Mechanisms of Noise Transmission through Helicopter Gearbox Support Struts

[+] Author and Article Information
M. J. Brennan

Royal Naval Engineering College, Manadon, Plymouth, Devon, PL5 3AQ United Kingdom

R. J. Pinnington, S. J. Elliott

Institute of Sound and Vibration Research, University of Southampton, Southampton, Hampshire, SO9 5NH United Kingdom

J. Vib. Acoust 116(4), 548-554 (Oct 01, 1994) (7 pages) doi:10.1115/1.2930462 History: Received March 01, 1993; Revised July 01, 1993; Online June 17, 2008


Helicopter gearbox support struts are structural members designed to take large compressive and tensile mechanical loads. They also act as vibration transmission paths connecting the major noise and vibration generators of the main rotor and gearbox to the fuselage and cabin. In this paper the mechanisms of vibration transmission through these struts are examined. The differences between the low frequency behavior that is important in the transmission of the rotor vibrations, and the high frequency behavior that is important in the transmission of gear noise are discussed. A flexible element is introduced in series with the strut, and the limitations of this simple passive measure in attenuating longitudinal and flexural vibrations are highlighted. The analysis shows that there is a difference in the mechanisms of vibration transmission between low and high frequencies, and that there are difficulties in applying effective passive vibration isolation measures to this system.

Copyright © 1994 by The American Society of Mechanical Engineers
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