How much fuel did we use?
February 23, 2013 11:18 PM   Subscribe

How much jet fuel does it take to get from Vancouver to Beijing?

Five us flew from Vancouver to Beijing return three times on an Airbus A330-300. How much equivalent jet fuel did we use?
posted by miles1972 to Science & Nature (4 answers total) 3 users marked this as a favorite
Airbus says their A330-300 uses 0.04 liters per passenger per kilometer, assuming all seats are full. The great circle flight distance from Vancouver to Beijing, one way, is 8550 kilometers (5300 miles). So each passenger used: (0.04 * 8550) = 342 liters or 90 gallons. For five people that is 450 gallons.

If you had driven in a car that gets 30 miles to the gallon, 90 gallons would have gotten you only about half as far as Beijing. If you put two people in the car, each with 90 gallons, you would be able to drive the distance to Beijing.

So if you compare driving and flying, for a single person in a car, the car uses twice as much fuel. You break even with two people in a car. And with more than two people in a car, driving uses less fuel than flying.
posted by JackFlash at 12:00 AM on February 24, 2013 [3 favorites]

According to Google and, the A330-300 burns approximately 6,000 kg of Jet-A per hour at cruise, so let's use that as an average burn rate since fuel consumption is higher during different phases of flight (e.g., takeoff) and lower during others. That's 7,500 liters per hour at 1.25 L/kg for Jet-A. Now, Vancouver to Beijing takes about 11 hours, give or take. Let's throw in another hour's worth of fuel burn to account for taxiing, flying holding patterns, diversions, and goodness knows what else.

At 12 hours' worth of burn, we're at about 90,000 liters for one trip from Vancouver to Beijing. This is pretty close to the listed capacity of the A330-300's fuel tank (97,530 L). Let's say Cathay Pacific's A330-300 can hold 300 passengers, and their load factor for this flight was 80%, which is a pretty good ballpark. So you're talking about 240 people on each flight, meaning that each passenger was responsible for 375 L of fuel, or roughly 100 US gallons.

You guys flew this distance six times (assuming that's what you meant by return x 3), which gives us 2,250 L (or roughly 600 gallons) total fuel consumption per person. Collectively, the five of you used 375 L * 6 * 5 = 11,250 L, or almost 3,000 US gallons of Jet-A. At current rates (~$3.30/gal), you guys burned almost $10,000 worth of jet fuel overall.

yes, this is what I do with my Saturday nights
posted by un petit cadeau at 12:02 AM on February 24, 2013 [3 favorites]

I think the question has a problem; several, perhaps.

The answer depends on why you are asking and what purpose you hope to serve by posing it. It can be technical or economic. The brevity of the question leaves a lot of room for interpretation and you'll get a bunch of different responses, depending on the listening bias of the responder.

My bias leans towards economics, even though I am an engineer. Most issues seem to have more problematic economics that technological parts. Perhaps because it's 'softer'?

If you are trying to allocate resources, it's tricky. In absolute terms, YOU don't have to pay for the vehicle transport. The plane will fly empty of passengers with slight changes in the fuel economy and if no one bought a ticket, it would return home empty. Almost the entire flight consists of fixed costs. The margin contributed by each passenger is (ticket price - supplies), virtually all margin since it doesn't cost much to get you there... a little food and bathroom supplies, etc. Once the breakeven point is reached, each additional ticket is almost pure profit. If you presume the flight operates above breakeven, you five consumed no additional fuel or supplies (negligible) and so you COULD make the case you used virtually no fuel. (You have to assume, since YOU are evaluating the two alternatives (we went or we didn't went), you were passengers added beyond the breakeven point... all the others would have gone anyway. )

How much incremental fuel did you burn versus empty seats? Again, almost negligible. Your incremental weight was maybe 1100 pounds? (You are all 220 lb / 100 KG mesomorphs in my fantasy.) At about 7 lbs/gallon (.8 kg/L), 1100 pounds is about 150 gallons of fuel. Compare that to the 26500 gallons (97000 L), it's .6% of the fuel weight, basically noise. Add in the aircraft weight and freight weight, and you are well inside noise.

Allocation of costs is pretty tricky. Even the airline's estimate of passenger L/ km has to be parsed for what is really says. There are incidentals all over the place; unallocated costs other than fuel, etc. If you start with that line of reasoning, you've got to allocate the asset cost, the maintenance/inspection costs, downtime, overhauls, licensing, gate fees, yada yada. Where to stop?

If you simplify this to a mind experiment, comparing car driving over an imaginary oceanic highway of exactly the airplane travel path, and not the great circle route, Mssr. JackFlash is on track. Our federal government says a mile is worth about $0.50, give or take. You have one car, 5 passengers, 3 RT at 6K miles each, so the math is trivial. That's the bogey number that supplies 1/2 the answer in an A versus B comparison.

If you use the same approach for the plane, then fuel allocation is only part of the equation, and that's why motive for your question is important. What actual question are you trying to answer? (e.g., should we make this trip or not based on economic or environmental grounds?) Fuel cost allocation only is only one possible response.

I've heard if you put all the economists in the world end to end, you wouldn't reach a conclusion. This is an example of why that's probably true!
posted by FauxScot at 4:22 AM on February 24, 2013 [1 favorite]

The short answer is - it depends.

You can figure the average fuel burn per hour on the aircraft and that will give you a rough estimate. However, there are so many variables that can swing this it's almost incalculable without doing the math AS you take the trip.

Power settings, altitudes, climb and descent profiles, maneuvering and weight are all factors which will affect the burn. Then there is the airline's specific operating procedures (different carriers do different things with the same aircraft, surprisingly enough) which can affect this as well. Then you factor in the weather - head/tail winds have a significant effect on fuel burn.

A bit of Googling indicates that Jet-A fuel weighs 6.8 pounds per gallon. Jet aircraft generally calculate fuel-burn in pounds per hour.
posted by Thistledown at 5:44 AM on February 24, 2013

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