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We all know that the fin or vertical stabilizer controls
yaw but there are other things that are designed into a plane
that
also will control yaw. Wing sweep is another good
way to add
yaw stability. In figure 1 is a plane with swept wings
that is
flying straight ahead. Both its wings are meeting the
oncoming air
at the same angle, producing the same lift, and
therefore have the
same drag.
In figure 2 the pilot has used the rudder to kick
the nose to
the left. This has drastically changed The angle at
which the
two wings are meeting the oncoming air. When studying the
drawing
you will see that the right wing is presenting more frontal
area
and more lifting area to the oncoming air. The added
frontal
area and added lift will try to force the plane back to
straight
flight. The added lift will also cause the plane to roll
to the
left much the same as dihedral.
Wing dihedral
also offers a great deal of yaw stability. This
is one of those
things that is hard to draw and might be best
left to holding a
wing in your hand and looking at it but an
attempt will be made
here. In figure 3 the wing is being viewed
slightly form the bottom
with the arrow being the actual flight
direction. Wing half a is
yawed into the oncoming air with wing
half b trailing. Wing half a
is at a higher angle of attack than
b and is therefore creating
more lift and drag than b. This drag
will try to put the wing back
in straight and level flight.
The added lift will roll the
plane in the direction of wing half
b. ( Don't laugh too hard at
this one Gene. This is a three
dimensional problem and will always
make anyone squirm when they
try to put it on paper. If you don't
believe me, just ask, I'm
squirming now. We will get it
straightened out through demonstration
and discussion. )
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