Question on fuel consumption

"Shemp McGurk" wrote in message
m...
[...]
And from the example you give above, it's about what I thought it
would be: a 747 with, say, 300 passengers is consuming 6 gallons per
mile and a Gulfstream with, say, 10 passengers is consuming 1 gallon
per mile, the per-passenger miles-per-gallon is WAY higher with the
private jet than with the commercial jet.

You have that backwards (maybe because the mileages were stated reverse from
what we're used to in the US).

300 passengers in an airplane that's getting 1/6th of a mile per gallon
winds up being 50 passenger-miles per gallon, while 10 passengers in an
airplane that's getting 1 mile per gallon winds up being 10 passenger-miles
per gallon. The 747 has better mileage by a factor of 5.

That's assuming the figures are actually correct, of course. I can't speak
on whether they are or not.

Pete

"Peter Duniho" wrote in message ...
"Shemp McGurk" wrote in message
m...
[...]
And from the example you give above, it's about what I thought it
would be: a 747 with, say, 300 passengers is consuming 6 gallons per
mile and a Gulfstream with, say, 10 passengers is consuming 1 gallon
per mile, the per-passenger miles-per-gallon is WAY higher with the
private jet than with the commercial jet.

You have that backwards (maybe because the mileages were stated reverse from
what we're used to in the US).


Yes, you're right...I have it backwards but I meant to say what YOU
say below. Instad of saying "WAY higher" I meant to say "WAY worse".


300 passengers in an airplane that's getting 1/6th of a mile per gallon
winds up being 50 passenger-miles per gallon, while 10 passengers in an
airplane that's getting 1 mile per gallon winds up being 10 passenger-miles
per gallon. The 747 has better mileage by a factor of 5.

That's assuming the figures are actually correct, of course. I can't speak
on whether they are or not.

Pete

Of course this is basically true for any two aircraft, the larger one will
get more passenger miles per gallon. A 777 gets a lot more than a 737 for
instance. The same is true for car vs bus.

Mike
MU-2

"Shemp McGurk" wrote in message
om...
"Peter Duniho" wrote in message
...
"Shemp McGurk" wrote in message
m...
[...]
And from the example you give above, it's about what I thought it
would be: a 747 with, say, 300 passengers is consuming 6 gallons per
mile and a Gulfstream with, say, 10 passengers is consuming 1 gallon
per mile, the per-passenger miles-per-gallon is WAY higher with the
private jet than with the commercial jet.

You have that backwards (maybe because the mileages were stated reverse
from
what we're used to in the US).


Yes, you're right...I have it backwards but I meant to say what YOU
say below. Instad of saying "WAY higher" I meant to say "WAY worse".


300 passengers in an airplane that's getting 1/6th of a mile per gallon
winds up being 50 passenger-miles per gallon, while 10 passengers in an
airplane that's getting 1 mile per gallon winds up being 10
passenger-miles
per gallon. The 747 has better mileage by a factor of 5.

That's assuming the figures are actually correct, of course. I can't
speak
on whether they are or not.

Pete

Shemp McGurk wrote:

Actually, your Gulfstream V comparison with the 747-400 is exactly the
kind of thing I'm looking for: the per-passenger miles-per-gallon on a
private jet versus the per-passenger miles-per-gallon on a commercial
jet.

And from the example you give above, it's about what I thought it
would be: a 747 with, say, 300 passengers is consuming 6 gallons per
mile and a Gulfstream with, say, 10 passengers is consuming 1 gallon
per mile, the per-passenger miles-per-gallon is WAY higher with the
private jet than with the commercial jet.

Yes?


The basic concept is the same for airplanes as it is for ground
vehicles. The larger the vehicle the better the "payload mile per
gallon". If you consider the payload of a new 18 wheeler that gets, I
think, over 6 miles/per gallon, to that of the say 40 mpg of some small
cars, you will find that per pound of payload the 18 wheeler gets a lot
better millage. The same is true for airplanes. I would also bet, with
out knowing the exact numbers, that a 777 has a higher "payload mile per
gallon" than a 40 mpg Honda civic. If you go by Payload mile per gallon
per hour of transit time, the 777 number would eclipse the Honda number.

