IFATCA The Controller - October/December 1970

D 20418 F

% M F A r a

I j l

I FAT C A

JOURNAL

OF AIR TRAFFIC CONTROL

In this Issue

Fast Time Simulation

Heavy Jets and Airport Acceptance Rote Civil/Military Coordination

Marconi air traffic control

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4 second data rate with

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Corporation Members of the International Federation of Air Traffic Controllers' Associations AEG-Telefunken, Ulm/Donau, Germany Air Vision Industries, Inc., Montreal, Canada The Air Transport Association, Washington D. C., U.S.A.

Wolfgang Assmann GmbH., Bad Homburg v.d.H. Compagnie Generale de Telegraphie sans Fil Malakoff, Paris, France

Cossor Radar and Electronics Limited,

Harlow, England The Decca Navigator Company Limited, London

ELLIOTT Brothers (London) Limited Borehamwood, Herts., England FERRANTI Limited

Bracknell, Berks., England Glen A. Gilbert & Associates, Washington D. C., U.S.A. IBM World Trade Europe Corporation, Paris, France

International Aeradio Limited,

Southall, Middlesex, England ITT Europe Corporation, Brussels, Belgium Jeppesen & Co. GmbH, Frankfurt, Germany The Marconi Company Limited Radar Division Chelmsford, Essex, England N.V. Hollandse Signaalapparaten Hengelo, Netherlands

N.V. Philips Telecommunicatie Industrie Hilversum, Holland

The Plessey Company Limited Chessington, Surrey, England Selenia — Industrie Elettroniche Associate S.p.A.

Rome, Italy The Solartron Electronic Group, Ltd. Farnborough, Hants., England 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 corpora

tions, organizations, and institutions interested in and concerned with the maintenance and promo tion 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 Con troller" is offered as a platform for the discussion of technical and procedural developments in the fi e l d o f a i r t r a f fi c c o n t r o l .

1

FAT C A

JOURNAL

OF

AIR

TRAFFIC

CONTROL

THE CONTROLLER Frankfurt am Main, October/December 1970

Vo l u m e 9 • N o . 4

P u b l i s h e r : I n t e r n a t i o n a l F e d e r a t i o n o f A i r T r a f fi c C o n

trollers* Associations, S. C. II; 6 Frankfurt am Main N.O. 14, Bornheimer Landwehr 57a.

Officers of IFATCA: A. Field, O.B.E., President; J. R.

Campbell, First Vice President; G. Atterholm, Second Vi c e P r e s i d e n t ; G . W. M o n k , E x e c u t i v e S e c r e t o r y ;

H. Guddat, Honorary Secretory; J. Gubelmonn, Trea surer; W. H. Endlich, Editor.

Editor: Walter H. Endlich, 3, rue Roosendoel, Bruxelles-Forest, Belgique Telephone: 456248 Publishing Company, Production and Advertising Soles Office: Verlog W. Kramer & Co., 6 Frankfurt am Main N014, Bornheimer Landwehr 57a, Phone 434325,492169, Frankfurter Bonk, No. 3-03333-9. Rote Card Nr. 2.

Printed by: W.Kromer&Co., 6 Frankfurt am Main NO 14, Bornheimer Landwehr 57a.

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

Contributors ore expressing their personal points of view and opinions, which must not necessarily coincide with t h o s e o f t h e I n t e r n a t i o n a l F e d e r a t i o n o f A i r Tr a f fi c Controllers' Associations (IFATCA).

IFATCA does not assume responsibility for statements made and opinions expressed, it does only accept re

C O N T E N T

sponsibility for publishing these contributions.

The Application of "Fast-Time" Simulation Contributions are welcome as are comments and criti

cism. No payment can be made for manuscripts submitted

Techniques to the Study of ATC Systems R. J. Burford

for publication in "The Controller*. The Editor reserves

the right to moke 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 re printing any part of this Journal.

Effects of Heavy Jets on Airport Acceptance Rate Tirey K. Vickers WHAKATOPA — The Hovering Helper R. A. Soar Miscellania

Civil Military Coordination and Unification o f A i r T r a f fi c S e r v i c e s

Civil Military Coordination in New Zealand 23 R. A. Soar Advertisers in this Issue:

Borg-Warner Controls Ltd. (2);

Book

Review

24

Ferranti Ltd. (12); The Marconi Co. Ltd. (Inside Cover, Bock Cover Olympic Airways (15);

Selenia S.p.A. (Inside back cover).

Picture Credit:

GPS Sciences Ltd. (8, 10); Vickers (13, 14); Whites Aviation Ltd. (16, 17).

3

The Application of "Fast-Time" Simulation Techniques to the Study of ATC Systems

by R. J. Burford*

Introduction to ATC Systems Analysis General 1.1. Planning for the development of a future air traffic

control system, or for the improvement of an existing sys tem, requires a substantiated appreciation of the capacity and performance of the present system and of the project ed future system.

1.2. With the growing volume of air traffic and the ad vancement of modern technology, ATC planners are con cerned with making decisions relating to the organisation,

development and control of an increasingly complex and sophisticated dynamic system. In many instances it is no longer possible to decide solely on the traditional basis of experience, intuition and "rule of thumb", especially

rules and procedures, and performance restrictions of indi vidual aircraft, such as restrictions on the range of accept able cruising levels, limitations on rates of climb and descent, and the level of navigational capability.

1.5. An ATC system contains Decision Making Elements, air traffic controllers and pilots, who receive information concerning the current state of the system and then exer cise a Control Action over the aircraft with the express pur pose of achieving a stated objective — the provision of an expeditious flow of traffic — as closely as possible in con

formity with the expressed wishes of the aircraft, whilst maintaining safety by ensuring that potential conflicts be tween aircraft are detected and resolved without overload

ing the ATC organisation. The control action exercised can

sums in capital investment and affects the safety and secu

lie anywhere within the strategic/tactical spectrum rang ing from preset height restriction to aircraft vectoring. Such action takes place in the presence of External Agents which can modify or affect the system independently of the de cision making elements. Examples of external agents are

rity of large number of human lives. Under these circums

meteorological factors such as wind and temperature, er

when the decision involves the selection of the best of seve

ral alternatives, involves the employment of very large

tances it has become essential to turn to the Operational Research techniques which have been developed, and

which are now readily available to derive data on which

rors and uncertainty in the navigation of the aircraft, and uncertainty in the ATC prediction of the traffic situation.

sound decisions may be based.

1.6. The system limitations imposed by the constraints and the control action result in finite capacities of sub

Basic ATC System Elements

systems (specified volumes of airspace, runways, etc.) and this in turn leads to the formation of queues of aircraft at

1.3. Before discussing the methods by which present or proposed ATC systems can be investigated it is useful to define the basic system elements in Operational Research t e r m s .

1.4. In general an ATC system is characterised by a Sta tic Environment, the route structure, through which a flow of individual Items, the aircraft, are processed according to specified Constraints. The constraints may depend upon the identities and states of the individual aircraft as well as

upon the environment and usually take the form of ATC

one or more places within the environment, for example,

in stacks for inbounds, and at the runway holding point for outbound aircraft. Congestion may lead to the re-routeing of aircraft in an attempt to obtain improved overall system capacity. Here re-routeing is taken in its wider sense to include the allocation of an alternative cruising level, a change to a parallel track, interruption of a flight profile by stepping-off a climb or descent, as well as the alloca tion of an alternative route. Such action results in penalties to the system user in terms of delay or allocation of nonoptimum flight paths.

1.7. Summarising, an ATC system consists of: a) b) c) d) e) f) g)

a Static Environment, individual Items flowing through the environment, Constraints on the movement of items, Decision Making Elements, Control Action, a General Objective, External Agents,

Methods of Analysis General

2.1. ATC systems can be evaluated either by direct ex perimentation with the real system or by construction of, and experimentation with, a model which represents the * GPS Sciences Limited

4

— the route structure; — the aircraft; — procedural or physical in nature;

— the ATC unit or pilot; — strategic/tactical spectrum; — a safe, orderly and expeditious flow of traffic; — meteorological conditions errors and uncertainties.

behaviour of the real system. Such a model may take vari ous forms, for example: — a Descriptive model in which a detailed qualitative ex

planation of the salient features of the ATC system

under investigation is prepared by use of flow diagrams and written descriptions;

— a Mechanical model involving the construction of a phy sical working model;

teristics, constraints or loading of the system. Such tech

— on Algebraic model in which mathematical equations

queueing models, to study certain sub-elements of the ATC system to varying degrees of accuracy. However, it is diffi

describing the behaviour of the system are derived; — a Simulation model in which the action of the ATC sys tem as time advances is represented by an analogous analytic system; experiments carried out with the simu lation model enable the characteristics of the original system (real or hypothetical) to be studied and its per formance, reaction and capability to be evaluated.

Experimentation with the Real System 2.2. For an existing system the technique of expert ob servation of its behaviour and the analysis of specifically c o l l e c t e d d a t a c a n a c h i e v e s u b s t a n t i a l s h o r t - t e r m b e n e fi t s

in terms of improvement of airspace sectorisation and rationalisation of ATC procedures to increase ATC system

capacity. However, such methods of operational analysis are necessarily constrained by the generally fixed nature of the operational environment of the ATC system, and by the amount of procedural experimentation which is accept able to both ATC Authorities and Aircraft Operators.

2.3. Experimentation with changes in rules and proce

dures in the real system can result in disruption of the sys tem under study and is usually costly in time and money when applied to complex situations. The pertinent features of the ATC system are not always subject to control in the actual system, and it is not possible to make experimental studies of the effect of introducing new types of aircraft, navigational equipment, radars, etc. which are still at the design stage.

2.4. In many cases experimentation with the real system is impossible because the alternative solutions to be tested involve irrevocable and mutually exclusive changes to the environment, for example the siting of a new airport.

2.5. Finally experiments with real ATC systems could in

volve danger to life and property which cannot be justified.

Descriptive Models 2.6. The formation of a detailed descriptive model is on intrinsic step in almost all model building and its construc

niques have been used, based on probability theory and

cult, often impossible, to study complex dynamic system behaviour by mathematical analysis particularly where sys tem changes are induced as a result of human decisiontaking.

