Wing efficientie A380 versus 747

[motor-honda 0]

The 747 has exactly the right size and weight. With an optimum wing it has just the right cruising altitude of 33000ft. A heavier aircraft like the A380 with the right wing should cruise at a lower altitude but is less comfortable. So, as seen, the wing of the A380 is larger and is also mounted a few degrees backwards to improve lift to fly also at an altitude of 33.000ft. However this all will results in a higher drag with higher fuel consumption. The aspect ratio of the a380 WING is also very high which also increase fuel consumption ( its wing is wide but short and not so gracious as the 747 wing which is long and narrow to reduce drag. See the record holder around the world plane which has very long but very narrow wings).

The 747 is so succcesfull because its design has no compromise.

Is this known?

Regards

[Aerosoft Team [Inactive Account] 51558]

The 747 has exactly the right size and weight. With an optimum wing it has just the right cruising altitude of 33000ft. A heavier aircraft like the A380 with the right wing should cruise at a lower altitude but is less comfortable. So, as seen, the wing of the A380 is larger and is also mounted a few degrees backwards to improve lift to fly also at an altitude of 33.000ft. However this all will results in a higher drag with higher fuel consumption. The aspect ratio of the a380 WING is also very high which also increase fuel consumption ( its wing is wide but short and not so gracious as the 747 wing which is long and narrow to reduce drag. See the record holder around the world plane which has very long but very narrow wings).

The 747 is so succcesfull because its design has no compromise.

Is this known?

Regards

Well Airbus claims better fuel consumption per mile and per pound of usable load while cruising speeds are identical or close to identical. And having flown long distances a few times I can only say from a passenger point of view that a aircraft can't be larger enough. lol

[João Pinto 23]

Just one thing regarding the A380's performance.

I am a Boeing man myself. Not just design but also panels and systems, very pilot oriented, much more than "Flying Computers" also know as Airbuses.

BUT

I gotta admit.

Airbus A330 started the new era of fuel efficiency. Like Mathijs said, the A380 is reported to have the best fuel efficiency for a four engined wide-body (forget the A340). The max crz altitudes you mentio, well I don't know where they stand because EADS hasn't released performance charts on the A380 yet.

What I can say is that a fully loaded 744 from VHHH to EGLL cannot cruise above FL350. It has to do with weight and engine efficiency. During flight, however, as the engines burn the fuel and the aircraft becomes lighter then you can reach that magic FL450 (the max).

So, it depends on many variables to ascend to higher flight levels. Not just wings and drag.

[motor-honda 0]

What I try to tell is that teh A380 wing is too large for its weight which is designed to cruise at 33000 ft. Therefor a too large wing has always a more then neede drag and fuel consumption What Aribus mention is the fel ecomomy per lbs load. This is only valid when the plane is fully loaded. Otherwise ( and that is in most cases) the A380 will have less fuel economy then the 747. This is also mentioned by Boeing.

[Aerosoft Team [Inactive Account] 51558]

What I try to tell is that teh A380 wing is too large for its weight which is designed to cruise at 33000 ft. Therefor a too large wing has always a more then neede drag and fuel consumption What Aribus mention is the fel ecomomy per lbs load. This is only valid when the plane is fully loaded. Otherwise ( and that is in most cases) the A380 will have less fuel economy then the 747. This is also mentioned by Boeing.

I bet you that Boeing has some comments on that... But you really have a low confidence in the Airbus engineers (got to be honest, I know a few and some are even friends).

But I will give you the point on economy. The 380 needs a higher load to reach full efficiency. Of course that is rather standard, most new designs need that. It is one of the reasons why Airbus wants to carry more cargo per flight.

But why your attack on the Airbus wing? You seem to know your data.

[motor-honda 0]

I am not attacking Airbus. I am just wondering why nobody write about this issue. It is already known for a long time and it is written in almost every airplane designers books that the design of the 747 is optimum. Larger or smaller planes must have compromises the 747 doesnot have.

Regards.

[João Pinto 23]

Well, I don't suppose Airbus wasted so much time and resources developing simulations and algoritms in supercomputers to make a lower performance or less effective wing.

The point is that the A380 is the heaviest passenger airliner in the world.

And I think you're only thinking of high flight level and high speed performance when you should ALSO think of low level and speed performance when the 380 must keep those tons OFF the ground prior to touchdown and when you roll to lift that beast. This is very critical if you want to hold the aircraft in acceptable runway distance to make aproaches at the lowest speeds. The same goes for runway roll to VR.

The A380 isn't my favourite airplane, but sure is a marvel of science.

Let's wait to see it fly regularly and make our conclusions then, shall we?

By the way, Lufthansa is now making regular test flights with the A380. It will be the first airline to operate the bird with full crew and cabin configs. Even so, it will not be the first to receive the bird... weird...

Anybody lucky enough to see it, pick up those cameras!

[ae_timmy 3]

Dear Motor-honda, I don't know where you get your information from, but not all of it is correct. I am a 4th year aerospace engineering student at Delft University of Technology, I should know a few things about aircraft design.

First of all, there is no such thing as a design without compromises. Secondly an "optimum design" only holds for the design goals / requirements set out at the beginning of the project. If you change the goals (i.e. we want to transport more payload), you're design will change. To my knowledge there is no relation between the amount of payload and cruising altitude. It's a matter of aerodynamic design with respect to the wing. Mostly aircraft are optimized for their cruising altitude, as that is where they'll spend most of their operational life (especially long-haul aircraft as the A380).

On those aerodynamics, you mention the higher aspect ratio of the A380, I am personally not sure if this is true, but I could check if you would want me to. Anyways, a higher aspect ratio will mean less (induced) drag and therefore LESS fuel consumption. If you don't believe me, take a look at glider aircraft, there's a reason for those long and slender wings, gliders love less drag.

Wing placement depends on quite a few variables, one of which would be the position of the center of gravity. Moving the wing forward or aft a little bit doesn't do much for lift generation etc. Changing the "angle of attack" of the wing a little bit doesn't do you much harm at cruising altitude either, it's more a take-off thing, lots of aircraft have such wings.

On the fuel consumption, it would usually be expressed in fuel consumption per passenger kilometer. (Most aircraft and especially the new ones have better mileage per passenger than your average car). As mentioned before, aircraft are designed for certain amounts of payload. One very important factor in the performance of an aircraft is the wingloading (= total weight divided by the wing area, basically the higher the better, there are some exceptions of course) However, high loadings require heavy structures, and in aerospace engineering we don't like heavy structures. So you can imagine that wing design depends on quite a few trade-offs between variables.

Your first claim of the 747 having exactly the right size and weight is strange as well. There are after all different versions, all of which have different "weights" and sizes.

What I guess I am trying to say is that a design depends on a lot of variables and therefore on a lot of design choices. You can debate about the existence of an "optimum" design, but I personally don't believe they exist. Too many design compromises are made in EVERY design. And they will always be there, otherwise nothing would get built.

So finally I guess it is safe to say that you can trust Airbus to have put quite a lot of consideration into their aerodynamic design. There are reasons for why the wing looks like it does. The life of an engineer is not as black and white as you make it seem to be.