Why are there no small turboprops?

here you go, they do exist
http://www.atpcoinc.com/Pages/Products.html



"Thomas J. Paladino Jr." wrote:

I have always wondered why there are no small GA turboprops. It seems like
most of the major problems & maintenance issues associated with GA aircraft
are related to the piston motor, and as far as I can tell, turboprops are
much more reliable, fuel efficient, smoother running and easier to maintain.

So it begs the question, why are there no small turboprops in the 100-300hp
range for use on GA aircraft? I would think that turbine engines of this
size would be relatively easy to produce, and would be ideal for GA
applications. The smoother operation and lower vibration levels would also
ease wear and tear on the entire airframe and avionics components. So what's
the deal? Does turbine technology not translate downwards very well? Would
it be cost prohibitive? Am I entirely missing something?

the lanceair has a turbo prop version, I saw one take off few months back, fast
little airplane

Bob Gardner wrote:

Author Stuart Woods has a Malibu with a turbo engine, and I have seen a
turbo-powered 206.

Bob Gardner

"Thomas J. Paladino Jr." wrote in message
...
I have always wondered why there are no small GA turboprops. It seems like
most of the major problems & maintenance issues associated with GA
aircraft
are related to the piston motor, and as far as I can tell, turboprops are
much more reliable, fuel efficient, smoother running and easier to
maintain.

So it begs the question, why are there no small turboprops in the
100-300hp
range for use on GA aircraft? I would think that turbine engines of this
size would be relatively easy to produce, and would be ideal for GA
applications. The smoother operation and lower vibration levels would also
ease wear and tear on the entire airframe and avionics components. So
what's
the deal? Does turbine technology not translate downwards very well? Would
it be cost prohibitive? Am I entirely missing something?

"Robert M. Gary" wrote in message
om...
"Mike Rapoport" wrote in message
link.net...

Diesels are more
promising.

And can run on the same gas.

And there's other sources for diesel...and maybe you can smoke it, too.

http://www.artistictreasure.com/learnmorecleanair.html

"Peter Duniho" wrote in message ...

For experimentals, it sounds like (from one of George's earlier posts) that
people ARE looking to incorporate small turbines into light airplanes, but I
doubt it's cost effective. As near as I can tell, for a given horsepower,
turbines are simply more expensive and for sure it's harder to find someone
qualified to work on them.

Maybe one day they'll be ubiquitous in a wide variety of applications, and
they'll start showing up in light airplanes too. But it seems to me that
until there's a huge market for certificated low-horsepower turbine engines,
no one's going to bother working on them.

Pete

I know there's been an RV-4T - they grafted a turboprop onto the front
of an RV-4. I think the biggest problem they had (besides fuel
consumption) was that they didn't mount the exhaust stacks right, and
it "backed up" a bit in the engine.

On Tue, 25 May 2004 00:40:15 GMT, "G.R. Patterson III"
wrote:

Barney Rubble wrote:

Slightly off-topic, why has no-on mentioned diesel engines (that run on
Jet-A1)? This has got to be the way to go, better economy, better operation
at altitude, simpler mechanicals (less to break) and FADEC/ECU controlled?

Actually, because of the higher compression ratios, the mechanicals are not simpler.

I know that the forces generated during compression are higher at a
higher compresion ratio, but I cannot imagine that they are higher
than the power forces. Now whether the power forces (peak) are higher
in a compression ignition engine ... maybe (and probably), but I've
never seen data from conn rod strain gages.

G.R. Patterson III opined

Greg Copeland wrote:

Is simple economics the answer? $30k piston versus something like $80k
turbine, or something like that?

It's certainly one answer. The price on that Maule is $450,000. With an
IO-540, it's
$173,420.

I've read that there are technical problems building small turbines; ie. the
smaller the diameter of the turbine, the faster the blades must spin to
produce power.

The biggie is edge effects. There is a minimum clearance between the turbine
and the case, and that clearance is independent of the diameter of the
turbine. So small turbines have much higher tip losses.


-ash
Cthulhu for President!
Why vote for a lesser evil?

On Tue, 25 May 2004 00:40:15 GMT, "G.R. Patterson III"
wrote:

Actually, because of the higher compression ratios, the mechanicals are not simpler.

Well sort of. Some two stroke cycle diesels don't have overhead
valves. No diesel has a spark ignition system. This type of engine
could be considered mechanically more simple than a four stroke cycle
engine.

But the fuel pump is a lot more complex and higher pressure, and most
diesels have either a turbo supercharger or a mechanically driven
supercharger, or both.

See http://www.deltahawkengines.com/index.htm for an example of a
very cool V four two stroke diesel engine intended for the homebuilt
market initially, and perhaps eventual certification.

Corky Scott

"Gerald Sylvester" wrote in message
nk.net...
Did you know you can buy true turbo jets for model aircraft? They cost
about $3000 and give about 20 lb thrust, They are around 4" in diameter.

I then said to
a guy, "Man that sounds like a turbine." He told me it was.

This is what we were talking about earlier with the jet
engines on the Cri-cri.

http://www.amtjets.com/gallery_real_plain.html

Some more "normal" and some unusual applications:
http://www.amtjets.com/gallery.html

Paul

Hi George,

Slightly off-topic, why has no-on mentioned diesel engines (that
run on Jet-A1)? This has got to be the way to go, better economy,
better operation at altitude, simpler mechanicals (less to break)
and FADEC/ECU controlled?

Actually, because of the higher compression ratios, the mechanicals
are not simpler.

I know that the forces generated during compression are higher at a
higher compresion ratio, but I cannot imagine that they are higher
than the power forces.
Now whether the power forces (peak) are higher
in a compression ignition engine ... maybe (and probably), but I've
never seen data from conn rod strain gages.

Peak pressure during combustion is about twice as high on a diesel
engine compared to a spark ignition engine (about 160 bar / 2400 psi
vs. 80 bar / 1200 psi). Hence the heavier build of diesels. On the plus
side, diesels run about 200 degC cooler than SI-engines even though
most diesels are turbocharged vs. naturally aspirated gasolines.

However diesels are MUCH more simple in mixture control - there is
none. You just inject the amount of fuel you need to burn to achieve
the desired torque. On gasoline (spark ignition) engines you control
the engine torque by restricting the air flow with a throttle. You then
have to match the fuel flow to the varying air flow pretty precisely.

Also, the entire ignition system, spark plugs, magnets, is omitted on a
diesel. 50% of engine problems on aviation piston engines is related to
ignition problems.

regards,
Friedrich

--
for personal email please remove "entfernen" from my adress

On Mon, 24 May 2004 at 17:31:12 in message
, Peter Duniho
wrote:
"David CL Francis" wrote in message
...
[...]
Can you explain why the efficiency of turbines is much higher at
altitude? What sort of efficiency are you talking about?

Mainly the same reason turbocharged reciprocating engines operate more
efficiently at altitude. You're carrying around a compressor that just
isn't all that useful down low. Once you get higher, where there's less
drag, you get more "bang for the buck" out of the engine. Of course, as
Mike Rapaport pointed out, there's also the issue of efficiency with respect
to the size of the engine (independent of operating altitude).

But is that efficiency? I would have thought that efficiency was
measurement by a parameter like pounds of fuel used per effective shaft
horsepower per hour. That certainly changes with altitude but not so
much.

--
David CL Francis