2.9. In general an ATC system is complex, involving many variables and features which cannot be expressed in simple

mathematical terms, and which by the very nature of the problem cannot be sub-divided into simpler secondary pro blems which can be studied algebraically.

2.10. If mathematical solutions are obtained this is usual

ly as a result of numerous simplifications and assumptions which in some coses are acceptable, in that the specific ob jective of the investigation is satisfied. However, in general the degree of detail in the description of the ATC system is reduced to on unrealistic level, which is unacceptable for useful system evaluation.

Simulation Models

2.11. The remaining technique is that of simulation, which involves the study of the behaviour of a representative mo

del of the real-life system and of experimenting with the model very much in the way that one would wish to ex periment with the actual systems.

For the purpose of investigating ATC systems, simulation techniques may be considered as divided into two distinct fields, Real-Time Simulation and Arithmetic Simulation.

2.12. Real-Time Simulation, sometimes called dynamic simulation, is the normal method of simulation employed

by ATC administration for training and evaluation pur poses. It is called "Real-Time" because it takes the same time to run a simulation as it would take to experiment with the real system, if this was possible. In Real-Time Simula tion the reactions of human participants involved in the operation of the system ore not simulated artifcially. In other words, no attempt is made to model human beha viour and the simulations ore operated by human control

lers performing their normal functions at the simulator positions, with aircraft and other communication sources being synfhesised by supporting staff.

tion sheds a great deal of light on the problem to be in vestigated and results in a detailed understanding of the system behaviour. However, since it cannot produce measu res of system performance and capacity it must be accepted as only a first step in system evaluation.

2.13. The simulated traffic is processed through the simu lator following a normal time scale, modified as necessary

Mechanical Models

o f m a n / m . a n a n d m a n / m a c h i n e r e l a t i o n s w i t h i n t h e AT C

2.7. Because of the complexity and form of ATC systems, they are not amenable to representation by physical work

system.

ing models.

advantages in regard to the broader problem of largescale system evaluation. Its primary limitations are:

Algebraic Models

— the method is expensive in terms of special equipment, time and manpower;

2.8. If the behaviour of a system to be studied can be expressed by mathematical equations then various mathe matical methods may be used directly to investigate the effects of alterations to the environment, aircraft charac

by instructions from the controllers in accordance with the rules ment. ly as duced

and regulations selected for the particular experi Actual operating conditions are reproduced as near possible, thus enabling maximum realism to be intro into the laboratory study of the ergonomic problems

2.14. However Real-Time simulation does suffer many dis

— the available dynamic simulation facilities limit the pro portion of the total system which can be examined in each exercise;

5

— because of the scale of effort involved, the sample and duration of conditions tested is usually small; the eva luation of system performance is correspondingly limit

ed by both this factor and also the time required for each exercise;

— the quantitative comparison between different systems

man/machine relationships — a task for which Real-Time

simulation is admirably suited. Even so. Arithmetic Simula

tion is an important tool for the evaluation and design of the ATC ground organisations, since it can provide outputs which quantify controller workload in terms of defined manual, mental, visual, speech and aural tasks.

may be invalidated by human variations from exercise to exercise.

Arithmetic Simulation

Arithmetic Simulation Techniques

2.15. The limitations of Real-Time Simulation can be large ly overcome by eliminating the human factor and simulat ing the fourth dimension-time. This is precisely what hap pens in the Arithmetic Simulation method where the com plete system, including the behaviour of human partici

— Fixed Time-step Simulation,

pants, is expressed in mathematical or logical terms. The

— Event to Event Simulation.

General

3.1. Arithmetic Simulation can be subdivided into two

basic types for the evaluation of ATC systems:

replacement of human processes by purely logical mechan isms enables time to be simulated by treating it as a simple mathematical parameter. As the whole ATC system is trans lated into logical and arithmetic terms, full use can be

made of high speed digital computers, thereby providing an advanced method for the evaluation of complex ATC

systems. With time expressed as a parameter, the simula tion process may operate many times faster than real-time i n w h i c h c a s e i t i s t e r m e d F a s t - Ti m e S i m u l a t i o n . F o r e x

ample, a specific simulation model of a Terminal Area

constructed by GPS can process a traffic sample of 5000 aircraft, representing a 24-hour traffic sample, through a complex Terminal Area in about 10 minutes using a CDC 6600 computer, and this includes computer analysis of sys

Fixed Time-step Simulation 3.2. In this form of simulation time is advanced in cons

tant, discrete increments, corresponding for example to the period of rotation of a radar head. The condition of the system is examined after each increment of time and all

operations or decisions deemed necessary are carried out

before the simulated clock, set up to record the correspond

ing time in the real system, is advanced further. The me thod is of value when the system to be examined is one of continuous change or involves many interacting events

2.16. The range of situations which can be examined and

occurring in rapid succession or with known periodicity, ffowever, as the model may have to be examined many times in this way before an important change does occur, the Fixed Time-step simulation method is generally waste ful of computer time and effort and is unlikely to give a

the duration of each simulation are increased significantly

significant gain factor over real-time operation.

tem performance — thus operating some 150 times faster than real-time.

compared with Real-Time simulation thus offering statisti

cally significant results very quickly and so increasing the value of simulation techniques in the evaluation and plan

Event to Event Simulation

ning of ATC systems.

3.3. If the real-life situation is one in which interactions

2.17. Arithmetic Simulation models are extremely power ful since they can be constructed to take into account as

much detail as Is required from the real system. The speci fication of the route structure, ATC procedures, separation minima, capacity constraints etc. can be supplied as input data to the models and therefore can be varied quickly and easily. The output data which can be produced during suc cessive runs of the model is then available to the ATC sys tem planner as a basis for improvement of existing route structures and ATC procedures, for identification of fac

tors likely to limit future capacity, and for comparison of alternative system development proposals on a cost-effec tiveness basis.

2.18. The primary task for which Arithmetic Simulation models ore used is the quantitative comparison of the capacity and systems performance associated with alter native system designs or equipment development propo sals, to facilitate management of the Research and Deve lopment budget and the allocation of resources in exten

sion and improvement of existing ATC systems. The Arith

metic Simulation approach has one main limitation in that

having effectively eliminated the participation of human controllers, it is not generally suitable for investigating the

detailed ergonomic factors of ATC, i. e., the man/man and 6

between system entities take place at discrete points in

time, separated by intervals of inactivity, routine activity

or predictable behaviour, the simulation model need be examined only when an event significant in the context of

the simulation actually occurs. The simulated clock may therefore be advanced from one event to the next event in

chronological order and this gives rise to Event to Event Simulation where time is advanced by variable increments.

3.4. Examples of events in an ATC system are: warning of an aircraft's entry to a sector; — aircraft entry to a sector; — aircraft exit from a sector; — start of a conflict detection search;

start of controller intervention to avoid a predicted con flict;

aircraft ioining a system queue (e. g. holding stack, out bound queue); aircraft leaving the system queue; aircraft request for an ATC service; time a pilot sees another aircraft under VFR conditions.

3.5. Events occur at discrete points in time (time of entry, exit, start, finish, request etc.) and are usually, but not al ways related to particular aircraft rather than with the

total ATC system. Associated with these events are speci fic ATC activities or phases of aircraft progress through the simulated environment. An event normally defines the start or finish of the activity or flight phase.

3.6. To illustrate this relationship the warning of an air craft's entry to a sector could initiate a Planning Activity in which the proposed flight path of the aircraft through the warned sector would be considered and, if necessary, the flight path suitably modified from, a knowledge of predict ed airspace and runway loadings to avoid overloading the sector. Such modification could be en-route holding or

complex series of logical steps and hence to computer instructions. However once the initial development of fasttime simulation has been completed the model provides a very rapid method of evaluating ATC systems and may readily be tailored to suit individual requirements, either

by suitable specification of input data, or by minor changes to the programmed logic.

The Fast-Time Simulation Technique

allocation of an alternative route to the aircraft concern

ed. It is important to note that the decisions token during such an activity can, and usually will, affect the actual timing of the next event for the aircraft, in the example chosen the aircraft's entry to the sector.

General

F a s t - Ti m e S i m u l a t i o n

4.1. In Fast-Time Simulation traffic samples are proces sed through the simulated route structure using the same procedural environment as the human assistants and con trollers would in a Real-Time Simulation exercise taking place in clock-time.

3.7. Using high speed digital computers. Event to Event

4.2. Because of the simulation techniques used it is pos

A r i t h m e t i c S i m u l a t i o n e n a b l e s e x a m i n a t i o n o f o n AT C

sible to calculate the actual as well as the predicted future

system to be undertaken at a speed significantly in excess of real-time. For this reason the technique is usually re

flight path for each aircraft within the simulation. It is not

ferred to OS Fast-Time Simulation when applied to the evaluation of ATC systems, in order to emphasise one of the main advantages over Real-Time Simulation.

3.8. Further advantages over Real-Time Simulation ore:

— ability to repeat a simulation exercise under precisely the some controlled conditions;

necessary therefore to wait, for example, until an aircraft reaches a certain point or altitude before assessing whether a conflict would actually exist with other traffic.

4.3. The fore-knowledge of the future traffic situation in a s i m u l a t i o n m o d e l e n a b l e s t h e t i m e a t w h i c h AT C d i s

covers that intervention or action will be necessary to be d e t e r m i n e d i n a d v a n c e . P r o v i d e d t h a t t h e AT C r u l e s a n d

— knowledge that the differences in system behaviour on

procedures, e. g. for conflict detection and resolution, can be specified with sufficient precision for them to be pro

changing the ATC rules or environmetal conditions ore due solely to the specified and deliberately introduced

grammed, it is also possible to determine in advance what action a controller will find it necessary to take and to cal

changes to the system;

culate, in advance, what further effect his action will have

— quantifcation of system performance to a measurable accuracy which cannot be obtained by Real-Time Simu lation technique;

— ability to simulate a wide range of conditions and to process a larger traffic sample;

— ability to simulate large ATC systems as a whole; — ability to simulate the effect of introducing ATC equip ment which is still in the design phase; — removal of the requirement for a large number of qua lified personnel to be included in the simulation team.

