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![]() Douglas A/B-26 Invader Stability control tests |
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Stability and control characteristics determined from tests
in the Langley 19-foot pressure tunnel of a 0.2375-scale model of the Douglas XA-26 airplane are compared with those measured
in flight tests of a Douglas A-26 airplane. Agreement regarding static longitudinal stability as indicated by the elevator-fixed
neutral points and by the variation of elevator deflection in both straight and turning flight was found to be good except
at speeds approaching the stall. At these low speeds the airplane possessed noticeably improved stability, which was attributed
to pronounced stalling at the root of the production wing. The pronounced root stalling did not occur on the smooth, well-faired
model wing. Elevator tab effectiveness determined from model tests agreed well with flight-test tab effectiveness, but control-force
variations with speed and acceleration were not in good agreement. The use of model hinge-moment data obtained at zero sideslip
appeared to be satisfactory for the determination of aileron forces in sideslip. Fairly good correlation in aileron effectiveness
and control forces was obtained; fabric distortion may have been responsible to some extent for higher flight values of aileron
force at high speeds. Estimation of sideslip developed in an abrupt aileron roll was fair, but determination of the rudder
deflection required to maintain zero sideslip in a rapid aileron roll was not entirely satisfactory.
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