IFATCA - The Controller - January/March 1971 by IFATCA

I FATCA JOURNAL OF AIR TRAFFIC CONTROL

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IFATCA JOURNAL OF AIR TRAFFIC CONTROL

THE CONTROLLER Frankfurt am Main, January/March 1971

Volume 10 ·No. 1

Publisher: International Federation of Air Traffic Con· trollers' Associations, S. C. II; 6 Frankfurt am Main N.O. 14, Bornheimer Landwehr 570. Officers of IFATCA: A. Field, O.B.E., President; J. R. Campbell, First Vice President; G. Atterholm, Second Vice President; G. W. Monk, Executive Secretary; H. Guddot, Honorary Secretary; J. Gubelmonn, Trea· surer; W. H. Endlich, Editor. Editor: Walter H. Endlich, 3, rue Roosendael, Bruxelles-Forest, Belgique Telephone: 456248 Publishing Company, Production and Advertising Sales Office: Verlog W. Kramer & Co., 6 Frankfurt am Main N014, Bornheimer Landwehr 57a, Phone 434325,492169, Frankfurter Bank, No. 3-03333-9. Rote Card Nr. 2. Printed by: W.Kramer&Co., 6 Frankfurt am Main N014, Bornheimer Landwehr 57a. Subscription Rate: OM 8,- per annum (in Germany). Contributors are expressing their personal points of view and opinions, which must not necessarily coincida with those of the International Federation of Air Traffic Controllers' Associations (IFATCA). IFATCA does not assume responsibility for statements made and opinions expressed, it does only accept re· sponsibility for publishing these contributions. Contributions ore welcome as ore commants and criti· cism. No payment can be made for manuscripts submitted for publication in •The Controller•. The Editor reserves the. right to m_ake any. ed!torial changes in manuscripts, which ha believes will improve the material without altering the intended meaning. Written permission by the Editor is necessary for re· printing any port of this Journal.

Advertisers in this Issue: AEG-Telefunken (l); Borg/Worner Controls Ltd. (Inside Cover); Ferranti Ltd. (Inside Back Cover); Marconi Radar Systems Ltd. (2, 15); Olympic Airways (11); Selenia S.p.A. (Back Cover).

CONTENTS Integrated Flight Path Control and Surveillance of VTOL Operations ......................... . H.P. Ruffell Smith and T. K. Vickers

An Appraisal of ATC Automation ....................... · · J. Grambart

1971 CATCA Convention

The Operational Plan for the Maastricht Upper Area Control Centre ...................... · .. · · · · · ·

A Description of the Technical Features of the Maastricht Upper Area Control Centre Automatic Data Processing and Display (MADAP) System ...................... · ·. · · · · · · · · · · · · · · ·

letters to the Editor· ........................ · · · · · · · · · · · · · ·

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

Picture Credit: EUROCONTROL (16, 19, 21, 22, 23, 24, 25, 26); Vickers (5, 6, 7, 9).

Integrated Flight Path Control and Surveillance for VTOL Operations H.P. Ruffell Smith and T. K. Vickers

Figure 1 Perspective view of proposed VTOL landing and takeoff profiles for congested urban areas.

This paper was presented at the Joint Symposium on Environmental Effects on VTOL Designs, Arlington, Texas, November 1970. It postulates a number of system concepts for the navigation and traffic control of the types of VTOL commercial transport aircraft which may be available beginning around 1980. The constraints imposed by noise, G forces and turbulent wakes on terminal area flight paths, approach profiles and V-port capacity are described. Several concepts are summarized to meet the requirements of en route navigation, approach guidance, air traffic control and approach monitoring of commercial VTOL operations.

In terms of flight time, fuel and air traffic capacity, however, vertical descents and climbs of the type described above would be costly, and would not be employed except as a matter of necessity in order to avoid unnecessary urban noise. Wherever approach or climb-out can be made over a non-noise-sensitive area, such as a river or harbor, it is expected that flight profiles would be modified to take advantage of this for the final descent or initial climb gradient, with only a very short vertical segment to or from the landing pad itself.

V-Port Design

Noise Contour Effects Compared with conventional fixed-wing aircraft, VTOL aircraft of similar capacity are expected to be relatively noisy vehicles as far as the radius of the objectional noise contour around the aircraft itself is concerned. The goal which is strived for, in future VTOL designs, is to limit the 90 PNDB noise contour to a radius of 1,500 ft. from the aircraft. The paradox on which is planned future hopes for bringing VTOL service into urban areas is based on the idea of keeping the footprint area of this noise contour at a minimum by making approach at an altitude of somewhat higher than 1,500 ft. and then transitioning to a vertical descent to the landing pad. As shown in Figure 1, this type of approach profile theoretically should be able to confine the objectionable noise contours to a 3,000 ft. diameter circle around the pad. A similar profile will be used on departure, with a vertical climb to an altitude where transition to forward flight at an altitude of slightly more than 1,500 ft. can be completed before the aircraft leaves the boundary of the 3,000 ft. diameter circle. It is difficult to imagine that precise vertical descents and climbs to and from such altitudes can be accomplished manually, at least in the present state of the art. Therefore, a means of automatic guidance and flight path control will need to be developed for operations of this type. Ultimately, advances in technology may make such profiles feasible. 4

The requirement for a 90 DB noise contour limit of 1,500 ft. from the point of touchdown dictates a surface area with a diameter of 3,000 ft. for a single pad V-port. However, for economical utilization within an urban area, it has been estimated that an urban V-port should have the capacity to handle some 30 million passengers per year. This presupposes two pads in use with one spare for emergencies. Different estimates have been given for the safe distance between pad centres, varying from 600 ft. to 1,000 ft. The minimum area would be some 30 acres and might have the shape shown in Figure 2. The size may seem large to some people who had hoped that VTOL would entirely solve the airport real estate problem. However, with the ancillary requirements for aircraft maintenance, gate positions, passenger handling, car parks and other essential services, it appears possible that the ground area needed for the various airport functions of a 3-pad V-port may nearly equal the area required for noise abatement.

Air Traffic Control Considerations To obtain the best cost-effectiveness ratio it seems axiomatic that a traffic control system to be used expressly for VTOL should be designed around the characteristics of such a vehicle. However, as future VTOL traffic will utilize

BOUNDARY OF RESTRICTED LAND USE (90 PNDB CONTOURS)

1500'R

750'

1500'R

'1 a: 0

Figure 2 Space required for 3-Pad V-Port.

certain routes and altitudes in common with conventional (CTOL) aircraft, provision must also be made for the satisfactory integration of CTOL and VTOL traffic within the common airspace under the jurisdiction of the present ATC system.

The limiting aspects of aircraft noise on the mode of operation in and out of urban V-ports has been described. Conversely, Figure 3 summarizes the effects which could be expected if it were possible to achieve a reduction in the noise levels, through some future technological im-

LOWER NOISE LEVEL

x r--

SMALLER NOISE CONTOUR

--...

LOWER MINIMUM ALTITUDE

i t

LESS INTERFERENCE BETWEEN SUCCESSIVE OPNS.

LESS FLIGHT TIME AT LOW SPEED

j_ HIGHER ACCEPTANCE RA TE

WIDER RANGE OF USEABLE LEVELS

SHORTER VERTICAL PROFILE

EASIER SEPARATION FROM OTHER TRAFFIC

__._

FEWER PADS REQUIRED

LESS FUEL AND ENGINE WEAR

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Figure 3 Possible benefits of achieving a lower noise level for VTOL aircraft.

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TIME IN MINUTES WITH3MILESSEPARATION, TWO 120-KTCTOLAIRCRAFT HAVE 90 SECONDS APPROACH INTERVAL FOR A MAXIMUM THEORETICAL CAPACITY OF 40 ACFTIHR. Figure 4

Space-time graph of CTOL approaches.

provements in the engines, the airframes or the flight control system. The far-reaching effects of such a reduction in noise can result in increased system capacity, higher aircraft utilization, lower operating costs and probably a better choice of V-port sites. Just as with conventional aircraft, block-to-block speed has an important bearing on the direct operating costs of VTOL aircraft. There is no real advantage in operating a

LEGEND

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TIME IN MINUTES AS FINAL DECELERATION ANO VERTICAL DESCENT ARE MAOE BEFORE LANDING, TWO 120-KT VTOL AIRCRAFT MUST HAVE 5 MILES SEPARATION ON APPROACH, TO AVOIO VIOLATION OF 3-MILE RULE AT TOUCHDOWN. RESULTING LANDING INTERVAL= 150SECONDS;MAXIMUM CAPACITY 24 ACFT/HR UNDER THESE RULES. Figure 5

Space-time graph of VTOL approaches.

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VTOL at low speeds, unless by so doing it can obtain a positive benefit by being able to utilize lower clearances from obstructions, lower separation from other traffic lanes or smaller manoeuvring areas for approach and departure - and thus be able to operate with less interference from other traffic than it could at higher speeds. Thus, the special characteristics of the VTOL aircraft - its ability to slow to a hover and make turns of very short radius normally will come into play only in terminal areas. The capacity of the present ATC system is limited by the lack of sufficient independent runways, the lack of sufficient airspace (using today's separation standards) and the amount of ATC workload per aircraft. The traffic capacity of any given traffic lane (such as an airport approach path) is directly proportional to the speed of the vehicles and inversely proportional to the amount of separation between them. To increase traffic capacity, either the flow rate must be increased on any individual path or additional independent paths must be established for simultaneous operation. The accuracy of the navigation system determines how close adjacent lanes can be spaced for independent operation; theoretically, the higher the flyable accuracy of the system, the closer the traffic lanes can be spaced and the more lanes which can be operated simultaneously through a given area. One hope for high aircraft utilization and high efficiency in commercial VTOL operations is for such aircraft to be able to use air space which is not being used by other aircraft. This leads to the requirement for a highly accurate three-dimensional navigation capability to permit the use of pre-defined coded routes which can be referred to easily by pilot and controller, and can be navigated accurately by the pilot or auto-pilot in three dimensions, without outside assistance from the controller. Existing separation standards for IFR operation under radar control are based on distance (normally 3 to 5 miles, depending on the distance from the radar), because radar shows distance relationships directly on the P.P.I. display. For conventional aircraft, the really time-consuming portion of their deceleration takes place when they are on the ground and thus beyond the stage where the 3-mile distance separation standard is still applicable. This principle is shown in Figure 4. For VTOL aircraft, however, which have air speed ranges down to zero, the use of a fixed distance separation standard all the way to touchdown would be very inefficient, as shown in Figure 5. Time to collision versus time for correction are the really important criteria in determining the relative safety of a given operation. For VTOL aircraft, with their wider range of air speeds, time separation would be much more efficient, provided that a suitable readout could be provided for monitoring purposes. Regardless of whether the separation were provided manually by the pilot, automatically by the computer or externally by the controller, the amount of separation which could be used safely between aircraft in trail would have to be largeÂˇ enough to compensate for all the resolution errors and time lags in the separation control loop. This standard would not necessarily be a fixed quantity, but could be adjustable by the ground facility. For example, it might need to be increased during turbulent air conditions. A simple display concept for monitoring time separation is shown in Figure 6; tracking circuits project ahead

POSITION OF TARGET AT TIME t (t +s} (PREDICTED}

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DESIRED TIME SEPARATION"/NTERVAL

= DISTANCE TRAVELLED DURING$

DIRECTION OF TRAFFIC FLOW ....

