Basic Consideration of the Lifting Capability of Stoppable Rotors

摘要

Stoppable rotor designs involve the operation of the rotor through very high advance ratios and, thus, large regions of reverse flow as the rotor is slowed. Dual-slot, circulation control airfoils, such as those on an X-Wing rotor, produce useable lift in the reverse flow region. A simple method is developed to determine the critical flight condition where the capability of the rotor to produce lift is minimized. Expressions are derived relating the rotor retreating side mean dynamic pressure (indicative of lifting capability) and the lateral offset of the centroid of that dynamic pressure (indicate of roll moment capability) to the rotor geometry and flight conditions. The critical advance ratios predicted by these expressions are compared with the results from a more sophisticated rotor performance analysis.