Development of a Transonic Free-To-Roll Test Capability

As part of the NASA/Navy Abrupt Wing Stall Program, a relatively low-cost, rapid-access, free-to-roll test rig was developed on which conventional high-strength wind-tunnel models can be used to evaluate both transonic performance and wing-drop/rock behavior in a single tunnel entry. The overall objective was to demonstrate the utility of the free-to-roll test technique as a tool for identifying areas of significant uncommanded lateral activity during ground testing and for gaining insight into the wing-drop/rock behavior of military aircraft at transonic conditions. A description of the test hardware as well as a description of the experimental procedures is given. The free-to-roll test rig has been used successfully to assess the static and dynamic characteristics of four different configurations—two configurations that exhibited uncommanded lateral motions inflight (preproduction F/A-18E and AV-8B) and two that did not (F/A-18C, F-16C). Excellent agreement between free-to-roll results and flight was obtained for those configurations where flight data were available.