFT AND DRAG.

UNB!lLIJNCED FORCES PRODUCE" ACCELERATION 'A": AIRCRAFT TENDS TO RISE AND 4/RSPUO TCNPS TO OcCREl/SF GRAOUAll Y UNTIL FORCES A Rt AGAIN IN £QIJIL18RJUN1.

w Figure 1 Effects of airspeed changes caused by wind shear

24

DECR£A~IN6 H£AOW/ND OR

INCREAS/Na TAILWINO DECREASES AIRSPEED, Wl.//CH DECREASES LIFT AND {)RAG.

UNBALANctD FORCES PROl)l)CE ACC£LcRATION ':4 .. : AIRCRAFT TENDS TO SINK AND AIRSPEED TENDS TO INCREASF 6RAOUAlL 'f' UNTIL FORCE .S A Re t46AIN IN fQVIL.IBRllJM,

L

w

A

Figure 2 Increasing headwind component

tudinal wind component, the inertia of the aircraft pre­vents it from reverting instantly to a new groundspeed. Instead, the immediate effect on the aircraft is a sudden change in airspeed. This changes the lift and drag forces, as shown in Fig. 2. The airplane then accelerates in the direction of the stronger forces, until equilibrium is achiev­ed with lift again equal to weight and drag again equal to thrust, at the new groundspeed. Some typical examples are described in the following paragraphs.

Figure 2 shows the effect of an increasing headwind component on the final approach path. This type of wind shear can occur at the base of a low overcast. The imme­diate effect is an increased airspeed. The resultirg in­crease in lift tends to raise the aircraft above the intended path, thus increasing the possibility of an overshoot. If the runway is short, the pilot's only method of completing the landing is to duck below the normal glide slope and force the aircraft on to the runway.

The same effect shown in Figure 2 can occur if the air­craft encounters a decreasing tailwind component on the final approach path. This condition can occur during a temperature inversion, when the surface wind is almost calm. Here again the immediate effect of the shear is an increased airsf!>eed, with the increased lift raising the air­craft above the intended path, increasing the possibility of an overshoot. This particular condition has been re­sponsible for many go-arounds (missed VFR approaches) on calm evenings, at airports with short runways.

Figure 3 shows the effect of a decreasing headwind component on the final approach path. The immediate

Figure 3 Decreasing headwind component

I '~

i:

/ /

I

'·

WIND PROFILE'

effect is a decrease in airspeed. With the resulting de­crease in lift, the aircraft tends to sink below the intended path. If the wind profile is as shown in Figure 3, the air­craft is sinking into an area where the airspeed is even lower, thus further accentuating the problem. Unless ad­equate corrective action is taken to increase the airspeed and reduce the sink rate, the result can be a hard landing, an undershoot, or even (in extreme cases) a complete stall. The pilot who anticipates such a shear condition can re­duce the hazards listed above, by using an approach speed somewhat higher than normal, to allow an ad­equate margin for the airspeed losses which will occur.

Figure 4 illustrates the case of an underpowered or heavily loaded aircraft climbing into an area with a de­creasing headwind or an increasing tailwind. The imme­diate effect is a decreasing airspeed, which reduces the lift and causes the aircraft to sink below its initial climb path. The problem now is to accelerate the aircraft again to a safe or optimum climb speed. However, if no reserve engine power is available, the pilot's only solution is to make a further sacrifice in climb gradient, levelling off to pick up speed and then climbing out at a somewhat higher airspeed and lower gradient than was used initally. The main hazard in this situation is the possibility that the total loss in climb gradient may exceed the safety margin initi­ally allowed for clearing obstacles on the climbout path.

One other operational problem should be mentioned in connection with the longitudinal component of wind shear. This is the ATC problem of spacing aircraft on the frnal approach path in order to maintain a maximum land­ing rate, but without violating the existing separation

I <l'

\ ';.....c::i;-------

I \-cl'-------

~- ---~-j ~-------j

WIND PROFIL£"

25

tNCR£AnN6 TAILWIND

'111'/

I ,,,..;

I >-I

I---~: -------------~ I ,....,

I I~

I 1--<

Figure 4 Climb with increasing tailwind or decreasing headwind component

standard. As shown in Figure 5, wind shear adds another variable to the function of determining how much separa­tion to allow between successive aircraft at the start of the common path. As the exact point at which each air­craft may encounter the shear line cannot always be pre­dicted some additional separation should be allowed initial!~ in order to insure adequate spacing throughout

the common path.

Lateral (Crosswind) Component. One of the most dis­turbing factors in the problem of completing approaches in extremely low ceiling/visibility conditions is a changing crosswind on the final approach path. As shown in Figure 6 a lateral shear requires the aircraft to change heading, in order to stay on the centerline of the approach course. In visual flight, the pilot can quickly detect and compen­sate for displacements caused by changes in the cross­wind component. When flying on instruments, however, greater displacement may occur before detection, requir­ing larger corrections and more time to get back on

course.

A typical low-ceiling situation involves a shallow layer of cold air on the surface, being overrun by a warm moist air mass with a different wind direction and velocity. The greater the direction and velocity differences between the two layers, the greater the horizontal accelerations which will be experienced by the aircraft when it crosses the shear line at the bottom of the overcast. The lower the ceiling, the later in the approach the shear is encou~tered - and the less time is available in which to correct the

approach path.

Time becomes the critical factor here because of the inevitable time lags in pilot and aircraft response. When the pilot emerges from the overcast he must see where he is, decide what to do, and actuat~ the controls accord­ingly. Under ideal conditions, this see/think/act cycle re-

WINO

SWFllR I

~I~

TIM£:~

t.,

WIND --- SWtflR

Figure 5 Space-time plot showing eff t f · · · d) f1

1 ec o wind shear (increasing head·

win on ma approach spacing

RUNWAY TRANSITION

~ THROUCiH I St4EAR ZON/:

WfND IN UPPER ltlYER /////

WINO IN LOWER LAYER Figure 6 Heading change required lo compensate for lateral component of wind shear

26

quires about 11/i seconds. At a typical ground speed of 130 knots, the aircraft travels 330 feet (100 meters) during this period. But the situation still isn't necessarily squared away, as the aircraft will require additional time to re­spond to the controls and to fly through the desired maneuver.

Figure 7 shows how much time is required to complete a runway-alignment-correction maneuver, from various offside distances. This data was obtained in flight tests by the Royal Aircraft Establishment several years ago, using a number of widely-different types of transport aircraft flown by groups of civil and military pilots. Surprisingly, the time required to correct a given displacement was nearly the same for all the types of aircraft tested, and for the two groups of pilots.

18

16

w-+---+-•

LEGEND W- WINGS LEVEL AT THIS POINT

j _J

0 06---,-0Lo ___ 2_lo_o __ 3=-o~o=----=4~0;-;:;o;-- 500

D - INITIAL DISPLACEMENT, IN FEE r Fig. 7 Correction time required for runway-alignment-correction

manoeuver

Automation

h f h operations There are those who say t at or approac · · (1 OD-foot down to the proposed ICAO Category 2 minima

ceiling, 1300-foot RVR) a human pilot should not be. ex-. n· ht th corrections pected to provide the last-moment 1g pa f

which have heretofore been such an important part 0

every instrument approach procedure; instead, th.ey say, this function should be turned over to the automatic land­ing system. This philosophy would imply that the automa-

t. f r any last-tic pilot should be capable of compensa 1ng 0 .

moment wind shear which can occur. Some previous designs of automatic landing systems have not been able

d·r Further to cope adequately with extreme shear con 1 ions. study is being given to this problem.

Suggestions

It is believed that the reporting of wind shear informa­tion to pilots would be useful in reducing some of the operational problems, as the pilot would then be better prepared for the situation ahead.

