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Aviation History
1961
1961 - 0241.PDF
FLIGHT, 24 February 1961 241 into its slowest automatically-controlled speed and on its abilityto continue the climb or find its way back to the landing site in case of engine failure. The solution depends in this case largelyupon the performance of the helicopter. Take-offs in rearward flight to allow an immediate normal landing in case of enginefailure look less attractive in the case of a low ceiling, because the pilot would have to make a complete transition from rearwardflight to the hover, and then into forward flight, entirely on instruments or autopilot. It is conceivable that the rearwardclimb-out might be made up the glide-slope of the precision aid, the transition being made by coming part of the way down theglide-slope again and then virtually taking overshoot action into a normal forward climb-out. It would seem more practical toensure the ability to make the standard climb to obstacle clearance height regardless of engine failure and then to be able to make acircuit and standard approach with an engine out. Such problems obviously become less severe with three or four-enginedhelicopters. Fig 5 illustrates the possible configuration of an approach inceiling-zero conditions, the actual visibility minima being dictated by the ability of the heliport to operate efficiently. The approachpath from cruising height would be the same as before, except that the helicopter—and it would almost inevitably be a three- orfour-engined type, able to hover outside the ground-cushion with an engine out—would make the transition to a blind hover at 100ftor 200ft. The final descent would be made vertically over a radio beacon and the pilot would probably first have accurate visualcontact with the ground just before touching down. The high- intensity light pattern would be largely obscured from viewbeneath the helicopter airframe until the last moment. There is a strong case for relying on high-intensity lighting andvisual contact for the final landing in order to avoid highly complex and probably uneconomical equipment. The final distanceto be covered and the duration of visual flight would be very short; and high-intensity lighting can probably penetrate light fog con-ditions below which it would rarely be necessary to operate. The improvement in regularity achieved by automating the final 100ydand 30ft or so of the approach would hardly warrant the con- siderable performance margin and special equipment involved. BEA Planning British European Airways' Helicopter Experi-mental Unit, based at Gatwick, has since 1947 been engaged in research into the requirements of helicopters in scheduledpassenger operation and has completed considerable investiga- tions of the equipment available and the control techniques whichwould be required. Members of the unit have probably done more practical work on IFR operations than anyone else andhave actually made equipment proposals for specific aircraft. Their conclusions indicate that new and specialized equipment isrequired in almost every phase of IFR helicopter operations, except possibly for communications. During the night mail flightsin East Anglia in 1949 they were the first to fit gyro instruments and fly at night without visual reference. In the very early days they realized the need for autostabiliza-tion as a basic part of the control system. They now consider that an electro-mechanical system intended only for stabilization, andnot for flight-path control as well, can be integrally designed with the primary controls; and that, if it is duplicated, it can be fitted A typical European city-centre heliport, the Sabena terminal in the Allee Varte, Brussels. The farther S-58 carries flotation gsar, not inflated, on its wheels CRUISE PRECISION APPROACH SLOW-SPEED AUTOMATIC PARTIAL TRANSITION 150ft CLOUD-BASE CRUISE, HOVERAT TRANSITION IOO 2Q0H AUTOMATIC DESCENT TO VISUAL CONTACT Fig 4 (upper drawing) and fig 5 show respectively the flight profiles for IFR operation with visual hover and touch-down, and extreme IFR operation with blind transition, hover and vertical descent to visual contact with the heliport lighting Model of one-tenth of the proposed replacement for Covent Garden Market, which would be built over King's Cross, London, railway sidings and surmounted by an 800ft X 1,200ft heliport. (Architects, C. W. Glover & Partners)
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