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Blade-Mounted Flap Control for BVI Noise Reduction Proof-of-Concept TestThis report describes a wind tunnel test of the McDonnell Douglas Helicopter Systems (MDHS) Active Flap Model Rotor at the NASA Langley 14- by 22-Foot Subsonic Tunnel. The test demonstrated that BVI noise reductions and vibration reductions were possible with the use of an active flap. Aerodynamic results supported the acoustic data trends, showing a reduction in the strength of the tip vortex with the deflection of the flap. Acoustic results showed that the flap deployment, depending on the peak deflection angle and azimuthal shift in its deployment schedule, can produce BVI noise reductions as much as 6 dB on the advancing and retreating sides. The noise reduction was accompanied by an increase in low frequency harmonic noise and high frequency broadband noise. A brief assessment of the effect of the flap on vibration showed that significant reductions were possible. The greatest vibration reductions (as much as 76%) were found in the four per rev pitching moment at the hub. Performance improvement cam results were inconclusive, as the improvements were predicted to be smaller than the resolution of the rotor balance.
Document ID
19960055175
Acquisition Source
Langley Research Center
Document Type
Contractor Report (CR)
Authors
Dawson, Seth
(McDonnell-Douglas Helicopter Co. Mesa, AZ United States)
Hassan, Ahmed
(McDonnell-Douglas Helicopter Co. Mesa, AZ United States)
Straub, Friedrich
(McDonnell-Douglas Helicopter Co. Mesa, AZ United States)
Tadghighi, Hormoz
(McDonnell-Douglas Helicopter Co. Mesa, AZ United States)
Date Acquired
September 6, 2013
Publication Date
July 1, 1995
Subject Category
Acoustics
Report/Patent Number
NAS 1.26:195078
NASA-CR-195078
L6BCK-FR-94001
Accession Number
96N36945
Funding Number(s)
PROJECT: RTOP 505-63-36-03
CONTRACT_GRANT: NAS1-19060
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.
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