wrote in news:e508d435-db20-4b21-9c9b-
:

On Apr 25, 4:37 am, Bertie the Bunyip wrote:
wrote in news:de5298d4-778b-475f-9321-
:





On 25 Apr, 11:53, Frank Olson
wrote:
Bertie the Bunyip wrote:
Chris W wrote in news:74gQj.67968$y05.19485
@newsfe22.lga:

I was channel surfing the other day and caught the tail end of
some
show
about rich people and their planes. Anyway the pilot of this
one
single
engine turbo prop said there was no mechanical connection
between
the
prop and engine. How can that be?

It's a free turbine. Most modern turboprops use that system.
There's a
seperate turbine that runs the prop geabox. He's technically
incorrect
since that turbine is part of the engine...

Bertie

Rich people. More money than brains.- Hide quoted text -

I'm not in disagreement with Bertie, wouldn't dare, but it
"could be" electric drive, hydraulic drive.

Nah, not on a turbine.

These are used in other vehicles. Most cars in the US
use an automatic transmission that includes a
torque convertor for example.

I am sure that it is in this case a free turbine - gas drive -
that connects to a propellor - gas-gas drive.

http://www.gasgas.com/index.shtml

Yeah, almost all modern turboprops use this system. Some of the older
ones, like the RR Dart or the Allisons were gear driven off the main
turbine, but this is all but abandoned these days. In fact, even
"jets"
are really just ducted fan turboprops with the fan driven by a
turbine
in the exhaust.

Bertie

The Garrett TPE 331 is still a fixed turboprop. Lots of those
flying, especially on some upscale kitplanes. Isn't the Swearingen
Merlin powered by those, too?
http://www.aircraftenginedesign.com/pictures/TPE331.gif

Dan


Yeah, Garret are one of the holdouts. They're on alot of airplanes. the
Metro, the turbine commanders. I think there's a Walter that's in th
esame class being used on quite a few airplanes as well. The Pratts are
all free turbines, AFAIK. The older ones are centrifugal engines with a
revese flow, that is, the intake is on the back and they exhaust in
front, which is why the PT6 's have those stovepipes just behind the
prop, and the newer 120 and newers are axial with the air coming in the
front and the fire going out the back. The 120 has a prop brake with
which you can stop the prop while the engine is running ( on the ground)
and use the engine for an APU.


Bertie