pros and cons of wing placement on an aeroplane

bill nye scienceguy!

I guess the thread title says it all: what are the benefits of having a wing fixed to the fuselage at the shoulder as compared to mid or low fixing and vice versa?

mgb_phys

Pretty much convenience on the ground - it doesn't make a lot of aerodynamic difference.
You need to stop the engines dragging in the dirt, so the larger the engine (or propeller) the higher the wing has to be, but that makes the landing gear long and expensive/heavy - if it is mounted from the wing.
But having a high wing lets you have a fuselage very close to the ground, as on most transport aircraft so they are easier to load.
It also effects where you put the wing spar (where the wing goes through the fuselage) a high wing on a cargo plane gives you a flat load bed for easy loading but on a passenger plane means that the headroom in the cabin is reduced (like banging your head in a BAe146).

The main aerodynamic effect is on the tail. If you have a high wing the wash from the wing effects the horizontal stabiliser and you need either a much larger one (like on a C130) or a T tail to lift the stabiliser out of the way (like a C5, BAe 146 or most civil turboprops)

bill nye scienceguy!

thanks, that's been bugging me for a while - I thought it would have had something to do with stress in the fuselage.

Mech_Engineer

The wing's location with respect to the aircraft's center of gravity plays or role in determining its aerodynamic stability and maneverability. In some cases, balancing the center of gravity at or slightly over the wing can have positive effects on aspects of the aircraft's maneuverability (as in the case of fighters or aerobatic aircraft.)

berkeman

Quiz Question -- Why are the Corsair's wings bent?

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minger

God bless wiki

berkeman

Ding-Ding! We have a winner. Back in the days before wiki (heck, before Al Gore invented the Internet!), I used to sit and watch Black Sheep Squadron, and wonder, why in the world would you design a wing like that? I finally found the answer in an aviation book about fighter designs.

djeitnstine

When will we return to the good old days where we read books to find our information.

Nick Bruno

I disagree with mgb in post #2. Aircraft with wings lower on the fuselage have better rolling capabilities, but is fairly unstable. Wings mid fuselage are designed for manuverability and are still pretty unstable. Wings on top give the best stability but less manuverability.

Its been a while since I have looked at this stuff (so the above information may be presented wrong), but I know that the placement of the wings has a large roll, no pun intended, in determining the manuverability and stability of the craft. I agree with post #4.

mgb_phys

True, but that's not usually the main driver, except for aerobatic aircraft and fighters.

Most commercial aircraft have low mounted wings because it makes the best use of fuselage space, even when (like the hamster cheek engines on a 737) it makes other parts more difficult.
Most high wing commercial aircraft are either turboprops or transports - but this is not for extra stability.

Nick Bruno

Interesting. I like to see how things differ from... say, real life, to things people think about while designing a model or RC plane with information they get from school or the technical aspect.

That real life experience is where the good stuff is, but at the same time I think it tends to produce paradigms.

el capitan

interesting.... what would be the differences between the types of engines used on different types of wing structure though ?? for instance, what would be the differences between a turboprop installation on a high wing aircraft (such as a c-27j spartan), and a turbofan installation on a 747 or a380 for instance (wide bodied aircrafts).

DaveC426913

I had always assumed it was somehow an efficient shape for dive-bombing.

Gannet

All three positions provides a flyable monoplane aircraft. Whether the position is a pro or con is directly dependent on the aircraft mission.

Most monoplane aircraft that have the same mission usually have the same wing position.

High Wings has the following attributes:

• uninterrupted lift surface has highest oswald efficiency factor
• fuel in wet wing can be gravity fed to engine; however, this also makes it more difficult to fill and increase potential for fire in a crash
• longer takeoff run than a mid- or low-wing
• shorter landing roll than mid- or low-wing (wing in ground effect)
• cantilevered wing requires full depth and width wing spar usually right where the pilot head wants to be
• Excellent downward visibility; however, poor upward visibility which is required when in a turn
• Most stable of the three positions; thus, poor in maneuverability
• easier for passengers and cargo to ingress and egress
• highest structural efficiency when wing is externally braced (reduce wing spar cross section and wing skins also, braces are in tension during highest load condition)
• Easiest to fly, but boring

Low Wings attributes are usually the reverse of the high wing attributes and the mid-wing is somewhere in between

Cyrus

Those are fine points Gannet.

DaveC426913

Indeed, I have learned much.