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Figure 6 Concept for monitoring time separation between aircraft targets on PPI scope.

UNSAFE

of the target the actual distance travelled by the aircraft during the last time increment (where the increment is equal to the minimum time separation standard). If the projected line from aircraft B does not overlap the preceding target (aircraft A), aircraft B will not collide with aircraft A within the next time-frame, assuming that both aircraft will maintain their same relative speeds during this interval. One of the most critical factors limiting the capacity of a V-port could be the problem of wake turbulence, particularly if the type of high-rise profiles shown in Figure 1 are employed. Herein lies an important difference between CTOL and VTOL approach and departure operations. CTOL aircraft use relatively shallow glide and climb angles, so CTOL flight paths to and from a conventional runway normally ore separated longitudinally from each other. Consequently, the interference between arrivals and departures on the same runway is usually limited to the runway occupancy time of the aircraft. As shown in Figure 1, however, the flight paths of VTOL arrivals and departures using the some pod will overlap within the airspace above the pad. This factor may tend to increase the separation requirements between successive VTOL operations in and out of the same or adjacent landing pods. Because of the relatively short effective wingspan of VTOL aircraft (particularly the lift fan-jet types) extremely high downwash velocities will be generated during takeoff and landing. In forward flight, the wake will assume twin vortices resembling those produced by conventional

oi-------

SAFE

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SAFE

TYPICAL PRESENTATION ON PP/ SCOPE

aircraft. These vortices will be propelled downward initially and will drift with theÂˇ wm'd, until they lose their energy and gradually dissipate into the surrounding air. Before close separations can be employed between successive VTOL arrivals and departures from the same pad, considerable research will be required to determine the structure and intensity of the vortices left behind by such vehicles in vertical descent and vertical climb. It is hoped that during these phases of the flight, the relative non-uniformity of the air velocities (and thus the lift distribution) within the wake itself may produce internal shearing effects which will tend to speed up the dissipation of the vortices. As the resulting wake will include the hot efflux from the jet combustors, it might be possible to employ an infra-red sensor at the V-port to determine when a disturbance has either dissipated or cleared the proposed path of the next aircraft. To avoid confliction between inbound and outbound aircraft, without requiring unduly high transition altitudes for either arrivals or departures, it is probable that traffic patterns at any given time would be uni-directional, as shown in Figure 1, in the immediate vicinity of the V-port. With the aircraft characteristics postulated for this study, it is assumed that a V-port with two active pods, using one pod for arrivals and one pod for departures, would be able to accommodate a flow of 48 operations per hour (24 in and 24 out). This rate, limited chiefly by wake turbulence hazards, may be increased later when a satisfactory turbulence sensor is developed, or when

more is known about the intensity and dissipation characteristics of the wakes from powered-lift vehicles in vertical climbs or descents.

En Route Navigation and Guidance The navigation and guidance of VTOL airline aircraft is predicated on the use of advanced electronic systems to permit efficient use of the airspace and to reduce pilot and controller workload. The systems employed must provide the capability of automatic guidance between check points predesignated in three dimensions. The system, for instance, which is being developed for the Lockheed 1011 transport can use navigational inputs from a number of different sources. These inputs are processed through an airborne computer, to provide a threedimensional navigational capability. For VTOL aircraft, the provision of accurate height sensing during the vertical portion of its approach and climbout is complicated somewhat by the possibility that the aircraft may be operating within its own disturbed wake under calm wind conditions. Thiswould tend to disturb the accuracy of the static pressure input of a barometric altimeter. For this reason, it is believed that a radio altimeter should be utilized during the vertical segments of approach and climbout. In other portions of the flight, an improved type of barometric altimeter can be employed which uses a thin film strain gauge pressure sensor to reduce lag and hysteresis effects. The output would be processed through the airborne computer for vertical guidance of the aircraft along the predesignated three-dimensional paths.

Approach Guidance and Control In the same way that the profiles of the take-off and approach paths are delineated by the effect of noise, the associated time constants are constrained by the biological consideration of the G forces. It seems unrealistic to expect seated passengers to accept aircraft longitudinal accelerations of more than 1/4 G. If this is proved correct, it is possible to start with the concept of maintaining a maximum cruising speed of 250 knots below 10,000 feet as long as possible and computing the time/speed relationship of the optimum deceleration paths for aircraft spacing and for noise abatement profiles. The concept of decelerating the VTOL aircraft in the air prior to its vertical descent, is quite unlike the operation of conventional aircraft, which complete their final loss of speed after landing. This difference emphasizes the need to synchronize the approaching aircraft with a "time slot" that moves along the programmed descent paths. The time constants of such a path will be very similar to that of an automatic railway train braking to a stop in a station. In fact, one cannot envisage approach paths of the kind indicated for VTOL aircraft being achieved by other than automatic means. It would appear unlikely that the task could be done manually with enough accuracy, even if the computed command information were displayed to the pilot. Because of the apparent similarity between the VTOL approach and the automatic train stop, the London Transport Executive was approached about the methods employed in achieving this on the new Victoria Underground Line (2). In this system a programmed deceleration is triggered off at a certain place. The speed is monitored and 8

compared with the programmed speed at increasingly frequent intervals, until the train comes to a halt at a predetermined position. With an adequate airborne computer, an accurate navigation system and a reliable height sensor, it should be possible similarly to initiate and control the VTOL final approach path. In this way, the desired degree of passenger comfort, noise control and approach accuracy should all be achieved.

ATC Interface Experience to date indicates that primary or secondary radar does not make an adequate aircraft position sensor for ATC, in monitoring low-altitude aircraft operations in heavily built-up areas. The use of data link appears to be a better method. In one concept, the aircraft position coordinates obtained from the navigation and altitude sensors are processed by the airborne computer and are transmit!ed automatically, on request of the ground station, to a simple data link antenna located as high as possible in the terminal area (3). Figure 7 shows how this information could be fed to ATC displays. As long as the total input of aircraft to each V-port is carefully metered to avoid exceeding the landing acceptance rate, tight scheduling control en route should not be necessary. Considerable variation in the arrival times of successive aircraft in the terminal area can be corrected simply by controlling the time at which deceleration to some suitable intermediate speed can be made. As an aid in the monitoring and control of separation between arriving aircraft, including scheduling control and the assignment of landing paths, a dynamic space-time diagram generated by a computer and displayed on a cathode-ray tube (CRT) may be the easiest possible method for a scheduling controller to keep up with the situation. In this case the computer could generate an X-Y display, with time shown on the X axis and distance from touchdown shown on the Y axis. The display would show the computed distances from touchdown of each arriving aircraft. This would be superimposed with the display of available landing slots and final deceleration patterns. The display would be a dynamic one; the approaching aircraft would march up the left side of the display as their distance from touchdown decreased. Meanwhile, the time scale would move gradually to the left, carrying with it the approach slots shown by the curved deceleration lines. The display would enable the controller to monitor the approaching traffic, to see that the deceleration of each aircraft was started at the right time, so as to match its space-time curve with the desired landing slot. The headway (longitudinal separation between successive aircraft) will gradually decrease as the aircraft began their deceleration and would be a minimum as the aircraft approached the landing pad.

Approach Monitoring Apart from the direct effect of human tolerance to noise and acceleration, the automatic approach and landing of a VTOL poses important problems in monitoring, both to ensure that the systems responsible for the safe flight of the aircraft are functioning and that its flight path not only complies with the biological restraints, but also with the air traffic control requirements for traffic regularity, clearance of ground obstructions and collision avoidance.

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Figure 7 Possible integration of proposed equipment with FAA alphanumeric ATC display system as installed in Atlanta TRACON and New York Common IFR Room.

Before starting to design monitoring systems, the underlying philosophy of the ATC role in control and surveillance must be considered. Given high integrity ground-toair data links, there is much to be said for sensing the position of the aircraft in three dimensions from the ground and after computation, sending control signals to the aircraft auto-pilot. The advantages in this system are that all the sensing and computing equipment is on the ground where it is not weight-dependent and can easily be duplicated, maintained and repaired. Equipment with this capability is likely to be fully developed and available by 1985. Such a concept has been described by S. S. D. Jones (1 ). He suggests that VTOL operations need a system comprising a ncll band radar, an aircraft transponder, a ground-based angle-sensor, range sensor, computer and track store with a data link for aircraft control. However, this system has three disadvantages. Firstly, it depends upon information essentially coming from one kind of sensor without cross-checking. Secondly, there is no provision for the pilot to monitor the safety of the situation. Thirdly, should any part of the ground orÂˇ airborne equipment fail, the aircraft could not be landed without diversion. A different concept, which would avoid hanging the whole of the system on the integrity of the data link, would use information sensed by the aircraft and processed by an airborne computer, to provide steering information for use by the auto-pilot. The same positional information would be passed continuously by data link to the ground, where it can be compared by ATC with the relevant time slot, and thus insure safe separation from other aircraft. A basic disadvantage of this system is that additional cooperative equipment is required in the aircraft and this will be cos_tly. However, some of this cost can be offset by the almost certain need for an airborne computer for other reasons and a reliable low-level ground-referenced navigation system, that is not dependent on line-of-sight propagation. If the redundancy of a "belt and braces" system is required, then position derived from ground sensors could be relayed to the aircraft via data link and a similar comparison made with the information from the airborne sensors. Implementation of the philosophy described above is well within current technology and much of the hardware exists. Some examples that are known to the authors are listed below:

Requirement

Solution

Automatic multiplesensor input aircraft navigation system, coupled to autopilot and with digita I outputs for data link. Pictorial navigation display. Ground-referenced high accuracy navigation system. Height indication.

