The rudder is attached to
the vertical stabilizer. The pilot uses the rudder pedals in the cockpit
to control the yaw of the glider, moving it about the vertical axis.
The rudder does not turn the glider. It is used to coordinate the turn.
In other words to keep the flight path of the glider tracking around
the turn. Let's take a look at turning flight.
 
Turning Flight
The glider must be banked because the same force (lift) that sustains
the glider in flight is used to make the glider turn. The glider is
banked and back pressure on the control stick is applied. This changes
the direction of lift and increases the angle of attack on the wings,
which increases the lift. The increased lift will pull the glider around
the turn. With the wings level, lift acts directly opposite of gravity.
However, as the glider is banked, gravity still acts in a vertical plane,
but lift will now act in an inclined plane. During a turn, lift can
be resolved into two components; vertical and horizontal. The vertical
component opposes gravity, and the horizontal component opposes centrifugal
force. During a turn, the horizontal component of lift must overcome
centrifugal force. Therefore, the horizontal component of lift turns
the glider.

Adverse Yaw
When you roll into a turn, the aileron on the inside of the turn is
raised and the aileron on the outside of the turn is lowered. The lowered
aileron on the outside increases the angle of attack and produces more
lift for that wing. Since induced drag is a by-product of lift, the
outside wing also preduced more drag than the inside wing. This causes
a yawing tendency toward the outside of the turn called adverse yaw.
Coordinated use of the rudder and aileron corrects for adverse yaw and
aileron drag.

Slipping Turn
In a slipping turn the glider is not turning at the rate appropriate
for the bank being used, since the glider is yawed toward the outside
of the turning path. The glider is banked too much for the rate of turn,
so the horizontal component of lift is greater than the centrifugal
force. Equilibrium between the horizontal lift component and centrifugal
force is reestablished either by decreasing the bank, increasing the
rate of turn, or a combination of the two changes.
 
Skidding Turn
A skidding turn results from an excess of centrifugal force over the
horizontal lift component, pulling the glider toward the outside of
the turn. The rate of turn is too great for the angle of bank. Correction
of a skidding turn thus involves a reduction in the rate of turn, an
increase in bank, or a combination of the two changes.
 
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