Trailing-Edge Flaps for Rotor Performance Enhancement and Vibration Reduction

The comprehensive analysis University of Maryland Advanced Rotor Code (UMARC) was used to quantify the capabilities of trailing-edge flaps (TEFs) for helicopter vibration reduction and performance improvement. The rotor performance in hover was improved with a combination of torsionally softer blades and positive TEF deflections. Suitable combinations of lower harmonic TEF inputs were shown capable of reducing the rotor power requirement by about 4-5% at an advance ratio of mu = 0.4. The TEF was shown to be capable of suppressing vibratory loads at a range of forward speeds, using half peak-to-peak deflections of about 5 degrees-10 degrees. Softening the blades in torsion resulted in larger flap actuation requirements for vibration reduction. A combination of 1, 2, 3, 4, and 5/rev TEF inputs resulted in a power reduction of 1.5%, while also reducing certain vibratory loads by more than 50% in high-speed forward flight.