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Aviation History
1970
1970 - 0385.PDF
f FLIGHT International, S March 1970 343 ^s.'-ifii;;^..,.:,;:',;:::;,:; \ PRIVATE FLYING 1970 . . (ate *v*l*v; « :«»>« | "Three chiaracteristics of specific airplanes are considered to be unacceptable. (1) violent elevator force reversal exhibited by one airplane at reduced load factor in the landing con figuration, (2) the power-on stall characteristics of two air craft—one that experiences a rapid roll-off that often results in excessive altitude loss, and the other that culminates in a spin—and (3) the neutral-to-unstable longitudinal characteris tics of a fourth airplane at the (approved) aft e.g. position that makes IFR approaches in turbulence extremely difficult. "A review of existing handling qualities criteria indicates that (airframe manufacturers) have not kept pace with aircraft development in the areas otf Dutch roll, adverse yaw, effective dihedral, and allowable trim changes with gear, flap and power variations. It appears that more stringent criteria . . . are needed. . . ." NASA will not identify the problem aircraft because it fears that some marketing departments might take unfair com petitive advantage of the information and this would degrade NASA's position as a research organisation. The specific manufacturers have been notified, however. Further evidence indicating the existence of certain aero dynamic deficiencies of light aircraft (as well as poorly designed aircraft systems) was published independently by the National Transportation Safety Board in July, 1967. In its statistical study, Aircraft Design—Induced Pilot Error (PB No 175-629), the board took a giant step forward when, in effect, it relieved some pilots of accident responsibility by implying strongly that some manufacturers should shoulder the blame because of poor product design. The FAA, which certificates all American aircraft before they are made available to the public, is not mentioned. Soon after the recent public information law was passed, each of the 35 basic models of aircraft discussed in PB No 175-629 was identified. Both NASA's and the board's publications are available from the US Government Clearinghouse in Springfield, Virginia 22151. As ia result of its handling characteristic study, NASA head quarters decided to instigate a research programme with both long- and short-range goals that it felt would be of benefit to general aviation Improvements for current aircraft designs were needed and NASA, with its vast resources, was well equipped to meet the challenge. NASA's short-range programme consists of providing aero dynamic and control system improvements that could be economically feasible either now or in the very near future. The long-range goals involve the evaluation of new and imaginative aerodynamic and control system concepts that could be incorporated into initial aircraft design, possibly within the next five or ten years. Fig I (above) Cockpit layout of NASA 808 showing the angle of attack indicator above the coaming, pitch and roll display at top right of the panel and control column modified to provide stick force measurement and stick-shaker capability Fig 2 (above, left) The second PA-30 Twin Comanche bought by NASA will be used as a ground simulator. The installation will be used to investigate electrical and mechanical means of signalling inputs from the control column to the control surface under "variable stability" conditions Airframe manufacturers will be invited to NASA's Flight Research Centre at Edwards AFB at periodic intervals to be offered any new developments as they occur. Before NASA could begin its research programmes, it had to have a light aircraft of its own. In May 1967 NASA obtained its flying test bed, a new Twin Comanche PA-30B. The N-number was removed and the aircraft became NASA Test Vehicle 808. The selection of the Twin Comanche as the test-bed air craft was based on the fact that it is the lightest aircraft in the twin-engine inventory. NASA wanted a twin so that its programme could include the study of asymmetric power effects. The light weight was desired so that the effects of turbulence would be maximised. The 'aircraft was sent initially to the Langley Research Centre's full-scale wind tunnel in Hampton, Virginia. There, the PA-30 underwent an intensive aerodynamic study. The resulting knowledge was needed as a basis for predicting what effect new modifications would have on the flight characteris tics of the aircraft Russ Barber, NASA project engineer, believes this was the first propeller-driven aircraft to have "flown through" a wind tunnel since World War Two. The Twin Comanche was flown to its present home at NASA's Flight Research Centre at Edwards AFB, California, in December 1967. The aircraft was then equipped with costly and elaborate flight test instrumentation. Protruding from each wing tip is a 4-ft long pitot-static probe equipped with sensitive vanes to record angle-of-attack and sideslip data. Each control surface is rigged with control position transmitters and a small vane on the leading edge of the left wing feeds information to an angle of attack indicator mounted on the instrument panel glare shield. The inside of NASA 808 reveals the completeness of this flying laboratory. Replacing the rear seats is an instrumenta tion rack containing a digital data acquisition system to record in-flight data, the black boxes of a more recently installed yaw damper and an inertial platform. In addition to the ceiling-mounted, 16mm motion picture camera used to film instrument indications, a pitch-and-roll-
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