3.9. These advantages of Fast-Time Simulation stem directly or indirectly from the replacement of the human participants involved in ATC systems by the process of modelling. The two obvious disadvantages are: — since the human element is removed, Fast-Time Simula tion cannot be used to study detailed ergonomic pro blems;

— the initial development of Fast-Time Simulation models

can be a time consuming process, involving several man

o n t h e f u t u r e t r a f fi c s i t u a t i o n .

4.4. In Fast-Time Simulation a controller's decision can

be made at any time during the simulated period — be fore, or up to, the time at which this process would occur in real-life — within a limit set by the occurance of any other intervening event which changes the state of the simu lated system.

4.5. Following each decision, the relevant details con

cerning the progress of the aircraft through the system, and the ATC decisions that were required to be made in re spect of it, can be recorded.

4.6. By detailed analysis of on ATC system it is possible to define the action of ATC, and the progress of aircraft through the system, in terms of a number of activities. In general these activities are either

a) describing a specific ATC process — such as — the allocation of a Standard Instrument Departure or Standard Arrival Route;

— the sequencing of inbound aircraft; — intervention to resolve a potential conflict; or

years of specialist mathematical and programming

effort for a large model.

3.10. The major part of model development is associated with the reduction of the controller's decision making pro cess and his inherent ability at pattern recognition, to a

b) describing a specific phase of an aircraft flight — such a s

— final approach, flight through a sector or movement on

the taxiways; or a combination of a) and b).

7

4.7. Because of the ability, inherent in Fast-Time Simula

rect representation of system behaviour and speed of ope

tion, of calculating aircraft progress and determining inter

ration of the simulation model.

action between traffic and controller action in advance,

4.11. In general an event and its associated activity are

it is possible to condense the continuous nature of an acti vity to take place at a discrete point in time — an event at the start of the activity. For example, in activities of type b)

connected with individual aircraft and take into account all

real-life ATC processes which would be encountered up until the next event time for the aircraft. The progress of

all the continuous and routine functions of the ATC system,

an aircraft through the system need only be amended at

such as routine supervision, can be carried out in the simu lation at the time the activity is initiated.

the Critical Times associated with that aircraft since be

4.8. The continuous clock of the real-life system is there

culated in advance and will not be altered by the chang

by replaced in Fast-Time Simulation by a discrete clock

ing state of the system.

which advances by jumping from one event time to the next event time, wihout having to be moved labouriously

4.12. Flowever the aircraft's existence can be taken into

tween such events the progress of the aircraft can be cal

traffic situation in the simulation needs to be examined

account during the activities associated with other aircraft through, for example:

only at event times since between events the behaviour of

— conflict detection routines;

through intervening times when no activity can occur. The the simulated ATC system has been predicted in advance.

4.9. Events determine the limits of predictability for the

— density limitations (by sub-system capacities); — size of aircraft queues.

total ATC system being simulated and are therefore asso

An aircraft can therefore affect the state of the system at all times although changes to its own passage through the ATC system, whether on the ground or in the air, need only

ciated with activities involving positive controller decisions based on current knowledge and estimates of the system.

Since events are usually associated with controller deci

sions, and actions which change the state of the system, they are known as Critical Events, and the times at which such events occur are known as Critical Times.

be considered at a limited number of Critical Times.

4.13. If the correct Critical Events are selected, the time of a Critical Event cannot be determined with any certainty until the simulated clock has advanced to the time of the

4.10. The correct choice of events and activities is crucial

previous event connected with the same aircraft and the

to the success of a simulation both from the point of cor

associated activity carried out. This is the direct result of

Start of Simulation

Aircraft entering simulation

Rank events in chronological order

Select the earliest e v e n t

Delete aircraft from simulation on exit from AT C s y s t e m

Advance simulated clock to time of earliest e v e n t

Complete activity associated with selected event and

calculate resulting new

8

events

simulation of ATC decision-making and the introduction of stochastic factors, including the deliberate introduction of perturbations in the Traffic behaviour.

of data inputs but their application can be controlled by

4.14. Since it is essential that activities take place in the correct time sequence a list of current and future events,

rules and procedures, simulation programs should be mo

together with their associated activities, must be maintain ed in strict chronological order within the simulation model.

4.15. The earliest event in this list can then be selected

when a time advance is required in order to determine the

next clock position. Once an activity has been completed the associated event can be deleted from the list, and any new events determined during the activity entered in the correct chronological position.

suitable use of these parameters.

4.20. In order to obtain flexibility with reference to ATC dular in construction, consisting of an interconnected num ber of distinct sub-programs, sub-routines or procedures, each representing a specific part of the ATC system logic.

In this way routines may be individually removed, reorga nised or rewritten to represent any necessary changes to the ATC system logic, without disturbing the general frame work of the model. This facility enables a wide variety of ATC systems to be simulated on the same model with the minimum of re-programming and debugging. Using this technique, an En-route Model, for example, could be tailor ed to ft either a European or an American environment.

Simulation Process

4.16. A simulation starts with the ATC system in some spe cified initial condition — usually empty because of the lull in traffic in the early hours of the morning. The simulated

Planning a Simulation Study

clock is set to its initial value and the first event time de

the ATC system for the sake of imitation — but to enable

termined, usually from the information contained within

system behaviour to be studied from a model which re

the traffic sample specification. The clock is then advanced to the first event time, the necessary activity carried out and the next event determined. The simulation then pro ceeds as shown in Figure 1, with new aircraft being entered to the simulated ATC system at appropriate event times specified by the selected traffic sample. Similarly aircraft are removed from the simulation by specification of an event at a time when the aircraft can no longer affect the state of the ATC system under investigation. The simulation is allowed to continue until the desired period of time has

5.1. The purpose of constructing a model is not to imitate

presents the important features of the real-life system, and the decision rules and regulations that determine how these features are modifed as time progresses.

5.2. Basically a simulation model should be:

— simple enough so that it can be manipulated, under stood and run within a reasonable timescale and bud get;

— representative enough to meet all the objectives of the

been simulated. At this time the simulation is terminated

and the data on system performance and capacity analys ed for output in a digestible form.

investigation for which it was constructed or modifed;

— complex enough to accurately represent the ATC system with respect to the study objectives.

Model Flexibility 4.17. It is essential to build into simulation models a high degree of flexibility so that they may be readily applied to similar, though different, environments. For example a Terminal Area Model should be easily adaptable to any major terminal area such as New York, London or Paris.

Such flexibility may be achieved by constructing the simu lation model so that the ATC system environment is speci fied as much as possible by input data.

4.18. Typical input parameters, to be "read in" prior to running a simulation are: — the route structure, position of navigational aids, etc.; — the traffic sample and aircraft performance characte ristics;

— separation minima;

— capacity limitations of specified runways and volumes of airspace; — height restrictions;

— uncertainties in navigational accuracy.

5.3. In order to construct such a model the simulation

team must be fully conversant with ATC systems. The prin

ciples underlying all operations must be fully comprehend ed, and the rules and procedures, often built up on an adhoc basis, must be reduced to logical terms.

5.4. By selecting only those events which are critical to the processing of aircraft through the particular ATC sys tem under study, by the use of Event to Event Simulation techniques, and by the programming of the model on a large digital computer, the actual simulation process can

be made to proceed very rapidly — many times faster than real-time. It is this speed of simulation, together with the ease of analysis and presentation of the resulting simulat ed performance, that makes Fast-Time Simulation such an attractive and valuable planning and evaluation tool.

5.5. For the successful application of these techniques

the simulation study must be subdivided into a number of basic tasks:

— — — —

Formulation of the problem; Def nition of objectives; Project planning; Construction of a descriptive model;

— Selection of quantitative criteria for the measurement 4.19. The processes of ATC, however, form part of the simulation model logic and cannot be specified by means

of system performance and capacity; — Collection of data and forecasting demand;

9

METHODOLOGY

OF

AT C

SYSTEM

A N A LY S I S B Y FA S T — T I M E S I M U L AT I O N

E N V I R O N M E N T

DESCRIPTIVE

MODEL

EXPERIMENT

ROGRAMS

PA R A M E T E R S

COMPUTER

A N A LY S I S OF

MODEL

AND

OF

D

ATA

RUNNING

I N T E R P R E TAT I O N R E S U LT S

RECOMMENDATIONS

— Formulation of a mathematical model;

vestigation. This is best done in close collaboration with

— Formulation of computer program; — Estimations of model parameters; — Preparation of simulation data;

those personnel involved in the operation or planning of the actual ATC system.

— Va l i d a t i o n ;

5.10. From such an analysis, detailed descriptions and flow diagrams can be prepared of the various elements of the system. Usually the system elements can be classified under four broad headings:

— Design of simulation experiments; — Computer running;

— Analysis of simulation data; — Recommendations.

5.6. The team carrying out the simulation study should be composed of Mathematical and Operational Research Analysts with detailed knowledge of simulation and other modelling techniques. Operational Analysts experienced in the field of ATC and Programmers experienced in highlevel and simulation languages.

— system environment;

— aircraft progress through environment; — constraints on the movement of aircraft;

— decision logic employed by ATC. This creates a descriptive model which serves to define and isolate the salient features of the system and to specify qualitatively the interaction between elements of the sys t e m .

5.7. A flow diagram for the methodology of studying an

ATC system by Fast-Time simulation techniques is given in Figure 2, showing the relationships between the funda mental stages of the study.

5.8. Before any attempt at building a simulation model is made it is essential to have a clear statement of the terms

of reference and the objectives of the investigation since

the particular model of the system will vary according to the purpose of the study and will only answer those ques tions that it has been designed to answer.

5.9. The first stage in actually building a model should be the detailed study of the operation of the real or hypo thetical ATC system, which is to be the subject of the in 10

5.11. At this stage the description should also Include: — specification of the objectives of the ATC system;

— specification of the criteria by which systems perform ance and capacity should be measured; — specification of the alternative principle and methods of control which it is desired to evaluate.

5.12. The next stage in the modelling process Is to trans late the detailed descriptions and flow diagrams into mathematical/logical terms, and to select the appropriate activities and associated events into which the ATC proces ses must be sub-divided for successful application of the Event to Event simulation technique.

5.13. The mathematical model must then be programmed for input to a digital computer, usually a fast machine with large data storage to allow for a sufficiently detailed des cription of the ATC system.