In the past, abnormally strong wind shear has some­times been suggested as a possible factor in specific land­ing accidents. So far as we know, however, wind shear has never been cited officially as a contributing cause of an accident. Perhaps the most important reason why the blame was usually placed elsewhere was that no official data was available to prove that the shear condition was present at the time.

This data gap need not continue, however. Airport con­trol towers at some major airports presently extend up into the 150-to-200-foot zone. At such locations it should be a simple matter to install an anemometer on a roof mast, to provide upper-level wind data for comparison with the surface wind. For airports which do not have a structure extending into the desired height zone, it might be pos­sible to install anemometers at appropriate heights on an existing radio or television tower within a few miles of the airport.

Except during local thunderstorms or frontal passages, such an arrangement probably could provide sufficiently representt.:tive data for determining the wind shear con­ditions which would affect airport operations in the termi­nal area.

Bibliography

For those readers who are interested in digging deeper into the details of this fascinating subject, we would re­commend the reports listed below.

1. I. A. Singer, G. S. Raynor, "Analysis of Meteorological Tower Data April 1950 - March 1952 Brookhaven Na­tional Laboratory", ASTIA No. AD 133806, June 1957.

2. D. L. Markusen, "lnvestig11tion of Wind Shear at Low Altitudes", RTCA 31-63/DO 118, March 1963.

3. C. F. Roberts, "A Preliminary Analysis of Some Obser­vations of Wind Shear in the Lowest 100 Feet of the Atmosphere, for Application to the Problem of the Control of Aircraft on Approach", U.S. Dept. of Com­merce, Weather Bureau, Sept. 1964.

4. Capt. C. M. Ramsey, "Vertical Wind Shear", Memo­randum No. 10, ICAO All-Weather Operations Panel, June 1964.

5. R. C. Gerber, "Status Report, ALPA All-Weather Flying Committee", Air Line Pilots Association, Chicago, Oc­tober, 1964.

6. "Pilot Reports of Wind Shear experienced on Take-off or Landing", U. K. Ministry of Aviation, Civil Aviation Information Circular 84/1965, August 1965.

7. D. H. Rieger, "Some Airline Schedule Reliability Pro­blems", Air Line Pilot's Association, Washington D. C., October 1965.

8. G. B. Litchford, "The l DO-Foot Barrier", Astronautics and Aeronautics Magazine, July 1964.

9. E. S. Calvert & J. W. Sparke, "The Effect on Weather Minima of Approach Speed, Cockpit Cut-Off Angle and Type of Approach Coupler for a Given Landing Success Rate and Level of Safety", Aeronautical Re­search Council Current Papers, CP No. 378, 1958.

27

Separation Minima Reviewed

The following article is the CONTROLLER's synopsis of o working paper produced by IFATCA's Standing Com­mittee I. It should be noted that the views expressed in this study are not yet official IFATCA policy but are in­tended to serve as a basis for the discussions at the 1966 IFATCA Annual Conference. IFATCA Member Associations, having received the original paper of S. C. l, will be for­warding their comments through the normal IFATCA chan­nels. Any additional comment, be it from individuals or organisations, would be appreciated and should be ad­dressed to:

Mr. Arnold Field, OBE Chairman, IFATCA S. C. l 14 South Street Park Lane London W. l England

Separation minima and their application are, natural­ly enough, subjects close to the hearts of all air traffic control officers. On the 1963 RAC/OPS Divisional Meeting in Montreal, the existing horizontal separation minima were reviewed and revised by ICAO, and a world-wide adoption of certain new criteria and procedures was re­commended. The following is a summary of those recom­mendations made, which may be of particular interest to IFATCA. Attention is drawn to the fact that present sepa­ration minima and horizontal separation procedures have only been approved by the Air Navigation Council; they have not the character of ICAO Stand a r d s, and they are only re co m me n de d to contracting States for worldwide application. The same will be the case with the newly proposed minima after their incorporation into DOC 4444 (PANS/RAC).

ICAO's Proposed Amendments to Separation Minima

Horizontal Separation - Modification of Minima by Individual States

An additional note was proposed for the preamble in DOC 4444 to the effect that contracting States may indivi­dually specify either - other minima for use in circumstances not prescribed,

or

- additional conditions to those prescribed for the use of a given minimum, provided that the required level of safety is at all times assured.

Lateral Separation

New minima were proposed for track separation based on the use of VOR's, NDB's and Dead Reckoning, namely separation to be effected

28

"by requiring aircraft to fly on specified tracks which are separated by a minimum appropriate to the navi­gation aid or method employed, as follows: a) VOR: At least 15- and at a distance of 15 miles or

more from the facility. b) NDB: At least 30° and at a distance of 15 miles or

more from the facility. c) DR: Tracks diverging by at least 45° and at a

distance of 15 miles or more from point of intersection of the tracks.

When aircraft are operating on tracks which are sepa-

rated by considerably more than the fo . . . fl regomg mini-

mum igures, S~ate~ may reduce the distance at which lateral separation is achieved."

An additional paragraph was propo d· "Wh se .

en two aircraft are on con . k . h Id b

. verging trac s action s ou e taken m sufficient time to th' .

I I · . ensure at vert1-ca or ong1tudrnal separation exists befo th d

· f re e secon aircra. t passes the point on its route at which the a -propnate lateral separation minima wo Id b . f .P g d Sh Id d b . u e rn rm-

e · ou ou t exist that an a· ft . · d I ircra can reach its

ass1.gne evel before lateral separation i I h . lot-in-command should be req . d s ost, t e p1-

u1re to confi h. b. lity to meet the terms of the clearance." irm is a i-

Longitudinal Separatio 8 d . n ase on Time

For aircraft on the same track t th recommended that the e · t·

2° . e same level, ICAO

xis rng minutes · b tween aircraft departing from th . separation e-flrst aircraft is 40 kts

0 e same airfield where the

should be abolished A 3r m.ore fast~r. than the second · minutes minim · d

instead for application under th um . 1 ~ propose existing 5 minutes minimum whene t~amfle con.d1tions as the ned is 40 kts or more fast e irst aircraft concer-

er. For climbing and descendin t ff

it was recommended that the gf:i~ 1 ~ on cros~ing t~a.cks, be introduced: owing special minima

15 minutes at the time level . s ore crossed 0 t ·f circumstances require, or , r grea er 1

10 minutes if navigational .d . mination of position and s~~e~.permit frequent deter-

Longitudinal Separat· on Distance ion Based

Another recommendation f th . ma should be specified fo or lcdom~ng was that mini-

r wor -wide 0 1· · enable longitudinal separation to be . PP 1cat1on to between any two aircraft by . drastically reduced

d. comparing the · It DME rea rngs reported to ATC b . s.1mu aneous mand. The actual minima put f Yd their pdots-in-com-

"Separation shall be estab~;~e~ b were .as f.ol.lows: less than a specified distan ( ) b Y maintaining not · ce s etween · f · t1ons as reported by refere . a1rcra t pos1-. nee to DME . .

with other appropriate no . t• in con1unct1on v1ga 1onal .d o·

troller-pilot ~ommunications shall be ai .s. .1rect c~n-such separation is used. maintained whrle

Aircraft at the same cruising level . . on the same track

(1) 20 miles or greater wh . 'd d en c1rcumstanc . prov1 e , each aircraft ut·r· ,,

0 es require,

. I ises n T k" DM t1ons and separation is checked b ra~ . E sta-neous DME readings from th . Y obtaining simulta­tervals to ensure that the . ~ aircr?ft at frequent in-.. . minimum is not infrin ed

(11) 10 miles, provided the 1 d' g · a true air speed of 20 k tea ing aircraft maintains

no s or more f t h succeeding aircraft; each aircraft tT as er t an the DME stations; and separation . h u

1kises "On Track"

simultaneous readings from this c. ec efd by obtaining I e a1rcra t at such · t

va. s as necessary to ensure that the in er-bi h d minimum is esta-

1s e and will not be infringed.

