Re: EPR v. N1 for turbofan power setting

From:         ejw111@psu.edu (Eric J. Whitney)
Organization: Applied Research Laboratory, Penn State
Date:         28 Feb 95 22:57:35 
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In article <airliners.1995.194@ohare.Chicago.COM> rdd@netcom.com (Robert Dorsett) writes:

I do not have a lot of experience in this area, but I do remember being in a 
meeting a long time ago (about 8-10 years) in which there was some 
discussion about the parameters used to determine power setting.

I remember that a design engineer on a military engine project said that 
F/A-18 pilots used Exhaust Gas Temperature (EGT) to determine take-off power 
setting. The pilot would throttle the engine to reach a specific EGT, once 
reached the plane would then be catapulted off the deck.  It's easy to see 
that you can get the same EGT with different EPR and N1's depending on the 
condition of the engine.  So, when the engineer said this other designers (I 
assume on other engine programs) went nuts.  They said in a severly degraded 
engine N1 could be so low that the plane could be catapulted into the sea! I 
cannot comment on any of this because I'm just not knowledgeable in this area; 
but using EGT would seem to be very iffy proposition.

I know of no commercial engines that use EGT as a measure of thrust. Perhaps 
somebody with more experience in this area could shed some light on this topic.

For example, in the commercial airliner what is the relationship between EPR 
or N1 and EGT?


Eric