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Aviation History
1947
1947 - 1374.PDF
i84 FLIGHT The covered the Gipsy Major iC engine, which has estab- lished a wonderful reputation for reliability (1,500 hours between overhauls), and it was but natural that the de Havilland enterprise should decide to design the new trainer around this well-tried engine. By marrying up-to- date airframe design to this engine it has been possible to achieve a performance more in keeping with modern re- quirements than was available in the good old Tiger. Preliminary Studies • The idea of the Chipmunk originated as far back as 1945, and much time was spent on the mock-up stage. Special attention was devoted to such features as view, cockpit layout, controls, and accessibility. Not until all these had been thoroughly examined was actual construction begun. This proceeded rapidly, and by May 22nd, 1946, the prototype machine was ready and made its first flight, piloted by Mr. W. P. I. Fillingham. Much test and de- velopment flying has been done since then, and the second machine is now in England, where it has been demonstrated extensively. In view of its function as a primary trainer, the wing loading of the Chipmunk has been kept low (10.3 lb/sq ft), and to get good stalling characteristics and effective aileron control, the aspect ratio decided upon was 6.82 : 1. The taper ratio is moderate at 2.1 : 1 but suffi- ciently high to give not only a pleasing appearance but also a good lift distribution. The aerodynamic design of the wing is compounded of two basic aerofoil sections: N.A.C.A.2415 over the inner portions and U.S.A.35B towards the tips. There is" thus an increasing camber near the tips. Slotted ailerons were chosen for light and responsive control. In- board of the ailerons are the slotted flaps which give the machine a use- fully steep glide path when in the fully-down position. Without the flaps the Chipmunk has a very flat glide* path. Reference has been made to the close study made of the cockpit lay- out. The maximum width of the fuselage is 3oin, and the well- raised canopy gives a fuselage depth of 54m to the top of the canopy as well as affording an excel- main engine bearers are welded tubes and earn rubber-bush mountings at front (right) and rear (left). D.H. CHIPMUNK PRIMARY TRAINER140 h.p. Gipsy Major IC Dimensions Length o.a. 25ft 8in Wing span 34ft 4inHeight 7ft I in Wing area (gross) 172.5 sq ft Mean chord 5ft Oin Incidence ™ 2 deg Dihedral 5 degAspect ratio 6.82 : I Taper ratio 2.1 : I Weights Empty weight ... 1,175 Ib Gross weight 1,780 Ib Wing loading 10.3 Ib/sq ft Power loading 14.3 Ib/h.p. Performance Max. speed, sea level ... ... ... ... ... 141 m.p.h. Cruising speed, sea level ... ... ... ... ... 124 m.p.h. Stalling speed with flaps 40 m.p.h. Stalling speed without flaps ... ... ... ... 45 m.p.h. Initial rate of climb 900 ft/min Service ceiling 19,000ft Absolute ceiling 21,200ft Still-air range (approx.) 500 miles Air miles per gallon (cruising) 20 DETACHABLE METAL WING TIP FABRIC COVERED METAL LEADING EDGE TAIL CONE CONTAINING BALLAST WEIGHT
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