Dynamic Wind-Tunnel Experiments

Dynamic wind-tunnel (DWT, NAL) experiments on a scaled (-down) model of a delta-wing aircraft were conducted using a single degree of freedom in pitch, yaw, and roll. The DWT facility is a 1.2 m x 1.2 m low-speed (20 to 60 m/s) tunnel of open jet – induced draft type. The FRP aircraft model was supported at the back on a low friction

bearing assembly for the roll motion experiments. DC motors drove the elevons of the aircraft model. In the DWT experiment the aircraft model is free to move about a gimbal with translational and rotary degrees of freedom. The experiments are of semi­free flying type as against the conventional/static wind-tunnel experiments. Miniature (incidence), rate, and acceleration sensors were mounted inside the hollow model of the aircraft to pick up the dynamic responses to the given inputs. Control surface movements were measured using precision potentiometers. Angular accelerations were sensed using a set of strain gauge type accelerometers. The test inputs were applied to servo-controlled (control) surfaces to excite the modes of the aircraft model. Aerodynamic derivatives were estimated from the motion responses of the model by using OEM and the results were compared with other wind-tunnel test methods [24]. The estimated derivatives are given in Table 9.10.