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Acoustic Characteristics of a Model Isolated Tiltrotor in DNWAn aeroacoustic wind tunnel test was conducted using a scaled isolated tiltrotor model. Acoustic data were acquired using an in-flow microphone wing traversed beneath the model to map the directivity of the near-field acoustic radiation of the rotor for a parametric variation of rotor angle-of-attack, tunnel speed, and rotor thrust. Acoustic metric data were examined to show trends of impulsive noise for the parametric variations. BVISPL maximum noise levels were found to increase with mu for constant alpha and C(sub T), although the maximum BVI levels were found at much higher cc than for a typical helicopter. BVISPL levels were found to increase with mu for constant alpha and C(sub T). BVISPL was found to decrease with increasing C(sub T) for constant alpha and mu, although BVISPL increased with thrust for a constant wake geometry. Metric data were also scaled for M,i, to evaluate how well simple power law scaling could be used to correct metric data for M(sub tip) effects.
Document ID
19990053133
Acquisition Source
Langley Research Center
Document Type
Reprint (Version printed in journal)
Authors
Booth, Earl R., Jr.
(NASA Langley Research Center Hampton, VA United States)
McCluer, Megan
(NASA Ames Research Center Moffett Field, CA United States)
Tadghighi, Hormoz
(Boeing Co. Mesa, AZ United States)
Date Acquired
August 19, 2013
Publication Date
January 1, 1999
Subject Category
Acoustics
Meeting Information
Meeting: 55th
Location: Montreal, Quebec
Country: Canada
Start Date: May 25, 1999
End Date: May 27, 1999
Sponsors: American Helicopter Society, Inc.
Distribution Limits
Public
Copyright
Other

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