Wind tunnel test of single-rotor lift-offset due to differential flaps

Abstract

A single-rotor lift-offset system for a winged compound helicopter is evaluated at JAXA 2m x 2m low-speed wind tunnel in the closed test section using a flyable radio-controlled model rotorcraft. The single-rotor lift-offset is achieved utilizing flaps originally designed for download reduction during hovering flight on a winged compound helicopter. Differential flaps on the left and right wings create a rolling moment on the wing-body to produce a lift-offset state of the rotor while the overall rotorcraft rolling moment is balanced. Two types of rotor blades, which are the optimized rotor blade for high advance-ratio flight and the reference UH-60A rotor blade, were tested to compare the effect of lift-offset on the overall aerodynamic performance. The tests were conducted at advance ratios of 0.3, 0.5, and 0.7. The test results show that the single-rotor lift-offset improves the overall effective lift-to-drag ratio as expected. Furthermore, the adverse yaw effect due to the differential flaps is observed from the test results of isolated wing-body.