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The Blackburn B-48 Firecrest, given the SBAC designation YA.1, was a single-engine naval strike fighter built by Blackburn Aircraft for service with the British Fleet Air Arm during World War II. It was a development of the troubled Firebrand, designed to Air Ministry Specification S.28/43, for an improved aircraft more suited to carrier operations. Three prototypes were ordered with the company designation of B-48 and the informal name of "Firecrest", but only two of them actually flew. The development of the aircraft was prolonged by significant design changes and slow deliveries of components, but the determination by the Ministry of Supply in 1946 that the airframe did not meet the requirements for a strike fighter doomed the aircraft. Construction of two of the prototypes was continued to gain flight-test data and the third was allocated to strength testing. The two flying aircraft were sold back to Blackburn in 1950 for disposal and the other aircraft survived until 1952. ==Design== The Firebrand required significant effort by Blackburn to produce a useful aircraft and the first discussions on a redesign of the aircraft with a laminar-flow wing took place in September 1943. The new wing was estimated to reduce the weight of the wing by 700 lb (318 kg) and increase the aircraft speed by 13 mph (21 km/h). The extent of redesign increased and this led to a new fuselage and other improvements.〔Buttler 2004, pp. 181–182.〕 In October 1943, Blackburn's design staff, led by G.E. Petty, started work on this development of the Firebrand which lead to Specification S.28/43 being issued by the Air Ministry on 26 February 1944 covering the new aircraft.〔Jackson 1968, p. 452.〕〔Mason 1992, pp. 330–331.〕 The specification was designed around a Bristol Centaurus 77 radial engine with contra-rotating propellers that allowed the size of the rudder to be reduced.〔Buttler 1999, p. 55〕 The new design, given the company designation B-48, was known unofficially by Blackburn as the "Firecrest" but always known by its specification number by the Air Ministry and Navy. It was a low-winged, single-seat, all-metal monoplane. Aft of the cockpit the fuselage was an oval-shaped stressed-skin semi-monocoque, but forward it had a circular-section, tubular-steel frame. The cockpit of the Firecrest was moved forward and raised the pilot's position so that he now looked over the leading edge, and down the nose.〔 The canopy was adapted from the Hawker Tempest fighter.〔 In the rear fuselage was a single fuel tank with two fuel tank in the centre wing section. The aircraft had a redesigned, thinner, inverted gull wing of laminar flow aerofoil section. The wing consisted of a two-spar centre section with just over 6.5 degrees of anhedral and outer panels with 9 degrees of dihedral.〔Buttler 1999, pp. 55–57.〕 It could be hydraulically folded in two places to allow more compact storage in the hangar decks of aircraft carriers. Four Fowler flaps were fitted to give good low-speed handling for landing and the wing had retractable dive brakes on both surfaces.〔 In the course of the redesign the structure was simplified which reduced weight by 1,400 lb (635 kg) and even after the fuel capacity was increased by the gross weight was still less than that of the Firebrand.〔Buttler 2004, p. 181.〕 Work on two prototypes was authorised in November 1943, but proposals for alternative engines delayed progress. In 1945, it was decided that as well as adding another Centaurus-engined prototype, there should be three prototypes with the Napier E.122 (a development of the Sabre) as Specification S.10/45. The Ministry believed that this would enable Blackburn to develop their knowledge of aerodynamic and structure design and support the engine development at Napier. However, it was found that the S.10/45 aircraft could only be balanced if the E.122 powerplant was placed behind the pilot. The necessary redesign and weight increase, coupled with the limited funds available to the Royal Navy, meant that it could no longer be justified and the S.10/45 was cancelled on 8 October. While in final design, the Centaurus 77 engine with contra-rotating propellers was cancelled in January 1946 and a conventional Centaurus 57 was substituted. This engine was found to require flexible mounts and was modified into the Centaurus 59. The vertical stabiliser and rudder had to be enlarged from to counteract the new engine's torque. In September 1946 a strength analysis conducted by the Ministry of Supply revealed that the aircraft would require strengthening to serve as a strike fighter and that a costly redesign would be required to bring it up to requirements. This would have made it comparable in weight and performance to the Westland Wyvern which had already flown so no contract was placed for production aircraft.〔Buttler 1999, pp. 56–58.〕 Delayed by the late delivery of its propeller, the first prototype was rolled out at Brough in February 1947 and then taken by road to RAF Leconfield where it made its maiden flight on 1 April that year. All three prototypes were completed by the end of September and the third prototype had been modified to reduce the outer-wing dihedral to 3 degrees. Both the second and third prototypes remained unflown when the Ministry of Supply ordered that flying be ceased and work on the aircraft be stopped. Later in the month, however, the third prototype was allocated to tests of powered aileron controls, as testing of the first prototype had shown that while adequate at cruise speed, the ailerons were heavy both at low and high speed. The second prototype was allocated to structural testing.〔Buttler 1999, pp. 57–58.〕 The third prototype made its maiden flight in early 1948, but the pace of the flight testing was leisurely with only 7 hours and 40 minutes completed by 30 November, over half of which was connected with air show performances. Testing concluded in March 1949 when the officer in charge concluded that there was no further purpose to the tests.〔Buttler 1999, pp. 58–59.〕 While the Firecrest was faster than the Firebrand, and gave its pilot a much better view from the cockpit, it was otherwise disappointing, with test pilot and naval aviator Captain Eric Brown claiming that the Firecrest was even less manoeuvrable than the sluggish Firebrand, while the powered ailerons gave lumpy controls, leading to instability in turbulent air.〔Brown 1978, p. 47.〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Blackburn Firecrest」の詳細全文を読む スポンサード リンク
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