Re: What effect does wing shape and placement have on an aircraft????

Barry,

Wing design information is tough to find because it is relatively complex.
I'll try to summarize some of the major design features and the tradeoffs
involved.

    I'll start with the differences when the plane is viewed from in
front:

The earliest wing configuration, used by the Wright brothers 
(http://www.wpafb.af.mil/museum/early_years/ey1.htm), was a bi-wing design.
This has one wing over the other and both wings are straight.  The 
advantage is that by connecting the wings together with wires and/or 
struts, the wings are stronger.  The disadvantage is that the wires and 
struts create added drag making this design very slow.

Later, designers tried single straight wings.  Single wings are more
aerodynamic so the planes can fly faster.  Some are high on the fuselage,
some are low, and a few are mid-wing designs.  For the most part, the
only difference is the preference of the designer.  The practical
differences mostly relate to ground operations based on the size of the 
aircraft.  On small aircraft, a pilot can walk under a high wing (like a 
small Cessna [http://cessna.com/]) instead of having to walk around (like 
a Piper [http://www.newpiper.com]).  For large commercial planes, a low 
wing is often more practical so maintenance is easier to perform.  This is 
especially true for planes with engines mounted below the wings.  Military 
cargo planes, though larger than some commercial jets, have high wings 
because they may have to fly from "unimproved" fields and dirt and stones 
could cause damage if the wings were placed lower.

    Now the differences in wing planforms when viewed from above:

The ealiest design was the straight wing.  These stick out from the sides
and have a constant chord (the distance from the leading edge to the
trailing edge of the wing) and look rectangular viewed from above.  These
are still found on many small airplanes today.  They are easier and 
cheaper to manufacture, and have lower maintenance costs.  However, the 
performance of this type of wing is limited due to drag.

Faster planes will often use a tapered wing, where the chord of the wing is
larger at the wing root (near the fuselage) and smaller at the wingtip.
This design is a little more expensive to make, but allows the wing to be
lighter by putting more of the load closer to the fuselage.  

Wings can also be swept back, giving an arrow head appearance when viewed
from above.  For low speed flight, this offers very little advantage and
costs more to build.  For subsonic high-speed flight, this helps with
stability of the plane and helps to account for different placement of 
cargo and passengers.  For supersonic flight, a swept wing is required to 
help keep the wing behind the shock wave produced by the nose of the 
aircraft.  

In some planes, there is not a separate horizontal tail, just a large wing 
that extends all the way to the back of the plane.  This configuration is 
called a delta wing and is mostly used on supersonic planes like the 
Concorde or the Mirage fighter.


The fore and aft location of the wing is determined by the center of 
gravity (CG) of the plane. The CG is the average location of all mass on 
the plane, including engines, fuel, passengers, and parts of the plane.  
The wing is placed so the center of lift (average location of where the 
wing is lifting) is just behind the CG. By putting it just behind like 
this, the plane will be stable.  If you take your hands off the controls, 
it will fly straight.  An exception to this is on a fighter plane.  
Fighters are designed with the CG behind the center of lift to make it 
unstable.  This makes it more difficult to fly (often computers are used 
to keep it flying straight), but allows it to turn very fast for fighting 
other aircraft.  

A less common, wing planform is a canard airplane.  This type has the main 
wing at the back and a winglet up front.  This is an efficient design that 
is found on the Beechcraft Starship, and several kit-built airplanes.  It 
is a more efficient design than a "conventional" airplane, but not as 
popular because it "doesn't look right".  

The aspect ratio of a wing is found by dividing the length of the wing by
it's chord.  Sailplanes have long skinny wings (high aspect ratio) which is
very efficient so they can stay up in the air a long time without an 
engine. However, this limits the top speed of the sailplane.  Fighter 
planes have short stubby wings (low aspect ratio) because they must fly 
supersonic and the wings need to be kept behind the shock wave from the 
nose.  This design is not very efficient, but is required due to the job 
the plane is designed to perform.

    Now the difference looking from the side:

The thickness of the wing depend on the speed the aircraft will fly.  For
low speed airplanes, a thicker wing will be more efficient.  It'll provide
more lift and allow for slower takeoff and landing speeds.  For high speed
planes, a thin wing is better because it produces less drag, but it must 
fly faster or the wing won't be able to hold the plane up.  

There are several exceptions that can be found to the above guidelines:  
    *The Bell X-1, the first plane to break the sound barrier, had a
straight-tapered wing.  It had to use the brut force of 4 rockets to push 
it supersonic, but the wing was very inefficient for this use.
    *The X-29 (http://www.wpafb.af.mil/museum/modern_flight/mf36.htm)
and Russian S-39 both use swept forward wings.  There are a few
manueverability advantages to this, but it's difficult to design the
structure so the wings don't break off at high speed.
    *One early USAF fighter had a reverse taper wing with bigger chord
at the wingtips than at the wing root.  This was horrible for the stucture
of the wing.
    *And the Boomerang, built by Scaled Composites, doesn't follow any
of these rules.  The wing is longer on one side and is swept forward.  This
plane was built just to show that they could do it.

When designing a new airplane, the first step is to determine what you want
the plane to do, how fast, how far, what kind of load.  Then you design 
the wing to match the requirements.

Hope this helped answer a few of the questions you have.

Todd Engelman
US Air Force Engineering