140 degrees? Hell, sounds like Uvalde in August. Or Phoenix. I
wouldn't worry too much about it.



Larry




"Bill Daniels" wrote in message
:

"Pete S" wrote in message
...

wrote in message
oups.com...
The August issue of AOPA PILOT reports a "tiny jet engine" is being
developed with 150 lbs of thrust. Its 15" long, 8.6" in diameter and
weighs 19 lbs. I wonder what it costs? This sounds like a great power
to weight ratio.


It is, but what you gain from the engine you loose from the amount of fuel
yoo have to carry. Take a look at www.microjeteng.com for what's available
now. I seem to recollect that a video was published on the internet of a
glass glider with a pop out pod with two jets on it.

Peter



Originally, I thought the horrible specific fuel consumption would make
these 'dog whistles' unsuitable for glider use.

On second thought, the residual weight after all the fuel is burned is much
less than a piston engine and propeller. The extend/stow mechanism is much
simpler as well. If they were used only for self launch and the entire fuel
supply were to be consumed in that launch, the idea has merit.

One worrisome issue is the temperatures of the tail surfaces that are in
contact with the jet exhaust. Bob Carlson told me that the fin on his jet
"Silent" reached 140F during the engine run even with two small turbojets
canted slightly outward to spare the fin. I suppose it's possible to choose
resins and curing processes that would make those fin temperatures
tolerable.

I have to admit that I like Bob Carlson's idea that if the ballast tanks
were to be filled with Jet A instead of water and then when in trouble just
start the jet and fly home instead of dumping ballast. My Nimbus would hold
75 gallons of Jet A which is several hours of engine run.

Bill Daniels