overhead wing

[Italy]

was thinking about applicability of using some types of military transports as wide body commercial liners and one of the issues against it was the inefficient engines and wing placement. yet it seems that there's at least two designs that use an overhead wing. is this really a disadvantage? (the location of the wing)

[27vet]

You can achieve a higher mach number with a low swept wing. The high wing design allows for quicker and easier loading of cargo. High wing is better for rough fields.

[Giblets]

Having flown on the 146, the wing spar also restricts overhead storage.

[Italy]

Having flown on the 146, the wing spar also restricts overhead storage.

could you go in detail about that? i'm looking at pics and trying to see what kind of restrictions are there




here's one of the An-148 which also uses an overhead wing

[Distiller]

A high wing with a fuselage landing gear is heavier since the fuselage has to be strong enough to take the loads of both elements. That, however, is offset by the lower weight of a shorter, fuselage mounted landing gear. Also the escape routes are less complex, since you're basically sitting on the ground already and don't need any slides, which again saves weight. Also the fuel system can be designed a little less complex (gravity feed), and one can avoid having fuel lines in the cabin. And then the fuselage adds a little lift in the high wing config. A high wing aircraft can be landed more precise, as there is less ground effect.

But: Then there's interior noise, as all the noise elements of the engine are in direct line of sight of the cabin. Pax don't like that. And the engines on a high wing turbofan are heavier, as there is more "armor" needed against catastrophic failures where vanes could enter the fuselage directly without shielding from the wing.

But the real reason that on fast long-range airliners the low wing dominates is that it has less drag than a high wing, and more so the faster you fly. And the larger the aircraft, the heavier the high wing option is.

[chornedsnorkack]

But the real reason that on fast long-range airliners the low wing dominates is that it has less drag than a high wing, and more so the faster you fly. And the larger the aircraft, the heavier the high wing option is.

By far, the largest planes have high wings. L-100, An-124, An-225.

How does the empty weight of L-100 compare against, say, 747-100? And how does the cruise drag compare?

[Giblets]

could you go in detail about that? i'm looking at pics and trying to see what kind of restrictions are there

You can quite clearly see half way down, the spar crosses and the overhead bins are just about useless unless you have a purse or a wallet to put in them. This is more relevant as more and more people take stuff in their hand luggage.

[Portagee]

How does the Dornier 328 compare?

[mrtotty]

Logically, the drag issue answers the question, but nonetheless, a high-wing version of an airliner the size of an A380 would have one big advantage - you'd be able to see out of the thing.

[Distiller]

By far, the largest planes have high wings. L-100, An-124, An-225.

How does the empty weight of L-100 compare against, say, 747-100? And how does the cruise drag compare?

@ 1: Sure Ro/Ro airlifter have high wings. Belly on the ground, wing high. Belly low and wing low would be ... challenging.

@ 2: No idea, hard data I mean. For larger aircraft the tube (fuselage) has to be more substantial (= usually heavy) to bear the loads from main landing gear *and* wing. For smaller aircraft the question of landing gear weight comes into question, and for airliner also the question of ground support (e.g. stairs) requiremetents.
Drag: It's all about interference drag.

[mordy]

Speaking of overhead wings, and being new in the forum, may I ask the identity of this plane? (There is a second one behind him).

Thanks

[cloud_9]

Looks to be an Ilyushin Il-76?

Here's a better picture...

http://www.military-today.com/aircra...l76_candid.htm

Welcome to the forum!

[mordy]

It sure looks like the Ilyushin il-76.

Thanks

[Mr Creosote]

Don't mean to hijack this thread, but whilst we are on the topic of airliner wings, what is the reason for the anhedral wings on the Tu-134 & Tu154? I guess it may make the undercarriage shorter, but can't be so efficent aerodynamically?

[tenthije]

what is the reason for the anhedral wings on the Tu-134 & Tu154?

From a lateral stability point of view a dihedral wing works has the same effect as wing sweep.

The Tupolev designers valued speed more then efficiency (ye good olde days). To decrease drag they gave the wings a lot of wing sweep. To counter the lateral instability this causes they decided on giving the wing an anhedral profile.

Nowadays with fly by wire it is cheaper and easier to make the planes aerodynamically unstable, instead relying on automated flight controls to maintain stability.

[steven_wh]

Don't mean to hijack this thread, but whilst we are on the topic of airliner wings, what is the reason for the anhedral wings on the Tu-134 & Tu154? I guess it may make the undercarriage shorter, but can't be so efficent aerodynamically?

The weight of the body of the aircraft is below the wings on a high level wing aircraft, which would give it higher stability than a low wing aircraft with the same dihedral . Hence anhedral is the norm for high wings. If an aircraft is FBW, stability can be low as this reduces drag, most modern aircraft are designed for low natural stability.

Steven

[27vet]

Some information on wing design : http://faculty.dwc.edu/sadraey/Chapt...g%20Design.pdf