Re: Engine noise

Date:         07 Jan 97 07:20:21 
Organization: Earthlink Network, Inc.
References:   1 2 3
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On 06 Jan 97 01:41:44 , (Larry Stone) wrote:

>In article <airliners.1997.110@ohare.Chicago.COM>, "Dave & RuthAnne
>Clickner" <> wrote:
>>Stage 2 or 3 is based on the weight of the aircraft and the noise level.  A
>>767 can make a lot of noise and be stage 3 while a 727 can make less and be
>>stage 2.  And yes there is a very large difference in the noise levels of
>>stage 2 and stage 3 for a single aircraft type.
>I was quite surprised recently to discover that our (United's) older
>747-100's and 200's, which are Stage 2, get classified Stage 3 when flying
>red-eye from HNL to SFO, apparently due to a pre-dawn noise requirement at
>SFO. I've been unable to determine if the "modification" is anything more
>than placing a placard in the flight deck that in essence says "this is a
>Stage 3 airplane". Perhaps there's also a largely irrelevant maximum
>take-off weight reduction - irrelevant due to the relatively short flight
>and resulting fuel on board as I've never been aware of a 747 off HNL to
>the West Coast being wwight restricted (unlike the DC-10-10's).

I do not know who "classifies" them as this but it is in violation of
FAR 36 in several ways.

1. Once an aircraft is Stage 3 it is not permissable for it to ever go
backward and be a Stage 2 aircraft again.

2.  The aircraft's "Stage" is that defined in the FAA Approved Flight
Manual.  The only way for it to change is to get a FAA Approved
revision to the AFM.  If the AFM says nothing it is a Stage 1

3. As for the gross weight,  this is the maximum allowable takeoff
weight as defined in the limitations section of the AFM.  This weight
may be lower than the Structure of the aircraft is capable of, simply
due to noise (FAR 25).

Simply put, an airline, operator, etc., cannot change the "Stage" or
the certificated noise levels of an aircraft at will.  Current FAA
requirements state that only the Aircraft Certification Offices can
due approvals where noise (FAR 36) is involved.  It cannot be done by
a POI, as a Field Approval, by (I think) any DAS, etc.

There can only be one set of Certifcated (approved) noise numbers for
a given aircaft model and gross weight.  Although, there are some
aircraft that can be either Stage 2 or Stage 3.  This is ussually
based on how much the operator paid the manufacturer for the aircraft
and it is controlled by serial number in the AFM, and only the Type
Certificate holder (manufacturer usually) can revise the AFM.