Aircraft at the same level on crossing tracks

The separation prescibed under (i) above shall apply provided that each aircraft reports distance from the station located at the crossing point of the tracks.

Aircraft climbing or descending on the same track

10 miles at the time levels are crossed, or greater if circumstances require, provided, each aircraft utilises "On Track" DME stations; one aircraft maintains a level while vertical separation does not exist; and se­paration is established by obtaining simultaneous DME readings from the aircraft.

Aircraft on reciprocal tracks

Aircraft utilising DME may be cleared to climb or to descend to or through the levels occupied of other air­craft utilising DME, provided that it has been positi­vely determined that the aircraft involved have passed

each other."

The Meaning of "Same Track" and "Reciprocal Track"

It was further recommended that States should be al­lowed to construe as "same track" or "reciprocal track" those tracks which converge or diverge within such angle or tolerance as individual States may specify.

IFATCA Standing Committee I -

Considerations and Conclusions

The Status of ICAO Separation Minima

The ICAO separation minima ("Separation Standards" as they are usually referred to in the world of ATC) are specified in the "Procedures for the Air Navigation Ser­vices - Rules of the Air and Air Traffic Control" (PANS/ RAC - ICAO DOC 4444). The whole concept of air traffic control demands that these minima be applied uniformly throughout the world. It is therefore surprising to find that, although most have been established vi~tually un­changed for years, they are still incorporated in a docu­ment detailing procedures which are recommended by the Air Navigation Commission for use by member

'f dif­States. It is not even mandatory for States to noti Y ferences, though the ANC says that this is desirable -

and invites States to do so.

In the preamble to PANS/RAC it is stated that the do­cument is intended to contain the complete procedures applicable to the Air Traffic Services and that it "contains material which is to a large extent fluid and liable to rela­tively frequent change". Because of slightly more com~l~x procedures involved in the amendment of Annexes it 1.s stated that "fluid" ATC procedures are ipso facto unsui­

table for inclusion therein.

"fl 'd" Separation minima are, however, anything but ui and, in the interests of the Air Traffic Services an? of the Airline Operators it is surely time that they be given the status of St a n d ~ r d s. Only the recommended methods of application are really appropriate to PANS/RAC.

The requirement to upgrade the status of separation minima has become more important now that ICAO have

actually invited States to prescibe their own minima and conditions of application whenever they consider this to be necessary. The fact remains that minima used on inter­national routes by adjacent States must be completely compatible and that, therefore, all differences from, or additions to, ICAO minima should be notified. Lowering of minima could be dangerous, whilst raising of minima, or the imposition of additional conditions, could result in unnecessary penalisation of aircraft operators.

Lateral Separation -Track Separation

The long overdue introduction of new criteria for the application of track separation is welcomed. However, it will be noted with surprise that whilst the DR minimum is expressly stated to be for application only to d iv erg -i n g tracks, the minima proposed for use with NDB's and VOR's are apparently intended for both d iv erg i n g a n d c o n v e r g i n g tracks.

In applying the minima to aircraft converging on an NOB or VOR it is difficult to see how the 15 mile distance criterion can safely be applied except when the Air Traf­fic Services have radar available - or when the pilot is able to use a co-located DME facility. Obviously in the former case radar separation would be used in preference to track separation anyway. For all practical purposes this means that track separation between aircraft con­verging on a NOB or VOR facility should only be applied when accurate information is available to ATC on the distance of the aircraft from the facility in question.

In the case of diverging tracks, the same distance cri­terion (namely 15 miles) is to be applied in all three cases, though the track angle difference minima are greater for the DR case than for either NOB or VOR. Regardless of the track angle difference it seems remarkable that the same 15 miles are to be applied between aircraft setting course from the same point-source aid (NDB/VOR) and between aircraft leaving a common DR position, which must, of neccessity, be considerably less definite.

It must again be noted with some surprise that ICAO offer no guidance to States for the establishment of di­stance criteria for such cases where tracks diverge by more than the specified 15 (or 30) degrees, but the distan­ce of aircraft involved is less than 15 miles from the fa­cility. Taking a track divergence of 90° there must still be a prescribed absolute minimum safe distance from the navigational aid for aircraft to use the same level, even when they are setting course from a VOR.

Longitudinal Separation Based on Time­Aircraft on the Same Track at the Same Level

The introduction of a general 3 minutes minimum for the separation of two aircraft the first of which is by 40 or more knots faster than the second will assist ATC con­siderably. However it seems a pity that the 2 minutes se­paration minimum for aircraft departing from the same airfield at the same level should be incr-eased to 3 minutes. No evidence is known that this standard was in any way unsafe. In fact, it must be safer than the 3 minutes separa­tion between en-route aircraft which can only be based on the relatively uncertain reports over a common navi­gational fix.

29

Longitudinal Separation Based on

Distance

1) General Appreciation

It is good to see that, at last, a (presumably) safe method has been found for reducing the longitudinal spacing of aircraft in those areas where radar coverage is not provided. The full procedures, however, are based on the proposition that an extensive chain of DME sta­tions is available along air routes. Such a ground environ­ment is, in fact, only to be found at this time in very few parts of the world. The procedures for use of DME are therefore only capable of implementation on a very li­

mited scale. The same was the case when SSR procedures were de­

veloped by ICAO. ICAO therefore wisely decided that, until such time as more experience was gained throughout the world in the use of SSR, it would be more appropriate to include SSR procedures in "Regional Supplementary Procedures" (DOC 7030).

Why then have they not come to the same decision with regard to DME procedures and the establishment of minima longitudinal separation based on distance?

Up to now, operational experience of the application of DME separation between aircraft appears to be con­fined to only one or two ICAO member States - one of which is outside the ICAO regional organisation. The S. C.1 is therefore not in a position to offer advice based on practical experience of DME procedures. We are, for this very reason, anxious that States should make certain that the ICAO proposals are safe, before full implementation is effected. To this end, the maximum use should be made of radar-monitoring facilities during initial trials.

The requirement for transmission to ATC of frequent simultaneous DME readings from aircraft is stressed by ICAO. IFATCA may also wish to ensure that the proce­dures will not result in a significant increase in R/T chan-

nel loading.

Whether the wording of the proposed procedures is unintentionally vague or not, it is surprising to see that, when separation between aircraft is based on DME read­ings, it is not specifically stated that the same DME fa­cility is to be used by all aircraft concerned.

2) Aircraft at the Same Cruising Level on the Same Track

This particular procedure seems to be least practi­cal for implementation on a world-wide basis, as it re­quires that DME stations should be available for the who­le of an aircraft's flight at cruising level. As DME and time separation standards are fundamentally incompatible, it would be impracticable for ATC to try and switch from one minimum to the other while aircraft are en route at

the same level.

The only practical application of the minima (except domestically in a full DME environment) appears to be during the departure phase of a flight, when reduced se­paration is applied to the exit fix of a TMA. There are few TMA's however, where - in case such reduced sepa­ration is operationally necessary - the required results cannot safely and efficiently be achieved by the use of radar.

3) Aircraft at the Same Cruising Level on Crossing Tracks

These minima should be of assistance to the Air Traf-

30

fie Services in those areas where radar coverage is not provided.

4) Aircraft Climbing and Descending on the Same Track

In this particular application, DME appears to offer most practical advantage to controllers and pilots. It will enable level changes to be made more readily outside radar coverage or before establishment of radar identifi­cation. The additional RIT time involved in applying this procedure should not be significant.

5) Aircraft on Reciprocal Tracks

The present wording of this paragraph requires edito­r'.a_I polishing i~ as 1~0~ as the meaning of the phrase "po­s1t1vely . determin.ed 1s concerned. This must mean "by comparison of simultaneous readings from aircraft using the same DME facility".

