Helicopter flight performance improvement by dynamic blade twist

Dynamic blade twist is investigated as a method for reducing rotor power and improving helicopter performance. An analytical model able to predict helicopter rotor power is first presented, and the flight data of the UH-60A helicopter and the Helicopter Multi-Block Method (HMB2) are used for validation. The predictions of the rotor power are in good agreement with the flight test data and HMB2, which verifies the application of the present method in analyzing helicopter performance. In hover and low speed forward flight, the power reduction by the prescribed dynamic blade twist is substantially small. In high speed forward flight, the effect of dynamic blade twist becomes more pronounced. It is found that lower harmonic blade twist can achieve larger power savings than higher harmonic twist. The zero harmonic twist dominates the power reductions. The helicopter take-off weight was found to have a strong influence on the power reductions achieved by the prescribed dynamic blade twist.