The airbus can hold an extra 100 passengers but burns 12% less fuel. Is the 747 just an old design? How does a 787 Dreamliner compare with its airbus counterpart?
The 747 is an old design. The newer planes have the advantage of composite materials, computer aided design, tremendous advances in flight controls and instrumentation, newer and more efficient engines… the list goes on and on. It’s the difference between a 1965 Buick and a 2013 Buick. About all the planes have in common is the ability to fly.
At the same time, note that a plane designed in the 1960s is only 25% less efficient than one designed in the last decade. That the 747 is only disadvantaged that much is a testament to how right they got it when they designed it.
I can believe that but I don’t know enough about plane design to know what they got so right or why. Could you explain that?
Also, OP, that 12% fuel economy, is that total or per passenger? Because if it’s the latter, maybe it’s more efficient not despite having more passengers but because of it.
Keep in mind that the 747 has at least a dozen iterations, each improving on the last in some way, and many older airframes have been refitted with different wings, wingtips, empennage, stretched upper deck, engines, etc. So the comparison would have to be looked at carefully to see whether it’s an original 747 (not fair) or a much newer iteration.
The 747 is an older design. The engines have been upgraded in the 747 over time for thrust and efficiency gains but are still not in the same class as the A380. The A380 uses the Rolls Royce Trent 900 or an Engine Alliance GP7000 (mix of GE and Pratt & Whitney designs upgraded) engines. The later engines are specifically designed for low noise and efficiency. They have a larger diameter and higher bypass ratios [more fan thrust less direct engine thrust]. You just can’t throw larger diameter engines on the 747 without major redesign and certification hurdles.
The 787 uses even more efficient engines (RR Trent 1000s or General Electric GEnx) and there are only two of them. The 787 and Airbus 380 are in different classes of passenger carrying [787 carries 234-296 passengers; A380 carries 585 up to a mind boggling 853 bodies]. [specs subject to change at any time]
The somewhat direct competitor for the 787 is the A350 [not quite out yet]. You can read Wiki for the specs. Engines will be similar but not identical to the 787. The A350 will have a slightly larger passenger load.
More specs available through Wiki or the manufacturer websites.
The engines aren’t necessarily a major factor. They can be upgraded. While the design might limit what newer engines can be swapped in, there’s still enough options that you could have newer, more efficient engines in a given 747 than in a given A380.
The 747’s design had the predicted SST market in mind. So they made it fast and with the cargo market in mind once SSTs took over. (!) So it is also heavy. Neither parameter is good for fuel economy. (Which is why really long range 747s didn’t come out for a while.)
No one’s actually putting that many people in an Airbus A380. The most passengers currently is 538.
Engine efficiency - which comes from higher burn temperatures and higher bypass ratios. Higher bypass requires a larger diameter engine, so there is a limit to what you can do for an older design.
Wing design affects efficiency, the application of more CFD and FEA gets you incremental gains here. A new wing design is about half way to a new aircraft. Incremental changes to the basic structure are much easier. Wings have to cope with a very wide range of conditions, so the difficulty is in marrying the most efficient cruise design with a design that provides enough low speed performance to allow the plane to take off and land at low enough speeds and at all possible operational conditions. And do this without huge heavy complexity.
Mass of the aircraft. Bigger planes tend to have lower mass per passenger. And advances in composite construction obviously can make a big difference.
Not exactly sure, I was watching the TV show “Mighty Planes” and they threw out that fact in the first 3 min of the show. I personally interpreted it to mean a fully loaded A380 burns 12% less fuel than a 747 over the same distance. Also I wouldn’t think that fuel used per passenger would be a good evaluation since airplanes have 1st class, business class and coach seating. Much harder to compare with 3 variables
It is always per passenger. The issue of passenger class is simply normalised to an economy class equivalent. Airlines care about per passenger numbers as that is how they make their money.