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Aviation History
1947
1947 - 1424.PDF
-216 FLIGHT AUGUST 28TH, 1947 Fig. /. Typical air cooled cyMidsr assembly with vertical push rods. Fig. 2. Hemispherical head with inclined valves and more complex push-rod arrangement. A New Ideal it is on present traditional lines, with tractor nacelles mounted on the leading edge of the aircraft. This layout of the conventional twin engine type of machine is always problematical in the event of one engine failing, and the drag is too high and means using a lot of horse-power. The American Beechcraft Executor, with its twin-engine radials, traditional nacelles and a total horse-power of goo, would definitely meet this specification in most respects, but the weight and size, first cost and operational costs of this aircraft would be far too high to go down in this country or meet my friends' specification of costs. A traditional machine of this kind would have a first cost of ^15,000 in England, and the running cost would be con- siderably higher than their top limit. It is the same old story of the American and British motor car; the "large, powerful " way is the easier way, but it is not the most economical and most efficient, and you pay for extrava- gance much more heavily in the air than on land. 200 m.p.h. on 500 h.p. Starting with the power plant, which fundamentally affects the prime and running costs of the machine, we have got to do 200 m.p.h. cruising speed, with 500 h.p. total and not with 000 h.p. The point at issue is: can this be done? The answer is definitely " No " with normal engine nacelles and present engine technique in these sizes, but I suggest it can be done by suppressing the traditional nacelle on the leading edge of the wing, putting the engines out of the way and driving through shafting. The pro- posed aircraft would, broadly speaking, have the following characteristics: All-up weight Cruising h.p. 70 per cent of T.O. Total wing area Wing loading Power loading (TO. power) . . Total drag coefficient, cruising Propeller efficiency, cruising . . Cruising speed at 350 h.p Can a really safe aircraft be made? The answer to this is, of course, relative, but in my opinion no safe enough aircraft to meet this specification can be produced with the traditional layout of power plant because, with one engine out, there is always a couple which lequires addi- tional skill of the pilot Under the lower flying speeds caused by the elimination of one engine, this may produce bad flying characteristics of the machine Here again, in my opinion, the answer is to take the propeller from the conventional place where there must be a couple, and make the thrust central. There is no other possible solution, in my opinion, and 5,000 lb. J50 h.p. at 10,oooft. 280 sq ft. 18 II.'sq ft. 10 lb/h.p. 0.019 80 per cent. 200 m.p.h. this must be tackled as an entirely new layout if my friends' ideal specification is ever going to be realized. It seems a fairly long development job and a considerable expendi- ture in money. Other possible means of* getting the required condition of safety following an engine failure is, I believe, the layout for a new charter aircraft lecently proposed by an eminent British aircraft designer. This introduces three engines, and whereas it is a distinct possibility and meets most of the requirements in regard to safety iir flying, it is not, in my opinion, the ideal way of doing the job. It must be more expensive in first cost and maintenance, and it must have a higher drag, but it may well be a sound interim measure, pending the correct solution. It would require a considerably high total h.p. The same remarks, to a greater extent, apply to a four-engine machine. In producing what I term the real solution, I think it is essential to have practical twin-engine reliability and so arrange the mechanical. layout that in the event of one engine breaking down it does not immobilize the common gear box and thereby put the other engine out of com- mission. It is well-nigh impossible to provide a ioo per cent solution in this respect, but I think it is feasible to do so to the tune of 90 per cent. Dealing first, therefore, with the power plant for this ideal machine (because this I suggest, is a corner-stone of the whole job), it would seem that a completely new engine is required, and that it must be more highly rated than the accepted light aircraft engine of to-day. This need not entail a sacrifice in reliability or an increase in specific cost. It is essential, however, to take advantage of the general advance in piston-engine tech- nique of the last decade, and to employ less bulky and clumsy engines of about 25 per cent less swept volume. This, properly designed and developed, should give greater reliability and lower fuel consumption than at Fig. 6. Suggested air- craft with two engines in the nose and shaft drive to contra-rotating ll in the tail.
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