exhaust flames

Date:         12 Dec 96 04:39:34 
From:         Steve Lacker <slacker@arlut.utexas.edu>
Organization: applied research laboratories
References:   1 2
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On another thread, the following comment appeared:

>John, I recall that PI had Martin 404's for many years, but they had
>two engines.  Quite impressive belching flaming exhaust at night.

Which brings up something I've wondered about on and off. Some 30 years
ago, my family would go and "watch airplanes" at the then-small local
airport for entertainment (my how times change :-) Sitting on the open
observation deck (no security checkpoints back then) about 50 to 100
yards from arriving and departing airliners was rather entertaining in
its own way. I remember that the turboprop airliners that were most
common at that time would occasionally belch a clearly visible fireball
out the pipe when an engine was started. I haven't seen such a
phenomenon in many many years now. What causes it, and why don't I ever
see it anymore? The aircraft were Electras (Allison 501s?) and Convairs
(with either Allison or RR Dart engines, don't remember which). I've
been around C-130s and P3's with similar Allison engines in more recent
times, but I haven't seen a fireball, nor have I ever seen anything
similar with a commuter turboprop. Have the engines been upgraded in
some way over the years? Is it a difference in fuel quality? A
difference in the ignition systems? Am I just never in the right place
now that security is so much stricter?

Stephen Lacker
Applied Research Laboratories, The University of Texas at Austin
PO Box 8029, Austin TX 78713-8029
512-835-3286	slacker@arlut.utexas.edu