BODY-AXIS ROLLING MOTION CRITICAL STATES OF A 65-DEGREE DELTA-WING

Dynamic wind tunnel test results of a 65-deg swept delta wing are revi ewed. These tests involved body-axis rolling motions at moderate (15- to 35-deg) angles of attack in both the Institute for Aerospace Resear ch 2 X 3 m low-speed wind tunnel and the 7 x 10 ft Subsonic Aerodynami c Research Laboratory facility at Wright-Patterson Air Force Base. The y included static, forced oscillation, and free-to-roll experiments wi th flow visualization, Multiple trim points (attractors) for body-axis rolling motions and other unusual dynamic behavior were observed. The se data are examined in light of the nonlinear indicial response theor y. The analysis confirms the existence of critical states with respect to roll angle. When these singularities are encountered in a dynamic situation, large and persistent transients are induced. Conventional m eans of representing the nonlinear forces and moments in the aircraft equations of motion, notably the locally linear model, are shown to be inadequate for these cases. Finally, the impact of these findings on dynamic testing techniques is discussed.