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Aviation History
1985
1985 - 0025.PDF
sales potential could also rise as a -Result. Photographs do not do justice to the Astra. They tend to emphasise the more obvious areas of Westwind ancestry, such as the rear fuselage and tail. In fact, little remains of the Westwind design except the family resemblance. A new aerofoil and winglets, intro duced with the Mark II version of the straight-wing Westwind, had clearly taken that design (originally inherited from Aero Commander via Rockwell) as far as it would go in aerodynamic efficiency. New wing Accordingly, development plans were announced for the high-aspect-ratio swept-wing Astra at the 1979 NBAA show. Work began on the full-scale mock- up in 1980, while 500 engineers, with their 70 CAD/CAM terminals, got to work on the first flying aircraft and static test specimen in April 1982. The objective was k to retain the proven low-drag eliptical fuselage cross-section of the Westwind (while providing more headroom) but to —ombine it with ultra-modern wing aero dynamics. The new wing uses thin, aft-loaded sections developed "in-house" by IAI. It confers Mach 0-82 cruise performance, and has already enabled the aircraft to be dived beyond its MMO of 0-85 to Mach 0-88 by project pilot Hagai Koren. Correlation between the actual aircraft and windtunnel results (including load distribution over the wing) has been good, and IAI states confidently that the Astra meets all the most important goals, although telemetry aerials make the first two aircraft slightly "dirty". The wing features automatic outboard leading-edge slats which deploy whenever angle of attack exceeds 8° at an airspeed of less than 250kt or Mach 0-5. This ensures a consistent inboard stall with no wing drop, and (because of the consequent loss of lift forward of the e.g. at the stall) a natural stall recovery is assured even with aft stick held by the pilot. Stall warn ing buffet is natural, and no stick shakers or pushers are expected to be required. Slat actuation systems will no doubt come in for particular scrutiny by the certifica tion authorities. The ailerons remain effective through out the stall. They are actuated hydrau- lically (with manual reversion) because —as at least one major manufacturer found to his cost—aft loaded aerofoils tend to produce heavily loaded ailerons. Astra's roll control has no "q" feel, and is described as sensitive but not to the point of being tiresome. Elevator and rudder are manually operated by pushrod, with geared tabs to reduce the loads. General handling qualities are said to be better than expected from tunnel tests, and are superior to those of the simulator which IAI has been using as a devel opment aid. Dutch roll is well contained, and a single yaw damper may be adequate because its loss may not necessitate a descent to altitudes where terrain or higher fuel burn become problematic. On take-off, rotation forces are lower than predicted, even at forward e.g., while land ings can be flattering because ground effect is substantial. Extensive windtunnel testing of Astra models obviously paid handsome divi dends because the aerodynamic con figuration was virtually frozen last month after only 265 flight hours on two aircraft, with very few, minor, modi fications. Tunnel testing involved about half a dozen models of various scales being flown in five different windtunnels, including the NLR high-speed facility in Holland, an LTV tunnel in the United States, and a high-speed tunnel at BAe Weybridge. Icing tests were carried out at Above Astra stands higher than the Westwinds and features a supercritical swept wing, but retains a family resemblance FLIGHT International, 5 January 1985 23
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