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From: George Braly <gwbraly@gami.com>
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Subject: RE: [LML] Williams EJ22 770 lb thrust
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>>Is the specific fuel consumption of this thing going to be good enough for

what we need in IV's to make them usefull?
 
David Taylor<<

Excellent question, David.

Williams really doesn't release any data, so we don't know.

HOWEVER... What is needed is a "quantum" improvement, not just an
"incremental" improvement.

At this point, the fundamental laws of thermodynamics come into play.  You
may remember something from high school physics or later, about "Carnot"
efficiency.  Basically, this involves the spread in the "high temperature"
and the "low temperature" at which the heat engine operates.  The bigger the
spread, the more efficient the process.

The "high temperature" limitation on a jet engine is the operating
temperature of the high speed (rotational speed) first stage turbine blades.
Until there is a quantum improvement in the materials science that will
permit these blades to operate in a much higher temperature environment,
then I see no way to make an overall quantum improvement in the basic
specific fuel consumption of the pure jet or the prop-jet engines.

The Eclipse Jet is supposed to have 1000+nm range.  That assumes a 2700 lb
empty weight.

All aluminum airframe.  If one, for example, takes a similar sized airframe,
say, a pressurized Aerostar, and removes both engines and both props, and
weighs it, it will weigh more than 2700 lbs.  Thus, I am highly skeptical
that the Eclipse will make its target empty weight, or anything close to it.

If you cut the useful load on the Eclipse by as little as 300 lbs,  the
range drops from 1000+nm down to 600 nm or so.   

Which means, that on a 700 nm trip, I could probably get there in the same
time in my Bonanza.

The laws of physics are everywhere the same, and the numbers never lie...

Regards,  George