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Aviation History
1940
1940 - 0526.PDF
i66 FEBRUARY 22, 1940 German reconnaissance machines would have kept the French ports under constant observation by day and by night. The landings did not all take place in the dark- ness, but one would have expected a liberal use of para- chute flares, and certainly a really formidable effort by German bombers to interfere with the landings, even at a cost of considerable losses. Heavy blows struck against the B.E.F. would have done more for the Ger- man cause than any slaughter in London or Birming- ham could do. In fact, before the war, many military authorities held that a landing within reach of a hostile bomber force was an impossible operation of war. It has, none the less, been carried out, and the reason is still a matter for speculation. The danger to us is that we may think that because the Luftwaffe has once been incredibly remiss, it will remain equally unenterprising in the future. That would be "wishful thinking." Our only safe policy is to assume that our enemies will do their utmost. Plain Engineering, but . . .F ROM the correspondence which has appeared in Flight recently, it seems obvious that it is fairly well agreed that very soon we shall have to face up to the problems of shaft transmission. There is less unanimity about the manner in which it should be used. Several arrangements are possible, such as tandem en- gines in the fuselage, with oppositely rotating airscrews in the nose ; or tandem engines in the fuselage with right-angle shaft drive to outboard tractor or pusher airscrews on the wings. If pushers are used, the air- screw shafts themselves will have to be fairly long, and there will be an unpleasant overhang of shafting from the rear spar. There are designers who consider the shaft worth while, even in the single-engined type such as the new American Bell " Airacobra" or XP-39. It is often argued, mostly by people who have not given the subject much thought, that the design of such shafting is plain, straightforward engineering. So it may be, but experiments made hitherto do not promise trouble-free development. Possibly the explanation is that they were '' before their time," but against that must be set the fact that the powers that had to be transmitted in those early examples were far lower than those we are now con- templating. We happen to know of one experimental machine built recently in which there was considerable trouble with the long airscrew shafts. Ultimately a coupling with the right "period" was produced, and the trouble of snapping shafts disappeared ; but in spite of being plain engineering, the task took a long time. Dive FightersI T was demonstrated in Spain that a strong fighter biplane could bring down much faster machines by gaining speed in a dive. This fact, which has been exploited to the full by the protagonists of light, low- powered fighters, does not justify the building of slow defensive machines, but it emphasises that, even in these days, diving ability is a great asset, for, although a typical fighter has at least 40 or 50 m.p.h. in hand over a contemporary "evasive" bomber, a high-flying defender capable of long, fast dives enjoys an extra advantage over the raider. There is another reason for insistence on good diving qualities in the fighter; this was well brought out when the French adopted the Curtiss Hawk 75A. A Curtiss test pilot was asked to do one really fast demonstration dive (actually over 575 m.p.h. was attained) to satisfy the French observers that the Hawk could engage a dive-bomber after it had begun its dive. Already there are indications that before long we shall see fighters fitted with diving brakes. TEN YEARS BETWEEN : Below is the " 400 m.p.h.-plus " Bell XP-39, or Airacobra, single-seater fighter which has a shaft drive from its centrally-mounted Allison engine. On left is the Westland fighter, built to an Air Ministry specification issued in 1930, which had a similar power plant installation. The Westland was armed with four machine guns ; so is the Bell, though these only supplement a 37 mm. shell-gun. On the other hand Westlands installed the first gun of this bore on a single-seater fighter years ago. We are sure that the Bell Aircraft Corporation, which deserves great credit for having developed such a remarkable machine (it has been ordered in quantity by the U.S. Army Air Corps), will forgive us for pointing out these historical facts.
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