Diesel aircraft engines and are the light jets pushing out the twins?

"Peter Duniho" wrote in message
...
"Mike Rapoport" wrote in message
nk.net...
I don's see that I've overlooked something relative to the Caravan. The
Caravan has a 940hp engine. There is currently no suitable piston engine
to
power such a large, single engine airplane. It couldn't be anything
other
than a turbine.

As you yourself pointed out, that 940hp engine is derated to 675hp. You
don't need a 940hp piston engine to provide the equivalent power, and a
675hp piston engine is not out of the question (for example, the Orenda V8
turbine replacement engines are in that ballpark, if I recall correctly).

Large snip.

I agree that it is difficult to compare different types of engines apples to
apples since the power and specific fuel consumption curves are so
different.. I have two airplanes, one turbine and one piston. Both engines
are well suited for their applications. In the Helio, power is often set to
15"MP to keep the speed down in turbulent, low altitude mountain flying. A
turbine would be horribly inefficient operated like this. In the MU-2,
power is set close to the torque or temp limits from takeoff until reaching
about 16,000' on the descent. A piston engine operated flat out like this
wouldn't last long, particularly at high altitude. Both powerplanes have
their place although I think that diesels will eventually replace gasoline
piston engines because of their efficiency, long life and simplicity.

Mike
MU-2

"C Kingsbury" wrote in message
om...
wrote in message
...
In rec.aviation.owning Mike Rapoport
wrote:

wrote in message
...

A lot of them are used to power natural gas compressors way out in the
middle of nowhere and reliability is much more important than fuel
efficiency and you have a large suitable fuel supply availible.

Large mobile electric generators are another common ground-based
application. Don't forget that weight and size are also relatively
unimportant in these applications, which makes a lot of engineering
problems much easier.

Given the high initial cost of turbines and the hgiher fuel
comsumption, I
doubt that turbines would be competitive with gasoline engines given
current
price differentials between the two fuels. The beauty of a diesel
aircraft
engine is that it should cost the same as a gas engine, has fewer
parts,
uses less fuel and lasts longer. The turbine engine is more reliable
but
costs more and uses more fuel. The lower the hp the less competitive
the
turbine gets against the diesel.

Your first sentence overlooks the fact that turbines are currently
competitive at the Caravan level, but I pretty much agree with the
rest.

Airplanes are designed around engines. Want to know what a
piston-powered Caravan looks like? It's called a Cessna 402.

The 'van is a pretty idiosyncratic plane- basically a flying box
truck. Great for hauling a heavy load a short distance into a small
strip. Sure, there's a bunch of rich boys out there flying them
around, too, but I suspect economics do not factor into their decision
in any way. The guys putting these things on amphibious floats with
executive interiors could probably afford to operate them even if they
only ran on vintage Champagne. A mainstream pilot can get a hell of a
lot more utility out of a SR-22 or 206 for probably 1/3rd or less of
the costs.

OK, let's say I buy into about 400hp as the "up to now" crossover point.

Given the current fuel cost differential, where would you expect that
point
to move to assuming the engines were available?

Considering that all the aviation diesels are being built to run on
jet-A, I'd say it's going to stay right where it is.

The only compromise we have to make with the diesels is to give up a
little useful load, otherwise they are equal or better on all counts.
Why isn't that enough for everybody to be excited about?

Best,
-cwk.

Why do we have to give up useful load? On most flights of any duration, the
savings in fuel required will more than make up for the increase in engine
weight (if any)

Mike
MU-2

wrote in message
...
If gasoline hadn't risen to twice the price of Jet-A (at least in parts
of Europe)

3 times. At least for avgas.

Paul

"Peter Duniho" wrote in message
...
Turbines do suffer from manufacturing defects (if I recall, there was an
uncontained failure in the 90's on some rear-engine jet -- 727, DC-9 or
something like that -- where the blade failure was due to some
metallurgical
problem).

Sioux City DC10.

Paul

"Peter Duniho" wrote in message
...
Turbines do suffer from manufacturing defects

http://www.tc.faa.gov/its/cmd/visito...30/turbine.pdf

Howdy!

In article ,
Roy Smith wrote:
In article ,
) wrote:

Think of it this way - a model airplane engine can be made to run with
1/20 of a cubic inch (.049 cu inch to even .010 cu inch), but piston
engine aircraft became impractical above a few thousand HP. That is
the range of practicality for a piston concept.

It is certainly possible to build much larger piston engines than that.
How about http://www.bath.ac.uk/~ccsshb/12cyl/

But it is a *little bit* impractical as an *aircraft* engine...

yours,
Michael


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| White Wolf and the Phoenix
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Roy Smith wrote:

It is certainly possible to build much larger piston engines than that.
How about http://www.bath.ac.uk/~ccsshb/12cyl/

Ah! I've always wondered how that Antonov 225 Mrija was powered...

Stefan

"Paul Sengupta" wrote in message
...
Turbines do suffer from manufacturing defects (if I recall, there was an
uncontained failure in the 90's on some rear-engine jet -- 727, DC-9 or
something like that -- where the blade failure was due to some
metallurgical
problem).

Sioux City DC10.

Not actually the accident I'm thinking of. But yes, that's another example
of blade failure (did they eventually determine it was a manufacturing
defect, or a maintenance problem?).

The accident to which I was referring only involved one or two fatalities,
of a passenger or of passengers sitting right next to the engine.

Pete

I believe you are referring to a Delta MD-80/88 that
was taking off from Pensacola. I think there were
two killed and a couple of injuries.

Mike Pvt/IFT N44979 PA28-181 at RYY

Peter Duniho wrote:
"Paul Sengupta" wrote in message
...

Turbines do suffer from manufacturing defects (if I recall, there was an
uncontained failure in the 90's on some rear-engine jet -- 727, DC-9 or
something like that -- where the blade failure was due to some

metallurgical

problem).

Sioux City DC10.


Not actually the accident I'm thinking of. But yes, that's another example
of blade failure (did they eventually determine it was a manufacturing
defect, or a maintenance problem?).

The accident to which I was referring only involved one or two fatalities,
of a passenger or of passengers sitting right next to the engine.

Pete

"Peter Duniho" writes:


Not actually the accident I'm thinking of. But yes, that's another example
of blade failure (did they eventually determine it was a manufacturing
defect, or a maintenance problem?).

The accident to which I was referring only involved one or two fatalities,
of a passenger or of passengers sitting right next to the engine.


I recall it as well. DC-9, I believe...

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