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zeno
12-04-2006, 10:38 PM
How many feet will one gallon of fuel propel a Boeing 747?

outlierrn
12-04-2006, 11:04 PM
IANA expert, but I believe airplane fuel consumption is measured in units of fuel per hour of operation, not distance covered. Flying in a tailwind vs a headwind can make a huge amount of difference in you miles per gallon

Duckster
12-04-2006, 11:10 PM
Fuel

* The 747-400ER can carry more than 63,500 gallons of fuel (240,370 L), making it possible to fly extremely long routes, such as Los Angeles to Melbourne, Australia.
* A 747-400 that flies 3,500 statute miles (5,630 km) and carries 126,000 pounds (56,700 kg) of fuel will consume an average of five gallons (19 L) per mile.
* The 747-400 carries 3,300 gallons (12,490 L) of fuel in the horizontal (tail) stabilizer, allowing it to fly an additional 350 nautical miles.

Source: http://boeing.com/commercial/747family/pf/pf_facts.html

You can do the final calculation.

Suburban Plankton
12-04-2006, 11:29 PM
I'd say 0.2 MPG is damn good for a vehicle that moves 524 passengers at over 550 MPH.

Take that, Toyota Prius!

Richard Pearse
12-05-2006, 12:05 AM
IANA expert, but I believe airplane fuel consumption is measured in units of fuel per hour of operation, not distance covered. Flying in a tailwind vs a headwind can make a huge amount of difference in you miles per gallon

True. Also in large aircraft fuel quantity and use is measured in weight rather than volume. Volume changes with temperature, but the weight of fuel used for a given power setting remains the same. So pounds/kilograms per hour is how it's generally measured.

That's not to say that thinking in terms of miles per gallon is useless, just a little less accurate.

Raguleader
12-05-2006, 03:35 AM
That's not to say that thinking in terms of miles per gallon is useless, just a little less accurate.

Heh, a teacher of mine (retired Air Force B-52 pilot) half-jokingly mentioned that, while on the ground, the B-52 Stratofortress has a gas mileage measured in "Gallons per foot". It was standard practice, so he told us, to load up the bomber with it's payload, then load it well past it's gross takeoff weight with fuel. By the time the plane traveled from the ramp to the start of the runway, it was light enough to take off...

... at which point the plane immediately went to refuel from an airborne tanker. :smack:

He assured us that once you got the damn thing into the air, it was much more fuel-efficient, since wheels on the ground are horribly draggy compared to retracted wheels inside the airplane in the air (and let's not even discuss fuel efficiency for a large jet plane on a treadmill... :D )

Raguleader
12-05-2006, 03:42 AM
True. Also in large aircraft fuel quantity and use is measured in weight rather than volume. Volume changes with temperature, but the weight of fuel used for a given power setting remains the same. So pounds/kilograms per hour is how it's generally measured.

Oh, another random thought, I think fuel for airplanes is always measured in terms of weight. How heavy a plane is is generally held to be more important than the volume of it's contents. If you have 20 gallons of fuel, it makes a big difference to the plane if that 20 gallons weighs 20 pounds or 200 pounds. If you have 20 pounds of fuel, the plane really doesn't care if it's 20 gallons or 200 gallons, as long as you contrive a way to get it inside the plane in a balanced manner.

This is why you keep seeing stretched versions of transport planes (both airliners and freighters), as they figure out that the plane isn't carrying near it's weight limit due to the bulkyness (rather than massiveness) of it's cargo.

Richard Pearse
12-05-2006, 07:17 AM
Oh, another random thought, I think fuel for airplanes is always measured in terms of weight. How heavy a plane is is generally held to be more important than the volume of it's contents. If you have 20 gallons of fuel, it makes a big difference to the plane if that 20 gallons weighs 20 pounds or 200 pounds. If you have 20 pounds of fuel, the plane really doesn't care if it's 20 gallons or 200 gallons, as long as you contrive a way to get it inside the plane in a balanced manner.


In light aircraft the fuel on board is usually measured in volume for consumption purposes, but converted to weight for the weight and balance sheet.