Decca/Ambac MONA for Lockheed 1011.

Vertical paths readout and autohover. Data links.

Ground ATC surveillance.

Electronic map. Loran C or Decca.

By continuous comparison of ground and airborne barometric strain gauges through a separate data link; the difference provides an output of aircraft height. Radio altimeter and Doppler driven vertical speed readouts. Decca auto-pilot-coupled Doppler with meter readout for fore-and-aft and lateral speed. Decca Datalink with tri-state logic having unique address and with the capability of 4 complete aircraft height and position transmissions per second. "C" band radar with angular, range and bearing sensors with PPI display. Aircraft position from aircraft navigation system by data link, showing identified position symbol for each aircraft, as demonstrated by Decca at Farnborough in 1966.

References

{l) JONES, S. S. D. "Guidance and Control Philosophy for All-Weather Landingn - The Journal of Institute of Navigation, July, 1970. (2) SMITH, V. H. "Victoria Line Signalling Principles" Journal of the Proceedings of the Institution of Railway Signal Engineers, 1966-67. (3) OAKES, T. "Airline Technical Requirements for 1975 STOL and V/STOL Systems" - Society of Automotive Engineers, Paper 700312, 1970.

10th Annual IFATCA Conference Third-Seventh May, 1971

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An Appraisal of ATC Automation-ÂĽBy J. Grambart NAFEC, Atlantic City, U.S.A.

After 13 years of effort, the FAA has been able to successfully apply the computer to two areas of ATC: bookkeeping and radar target tagging. Bookkeeping (automated flight plan processing, flight strip printing and flight data updating) is operational at several high activity air route traffic control centers. Radar target tagging (alphanumeric data blocks which automatically follow designated targets on a radar scope) is a working reality at the Atlanta TRACON and the New York Common IFR Room (CIFRR). Both automated bookkeeping and radar target tagging are much appreciated by the controllers who use them daily. During the same period three ATC automation applications were complete and costly failures. Data Processing Central (DPC) was a first attempt to use the computer in an en route environment. An ambitious project which combined flight data processing, electronic shrimp boats, automated handoffs and strip printing, DPC never got beyond the experimental stage at NAFEC. It failed primarily because it was not preceded by a rigorous analysis of the existing manual system. DPC was far too cumbersome. It markedly increased controller workload by requiring too much information from the operator. Interestingly, controllers testing this system knew it to be a failure some 12 months before the project was quietly shelved. A later effort, the Stored Program Alpha-Numeric system (SPAN), was first tried at Indianapolis Center, but as a result of a midair collision between two air carrier aircraft over Westchester County, a high echelon decision was made to relocate it at New York Center. Called NYCBAN (New York Center Beacon Alpha-Numerics) in its new home, the system provided target tracking with alphanumeric data blocks only for beacon targets and Mode C altitude readout. It was specifically designed to be used only in a high altitude environment. After a few months of trial the system was removed. The busy New York facility had found that, with moderate to heavy traffic, the data blocks occupied too much of the total scope area, increasing clutter and causing an overwrite problem. The system was not designed for, and could not cope with, a high density mix of beacon and nonbeacon radar targets. The need to operate functioncategory panels, slewballs and alphanumeric keyboards only served to increase the workload of already busy controllers. Their verdict: "We can use it for light traffic conditions, but in moderate to heavy traffic we have to turn it off." Still later a Computer Aided Approach System (CAAS) was evolved at NAFEC and installed at Kennedy Tower for operational evaluation. It was designed to aid approach controllers by giving them computer-generated heading and time-to-turn data, to assure tight but adequate spacing between consecutive approaches. This system too required considerable input by the controller. The Reprinted from ATCA's Journal of ATC with kind permission of the Editor.

Kennedy people worked with it for months but finally requested its removal. Their complaint: "We can use the system for periods of light traffic, but when we get busy we have to turn it off." As infinite flexibility is the essence of efficient high density terminal control, they had found that experienced controllers can manage approach sequencing faster, more flexibly, than a computer. Indeed, the machine had actually slowed the process. Let us consider the automated bookkeeping system in operation at New York Center. Incoming flight plan data is accepted and processed, so that the necessary flight strips are printed, on time, at the proper sector positions. This extremely valuable service is achieved with no information flow from controller to computer. Flight data aides, completely divorced from the control function, make the necessary inputs, tear completed strips from the computeroperated flight strip printers, and post them at the appropriate sector positions. There is one keyboard device at each radar console to permit flight strip updating at adjacent sectors via the Computer Update Equipment (CUE). Significantly, that keyboard is rarely used because the controllers find it quicker to phone an update message to the adjacent sector. At the New York Center a good man/machine relationship is realized; the system services the controller, without in any way interfering with the vital radar surveillance and decision-making processes. The information flow is all to the man. The New York CIFRR system provides computer-printed flight strips, plvs electronic alphanumeric data blocks, tagged to each controlled target. Both discrete and nondiscrete beacon targets, as well as raw radar returns, are tagged and tracked. The New York Center and CIFRR computers are on-line; at least 10 minutes prior to an IFR arrival or departure the center sends the flight plan data to the CIFRR computer. Electronic aircraft identity tags appear, in alphabetical order, and are stored on a scratch-pad area of the controlling radar display. At the same time, printed flight strips, carrying the complete flight plan data, are made available at the position while duplicate strips are printed in the appropriate control tower cab. If the target is primary radar only, it is identified, during the initial radio contact, via a radar target check over the reported position. Alternately, a cross-check between aircraft heading and target track may be used. A nondiscrete beacon target may be identified via the coded target "ldent" process. With target identification established, the controller, using a slewball and category/function panel, initiates tracking and electronic data block-target association. An experienced operator can complete the process in five to eight seconds. Of this time, his attention is diverted from the scope for perhaps two seconds while he pushes the proper category/function button. During the remainder of the computer updating process the controller's eyes are on the scope (where they should be), using the slewball to guide the tracking dot to the desired target. Discrete code beacon targets are automatically tagged and tracked

immediately they appear on the scope, with no controller input. It should be emphasized that the time consuming, attention diverting alphanumeric keypack at the console is rarely used. In the CIFRR, as well as the Center, there is a maximum of information flow from the computer (tags, tracking and flight strips) with very little input from the controller. When discrete-code beacon equipment becomes common, controller-to-computer input will shrink to zero. The CIFRR controllers regard the system as a reliable, extremely useful tool. Air/ground communications are considerably reduce~, since identity, ground speed and (for Mode C targets) altitude, are .visually apparent. Controller coordination is easier because the format includes a symbol identifying the cognizant controller. Target tagging induces a quieter, more relaxed environment. While the system cannot, of it~elf, increase capacity (for capacity is tied to runway availability), the surety of continuous target identity notably decreases controller tension by reducing the possibility for making errors. The payoff is in increased safety. The concept, design, procurement, installation and operational use of the CIFRR A/N system is a shining example of systems engineering and interservice teamwork. It should serve as a model for future effort. Presently one unit of the Notional Airspace System (NAS) is installed and on trial at the Jacksonville Air Route Traffic Control Center, while on engineering model of the same system is installed at NAFEC. Basically, NAS is designed to combine data from airborne transporters and ATC radars, routing it through a powerful computer (IBM 9020 A or E). The computer-processed radar is displayed on cathode ray tube presentations to give the en route controller an extremely flexible A/N radar display. SpEciflcally, the planned features are: 1. Computer entry and processing of flight plan data 2. Flight strip printing at appropriate operating positions 3. Reception and entry of flight plan updates 4. lnterfacility coordination via computer-transmitted data 5. Combined display of A/N and radar data 6. Automated and manually initiated target tracking 7. lntersector coordination (handoffs) through computergenerated A/N displays, bath pion view and tabular It should be noted that items 1 through 4 are already operational at several high activity. cent~rs that are not NAS-equipped, and items 5 and 6 are m daily use at Atlanta Tower and the CIFRR. Importantly, in these successful applications, the automated service is available with little or no information flow from controller to computer. The aid is truly automated; it does not interfere with the controller's decision-making process. In contrast, the NAS sector radar controller is confronted by an imposing array of buttons, panels, switches, keyboards and readout devices. There is a function/category panel, operated in conjunction with an alphanumeric keypack and slewball. In addition to a "quick action panels,,,' there are A/N generator controls, display controls, a CRT computer readout display, scan converter controls, system status indicators, and system failure entry keys. The sector "D" console is equipped with its own function/category panel and computer readout device, and in addition has a full keyboard for data entry. The sector "A" console has the same equipment as the "D" position; it also contains a flight strip printer.

