Wind Tunnel Testing a Small Isolated Folding Propeller

Aircraft with small speed-controlled propellers are becoming increasingly popular. This is conspicuous in the commercial sector, but also evident in the defense sector. Proof of the latter is the Army's Air Launched Effects (ALE) program, which aims to develop foldable, tube-launched Unmanned Aerial Systems (UAS). Such aircraft will likely use small speed-controlled folding propellers, which have unique geometry and limited publicly available data making it difficult to characterize their performance. This paper concerns performance testing of a small speed-controlled folding propeller in the U.S Army's 7- by 10-foot Wind Tunnel at NASA Ames Research Center, utilizing a new test rig that aerodynamically isolates a propeller's blades. The results of the test are presented, which include thrust and efficiency measured at various pitch angles, rotational speeds and wind speeds. Useful and expected trends are identified in the data, such as the peak efficiencies increasing with increased RPM, wind speed and blade pitch.