For example, a Shrike Commander has a 156 US gallon fuel tank, a fuel gauge calibrated in gallons, and engine performance charts that give fuel consumption in gallons per hour. Weight is only considered when filling out the load sheet.

Larger transport category aircraft measure fuel in weight for everything from the loading to the fuel consumption.

David Simmons
12-05-2006, 08:57 AM
I'd say 0.2 MPG is damn good for a vehicle that moves 524 passengers at over 550 MPH.

Take that, Toyota Prius!Measured as passenger-miles/gallon an automobile with four passengers gets 120 pass-mi/gal if it is getting 30 miles/gallon. A 747, which isn't as fuel efficient as newer models, with a full load gets 110 pass-mi/gal. That's using the numbers you cite.

butler1850
12-05-2006, 09:29 AM
Measured as passenger-miles/gallon an automobile with four passengers gets 120 pass-mi/gal if it is getting 30 miles/gallon. A 747, which isn't as fuel efficient as newer models, with a full load gets 110 pass-mi/gal. That's using the numbers you cite.

But the 747 is going 550mph. I'd be THRILLED to go that fast in my car, but the onramps would be a real problem. :D

Xema
12-05-2006, 09:33 AM
... once you got the damn thing into the air, it was much more fuel-efficient, since wheels on the ground are horribly draggy compared to retracted wheels inside the airplane in the air
The landing gear certainly adds some drag, but the big problem is the inefficiency of jet engines at low airspeeds and low altitudes. The big improvement when airborne is mainly due to getting the engines into a regime for which they were designed.

Xema
12-05-2006, 09:48 AM
an automobile with four passengers gets 120 pass-mi/gal if it is getting 30 miles/gallon. A 747 ... with a full load gets 110 pass-mi/gal.
And since the real-world load factors for aircraft tend to be substantially better than for cars (which apparently average less than 1.5 occupants), the fuel economy advantage lies with the airliner.

As butler1850 notes, the speed advantage is huge. Fully loaded, the car delivers around 250 passenger-miles per hour; the 747 can exceed 300,000. And 747s can (and routinely do) spend 18+ hours a day in the air, which translates to well over 5 million passenger-miles per day. Since what travelers pay for is passenger miles (with a premium for speed), it's not surprising that Boeing has been selling 747s for nearly 40 years, and can continue to get impressive prices for them.

tdn
12-05-2006, 11:55 AM
The landing gear certainly adds some drag, but the big problem is the inefficiency of jet engines at low airspeeds and low altitudes. The big improvement when airborne is mainly due to getting the engines into a regime for which they were designed.
As I understand it, at high altitudes, a plane will sip fuel the way a supermodel guzzles a milkshake. It doesn't take much power to keep the speed up.

chorpler
12-05-2006, 12:25 PM
Heh, a teacher of mine (retired Air Force B-52 pilot) half-jokingly mentioned that, while on the ground, the B-52 Stratofortress has a gas mileage measured in "Gallons per foot".

Similarly, one of the quizzes in More of the Straight Dope, or whatever the second SD book is called, says that an oil tanker gets 31 feet per gallon. Or was it an aircraft carrier?

Rigamarole
12-05-2006, 12:40 PM
Do they pay standard fuel rates for that fuel? That is, if it takes 60,000 gallons to go from Los Angeles to Melbourne, are they paying the same $3.00/gal (or whatever. $2.50 lately) we are? Or do they get the fuel directly from refineries for less?

lazybratsche
12-05-2006, 12:40 PM
But the 747 is going 550mph. I'd be THRILLED to go that fast in my car, but the onramps would be a real problem. :D

Problem? That doesn't sound like a problem to me . :p

Where's you sense of adventure anyways? Apparently it isn't thirty feet above the road, tumbling end over end, where it should be. ;)

MrSquishy
12-05-2006, 01:16 PM
Do they pay standard fuel rates for that fuel? That is, if it takes 60,000 gallons to go from Los Angeles to Melbourne, are they paying the same $3.00/gal (or whatever. $2.50 lately) we are? Or do they get the fuel directly from refineries for less?Are you under the impression that jet engines run on gasoline?

butler1850
12-05-2006, 02:07 PM
Problem? That doesn't sound like a problem to me . :p

Where's you sense of adventure anyways? Apparently it isn't thirty feet above the road, tumbling end over end, where it should be. ;)

I'd be happy to give it a shot, but my accountant, Mrs. Butler would go :eek: at the wrecked car, husband, and the time I'd have to take away from work!