The number of input devices is astonishing; one wonders if the man exists to serve the machine I In actual operation of the NAS engineering model at NAFEC, controllers exercising the system through the many test programs often were not able to use radar separation, since this, of course, requires target monitoring. Instead, the simulated targets had to be separated by ANC; that is, by altitude and time intervals, so that controllers could be free to operate the multitude of input devices. They could monitor radar, or feed the system; they could not do both. And these men had about 18 months experience with the system! It is not surprising that about a year ago, NAS began to be referred to as "DPC II." The NAFEC controller experience has been duplicated at the Jacksonville installation. Controllers there have found that the system, even in its simplest application (flight data processing and strip printing), and during the lightest traffic periods, decreases their capacity by requiring too much human input. Workload is increased. Present programming problems, combined with difficulty in procuring two key NAS equipments, the Computer Display Channel (CDq and the displays themselves, indicate that it may be several years before alphanumeric shrimp boats and target tracking is available. Why was NAS created in its present cumbersome configuration? The answer lies in the research and development that was not done before the system (20 items!) was procured. Viewed in this context, it should not be surprising that the test and evaluation that was begun only after mass procurement unmistakably indicates that the system requires massive and courageous redesign. And unless that redesign is accomplished, NAS is in danger of becoming a technological white elephant, costly, embarrassing and operationally unacceptable. What is the single most valuable lesson learned from these various automation projects? The question can best be answered if we comprehend the outstanding difference between the successes and the failures. That difference lies in the crucial relationship between the computer and controller, which may be stated as an axiom and a corollary: The viability of an ATC automation system is inversely proportional to data flow requirements from the controller to the computer, and directly proportional to data flow from system to controller. Until a system can directly assume part of the vital decision-making burden, it should not increase the controller's peripheral workload. This statement may seem obvious; the present design philosophy and configuration of NAS is evidence that it is not. The considerable inventory of ATC automation experience possessed by the FAA provides undeniable proof that operationally useful computer aid must require little or no controller input. The high activity controller (who should get the first benefits) is an intensely busy man who routinely works at or near capacity; he cannot be expected to safely separate and expedite traffic and hand-feed a computer. The existence of successful ARTC flight data processing, and the CIFRR A/N system, is hard evidence that valuable computer aid without controller input is both possible and practicable. Both systems meet the ultimate pragmatic test; they are helpful, and they work reliably. Each system is conceptually simple; neither attempts to do too much. The experience gained in building and programming them should be applicable to NAS. Let us begin by questioning some of the NAS concepts that seem of doubtful value and even, perhaps, impossible 13

to implement. Digitizing and processing the radar signal is very costly in terms of digitizing equipment, complex displays, programming, computer capacity and storage. Further, there is a philosophical difficulty. The SAGE System (and NAS was sired by MITRE, out of SAGE) displays processed radar targets as small symbols on the cathode ray tube face. Target symbols may be crosses, circles, triangles, etc., but they are often smaller in area than the unprocessed returns. The processed target, if it is to provide the same degree of positional truth (relative to actual aircraft placement) as an unprocessed return, must be shown as a probability area of the same size. Any system which is interposed between the radar antenna and the display must inevitably diminish both target positional "truth" and system reliability. This being so, the controller will be unable to use a digitized display with the same confidence and freedom from down time now offered by unprocessed radar. And in ATC systems, confidence and reliability are essential attributes. It is perfectly possible for a computer to sense and store radar position and velocity data without digitizing the displayed return; the CIFRR system does just that. Perhaps future plans for automating some of the decision functions may make digitizing necessary, but at the very least it is open to doubt. In any case, the digitizing process and CDC capability will add years to system implementation; it should be relegated to an R&D status until proven operationally useful and reliable. Meanwhile, field implementation will proceed faster and less expensively if NAS is reconfigured and programmed to provide unprocessed radar on reliable and procurable displays. This single step will do much to simplify the system, increase its reliability and diminish overall cost. The NAS features previously listed as items 1 and 6 are of proven operational value. As earlier pointed out,

they are routinely used at a few centers and at the CIFRR. But, like these operational systems, NAS must provide these features with little or no controller input, or the new system becomes a long step backward. To that end the NAS consoles should be ruthlessly cleared of all input devices that would divert attention from the radar displays, and that would add to the total workload. The 7th feature, automated intersector handoff coordination, at least as presently programmed, is far too time consuming, and has notably contributed to the problems of NAS test controllers at NAFEC. It is far slower than the present aural handoff, because of required computer input. If the handoff function is eliminated, so is the troublesome target eligibility problem. Simultaneously, controller input is markedly decreased, and the need for console input equipment diminished. Recommendations

1. Place digitized radar in an R&D category until it is technically and operationally proven. 2. Program NAS to provide the listed features 1 through 6 through a software philosophy modeled on that of in-being, field-proven systems. 3. Rigorously eliminate, or severely limit, controller input. 4. Model the NAS consoles on those in present use, eli-

minating input devices from the radar positions. Over the past decade the FAA and SRDS have accumulated uniquely valuable experience in the integration of computers and air traffic control. Inevitably the knowledge was acquired at considerable cost. If we are to profit from that hard-won experience, it must be used as the basis for future system improvement.

1971 CATCA Convention The Canadian Air Traffic Control Association will be holding it's biannual Convention at the Inn On The Park Hotel, Toronto, April 26 through April 29, 1971. Two of the events at this Convention will be evening panel discussions on the topic of "The Pilot and The Controller". Scheduled for the evening of April 26 is the first panel, entitled "Aviation and Air Traffic Control-legal Aspects". Panel moderator will be Mr. Frank Rock, formerly Chief Pilot for the Abitibi Paper Company, now engaged as the Director of the Aviation and Flight Technology Course, Seneca College of Applied Arts and Technology, Toronto. Panelists will include: - Capt. J. C. Morden - Chief Pilot, Nordair limited representative Air line Pilot; - Mr. Eric Lane - prominent Aviation Lawyer - Toronto; - Mr. Trevor Moores - Tower Supervisor, Toronto International Airport; - Mr. Ken Gray - Terminal Controller, Ottawa Terminal Control Unit - representing the Canadian Air Traffic Control Association. In addition there will be two Business/Private Pilots on the panel, one representing the Canadian Business Aircraft Association, the other representing the Canadian OwnersPilots Association. A representative of the Ministry of Tran sport has also been invited to attend and participate. 14

The second panel, scheduled for the evening of April 28, is entitled "Aviation and Air Traffic Control - Safety". Moderator for this panel will be Mr. Harvey Kirck, past active as a Private Pilot, and who has the present distinction of being the Editor and "On-The-Air" Anchorman for the CTV Television Network National News. Panel participants in this case will include: - One Air line Pilot, representing the Canadian Air Line Pilots Association; - One VFR and one IFR Air Traffic Controller, representing the Canadian Air Traffic Control Association; - Three Business/Private Pilots, two of which will be representing, respectively, the Canadian Chapter of The 99's, and the Royal Canadian Flying Clubs Association. The third Business/Private Pilot will be Mr. Reg Reynolds; President of, and representing; the Canadian Business Aircraft Association. In this case, as before, a representative of the Canadian Ministry of Transport has been invited to attend and participate. Also planned for the Convention is an area of technical exhibits which will be informative to all representatives of the aviation industry and in addition give them the opportunity to view the manufacturer's latest products. Further information may be obtained from Mr. Bill Robertson, CATCA Secretary-Treasurer, P. D. Box 13, Toronto A.M.F., Ontario, Canada.

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The Operational Plan for the Maastricht Upper Area Control Centre

Following is the extract of a paper which was first published in the EUROCONTROL Journal No. 6/1968. While some aspects of the Plan have been changed since then, the basic philosophy of the Maastricht Operational System is still fully valid, and it is considered that this article wi ll be of interest to a great number of our readers. (See also page 23)

Figure 1 The Moostricht Upper Area Control Centre.

Introduction In the preamble of the International Convention dated 13th December, 1960 by which Eurocontrol was created it is stated that the entry into service and general deploy~ ment of turbine-engined transport aircraft may give rise to far-reaching changes in air traffic control. The reasons a~e that modern types of aircraft are characterized by high speeds and by the need, for reasons of economical operation, to make an uninterrupted climb at a higb speed to optimum operating altitudes, and to remain at those altitudes until a point as near as possible to the destination of the aircraft has been reached. Therefore these characteristics would not only imply the reorganization of existing control methods and procedures, but also the creation, above a certain level, of new flight information regions, organized in whole or in part into control areas. Consequently the control of aircraft at high altitudes could no longer be envisaged within the restricted framework of notional frontiers in the case of the majority of European countries. It was with these considerations in mind that the Permanent Commission of Ministers decided in 1964 to establish Eurocontrol's first international area control centre at the airport "Zuid Limburg", 10 km North of Maastricht in the Netherlands, to provide air traffic services in the upper airspace over Belgium, the northern half of the Federal Republic of Germany and the Netherlands.

The Area to be Controlled and its Main Traffic Characteristics In the Benelux/Federal Republic of Germany Region some 10 major civil airports generate traffic in the upper air space, and a large number of military air-bases, not only used by the national air forces but by other NATO air forces as well, contribute considerably to the air activity. Civil movements are concentrated along four main axes: London - Belgium - Frankfurt - S.E. Germany, North~South over Germany (Denmark - Switzerland}, London - Netherlands - Germany- Copenhagen, and Central England-Amsterdam - Frankfurt. Flights in the region are mixed shortand long-haul operations. Air traffic services will have to be provided in this environment to air traffic operating in the upper air space, i.e. from Flight Level 200 (20,000 ft) and above in the Benelux airspace and from Flight Level 250 (25,000 ft) and above in the airspace of the Federal Republic of Germany. Air traffic, in the sense of the Eurocontrol Convention, comprises civil aircraft and those military, customs and police aircraft which conform to the procedures of the International Civil Aviation Organization (ICAO). This air traffic is called General Air Traffic (GAT}. Military air traffic that cannot comply with the ICAO procedures is called Operational Air Traffic (OAT). GAT will be controlled by the Maastricht Centre, whilst OAT will be controlled by military air traffic control units. Since both categories of air traffic are operating in the same airspace, an effective coordination system will be required to ensure that adequate separation between GAT and OAT is provided. The Maastricht Centre will have to provide air traffic services to a large number of turbine-engined high-performance aircraft. Recent years have shown a rather explosive development of this type of traffic in the upper

airspace and a marked shift of aircraft movements from the lower to the upper airspace has been observed. On the basis of traffic analyses carried out over a number of years the following GAT traffic fore casts have been established: 1972

1975

Peak Hourly Rates Amsterdam Sector Brussels Sector Hannover Sector (Northern FRG)

80 95 75

90 115 85

Instantaneous Peaks* Amsterdam Sector Brussels Sector Hannover Sector (Northern FRG)

40 48 38

45 58 43

To these figures must be added a number of military aircraft that will operate as GAT, but will not normally fly along the established route system. There is therefore a justified need, as indicated in the preamble of the Eurocontrol Convention, for an organization of air traffic services adapted to the needs of highperformance aircraft operating in the upper airspace.

