Engine hush kits

From:         rwi@whidbey.whidbey.com (Richard Isakson)
Organization: The Whidbey
Date:         28 Mar 95 07:49:44 
References:   1
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In sci.aeronautics.airliners Steve Howie <showie@uoguelph.ca> said: 
>I've asked unsuccessfully on rec.travel.air about what is involved in  
>installing the so-called "hush kits" on jet engines. Could someone (Andrew?)  
>enlighten me as to what makes up one of these kits, and how they actually 
>reduce engine noise. 
While all hush kits have hardware fixes in them, one of the big factors in
reducing the noise is a reduction in the performace of the airplane.  You
can either derate the engines which gives less thrust over the noise
station. Or you can reduce the maximum takeoff weight of the airplane which
puts the airplane higher over the noise station. Or you can do both. 
Either way you have to recertify parts of the flight manual. 
Rich Isakson (rwi@whidbey.com)