Re: Aircraft emissions techie question

Date:         17 Dec 99 01:57:48 
From:         Erik Verheijden <erikv@home.nl>
Organization: @Home Network
References:   1
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Jack Pease schreef:
>
> Don't suppose anyone can help me with a technie question.
>
> NOx emissions rise with engine power. NOx is saved if a pilot selects 85%
> thrust on take off rather than 100% thrust, and presumably save fuel, so why
> isn't this done all the time if the engines have enough in reserve??? Does
> it reduce ambient noise if a plane shoots down the runway on 100% power then
> thrusts down once over the airport boundary, or is it better to be 85%
> thurst all the way but lower on the airport boundary?

To answer part of your question, many take-offs are made at less than
100% (derating). The main reason for this is engine wear.
A jet engine consumes much more fuel at lower altitudes. A take-off and
climb with lower thrust settings may not save fuel at all: the airplane
spends more time at low altitudes with a high fuel flow.

Erik.