Abstract
A quasi-static acoustic mapping method has been developed to predict rotorcraft ex ernal noise This takes advantage of an expansion, to first order, about a solution to the helicopter no dimensional-state trim equations to include the effects of acceleration parallel to the flight path and X-fo c anges on e radiated noise. Application of the new method to predict helicopter blade-vortex interaction (BVI) noise has shown that choice of flight-path angle, X-force, and vehicle acceleration all have an important influence on ground noise exposure during approach and landing. The effect of constant flight-path-angle approaches on BVI ground noise, with and without X-force control, is compared with decelerating approaches at the same flight-path angle. Two different quiet flight trajectories are suggested that use a combination of these controls to minimize BVI noise exposure on the ground during a helicopter approach to a landing.
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