Re: Hush Kits

From: (PSBallent)
Organization: America Online, Inc. (1-800-827-6364)
Date:         27 May 96 13:35:40 
References:   1
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The main reason for using hush kits is to meet FAA part III standards for
noise.  Many of the older engines, such as the JT-3D need hush kits to
meet FAA noise standards.   The only other option for meeting noise
standards is to buy new engines.   Hush kits can provide better fuel
consumption, but only by a few percent.  Cost wise, for a 707, hush kits
run 1-2 million an engine.

A hush kit is basically a new cowling that mixes cool bypass air into the
exhaust to reduce thermal shock, which reduces noise.  Some hush kits also
move the Inlet Guide Vain (IGV) forward to reduce noise from the
compressor and fan.

Hope this helps,

Pete Ballentine -