Design Investigation and Hover Testing of an On-blade Active Trailing-edge Flap for Higher Harmonic Control

This paper presents an open-loop hover experiment and analysis for a 4-blade Mach-scaled Seoul National University Flap (SNUF) rotor. A detailed finite element analysis is attempted to predict allowable experiment range that provides sufficient structural integrity. Multi-body dynamic analysis DYMORE and cross-sectional design program VABS are used to analyze the present trailing-edge flap rotor blade, and the flap hinge stiffness is calibrated on the static bench test. Ground testing on the present rotor shows a linear strain-displacement response, and the relevant result shows better than 80% correlation against DYMORE prediction. Appropriate test matrices are constructed and two of those are attempted herein. The first one is the baseline no-actuation collective sweep test at two different rotating speeds at tip Mach of 0.22 and 0.3, respectively. The results are utilized to correlate between the momentum theory and free wake empirical parameters. Next, a single active flap blade test is attempted to assess the trailing-edge flap driving component. It is found that the dynamic trailing-edge flap deflection result needs to be both electrically and mechanically isolated from the test stand. In the future, trailing-edge flap deflection will be recorded for 1 - 5/rev activation at tip Mach 0.5, while four-blade actuation engaged. The frequency response of the trailing-edge flap mechanism will be identified, and 1/rev tracking control will be attempted.