Viking Pitch Damping Derivatives as Influenced by Support Interference and Test Techniques

Abstract

Sting support interference effects on the pitch damping derivatives and a comparison of damping characteristics using forced and free oscillation test methods were investigated on 140° spherically blunted cone configurations at M = 1.76-3.0. Sting influences are minimal with sting/model diameter ratios =0.183 and effective sting lengths =3.55 dm. Increasing ds/dm to 0.53 provides a considerable influence to the damping parameter at a = 0°-3° at all Reynolds numbers but shows little or no effect at higher alphas. A good correlation of freeflight and small diameter sting captive model wake geometries (wake neck position and size) was obtained which adds confidence in obtaining damping derivatives through captive model testing. The damping characteristics obtained on 11.23% and 4.35% scale Viking configurations using forced and free oscillation test methods respectively in two different test facilities are compared. The agreement is quite good at almost all test conditions.