Transonic Free-to-Roll Analysis of Abrupt Wing Stall on Military Aircraft

摘要

Transonic free-to-roll and static wind-tunnel tests for four military aircraft―the AV-8B, the F/A-18C, the prepro-duction F/A-18E, and the F-16C―have been analyzed. These tests were conducted in the NASA Langley 16-Foot Transonic Tunnel as a part of the NASA/Navy/Air Force Abrupt Wing Stall Program. The objectives were to evaluate the utility of the free-to-roll test technique as a tool for predicting areas of significant uncommanded lateral motions and for gaining insight into the wing-drop and wing-rock behavior of military aircraft at transonic conditions. The analysis indicated that the free-to-roll results agreed well with flight data on all four models. A wide range of motions―limit-cycle wing rock, occasional and frequent damped wing drop/rock and wing-rock divergence―were observed. The analysis shows the effects that static and dynamic lateral stability can have on the wing-drop/rock behavior. In addition, a free-to-roll figure of merit was developed to assist in the interpretation of results and assessment of the severity of the motions.