Wind Tunnel Test of a Very Flexible Aircraft Wing

Abstract

A wind tunnel test of a very flexible wing model has been conducted to collect data suitable for correlating with and validating nonlinear aeroelastic analysis methods. Nonlinear methods are necessary to accurately predict the response of high altitude long endurance vehicles such as the NASA Helios or the DARPA Vulture class of vehicles and very little test data is available for validating such methods. A 9 foot semi-span cantilever mounted flexible model was designed and built to withstand a wing tip deflection of 5 feet. The model included actuated control surfaces and a side wall turntable mount for adjusting angle of attack. The model was fully instrumented to collect structural response data and an optical deflection measurement system was utilized to collect deflection data. During seven days of testing and 132 runs, data was collected from over 700 hundred static test conditions and 200 dynamic conditions. During the testing, a low speed instability region was discovered and limit cycle oscillation behavior observed. A maximum wing tip deflection of 45 inches was achieved during the higher speed test conditions.