EXPERIMENTAL INVESTIGATION OF MAIN ROTOR WAKE INDUCED EMPENNAGE VIBRATORY AIRLOADS FOR THE RAH-66 COMANCHE HELICOPTER

The Boeing Sikorsky RAH-66 Comanche helicopter for the U. S. Army will have a T tail (horizontal stabilizer mounted at the top of the vertical stabilizer). One of several design concerns is the effect of vibratory airloads resulting from the main rotor wake impinging upon the horizontal stabilizer. Data have been examined from a Comanche wind tunnel model test and an S-76 FANTAIL™ demonstrator full scale flight test to improve understanding of the wake/tail interaction and to develop vibratory airloads to support design of the Comanche empennage. Methods were developed to analyze and generalize the data from both tests. Vibratory airloads from the model test correlate very well with those from the flight test, when appropriate corrections are applied. Results of this work show that the high tail design of the Comanche places the horizontal stabilizer in proximity to the main rotor wake but that the resulting loads and vibrations can be controlled by judicious dynamic tuning of the structure.