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Old March 8th 05, 05:18 PM
Peter Stickney
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In article ,
"Mike Kanze" writes:
Peter's calculations are a reminder that it is the weight that counts, not
the gallonage. And more specifically, how many BTUs/pound you can get from
your fuel choice (more = better, usually). This is why the world has never
seen a commercially-viable coal-fueled aircraft, old Aeroflot jokes
notwithstanding.


Just so. All hydrocarbon fuels have about the same energy content -
something around 18,000 BTU/lb. Since the jet's fuel controller is
figuring stuff out by the amount of heat produced, it just stuffs the
fuel in until it's hot enough.
Early on, the Navy ran their jets on AVGAS. The carriers already had
bunkerage for that, and they didn't need to add a new supply chain -
that meant modifying not only the carrier's internals, but also the
tankers and replenishment ships that fed them. There were a few
problems though. AVGAS has a desity of 'bout 6.0 lbs/U.S. Gallon.
JP-4 (Jet-B) is about 6.5 lbs/gal, and JP-5 (JET-A) is about 6.7 -
that means that an AVGAS powered jet is going to have 90% of the range
of the same airplane burning Kerosine. Casoline's a much more serious
fire/explosion hazard. The high lead content of 115/145 AVGAS also
played hell with the burners and turbine section.
Biting the bullet, and switching to JP-5 was a big win. Especially
since you could run the ship's boilers on JP-5 as well, giving you a
lot more bunkerage, and a single supply line.

There were a number of tricks played in the early days of jets to
increase the density of fuel - a favorite, used in the jet
cross-country attempts in the early 1950s (Bendix races, * such) was
to put cans of Dry Ice into the fuel tankers used to refuel the jets
at their intermeddiate stops. The chilled fuel was more dense, and
you'd squeeze just enough extra Cubic BTUs into the tanks that it
would essentially make up for the fuel used for takeoff.


--
Pete Stickney

Without data, all you have are opinions