Present Organization At present, within the "Maastricht UIR" air traffic services in the upper airspace are provided on behalf of Eurocontrol by the control centres of the national administra!ions concerned, except in the upperÂˇ airspace over Belgium and Luxembourg where the services are provided from the Brussels Upper Area Control Centre under the direct responsibility of the Eurocontrol Agency. In the Federal Republic of Germany (FRG) an upper ?rea control unit at Hannover provides air traffic services in the Hannover UIR, whilst air traffic services for the upper airspace in the southern half of the FRG are provided from upper airspace facilities at Frankfurt and ~unich. In the Netherlands, an Upper Area Control Unit is expected to commence operations in the near future. These units, dispersed over a large area, will ultimately be consolidated in the Maastricht and Karlsruhe UACs in order to provide a more efficient, unified and integrated service.

Operational Obiective and Concept . The operational objective is to provide positive control, 1.e. control service to all aircraft irrespective of weather conditions, without imposing undue restrictions on them. It is, however, evident that such an objective can only be achieved by a series of development phases. System developments are directed towards the extension of controlled airspace in step with the development of military air traffic control systems and coordination methods between these services and the civil control units. The first aim is to expand controlled airspace from FL 250 to all flight levels operationally used. A step in this direction was taken in 1967 by the introduction of a Flight Advisory Service in the BNL/FRG Region from FL 250 to FL 460. Many civil operators, who in the past obviously preferred to confine many of their flights to controlled airspace (FL 200-FL 250) within the Region, now appear â&#x20AC;˘

The instantaneous peak is defined as the maximum value of the 6 minutes rate, that is the number of aircraft instantaneously present within the volume of airspace under consideration, plus those aircraft entering that airspace during the following five minutes.

willing to avail themselves of this new service. This in turn is resulting in better vertical distribution of traffic. The final aim is to introduce positive control, thereby completely eliminating VFR flights in the upper airspace. In designing the Maastricht concept it was decided to divide the airspace to be controlled by the Maastricht UAC into sectors, which will be as large as possible in order to reduce transfer of control and its related coordination to a minimum for a given flight in the Region. For various reasons, such as civil-military coordination and coordination between lower centres and Maastricht, the sectors in the Benelux Northern FRG area will, in the initial phase of operation of Maastricht, correspond generally to existing national Upper Flight Information Regions (UIRs). Forecast short-term peaks shown in the preceding table give an indication of the number of aircraft that will be present in these UIRs almost simultaneously. They are of particular interest because it is possible to deduce control workload from these figures. If the traditional method were applied whereby one controller is responsible for the control of aircraft in a given sector, these Regions would have to be broken down into a large number of sectors, since the number of aircraft expected to be present in a region would be too large for one controller to handle. This would result in many transfers of control actions between sectors and frequent changes of radiocommunication channels for the aircraft, as is apparent in the lower airspace of the region with some 30 individual sectors. In order to avoid this increase of workload on the ground and in the air large sectors have been designed, based on the pattern and complexity of the traffic flow. The number of controllers operating such a large sector must, of course, be increased. This increase is, however, again limited to a certain number whereby the internal coordination within the sector stays within reasonable proportions. During a simulation exercise, carried out in 1963 at the Experimental Centre of the United States Federal Aviation Administration at Atlantic City, where the fundamental system for the Maastricht UAC was investigated, it was found that one planning controller and up to four executive controllers would form the optimum number for the control team of a sector. Such a team would be able to handle the traffic presently forecast on an UIR basis with the proposed number of sectors. The planning controller will be charged with the planning of the movements of the aircraft expected to operate in the sector on the basis of flight plan information, updated as far as possible before the aircraft enters his sector. Potential traffic conflicts will be detected for enroute aircraft and as far as possible removed. The planning controller may not, however, be in a position to remove all conflicts in the planning stage, as he applies rather large separation standards. He will then decide to let the aircraft continue with less separation than that used for planning purposes, but under radar surveillance carried out by the executive controller. This executive controller, who maintains radiocommunication with the aircraft, will assume a monitoring task until the minimum radar separation is liable to be infringed. In that case he will intervene and take appropriate measures to maintain safe separation. Traffic will be assigned by the planning controllers to the executive controllers on a route basis in such a way that one controller will control an aircraft throughout the 18

sector. Change of radio frequencies for communication purposes and transfer of control within the sector will thus be avoided. Aircraft flying "off-route" will be taken care of by one or more executive controllers, depending on workload, manning special "off-route" working positions. Figure 2 shows the sector organization in diagram form. Data Sources The two principle sources of data for the air traffic control functions are flight plans and radar. Flight plans, filed by the captain of an aircraft with Air Traffic Control at the airport of departure, will arrive at the UAC either by teleprinter via the AFTN (Aeronautical Fixed Telecommunication Network) or through direct computer to computer links, since it may be expected that at the time of operation of the UAC, automatic data-processing, including automatic data transfer, will be applied at several adjacent and subjacent ATS units. Flight plan data must be supplemented and updated by actual information on aircraft movements in the area of responsibility. Complete primary and secondary surveillance radar cover for the region will therefore be provided. The information obtained from three primary/secondary surveillance radar installations in the Benelux/FRG region (also used for lower airspace purposes) must be displayed to the controllers irrespective of the geographical configuration of a sector. This means that more than one radar will be required to compose a dynamic picture of the traffic situation on the executive controller's radar display. The radar installations to be used for this purpose (Bremen, Leerdam, Brussels) have been selected on the basis of their coverage characteristics and geographical location within the BNL/FRG Area. The performance characteristics of these new radars have jointly been developed by the national administrations and Eurocontrol to meet the operational need of both upper and lower airspace air traffic control. Figure 3 shows the theoretical SSR cover based on line-of-sight characteristics from 15,000 ft upwards including the Southern FRG, which, however, does not f~rm part of the Maastricht UIR. Since the secondary surveillance radars play a predominant role in data acquisition, certain additional SSR installations will be used as standby radars, thus ensuring duplicate cover for the Region. As for as the transmission of radar information to the Maastricht _Centre i~ concerne~, ~wo methods have initially been considered, 1.e. transm1ss1on of video signals via broadband radio links, or digitalization of the radar information at the radar site and subsequent transmission of these .digitalized data via narrow-band telephone lines. As the automation of various air traffic control functions at the Centre required the digitalization of radar informati~n anyway, and as radar digitalization techniques are sufficiently adva.nce_d to meet the. requirement of the planned system and its hme-scale, while at the same time offering con.siderable advantages, it was decided to digitalize both primary and secondary radar information at the radar sites and transmit it to the Centre over a system of land lines that will ensure the greatest possible reliability. Automatic Data Processing Increase of traffic means increase of workload and where this exceeds certain limits, the existing sectors of a manual system must be multiplied. More working positions

must hence be established far operating the increased number of sectors. As had been said earlier, however, such a development is contrary to the requirements of aircraft operating in the upper airspace. A greater number of smaller sectors produces extra workload in the cockpit and considerably increases the coordination problems of the controllers on the ground. The aim must therefore be, in order to maintain reasonable sector s izes, to increase the controller's efficiency and effectiveness. This can be done by relieving him from routine functions, such as data acquistion, sorting, display and updating of information, and giving him more time far his genuine task, i.e. the control of traffic. Routine functions, such as the above, can well be performed by an automatic system. For handling the large amount of flight plan, radar and relevant control data related to the traffic we are concerned with, automatic data processing has already become a necessity.

means of input keyboards. Before the final " Input" or " Execute" button is pressed, the Flight Data Operator can verify the information he typed in, on a preview display. With this facility he can check whether any errors hove crept in during the input process and can rectify them if so required. The computer is provided with a table of aircraft performance characteristics. Wind and temperature data for various groups of flight levels far a number of sub-areas of the Maastricht UIR is fed into the system in digital form via a direct link with a meteorological computer in the Region. With this information the Maastricht automatic data processing system can calculate the progress of a flight along the route of the aircraft, including tbe ET As over

Figure 2 Sector O rgan ization. Figure 3 Theoretico l SSR cover ot 15.000 It.

The system to be app lied ot Maastricht UAC ha s b een designed to perform all the above functions, with a particular view to automatically providing the controller with exactly (and only) the piece of information he needs to control hi s traffic, ot exactl y the time this information is required . Thus the system will greatly facilitate inter-sector coordination; it will also provide far the automatic on-line exchange of flight data between the UAC and such adjace nt or subjacent ATC units which are appropriately equipped. Âˇ Where automatic data exchange is not possible and flight plans arrive via the AFTN link, or by o ther mean s such os telephone or R/T, they wil l be input manually at a "Flight Data Section" in the Centre, wh e re the se messages wi ll be received. (The Flight Data Section will also be responsible for manually transferring information to ad jacent ATS un'its which are not automated.) Th e information received at the Flight Data Section wil l be checked a nd fed into the' computer in the established message format by

the re levant reporting points, and di sp la y it at the a ppropriate time to th e controllers conce rned. With all relevant aircraft movements thus calculated and stored, the system w ill be abl e to carry out a conflict search and show th e Planning Co ntroll e r where and whe n separation standards might be infringed. Conflict search is initia lly carried out for level flights along routes only. Th e problems a ssociated with cl imbing and descending, a nd "off-route " traffic wi ll be dea lt with by the Executive Co ntrollers. Exte nsion of conflict sea rch will be a further development. W hen information is obtained that th e actual progress of th e a ircraft is not in conformity with the ca lculated progress by observation of the aircraft position on a radar display o r upon receipt of actua l information by other mea ns, " updating " of the information avai la ble in the computer can be ca rri ed out by manua l input through an input 19

device by the controller. The computer will then make the required corrections and display new estimated times of arrival over reporting points. Since all radar information is being processed by the computer, updating will in normal circumstances be done automatically as will be explained below. As explained under nData Sources", primary and secondary radar information will be extracted at the radar site. This will be done in digital plot form, i.e. the data to be sent to the Maastricht computer will contain information on azimuth, range, SSR mode/code and various other data required for technical purposes. Although mainly SSR information will be used, primary radar information will be available in case SSR information on an aircraft is lacking. At the Centre the computer carries out coordinate conversion of the information related to the different radar positions to a common reference system. If further initiates automatic tracking (flight following and identification) on aircraft responding on specified four and two djgit codes. (Other SSR responses and selected primary radar plots will need manual track initiation}. Once track initiation has taken place, correlation of track and flight plan information is carried out automatically for 4digit (4096) code responses on which flight plan information, containing the corresponding mode/code information, is in store. Other cases require, in general, manual correlation. It is then possible to display on the synthetic (computerdriven} radar data displays (also called synthetic dynamic displays} track information consisting of a position symbol, the identification of the aircraft and the flight level (derived from mode C information). This position information is renewed every three seconds. As both calculated and actual progress of the aircraft are in store, updating of displayed plan information can thus be carried out automatically. Following the updating of aircraft positional information a renewal of conflict search will be required in order to see what effect the change in progress of the aircraft has with respect to other aircraft in the system. If, according to a set parameter, the change is such that the separation standard is infringed, the planning controller receives a conflict warning on his electronic data display and can then take appropriate measures. Data Display Facilities

