Re: High wing vs. low wing

Date:         16 May 2001 17:45:37 
From:         matt weber <mattheww@Qwest.net>
References:   1
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At 04:40 PM 4/19/01 +0000, you wrote:
>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.
>
>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.
>
>So essencially, the question is:
>
>WHAT ARE THE BENEFITS OF LOW WINGED AIRCRAFT (if any) AS OPPOSED TO HIGH
>WINGED AIRCRAFT?

Most materials take compression loads better (and fail much more gracefully
under them)  then they take tension loads, consequently a low wing aircraft
does not need as strong a wingbox or fuselage as a high wing (lower
weight). The aircraft load is being carried as a compression load with a
low wing as opposed to a tension load on a high wing. Cracks cause far less
trouble in compression loads then they do with tension loads.   Other
issues, high wing gets you more engine clearance, which if you want to run
on not so good air fields (gravel/dirt and shell fragments), is probably
desireable. The impact is very real. When you compare lift capacity as a
percentage of Empty weight, the low wing commercial airlines do much better
then the Military airlifters.

Most commercial cargo is palletized or containerized, so it is easily
loaded with automated loading equipment. A lot of military cargo is
outsize, so it has to be driven on board, so the higher cabin floor really
isn't much of a draw back for a commercial airliner, but is for a military
cargo aircraft.

Matt Weber