Effects of the roll angle on cruciform wing-body configurations at high incidences

Abstract

Three cruciform wings were tested on a body at five roll angles and up to three longitudinal positions in a lowspeed wind tunnel, up to an angle of attack of a = 90 deg. The roll angle affects significantly the fin normal force coefficient. The normal force on the upper fins decreases to zero, at a > 40 deg, possibly because the vortex breakdown on the lower fins induces separated flow over the upper fins. As a consequence, a strong rolling moment is induced at these incidences at asymmetric roll angles. This rolling moment is independent of the wing axial position but proportional to the wing planform area, similarly to the fin normal force coefficient. This rolling moment is much larger than the rolling moment induced on symmetrical configurations by the asymmetric body vortices. The wing contribution to the side force is small compared with the body contribution at asymmetric roll angles. As a result, the maximum side force is not higher than that obtained at symmetric + and X attitudes.