Re: Delta Flt 1288

From:         ehahn@mallard.mitre.org (Ed Hahn)
Organization: The MITRE Corporation, McLean, Va.
Date:         18 Sep 96 13:52:15 
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In article <airliners.1996.1898@ohare.Chicago.COM> "David G. Davidson" <gerhard@onramp.net> writes:

>>> Let me re-state the question: "does the
dgd> engine installed in the #2 position suffer a performance
dgd> degradation due to the presence of the S-duct?"<<

dgd> The only performance corrections that I know of for the center
dgd> engine are if the 6th stage bleed system has been activated. That
dgd> calls for a 0.05 EPR reduction for takeoff and GA power.

dgd> The L-1011 also has no center engine performance correctiosn that
dgd> I'm aware of.

This is all very true.  However, from what I understand, because the
#2 engine in B727 sees "dirty" air from the S-duct, it is more prone
to stall/surge problems than engines #1 and #3.

Therefore, I think that the stall margin performance standard for the
center engine is somewhat higher than those for the pod engines.  Note
that this does NOT mean that the center engine is of a different type,
just that after being tested in the test cell after overhaul, those
engines which have the best demonstrated stall margins are designated
for center engine duty.

This is all hazy recollection from my undergraduate engines course,
however.

ed
--------   Ed Hahn | ehahn@mitre.org | (703) 883-5988   --------
The above comment reflects the opinions of the author, and does not
constitute endorsement or implied warranty by the MITRE Corporation.
Really, I wouldn't kid you about a thing like this.