6) Additional Use of DME

We should have expected more guidance from ICAO on metho~s. of utilising DME information for ATC pur­poses add'.t1onal to the comparison of readings from two or more .aircraft. Two further theoretical applications co­me to mind:

- radar i~entifi_cati~n: It seems reasonable to suppose that radar 1dent1ficat1on could be established directly by relating the position of a radar echo to the VOR rad· I

b . f 1a

(or eanng rom an NDB) and DME reading reported b an aircraft, provided the VOR/NDB and DME station~ were co-located.

- Track separation minima: Where 0 VOR or NOB is co-located with a DME facility, the proposed ICAO t k . . . roe separation minima c?uld be applied not only to diverging but also to converging tracks, provided DME distance is reported to be greater than 15 miles.

Longitudinal Separation Based Ti'me A

. f on 1rcra ton Reciprocal Tracks

Although this particular subject was not discussed at the ~AC/OPS m7eting, it is desirable that IFATCA should co.ns1der how this separation standard could be reduced. It 1s, above all other minima, very restrictive for ATC a Ii-cation. PP

As ~ill be known, the present minimum requires vertical separation to be established between 01'rcraft · . on recipro-cal tracks 10 minutes before they are estimated t I h

f . h. o cross. n t e case o 1ets, t 1s may mean a geograph· I d. t

of about 150 miles. ica is once

It would greatly assist the Air Traffic Ser · th h . vices roug -out the world, 1f an addendum would be mad th f I . . e on e o -lowing lines:

"T.he time by which vertical separation must be esta-blished before two aircraft are crossi'ng b . . may e re-duced 1f th~ following conditions are fulfilled: a) Two radio navigation fixes at least 30 ·1 . , m1 es apart,

lie between the two aircraft, and

b) vertical separation is established before either air­craft passes one of these radio-navigational fixes."

The Meaning of "Same Track" and "Reciprocal Track"

ICAO have acknowledged that, for practical purpos · f b d es,

a1rcra t may e consi ered to be on the "same track" or

"reciprocal track" even if their tracks diverge or converge slightly.

The critical angular difference between tracks must, quite obviously, be the same in all parts of the world. It is therefore surprising that ICAO should leave individual States to decide what the angular tolerance should be. IFATCA will wish that ICAO should itself determine the criterion for angular track differences, taking into account aircraft and radio aid performance data in differing cir­cumstances.

IFATCA Standing Committee I - Recommendations for Adoptions as Official IFATCA Policy

1) The Status of I CAO Separation Minima I

Separation Minima for world-wide application should be incorporated in Annex 11 and given the status of Standards.

Where procdures and associated separation minima are introduced by ICAO and their application is confined to one or two regions (or where their validity has only been proved in limited areas), their publication should initially be restricted to DOC 7030 "Regional Supplemen­tary Procedures".

2) L a t e r a I S e p a r a t i o n - T r a c k S e p a r a t i o n

The application of the track separation minima for NDB's and VOR's should be restricted to aircraft on d i -v e r g i n g tracks, except where the aircraft concerned can utilise a co-located DME facility.

The proposed separation minima for aircraft diverging from a DR position should be reconsidered.

In case of track divergence which is considerably grea­ter than the angles specified in the new track separation minima, ICAO should itself specify an absolute minimum distance for NOB, VOR and DR fixes.

3) L o n g i t u d i n a I S e p a r a t i o n B a s e d o n T i m e Aircraft on the Same Track at the Same Leve I

The 2 minute separation between aircraft departing from the same airfield for the same cruising level (with the first aircraft being 40 kts or more faster) should be upheld - i n add it ion to the proposed en-route 3 mi­nutes minimum.

4) L o n g i t u d i n a I S e p a r a t i o n B a s e d o n Distance

a) General

To facilitate their application by ATC, it should be clearly stated that all separation minima are based on the comparison of DME readings from aircraft using the

same DME facility.

The use of this type of separation must not be allowed to result in R/T channel overloading.

Before introducing the proposed DME separation pro­cedures, radar monitored trials should be carried out to confirm that the procedures are in fact safe.

At present, it would be preferable that these proce­dures would be included in DOC 7030 rather than in DOC 4444.

b) Aircraft at the Same Cruising Level on the Same Track

This type of separation by DME readings should be restricted to the domestic airspace of any one particular State. Its extention to international routes must be subject to inter-State agreement on Regional level.

The effect of this particular procedures on R/T channel loading should be carefully watched.

c) Aircraft Climbing and Descending on Reciprocal Tracks

The words "by comparison of simultaneous readings from aircraft using the same DME facility" should be added after " ... positively determined".

d) Additional Uses of DME

DOC 4444 should be amended to permit the use of DME readings to assist radar identification and to be employed in the application of track separation minima.

5) L o n g i t u d i n a I S e p a r a t i o n B a s e d o n T i m e - Aircraft on Reciprocal Tracks

DOC 4444 should be amended to permit reduction of the time by which vertical separation must be provided before two aircraft are passing each other, provided that

a) two radio-navigational fixes, at least 30 miles apart, lie between the two aircraft, an d

b) vertical separation is established before either aircraft passes one of these radio-navigational fixes.

6) T h e M e a n i n g o f " S a m e T r a c k " a n d "Reciprocal Track"

ICAO should provide more guidance to States as to how they should determine the maximum permissible an­gular divergence or convergence between the tracks of the aircraft.

* * * New control tower and new runway at Orly Airport

The traffic at the Paris Airports (Orly, le Bourget and the airports of the Paris area) has doubled during the past six years. At Orly airport alone the traffic is expected to reach a number of 10 OOO OOO passengers in 1970. This has lead the Aeroport de Paris authority to build a second East-West runway so that the increasing traffic can be absorbed. This runway is 3 650 metres long and can be utilized by aircraft weighing up to 200 tons.

The old control tower at Orly was located in the center of the runway system, that is at the Eastern edge of the airfield. The construction of the new runway has made it necessary to build a new tower, conveniently located and high enough so as to enable controllers to see the farthest end of the runways. This tower, 52 metres high, is adjacent to the terminal building.

Tower and runway were both inaugurated on March 10, 1966, by Mr. E. Pisani, Ministre de l'Equipement, and Mr. Bettencourt, Secretaire d'Etat aux Transports. The ce­remony was attended by Mr. P. Boursicot, President du Conseil d'Administration de l'Aeroport de Paris, Mr. P. D. Cot, Directeur General de l'Aeroport de Paris, personali­ties of aviation, industry and press. The Officers of the Association Professionnelle de la Circulation Aerienne and the First Vice President of I FAT CA, Mr. Cerf, were also present at the ceremony.

M.

31

Rapid Dissemination of Information on Marginal Weather Conditions at Airports

Current and reliable meteorological information significant

Pilots need the most accurate and realistic weather ob­servations possible, when determining whether the meteo­rological conditions at an airport will permit safe take-off or landing.

The rapid transmission to pilots of current weather re­ports, as prepared by the responsible meteorological office, is one of the responsibilities of aerodrome and approach facilities.

Aerodrome MET reports containing the information essential to pilots consist of a) routine reports, generally made available at half­

hourly intervals; b) reports of special observations relating to deterioria­

tion in weather conditions; c) runway visual range.

From the operational point of view of air traffic control there are three problems associated with the task of making meteorological reports available to pilots:

the rapid and reliable transmission of meteorological observal·ions from the weather station to the air traffic control facility; timely transmission of this information to the pilot, and proper recording and documentation of the data trans­mitted by the weather station and by the ATC facility. The importance of these problems was demonstrated

recently when an air traffic controller at a major airport in Germany was publicly and in an obviously unqualified manner accused by an illustrated paper with nation-wide distribution of having materially contributed to an air­craft accident because he had alledgedly transmitted er­

roneous weather reports to the pilot. The methods used to transmit weather reports from the meteorological offices to ATC facilities vary. At some air­ports, weather observations are relayed by telephone to air traffic control. At other locations, a collective dissemi­nation system is used, where the observations made by the weather bureau are recorded on magnetic discs, and ATC facilities airline offices and others interested may, by dialling a' designated telephone number, monitor the stored information. This system provides for a signalling arrangement to warn air traffic controllers that a new

weather observation has been recorded.

