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Aviation History
1946
1946 - 1229.PDF
JUNE 20m, 1946 FLIGHT 633 CORRESPONDENCE The Editor does not hold himself responsible for the views expressed by correspondents. The names and addresses of the writers, not necessarily for publication, must in all cases accompany letters. PICKING THE WAR-WINNERS Halifax Performance on One EngineF reference to Philip Simpson's letter giving his list of alliedwar-winners in Flight, May 23rd, I feel I must take him up on his statement that the Lancaster is the only" multi " able to fly and maintain height on one engine. This feat was accomplished on a Halifax II (Merlin 20) withfull petrol load of 1,882 gallons and full crew, flown by Sqn. Ldr. P. Dobsou, at Riccall, Yorks, in 1943—June, if I remem-Y-ber correctly. Photographic proof is available, and as a point of interesta copy of the original was published in your journal. Having said my piece, may I thank you for providing anexcellent journal; also please will '' Indicator'' write up the handling of the Halifax. JOSEPH W. HUTTON. UNUSUAL LANDINGS Going Backwards in a Spitfire '"THE series of articles on " Britain's Test Pilots " is a really-*- nice way to pay tribute to perhaps the most deserving of the flying profession. In this way it is possible to have aminiature study of the history of aviation at least in the last decade or so. The recent article about J. K. Quill is of excep-tional interest even to those who have only worked on the beloved "Spit." However, I can think of at least one "pro-fessional" aviator who could dispute his claim to the record lor going backwards in a Spitfire. In March, 1942, a medical officer was attempting to land aSpitfire Vb which was in a slight state of disrepair. This Spitfire put down rather fast in a carefully executed landing,but took exception to the bumps of Martlesham and went into reverse, shedding wheels, flaps, rudder, ailerons, etc., at some-thing around 100 m.p.h. The name of the pilot was, I believe, F/O. Noel Jackson, who, it is said, sent the ambulance backwith the remark that he always walked back from his own accidents on the basis that any landing you can walk awayfrom is a. good one ! A. J. MILNER. ULTRA-LIGHT AIRCRAFT Victim of Short-sighted Obstruction YET again do we see the Government stranglehold on a limbof the aircraft industry reducing a potential export trade to yet another example of British slowness on the uptake, andleaving many of our people in a state of frustrated dissatisfac- tion. I refer to the ultra-light aircraft, for which " at present "the Government has refused to issue flying permits. As a Government alleged to be dedicated to the cause of theless wealthy in this country, surely they should be glad to see the ownership of an aircraft, at present possible only for thewell-to-do, brought within reach of those not so fortunately placed. The cost of aircraft is proportional to speed, range and carry-ing capacity. It is therefore obvious that a small, slow air- craft, carrying two persons at the most, powered by a very lowhorse-power engine and with limited range could be made avail- able at a very low price as compared with the " light " aircraftffitvv selling. *' Brought out by firms renowned for the production of reliableand economical aircraft, the ultra-light aircraft would, besides filling a wide gap in the home market, undoubtedly prove ofgreat advantage, both in prestige and purse, if exported in good time and sufficient quantity.In answer to as yet unexpressed objections, may I say that I see no reason why this aircraft should not prove as safe asany other, if, built by our own incomparable engineers, it was designed to carefully considered specifications and subjected tostringent C. of A. examinations. But what is the use of hoping ? We are tied by our ownfolly, and it threatens to be years before the industry will be allowed to run itself as only it knows how, before Governmentslearn that guidance and assistance will bring- the country more prosperity than thick-headed and short-sighted obstruction anddelay. Until then it is going to be an uphill fight, but I for one feelthat the industry will win through, will find its way somehow through the maze of controls to prosperity, but always must itlook back to the period after the war as a time of frustration and lost opportunity. B. E. J. GARMESON. THE JAMESON AIRCRAFT ENGINE Crankshaft Arrangement in Flat-fours yL'R correspondent, "M.I.A.E." Flight, June 6th), infers-*- a little doubt about the progressive variation of mixture charge obtained. It is not easy to assess the matter from astudy of the design, but one may at least assume that the effect would be limited to an engine of the type and preciselayout shown (or possibly to a radial engine suitably planned), but that the same result would not be achieved with an in-line unit. Charge stratification has been advanced as one ot the main reasons for the extraordinary results obtained withthe Aspin rotary combustion chamber, the chamber itself act- ing as a centrifuge; this appears to be a system far moreflexible in its application to any type of engine. However, I am mainly moved to write not on this pointbut on the statement in the original description that " physical- design . . . conforms to accepted flat-four practice."Except for low-speed stationary or industrial engines, I should imagine that a two-throw 180 degree crankshaft cannot beregarded as accepted practice, owing to the severity of the couple which cannot be wholly corrected by crankshaft balanceweights. The Jowett flat-four car engine, which is the only successfulBritish example of the type in this field, has a three-throw crankshaft; the makers have been producing flat twins for 40years (180 degree two-throw), but the wider spacing of the big ends in the four precluded the use of that type of shaft.Aspin's first light aircraft engine was a flat four with two-throw 180 degree crank, and it was very soon changed to three-throwto get rid of the couple In Germany the original Volkswagen design had a two-throw crankshaft in its flat-four engine, butthis was discarded in the development stage and a three-throw crank substituted. Therefore, it would seem that if a mechani-cally unobjectionable flat-four engine is required, "accepted practice " is the use of a three-throw crankshaft. DONALD H. SMITH, M.I.A.E. SPEED AND THRUST Calculating Jet Power OutputM AY an interested amateur exhibit his ignorance by askingfor an explanation of something doubtless so simple as to make him look ridiculous? The trouble started seriously when I read " Indicator's"article "Speed and Thrust" in Flight, January 17th, 1946.. and has gone on ever since. Why can nobody explain satis-factorily why jet engine capability is measured in lb thrust and piston engine capability in horse power? Agreed that with a constant thrust resulting from the enginepower is directly proportional to the speed in the direction of application of the thrust, for power = thrust times speed. Butnow consider a piston engine being run up. If it is developing 2,000 h.p., then there must be both a thrust and a speed.The thrust you can feel by standing behind the aircraft, but where is the speed? Is it the speed of the backward-movingslipstream, or is it the angular velocity of the airscrew blades? If the latter, then the thrust on which you would have tocalculate is the torque resistance due to drag on the airscrew blades. But whichever of the two it is, don't they bothapply equally to the jet engine? For you still have your back- ward-moving mass of air (and then some) and your rotationalvelocity. Ah, you say, but you don't worry about the torque resistanceto the motion of the jet engine rotor for it doesn't apply. Well, doesn't it? There must be a resistance, or there wouldbe nothing to stop the rotor from flying off to top revs all the time, even at J throttle, except bearing friction and moment ofinertia, and you would be getting something for nothing. My case, then, is that the two engines are equivalent to oneanother. For take an aircraft flying at 300 m.p.h. i.a.s., and whichever engine you have in it, provided the aircraft is flyings. and 1., and not accelerating, the backward thrust of the air- stream from the engine is surely equal and opposite to the totaldrag of the aircraft—or isn't it? Apply the same reasoning at any speed, including standing still, and don't you arrive atthe conclusion that at zero speed you have zero thrust, which is nonsense? And there are other anomalies Obviously, 1 am talking through the back of my neck, butwhere have I gone astray3 BROWN JOB.
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