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Aviation History
1940
1940 - 0213.PDF
JANUARY 25, 1940. of the dive the target is 1,500 m. away and at the end only 600 m. The release of the bomb and the pull-out (Phase 4) is said to occupy 2 sec. and the spiral get-away and gradual climb (Phase 5) 90 seconds. It is considered that during Phases 1 and 5 the dive- bomber has complete manoeuvrability and is therefore diffi- cult to hit with anti-aircraft guns. The sudden reduction in speed in the second phase is also disconcerting to the artillery. It is in Phase 3, when the flight path of the dive-bomber must necessarily almost coincide with the tra- jectory of the bullets and shells, that the chances of its being hit are greatest. Phase 4 is said to be too short for consideration by the anti-aircraft artillery. Testing in America Dive-bombing and the pilots who do it have been heavily over-drarnatised by pen and camera, mainly because the 9-G '' pull-outs required until fairly recently of prototypes for the U.S. Navy sometimes subjected test pilots to rather unpleasant strains. Referring to this test a writer in an American contemporary once said: '' We are told that in one of these sharp pull-outs from a terminal velocity dive to meet the current rigid Navy requirements the pilot is absolutely without control as to the amount of force of pull-out he puts on a ship, as the only physical or mental reaction possible under these circumstances is to decide when he is going to pull out, pray, pull like hell, pass out, and hope that when he does come to he and the airplane will still be intact." To minimise the effects of sharp pull-outs American test pilots sometimes gird themselves with a corset-like belt and tie a scarf tightly round their throats. There is a natural desire to yell during the dive and this is also considered beneficial. An American Service pilot, discussing dive-bombing, writes: '' The average pilot is uncomfortable only in pro- longed dives from extremely high altitudes ; under io,oooft. the sensation is exhilarating, even in a terminal velocity dive. No other sport offers such a feeling of projection, for the very attitude of your 'plane, which becomes only an extension of yourself, is the factor which determines your accuracy." He goes on to say: "A lot of bilge has been written about the tremendous bodily stresses that pilots undergo in this work, but the fact is that the human body can be subjected to stresses that will wrench the wings off the sturdiest airplane." The Fokker G. 1 multiple-purpose machine can be fitted withdiving brakes shown above in their "normal flight" and "diving" positions. It is said that German dive-bombing pilots used to adopt a crouching position to minimise the effect of " G " during the pull-out, a special sighting window being fitted in the bottom of the fuselage. Certainly this position enables a man to withstand a greater acceleration, but it is not so efficient as the prone position. Design Difficulties Design requirements as affecting dive-bombers are often very difficult, for, apart from considerations of structure, aerodynamics and view, it is often necessary to limit dimensions and landing speeds to such figures as can be tolerated for carrier operation and to provide for folding wings and alternative loadings. A dive-bomber must be strong enough to withstand sharp pull-outs ; manoeuvrable enough to keep enemy A.A. gunners guessing; the pilot's view over the nose must be especially good ; and provision must be made, if the machine is a single- engined type and the bomb is carried beneath the fuselage, for the projectile to be guided clear of the airscrew. The twin-engined layout not only gives the pilot a better outlook forward, but facilitates bomb displacement. Diving brakes, typical examples of which will be discussed later, are On the left is the Douglas (Northrop)DB-19 dive-bomber which, like the Brewster XSBA-i shown below, has" double-split " trailing edge flaps for restricting its speed. The Brewster hasinternal stowage for a single 500-lb. bomb.
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