Flight test of a half-scale unmanned air vehicle

A half-scale unmanned air vehicle was flight tested to provide lift and drag data for correlation with the fullscale vehicle. Additional work was carried out to determine if wing drag could be reduced with an improved surface finish and a trailing-edge modification. Ground tests for power and thrust using a torque stand and a lowspeed wind tunnel supported the flight tests for the determination of engine and propeller parameters. A panel method was used to predict the induced drag behavior of the tested air vehicle. Parasite drag was predicted by build-up methods. The predicted parasite drag for the half-scale fell short of flight-tested values by about 25%, but that predicted for the full-scale vehicle correlated well with the flight data. Within the scatter of data, the induced drag correlated satisfactorily. A comparison was made to lift and drag data extracted from full-scale, idlepower glide tests, and correlation was poor. Implications are that residual thrust prevents these glide-test data from accurately representing the full-scale drag polar.