Re: High wing vs. low wing

Date:         16 May 2001 17:45:28 
From:         westin* (Stephen H. Westin)
Organization: Cornell University
References:   1
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JP Caputa <> writes:

> Why is it that all commercial airliners, aside from perhaps
> turbo-prop feeder liners and the BAe 146 are low winged, where as
> most military cargo planes are high winged. Both types of aircravet
> serve very similar roles, and travel over similar ranges.

Nope, their roles are quite different. Airliners fly in to nice,
civilized airports with jetways, paved runways, and the like. Military
transports might have to fly into dirt strips. They also may have no
tugs to push them back, so reverse thrust will be needed for ground
maneuvering. So getting the engines far from the ground is a Good
Thing to avoid having them inhale something solid. And cargo is
unloaded from airliners by lots of nice machinery, rather than being
driven or towed off. So a low cabin floor is very nice to have in a
military plane.

> I can understand that the purpose of the high winged cargo transports is
> to have the floor of the plane closer to the ground for easier loading
> of cargo, but I'd figure this should be an equally important factor for
> the airlines.

Not as important as making it convenient for passengers. Actually, I
suspect that mechanized cargo handling systems (especially for
containerized freight) make this point moot. The equipment is bought
for efficiency, and would be there in any case; it just reduces the
advantage of a low cargo deck.

> So essencially, the question is:

Well, a low-wing aircraft gets more benefit from ground effect at
takeoff and landing. It lets the wing spar pass through the cargo
area, rather than intruding into cabin headroom. It also is compatible
with worldwide infrastructure built up over the past 45 years or so.
Not to mention the chance to mount landing gear on a low wing, giving
a nice wide stance without lots of extra structure.

Regional airliners have a mission much more similar to that of
military transports: more primitive airfields with less infrastructure
for ground handling. So it makes sense for them to use high wings.

-Stephen H. Westin
Any information or opinions in this message are mine: they do not
represent the position of Cornell University or any of its sponsors.