Jetrader - November/December 2008 - (Page 28)

when cleaned up in ﬂight. Only seven were built, and wood was the principal material in its construction. It had four DH 525hp inverted V-12 engines, constant speed propellers, slotted ﬂ aps and retractable landing gear. The major innovation was the molded-composite fuselage shell with an end-grain balsa-wood core and birch plywood outer skins. The wing was made in one piece with a laminated spruce-spar and birch skin. Other than the engine installation there were few fasteners, it was mainly glued together. Designed by A.E. Hagg as a long-range mail plane, the two prototypes were damaged—one in March 1938 with a forced wheels-up landing and the second with a broken back during overload landing trials. Both were repaired. Imperial Airways, the forerunner of B.O.A.C., took ﬁve with a 22-seat layout between October 1938 and June 1939 for the European routes. Meanwhile the two prototypes were used from 1940 by the RAF as a shuttle service to Iceland after the army occupied it to forestall a rumored plan of a German invasion. By 1943 there were only two survivors, the others being lost in landing accidents and enemy action, notably the blitz on Bristol in September 1940. The remaining two were scrapped in September 1943. The two major problems were the excessive ﬂexing of the airframe in ﬂight and the deterioration of the structure from rot. Although it was not a commercial success, its elegant method of construction was to be the basis for the de Havilland submission of a design for a twin-engined ﬁghter bomber in response to the Air Ministry’s P.13/36 speciﬁcation. The result was the Avro Lancaster and Handley Page Halifax four-engine heavy bombers and the two-man crew DH Mosquito. It was one of the fastest aircraft in WWII before the advent of jet ﬁghters. The bomber version had a top speed of 419 mph at 28,500 feet and a still air range of 1,470 miles, more than enough for its regular night sorties to Berlin carrying a 4,000 lb “cookie” blockbuster, shaped like a large propane tank. It carried no armament but was equipped with the extremely accurate H2S radar bombing aid. Although designed as an unarmed bomber, the Air Ministry initially ordered only a photo reconnaissance version with The de Havilland Mosquito Merlin 21s, which had a single-stage supercharger. Later PR models had the Merlin 114 engine with a two-speed, twostage supercharger, a pressurized cockpit and an operating altitude of 40,000 feet. It was capable of 425 mph. Rough Materials So why was wood the principal material used in its construction? Aluminum alloys were in huge demand for the production of ﬁghters and bombers in wartime Britain, whereas spruce and birch plywood were relatively plentiful. Further, trained metal workers were likewise engaged in the assembly of metal aircraft, but woodworkers were readily available, and de Havilland had developed the use of plywood to generate a smooth, rigid-butlight structure in its DH 88 Comet racer, which won the England to Melbourne, Australia, race in 1934, (see: Jetrader, November 2005). For the Albatross, the 10 mm thick end-grain balsa core was sandwiched between 2 mm birch skins and proved that a low-drag, smooth airframe could be produced. The Mosquito fuselage was split longitudinally and the internal frames, 2 mm inner skin, balsa core and outer skin were laid up, glued and formed on wood male plugs. Each half then had all ﬁttings, control runs, electrics and hydraulic plumbing installed before gluing them together. Prior to this, a bottom section was cut away from each half and used as the bomb bay doors. The two, one-piece laminated spruce spars were covered with stressed birch ply; two layers on the top surface and one on the bottom, with each engine radiator inside the wing leading edge between the fuselage and engine nacelle. The result was a light, rigid, smooth-surface airframe of extremely low drag and high-speed capability. Production was at a high rate and distributed among the furniture industries, car manufacturers, aircraft manufactures Airspeed and Percival and de Havilland’s own shadow factory tucked well away from likely bombing targets. The bomber version initially carried a 2,000 lb bomb in the bay and a 250 lb one on a hard point under each wing. The precision of its bombing capability was legendary. Outrunning the Messerschmitt ﬁghters, the unarmed Mosquitos destroyed Gestapo barracks, records and interrogation buildings in a number of cities in occupied Europe. This included their HQ in Oslo and the Schott optical works at Jena. The bay was capable of carrying a 3,000 lb bomb plus two 500 lb bombs under wing, or the 4,000 lb “cookie” after the doors were modiﬁed, which then became the standard version. With the advent of the Foke-Wulf Fw 190 ﬁghter and its slightly superior speed over the thenversion of the Mosquito, it was switched from day to night bombing and navigated to its target by the intersection of two converging radio beams from stations in 28 The ofﬁcial publication of the International Society of Transport Aircraft Trading

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Jertrader - November/December 2008 A Message from the President Contents Calendar/News Q%2BA: Richard Anderson Building a Strong Foundation Post Prague Aircraft Appraisals From the ISTAT Foundation Aviation History

Jetrader - November/December 2008

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