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Why No Upper Wings On Wide-bodies?

Wed Sep 15, 2004 9:17 pm

I was wondering, when you look at some massive upperwing planes like the C-5, and the antonov planes , why there are no big pax-jets with upperwings.
What would be the disadvantage if, 747,777,340 would 've been build with upperwings?
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RE: Why No Upper Wings On Wide-bodies?

Wed Sep 15, 2004 9:34 pm

On those big cargo jets, the nose door opens so that the entire fuselage can be used for cargo. The wing would be in the way if it were mounted in the "standard" position, so it was remounted above the cargo hold, out of the way. Pax jets don't require this, and, IMO, except for the 146, overhead wings are sort of unappealing. You get that big bump on the top of the fuselage  Big grin
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RE: Why No Upper Wings On Wide-bodies?

Wed Sep 15, 2004 9:39 pm

I think that maintenance could be more difficult, also the walk round would be more difficult.
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RE: Why No Upper Wings On Wide-bodies?

Wed Sep 15, 2004 10:00 pm

Correct me if I'm wrong, just a guess...

Upper wing have better STOL performance, in detriment of comfort... For example, when landing standard wing gives more comfort due to a greater ground effect. Also, Upper wing planes tend to be slower, no?
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RE: Why No Upper Wings On Wide-bodies?

Thu Sep 16, 2004 12:02 am

High winged aircraft, as they are called, can avoid FOD damage easier. This is important for military jets but not for airliners.

High wing gives:
- Harder engine maintenance.
- Wing box goes through the cabin instead of the lower fuse.
- Better engine ground clearance.
- Tricky undercarriage construction. Either in the fuse or on long legs on the wing. Neither method is optimal unless you want the fuse sitting very close to the ground. This is ok if you have a sloping rear fuse due to a cargo door, but that kind of rear fuse makes it hard to install seats all the way back.
- Closer to the ground is good if you are loading outsize cargo. For pax and normal cargo it's less of an issue.
- I will leave the aerodynamics to the experts  Big grin

One of the 747 concepts was mid winged and double decked btw.
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
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RE: Why No Upper Wings On Wide-bodies?

Thu Sep 16, 2004 3:25 am

Just to expand on what Starlionblue is saying, in the end, you have a heavier aircraft. The extra weight results from either the complex structure around the undercarriage (ie C5, all the weight of the wing must pass through the fuselage to the landing gear) or in a very long main landing gear. In the end, it is just cheaper and less complex to build commercial airplanes with the standard "cookie cutter".  Smile

Air transport is just a glorified bus operation. -Michael O'Leary, Ryanair's chief executive
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RE: Why No Upper Wings On Wide-bodies?

Thu Sep 16, 2004 4:44 pm

Auae, Starlionblue,
good points raised.

I’d like to chime in with a major structural concern. With a high wing, you have to transfer all the forces of flight flight up to the wing through the central part of the fuselage. Major weight concern there.

Furthermore, should there be an accident... you better have paid very close attention to what Auae said about reinforcing the central fuselage to take up the forces of landing or you will have the wing spar and wing (full of fuel) come crashing down through the passenger compartment.

I thought I was doing good trying to avoid those airport hotels... and look at me now.

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