FLIGHT INVESTIGATION OF THE LONGITUDINAL STABILITY AND CONTROL CHARACTERISTICS OF A FOUR-PROPELLER TILT-WINGnVTOL MODEL WITH A PROGRAMED FLAP

摘要

An investigation of the longitudinal stability and control charac¬teristics, during slow constant-altitude transitions from hovering to forward flight, of a high-wing VTOL (vertical-take-off-and-landing) airplane model with a tilting wing and flap was conducted by a remote-control free-flight model technique. The model was a four-propeller configuration with a 35-percent-chord slotted flap that was programed to deflect as the wing rotated from 90° to 0° for transition from hovering to forward flight. The flap programing was arranged so that the flap was retracted for the 90° and 0° wing-incidence conditions to give a clean configuration for hovering and for normal forward flight. The flap was deflected for intermediate angles of incidence to obtain favorable performance and longitudinal trim characteristics for the transition flight conditions.nThe flight tests showed that the transition could be performed and that by proper programing of the deflection of a full-span flap and the incidence of the horizontal tail, the variation of longitudinal trim throughout the transition range could be practically eliminated so that the control power remaining for maneuvering would not be reduced at any point in the transition. The model had an unstable pitching oscillation in hovering flight, but this dynamic instability decreased rapidly as the forward speed increased.