5.14. The computer model generally consists of three cons tituent parts — the programs which contain the basic rules for processing aircraft through the simulated environment, e. g. for conflict detection and resolution, and for input and output of simulation data;

— the parameters which control the application of the rules built into the programs: examples of such para meters would be separation minima, runway constraints, capacity limitations and distributions of errors and re action times;

— the data which specifies the physical structure of the ATC system and the nature and performance of the traf fic to be processed.

5.15. The study stage associated with the analysis and interpretation of results requires considerable effort since it is concerned with translating the numerical results output by the model into operationally meaningful terms which can be readily understood and digested.

5.16. Once the simulation model has been programmed

and debugged, it should be validated by using the model to reproduce known conditions. This provides a check which ensures that all the relevant factors hove been in

cluded in the model, and that the behaviour of the simula tion model closely resembles that of the real system.

5.17. Following any improvement to the model necessitat ed by the validation process, the simulation model can then

pressed in terms of current traffic levels or traffic forecasts based on projected growth, con be translated into measu res of systems performance which are operationally mean ingful. From these measures, the load upon the total simu

lated system and upon sub-systems can be evaluated to gether with the relative benefits and penalties to system users and system operators. The detail results supplied by simulation models enable ATC planners to identify and isolate those parts of the system that are restricting effi ciency and capacity, and provide planners with quanti

tative information on which development policies, which will increase the overall efficiency and capacity of the sys tem, con be based.

6.3. Simulation models of ATC system are capable of providing results over a wide range of ATC problems for example: — the evaluation of ATC system and subsystems capa cities;

— the evaluation of ATC system reaction to increased levels of traffic demand;

— the quantification of benefits and penalties associated with variations of policies, control action and facilities; — the investigation and identification of relationships be

tween different system performance measures and sys tem loading or demand;

— the evaluation of ATC system reaction to the introduc tion of a new aircraft type (for example VTOL or SST); — the evaluation and comparison of ATC system perform ance associated with airport sites or airport usage policy; — the evaluation and minimization of ATC user and ope rator costs;

— the evaluation of design parameters for future equip

be applied to assess the system performance and capacity of the various proposed system configurations. Detailed examination of the results will not only evaluate system capability, but will also indicate the areas of limiting capa cities, congestion, and potential weakness, in the system simulated and provide important data which will aid the redesign of the system.

Conclusions 6.1. Fast-time simulation has proved to be a very power ful research and evaluation tool in dealing with the com

plex, sophisticated and dynamic nature of ATC systems. The technique has the ability to cope with problems which are mathematically intractable and which resist solution by

other analytical methods, whilst at the same time avoiding the potentially high costs, dangers and difficulties of ex perimenting with the real system. It has significant advant ages over Real-Time Simulation in as far as speed of ope ration, size of the problem area that can be tackled, re

peatability and the removal of unknown factors introduced by human variability are concerned. However, the tech nique is limited in the examination of purely ergonomic problems concerning the interface between the controllers and their equipment — an area which is eminently suitable for investigation by Real-Time Simulation.

6.2. Fast Time simulation provides a very efficient me thod by which demands imposed upon on ATC system, ex

ment;

— the evaluation of benefits and costs derived from the

Introduction of different types of radar and/or navi gational systems.

6.4. The Fast-Time Simulation Technique can be applied right across the whole spectrum of ATC operation from the simulation of Ground Movement Control to the accelera

tion and deceleration phases of supersonic flight with the construction of models of differing complexity and scope tailored to the basic objectives of an investigation. The models currently available from GPS Sciences include; — — — — — —

an Upper Airspace Model; an En-route airways linking two terminal areas; a Terminal Area Model; a Ground ATC Organisation Model; a Runway Model; an Airport Taxiway and Ground Movement Control Model.

6.5. The technique is by no means limited to the model ling of ATC systems and has been satisfactorily applied to the movement of passengers and cargo through Terminal Buildings, to rail, road and water transportation systems, even to the investigation of lift control systems. In fact any system involving the movement of men or materials from place to place through a network subjected to specific constraints and controlled by human or automatic decision

making elements can be usefully investigated by the appli cation of the Event to Event, or Fast-Time, Simulation tech nique.

n

Air Traffic Control in the 70's

Ferranti have done

the groundwork The steadily increasing volume of air traffic is prompting many civil

Experience with simulators helps to perfect operational systems

aviation authorities to make an urg

Ferranti ATC simulators for the training

ent re-appraisal of control methods.

of controllers and the evaluation of new

For many airports and air traffic

ATC techniques are already widely known.

control systems, the Seventies are

going to demand much more sophis ticated systems than those currently in

use.

The design of effective computer based

systems for air traffic control demands

considerable experience and a close knowledge of ATC- procedures. Ferranti have that experience and knowledge. They have been engaged in the design and development of ATC systems for over 12 years, and were in fact the first company

to apply computers to air traffic control in

the U.K. This was at the Oceanic Control Centre at Prestwick, where a Ferranti computer was installed to evaluate new solutions to the ATC problems of the North Atlantic.

Contributing to their international accept ance has been the long list of simulation

projects carried out on the equipment installed at Hum Airport, Bournemouth, as p a r t o f t h e A i r Tr a f fi c C o n t r o l E v a l u a t i o n Unit of the Board of Trade. Ferranti's unique experience with simulators enables them to look much farther ahead in their

planning and development of operational systems. This is because in designing equipment for training young controllers they have had to anticipate future needs.

It has also given them an intimate under

standing of the controller's problems. And it has increased their ability to undertake study contracts.

Ferranti MINICAP System at the

London

AT C

Centre

This system automates the major part of flight progress strip production, and was

supplied by Ferranti complete with oper ational programs. It performs some of the more routine tasks of Air Traffic Control and so leaves controllers more free to concentrate on making the decisions that can be so vital.

AT C A u t o m a t i o n i n S t a g e s I n AT C , a u t o m a t i o n i s a p r o c e s s o f

the

latest

Ferranti

AT C S y s t e m s

Ferranti were among the world leaders in developing the microminiature digital computer, and their FM1600B is already established as a fast, efficient computer for s h i p b o a r d s y s t e m s i n t h e R o y a l N a v y.

Now It has been chosen for a number of

ATC applications including a simulator at Schipol (Amsterdam) Airport, and another at the College of Air Traffic Control at Hum, Bournemouth.

Ferranti, with all this background of experience and with advanced equipment of proven reliability, are ready to help you s o l v e t h e AT C p r o b l e m s o f t o m o r r o w.

steady accretion so that eventually each part will form a unit of a complete system.

Ferranti systems are designed with capa

Ferranti

Limited,

bility for extension in mind. Cost-effective ness does not stop when the next stage in expansion is reached.

England, RG121RA.

Digital Systems Department, Bracknell,

Berkshire,

FERRANTI

VCf t s ■N •

i*r If

(Ml

• t t t t r

I

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A III

4rir III

ut

O P E R AT I O WA L S Y S T E M S A N D S I M U L A T O R S

I 14

III t«U

Jl

Effects of Heavy Jets on Airport Acceptance Rate Under the new vortex-avoidance procedures which hove been set up since the commissioning of the Boeing 747, a dual separation standard is now in effect in the USA. The new standard specifies that at least two minutes separa

tion must be used, when any other type of aircraft will fol low directly behind a heavy jet. The old radar separation

by Tirey K. Vickers

C) Rearrangement to group entries in

chains

of

at

least

two

of the some type Entry number Aircraft type 1 3 4 5 2 6 7 8 12 9 10 11 13 14

standard of three nautical miles is still in use between all

H H H H L L L H H L L L L H

other combinations of aircraft. The new regulation defines a "heavy jet" as an aircraft capable of takeoff at weights of 300,000 pounds or more. At approach speeds up to 150 knots, G separation of five nautical miles fulfils the two-minute requirement.

Recently on analysis was completed in order to de termine the losses in airport capacity which could be ex

ASSUMPTiOtj; EXCEPT TYPE

5

3

MILES

MILES

AIRCRAFT

MINIMUM

REQUIRED

S E PA R AT I O N

BY

FOLLOWING

A

ANY

OTHER

H E AV Y

JET

pected with different percentages of heavy jets in the land ing sequence.

In this exercise, it was assumed that a single runway is

used exclusively for landings, and that the approach speeds of the heavy jets and the other types of aircraft were simi-

lar.Three different sequencing strategies were investigated, as follows:

A) The controller simply sequences the aircraft as they appear, on a purely random (first-come, first-served) basis.

J

I

I

]

I

1

20

30

40

50

60

70

P E R C E N TA G E

OF

H E AV Y

JETS

IN

I

\

80

90

1 100

MIX

B) The controller deliberately rearranges the sequence to obtain as many HL pairs (as heavy jet followed by a

lighter aircraft) as possible. As this "strategy" maximizes the number of long intervals required, it represents the

Figure 1 Effect of sequencing procedure on acceptance rate using 3-5 mile separation

worst-case-condition for any particular traffic mix.

C) The controller deliberately rearranges the sequence to avoid sequencing on isolated aircraft of either type be tween two aircraft of the opposite type. Instead, he

arranges to pair any isolated aircraft with at least one other aircraft of the same type before trailing it with the

next aircraft of the opposite type. The object of this strategy is to reduce the number of HL pairs — and thus the number of long intervals required — for any t r a f fi c m i x .

Examples of the three strategies are listed below, for

a 50% mix of heavy jets in a typical sequence.

A ) R a n d o m ( fi r s t - c o m e , fi r s t - s e r v e d ) Entry number Aircraft type 1

2

3

4

5

6

7

8

9

10

11

12

13

14

H L H H H L L H L L L H H L

B) Rearrangement to obtain maximum number of HL pairs Aircraft type 1 2 3 6 4 7 5 9 8 1 0 1 2 11 1 3 1 4 L

H

L

H

L

H

L

H

ous mixes, using each of the three strategies. In this Figure,

it is assumed that the separation is perfect — exactly 5 miles for HL pairs and exactly 3 miles for HH, LL, and LH pairs.

It will be noted that, regardless of which strategy is used, the acceptance rate decreases as the percentage of heavy jets increases from 0% to 50%. However, with a fur ther increase in the percentage of heavy jets beyond the 50% mix point, the acceptance rate rises again because with an increasing majority of heavy jets, there are less and less of the lighter aircraft available to make the HL pairs which require the longer intervals.