Now where do I find a tire that could handle that speed for my '05 Subaru Baja... and should I leave the tailgate up or down during cruise? :D

Xema
12-05-2006, 02:07 PM
Do they pay standard fuel rates for that fuel?
I think it's safe to assume that if you're an airline using millions of gallons of jet fuel a week, you should be able to negotiate a discounted price, as compared to someone buying mere dozens of gallons. But no one is going to sell it to you below cost, so you can still expect to spend a lot of money on fuel.

lazybratsche
12-05-2006, 02:31 PM
After a bit of googling, it appears that jet fuel is primarily based on kerosene (which is the petroleum fraction between gasoline and diesel). The price seems to average $4/gallon for Jet A (which seems to be the standard) fuel purchased for general aviation. Cite. (http://www.airnav.com/fuel/) The big carriers probably have deals to get it cheaper, since they probably use the overwhelming majority of it.

Also consider that kerosene will have a slightly higher energy density than gasoline. So, it seems that gasoline and jet fuel prices are somewhere in the same ballpark... probably close enough to continue the back-of-the-envelope price and efficiency calculations here.

Shagnasty
12-05-2006, 02:40 PM
Are you under the impression that jet engines run on gasoline?

Jet engines run on jet fuel which is basically the same thing as diesel fuel you can buy at gas stations. The question isn't that far off.

KCB615
12-05-2006, 04:36 PM
Jet engines run on jet fuel which is basically the same thing as diesel fuel you can buy at gas stations. The question isn't that far off.

Just a nitpick, but Jet A (which the vast majority of jet aircraft run on) is kerosene, not diesel.

Shagnasty
12-05-2006, 05:54 PM
Just a nitpick, but Jet A (which the vast majority of jet aircraft run on) is kerosene, not diesel.

Diesel fuel, kerosene, home heating oil, and Jet A are essentially the same thing except for additives and the way they are treated for tax purposes. They are plenty close enough to ask about costs for an individual versus an airline.

David Simmons
12-05-2006, 08:11 PM
And since the real-world load factors for aircraft tend to be substantially better than for cars (which apparently average less than 1.5 occupants), the fuel economy advantage lies with the airliner.

As butler1850 notes, the speed advantage is huge. Fully loaded, the car delivers around 250 passenger-miles per hour; the 747 can exceed 300,000. And 747s can (and routinely do) spend 18+ hours a day in the air, which translates to well over 5 million passenger-miles per day. Since what travelers pay for is passenger miles (with a premium for speed), it's not surprising that Boeing has been selling 747s for nearly 40 years, and can continue to get impressive prices for them.Hmmm. I can't find this response which I thought I posted earlier.

My post wasn't intended to disparage the 747's fuel economy. And I agree that the airlines load factor is much better than that of automobiles.

Xema
12-05-2006, 09:08 PM
My post wasn't intended to disparage the 747's fuel economy.
And I certainly didn't interpret it that way. In fact you made the essential point: a full 747 provides remarkably fuel-efficient transportation.

Duckster
12-05-2006, 10:50 PM
I think it's safe to assume that if you're an airline using millions of gallons of jet fuel a week, you should be able to negotiate a discounted price, as compared to someone buying mere dozens of gallons. But no one is going to sell it to you below cost, so you can still expect to spend a lot of money on fuel.
Southwest and Alaska Airlines both bought into long-term contracts under a system known as hedging. Scroll a bit more than halfway down on this Congressional House report (http://www.house.gov/transportation/aviation/02-15-06/02-15-06memo.html) on Commercial Jet Fuel Supply: Impact and Cost on the U.S Airline Industry. However, both airlines will lose the contract advantage beginning in 2008. Buy your cheap tickets and fly now!

