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Aviation History
1958
1958 - 0245.PDF
21 February 1958 259 The Control of Air Traffic A. Cdre. Mann's Brancker Memorial Lecture to the Institute of Transport R A. Cdre. W. E. G. Mann, C.B., C.B.E., D.F.C., who is remembered as a pioneer of inverted formation aerobatics in the inter-war years, held a succession of responsible signals posts during the war. He went over to duties in civil aviation in 1945, and is now Director-General of Navigational Services, M.T.C.A. LAST week we briefly summarized the 15th Brancker MemorialLecture delivered at the Institute of Transport in London on February 10. The origins, development and future requirements of Air TrafficControl, as set out by the lecturer, A. Cdre. Mann, are here summarized more fully in the form of selected quotations. ECORDS show that [by 1933] the Air Traffic ControlService at Croydon was earning a high reputation . . . Approximately 11,000 aircraft were contacted and, moreimportant still, over 1,000 position fixes and 6,400 bearings were passed. It is of interest that in 1957 some 300,000 aircraft, flyingover the same area, passed over 800,000 position reports by radio-telephony." "A committee set up in 1935 under the chairmanship of SirHenry Maybury, to consider the development of civil aviation in the United Kingdom, looked into the difficulties the air trafficcontrol service was experiencing in maintaining safety . . . The Maybury committee recommended that a comprehensive airtraffic control organization and all radio facilities should be pro- vided, maintained and operated by the Government. It alsoenvisaged that in the course of time it would be possible for the burden [of considerable cost] to be transferred to aviation itself. . . The question of who should ultimately bear the cost has not yet been resolved . . . The International Civil Aviation Organiza-tion is to discuss this problem later in the year." Development "The tremendous advances in the development of communica-tions systems and navigational aids during the war were to prove of great significance to the rapid development of post-war trans-port . . . Radio-telephone communications of very high frequency at last made possible clear and direct speech between captainsand controllers. This was a great step forward." "A G.C.A. ground control approach equipment . . . wasintroduced at London Airport during 1947 . . . The potentialities of longer-range radar for general surveillance were also appreci-ated and an experimental service, probably one of the first to be used solely for civil aviation, was introduced in January 1948,using Microwave Early Warning Radar war-time equipment." "With American experience as a guide a network of nationalairways was introduced in August 1950, and later extended throughout Western Europe.""The high speeds of modern aircraft do not give a pilot suffici- ent time to take adequate avoiding action . . . Therefore we shallhave to control the movements of all high-speed aircraft all the time as well as other aircraft when traffic density reaches acertain figure." "A controller is most efficient when he is busy, but in theinterests of safety he must not be fully extended for more than very short periods. The exercise of air traffic control from a FlightProgress Board is a most exacting task, and with exceptionally heavy traffic efficiency can fall off rapidly. This display systemno longer meets requirements . . . too much information has to be carried in the controller's head. Therefore a greatly improvedmethod of displaying the traffic situation and its movement in three dimensions is most urgently required." "Radar serves us well so long as its main function is simplyone of confirming to the controller that all aircraft at the same height are safely separated by at least five miles. What the radarcontroller cannot do as a rule is accept responsibility for main- taining these reduced distances, and also for guiding and virtuallynavigating individual aircraft en route." "Air traffic control has to use enormous separation standards[over the North Atlantic] due to the very low standards of navi- gational accuracy possible and to difficult radio communicationconditions. In this area the controller has to provide a longi- tudinal separation of 30 minutes flying time and a lateral separationof 120 nautical miles . . . Many captains now wish to fly along similar tracks at similar heights. Moreover, most flights arescheduled to leave at about the same time. This canalizing of traffic, together with these separation standards, either delaysdepartures or forces aircraft to fly at low uneconomical heights on too many occasions." The Future "To illustrate the impact of jet aircraft and the difficulties thatconfront air traffic control, let us consider the kind of flight plan the operator and captain would like to file. We will assume theflight is from Central Europe to America. Without doubt the captain would want to follow an optimum economic path in bothhorizontal and vertical planes, probably passing over other traffic centres while climbing at a rate which cannot be specified pre-cisely, to a height which can only be indicated generally, and through traffic which would not have taken off until after he wasairborne. At some point he would wish to start his descent through traffic which departed from termini near his destinationseveral hours after he left the ground in Europe. Although he would not wish to cruise at any fixed height, he would requirehis flight path to be clear of all other traffic. Today no such flight plan could be given a safe clearance by control, and I doubtif it will ever be possible to do so. I trust that the operators of jet aircraft have taken account of this." "The requirements of turbo-propeller aircraft, fortunately, aresomewhat more flexible, but the question that must be faced is: can regular safe and economic operations be carried out by air-craft with such rigid operating requirements, or should the designers of aircraft and engines be asked to provide aircraft withmore flexible operating characteristics?" "Because of the advantages of radar, I think the best solutionwould be to construct four long-range stations which with aero- drome radars should give cover . . . over the controlled air spacein the United Kingdom, from a height of 5,000ft to at least 30,000ft. An essential development would be the introduction ofsecondary radar . . . with transponder beacons in aircraft." "Clearly ... horizonal separations must be considerably reduced. . . aircraft must dierefore be navigated much more accurately. For this reason, the United Kingdom, with the support of BritishEuropean Airways, has consistently advocated for many years the international adoption of the British Decca Navigator System inhigh traffic density areas." "The United Kingdom . . . has also undertaken the testingand evaluation of a ground-based long-range system known as Dectra. A number of Atlantic operators will soon be carryingand testing Dectra equipment . . . Early tests . . . hold out hope of an accuracy of five miles in mid-Atlantic." "The Doppler system would be complementary . . . and wouldbe of the greatest value ... in areas where traffic is light and where ground-based aids cannot be made available." "The form and type of data to be transmitted over the world'saeronautical communication systems must soon be standardized if full advantage is to be taken of the possibilities of electronicmemory devices and computers." "With the varying speeds of aircraft and the fact that twosucceeding aircraft may be coming from different stacks, the approach radar controller is given the formidable task of position-ing aircraft correctly in time and space for the final approach to the runway. Thus, apart from the need for more accurate naviga-tion, it would be most helpful if all aircraft could fly at a common approach speed. Unfortunately, it is probable that die wing tipvortices of certain new aircraft about to be introduced will set up turbulence which may persist for some time in calm air toan extent that separations would have to be increased and there- fore the landing rate correspondingly reduced." "If airports are to be economically operated to their maximumcapacity the design of aircraft should permit them to conform to a reasonable range of approach speeds . . . Our aim should be60 landings per runway per hour in fair weather, and at least 40 in bad weather. It seems to me [that such factors] are notalways taken fully into account by the designers and operators of transport aircraft." "Automatic blind landings are possible today but it will bemany years before they will be reliable enough for air transport work." "I doubt whether heavy STOL and VTOL aircraft could beaccepted at an airport without reducing the movement rate of more conventional aircraft. I have some misgivings at theapproach speeds of 150 kt or more of some of the jet aircraft soon coming into service ... Is there not a happy mean between anapproach ... of zero knots [VTOL] and one of 160 knots? If aircraft could approach at a common speed of the order of 80 to100 knots higher landing rates and increased airport capacities could be safely achieved. Both airports and transport aircraftcould then be operated more economically."
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