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Aviation History
1947
1947 - 0394.PDF
FLIGHT MARCH 2OTH, 1947 Radar in Civil Aviation Uses and Possibilities : Grouping and Analysis of Equipment IN his paper of the above title, readbefore the Bristol Branch of theRoyal Aeronautical Society on Feb- ruary 18th, Mr. F. R. Willis, Superin-tendent of Signals Planning for B.O.A.C., ably summarized the qualities of manyol tin- radio/radar aids available, or shortly to become available, to civil avia-tion. Of particular value and interest is bis personal experience of their operationand of requirements of the minute which have enabled him to comment upon andassess the value of each aid where another could only have described its form andcapacity. • Extracts from his lecture follow: For convenience air navigation wasusually divided into three phases: (1) Final approach and landing.(2) Short-distance navigation. (3) Long- distance navigation. These were conveniently related to thezones of influence and air traffic control, namely, the airfield, approach, and airzones. With them might be coupled the avoidance ol collision.The major responsibility vested in traffic control was to ensure safe and ex-peditious air movement by regulation of traffic flow based on a knowledge of posi-tion of aircraft and route conditions. Its proper operation depended considerablyupon the navigational aids and communi- cations systems. For their share in de-termining the limits set to operating stan- dards the radio/radar aids might bequalified thus: (1) Final approach aids— major effects on regularity and punctu-ality. (2) Short-distance aids—major effect on punctuality, second-order effecton regularity. (3) Long-distance aids— second-order effects on regularity andpunctuality. It was only a question of time until compulsory carriage of finalapproach and short-distance aids became necessary on transport aircraft operatingon specified, routes under instrument flight rules. Final Approach Aids Paradoxically, though an approach aidhelped a pilot to land, it did not neces- sarily contribute a great deal to the taskof putting the wheels on the ground. No approach systems, radar or radio, wereyet regarded as suitable for the blind landing of passenger-carrying civil air-craft. Factors governing airfield capacitywere the speed and certainty with which an aircraft could let down, which de-pended upon: (1) Thff efficiency of the v/ ^ Typical B.A.B.S. displays. (Left*Aircraft about 2 deg. starboard of runway, dashes I sector, heading port.(Right) Aircraft about 2 deg. port of runway, dots I sector, heading star-board. - blind-approach aids and the weatherminima in force. (2) The number of runways available and whether separaterunways were reserved for landing and take-off. (3) Taxying arrangements.(J)) Efficiency of aircraft communica- tions. Radar aids concerned were B.A.B.S.(Beam Approach Beacon System) and G.C.A. (Ground Controlled Approach),the former air and the latter ground in- terpreted. Neither had been named byP.I.C.A.O. as international standards, but both would see a great deal of ser- By F. R. WILLIS vice. Rebecca equipment (the airborneB.A.B.S. set) was bulky and required operation outside the cockpit from wherethe information displayed was interpreted to the pilot over the inter-phone system.This demanded implicit confidence in his B.A.B.S. operator on the part of thepilot, and in civil flying, where it was difficult to group flying staff in fixedcrews, intensive practice was necessary. affected by siting difficulties and tidalvariations. The system was now figur- ing in a priority programme of installa-tion along the principal Commonwealth air routes. Mr. Willis then went on to describe theG.C.A. talk-down system which had been recommended as a supplementary aid atairfields where local conditions warranted its use. The two elements of G.C.A.were the search system and the precision system for highly directional beamsating on wavelengths of 3 to 10 c metres. The P.P.I, of the search systemwould locate an aircraft within the radius of 30 miles at heights up to 4,000ft, andthe two beams of the precision system, inching in the vertical. and horizontalplanes, provided a magnified view of a relatively small sector 20 deg wide and7 deg high for the maximum radius of 10 miles. At a range oi a mile cr less, anaircraft's deviation from the proper descent path could be detected within afew feet. The interior of the control trailer hadpositions for five operators, two for the azimuth and elevation tubes, two others G.C.A. mobile operations room. The photograph was taken during a recent demonstration at London Airport, and the aircraft is a B.O.A.C. Dakota. A pilot's miniature cathode-ray indi-cator had been developed, and also a meter indication, track being given onone instrument and distance in miles on another. Both these ideas had merit,but neither had been tested under airline conditions. The second required anextra radar unit to transform the cathode-ray picture into signals suitablefor actuating meters. One apparent disadvantage ofB.A.B.S. was absence of a glide path, but to some extent this was compensatedby the distance-measuring fac'lities. These were specially useful to flyingboats, since the operation of glide paths or marker beacons at marine airports was known as traffic director and aircraft1selector each with a P.P.I., and the con- troller in the centre with meters indicat-ing the aircraft's deviation from tbe descent path. Recent improvements had includedseparation of the search and precision systems and permanent installation of theformer in airfield control towers. Instead of separate precision tubes for azimuthand elevation a combined display had been evolved. This had reduced thenumber of highly trained crew required, which hitherto had been at least five menper watch. G.C.A. achieved much popularityduring the war and required no special
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