Anhedral tip blades for tiltrotor aircraft

Details Anhedral tip blades for tiltrotor aircraft Anhedral tip blades for tiltrotor aircraft

2010-10-13

2011-11-29

Michener, Joshua (Department: 3644)

Aeronautics and astronautics

Aircraft, heavier-than-air

Airplane and fluid sustained

C244S00700B

Reexamination Certificate

active

08066219

ABSTRACT:
A tiltrotor aircraft having a fixed wing and tilting rotors has a rotor blade with a shaped tip portion that provides improved hover performance. The shaped tip portion preferably has a terminal anhedral of at least 20° with respect to its stacking line, and the blade has an overall twist from root to tip of at least 20°, and a thickness ratio between 19% and 30% at a radial station of 10%. These features advantageously conspire to provide a hover figure of merit of at least 0.84 and a cruise propulsive efficiency of at least 0.85. A controller preferably limits the rotor speed in sustained airplane-mode forward flight cruise of at most 40% of a hover maximum rotor speed, and alternatively or additionally limits a rotor edgewise advance ratio to at most 0.20.

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