The planning controller's task is to establish and formulate the overall plan for the safe, orderly and expeditious movement of air traffic by allocating routes and flight levels to aircraft in a manner to provide adequate separation. He therefore requires appropriate flight data on the aircraft concerned, which need to be displayed to him in an easily interpretable way. It is foreseen that he will not restrict his activity to his particular sector, but will plan for the flight throughout the UIR. This is considered feasible because the data processor contains the information of all aircraft operating or proposing to operate within the Maastricht area, it has a conflict-detection capability and allows the display of information to the planning controller appropriate to the current and planned traffic situation in other sectors of the Maastricht area. The data display facilities for a Planning Controller will consist of a Synthetic Dynamic Display (SOD) and two Electronic Data Displays (EDDs}, with a normal flight pro20

gress board to act as back-up in case of failure of the electronic displays. The SOD will be of the some type as the SOD of the executive controllers and will show him the actual traffic situation in order to assist him in his planning activities. One of the EDDs will be used to display the list of flights assigned to the sector, flight plan messages and other information of interest to the controller. The second EDD will normally present information concerning aircraft which are or will be operating within the sector for a period of time defined by the "now time" and the following 20 minutes. This information is shown in tabular form in relation to the sector reporting points. This information will, however, be replaced by a message showing the result of a conflict probe either at the request of the planning controller or automatically as soon as the standard separation between two aircraft is infringed. This message will show the traffic situation along the planned route within the UIR in relation to the aircraft for which the conflict probe has been carried out. Items to be displayed will consist of ETAs over selected reporting points along the route and information on all aircraft which will also pass these reporting points within a predetermined number of minutes before or after the estimated time of arrival of the aircraft for which the conflict search has been carried out. By means of trials at the Eurocontrol Experimental Centre, optimum message formats and presentation of data to the controllers have been established. The executive controller is concerned with the implementation of the plan established by the planning controller for the flow of traffic and with monitoring the evolution of this plan. In the case of level flights on ATS routes, his degree of active control involving radar separation will in principle be limited to exceptional cases. Mostly his activity will be directed to the application of radar separation during climbs and descents of aircraft, and in the event of level changes. The SDD will show him the instantaneous positions of all aircraft for which he is responsible and which are allocated to him by the planning controller. He will transmit clearances and messages to aircraft under his control and effect radar handovers to adjacent sectors. The data displayed on the SOD are basically position data on aircraft obtained from primary and secondary radars, mobile labels associated with position data, containing information on the aircraft's identity (call sign, flight number), flight level and a symbol to indicate the attitude of the aircraft (level, climb or descent). A vector leader originating from the position symbol, representing one minute of flight and an artificial afterglow of the position symbol will assist the executive controller in assessing the track followed by the aircraft. Different position symbols will indicate whether the aircraft's position information is obtained by SSR and correlated with flight plan information, obtained by SSR but not correlated, or derived from primary radar information. Since there will be up to four executive controllers per sector, the aircraft allocated to particular executive controllers will be distinguishable by a special marking of the position symbol of the aircraft indicating which controller is responsible for the aircraft. A task allocation bar, which will be displayed over the identification of an aircraft, will indicate to the executive controller that infringement of planning separation basis exists and that radar

monitoring and intervention may be required. Figure 4 shows a typical representation of track and label information on an SOD. The usual electronic maps and other relevant background information will a lso be displayed.

Civil Militory Coordinotion

As mentioned in the beginning, on efficient method of coordination between the UAC and military air traffic control units (MATRACs) is necessary. In the Maastricht system this is ach ieved by automatically transmitting, via digital data links, information on GAT that is available in the Maastricht data processor to th e MATRACs concerned. These units will thus be able quickly to identify GAT on their radar displays in a reliable manner. On the basis of this information the military air traffic controllers are in a position to maintain separation between the Operational Traffic under their control and the GAT that is controlled by Maastricht. As information on GAT is readily available on both sides, any additional coordination that might become necessary between civil and military controllers is greatly facilitated. Further Provisions

Figure 4 Presen tation of aircraft position with track and labe l information on an SDD (Synthetic Dynamic Display).

The area with wh ich the executive controller is concerned can be se lected as require d. This wi ll be a "cutout" of th e total picture available in the data pro.c essor. EDDs for the executive control lers wi ll show information re lating to the aircraft under their control. Further data such as meteorological information ca ll ed up from the com puter store, wil l be dis played on these EDDs as we ll. The executive controll er can also request printed strips for a ircraft under his control shou ld his EDDs become inoperative. Both the planning and executive control positions wil l be provided with appropriate input fac ilities in order to insert information or instructions into the computer, radiotelephony operating equipment for communication with aircraft in their sector, and te lephone facilities for coordination and exchange of information with other air traffic co ntrol units. As is apparent from Figure 2, there are more working positions in a sector, such as the Assistant Planning Controll e r position and th e Coordinator. It wou ld however be going too far to describe th e displ ays and equ ipment of all of them.

Since the Centre will need a large amount of speedy and re liable voice communications with other civil and military air traffic control centres for coordination and data transfer purposes (in so far as automatic transfer is not possible, or to supplement such automatic transfers), a fast and efficient switching system for telephone circuits is necessary to provide the controllers with almost immediate commu nication when so required. Such a system will bring its utmost efficiency into practice when the correspo nding parts of the telephone system in adja cent ATS units are compatible. To th e fullest extent possib le use will be made of the input keyboards to select also communication channels in order to simplify the control lers' equipment environment. As in every area control centre there is, in addition to th e data required for the calculation of the progress of flights, a req uirement for meteorological data for the information of the control staff and for onward relay to aircraft. Information about a la rge numbe r of airports and air-bases in and outside the region must therefore be available. Since the three main meteorological centres in the region are provided with automatic data processors, it will be possible to feed the required data automatically from such a centre into the Maastri cht da ta processor, where the contro ll er can request display o f meteorological informati on on his e lectronic data display. Inform ation of a more stati c nature like lo ng er-term forecasts, weather maps, etc. for the briefing of control staff, wil l be provided by messages through the AFTN and by facsimile transmiss io n from a meteorological centre. A smal l unit in the centre wi ll take care of the preparation and production of a daily NOTAM summary organized in accordance with the needs of ea ch sector in the centre on the basis of NOT AMs received through the AFTN. They wi ll further notify the appropriate sector control positions of the co ntents of Class I NOTAMs which are of immediate significance to the current centre and sector operations. The establishment of a control centre using an advan ced system and working ll)ethods such as Maastricht, will no dou bt have a promotive effect on the whole of the air traffic syste m in the region. Its implementation must therefore be carried out in close co llabo ration with the related national air traffic services in order to arrive at a flawless operation of the overall system and to offer a ircraft operators a safe and efficient flight path. EURO

M A

D A

p PERIPHERAL COMPUTERS

PC 11-12-13-14 TFK TR 86

A Description of the Technical Features of the Maastricht Upper Area Control Centre Automatic Data Processing and Display (MADAP) Systemic Introduction The operational plan for the Maastricht Upper Air Space Control Centre is described on page 16. This article provides a technical description of the Maastricht Automatic Data Processing and Display (MADAP) System that is in the process of being installed at the centre. This system is required to perform essentially the following automatic functions: - the processing of flight plan data received from neighbouring air traffic service units or from aircraft through the air/ground voice communication system; - the processing of radar information received from a number of remote primary and secondary surveillance radar stations; - the correlation, storage, up-dating and arrangement of the data for display as required at a number of operating positions. The system contains in all eight computers, over 80 operating and training positions and approximately 140 display units. It can deal simultaneously with an estimated number of 200 active flight plans and 250 processed tracks. It is designed to operate with a high degree of reliability with no possibility of a complete system failure. Other important design aims are extension possibilities to provide for increased traffic and development potential to meet the changing requirements of the future. Configuration of the System The general configuration of the system, which â&#x20AC;˘s shown in the form of a block diagram (see Fig. 1), has been evolved from studies and experience obtained .in the implementation of the Experimental Data Processor (EDP) which has been installed at the Eurocontrol Experimental Centre at Bretigny. The system comprises essentially the following four elements: - the external interface equipment, which allows connection to be made to all outside data sources such as neighbouring ATS units and remote radar stations (DLS/TSU and SMX); - the main computer complex, which processes the flight plan data and radar data (MCC); - the peripheral computer complex, which interprets controller input messages and outputs data to the display system (PCC); - the operator input and display system whose function is evident from its title (ODS). The whole system is capable of operating in two states which are described as the normal state and the emergency state of operation, each of which consists of a defined hardware configuration and software structure. In the normal state, the hardware configuration requires at least one main computer to remain in operation, the software organization utilizes full system capacity and all the Extract of an article that hos been published in Vol. 2-11, 1970, of the EUROCONTROL REVIEW. Reprint with kind permission of the Editor.

