Re: Aircraft emissions techie question

Date:         17 Dec 99 01:57:46 
From:         Guido Frey <>
Organization: KomTel GmbH
References:   1
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Jack Pease schrieb:
> 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?

Dear Jack,

at Lufthansa German Airlines so called Runway Weight Charts are actually
used.  These Charts show how much takeoff power can be reduced for a
given runway, takeoff mass, outside air temperature, runway condition
and barometric pressure.  By these charts the required thrust setting
will be determined before every takeoff. The procedure is normally used
for every takeoff except under the following conditions: Runway is
covered with snow, slush, ice or standing water; antiskid system is
inoperative; windshear is suspected etc.

The advantage of the procedure is: reduced pollution, longer engine life
and thereby reduced maintenance costs.

The disadvantage is: More noise for the airport sourroundings (lower
climb angle as reduction is limited by 50 feet screen height over the
departure end of the runway, the required minimum climb gradient dual
and single engine for the flown departure route and the accelerate stop
distance for an engine failiure at V1).

I do not know if this a good answers for that part of your question. But
in case you need more details, just drop me an e-mail.

Best regards,