As the pneumatic tube is still with us, it is frequently used to transport meteorological reports from the weather

bureau to ATC facilities.

The transmission of weather reports via AFTN and their reception by teleprinters is also a common practice, although the distance between the weather bureau and the control tower and the approach control office is only a few hundred feet or a compile of floors within the same

building.

In most of the cases mentioned, the meteorological data thus received at ATC facilities needs to be transcri­bed, copied, or put into some other form suitable for

32

display to air traffic controllers, and must then in many instances be distributed to numerous control positions. As a result we may find that important elements of the weather conditions observed at an airport (e. g. runway visual range, rapidly changing cloud ceilings, etc.) often arrive at the air traffic controller's operating position with considerable delay.

Another problem, as mentioned earlier, is the efficient recording of the meteorological information transmitted. Although the weather data transmitted via telephone to ATC facilities are usually recorded on magnetic tapes, !hei_r reproduction, if needed for analysis or as evidence, is time-consuming and cumbersome. Further, there is no eviden~e, that the information transmitted was properly transcribed and copied, unless all copies made are re­tained along with the tape recordings.

T_h~se then are. some significant disadvantages of the trad1t1~n~l transmission techniques. Regarding the timely t~ansm1ss1on of meteorological information to pilots, re­liance must be placed on the judgement of the controller who - apart from complying with established instructions in th_is res~ect - m~st be conscious of his obligation to ~rov1de _airc_rews ~1th whatever current meteorological information is available to him to assist pilots in critical phases of flight, such as approach-to-land and take-off under rapidly changing marginal weather conditions.

In order to enable the controller to do this it would seem that some of the difficulties mentioned ;bove em­phazize the requirement to receive at terminal air traffic control f?cilit!es, without delay, reports of meteorological observations 1~ a_ for'.11 which does not need reproduction and manual d1stribut1on to operating positions within the facility, and which is, without further effort properly re­corded for operational and legal purposes.'

The ZETFAX system

An_ interesting solution to this problem has recently been introduced at some German airports by the Bundes­anstalt fUr Flugsicherung {BFS), the Federal Institute for Air Navigation Services. It makes use of a modernized facsimile technique.

The Dr. Ing. Rudolf Hell Company at Kiel manufacture the ZETFAX_ system [l], which is capable of being adapted to the special needs of air traffic control. It consists of a transm~tt~r un~t, an associated control device for multiple transm1ss1on lines and one control amplifier for multiple outputs, located at the weather observation station close to the instrument runway, and various receiver/read-out units at_ the control tower (fig. I) and in the approach con­trol office. The weather observer records his observations in ATC code on special paper and feeds it into the trans­mitter. The recorded data are instantaneously transmitted via normal telephone lines and appear in the same form in which they were recorded, on strips of paper at the re­ceiver/read-out, ready for use by the controller (fig. 2).

Figure 1 ZETFAX Receiver installed in a control tower

Adequate provisions are made to ensure a high degree of operotional reliability. This includes instantaneous in­

dication of any system malfunction.

The weather reports transmitted via the ZETFAX faci­lities are also recorded in spoken clear text on magnetic tape in order ta transmit this meteorological information by modulating the signals of navigational aids (ILS, VOR), and to effect transmissions on VOLMET frequencies, so that weather reports may be intercepted by aircraft in

flight. Depending on the lay -out of output amplifiers and on

the numbers of transmission lines, many other interested agencies may be connected to this type of weather trans­mission/ reception system. Figure 3 shows a d iagramme of a ZETFAX instal lation al the Frankfurt/Main Airport. As can readily be seen from this illustration various other appl ications of this type of facsimile system are possible. Within ATC it is also used for report ing arrival and de­parture t imes and for relaying flight plans from the AIS briefing unit to the control tower. The German M eteorolo­gical Service at the Frankfurt/ Ma in airport operates spe­cial HELLFAX recorders to record weather forecast charts and specia l wea ther maps received via telephone l ines from the centra l office of the German Meteorologica l Service or by radio from foreign Meteorologica l Offices.

As indicated in figure 3, airlines use facsimi le equip­ment of this type for the reception of meteorological re­ports, as we ll as for the exchange of operational and adminstrative messages between the ir different depart­

ments. A meteorological va lue of particular importance to

pi lots in marginal weather conditions is the runway visual

range (RVR). The RVR system has been evolved to make avail.able a more precise assessment of visual range in relation lo a particular runway in meteorolog ical v is ib i l i­t ies of les~ than 1100 metres. The values measured repre­sent l~e visual range which a p i lot may expect from the cockpit of an aircraft whi le landing or on take-off. Run­way visua l range measurements are usually taken at all airports equipped with prec ision approach systems a nd are transmitted by air traffic controllers to all aircra ft ~bout to land or take-o ff at such airports. At most loca­tions: runway visual range is determined by reference to specia l runway markers or runway l ights at certa in inten­sity settings, or other electric reference l ights. The spacing of these markers or light sources along the runway is kno:--n. The visual range is obtained by counting ma rkers or lights along the runway and application, w here neces­sary, to an appropriate conversion table. The result is then communica ted to ATC.

The system used in the United States At many airports i n the United States, runway visual

range is measured and d isplayed to air traffic controllers direct ly. The US W eather Bureau is current ly making run­way v isual range installations at sites designated by the FAA, with first p r iority being given to 165 runways. The final goal is the installation of runway visua l range systems for a ll h igh intensi ty l ighted runways.

The more advanced RVR system (2] consists of a) a transmissomeler· b) high intensity runV:,oy l ights ; c) a computer; d) digital read-out diplays.

~A!N /OOO /~

' I I I

I

Figure 2 An a irport weather observation in ATC code as received a t an a i r tra ff ic control opera t ing position via ZETFAX

33

CD

US Air Force

CD

Approach Control

-- -- --CD

Tower

Flight Plans Departure Messages

Arrival Messages

Aeronautical Information Service

0

c~ ~CA

Met Observation

Reports

CD

~ German

CD Weather

@ 0 Service

City Branch Management Fhght Control

Operations

Customs Clear Freight. Mail

Interline Counter Food Storage Load Control

CD PAA

~ AIS TRAFCO

~DLH F~~~OPCO

R

CD

Figure 3 Schematic diagramme of ZETFAX installations at the Frankfurt/Main airport Met Observation Station

Legend: R = Receiver, T = Transmitter, CD = Control Device, CA = Control Amplifier

The primary instrument used to determine RVR is the transmissometer. This instrument consists of a projector, a detector and a meter or recorder to indicate the light

transmissi~ity of the atmosphere. The projector emits a light of known intensity; the detector measures the amount that is received as a percentage of the amount that would be received through clear atmosphere, and the meter converts this into a measure of visibility. In effect, the transmissometer samples the visibility along a known baseline and determines the visibility over a greater di-

stance. The transmissometer is usually placed near the ap-

proach end of the I LS runway and positioned so that the light beam is parallel to the runway. The projector and detector are installed with a Axed baseline between them of 500 to 750 feet. The function of the projector is to direct a steady light beam of constant intensity toward a photo­electric detector at a known distance. This detector is sen-

34

sitive to the varying intensity of the projected light beam. The intensity of the light received at the detector depends upon the degree to which the path between the projector and the detector is obstructed by rain, snow, drizzle, fog, haze, etc. The detector generates a series of impulses into a recorder - indicator or computer. These pulses are in proportion to the light intensity received by the detector. Representative light intensity - i. e. that light intensity which is available to the pilot when he views the runway lights from any reasonable angle - is used in the RVR system. The three highest light settings of 5 settings of runway light brightness are used in determining runway visual range.