operational functions are available. In the emergency state, provided for the improbable case of a breakdown of the two main computers, the hardware configuration is based entirely on the use of the peripheral computers, the software structure is correspondingly changed to a simpler design and the operational functions are reduced to a level as will provide a minimum operational service for a limited period of time. The External Interface Equipment The External Interface Equipment enables the MADAP system, which is located within the Maastricht UAC building, to be connected by landline circuits to various outside units for the transfer and transmission of data. The external units include the following: - neighbouring ATS units for the transfer of flight plan data; - military air traffic control centres (MATRACs) for the transmission of flight plan and radar data from the Centre to the MATRACs; - a meteorological (MET) station for the receipt of meteorological information; - remote radar stations from which primary and/or secondary radar data is received. In order to provide for flexibility in the type of external circuit required for the transfer of data to the outside units, the External Interface Equipment enables connection to be made to the following types of circuits: - 6 duplex telegraph (50 bits/s) 1 circuits for connection to ATS units; - 6 duplex medium speed (l ,200 bits/s) telephone circuits for connection to ATS units, a MET unit to the MATRACs; - 18 high-speed (2,400 bits/s) telephone circuits for connection in all to 6 radar stations (3 circuits per station) for the uni-directional transmission of radar information. Provision is also made for the expansion of the low and medium speed connections to external units by the inclusion of additional equipment. The external interface equipment has been designed within reasonable limits to provide for the foreseeable requirements of the future. In order to provide the required degree of reliability of the MADAP system it is necessary to feed all incoming data to the two main computers MC 1 and MC 2 of the main computer complex (MCC) and to the two standby peripheral computers PC 21 and PC 22 of the peripheral computer complex (PCC) so that each is in possession of the data in case of breakdown. This is done in the external interface equipment through data link splitter units (DLS) which enable each incoming circuit to be connected in parallel to the four computers. Similiary, in the case of outgoing data, each external Binary digit-abbreviated to "bit": Basic unit of information which designates only one of two possible values [zero (O) or one (l) or states "yes" or "no", open or closed, etc.)

circuit is connected to o combiner unit or transmission selector unit (TSU) so that any one of the four computers that is in operation may feed the data to that particular circuit. Initially, the operation of the external interface equipment will be on the basis of a fixed circuit network. The necessary provisions are being made, however, for the eventual use of an automatic switched circuit network for data and telephone communication when the MADAP system will be linked to the Maastricht Operational Telephone Exchange (MOX) System, which will be implemented in the Centre. The external interface equipment also includes the main computer sub-multiplexer units (SMX). The SMX unit, one of which is connected to each main computer, performs the following functions: - transfer of the data communicated simultaneously and in a random manner synchronously or asynchronously via the external circuits in an ordered manner sequentially to the main computer; - conversion of data communicated serially via each external circuit for parallel transfer to the main computer. It also performs the reverse function maintaining the appropriate data transmission rate for the external circuit; - parity checking of the data either at field or character level with signalling of parity errors to the main computer. Simila r functions to the above are performed for the standby peripheral computers PC 21 and PC 22 in the data transfer units of these computers. The Main Computing Complex (MCC)

Th e main computing complex performs the following functions: - Flight plan processing;

The Maastricht UAC buildi ng (March 1970).

Multiple radar data processing and tracking; Rodar/ Flight plan correlation; Automatic updating of flight plan data; Supply of information to the peripheral computers for further processing and display.

The above functions are carried out by one single IBM 360/50 (MC.1) computer together with the appropriate peripheral equipment. The central processor unit (CPU 2050-1) has 512 K bytes 2 (K = 1,024) of 2 microsecond cycle time core memory, which forms the primary storage for the supervisor programmes, user programmes and data. The basic unit of storage is the 8-bits byte and 1-bit for pariiy. Se~ondary storage units comprising four magnetic tape units and four disc units are provided with the possibility of access by either main computer. The external storage control units are connected to either main computer via a selector channel. The selector channel may be regarded as a powerful computer whose function is to transfer data out of the CPU and into it from the external memories. The selector channel may input or output information from the tape units or disc units, one at a time, but it can perform this transfer of information at the rate of 800,000 bytes per second. Each magnetic tape unit can transfer data at the rate of 60,000 bytes per second. Each disc storage unit can store 7.25 million bytes per removable disc pack and data may be transferred at 156,000 bytes per second. Thus the external memories can store considerable quantities of information which may be transferred rapidly into the central processor unit so providing a powerful main computer. The main computer carries out the functions outlined above from data such as flight plan information and radar data from external units to which it is connected via the submultiplexer. Flight plan information which cannot be Byte= 8 bit.

exchanged automatically between external ATS units and MADAP is dealt with by manual operations through the operator input and display system (ODS) from the flight plan data section (FDS). Other peripheral equipment is connected to the computer to enable information to be inserted in the computer or extracted from it either when it is connected to the external sources of information, i.e. operating on-line, or when it is not so connected, i.e. operating off-line. This external equipment comprises a console typewriter, a card reader/punch and a high speed printer. These ore connected to the central processor in addition to the submultiplexer through a multiplexer channel. The multiplexer channel allows a number of low-speed devices to operate concurrently by 'byte interleaving'. The channel may also operate in 'burst mode' i.e. non-concurre ntly by carrying out input/output fur:ictions sequentially. Th e maximum data rate of this channel is 160,000 bytes per second. The central processor unit feeds the processed data to the peripheral computer complex (PCC) for Âˇfurther processing and display. Thi s information again is fed via a se lector channel similar to the one feeding the external memories and permits a large amount of data to be transfe rred in either direction within a short time. The various processes described cannot be carried out simultaneously in the computer and the funct ions are therefore performed under the control of a supervisor programme which will automatically monitor and control the system function s as well as the system configuration require d to ensure the continuity of the functions in the event of various possible breakdowns in the system. In order to provide syste m relia bility o second identical IBM 360/50 standby computer (MC 2) is provided which takes over upon foilure o f the operational main computer (MC l ). Fa cilities ore also prov.ided to enable all peripheral equipment, with the exception of the console typewriter and the main computer sub-multiplexer, to be operated with e ith e r processo r. This is arrang ed by th e provision of two-channel switches which permit the selection of eithe r of the main processor hig hways by programme or by manual operation on the control unit associated with each p eriphe ral equipment. The Peripheral Computer Complex (PCC)

The pe riph e ral computer complex (PPC) in conjunction with th e main computer complex (MCC) forms th e central co mpute r main complex (CCC) of the MADAP system. Th e peripheral computer complex in the normal sta te of operation performs the following functions: - Interpretatio n and processing of controller input messages; - Formating of data for messages to be displayed on electronic data disp lays (EDDs) and synthetic dynamic data disp lays (S DDs) ; - Fo rmating a nd output of messages to be printed on flight progress strips; - Repetitive output of data to the display system; - Programme supe rvising functions including re-configu ra ti on of th e syste m; - Othe r miscellaneous fu nctions such as for the fligh t data section (FDS), supervisor technica l monitoring and contro l desk (TMCD) and training sections. The pe riph e ra l computing compl ex consists o f fou r TR 86 (PC 1), ea ch o ne of which is ca p abl e of se rving two ope ra-

Deb ugg ing o f the first progro ms on M oin Computer N o . l of the Centrol Computer Co mplex o n Si te.

tional control sectors. To enhance system reliability two additional TR 86 (PC 2) computers are provided as standby computers. A standby (PC 2) computer can replace any one of the operational peripheral (PC l) computers. In the case of the main computer complex, one state of operation is possible, i.e. the one in which the full system functions, i.e. the normal state of operation,_ is provided. The normal state of operation may be ensured by either the operational main computer (MC 1), or in the event of failure of this computer, by the standby main computer (MC 2). In the event of failure of the standby main computer an emergency state of operation is provided, which is ensured by either one of the two standby TR 86 peripheral (PC 2) computers. In the emergency state of operation one of the standby TR 86 (PC 2) computers is required to carry out the following functions: - Flight plan processing (FPP) without automatic flight plan updating and without correlation of radar and flight plan positions; - Association of individual SSR identity codes and aircraft callsigns; - Partial processing of radar data, i.e. coordinate conversion to a common reference system; - Routing of radar data to the four operational computers, up to four radar pictures to one computer. In the emergency state of operation the operational (PC l ) computers, each feeding two control sectors, carry out the fo llowing functions: - Separate radar data processing without systematic tracking; - Establishment of a composite data plot p resentation per control sector, comprising plots from up to three radars; - All other functions as in the normal s tate but with a decreased picture repetition rate in the event of a peripheral computer be in g overloaded.

View of the external memory uni ts of th e M A DAP M o in Computer Comp lex.

The configuration of each of the four operational peripheral computers is identical. In addition to the central processor unit with internal core store of 64K of 24-bit words the following features are provided: - standard input/output channel for connecting on-line to the two main computers, the two peripheral computers, the magnetic tape unit (for legal record) and the off-line devices, card reader, card punch and high speed printer; - central processor channel for connecting two teleprinters, and paper tape reader and paper tape punch; - four display data channels for connecting each of four display drive units for the EDDs and SDDs. The configuration of the two standby peripheral computers (PC 2) are identical. In addition to the facilities provided for the operational peripheral computers the standby computer has the following: - one standard input/output channel to make possible a connection to two SSP l 00-86 disc units each providing additional capacity of 2 million bytes, data transfer rate of 300K byte per sec. and average access time of 17.2 msec.: - one multiplexer input/output channel for connection to the medium and high speed digital links (l ,200 to 2,400 bits/s); - eighteen simplex data transfer units for the eighteen radar data links (2,400 bits/ s); - 6 duplex data transfer units to connect 6 high speed data links to adjacent ATS and Met. centres (l ,200 or 2,400 bits/s). Each of th e six peripheral computers are permanently and separa tely connected with each of the main computers MC l and MC 2 by coaxial coble. The replacement of a normally operational computer PC l by one of the standby co mputers PC 2 and vice verso is achieved by informing the computers (either automatically or manually) to load and execute another set of programmes and to select

