Newsgroups: sci.aeronautics.airliners
From: David Lednicer <dave@amiwest.com>
Subject: Smoking on airliners (also jet fuel followup)
Date: 22 Jun 94 16:57:48

	Yes, it is nice that we don't need to breath in that stuff, but
the yellow stain that cigarette smoke leaves was great for finding leaks
in the pressure vessel of the aircraft (another words - cracks).  I have
also heard that the goo helped seal the pressure relief valve when it was
closed.

	Somehow a post about Jet fuel ended up in this thread.  I'm not
an expert, but I know Jet A (JP-1) used in commercial airliners is
essentially Kerosene, which must have an awfully low Octane rating.
Every time someone gets a tank full of it on a piston engined aircraft,
by accident, they end up crash landing shortly after take-off from the
poor engine performance.  Lead is added to Gasoline to raise its Octane
rating, usually from the low 80s to 100 or more (to delay the onset of
detonation and increase the available power).  As jet engines have continous
combustion, instead of intermittent, high Octane ratings are not necessary
for jet fuel.  However, the old JP-4 fuel that has largely been phased out
was a 50-50 cut of Gasoline and Kerosene.  I remember a B737-300 getting a
load of JP-4 and having problems with the CFM-56s.  Last I knew, the military
mostly used JP-5, which I don't think is much different from JP-1.  The
SR-71 was an exception, using an exotic fuel that was called JP-7.


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David Lednicer             | "Applied Computational Fluid Dynamics"
Analytical Methods, Inc.   |   email:   dave@amiwest.com
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