The computer in the system digests runway light sett­ing information, varying transmission values, and the exi­stence of a day or night condition. On the basis of this information it computes RVR for any one of the three highest light settings used.

The recorder - indicator of the computer tra.nslates this information into the direct reading indicators. The calibrated meter system converts the transmissometer reading into values of RVR in hundreds of feet.

Digital read-out displays, suitably installed at control­lers' operation positions, e. g. at local and ground con­trollers' approach and PAR controllers' positions, enable controllers to take direct runway visual range readings and to transmit these to the pilot. Figure 4 illustrates this system in schemative form.

New RVR measuring system at Brussels airport

Another runway visual range measuring system which makes use of the closed circuit television technique is being tested at Brussels airport. The system is being de­veloped by Ateliers de Constructions Electriques de Char­leroi (ACEC). In the Brussels installation, a TV camera equipped with a remote controlled zoom lense with the focal length ranging from 50 to 500 millimeters is trained on a row of standard 200-watt marker lights, offset 75 metres from the edge of the runway. The lights are 50 metres apart over the first 500 metres, then at l 00 metres intervals out to 1200 metres. However, only three visibility reading lights are powered at the same time. Control circuits which switch the markers lights on and off, are closed by contacts on the focussing-ring cam of the zoom lens, together with a tilting mechanism, insure that the camera is focussed on the three lights which are lit. To take a remote reading, the observer works with a control panel and the TV receiver. He steps out the system, one light at a time, as long as three lights are clearly

0 0 0 0 0 0

INSTRUMENT APPROACH RUNWAY

0 0 0 0 0 0 0

INST. RUNWAY

0

visible on the screen. The lights are illuminated in a sequence of three - first, second and third; then second, third and fourth; then third, fourth and fifth; and so on. When the visibility limit is reached, the closest of the three lights will show brightly, the middle one will be barely perceptible and the farthest will not be visible. Vi­sibility - the distance to the centre light - can be read directly off thee ontrol panel, which indicates which three lights are lighted. A change in visibility shows on the screen as a light becoming visible or fading out. [3]

It seems that meteorological personnel will operate the system and take remote readings of the prevailing vi­sibility. This leaves the problem of making the results known to air traffic control in a rapid and accurate man­ner unsolved. However, the improvements of the proto­type system, planned by ACEC may well take account of this problem. It is apparently envisaged to eliminate the receiver screen. The system would step automatically until the amplitude of the signal from the closest of the lighted lamps equalled the sum of the other two. At this point, stepping would stop and a visibility value would be displayed on a digital read-out. If this could be achieved, the remoting of the read-out into air traffic control faci­lities (tower, approach control) for direct display to con­trollers would seem to be practical and useful proposition.

GR

References:

[l] ZETFAX aus der Praxis - fiir die Praxis, Dr. Ing. Rudolf Hell, Kiel [2] Runway Visual Range, lst Edition, 2nd Printing, Air Traffic Train­

ing Division, Federal Aviation Agency Academy, May 1964 [3] Electronics, 1966, Vol. 39, No. 4 pg. 237

~~R~~O~ET~ LIGHT BEAM{14 FT ABOVE FIELD LEVEL) • • PROJECTOR O O O O DETECTOR

0 0 0

HIGH I NTENSITvL-----~~----,

LIGH T SETTINGS

.:.r.::. ~

pH OTO CELL

DAY/NIGHT INDICATION

RrNtOM 2 6

COMPUTER

~ rnJ

Figure 4 Block diagramrne of !he RVR system currently undergoing installation at nirports in the United States

35

BOOK REVIEW

Fachworterbuch der Elektrotechnik (Dictionary of Electrical Engineering)

In six languages: English/American, French, Italian, Spanish, Dutch, Germon. Compiled and edited by W. E. Clason; 730 pages, clothbinding, 7100 basic words in the main reference

section. Published jointly by R. Oldenbourg Verlag, Munchen -Wien; American Elsevier Publishing Company, Inc., New York; Elsevier Publishing Company, Ltd., Berking, Essex; Dunod Edi­

teur, Paris; and Elsevier Publishing Company, Amsterdam.

The past decade has brought about such revolutionary progress in

science and technology that large sections of most of the existing technical dictionaries have become obsolete or incomplete. Further­more, scientific research is getting more and more internationalised, requiring, to an ever increasing extent, multilingual rather than bilin­

gual dictionaries. To meet this requirement, the publishing houses Elsevier and Olden­

bourg ere preparing a series of multilingual dictionaries for various special branches of science and technology. These books are treated and compiled by renowned specialists in the subject branches, which have at their disposal the abundant and multifarious sources of Europe and the United States, with which the publishing houses maintain re­

lations. The Fachworterbuch der Elektrotechnik has been compiled in accor­

dance with recommendations of UNESCO, which aim at the realisation of a plan providing for comprehensive coverage of oil fields of science and technology by suitable dictionaries in the languages necessary.

The languages ore classified into Anglo-Saxon, Latin, and German

g~oups.

The first part of the book contains the basic table of 7100 English/

American words. These English terms are listed in alphabetical order and they are heading word blocks which contain the equivalent French,

Spanish, Italian, Dutch, and German expressions. Where several word combinations ore possible, these are oil indicated in the appropriato;

language. The word blocks ore prefixed by reference numbers. The second port of the dictionary is subdivided into French, Spanish,

Italian, Dutch, and Germon sections, each containing on alphabetical

index, and the individual words ore followed by the appropriate re­

ference numbers in port one. A thumb index facilitates the quick location of each language section. This technical dictionary will undoubtedly prove to be a useful

working aid to the professional translator and to international engi­

neering staff. The voluminous material is very cleverly arranged - o pleasant

feature which helps to the efficient utilisation of the book. -or

Jahrbuch der Luftwaffe (Air Force Almanac)

by Kurt Neher and Kori Heinz Mende. 220 pages, more than 200 pictures, clothbinding, DM 19,80. Published by Wehr und Wisscn Verlogsgesellschaft mbH, Dormstadt, Germany.

Like the first issue of the "Johrbuch der Luftwaffe", which was published in 1964, this second volume hos as its aim to provide on insioht into the activities of the Germon Air Force (GAF) as o branch

of tt1c Germon Forces and on integrated port of NATO. Emphasis is placed on the explanation and dcscriptio_n of it~ vario~s

military and technical functions, with particular ottent1on being paid

to man in the service environment. The lOth anniversary of the postwar "Luftwaffe" is the subject of

on article by its "lnspekteur", Lt. Gen. Ponitzki, in which he reports

on the developments and achievements during the past decode. Another article deals with general military/political matters, an~

with the Germon participation in the North Atlantic Treaty Organi-

zation. . There arc 26 further contributions, some of which deal with practi-

cal questions of military operations and its technical and economical basis; others reflect the experiences of airmen, NCOs and officers in

the Germon Air Force. Four articles illustrate the efforts required for maintaining combat

readiness and, taken as a whole, they also reveal the orgonisollon of the German Air Force with the grouping into Flying, Air Defence,

Tronsport, ond Communication units. . . . Further articles provide more detailed information on sub1ects which

have been treated only generolly: dislocation of air defence, the per· sonnei situolio11, hygiene and sanitation, flying sofP.ty, mops ancl charts,

etc The mmn technical contribution concerns VTOL.

36

·Training· takes up much of the Almanac space. A general section on GAF schools and training methods is supplemented by articles about Germon pilot and navigator training in the United Stoles.

The Almanac is well illustrated; there are, inter olio, photos, sket­ches, and descriptions of 65 NATO aircraft, and some excellent multi­colour mop reproductions.

Reports on the day-to-day operations of o German airbase, flying missions to Turkey and to the UK, and the story of the NCO who builds his own aircraft in spore time are lively counterparts to the tech­nical articles.