another set of coaxial cable connections. The change-over is performed by de-energizing the original set of permanent cables and by switching to a new set. Operator Input and Data Display System (ODS) The operator input and data display system (ODS) permits a conversational mode of operation between the air traffic control personnel and eventually certain technical maintenance personnel and the central computer complex (CCC). The system consists of input devices to gain access to the computer such as position entry and touch input devices, keyboards and teleprinters. These devices provide a means of obtaining all information available in the central computer complex relating to traffic within the entire Maastricht system area. It also contains display and printing units which are capable of providing to the operator in tabular, pictorial or printed form information relating to the aircraft in the system. The quantity, extent, content, scale and brightness of this information is largely at the discretion of the individual operator. The ODS may be functionally divided into the following parts: - seven control sectors each containing planning control section, executive control section and tracker position; - flight data section (FDS} which handles manually those flight plans and associated messages between the Maastricht UAC and external ATS units communicated through the AFTN, telephone or R/T channels; - watch supervisor position; - meteorological section; - training section; - technical monitoring and control desk; - maintenance display test bench. In all, these positions contain input and output devices which total as follows: - electronic data displays (EDD) . . . . . . . . . . . . . . . . . . 92 - synthetic dynamic data displays (SOD) . . . . . . . . . . . . 47 - alphanumeric function keyboards (KYB) . . . . . . . . . . 16 - display control panels . . . . . . . . . . . . . . . . . . . . . . . . . . 46 - touch input devices (TIO) . .. . . . . . . . .. . . . . . . . . . . . . 46 - position designation and entry devices (RLB) . . . . . . 46 - flight progress strip printers . . . . . . . . . . . . . . . . . . . . 18 - page printers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 - input/output teleprinters . . . . . . . . . . . . . . . . . . . . . . . . 3 - technical control teleprinters . . . . . . . . . . . . . . . . . . . . 10 - status display and picture selection panel . . . . . . . . 1 Up to two control sectors may be allocated to each peripheral computer PC 1. The training and maintenance display test bench are allocated to one of the standby computers PC 2. The displays (EDDs and SDDs) within a sector ore driven by a display drive unit (DOU) which transforms the binary information coming from the computer channel into analog information for distribution to the various displays. This unit consists of two individual drives each of which normally drives half the displays in a sector at the required refresh rate (20 Hz.) In the event of a failure of one of these drives the remaining drive is arranged to feed all the displays in a sector at a reduced refresh rate, thus providing a high degree of availability. The display units show synthetic information only and are therefore free of noise and clutter. There is no raw radar in the system and the operators view screens that are refreshed at a high repetition rate providing a bright and clear picture thus reducing operator fatigue.

Inputs from operator devices demanding information from the system such as keyboards, touch input and position designation (rolling ball} devices are connected to the peripheral computer (PC) through telegraph multiplexers which are duplicated for each channel. Programmes The software system takes into account the existence of two computer hardware levels, i.e. the main computer (MC) level and the peripheral computer (PC) level. The programmes enable various tasks to be performed by the system, the main task being the discharge of a number of operational functions which are listed below: - conflict detection in the planning phase based on flight plans for traffic in level flight on air routes; - calculation from flight plan data of estimated time of arrival at designated reporting points; - printing of flight progress strips; - coordinate conversion to a common reference and geographical projection of all radar plots received; - selection of plots within defined extraction areas for storage and display; - formulation and processing of tracks and track positions from defined primary and/or secondary radar plots; - calculation from current flight plan data of the present and predicted position of an aircraft on the basis of aircraft performance and meteorological conditions; - correlation of radar track position with flight plan information and the ensuring of automatic updating of the stored flight plan data; - display of flight data on electronic data displays (EDD) at various operating positions according to a predetermined programme or as requested by the controller; - display of radar and other data, including data derived from flight plan information on synthetic dynamic data displays (SOD} at various operating positions according to a predetermined programme or as requested by the controller; - provision for accepting from operating positions new or revised information; - direct digital exchange of information with neighbouring centres; - miscellaneous tasks such as recording of data for statistical and legal purposes, reconfiguration of the system in case of failure of the computers. The system functions, i.e. those relating to the processing of the flight plans and radar data, are carried out at the main computer level whilst the display functions are carried out at the peripheral computer level. The software system also provides for the two operational states, the normal state and the emergency state, which are determined by the availability of the computers at the two hardware computer levels. In the emergency state none of the main computers is available and reduced system and display functions are shared by the peripheral computers as already described. In addition, the system may perform a number of offline functions such as compiling, assembling, programme testing and simulation. The operational functions are controlled by an on-line supervisor programme written in the base language, whilst the off-line programmes are controlled by an off-line supervisor. The programmes for MADAP have a modular structure. This enables programmes to be built for various opera27

tional states of the system by the use of the same modules, thus reducing programming effort. It also enables modifications to be made to a given module without undue effect on other parts of the programme. The modules may be compiled separately. The module is a self-contained unit of an ideal size of 1,000 to 4,000 machine instructions and carries out a group of related specific functions. Modules communicate Âˇwith each other through messages which pass through the supervisor programme. There are in all approximately fifty modules in the MADAP programme which are labelled by a distinctive reference system.

The Consoles for the Operating Positions The consoles for the operating positions are constructed on a modular basis. Two basic sizes are available of widths 125 cm and 75 cm. From these two basic sizes any number of consoles can be put together to form console suites for any number of operators. Further flexibility is possible by the fact that the modularity of the design permits the construction of a console suitable for any given function. This has been arranged by the sectional construction of the console so that it consists of (a) desk unit, (b) a desk top unit, (c) a super-structure unit and (d) an overhead unit. Thus an executive control group which provides for two operators may be constructed in the following manner: 1. 2 Desk units comprising one 125 cm desk unit and one 7S cm desk unit side by side; 2. 3 Desk top units comprising two 7S cm display panels and a SO cm communications panel; 3. 3 superstructure units comprising two 75 cm SDD units and one SO cm EDD unit; 4. 3 Overhead units consisting of two 7S cm communication unit and one 50 cm communication unit. There ore in all six different types of console groups which include executive control and tracking, planning control, training, watch supervisor, MET/AIS section, and flight data section, in the MADAP system all of which are constructed from the modular console units. The operations room provides in all for 78 working positions.

The Technical Monitoring and Control Desk (TMCD) A position is provided in the equipment room which permits the monitoring and control of the whole MADAP

Letters to the Editor Dear Mr. Editor, Permit me through the columns of the "Controller" to express our sincere appreciation of the wonderful response from all our colleagues in IFATCA to a recent appeal by the Irish Association. The response from Member Associations was most gratifying and helpful, and emphasises the wonderful potential of our International Federation in fostering our common aims for mutual advancement. Again, on behalf of the Irish Controllers may I say thank you all or to quote an old Irish expression used to convey superlative gratitude "Go roibh mile maith agaibh go leir". Yours sincerely, M. J. Kerin, Hon. Gen. Secretary, Irish Association.

system. The space provided also allows for the installation of technical control and monitoring equipment of other systems that are being installed in the centre thus enabling the monitoring and control of the whole Maastricht UAC complex to be effected from a central position. The monitoring facilities provided ore as follows: - the display in mimic form of equipment configurations in operation; - the examination, by switching to a monitor display unit, of the information shown on any EDD or SDD; - the indication of the fault conditions detected by the different on-line test programmes on the monitor display and by printout on the console typewriters. The position also permits the control of the whole system so as to effect rapid restoration of service in the event of the unserviceability of any part of the system. A number of system failures are dealt with by automatic switch-over which will be displayed at the desk. However the TMCD enables manual control to be taken at any time. It is possible by means of the control typewriters to enter the programme modifications necessary to isolate the faulty elements and introduce standby equipment into operation. Hardware re-configurations are possible by the operation of keys and input devices. Off-line tests on the system may also be carried out from the TMCD.

The Implementation Programme The contract for the supply and installation of the MADAP system was let on the 19 December, 1968. The intention is to commence an operational service, after a period of evaluation and familiarisation by the end of 1972. The MADAP system is an ambitious project with a tight time scale for its successful implementation. The Eurocontrol Agency is aware of the difficult task that it has been set by the Permanent Commission of Ministers. It is a project that aims at a significant advance in the application of automation to air traffic control and as such it has created a wide interest both within and outside the member states of the Eurocontrol Organization. The Agency is resolved to discharge the heavy responsibility that it has been given to the utmost of its ability and is confident of the successful outcome of the project. EURO

Book Review Jahrbuch der Luft- und Raumfahrt 1971 German Aerospace Annual

Compiled and edited by Dr. Karl-Ferdinand Reuss. 500 pages (14,8 X 21 cm), plastic cover. Published by Sudwestdeutsche Verlagsanstalt, 6800 Mannheim, F.R.G., P.O. Box 2007. OM 27,80, incl. tax. The 1971 issue of the "Johrbuch der Luft- und Raumfahrt" marks the 20th anniversary of this well-known German Aerospace Annual. Originally a slim pocket book, it has developed, through 20 years of faithful reporting on German aviation and space activities and by continuously providing reliable address and reference material on the German aerospace community, into a certain kind of post-war aviation history and an impressive reference document. In addition to such familiar features as systematic classification of subject matter, reliability, timeliness, location aids, etc., tri-lingual lists of contents and chapter headings have been introduced into the 1971 edition of the "Reuss", for the convenience of the non-German speaking readers. EH

Pity the Air Traffic Controller when they come in like this An exaggerated picture perhaps but not for long. Air Traffic is increasing so fast that the controller's job needs an entirely new appraisal. And one of the thin gs we've got to look at is ~he method of training controllers. Is it adequate to meet the demands of th e Seventies? The flexibility of th e Ferranti Radar Simulator provides the answer-now and for the future. It gives the trainee controller pract~ce in Air ~r~ffic Control under con ditions so realistic that when he takes over control of real aircraft he'll not only be fully trained but confident too.

pigit~l techniques readily permit mod1fi_ca t10ns to accommodate chan ges in a v.:ide range of parameters, including a ircraft type and speed radar a n d geographic~l data. Raw 'radar or fully synthetic output can be provided to dr ive any type o~ display. The system can therefore simulate new aircraft and procedural techniques not even envisaged at this stage. Fer!anti have . the capability and exper1e~ce to ~es1_g~ and develop a system to suit any individual requirements. If you have an ATC training or evaluation problem talk to Ferranti.

FERRANTI

ATC training systems Ferranti Limited , Digital Systems Department, Bracknell, Berkshire, England . RG

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AIR TRAFFIC CONTROL SYSTEMS - DEFENCE SYSTEMS :- COMMAND AND CONTROL SYSTEMS Selenia's digital display systems cover a wide field of applications ranging from Air Defence (NADGE) to Air Traffic Control (ATCAS). As well as displays Selenia produces computers, primary and secondary radar extractors, simulators and digital interface equipment both for ground and shipborne installation.

selenia digital display SyslelDS TNE~~~~~IE

ELETTRONICHE. ASSOCIATE SpA SYSTEMS DIVISION, ROME-ITALY