Curve A shows the results of purely random first-come, first served sequencing conditions. The acceptance rate of a 50% mix is about 86% of the normal rate without heavy jets.

Curve B shows that a controller who tries hard enough

could reduce the landing rate down to 75% of normal, by creating Ihe maximum number of HL pairs. Perhaps the only operational reason for doing this would be to open up a number of approach intervals, to clear out a backlog

of departures on an intersecting runway.

Curve C shows that a controller could gain up to 4% of

Entry number H

Figure 1 shows the variation in acceptance rates which could be expected from very large traffic samples of vari

L

H

L

H

L

capacity with a 25% or 75% mix of heavy jets, by group ing his aircraft in pairs of the same type, instead of allowing a single HorL aircraft to be sequenced be3

tween aircraft of the opposite type. However, with a 50% mix to work with, there would be fewer opportunities for

assumption; EXCEPT

5

3

miles

MILES

minimum

REQUIRED

BY

separation ANY

OTHER

T Y P E A I R C R A F T F O L L O W I N G A H E A V Y J E T;

him to make such changes.

1 - M I L E AV E R A G E

BUFFER ADDED

IN

EACH

CASE

70

80

There are certain disadvantages in rearranging the normal first-come first-served order. As may be apparent

from comparing the entry numbers in the A, B, and C ex amples given earlier in this report, any re-arrangement of the natural entry order tends to produce an inequitable distribution of delay among the aircraft concerned.

Although a judicious rearrangement of the first-come firstserved order will allow a particular string of aircraft to be landed in a shorter overall period of time, certain indivi dual aircraft which get shifted may be penalized by land

20

ing later than they would hove, if a first-come first-served

order had been followed instead. In many cases there

would be a higher controller workload involved in rear ranging the string.

Figure 1 provides an indication of the theoretical chan ges which occur as certain factors are changed, assuming

that the spacing procedure is perfect and that no errors

exist in the approach system. However, during IFR condi tions, in the real world, the controller usually aims for some additional separation above the minimum, just to

make sure that he will always have enough, in spite of variations in winds and airspeeds, as well as lags in com munications or in pilot and aircraft response.

Therefore, to bring the results of this study closer to cur rent practice, the situation has also been studied with the additional assumption that the radar arrival controller allows an extra mile of separation between all aircraft; so the average separation of HL pairs is 6 miles instead of 5, and for HH, LL, and LH pairs is 4 miles instead of 3.

The results are shown in Figure 2. Here it will be noted that the penalties in all case are slightly less, on a per

30

40

P E R C E N TA G E

50 OF

60

H E AV Y

JETS

IN

90

MIX

Figure 2 Effect of sequencing procedure on acceptance rate using 4-6 miles separation

3. As the percentage of heavy jets in the traffic mix con tinues to increase beyond the 50% point the accept ance rate will start to increase again.

4. Controllers can gain back some of the theoretical loss in capacity by grouping aircraft of the same type where possible, rather than by alternating the types of aircraft in the sequence.

5. If the future ATC system ever reaches a stage where landing sequences can be replanned thirty minutes or more in advance, and aircraft speeds can be adjusted enroute in order for each aircraft to enter the common

approach path in order desired by ATC, then more use can be made of this principle.

centage basis. It is wise to point out, however, that

6. There is a practical limit to the amount of grouping pos

slightly over 30 landings per hour, as against slightly over

sible, as any rearrangement tends to produce an in equitable distribution of delays.

the 100% point is also lower — in Figure 2 it represents 40 landings per hour in Figure 1.

The conclusions of this little study should be of interest to airport designers as well as air traffic controllers, and may be summarized as follows:

1. Aircraft acceptance rates can be expected to decrease initially, as the percentage of heavy jets increases.

2. The maximum decrease will occur when the percentage of heavy jets reaches 50% of the traffic mix. At this

point, the acceptance rate will be about 90% of normal.

7. Although not discussed in the foregoing paragraphs, the same principles apply also to the sequencing of

departures. Here it may be much easier to rearrange the sequence of aircraft to obtain longer strings of the same type (and thus reduce the number of HL pairs with

the longer separations they require); as all the potential members of the group normally will be located within a relatively small area on the airport, rather than be ing strung out over a number of miles of airspace.

O n e D e c a d e I FAT C A 10th Annual Conference

Third — Seventh May, 1971

Athens, Royal Olympic Hotel 4

winning ticket I ' i i h c d l d b l e H o e i n c j u . B r d i u l - n e w. L i ' d c i e r s o f t h e j e t - a g e .

W e fl u I t w n i o n c i l l o i i r i n t e r y i d t i o u d l r o u t e s . T o U . S . . \ . , Cdiuuld. ICuroiye. Middle I'Jdst and .Africa. At OOO smiles j i e r fl o u r . ( ) u h o a r d y o u ' l l J i n d t h e l e d r m t l i o f G r e e c e . W a r m smiles. Warm service. .After all lee're the airline of Greece.

Gur t iehets are u-inners every time.

we

fl y t h e O i y m p i c t i c k e t

a

t

tt

tmf

A

add

warmth

WHAKATOPA — The Hovering Helper

by R. A. Soar* Although crash/fire facilities ore not normally the direct concern of Air Traffic controllers, they ore of great interest,

and it tended to ground in thin mud or sand. When this

and although one hopes that they will never have to be

was too great for the thrust available from the propellor

used at all, the knowledge that there is an efficient service is reassuring. A recent innovation at Auckland International

to

Airport may, therefore, be of particular interest to those

happened the tracks could get no purchase and the friction overcome.

During 1969, a second-hand SRN 6 was purchased from the British Hovercraft Corporation. The craft was converted

whose airfield is bounded by water or marshy terrain.

to its new role by Air New Zealand Engineering to speci

On 27 September 1969, an SRN 6 Hovercraft was com missioned at Auckland to be added to the airport crash/ fire facilities as a rapid initial rescue unit. Auckland Inter national Airport is on the shores of the Monukau Harbour, a 163 square mile area, which, at low tide, consists of large

fications drawn up by the Civil Aviation Division of the New Zealand Ministry of Transport in conjunction with the

areas of sand and mud banks interlaced with channels,

"Pilots" for the Hovercraft were drawn from the airport crash/fire department and were given a short course in light

varying from a few inches in depth to several fathoms.

These bonks ore completely covered at high tide.

The problem of reaching an aircraft which has crashed

British Hovercraft Corporation. The project was jointly financed by the Auckland Regional Authority and the Government.

aircraft to establish their suitability and to initiate them into the mechanics of flight. They were given 80-100 hours

in the Harbour has concerned the authorities since the air

training in the Hovercraft before qualifying and will re

port was planned, and although the Hovercraft was obvi ously ideal, a cheaper solution was sought. Zodiac dinghies,

quire 5 hours per month to maintain a satisfactory stan

powered by outboard motors were used, but at low tide

tures covering the SRN 6 and the Rolls Royce Gnome

their scope was limited, access by water was circuitous and launching relatively time-consuming. An improvement was sought by the purchase of the Muskeg Bombardier, an

engine. Maritime Law, Navigation, Radar. Flight Training — Phase I, Control of the Craft; Phase II, Radio Navigation;

amphibious tracked vehicle of Canadian origin. It was, however, found to be rather slow, particularly in the water

dard. Training took place in four stages — Ground Lec

Phase ill. Radar.

Reaction time from alerting to vehicle readiness is estimated to be 2 minutes and the speed of transit is 50

■ New Zealand Air Traffic Control Association.

Auckland International Airport on the shores of Manukau Harbour

16

(Photo: Whites Aviation Limited)

Greek and Austrian Associations elect new Board o f O f fi c e r s The ATCA of Greece held elections in July, 1970, and the new administrative council now consists of

Costas Theodoropolous President G e o r g e K o r a g e o r g i s Vi c e P r e s i d e n t Basil Chakiamis

General Secretary

Costas Peristerakis

Treasurer

Sotirios Sotiriades

Member

Elias Petroulias

Member

George Aslanides

Member

In June, 1970, the Austrian Air Traffic Controllers As sociation held their Annual Conference in Vienna and

SRN 6 Hovercraft converted to rescue vehicle

elected the following Officers Ladislaus Sloup Alfred Nogy

President 1. Vice President

Helmuth Kihr

m.p.h. in normal conditions. Speed would, of course, hove to be reduced in poor weather and at night, although it would still be high compared with conventional vehicles.

The SRN 6 is undoubtedly a great asset to Auckland International Airport crosh/fire facilities, and is almost cer tainly unique at present, although the interest being shown by overseas airports in similar situations indicates that these vehicles could become standard equipment.

2. Vice President General Secretary

Christian Eigl Helmut Erkinger

Deputy Secretary

Konrod Hirsch

Treasurer

Karl Bohm

Deputy Treasurer

Erich Schyr

M e m b e r, Professional Matters

Othmar Kubes

Member, Public Relations Member, Social Matters

Gerhard Posch

THE CONTROLLER congratulates these Officers and wishes them every success in their new assignment.

Specifications Standard SRN 6 powered by a Bristol Siddeley marine gnome gas turbine.

Payload: 9 tons or 50 people in emergency with raft for 150 more Fire foam capability: 1000 gals per minute for 20 minutes or 2000 g.p.m. for 10

minutes. Foam gun has range of 150 ft.

Auxiliary equipment: 6X25 man life rafts

A pyrene foam producing unit A 250 g.p.m. portable water pump.

4 dry chemical extinguishers A rescue cutting saw

Union of Soviet Socialist Republics joins ICAO as the 120th Member State The Government of the Union of Soviet Socialist Re

publics gave notice of its adherence to the Convention on I n t e r n a t i o n a l C i v i l Av i a t i o n o n 1 5 t h O c t o b e r a n d t h u s b e

came an ICAO Contracting State as of 14th November, 1970.

Aeroflot, the Soviet civil aviation orgonzotion, has 500,000 kilometres of air routes and presently serves 3,500 cities. In the USSR itself, Aeroflot has a network of 2,500 airlines.

