Correlation of F/A-18 buffeting from wind-tunnel and flight tests

Abstract

A method to predict full-scale buffet of the F/A-18 vertical tail using measurements taken on a rigid windtunnel model is presented. Tests were performed on a rigid 6% scale F/A-18 in the 1.5-m trisonic blowdown wind tunnel at the National Research Council in Ottawa, over a range of angle of attack and Mach number. The results from the prediction code were compared to flight test results, which were obtained from flights undertaken at the Aerospace Engineering Test Establishment in Cold Lake, Alberta. In general, comparisons between flight and scaled wind-tunnel data were good, although the initial prediction code invariably underpredicted the full-scale response. Through the use of a variable pressure correlation technique (based on flight conditions) the accuracy of the prediction model was significantly increased. The flight data was also reduced to the nondimensional buffet excitation parameter. It was found that buffeting in the fundamental torsional mode at approximately 45 Hz occurred at a lower angle of attack (with larger overall magnitudes) compared to the fundamental bending mode at 15 Hz.