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The Yakovlev Yak-1000 was a Soviet supersonic technology demonstrator intended to evaluate the aerodynamic layout and field performance of the cropped delta wing discussed in captured German documents in combination with the new Lyulka AL-5 turbojet. The tandem undercarriage proved to be unsatisfactory and there were serious flight stability problems related to the delta wing, enough so that it never flew after an accident during taxiing tests. ==Development== A June 1950 Council of Ministers directive ordered Yakovlev to develop a supersonic fighter that used the Lyul'ka AL-5 axial compressor turbojet. Based on a recommendation from one of TsAGI aerodynamicists, Yakovlev was directed to use the rhomboid or cropped delta-shaped wing covered in captured German research.〔Gordon, pp. 184–85〕 The directive was extremely ambitious as it required the maximum speed to be Mach 1.7 at a time when the world speed record was barely over the sound barrier.〔(【引用サイトリンク】title=Speed Record Club )〕 This requirement had to be revised when the AL-5 was delayed and a substitute engine had to be chosen. No other Soviet turbojet offered the same sort of power as the AL-5 so the project was recast as a technology demonstrator to evaluate the novel wing aerodynamics. The Klimov RD-500 was chosen and the maximum speed was expected to be at a take-off weight of .〔 The Yak-1000 had a circular-section, semi-monocoque fuselage with the engine air intake in the nose. The engine was mounted behind the pressurized cockpit and exhausted through a long tailpipe in the rear fuselage. Two air brakes were fitted on the underside of the rear fuselage. Forward and rear fuel tanks held and respectively.〔 The entire rear fuselage and tail was removable to allow access to the engine.〔Gunston 1995, p. 482〕 The three-spar wings were the most significant new feature on the Yak-1000. Small and rhomboid-shaped, they had an aspect ratio of only 1.46 with 60° leading-edge sweepback with 51°11' sweepback at quarter chord. The thickness/chord ratio was a remarkable 3.4% at the root and 4.5% at the tip. Skin was 1.5mm thick Duralumin. The trailing edge was swept forward 11° and consisted of a full-span flap with inset ailerons.〔Gordon, pp. 185, 187〕〔Gunston, 1997〕 The delta shaped horizontal stabilizer was set low on the tail and was shaped much like the wing, with 5% thickness. The rudder was tiny, as were the mass-balanced elevators. The tandem "velosipednoye" (bicycle) undercarriage legs, similar to those of the Yak-50, retracted aft, although the forward wheel remained exposed when retracted. Small outrigger struts retracted aft into underwing fairings set at mid-span. On the ground the Yak-1000 had a pronounced nose-high attitude, and the single nose wheel was steerable.〔Gordon, pp. 185, 187〕〔 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「Yakovlev Yak-1000」の詳細全文を読む スポンサード リンク
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