Re: Phase III Engine

Date:         06 Oct 97 02:14:23 
From: (Brian Clouse)
Organization: Prodigy Services Company  1-800-PRODIGY
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  or MIME structure

Do you mean Stage 2 vs. Stage 3 aircraft?  Those refer to noise levels
produced during takeoffs and landings, with Stage 3 limits being stricter.
  Stage 1 means no limits, Stage 2 is basically 1960's-era jets, and
Stage 3 covers pretty much anything made since the 1970's.

The difference matters because many airports located near populated areas
limit, or even ban, Stage 1 or 2 operations at night or even entirely.
For flexibility, and good neighborliness, as well as economics (the older
planes are less efficient), the airlines are retiring non-Stage 3
aircraft as soon as they can.

Noise levels are a result of a lot of things besides the engines, like
the weight and overall dragginess of the aircraft, especially during
approach.  For regulatory purposes, the FAA has a complex formula based
on measured decibel levels at prescribed locations on an aircraft
submitted for certification.

Brian Clouse