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Helicopter far-field acoustic levels as a function of reduced main-rotor advancing blade-tip Mach numberDuring the design of a helicopter, the weight, engine, rotor speed, and rotor geometry are given significant attention when considering the specific operations for which the helicopter will be used. However, the noise radiated from the helicopter and its relationship to the design variables is currently not well modeled with only a limited set of full-scale field test data to study. In general, limited field data have shown that reduced main-rotor advancing blade-tip Mach numbers result in reduced far-field noise levels. The status of a recent helicopter noise research project is reviewed. It is designed to provide flight experimental data which may be used to further understand helicopter main-rotor advancing blade-tip Mach number effects on far-field acoustic levels. Preliminary results are presented relative to tests conducted with a Sikorsky S-76A helicopter operating with both the rotor speed and the flight speed as the control variable. The rotor speed was operated within the range of 107 to 90 percent NR at nominal forward speeds of 35, 100, and 155 knots.
Document ID
19910001386
Acquisition Source
Legacy CDMS
Document Type
Technical Memorandum (TM)
Authors
Mueller, Arnold W.
(NASA Langley Research Center Hampton, VA, United States)
Smith, Charles D.
(NASA Langley Research Center Hampton, VA, United States)
Lemasurier, Philip
(Sikorsky Aircraft Stratford, CT., United States)
Date Acquired
September 6, 2013
Publication Date
July 1, 1990
Subject Category
Acoustics
Report/Patent Number
NASA-TM-102684
NAS 1.15:102684
Accession Number
91N10699
Funding Number(s)
PROJECT: RTOP 532-06-01-09
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.
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