--
Chris W

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(Shemp McGurk) wrote in message . com...
The government routinely publishes a list of miles-per-gallon
consumption ratings for all cars sold in the U.S.

Does anyone know whether such a list exists for aviation?

Miles per gallon measurements don't work that well for airplanes.
After all, there's factors like the plane's headwind or tailwind
speed, and that airplane engines run at higher power output ratings in
cruise than do cars. Flying with a headwind is like driving west at
70 MPH on a road that's moving east at 30 MPH. You're only doing 40
MPH relative to the trees on the side of the road. With a tailwind
it's opposite. And, most of the time you're dealing with one or the
other.

A car is rarely run over 40%-50% of potential power output. While
higher power's useful for hills, or for passing, the average RPM is
much much lower than the max. Airplanes, though, typically run
60%-80% of full power in the cruise phase of flight, the longest phase
by far. So, you're comparing apples and oranges here.

For these and other reasons, airplanes are usually figured at
gallons/hour consumption.

-Malcolm Teas

"Malcolm Teas" wrote

Miles per gallon measurements don't work that well for airplanes.
After all, there's factors like the plane's headwind or tailwind
speed,

airplanes are usually figured at
gallons/hour consumption.

-Malcolm Teas

Yes, we all know that, but approximations (meaningful ones) can still be
made. Yes, you would have to figure with no headwind, and direct route, (or
airways for big stuff) and you would do the same for the ground
transportation. Reality would be different, but that is beside the point.

Figure fuel used for a round trip to a destination far enough away to allow
getting to cruise altitude, then figure gas mileage for a car for the same
destination, and there you have it.
--
Jim in NC


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"Shemp McGurk" wrote in message
om...
The government routinely publishes a list of miles-per-gallon
consumption ratings for all cars sold in the U.S.

Does anyone know whether such a list exists for aviation?


It does not exist. The usual method of predicting fuel mileage in an
airplane is to take the gallons per hour, which is relatively constant at a
particular altitude and power setting, and then find out how long it will
take to reach the destination, taking into account wind, payload, and other
factors.

Some small single piston engine planes can easily exceed thirty miles per
gallon, while others are doing well to get a third of that.

Most of the manufacturers post performance specs on their web sites for
various models of aircraft. Boeing, Airbus, Raytheon (Beech), Bombardier,
Cessna, Cirrus, Piper, Lancair, Mooney, Diamond and many other manufacturers
all maintain good web sites that will tell you how their airplanes perform.

Most pilots would look at a government listing of miles per gallon with some
suspicion anyway. Pilots like their fuel consumption figures to be a little
more accurate than the list that is published for automobiles. After all, we
can't just pull over to the side of the road if we run out of gas.

"C J Campbell" wrote in message ...
snip
Some small single piston engine planes can easily exceed thirty miles per
gallon, while others are doing well to get a third of that.


I'm curious, CJ. Can you provide an example of a light single that
easily exceeds 30 mpg? Most of the more common ones (172, PA28,
etc..) tend to average around 15 to 18 mpg, depending on the power
setting.

John Galban=====N4BQ (PA28-180)

On 22 Oct 2004 13:58:31 -0700, (John Galban)
wrote:

"C J Campbell" wrote in message ...
snip
Some small single piston engine planes can easily exceed thirty miles per
gallon, while others are doing well to get a third of that.


I'm curious, CJ. Can you provide an example of a light single that
easily exceeds 30 mpg? Most of the more common ones (172, PA28,
etc..) tend to average around 15 to 18 mpg, depending on the power
setting.

30 mpg is tough to come by in a plane, but some of the smaller
experimentals can probably do it.

The Q200 and Pulsar come to mind. Both are running 180mph
around 6gph.

"John Galban" wrote in message
om...
"C J Campbell" wrote in message
...
snip
Some small single piston engine planes can easily exceed thirty miles
per
gallon, while others are doing well to get a third of that.


I'm curious, CJ. Can you provide an example of a light single that
easily exceeds 30 mpg? Most of the more common ones (172, PA28,
etc..) tend to average around 15 to 18 mpg, depending on the power
setting.

I know a guy who claims to get that in his Long-EZ, and my brother says he
will probably get that or better in his Celerity Mirage if he ever finishes
it.