ShibbOleth
12-06-2006, 07:30 AM
City or Highway?

Johnny L.A.
12-06-2006, 07:33 AM
City or Highway?
Highway. Very high way.

Mr. Slant
12-06-2006, 11:26 AM
Diesel fuel, kerosene, home heating oil, and Jet A are essentially the same thing except for additives and the way they are treated for tax purposes. They are plenty close enough to ask about costs for an individual versus an airline.

You can run any pre-1985 diesel passenger car or truck I can think of on kerosene all day long.

DrCube
12-06-2006, 12:50 PM
You can run any pre-1985 diesel passenger car or truck I can think of on kerosene all day long.

I remember occasionally putting kerosene into the tank of a "deuce and a half", or 2 1/2 ton cargo truck, that we had in the Army. The mechanics used to say a deuce and a half could run on Pepsi-Cola, but I think that was a slight exaggeration. They ordinarily ran on JP8, which was basically deisel fuel. By the way, I think the various kinds of JP fuel used in the Army were different ratings of jet fuel. So yeah, jet fuel is deisel essentially, in my estimation.

Sunspace
12-06-2006, 01:38 PM
So could you run a 747 on biodiesel?

ElvisL1ves
12-06-2006, 05:24 PM
Yes, with a little twiddling of the fuel controls, and the right additives, but those are negotiable in a pinch. Jet fuel is kerosene (paraffin to Brits) is #2 heating oil, essentially. "JP" is a military prefix for "Jet Propulsion" - the US military uses JP-5 for everything, and calls commercial "Jet-A" fuel "JP-8" instead.

You can run a gas turbine engine on almost anything, really, just pump the BTU's in at the right rate, and be careful with starting with low-flash fuels. US military helicopters are qualified to run on ordinary gasoline by simply moving a lever on the engine, for instance.

Common Tater
12-06-2006, 06:22 PM
US military helicopters are qualified to run on ordinary gasoline by simply moving a lever on the engine, for instance.

Really? I never heard that. Is that a Huey thing? The Army always always called the fuel "JP-8", with mumblings that JP-4 was too hazardous. Tanks, Humvees, and helicopters all ran on the same stuff. JP-5 is equivalent to JET A, and JP-8 is equivalent to JET A-1. It ain't cheap, nohow. Clear as moonshine.

Raguleader
12-07-2006, 12:42 AM
Yes, with a little twiddling of the fuel controls, and the right additives, but those are negotiable in a pinch. Jet fuel is kerosene (paraffin to Brits) is #2 heating oil, essentially. "JP" is a military prefix for "Jet Propulsion" - the US military uses JP-5 for everything, and calls commercial "Jet-A" fuel "JP-8" instead.

You can run a gas turbine engine on almost anything, really, just pump the BTU's in at the right rate, and be careful with starting with low-flash fuels. US military helicopters are qualified to run on ordinary gasoline by simply moving a lever on the engine, for instance.

One of the bragging points of the M1 Abrams tanks (and one of the intended design specs) was that it could run on just about any sort of fuel you could find for it, short of wood and coal. Diesel, jet fuel, or gasoline I think were the three choices. If this is a trait of gas turbines in general, then there is a class of US Navy destroyer that can operate similarly.

That said, the Abrams' built in smoke generators only work if it's burning diesel, IIRC. That might have to do with how the generators themselves work rather than any particular trait of the fuel (ie: gasoline might just cause the tank to emit balls of fire from the smoke generators, having an effect roughly opposite to that intended)

Boo Boo Foo
12-07-2006, 06:43 AM
Nothing to contribute - merely to say thank you to everyone who posted in this thread. It was like reading a posting on Wikipedia! :D

King Friday
12-07-2006, 09:27 PM
I don't know about a 747, but I know a C-208 Caravan burns about a gallon a minute.

ElvisL1ves
12-07-2006, 09:32 PM
Really? I never heard that. Is that a Huey thing?Blackhawk too.