-t-

Jahrbuch der Luft- und Raumfahrt

by Dr. K. F. Reuss. 466 pages with diagrams and pictures, plastic cover, DM 19,80. Published by Sudwestdeutsche Verlogs­onstolt, Mannheim.

The 15th volume of the • Johrbuch der Luft- und Roumfohrt" is in­tended to be on anniversary publication, but some chapters seem to contain less information than those of the preceding issues. For ins­tance, the chapter on international aviation hos been reduced; one looks in vain there for ICAO, EUROCONTROL, IFATCA, and IFALPA.

This con probably be explained by the publisher's policy to avoid reprinting each year information which is not subject to frequent chan­ges, and only referring to that information as published in earlier issues. Thus, printing space is gained for the "report section" of the

yearbook.

It is true, the N Jahrbuch der Luft- und RaumfohrtN is not just on aviation directory. Much core and effort is token to provide, in addition to names and addresses, on outhentical summary of major aviation events which happened in the Federal Republic of Germany during the year preceding the publication.

Some of the more important permanent information has now appa­rently been sacrificed at the cost of timely reporting on Germon avia­tion activity in 1965.

While topical reporting is very commendable, certain permanent in­formation should be considered important enough to merit publication in each volume of the yearbook, and we would hope to find it re­estoblished next year.

The 1966 issue contains information on air- and space low, on the

civil and military aviation administration in the FRG, including detail­ed sections pertaining to the aviation directorate in the Ministry of

Transport, the Bundesanstalt flir Flugsicherung {Federal Institute for Air Navigation Services), the Luftfohrt-Bundesomt (Federal Agency for Aviation), and the Federal Meteorological Service.

One complete chapter has been devoted to space activities. It in­cludes, inter olia, o comprehensive summary of space projects in East and West, and o list of all satellites in orbit (and crashed). Further sections of this chapter deal with space research and development in Germany, and the activities of such European organisations as EURO. SPACE, ESRO, and ELDO ore also mentioned.

Air traffic is the heading of the next chapter, which is subdivided as follows: Deutsche Luftfohrtliga, Annual Report of the Deutsche Luft­

hansa AG, airlines operating in Germany, Arbeitsgemeinschaft Deut­scher Verkehrsflughc'ifen, and miscellaneous aviation organisations. This chapter also includes o list of oil international airports in the FRG general aviation airfields, and glider sites. '

The following chapter treats with aviation industry, the International Traffic Exhibition Munich, the Deutsche Luftfohrtschau Hannover, avia­tion insurance companies, and industry sub-contractors.

One complete chapter is dedicated to the "Club der Luftfahrt".

General Aviation is a very interesting item of the yearbook, mainly

based on the report of the German Aero Club, which is the official representative of IAOPA in Germany. This chapter also contains rather detailed and comprehensive statistical data on the total number of general aviation aircraft in the FRG and their flying activity through­out the year.

There is also one voluminous chapter on aviation press, and on· other chapter deals with international aviation.

As in p1evious years, great care has been taken to make the year­book o valuable aviation guide. The suitable lay-out and a large index section deserve particular mention. EH

Cinema Review How to avoid the Twist

"WAKE TURBULENCE" is a new film released by the U.S. Federal Aviation Agency, to publicize the growing hazard of trailing vortex encounters. In 16-millimeter color film with sound track (running time about 15 minutes), the film may be borrowed by U.S. groups from the FAA Ad­ministrative Service Division, Film Library AC 43.1, P. 0. Box 1082, Oklahoma City, Oklahoma. In other countries arrangements to borrow the film may be made through your nearest FAA representative, or by direct contact with the Office of International Affairs, Federal Aviation Agency, 800 Independence Ave., Washington, D. C., USA.

The film introduces the trailing vortex problem with some exciting air-to-air photography. Animation tech­niques are then used in explaining the causes, behavior, and effects of the twin vortices that trail every airplane or

helicopter in flight. Back to live photography again, the film shows how to avoid the most serious effects of trail­ing vortices in airway and terminal operations. For the final punch, the film includes a closeup of the twin torna­does generated by a DC-8 in smoke tests at Los Angeles Airport.

Although no actual crashes are staged in the picture, the aircraft go through enough wild gyrations that the average pilot or controller in the audience will shudder at the hazards to which he may have exposed himself or others, unknowingly, in the past.

Very well done, and no more technical than it needs to be, the movie is quite suitable for flying clubs, safety seminars, pilot-controller forums, and controller associa­tion meetings. We would also recommend it highly as a useful addition to the film libraries of flying schools and ATC training agencies. TKV

Administrative Director of Frankfurt Airport retired Walter Luz, well-known German aviation pioneer, re­

tired from his post as Administrative Director of Frankfurt Airport on 1 st April 1966.

Aged 67 to-date, Director Walter Luz is looking back on a full lifetime in aviation and for aviation. As early as 1919, he joined the Luftschiffbau Zeppelin, Friedrichshafen, as administrative Director, and later he held various other positions as Director of aviation companies until 1926, when he was assigned the leading administrative post in

the Deutsche Lufthansa AG. Soon he became a member of the Board of Directors, and in 1942 he was nominated Chairman of the Board.

After the war, Walter Luz put all his energy and exten­sive experience into the re-establishment of civil aviation in Germany.

Thanks to his and technical Director Rudolf Lange's untiring efforts, Frankfurt "Rhein-Main" Airport has be­come one of the major international airports in Europe.

e

ANACNA, the Italian Air Traffic Controller's Association The Associazione Nazionale Assistenti e Controllori

della Civil Navigazione Aerea Italia, host to this year's IFATCA Annual Conference in Rome, is a small but very active association. Founded in August 1959, it counts among its members all civil air traffic controllers (50) of Italy.

The Italian military controllers (500) were initially un­able to join the Association, due to their service status which prohibits membership in any kind of association. Thanks to the initiative of ANACNA, however, the mili­tary controllers are now represented in the Association through corporate membership of the Inspectorate of Communications and Air Navigation, to which they all be­long, and which is a sub-directorate of the Italian Ministry of Defence.

The aims and objektives of ANACNA are quite similar to those of IFATCA: -- to promote safety, efficiency, and regularity in Inter-

national Air Navigation; - to assist and advice in the development safe, orderly,

and efficient procedures and systems in Air Traffic Control; to exchange, a national and international basis, ideas and experience with Air Traffic Control Experts;

- to foster the co-operation with national and internatio­nal aviation authorities and other institutions or per­sons concerned with air navigation. To realize these objectives, ANACNA has developed

considerable initiative during the past years. For instance, the Association, together with the Italian Airline Pilot's Association, sponsored a panel discussion on the present situation of air traffic control in Italy.

Another joint project of the Italian air traffic control-

lers and airline pilots was in early 1964 a symposium on "Some Aspects of Automation in Air Traffic Control".

In Autum 1964, ANACNA sponsored the demonstration of ATC-data processing systems, developed by Italian and foreign electronic companies. The Association also assists in the publication of the aviation journals "Aviazione di Linea" and "Transporti Aerei", by providing articles and studies on air traffic control.

Very important publications, which are presently under preparation by the Italian Air Traffic Controller's Associa­tion, are a Manual of Air Traffic Control and a detailed study on the Italian Air Navigation Services. The latter work is intended as a contribution to the reorganisation of the Air Traffic Services in Italy, and it is hoped that the study will facilitate this complex task.

Further on the ANACNA work programme are two meetings on the national level: one dealing with the liabi­lity of air traffic control staff, and the other being con­cerned with the air traffic controller's responsibility in respect of terrain clearance.

Military and civil air traffic controllers in Italy have no individual legal status and professional title corres­ponding to their tasks and activities. They are Govern­ment Employees.

