Cessna Anticipates AvGas Demise

Bertie the Bunyip wrote:
"Gig 601XL Builder" wrDOTgiaconaATsuddenlink.net wrote in
:

Larry Dighera wrote:
CESSNA TO OFFER DIESEL SKYHAWK
(http://www.avweb.com/eletter/archive...ll.html#196294)
Cessna will offer the 172S Skyhawk with a Thielert turbo diesel
engine with deliveries to start in mid-2008. In an announcement at
AOPA Expo in Hartford, Conn., Cessna officials said the decision to
offer the diesel came after extensive market surveys and flight
testing. "The Skyhawk is already the best-selling, most-flown
airplane ever with more than 43,000 delivered and this option further
expands the market due to the worldwide availability of Jet A fuel,"
said John Doman, Cessna vice president of propeller aircraft sales.
Cessna will install the engines at its Independence, Kan., factory
under the supplementary type certificate already held by Thielert.
Am I missing something? Where in that story does Cessna anticipate the
demise of AvGas?


They'd have to be pretty stupid not to anticipate it.
There were, after all, only a certain number of dinosaurs.

I've never seen the exact count of Avgas dinosaurs vs. Jet A dinosaurs.
Can you tell us how many there were of each specie?

Matt

On Oct 5, 12:46 pm, "Gig 601XL Builder" wrDOTgiaconaATsuddenlink.net
wrote:
wrote:
On Oct 5, 10:42 am, "Gig 601XL Builder" wrDOTgiaconaATsuddenlink.net
wrote:
Stefan wrote:
Cessna will offer the 172S Skyhawk with a Thielert turbo diesel
engine

I'd rather say that Cessna is anticipating the difficulty to explain
why they still sell engines with 50 year old technology, once the
pilots start to recognize that there are modern engines around which
burn less than half the fuel.

Are you saying the Thielert turbo diesel burns half the fuel? Wow!!!

A bit more than half. The 135 hp Centurion burns around 4
GPH in cruise. And that's Jet-A, which costs considerably less than
100LL.
The avgas supplies threaten to dry up because the
refineries don't want to bother with it. Avgas constitutes something
like 1% or less of the gasoline market, and carries hundreds of times
the liability. Would you bother with it under those conditions?

Dan

Apples and oranges Dan, the engine that is going in the new Skyhawk is a
turbocharged 155HP. What does it burn?

Dunno that. The original Thielert STC was for a 135 hp engine
in a Skyhawk. Less than the original engine, and a little less
performance because of that, but it generated that hp at about 2300
propeller RPM instead of the Lycoming's 2700 so that less hp would be
lost to drag.
See http://www.centurion-engines.com/

Dan

On Fri, 05 Oct 2007 18:23:29 +0200, Stefan
wrote in :

Cessna will offer the 172S Skyhawk with a Thielert turbo diesel engine

I'd rather say that Cessna is anticipating the difficulty to explain why
they still sell engines with 50 year old technology, once the pilots
start to recognize that there are modern engines around which burn less
than half the fuel.

I like the idea that there is more energy per pound in Jet A fuel than
AvGas, but I have no idea of the failure modes nor expected TBO and
other performance, operational, and maintenance issues. What should a
pilot expect to find has changed in the Thielert engine equipped C-172
other than higher power available at altitude, increased range, and
fewer refueling options?

On Fri, 5 Oct 2007 13:46:06 -0500, "Gig 601XL Builder"
wrDOTgiaconaATsuddenlink.net wrote in
:

the engine that is going in the new Skyhawk is a
turbocharged 155HP

How will that affect useful load compared to the 180 HP equipped
C-172S?

"Larry Dighera" wrote in message
news

I like the idea that there is more energy per pound in Jet A fuel than
AvGas,

Whoa! There is more energy in Jet A per GALLON. Depending on which weight
and BTU averages you are using, Jet A and Avgas come out pretty close on BTUs
per pound. Remember, Jet fuel is heavier than gasoline.

Vaughn

In article ,
"Vaughn Simon" wrote:

"Larry Dighera" wrote in message
news

I like the idea that there is more energy per pound in Jet A fuel than
AvGas,

Whoa! There is more energy in Jet A per GALLON. Depending on which
weight
and BTU averages you are using, Jet A and Avgas come out pretty close on BTUs
per pound. Remember, Jet fuel is heavier than gasoline.

Which weighs more, a pound of Jet-A or a pound of Avgas?

