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Aviation History
1960
1960 - 2423.PDF
FLIGHT, 28 October 1960 667 Two printers produce flight progress strips in blue or yellowfor east-bound or west-bound aircraft. Any deviation from pre- dicted performance can be inserted by the controller into thecomputer by keyboard and a new batch of flight progress strips is immediately printed. A permanent record is provided by thepaper strip from the input printer, which also provides a means of visually checking the computer inputs. The film and its com-mentary clearly showed how all these processes were performed at Schiphol. Copies are available in a number of languages. Phase 2 of SATCO mainly provides for automatic conflictsearch and the display of flight progress strip information by electro-mechanical indicators instead of conventional printedpaper strips. Radar inputs would also be possible, so that aircraft could be identified and tracked and flight information up-datedmuch more often than with position-reporting. Automatic track- ing radars and air-to-ground data links could also be added toprovide even more direct surveillance of flight paths and closer control. Some time after the introduction of Phase 2, conflictsearch and warning would be supplemented by conflict resolution, which would compute avoidance procedures. A Signaal engineer foresaw the use of radar displays on which a computed position and identification of an aircraft would bedisplayed together with actual radar returns. The operator could then position a symbol over the actual aircraft echo, press a buttonand thereby insert a correction to the computer if necessary. The audience very soon raised the question of reversion tomanual operation in case of failure and the Signaal engineer stated that a quarter of the elements in the present SATCO computerwere intended for checking and had no calculating function. Two-channel computation would also be employed, so that ifone channel failed a second would continue working, though overall capacity would be reduced. Console failure could beallowed for by provision of a second console with a manual changeover switch.Altogether 14 ways of displaying letters and figures from the computer had been investigated and the present electro-mechanicalsystem did ensure that the last "good" indications would remain in view after display failure so that the complete situation picturewould remain and only the up-dating function be lost. The degree of redundancy to be provided in a system of this kind was, accord-ing to Signaal, a difficult problem and one which was dictated mainly by economic considerations. RADAR IN AIR TRAFFIC CONTROL THE Guild's own paper, entitled The Application of Radar toAir Traffic Control, was prepared by a group of members and read by Sqn Ldr K. B. Crosbie, a member of the RAF UnitedKingdom Air Traffic Service. The paper considered the present situation over the United Kingdom under the three main head-ings of civil operations, military operations and the limitations of the radar system itself. Civil and military operations were carriedout in accordance with different rules and with very different operational requirements. The civil operator wanted establishedand protected routes for pre-planned operations, but the military commander required a large element of tactical freedom with theminimum of pre-planning. The conflict was not only civil/military, but also military/military. The latter problem could be overcome by centralizing control. Groups of adjacent airfields were in fact already beingcontrolled as complexes. But a common controlling medium was required to overcome civil/military conflict and the Guild con-sidered that the only known common factor for the foreseeable future was radar. Sqn Ldr Crosbie noted that there were at present some 300radars in the United Kingdom, almost half of which had ranges of more than 50 miles and height coverage of 15,000ft or more.Radar coverage was one thing, but utilizing it for aircraft control was another. In addition, there were probably between 300 and400 aircraft airborne over South-East England at any one time, with horizontal and vertical performances varying from 120kt to600kt and from 300ft/min to 3,000ft/min. The fact that most British airways were two-directional meant that a radar con-troller would have to resolve a built-in collision hazard before he could perform his main task of controlling climb and descentthrough occupied levels. The pattern was in fact twofold. First, radar control had to be used in support of a planned proceduralsystem, later also employing a precise navigation aid; secondly air space outside the route system required radar as the primecontrolling agent. The Guild suggested accordingly that both civil and militaryradar controllers required radar cover between 5,000ft and 25,000ft, backed up where necessary by airfield radars. Universalcoverage of the UK was then required from 25,000ft to over 60,000ft, to be used in combined civil and military centres. Based on this assessment, the Guild's proposal visualized radarsspecifically designed and sited for traffic control; they specified a Type 1 radar with 150 n.m. and 5,000 to 25,000ft cover, whileType 2 should cover from 15,000ft to 60,000ft with a positive range of 250 n.m. Both types should satisfy a number of requirements. Theyshould be designed for 24hr operation with sufficient redundancy for routine maintenance and radar or power failure. Echoes fromweather and ground features should be eliminated, but weather returns should be available to allow vectoring round storms.External interference should be eliminated, and to this end a central licensing authority should be established to ensure diatnew radars did not cause interference with radars already operating nearby. Tangential and blind velocity fades should be eliminated fromMTI systems. The aerial should turn at not less than 10 r.p.m. Much research was necessary to assist controllers in directingavoiding action for high-speed aircraft. The minimum beam width should be 2° in order to provide a sufficiently large radar returnon the screen, and the penalty of reduced discrimination would have to be accepted. This stipulation was made in relation tocurrently available radar and did not take into account synthetic display-brightening methods. Coverage in the operational areashould be absolutely gap-free. Automatic height-extraction should be provided, not so muchin order to indicate the height of each aircraft as to make it possible to select given height bands for display. A choice of video mapsshould be available to assist procedural guidance. Automatic identification, which pre-supposed the use of secondary radar,was desirable, but international agreement was obviously required to coyer the airborne equipment. It should be possible to transferidentified radar information automatically from one controller to another. Radar consoles should be unit constructed and thecontroller should be able to select his aerial head; console controls would require special study. This specification implied no criticism of manufacturers, butwas intended as a guide for equipment directly designed for ATC work. The aerials should be sited to provide suitable coverage andthe radar information remoted to centres which were junction points for ATC communications and where radar informationcould be matched against all other relevant information. Type 1 radars should therefore be provided in the civil/military centresat London, Preston and Prestwick and military airways-penetra- tion could be controlled from these points. Spare coverage couldbe used for military operations. In addition, three military radar areas should cover the Vale of York, North-East England, South-East Scotland, East Anglia and South and South-West England. Type 2 radar information need only be remoted to two of thecombined air traffic centres. On this radar framework a system compatible with present and future civil and military operationsshould be built up. Finally, the Guild stated that any automation or computersintroduced into die control organization must leave the human controller as the main "thinking machine." THE SEVEN SINS OF INTERNATIONAL ATC CPEAKING, as he pointed out, in a private capacity, Capt^ Lincoln Lee of BOAC delivered an incisive and amusing indictment of seven "sins" which he had noticed during manyyears of operation on almost every BOAC route. The sins were poor organization and equipment, non standardization, badtiming, poor nomenclature, waste, poor discipline and mistakes. Capt Lee pointed out that he was not an ATC expert but a pilotand that despite the "seven sins" he had great respect for the work done by controllers. Neither were his remarks directed atany one country or any one place. The examples he gave of the seven sins are briefly summarized below. No 1 Sin: Poor organization and equipment. All too often,point-to-point communication was non-existent or broke down, so that air-to-ground radio frequencies were at times choked withpoint-to-point messages. Sometimes the facilities were simply not used so that a centre was surprised at the arrival in its areaof a particular aircraft. Capt Lee cited several cases of lack of co-ordination between centres and approach controls and ofindecision about which frequency was to be used for a given control phase. Lengthy and complex flight clearances often tiedup R/T channels unnecessarily and a series of pre-set routes with code names might replace ad hoc clearances. Routes withoutfacilities, unreliable facilities and over-optimistic use of radar were also snags. No 2 Sin: Non-standardization. In this category Capt Leeput upper-air quadrantal levels still not generally agreed; metres
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