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

"Newps" wrote in message
...


wrote:



If gelling of Jet-A were a problem, airliners would be falling out of
the sky on a regular basis.

It is a problem. It is solved by heating the fuel.

.... and since hydraulic fluid needs cooling they locate the hyd.cooling
coils inside the fuel tank(s). That helps solve two problems.

Excerpted from other posts.......

Any talk about Jet-A jelling sounds....bogus..

If gelling of Jet-A were a problem, airliners would be
falling out of the sky on a regular basis.

It is a problem. It is solved by heating the fuel.


It is a problem on long flights at high altitudes and high
latitudes. The fuel filters on the Boeings that I flew
were heated to prevent the screens from "waxing" over.
The fuel itself was not heated. The filters were heated
with hot engine bleed air and heated for one minute every
thirty minutes when the fuel temperature dropped below zero
degrees celsius.

At PanAm, we had three procedures for dealing with extremely
low temperatures across the North Atlantic.

1. Re-route to a more southernly (warmer) route.
2. Reduce altitude to a warmer OAT.
3. Increase speed for a greater friction effect on the tanks.
At around M.80, the Ram Air Temperature is about thirty
degrees higher than the True Air Temperature.

All of these required extra fuel of course and we depended
on the Dispatcher providing a good Temp Aloft forecast.

Bob Moore
ATP B-707 B-727
PanAm (retired)

Aha,

But much of the cost is due to changing components other than the engine.

If you had a glass cockpit, and fuel system that were compatible to start
with, then all you would need to change was the engine, mount, prop, sending
units, and software.

That would seem to be less than what the europeans are giong through to put
the Theilert in a skyhawk.




wrote in message
...
In rec.aviation.owning Mike Rapoport wrote:

wrote in message
...
In rec.aviation.owning Mike Rapoport
wrote:
The Caravan has a 940hp engine flat rated to 675hp. Turbines are
typically
flat rated so that the engine can make rated power to reasonable
altitudes
and temperatures without having to design the gearbox for the full
thermodynamic horsepower. To keep the comparison with piston engines
apples
to apples you need to use thermodynamic ratings.


http://www.pwc.ca/en/3_0/3_0http://w.../3_0_2_1_2.asp

OK, that explains that.

To put some numbers on things, the engines in my MU-2 have a specific
fuel
consumption of .55lb/hp/hr and a piston engine is about .45 and
diesels
can
be under .40. Huge (ship) diesels can be under .30. Compare your
model
aircraft engines with the TFE731-60 used on the Falcon 900EX which
uses
.405lb/lb thrust/hr

Aha, numbers!

So if one assumes the motivation to switch from a piston to a turbine
is
the price of gas is roughly twice Jet-A, the crossover point would be
a
turbine that did about .8 (to allow for the weight difference in the
fuels).

Any idea how small (in appropriate terms of hp) current technology can
make
a turbine with that consumption?


--
Jim Pennino

That would be the economic crossover point if the engines cost the same.
Of
course a plane that needed twice the fuel (in lbs) to achieve the same
performance wouldn't have much useful load or range.

Dropping a diesel in an airplane costs a bunch. The justification is the
cost is recovered in lowered fuel costs.

Your second point is certainly valid though and a minor problem with the
diesels according to the AVweb article on them.


--
Jim Pennino

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"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
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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

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


--
Michael and MJ Houghton | Herveus d'Ormonde and Megan O'Donnelly
| White Wolf and the Phoenix
Bowie, MD, USA | Tablet and Inkle bands, and other stuff
| http://www.radix.net/~herveus/

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

Mike,

TCM IO-520/550's running LOP are about .39-.40 BPSC according to the GAMI
folks, the SEMA engine is about .33-.35 from their specs. At 70K for their
engine conversion and the cost of JetA being within 10% of the cost of 100LL
at most GA airports I ageree with you and don't think we'll see a lot
diesel's in the near future.

The Diamond Twin really impresses me, can' t wait for an independent
(non-Flying or other slick mag) pilot report to see how it really does.

Ernie
BE36 E-160
KDVO


"Mike Rapoport" wrote in message
k.net...
The Caravan has a 940hp engine flat rated to 675hp. Turbines are typically
flat rated so that the engine can make rated power to reasonable altitudes
and temperatures without having to design the gearbox for the full
thermodynamic horsepower. To keep the comparison with piston engines
apples to apples you need to use thermodynamic ratings.

http://www.pwc.ca/en/3_0/3_0http://w.../3_0_2_1_2.asp

To put some numbers on things, the engines in my MU-2 have a specific fuel
consumption of .55lb/hp/hr and a piston engine is about .45 and diesels
can be under .40. Huge (ship) diesels can be under .30. Compare your
model aircraft engines with the TFE731-60 used on the Falcon 900EX which
uses .405lb/lb thrust/hr

Mike
MU-2


wrote in message
...
In rec.aviation.owning Mike Rapoport
wrote:
About the size of the Caravan 900hp+

Mike
MU-2

According to the Cessna website, the current Caravan is 675hp.

--
Jim Pennino

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On Fri, 17 Sep 2004 12:13:49 -0700, wrote:

A gas turbine scales up easily and but is nearly impossible to scale
down. The auto manuacturers found that out in the 1940s - remember
the "car of the future" on the covers of Popular Science et al?
Turbines for cars are further away now than they were 55 years ago.
The turbine suffers from excessive fuel consumption at part throttle
(the piston engine is incredibly flexible that way)and in smaller HP
installations.
[...]

This is not my recollection. What killed auto turbines was their
spool-up and spool-down time, and gearboxes for 20,000 RPMs.

BTW, remember the rail engines. The turbines there tried to compete
well into 1960s. They were killed by their short overhaul time,
not fuel consumption.

-- Pete

In rec.aviation.owning Pete Zaitcev wrote:
On Fri, 17 Sep 2004 12:13:49 -0700, wrote:

A gas turbine scales up easily and but is nearly impossible to scale
down. The auto manuacturers found that out in the 1940s - remember
the "car of the future" on the covers of Popular Science et al?
Turbines for cars are further away now than they were 55 years ago.
The turbine suffers from excessive fuel consumption at part throttle
(the piston engine is incredibly flexible that way)and in smaller HP
installations.
[...]

This is not my recollection. What killed auto turbines was their
spool-up and spool-down time, and gearboxes for 20,000 RPMs.

BTW, remember the rail engines. The turbines there tried to compete
well into 1960s. They were killed by their short overhaul time,
not fuel consumption.

-- Pete

According to a guy I worked with who worked on the Chrysler turbine car,
the problem that was the straw that broke the camel's back was the under
the hood temperature being too high for all the other stuff under the
hood, i.e. wiper motors, relays, etc.

--
Jim Pennino

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