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Aviation History
1948
1948 - 0083.PDF
JANUARY I5TH, 1948 FLIGHT Blending with the snow-covered fields below, as if in winter camouflage, the A.W.52 sails over the Warwickshire countryside. On the Wing Possible layout of a long-range pure-jet transport based on the A.W.52 design. aft trimming device which will not impair the lightnessof the primary flying controls. Stick-free stability has been the aim from the start. One of the first things to beestablished during early flight trials will be the degree of automatic movement of the correctors relative to the flap,and the speed with which they are to move. Completely automatic movement of the correctors to follow the pilot'sgfieration of the flap is not foreseen, and the present twelve • jrees maximum upwardMovement of the corrector is produced half automaticallyand half by the movement of the corrector lever. In the caseof the A.W.52 glider, correc- tor movement at the rate of1 degree per second was found to give the best results, and itis expected that it will be settled at the same rate in thecase of the powered 52. The control lever in the cockpit re-sembles a multi-position flap lever, with thumb release button on top and each quadrantposition representing a degree movement of the corrector. In view of the very large speed range of the A.W.52(100-500 m.p.h.) and the permitted range of e.g. position, the problem of selecting corrector angles and speed of move-ment will be very much greater than for the glider. It has been said that, one of the major weaknesses of all theall-wing design is the closeness of the fore-and-aft e.g. limits. This is to some extent true, but in the case of theA.W.52 a movement of the order of 7 per cent of the mean chord, that is, about 12 inches, is .allowed at present.This is rather more than half that of a conventional civil the 52 to remove the boundary layer immediately in frontof the control surfaces by suction. A series of narrow slots (Jin wide) are located spanwise in front of the correctorat approximately half chord. This, incidentally, coincides rouehly with the position where the wing ceases to bedesigned for laminar flow. So far, suction has not been used on the 52, but its effect was examined on the glider,which was similarly provided. The suction is obtained from the intake ducts of the Nenes, and the degree of suctionis controlled by pairs of flaps in these intakes. When the system is put into operation, the suction flaps will be under automatic control fromboth the throttle and the elevators. In general terms, the purpose-is to increase the amount of suction at the slots progres-sively as the stick is moved aft of the neutral position and/orthe throttle position reduced to 8,000 r.p.m. engine speed orless. In the extreme case of closed throttle, and stick wellback (as for instance on land- ing), the flaps are at their full-open position and suction is at a maximum, while for the extreme use of either elevator or throttle separately, theflaps answer with a movement up to 40 per cent open. The use of full suction, 60-70 cu ft/sec, results in theloss of some 300 lb of thrust from the Nenes. In the ca?° of the stick being moved far back with throttle full open,as might occur in a tight turn or possibly on a take-off, some 50 per cent of the total suction could be applied. Theresulting loss in thrust, although it occurs at a critical time, is for practical purposes small enough to be ignored. Thesuction ducts from the two Nenes are interconnected by a balance pipe, and the system includes a plenum or set- transDort of to-day. The Skymaster, with a movement of tling chamber in the wing beneath the slots on each side.16 to .32, is something of an exception. To overcome the tendency of swept-back wing tips tostall before the rest of the wing, provision was made on Ultimately the removal of the boundary layer from the entire wing may be attempted, using gas turbine power plants drawing their whole air supply from this source to
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