Why are there no small turboprops?

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.

George Patterson
I childproofed my house, but they *still* get in.

tony wrote:

I'm ignorate of the technology, but seem to remember the airlines went to jets
because fuel costs were lower and they were lest costly to keep running.

Kerosene is much cheaper than 140 octane avgas, and turbines are easier to maintain
than large Pratt & Whitney radials. Neither of these facts is pertinent to light
aircraft.

George Patterson
I childproofed my house, but they *still* get in.

"tony" wrote in message

I'm ignorate of the technology, but seem to remember the airlines went to
jets
because fuel costs were lower and they were lest costly to keep running.


'Tis true that kerosene was substantially cheaper than very high octane
gasoline (typically 140+, iirc) then, but the main reasons were 1) maint
cost -- those high powered turbo-supercharged radials on the Connies and
DC-7s were tweaked to within an inch of their lives, and would fail
regularly. (My brother-in-law's father worked for AA in BOS in that era,
and the standing joke was that they put four engines on those things so they
could arrive with at least two or three); and 2) cruise speed/payload -- the
transition to jet transports allowed schedulers to carry many more
passengers at about 50% more speed. The implications of this change on
system capacity and operation, particularly trans-continental and
trans-oceanic flights, were astounding and very far reaching.

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?
For the majority of GA this has got to be the long-term answer, even in the
US. Europe is leading the way on this topic, oh did I mention gas prices?

- BR
"G.R. Patterson III" wrote in message
...


tony wrote:

I'm ignorate of the technology, but seem to remember the airlines went
to jets
because fuel costs were lower and they were lest costly to keep
running.

Kerosene is much cheaper than 140 octane avgas, and turbines are easier to
maintain
than large Pratt & Whitney radials. Neither of these facts is pertinent to
light
aircraft.

George Patterson
I childproofed my house, but they *still* get in.

Thomas,

There are some smaller turboprops but the economics just aren't there
to put them into mass production. The market is quite small and the
specific fuel consumption of a turbine versus a piston means that if
you put it on your Cessna 210, for example, you can't carry enough
fuel to get anywhere and still put people in the cabin. Plus, the
simple cost of the technology and the metals to handle the heat in a
turbine engine makes it almost impossible to compete with other types
of engines in that horsepower range.

There was an article on the subject of specific fuel consumption and
load carrying ability of turbines in little airplanes in Aviation
Consumer a couple of years back.

For the 100-300 hp range it looks as if going back to diesels, as was
explored in the 1930s, may be appropriate.

All the best,
Rick

"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?

"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?

Cessna 210's and Bonanza's can be found with turbo prop retrofits.
These engines run a long time but when its time for a hot overhaul,
its going to cost you an arm and a leg.

Cost and effficiency. Small turbines are very expensive fuel guzzlers.
Large turbines (airliner size) are efficient but small ones aren't. The
1000hp engines on my MU-2 have a bsfc of .52 and smaller engines would be
even worse. Piston engines are in the .40 area. Diesels are more
promising.

Mike
MU-2


"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?

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?

On Mon, 24 May 2004 at 13:48:53 in message
, G.R. Patterson III
wrote:
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.

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.
--
David CL Francis

On Sun, 23 May 2004 at 23:35:35 in message
, Peter Duniho
wrote:
Some issues however... Turbines operate much more efficiently at altitude,
and planes with less than 300 hp (especially those with significantly less
than 300 hp) just aren't flown that high normally. Also, while they are
more reliable, they are also more complex in certain ways (in spite of the
fundamental concept being simpler), and they are more finicky about proper
operation.

Can you explain why the efficiency of turbines is much higher at
altitude? What sort of efficiency are you talking about?
--
David CL Francis