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Helicopter Rotor-Blade Chord Extension Morphing Using a Centrifugally Actuated Von Mises Truss

2014; American Institute of Aeronautics and Astronautics; Volume: 51; Issue: 5 Linguagem: Inglês

10.2514/1.c032299

1533-3868

Patrick Moser, G. C. Barbarino, Farhan Gandhi,

Structural Analysis and Optimization

Previous studies have shown that chord extension morphing over a spanwise section of helicopter rotor blades can reduce main rotor power requirements in stall-dominant flight conditions while being able to increase the maximum gross weight, altitude, and flight speed capability of the aircraft. This study examines a centrifugally driven, fully passive chord morphing mechanism for helicopter rotor blades. It is based on a von Mises truss connected to a rigid extension plate that deploys through a slit in the trailing edge. When the rotor revolutions per minute increases beyond a critical value, the chordwise component of centrifugal force on the assembly results in the deployment of the plate beyond the slit in the trailing edge, effectively increasing chord length. On reducing the revolutions per minute, a retraction spring pulls the plate back within the confines of the blade. This study presents the design process, iterations, and final design solution for a configuration that undergoes 20% chord extension. A prototype was fabricated and tested on the bench top as well as on a rotor test stand at rotational speeds simulating more than 60% full-scale centrifugal loads. The test results demonstrate that the concept works. However, effects such as friction lead to revolutions-per-minute requirements different from those predicted by simulation.