18 and 36 inch bolt cutters

A pinch bar A crow bar

2 shovels for use in shallow water or for throwing sand onto magnesium fires 2 large and 2 small axes

2 foam producing branch pipes for use with a secondary fire fighting system 4X75 ft. of 2V4 inch, hose A ladder

ICAO appoints new Secretary General The Governing Council of the International Civil Avia

tion Organization has appointed Dr. Assad Kotaite its chief executive officer for a three-year term that began on 1st August, 1970. He succeeds Mr. B. T. Twight of the Nether lands. Dr. Kotaite, as the new Secretary General, will be responsible for the administration of ICAO under the guidance of its 27-member Coucii.

An Elkhart nozzle

2 sets of breathing apparatus 2 searchlights

A n n u a l E l e c t i o n o f O f fi c e r s f o r I C A O C o u n c i l

Radar

in November 1970, the Governing Council of ICAO has elected its Officers for the annual period 1970/1971. Those elected were: First Vice President, M. Agesilos of Prance; Second Vice President, L. Vosquez Canet of Guatemala; Third Vice President, K. Barkah of Indonesia. President Walter Binaghi of Argentina is elected every three years

HP and VHP radio

and

2 first aid kits 6 stretchers 2 asbestos blankets

2 vapourising liquid 31 b fire extinguishers 100 ft. of cone matting for use on soft ground

continues

in

o f fi c e .

ICAO

17

Civil/Military Co-ordination a n d U n i fi c a t i o n o f A i r Tr a f fi c S e r v i c e s The following Working Paper has been prepared by the G e r m a n A i r T r a f fi c C o n t r o l l e r s A s s o c i a t i o n a n d s u b m i t t e d

to the Belgrade and Montreal IFATCA Conferences. At the request of numerous readers we are now publishing this interesting and timely Paper in "The Controller",

An analysis of the basic factors The utilization of airspace by both military and civil air traffic confronts all units concerned with handling of air traffic, with serious problems.

The Air Traffic Services generally assume, that 1. traffic is known,

try. Therefore recommendations of this study must offer a

range of possibilities to meet the whole variety of require ments.

Composition and categories of Military Air Traffic

2. its behaviour is predictable and 3. that it is controllable.

For Military Air Traffic, these conditions apply only to

a very limited degree. When this type of air traffic operates

Military traffic can be iudged with regard to equipment used as well as to mission types flown.

Military aircraft are solely equipped to meet tactical

within the same airspace as Civil Air Traffic, its limitations

requirements. Due to this fact they cannot be fitted into every air traffic control system. Radio equipment allows

and characteristics reduce possibilities of safeguarding civil

the use of a limited number of frequencies in certain bands

air traffic considerably.

The aim of this survey should be to offer recommenda tions for the common utilization of airspace and for proce dures of co-operation and unification of Air Traffic Ser vices, and outline the special characteristics of military traf fic. The characteristics and procedures of civil air traffic are considered to be generally known.

only. Due to their navigational equipment military aircraft are unable to use all parts of the airspace i. e. certain air

ways etc., also limited endurance does not permit extensive

holding or rerouting. Additionally, the lack of back-up sys tems comparable to those of civil aircraft increases the

possibility of emergencies due to failures of primary sys

tems and therefore tends to congest capacities of air traf fi c s e r v i c e s .

The types of missions flown by military aircraft might be

Factors governing the density of air traffic

subdivided into the following categories:

The importance of military traffic as a part of air traffic of a specific country depends on various factors, such as:

a) Transport Flights

1. Political situation

These missions will normally be flown with aircraft,

(Sovereignty, neutrality, membership to military alli ances, relations to neighbouring countries, political

whose performances and equipment are similar to those

structure of the country etc.);

operate along airways and can therefore be fitted into

2. Military situation (degree of threat — by other countries, intended opera tion of the air force, strength of forces, number of mili tary aircraft available, structure of air forces etc.);

of civilian aircraft. Most flights of this category will air traffic control systems. Although troop dropping and

supply dropping missions are considered to be trans port traffic as well, these missions can not be controlled

by air traffic services except during that part of the flight, when they constitute aerodrome traffic.

3. Geography

(size and shape of the country, geographical situation; Topography of the surface insofar as it has any influ ence on the conduct of air traffic industrial areas, un

populated and desert areas etc.); 4. Economical situation

(as it determines the density of air traffic and the degree to which a country depends on its existence and it governs the possibility to solve air traffic problems with advanced technology).

Considering all these facts, it becomes clear that solu tions of air traffic problems can vary from country to coun 18

b) Low Level Missions

Military aircraft operating at low altitudes normally navigate by visual reference to the ground or by air borne radar. Due to their extreme low altitudes they will

not be within radar and radio coverage of air traffic control agencies except when constituting aerodrome

traffic. It must be considered additionally that these

flights hove only limited chances for collision avoiding actions since the attention of pilots must be concentrat

ed to an extremely high degree in execution of this type of mission.

c) Navigational Training Fiights not conducted as Low Level Missions

These flights are carried out in all weather conditions, the routing depends on tactical requirements and is determined by the navigational capabilities of the air craft, for example, turning points are used, which can be identified by airborne radar. The limited endurance necessitates a precise planning and limits possibilities of unexpected re-routing or level changes. In m.any countries these flights are monitored by radar, as navi gational errors may result in the loss of aircraft or

provoke political incidents owing to the geographical and political situation of countries concerned. d) High/Low operations There is a high number of missions flown where the flight levels change from high to low or vice versa one or more times. Additional to the problems resulting from these changes, para's, b. and c. apply. e) Air Defence Training Missions

These flights will be conducted in all weather conditions in order to practise intercept procedures. Intercepts will be executed at all levels and all speeds possible. A spe cial factor is the large airspace required by supersonic missions, which is in the range of 100 NM^ or more. Dur

ing certain phases of these flights avoiding actions are limited.

of about 40 NM^ horizontally and 30,000 ft. vertically.

Depending upon training methods and proficiency of aircrews, radar assistance must be provided.

General considerations on provision of ATS to military traffic Control of military air traffic is generally very compli cated. It frequently necessitates the employment of radar sites and is normally beyond the scope of procedural me thods, and conventional control. Military air traffic de mands a high flexibility of air traffic control systems in order to meet its special requirements at any time. This results in undue strain on the capacity of these systems,

which are further stressed by the fast build up of traffic concentrations of military flights in various sectors of the area of responsibility.

Navigational equipment of military aircraft is designed to enable the aircraft to perform its tactical operation.

Therefore, most military aircraft can use only those navi gational aids which are operated by military authorities and are positioned in accordance with special require ments. Consequently these aircraft will operate along cer

tain routes, which do not necessarily coincide with those of civil air traffic. Many aircraft are equipped with naviga tional equipment for departures and approaches only,since their intended combat operation does not include route navigation, other aircraft are equipped to be controlled by automatic systems via data-link.

f) Air Defence Combat Operations These flights — Battle Flights or Hot Scrambles — are executed for the benefit of national security, and mili

tary requirements only will be considered. g) Exercises

Major exercises normally involve the whole airspace of one or more countries, and are preplanned in detail.

Due to these facts military aircraft are to a high degree dependent, for area navigation, on the assistance received from ground radar stations. The provision of navigational assistance is of prime importance when supporting military a i r t r a f fi c .

The following factors should be noted in particular: a) Range and Endurance

These miissions will be conducted at medium to high

Military aircraft normally have a shorter endurance than civil aircraft. Therefore military pilots are forced to adhere strictly to the planned flight as fuel for addi tional flying time is not carried. Changes of the intended flight caused by weather, delay of air traffic clearances, and other traffic situations, confront pilots with ex treme difficulties. Pilots may be forced to deviate from their flight plan on short notice, or may find themselves in a position unable to accept reroutings or other in

altitudes. The refuelling area can be of different dimen

structions by air traffic services.

These details are generally available well in advance in order to initiate airspace reservations or necessary restrictions for the remainder of air traffic. However,

short term alterations are possible and will be beyond the influence of civil air traffic services.

h) Air Refuelling

sions but will normally extend 3000-4000 ft. vertically.

Flights to and from that area will conform with condi tions as outlined under a. b. c. and d. — Separation

within the refuelling area will be provided and monitor ed by the tanker. Radar monitoring by ground stations, however, will normally be necessary.

i) Training Flights Training missions of aviation — and weapon schools

operate in all weather conditions. Some of these flights not conducted in accordance with details outlined in

para's, a.-h., will be formation flying, exercises to handle aircraft under extreme conditions, simulated emergen

cies, aerobatics etc. These operations require airspace

b) Equipment with back-up systems

Apart from transport aircraft, military aircraft are rare ly equipped with spare systems. Failure of a main sys tem may therefore easily result in an emergency situa tion, which often can be overcome by the help of on

experienced ground unit only. Actions of ground sta tions include advising of alternate procedures, instruc tion to perform certain emergency procedures, inter cepting distress aircraft by shepherd aircraft etc. Seri ous problems in this connection ore oxygen failures and failures of navigational systems, which in many cases are noted by groundstations who are controlling the air craft before the pilot himself is aware of the situation.

19

c) Changing of Mission Orders For tactical reasons orders can be changed in flight, and often by outside influence, which has little know ledge of the traffic situations, control and technical problems etc. This creates undue stress on the flexibility of a traffic system. The flexibility will also be stressed by changing landing capacities of military aerodromes.

Diversions because of weather, closing of a field due to

military or emergency reasons, such as operation of jetbarriers for example, are normal situations in the every day life of military aviation.

d) High and Low Missions

Flights, generally referred to as high-low-high mis sions, have the requirements as mentioned under b. and

c. relative to the proportion of high and low level parts

in the mission concerned. Control will be complicated because of the various altitude changes, most of which can be executed with radar assistance only, and due to the fact that one or more parts of the operation will be beyond radar and radio range of air traffic services.

Holding these flights is nearly impossible without im pairing the result and safety of the mission. e) Air Defence Training Missions

These flights are conducted under the responsibility of

Requirements of the different mission types OS listed above

air defence units. Control by air traffic services is limit

ed to the departure and approach part of the flight.

Military radar units normally provide these flights with anti-collision warnings. The safety requirements of this

a) Transport Flights

category can only be fully complied with by airspace reservations.

