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Parametric Investigation of the Effect of Hub Pitching Moment on Blade Vortex Interaction (BVI) Noise of an Isolated RotorAt the most fundamental level, main rotor loading noise is caused by the harmonically-varying aerodynamic loads (acoustic pressures) exerted by the rotating blades on the air. Rotorcraft main rotor noise is therefore, in principle, a function of rotor control inputs, and thus the forces and moments required to achieve steady, or "trim", flight equilibrium. In certain flight conditions, the ensuing aerodynamic loading on the rotor(s) can result in highly obtrusive harmonic noise. The effect of the propulsive force, or X-force, on Blade-Vortex Interaction (BVI) noise is well documented. This paper presents an acoustics parametric sensitivity analysis of the effect of varying rotor aerodynamic pitch hub trim moments on BVI noise radiated by an S-70 helicopter main rotor. Results show that changing the hub pitching moment for an isolated rotor, trimmed in nominal 80 knot, 6 and 12 deg descent, flight conditions, alters the miss distance between the blades and the vortex in ways that have varied and noticeable effects on the BVI radiated-noise directionality. Peak BVI noise level is however not significantly altered. The application of hub pitching moment allows the attitude of the fuselage to be controlled; for example, to compensate for the uncomfortable change in fuselage pitch attitude introduced by a fuselage-mounted X-force controller.
Document ID
20160006435
Acquisition Source
Ames Research Center
Document Type
Conference Paper
Authors
Malpica, Carlos
(NASA Ames Research Center Moffett Field, CA United States)
Greenwood, Eric
(NASA Langley Research Center Hampton, VA United States)
Sim, Ben
(Army Aviation Systems Command Moffett Field, CA, United States)
Date Acquired
May 19, 2016
Publication Date
May 17, 2016
Subject Category
Acoustics
Aerodynamics
Report/Patent Number
ARC-E-DAA-TN31321
Meeting Information
Meeting: AHS Annual Forum
Location: West Palm Beach, FL
Country: United States
Start Date: May 17, 2016
End Date: May 19, 2016
Sponsors: American Helicopter Society, Inc.
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.
Keywords
Parametric Investigation
Blade Vortex Interaction
Isolated Rotor
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