Wednesday, October 8, 2014
De Havilland Mosquito B Mk IV
On 21 June 1941 the Air Ministry ordered that the last 10 Mosquitoes, ordered as photo-reconnaissance aircraft, should be converted to bombers. These 10 aircraft were part of the original 1 March 1940 production order and became the B Mk IV Series 1. W4052 was to be the prototype and flew for the first time on 8 September 1941.
The bomber prototype led to the B Mk IV, of which 273 were built: apart from the 10 Series 1s, all of the rest were built as Series 2s with extended nacelles, revised exhaust manifolds, with integrated flame dampers, and larger tailplanes. Series 2 bombers also differed from the Series 1 in having a larger bomb bay to increase the payload to four 500 lb (230 kg) bombs, instead of the four 250 pounds (110 kg) bombs of Series 1. This was made possible by shortening the tail of the 500 pounds (230 kg) bomb so that these four larger weapons could be carried (or a 2,000 lb (920;kg) total load). The B Mk IV entered service in May 1942 with 105 Squadron.
In April 1943 it was decided to convert a B Mk IV to carry a 4,000 lb (1,812 kg), thin-cased high explosive bomb (nicknamed "Cookie"). The conversion, including modified bomb bay suspension arrangements, bulged bomb bay doors and fairings, was relatively straightforward, and 54 B.IVs were subsequently modified and distributed to squadrons of RAF Bomber Command's Light Night Striking Force. 27 B Mk IVs were later converted for special operations with the Highball anti-shipping weapon, and were used by 618 Squadron, formed in April 1943 specifically to use this weapon. A B Mk IV, DK290 was initially used as a trials aircraft for the bomb, followed by DZ471,530 and 533. The B Mk IV had a maximum speed of 380 mph (610 km/h), a cruising speed of 265 mph (426 km/h), ceiling of 34,000 ft (10,000 m), a range of 2,040 nmi (3,780 km), and a climb rate of 2,500 ft per minute (762 m).