AN ANALYSIS OF VERTICAL- TAIL LOADS MEASURED IN FLIGHT ON A SWEPI'-WING ID.1BER AIRPLANE

Results are presented of an analysis of vertical-tail shear, bending-moment, and torque loads measured on a swept-wing bomber airplane during rudder-step, rudder-pulse, aileron-roll, and steady-sideslip maneuvers. The flight tests were made at altitudes of 15,000, 25,000, and 35,000 feet and Mach numbers from 0.49 to 0.82. Lift- curve slopes of the vertical tail obtained from the flight data compared favorably with wind-tunnel and theoretically determined values. Tne compressibility effect on the vertical- tail lift-curve slope was counteracted by the fuselage flexibility relieving effect. The center of pressure of the component vertical-tail load due to sideslip was located at approximately 18 percent of the mean aerodynamic chord, and the center of pressure of the rudder- deflection load component was located at approximately 50 percent of the mean aerodynamic chord. The spanwise centers of pressure of both load components were located at about 40 percent of the span. Static directional- stability derivatives of the airplane and con-tributions of the vertical tail and wing- fuselage combination to the directional stabil ity of the airplane obtained from the flight data were in good agreement with wind- tunnel values. The wing- fuselage combina-tion was unstable in yaw and all the determined stability derivatives remained effectively constant over the Mach number and dynamic-pressure ranges