Rotor wake study near the horizontal tail of a T-tail configuration

Development of advanced rotorcraft configurations has highlighted a need-for high-quality experimental data to support the development of robust and accurate analytical design tools. To provide high-quality experimental data, a test program was conducted in the NASA Langley Research Center 14- by 22-Foot Subsonic Tunnel to measure the flow near the empennage of a 15% scale powered helicopter model with an operating tail fan and a T-tail configuration. Three-component velocity profiles were measured forward of the horizontal tail for four advance ratios using laser velocimetry to evaluate the effect of the rotor wake impingement on the horizontal tail angle of attack. These velocity data indicate the horizontal tail can experience unsteady angle-of-attack variations of over 30 deg due to the rotor wake influence. The horizontal tail is most affected by the rotor wake at and above advance ratios of 0.10.