Roy Smith wrote:

In article ,
"Vaughn Simon" wrote:

"Larry Dighera" wrote in message
news

I like the idea that there is more energy per pound in Jet A fuel than
AvGas,

Whoa! There is more energy in Jet A per GALLON. Depending on which
weight
and BTU averages you are using, Jet A and Avgas come out pretty close on BTUs
per pound. Remember, Jet fuel is heavier than gasoline.

Which weighs more, a pound of Jet-A or a pound of Avgas?

Can't tell you

However, I know that my fuel tanks hold 38 gallons. What is that
weightwise for 100LL and Jet-A?

Ron Lee

On Oct 5, 6:41 pm, "Vaughn Simon"
wrote:

Whoa! There is more energy in Jet A per GALLON. Depending on which weight
and BTU averages you are using, Jet A and Avgas come out pretty close on BTUs
per pound. Remember, Jet fuel is heavier than gasoline.


It's pretty close, but Jet A should have slightly higher BTU per pound
due to larger average hydrocarbon molecules in jet fuel.

The biggest difference is that the diesel engines have higher thermo
efficiency than gasoline engine, therefore their BSFC is quit a bit
lower. It burns less pound of fuel per hour to produce the same
horsepower on a diesel engine. Another factor, which only has to do
with economy, is that we pay for fuel in volume (gallons), not
pounds. If Jet A and 100LL are both $4 per gallon, you get more
pounds of jet A with that $4. These two factor combined, diesel
powered Cessna would burn about 30% less $ worth of fuel per hour at
the same power output, assuming JetA and 100LL cost the same per
gallon. That's quite significant. These days it seems that Jet A is
consistently less per gallon than 100LL.

BTW, the 135HP Thielert has a CS prop so that it can put out 100% of
rated power during takeoff and climb. That should produce about the
same horsepower as the 160HP C-172 with a fixed pitch prop.

It's really about time for Cessna to wake up to the fact that the low
end GA is being slowly strangled partly caused by the use of 100LL in
GA fleet. As a fuel, 100LL has this strange economy that the less the
overall consumption, the higher the price delta between 100LL and
autofuel. Remember 100LL requires special handling in the entire
chain of manufacturing and distribution, and it's not transported by
pipeline in the U.S. That largely fixed infrastructure cost has to be
amortized over a ever shrinking pool of consumption. We already see
the average price gap between 100LL and autofuel widen in the last few
years to something more like $1.30 - $1.50. It's going to get worse.
The low end GA, which is most sensitive to the fuel price, is getting
squeezed because 100LL is the only fuel they can use at most airports,
except for a few lucky ones that can use autofuel STC and have access
to ethanol free autofuel.

..

I like the idea that there is more energy per pound in Jet A fuel than
AvGas, but I have no idea of the failure modes nor expected TBO and
other performance, operational, and maintenance issues. What should a
pilot expect to find has changed in the Thielert engine equipped C-172
other than higher power available at altitude, increased range, and
fewer refueling options?

The lower fuel burn comes not from the higher energy of Jet-A, but
rather from the higher compression ratio which converts a higher
percentage of the energy to useful work. Diesel comes closer to an
ideal Carnot cycle than gasoline.

Matt Whiting wrote in news:bvzNi.196$2n4.15991
@news1.epix.net:

Bertie the Bunyip wrote:
"Gig 601XL Builder" wrDOTgiaconaATsuddenlink.net wrote in
:

Larry Dighera wrote:
CESSNA TO OFFER DIESEL SKYHAWK
(http://www.avweb.com/eletter/archive...971-full.html#
196294)
Cessna will offer the 172S Skyhawk with a Thielert turbo diesel
engine with deliveries to start in mid-2008. In an announcement at
AOPA Expo in Hartford, Conn., Cessna officials said the decision to
offer the diesel came after extensive market surveys and flight
testing. "The Skyhawk is already the best-selling, most-flown
airplane ever with more than 43,000 delivered and this option
further
expands the market due to the worldwide availability of Jet A
fuel,"
said John Doman, Cessna vice president of propeller aircraft sales.
Cessna will install the engines at its Independence, Kan., factory
under the supplementary type certificate already held by Thielert.
Am I missing something? Where in that story does Cessna anticipate
the
demise of AvGas?


They'd have to be pretty stupid not to anticipate it.
There were, after all, only a certain number of dinosaurs.

I've never seen the exact count of Avgas dinosaurs vs. Jet A
dinosaurs.
Can you tell us how many there were of each specie?


at least five. I think you'll find that's accurate


Bertie
Matt