Ask A Scientist© Engineering Archive

Index Key:   ENG004
Author:      daniel r eastabrook
Subject:     Placement of airplane wings.
Why do some Air Planes have wings on the top of them and some have them on
the sides and curved back?

Response #:  1 of 2
Author:      david r munoz
To complete the thought, I can not think of an aerodynamic reason to have
the wings on top instead of the side.  However, I believe it is easier to
construct and airplane with the wings on top.  Therefore, I believe that
this type plane could be constructed at a lower cost and thus sold for a
lower price.  
As for the question about why the wings are curved or swept back, one reason
that I can think of is related to the lift force.  The lift force is
provided by the differential pressure between the upper and lower wing
surfaces and this pressure acts on the area of the horizontal wing surface
(assuming no boundary layer separation).  The other basic force that must be
considered in aircraft design is the drag force which is proportional to the
vertical area of the wing.  With a swept wing (or a wing curved back) one
could enjoy a large horizontal area with a small vertical area, thereby
maximizing the lift and minimizing the drag.  This is desirable since to
overcome the drag, we must supply an engine.  The larger the drag force, the
larger the engine we will need to overcome it.

Response #:  2 of 2
Author:      jlu
The choice of wing location does affect the stability of the airplane
somewhat, but it is made primarily for other reasons.  It is much easier to
get in and out of a high-winged airplane.
Wings are swept back on airplanes designed to travel near the speed of sound
or above the speed of sound.  The reason is that near the speed of sound a
"shock wave" forms ahead of the wing.  The more swept back the wing, the
faster the airplane can go before the shock wave forms.