Most aircraft used in Transport Operations operate in

a similar way to civil airlines and because of this they normally use airways and can be treated as civil air traffic. During certain military exercises, transport air craft will operate in like fashion to that mentioned in b. — below, while others will require direct routing with ground radar assistance. b) Low Level Missions Due to the characteristics of the mission profile, low

These missions cannot be controlled by air traffic ser

vices units. Safety requirements of other traffic will play a very small role against the task of the operation. g) Exercises

For tactical reasons and because of the complex plan ning and logistics of such exercises, possibilities of in

fluence by nonmilitary sources are limited. Necessary

level flights normally are beyond control possibilities of

information however can be gained through co-ordina

air traffic services. Confliction hazards arise with parti

tion staffs and by liaison-officers attached to air traffic

cipants of General Aviation. Special attention must be

units. Military air traffic units frequently support such exercises by providing radar services and acting as co

paid to the limited capability of low level missions to

avoid conflicting traffic by evasive actions. This fact also limits the possibility to comply with General Rules as far as right of way rules are concerned. To protect

military and civil aviation, reserved airspaces, special low level areas, and routes should be established,where in certain regulations concerning right of way, altitude restrictions, one-direction traffic etc. will apply. Another special factor to be considered is the dependence of low level operations on weather conditions. A sudden change of weather forces the break-off of missions and requires immediate radar assistance to prevent colli sions until an ATC clearance can be issued. Under these

extreme conditions the compliance with normal regu

lations such as submitting of IFR-flight plans before clearances can be issued or holding in VMC until re ceiving clearances etc. is impossible.

c) Navigational Training Flights These flights need air traffic services to be separated

ordination units between participants. h) Air Refuelling

Receiver aircraft can be controlled when approaching the tanker, or departing from it, depending on the mis

sion type, aircraft will fly in accordance with para's, a.-d. The refuelling manoeuvre should be conducted within a reserved airspace, preferrably under radar control. The fact, that a refuelling formation is unable

to perform any evasive actions deserves special con sideration.

i) Training Flights

These flights can be controlled by air traffic services during departure and approach phases. The remainder of the flight can only be monitored by radar for the

provision of collision warnings, considering the some

times reduced possibilities of evasion manoeuvres.Training Flights can be conducted in accordance with a.-e.

f r o m e a c h o t h e r a s w e l l a s f r o m c i v i l a i r t r a f fi c . F o r

and g.-h. For general aviation training, however, air

several reasons such as weather, flight restrictions at

space reservation seems to be the most suitable method

certain times, and for special training purposes, flights of this category have to.be conducted in substantial numbers simultaneously. This leads to an irregular stress on air traffic services capacity and results in an ex

20

f) Air Defence Combat Missions

to meet the safety requirements of this category. Gene rally, the characteristics of training operations are de

fined by the high density of traffic, training standards

and many simulated and real emergencies. Ground

treme strain on the system. This category requires a

units are expected to support the training by certain

sufficient capacity reserve and flexibility of the air traf

reactions in unusual situations as often occur in aviation

fic services.

training.

Military ATS units Air forces may operate the following units to control military air traffic:

1. Military ATS units: They provide aerodrome control, GCA-service, approach and en-route control.

2. Air Defence Stations: They control military traffic under certain tactical aspects, though other flights might be accepted for training purposes.

Possible solutions

to the CIvil/Mllltary Coordination Problem There cannot be a general solution to the problem of co-operation as there are a variety of problems due to dif

ferent requirements of air traffic participants and different

conditions in various countries. This paper can only high light major possibilities which either alone, or combined, con help to overcome the specific problems of countries concerned.

3. Command posts; temporarily installed for the control of special missions.

4. Operation Centres; delegating control authority and monitoring it without using its own control capacity.

Military ATS units are normally manned by Armed For ces controllers. Units and controllers can therefore be di

rected by command. This is one of the reasons for the flexi

bility with which these units meet the requirements of the forces. Additionally, personnel are trained to assess tac tical requirements and to implement them when control ling aircraft. As military units these air traffic services are in a position to gain information about military flight ope rations and to influence such plans if necessary. These cir cumstances favour a foreseeing, expeditious control of

military traffic. Basically working procedures do not differ from those of civil units. The use of radar, however, and

the required flexibility, has lead to a decentralization of control functions in order to reduce the workload of the

individual controller. Another feature is the tendency of military units to differentiate between planning and ex ecutive functions. Additional to recommendations of ICAO

and national laws, military units must consider special mili

tary regulations. Exceptional laws, which favour military aviation in certain aspects, help these units to meet the special requirements of this traffic.

Air defence stations operate exclusively to meet tac tical necessities: Air traffic control regulations will there fore be considered in a particular manner, i. e. as far as

these regulations do not hinder tactical operations they will be complied with. The possibility of centralized ope ration is another characteristic of modern air defence sys tems. Control authority con be delegated to one operation center while the executive work is done by another. Co operation with air traffic services in this mode of operation of air defence becomes complicated, as the jurisdiction of

Reservation of Airspace The easiest way to separate military from civil traffic is to keep one or the other within a specially reserved area.

For which category airspace reservations will be mode, depends on the quantity of traffic and its intentions, and generally airspace reservations will be mode for military traffic. The use of this airspace does not normally strain

the capacity of air traffic services as responsibility for this airspace should be delegated to users.

Advantages

Conflicting air traffic is geographically separated;

Co-ordination requirements ore limited to exceptional situations;

Traffic within reserved airspace can operate without restriction;

Tactical requirements for certain categories of military operations ore met.

Disadvantages

Airspace for the use of all participants will be reduced by reservations:

The stress on the safety minimizes the aspect of expe dition, since other traffic must be vectored around these a r e a s ;

— Uneconomical use of airspace; Reduced flexibility, because long reservations limit pos sibilities to meet special situations.

control may rest with units not controlling the aircraft.

Therefore, military units controlling air traffic do so under different aspects, whereby the tactical requirements play a major role. There ore only limited opportunities for non-military influence to be exerted. Because of the differ ing commitments of such units, they consider co-operation with Civil Air Traffic Services in a different manner. Mili

tary ATS units have a special attitude towards co-operation because:

1. their working principles ore similar to those of civil air traffic services, hence

2. they consider co-operation to be essential, and

3. they are capable of exerting influence on military ope ration, because 4. they combine military requirements with air traffic con trol necessities.

Division of military and civil responsibilities according to the division of airspace Certain parts of the airspace will be under the juris diction of civil while other ports are under the control of military units, depending on traffic concentrations and categories in these ports.

Advantages — Clear responsibilities;

Most flights will be controlled by units specifically de signed to meet the requirements of subject flights; — Economical use of airspace;

Compliance with the principle of "unity of control".

21

Disadvantages

This data could be processed via data-link if control

— Airspace must be divided into many small sectors;

units are stationed at different locations.

— Numerous control stations are necessary; — Civil stations must also control military flights crossing their areas, while military units will control civil traffic,

— "Integrated Co-operation", which provides for the uni

fication of military and civil units, thus forming one combined unit for the control of one part of the air space.

flying through military areas; — Two air traffic organizations with identical commit ments must be kept up.

Co-ordinated Co-operation Different

Centres

Two air traffic services units control within the same

Division of military and civil responsibilities according to the category of traffic Military air traffic units control military traffic, while civil units control civil air traffic. If military traffic is con ducted in a similar fashion as civil traffic, (transport flights for example), it could be controlled by civil authorities; vice versa, if certain civil flights deviate from normal pro cedures, like test flights, they could be controlled by mili tary units: the behaviour of a certain flight is the determin ing factor in deciding which unit is responsible for the flight.

Advantages — Each flight is controlled by a unit capable to meet its specific requirements;

— High flexibility of the complete air traffic system; — Most economical use of airspace; — Airspace must be divided into few sectors only.

Disadvantages — More than one station working in the same airspace.

— Traffic situation must be currently co-ordinated between these units.

airspace, while the traffic situation is co-ordinated and

displayed at both stations. This co-ordination is not a pro cedural but a technical problem which can easily be over come. The use of SSR-codes, by which the controlling agency can be identified, will be of great help. The co ordination of control intentions however, is much more difficult. It could be solved by making use of certain air space structures. Considering the fact that civil air traffic,

with the exception of departures and approaches, will navigate along ATS-Routes, military traffic should give way laterally to civil traffic when crossing these routes, or military units must get clearance from civil stations to cross ATS-Routes.

If civil traffic leaves ATS-Routes it should give way to military traffic laterally or civil units must get clearances to deviate from normal routes. If military traffic intends to use an ATS-Route, it comes under jurisdiction of civil air

traffic stations; if civil aircraft intend to operate outside

of ATS-Routes it will be under the responsibility of military

air traffic units. The change of responsibilities does not necessarily demand a frequency change, as radar flight following of subject flights by the unit responsible will be sufficient. Monitoring radio frequencies of partner stations Will favour co-operation, provided workload of controllers permit such procedures.

"Side-by-side"

Centres

Civil and military controllers working the some sector

— Determination of responsibilities is difficult.

should use adjacent control positions and the same traffic

— Co-operation on administration level is essential.

both units, which can be rather difficult because of diffe

Co-operation of civil and military units depending on the kind of solution chosen In reserved airspace, responsibility should rest with users and co-ordination with units, responsible for ad jacent areas can be conducted in accordance with normal air traffic control procedures.

The same procedures will apply, when responsibilities depend on the division of airspace.

If responsibilities depend on the type of traffic and two

display. The proviso is the use of identical sectorization by rent traffic concentrations of military and civil traffic. An advantage of this solution is that data-processing of traffic data over long distances becomes unnecessary.

External co-ordination will be replaced by an internal o n e .

An advantage of co-ordinated co-operation is the fact that civil and military units will remain independent and can therefore meet the requirements of traffic categories under their control to a high extent, while conflicting situa tions with other traffic categories are considerably re duced.

Disadvantages are the increasing technical efforts ne

dures must be developed. Extremely close co-operation is

cessary. Future developments and plans of civil and military air traffic services must be co-ordinated to ovoid diverging

essential and cannot be over-emphasized, especially since the principle of "unity of control" does not apply.

ful co-operation.

Co-operation could be achieved by one of the follov/ing methods:

Integrated Co-operation

or more agencies control the same airspace, new proce

— ''Co-ordinated Co-operation", in which all units con trolling traffic in the same area must, at all times, have

the current traffic situation available and displayed.

