Item Details

Results of the Flight Noise Measurement Program Using a Standard and Modified SH-3A Helicopter

by Robert J. Pegg, Herbert R. Henderson, and David A. Hilton
Format
Book; Government Document; Online; EBook
Published
Washington, D.C. : National Aeronautics and Space Administration ; [Springfield, Va. : For sale by the National Technical Information Service], 1973.
Language
English
Series
NASA Technical Note
Summary
A field noise measurement program has been conducted using both a standard SH-3A helicopter and an SH-3A helicopter modified to reduce external noise levels. Modifications included reducing rotor speed, increasing the number of rotor blades, modifying the blade-tip shapes, and acoustically treating the engine air intakes and exhaust. The purpose of this study was to document the noise characteristics recorded on the ground of each helicopter during flyby, hover, landing, and take-off operations. Based on an analysis of the measured results, the average of the overhead, overall, ontrack noise levels was approximately 4 db lower for the modified helicopter than for the standard helicopter. The improved in-flight noise characteristics, and associated small footprint areas and time durations, were judged to be mainly due to tail-rotor noise reductions. The noise reductions were obtained at the expense of required power increases at airspeeds greater than 70 knots for the modified helicopter.
Description
89 p. : ill. ; 27 cm.
Mode of access: Internet.
Notes
  • Prepared at Langley Research Center.
  • Cover title.
  • Bibliography: p. 10.
Series Statement
NASA technical note ; NASA TN D-7330
Logo for No Copyright - United StatesNo Copyright - United States
Technical Details

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    a| Results of the flight noise measurement program using a standard and modified SH-3A helicopter c| by Robert J. Pegg, Herbert R. Henderson, and David A. Hilton.
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    a| Washington, D.C. : b| National Aeronautics and Space Administration ; a| [Springfield, Va. : b| For sale by the National Technical Information Service], c| 1973.
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    a| 89 p. : b| ill. ; c| 27 cm.
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    a| NASA technical note ; v| NASA TN D-7330
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    a| Prepared at Langley Research Center.
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    a| Cover title.
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    a| Bibliography: p. 10.
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    a| A field noise measurement program has been conducted using both a standard SH-3A helicopter and an SH-3A helicopter modified to reduce external noise levels. Modifications included reducing rotor speed, increasing the number of rotor blades, modifying the blade-tip shapes, and acoustically treating the engine air intakes and exhaust. The purpose of this study was to document the noise characteristics recorded on the ground of each helicopter during flyby, hover, landing, and take-off operations. Based on an analysis of the measured results, the average of the overhead, overall, ontrack noise levels was approximately 4 db lower for the modified helicopter than for the standard helicopter. The improved in-flight noise characteristics, and associated small footprint areas and time durations, were judged to be mainly due to tail-rotor noise reductions. The noise reductions were obtained at the expense of required power increases at airspeeds greater than 70 knots for the modified helicopter.
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    a| Hilton, David A.
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    a| Henderson, Herbert R.
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    a| Langley Research Center.
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