The Army always always called the fuel "JP-8", with mumblings that JP-4 was too hazardous.JP-4 does have a slightly higher heating value (energy content per unit weight), reducing fuel burn in mass per hour, but it has a higher vapor pressure and lower flashpoint. USAF only recently abandoned it in favor of JP-5, which the Navy always used due to its greater shipboard safety. But neither is any big deal safetywise compared to gasoline - you can drop a lit match into either one, or kerosene, and it will just quench.

King Friday
12-07-2006, 09:38 PM
Diesel fuel, kerosene, home heating oil, and Jet A are essentially the same thing except for additives and the way they are treated for tax purposes. They are plenty close enough to ask about costs for an individual versus an airline.

The diesel mobile refueling trucks at BWI airport were run on Jet A for years, until the EPA stepped in and said we had to start using diesel fuel.

Also, there was a comment about airplanes measuring fuel in pounds rather than gallons because of weight and balance issues. There's also the expansion and contraction factor. 15,000 pounds of fuel at 30,000 feet is not the same amount of gallons of fuel as it is on the Arizona desert, but it's the same weight.

Xema
12-07-2006, 09:39 PM
I don't know about a 747, but I know a C-208 Caravan burns about a gallon a minute.
For the 747, it's fairly close to a gallon a second.

ElvisL1ves
12-07-2006, 09:42 PM
The diesel mobile refueling trucks at BWI airport were run on Jet A for years, until the EPA stepped in and said we had to start using diesel fuel.The diesel engines now starting to appear in the US (they're common in Europe) are marketed as being able to burn jet fuel. But the EPA doesn't regulate aircraft the way they do ground vehicles.

ElvisL1ves
12-07-2006, 09:43 PM
Er, diesel engines for light aircraft, that is.

Sunspace
12-08-2006, 04:18 AM
Er, diesel engines for light aircraft, that is.Ah. Thank you. My sister has a Jetta wagon TDI, and I didn't remember anything in the manual about jet fuel. :) Jetta fuel, on the other hand...

King Friday
12-09-2006, 10:23 AM
Ah. Thank you. My sister has a Jetta wagon TDI, and I didn't remember anything in the manual about jet fuel. :) Jetta fuel, on the other hand...

That Jetta will most certainly run on Jet A, if you're willing to pay up to $6 a gallon. Just don't get pulled over by a cop with a keen sense of smell, as Jet A is quite pungent.

Since we're on aviation fuels, Avgas is just as illegal, if not more so, to burn in an automible.

Common Tater
12-09-2006, 04:27 PM
Blackhawk too.



Really? Where is the lever at ?

Broomstick
12-09-2006, 04:41 PM
Since we're on aviation fuels, Avgas is just as illegal, if not
more so, to burn in an automible.
Avgas will also completely destroy your catalytic converter due to the lead content.

Common Tater
12-09-2006, 04:49 PM
Avgas will also completely destroy your catalytic converter due to the lead content.

I don't have a catalytic converter in my pickup, for example as it predates emission controls. In this instance there would be no benefit as the engine is incapable of utilizing the high octane. I think it's the tax issues that are a factor, but as far as I know, it isn't illegal to run in race cars and such.

ElvisL1ves
12-10-2006, 08:11 AM
Really? Where is the lever at ?On the fuel pump.

Common Tater
12-10-2006, 08:43 AM
The lever, on the fuel pump, on the engines, of the Black Hawk?

Raguleader
12-10-2006, 03:11 PM
The lever, on the fuel pump, on the engines, of the Black Hawk?

Colonel Mustard, in the hanger, with the fuel pump. :D

Common Tater
12-10-2006, 03:29 PM
It's HanAr, not HangEr... *grumble*

Raguleader
12-10-2006, 03:52 PM
It's HanAr, not HangEr... *grumble*

You just assume I'm talking about a building for storing aircraft. For all you know, he was somehow squeezed inside of a coat hanger.

I can't figure out the mechanics of how that works, but that's my story and I'm sticking with it! :D

David Simmons
12-10-2006, 05:12 PM
It's HanAr, not HangEr... *grumble*And it's HanGar, not HanAr, sea?

Common Tater
12-10-2006, 06:56 PM
Eye was hopping know won wood no tice that...

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