22

developments, which could mean a sudden end to success^

Integrated co-operation is the unification of civil and military units to form one combined air traffic services unit.

Procedures of co-operation are similar to those of a co-

ordinated system when using the same control room. The principle of unity of control will be safeguarded. On the other hand, unification of military and civil units may cause

internal problems concerning certain competencies due to the different legal and social status of personnel.

Domination by military components should be rejected because of political and constitutional reasons, similarly the domination by civil components may result in proce dures by which the military components loose the capabili ties that enable them to comply with the tactical require ments of the forces.

The solution to be selected depends on the conditions

of countries concerned, whereby the political situation of the country and the role of the airforce plays a dominating part.

General Conclusions It is the task of air traffic services to enable the safe

and expeditious flow of air traffic, whereby all airspace users will be considered to be of equal importance. The determination of priorities must not result in ignoring the existence of certain categories of traffic. This would be con

trary to the basic attitude of air traffic services and would by no means help to solve any problem. In this connection it is of vital importance to find solutions to civil-military

co-operation problems that meet the requirements of all participants in air traffic. The development of bigger and faster aircraft in civil aviation and the evolution of more

and more complex weapon systems demand modern solu tions. Modern technology, electronics and automation give us new methods but outmoded ideas and principles have yet to be overcome.

Some of the solutions outlined in this paper require, to a certain extent to abandon the principle of "unity of

control", one principle that was unquestionable in earlier times, when controllers had no other means of gaining information about aircraft operating in their airspace than

by talking to them. Today, radar data link and computers can provide controllers with all the data required. Another advantage of this principle was the fact that only traffic

under the control of one controller hod to be considered

by him when planning and controlling the traffic flow, on

advantage which can hardly be called one today when considering the high amount of unknown traffic. This ad vantage must be discarded in favour of effective co-opera tion between military and civil units. It is in fact a question of overcoming organisational problems by modern plan ning methods, other than by employing sophisticated tech niques.

When contemplating military air traffic it is vital to bear in mind that air forces have a certain commitment to

fulfil. For this they employ various command and control systems of which military air traffic services are just one.

It will play an important part amongst these systems as

long as tactical requirements can be implemented with air traffic requirements. If co-operation with civil air traffic services forces this military branch to compromise to the disadvantage of tactical requirements, the flying arms of the forces will seek the assistance of other military systems which are rarely required to co-operate with civil agencies, although their co-operation with military air traffic ser vices is a normal procedure. As to the co-operation with command and control systems, military air traffic services can be of vital importance.

In countries where air forces operate their own ATS organizations, all efforts should be directed towards effi cient and confident co-operation, with the aim of control ling all participants in air traffic for the benefit of safety of modern aviation. Parts of the traffic should be control

led by civil air traffic services, while others are under con trol of military air traffic services. Those flights under con trol of tactical stations should be known to the military air traffic services who will then pass on the information necessary for the establishment and up-dating of traffic displays.

This co-operation depends to a high extent on person nel working in all air traffic services, therefore their basic training in this branch should be identical. Only those men should work in military air traffic services, who have equal qualification to their civil partners. This seems to be the only way of implementing standard procedures which are a prerequisite for effective co-operation at executive and administrative level. Overcoming problems of the future for the benefit of safe and efficient conduct of air traffic

will depend to a large degree on effective and lasting co operation between air traffic agencies — civil and military.

Civil/Military Co-ordination in New Zeaiand

by R. A. Soar* The following report about military/civil air traffic control in New Zealand has kindly been provided by the New Zea land Air Traffic Control Association. It is a very interest

ing supplement to the Working Paper published on the pre ceding pages.

The system of Civil/Military Air Traffic Control in New Zealand is probably unique and it has been interesting to compare it with the recommendations contained in the relevant report submitted to the Montreal Conference.

Within New Zealand Civil/Military Air Traffic Control

airfields, whether military, civil or joint military/civil, ore staffed by Air Traffic Controllers employed by the Civil Aviation Division of the New Zealand Ministry of Trans port.

Whilst serving at RNZAF stations, controllers are com

is closely integrated. The basis for this is that all controlled

missioned as officers in the Royal New Zealand Territorial Air Force, so that the RNZAF has an adequate degree of control over their actions relating to military aircraft and

* New Zealand Air Traffic Control Association

other military matters.

23

It is a prerequisite on recruitment that controllers be

The allocation of Danger Areas, Restricted Areas and

prepared to serve at RNZAF stations and be acceptable to

Special Notamed Exercise Areas in no way differs from

the Air Force for such service.

the normal procedure used in other countries.

Miscellaneous problems such as notams and weather

This organisation simplifies many of the complications which might otherwise hove developed if there had been a separate military ATC service, since there is no difference in training- promotion or salary scales. All the positions at RNZAF stations are graded in the same manner as at civil units. Vacancies at military units are advertised and applied for in the some manner as for vacancies at civil units. The military units are totally integrated in this con cern into the general ATC career structure.

Since the controllers have had the same training and

hold the same ratings at military units as at civil units, they are able to take control of civil flights and so these units have been integrated into the general ATC system.

information are much simplified by the use of common procedures and formats. In the case of notams, all notams for each F.I.R. are issued by the parent A.C.C., whether it be for military or civil airfields, and all whether information is distributed under the civil format.

New Zealand is perhaps lucky in that her military traffic density is not great and the political problems that might

arise in Europe, or elsewhere, are not present due to her isolated geographical position, but it is because of her

internal route structure and geography that an integrated system is necessary and it has proved successful for a con siderable number of years.

Military flights are given full separation from civil

flights, and this applies whatever the mission being carried out, whether it be transport, navigation, transit, strike or local training. The airspace within New Zealand is such that the proportion of uncontrolled airspace, particularly

Book Review AdreBbuch der Deufschen Luff- und Raumfahrt 1970

above Flight Level 130, is relatively small.

German Aerospace DIrecfory, published by Luftfahrtverlag Wal ter Zuerl, 8031 Steinebach, FRO. 704 pages, clothbinding; DM

This fact has come about due to the disposition of the airfields at the centres of population and the interconnect

ing internal civil route structures which makes the alloca tion of military routes or large areas of uncontrolled air space virtually impossible. Although the issuing of clear ances to military aircraft might appear to be difficult, it is in fact relatively rare that it presents insurmountable pro blems; OS, where a procedural clearance is not practicable, the radar coverage is such that in the areas and at the levels at which the problems usually occur, radar separa tion can readily be applied.

Local training flights conducted in areas where they infringe controlled airspace are usually given an area in which to operate which may take any form which provides adequate separation, (e. g. between certain VOR radials bounded as necessary by LELS and/or DME distances).

Separation between military aircraft may be to civil standards, but where requested by the appropriate authori ty this may be reduced to whatever is requested. Where New Zealand military aircraft are concerned the pilot's authority is usually accepted for this reduction of minima.

For circuit work, runway separations and other areas of operation of military aircraft such as interceptions, where civil minima are totally incompatible with military minima, standards are laid down in local unit orders and since

these exercises take place at, or under the control of mili tary units, these procedures present no problems.

If a military aircraft is operating in the circuit at a civil airfield, civil minima are applied unless prior arrange ments have been made, in which case the reduction of civil minima must not involve civil aircraft.

Except in the case of some of the smaller fighter or trainer aircraft the navigational and communications equipment of military aircraft types operating in New Zea land is sufficient to be able to satisfactorily apply separa tion.

28,—.

The 1970 edition of Zuerl's Aerospace Directory has been extended to more than 700 pages. The publishers have set themselves an ambiti ous goal, viz. to publish in one, selfcontoined volume all addresses of the entire PRO aviation community. Listed in the directory ore, inter olio, aviation authorities, aerospace and avionics industry, consortia formed by major European firms, private and official aeronautical associations, research and development centres, airlines and other trans

port enterprises, a compilation of all aircraft registered in the FRO; airports, aerodromes, landing and glider sites, the German AeroClub (DAeC) and General Aviation; aviation press and international aviation organisations. Considerable space is devoted to the German Air Force

including air attachees in the FRG and the North Atlantic Treaty Orga nisation (NATO).

The directory also contains various registers, one of them, the in

dustry branch index (on the "yellow pages") covering almost 100 pages.

For English speaking users of the directory a table with a trans lation of technical terms has been included. This is probably the weak est part of the book, for it contains a number of misprints and ambi guities.

Otherwise Zuerl's Aerospace Directory is a very useful working aid.

Glossary of Aeronautical Definitions

English—German, German—English

By Roderich Cescotti. Third, revised edition — 1969. Published

on behalf of Dr. Ing. H. J. Zetzmann by Honns Reich Verlag, Munchen, F. R. G. 291 pages, snolin-cover; DM 24,—.

The "Glossary of Aeronautical Definitions" was first published in 1956. It is a compilation of definitions which hove been formulated either by the International Civil Aviation Organization or by the British Stan dards institution during the post WWII years. Beyond their immediate

field of application the "British Standards" are of a particular import ance, for they ore based on the recommendations of the Advisory Group for Aeronautical Research and Development (AGARD) which, being a group of consultants for research and development in the field of air and space aviation, deals with all related problems which are common to the NATO partners.

In its new edition the "Aeronautical Definitions" have been revised to refiect the latest available versions of ICAO and British Standards definitions. The presentation of the material has been streamlined and the total volume, as compared with the first edition, has been increased from 3540 to 4140 entries.

In the case of those whose equipment is limited in the navigational sphere, a combination of a D. R. Flight Plan and the liberal use of radar usually suffices since the type of exercise undertaken by these types in controlled air

In general, this dictionary is well edited and will be of particular use to those aviation R&D staff, ATS authorities. Air Traffic Controllers, members of aviation industry etc. who are working in a bilingual Eng lish German environment. There are, however, a few inaccuracies in translation (e.g. 1194-Dutch Roll "Holldndische Rolle"), which would

space rarely causes them to go out of radar coverage.

merit

24

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Crompton Works, Chelmsford, CM1 3BN, England Telephone: Chelmsford (0245) 67111 .Telex: 99108 TWO MORE AIR TRAFFIC CONTROL RADARS FROM THE S600 SERIES