ANACNA, has always recommended the creation of a separate corps of ATC staff and also advocotes the ideo of an independent air traffic control authority in Italy, according to the administrative system of ATS in other countries. The legal and technical organisation of this authority should ensure optimum operational efficiency. Since the Brussels Annual Conference in 1964, ANACNA is a member of I FATCA. CT

37

The International Federation

of Air Traffic Controllers Associations

Addresses and Officers

AUSTRIA

Verband Osterreichischer Flugverkehrsleiter A 1300, Wien Flughafen, Austria

President H. Brandstetter First Vice-President H. Kihr Second Vice-President H. Bauer Secretary R. Obermayr Deputy Secretary W. Seidl Treasurer W. Chrystoph

BELGIUM

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

President Vice-President Secretary Treasurer Editor

CANADA

A. Maziers R. Sadet R. Tamigniaux R. Maitre 0. Haesevoets

Canadian Air Traffic Control Association P. 0. Box 24 St. James, Man Canada

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

DENMARK

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

Danish Air Traffic Controllers Association Copenhagen Airport - Kastrup Denmark

Chairman Vice-Chairman Secretary Treasurer

FINLAND

Henning Throne H. Dall J. Thi lo P. Bressam

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

Air Traffic Control Helsinki Lento Finland

Chairman Vice-Chairman

38

Fred. Lehto Jussi Soini

Secretary Treasurer

FRANCE

Heikki Nevaste Aimo Happonen

French Air Traffic Control Association Association Professionnelle de la Circulation Aerienne B. P. 21 Aeroport du Bourget, Seine France

President First Vice-President Second Vice-President General Secretary Deputy Secretary Treasurer Deputy Treasurer

GERMANY

Francis Zamith Maurice Cerf J. M. Lefranc Jean Flament J. Lesueur J. Bocard R. Philipeau

German Air Traffic Controllers Association Verband Deutscher Flugleiter e. V. 3 Hannover-Flughafen, Germany Postlagernd

Chairman Vice-Chairman Vice-Chairman Vice-Chairman Secretary Treasurer Editor

GREECE

W. Kassebohm H. Guddat E. von Bismarck H. W. Kremer P. Storm H. Prell J. Gortz

Air Traffic Controllers Association of Greece Air Traffic Control Athens Airport, Greece

President Vice-President General Secretary Treasurer Councillor Councillor Councillor

ICELAND

Chr. Tzamaloukas G. Elias C. Kioupis P. Vasilakopoulos B. Egglezos P. Mathioudakis H. Kopelias

Air Traffic Control Association of Iceland Reykjavik Airport, Iceland

Chairman Vice-Chairman Secretary Treasurer

Valdimar Olafson Jens A. Gudmundsson Einar Einarsson Guolaugur Kristinsson

AN AID TO ATC! What is important assistance to Air Traff ic Controllers?

Tomorrow: Automation, but

today: Controlstrips and the

FLP 2012 59 STRIPHOLDER Appreciated by Air Traffic Controllers

all over the world !

Latest design: made of b lack p lastic, non reflecting,

handy, unbreakable, reducing noise level in A TC

considerably, improvement for RADAR Control ,

low price, fa st de livery.

Tolerances according to ATC req ui rements.

Qbering. HEINRICH PFUTZNER FRANKFURT AM MAIN Germany Zeil 29-31 Tel. 280468 - Telex 04-13443

IRE LAND

Irish Air Traffic Control Officers Association Aeronautical Section O'Connel Bridge House Dublin 2, Ireland

President Vice-President Secretary Treasurer

IS RAEL

D. J. Eglington P. J. O'Herbihy M. F. McCabe P. P. Linahan

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

Chairman Jacob Wachtel

ITALY

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

Chairman Secretary

LUXEMBOURG

C. Tuzzi L. Belluci

Luxembourg Guild of Air Traffic Controllers Luxembourg Airport

President Secretary Treasurer

NETHERLANDS

Alfred Feltes Andre Klein J.P. Kimmes

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

President Vice-President Secretary Treasurer Member Member

NEW ZEALAND

J. van Londen J. L. Evenhuis J. Thuring J. C. Bruggeman G. J. Bakker L. D. Groenewegen van Wijk

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

Hon. Secretary

NORWAY

Lufttrafikkledelsens Foren ing Box 135 Lysaker, Norway

Chairman Secretary Treasurer

40

R. G. Roberts

F.Oie P. W. Pedersen A. Torres

SWEDEN

Swedish Air Traffic Controllers Association Luftvartsverket Brom ma 10, Sweden

Chairman Secretary Treasurer

SWITZERLAND

E. Dahlstedt B. Hinnerson C. A. Starkman

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

Chairman

UNITED KINGDOM

Bern hard Ruthy

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

Master Executive Secretary Treasurer

URUGUAY

N. Alcock Mr. Rimmer E. Bradshaw

Asociation de Controladores de Transito Aereo del Uruguay Potosi 1882 Montevideo, Uruguay

Chairman Secretary Treasurer

VENEZUELA

U. Pallares J. Beder M. Puchkoff

Asociacion Nacional Tecnicos Transito Aereo Venezuela Avenida Andres Bello, Local 7 8129 Caracas, Venezuela

President Vice-President Secretaries

Treasurer Vocals

YUGOSLAVIA

Dr. Carlos G. Osorio Manuel A. Rivera Prof. Vicent Smart R. Salazar J. Blanco Villanueva Miss Amelia Lara F. Arturo R. Gil Alfonso Parra

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

President Secretary

I. Sirola A. Stefanovic

ROUGHlY ISN'T GOODENOUG Jetfleets cost millions to buy and to operate. Minor deviations from optimum flight paths mean ever larger economic

penalties. Rough ly isn't good enough. Only the most accurate,

reliable and comprehensive navigation system is good

enough-and Decca/Harco is such a system. It provides

the pi lot automatically with compound navigational information

derived from both self-contained and ground reference aids.

Computation is automated and manipu lation is minimal,

greatly reducing the pi lot's work load at a time when other

instrumentation is increasing. Decca Omni trac- world 's

most advanced airborne computer- controls the aircraft's

nav igational requirements, while on the ground the Decca Data

Link continuously relays to A TC al l in-flight information from

co-operating aircraft. With Decca/Harco complex traffic

patterns can be flown with maximum efficiency and minimum

delay, ensuring the best, most economic, use of air-space.

/

) DECCA· HARCO DOES THE JOB PRECISELY The Decca Navigato r Company L11111ted London

' I I I

' I I I

Y\ That's the value of orders for

PUSSIY RADAR in its big first year! AR-1 A IR-SU RV EILLAN CE RADAR More than 40 ordered for civil and mili­tary uses.

For use throughout the world including terminal approach and intermediate sur­veillance at London Airport.

NEW CONTRACT S REFLECT BIG­SYSTEMS CAPABILIT Y £A7m HUBCAP air defence systems for the Royal Australian Air Force. £4m Royal Air Force data- processing system.

MI NICOM - miniature communications control system for the Royal Air Force.

DEFENCE PROJECTS FOR BRIT AI N ANO OVERSEAS HF-200 heightfinders for Ministry of A viation. Classified projects involving equipment and systems.

METEOROLOGI CAL RADARS SERVE 61 COUNTR IES 43S to be Hong Kong's th ird Plessey Radar. WF2 for typhoon tracking in the Philippines.

SYST EMS FOR NAVAL VESSELS Radar 'package' developed for small sh ips. T hree Ghanaian corvettes fitted

with AWS-1.

SPEC IAL PRODUCTS Application of electro fo rming process to

electromagneti c alloys.

RESEARCH AND DEVELOPMENT Development contracts from British Government for advanced techniques.

SPAC E T ECHNOLO GY D evelopment of Satellite Communica-tions T erminals for land and ship borne

installations.

PLESSEY RADAR PLESSEY RADAR L IMITED Davis Road, C hessin gton, Surre y, England. Telephone: LOWer Hook 5222 Te lex : 262329 Cables : Plessey Chessington. PLESSEY ELECTRON ICS GROUP

~PE(R) 1 8B