Comments on: Fuel efficiency of airplanes

Question: Fuel efficiency of airplanes

abingham — Tue, 18 Oct 2005 09:24:46 -0800

What is the fuel efficiency of an airplane? How does this compare to other vehicles, both in terms of quantity of fuel consumed and quantity of pollution created (since some fuels, I assume, create different amounts of pollution per unit volume)? I've looked around and can't find any more than some vague generalizations (mostly from airplane manufacturers).

I'm interested in any type of aircraft, although I'm specifically motivated by questions about the efficiency of a large passenger jet. Formulae describing take-off/landing overhead would be great, although a simple "X miles per gallon" is fine too. If passenger and cargo weight are non-negligible in these calculations, I'd like to know their effect.

By: skynxnex

skynxnex — Tue, 18 Oct 2005 09:36:07 -0800

See Google Answers: What is the amount of fuel used in at the very least. It seems to answer at least part of your question. Where, a full plane with 409 passengers: "747-400 plane cruises at 576 mph (927 km/h), burns 12,788 liters (3378 US gallons) of fuel per hour". Which is about 0.171 miles per gallon, if I'm doing my math right.

By: beagle

beagle — Tue, 18 Oct 2005 09:50:47 -0800

Which means also that, in one hour, the jet racks up 235,584 passenger miles; divided by 3378 gallons that yields 69.74 passenger miles per gallon. A sedan driving down the highway with 4 passengers at 25 miles per gallon gets 100 passenger miles per gallon. How about a fully loaded train or bus?

By: fourstar

fourstar — Tue, 18 Oct 2005 09:57:48 -0800

According to Greyhound, their "fleet ... achieves 162 passenger miles per gallon of fuel." If skynxnex's calculations for a 747 are right, it, by contrast, only gets about 70 passenger miles per gallon of fuel. Related Discussion

Also see Fuel-Efficiency of Travel in the 20th Century

By: Chuckles

Chuckles — Tue, 18 Oct 2005 10:17:05 -0800

Great post fourstar!

Of course there are lots of over factors... The resources used and urban impact of airports compared to bus/train stations. The impact of roads vs. track. The crew required to man the infrastructure (flight attendants and pilots, the bus driver, or the highway cops and traffic camera operators).

Does anyone know of an analysis that factors in the energy used by the humans required to operate a particular mode of transport, or even just the staff required per passenger mile?

By: fourstar

fourstar — Tue, 18 Oct 2005 10:18:01 -0800

Also, just out of curiousity I decided to see if smaller jets had better performance (some rough estimates):

Eclipse Aviation's 500:
Range, 4 occupants 1,280 nm / Fuel Capcity 230 gal = ~22.3 pmpg

Gulfstream G 550:
16 people at 6000nm / 6168 gallons = ~16 pmpg

By: mmascolino

mmascolino — Tue, 18 Oct 2005 10:18:46 -0800

fourstar: but also realize tht the 747 is also carrying a lot more cargo per capita than a bus would.

By: alms

alms — Tue, 18 Oct 2005 10:24:39 -0800

This is why the best way to increase the fuel economy of airplanes is schedule optimization, i.e. making sure that every flight is packed full.

By: SpecialK

SpecialK — Tue, 18 Oct 2005 10:50:43 -0800

The other thing that isn't taken into account is the value of immediacy. Where a train or a bus would take upwards of 24 hours at the bare minimum (straight through, team drivers) to reach Los Angeles from Seattle, an airplane makes the trip in an hour or so.

By: trevyn

trevyn — Tue, 18 Oct 2005 11:06:44 -0800

Also, airplanes tend to fly more-or-less in a straight line; following roads requires more miles to go the same distance.

By: weapons-grade pandemonium

weapons-grade pandemonium — Tue, 18 Oct 2005 11:56:54 -0800

Jets apparently waste an enormous amount of fuel as they taxi and wait to take off. Turbofan engine efficiency is two to four times less efficient than a piston engine at low speed and altitude. Do they count this in the stats?

By: Mars Saxman

Mars Saxman — Tue, 18 Oct 2005 15:00:20 -0800

Maybe you've got some hot-shot supersonic rocket plane in your pocket, SpecialK, but on a commercial jet it takes more like two and a half hours to cover the 1200 miles between Seattle and Los Angeles. Still a lot faster than any other mode of transportation, though...

By: wilful

wilful — Tue, 18 Oct 2005 16:44:44 -0800

The value of immediacy to pollution is what? The pollution is more concentrated?

Another pollution concern is where it is put. Jets are inserting their pollution into the high atmosphere, obviously, which means that they're not causing cancer through particulates like diesels, but are effectively injecting proportionately more greenhouse trapping gases (source).

By: SpecialK

SpecialK — Tue, 18 Oct 2005 20:06:57 -0800

Mars: Not to argue, but how can it be two and a half hours from Seattle to LA when it's only an hour and (ten to twenty) minutes (including taxi time) between Portland and LA, a flight that I do every few months?

By: SpecialK

SpecialK — Tue, 18 Oct 2005 20:07:42 -0800

The value of immediacy is the value of time, which has nothing to do with pollution.. yet is more important to the 99% of the population that has too little of it.

By: Chuckles

Chuckles — Tue, 18 Oct 2005 20:45:54 -0800

Immediacy is significant, but not at all because some rich people feel hard done by because they don't have a private jet.

The job of getting Mr. X from A to B takes a certain amount of time. Mr. X consumes a certain quantity of resources per hour. That consumption could be factored in when comparing the impact of different modes of transport.

That is why I brought up the staffing. A crew of 10 on a medium sized plane might account for as much fossil fuel as the plane itself burns... Well, I kind of doubt that, but it I think it would be significant...

By: Mars Saxman

Mars Saxman — Tue, 18 Oct 2005 21:22:47 -0800

Well, that's interesting, SpecialK; which airline are you using? I just looked on the Alaska Airlines site to make sure I wasn't completely losing it, and they list flight times around 2:30 for SEA->LAX and 2:15 for PDX->LAX. But I also checked the Great Circle Mapper and it's only 954 flight miles from Seattle to Los Angeles - the 1200 figure I had remembered was actually the highway distance (illustrating trevyn's point!).

By: logicalrealist

logicalrealist — Wed, 19 Oct 2005 10:52:34 -0800

Weapons-Grade, I'm pretty sure they do not include it. The topic, though, is getting some attention lately -- Boeing tested an electrically powered nosewheel in August. Not anywhere near ready for production yet, but an appealing opportunity to develop.