Tuesday, February 17, 2009


A spin may be defined as an aggravated stall that
results in what is termed "autorotation" wherein the
airplane follows a downward corkscrew path. As the
airplane rotates around a vertical axis, the rising wing
is less stalled than the descending wing creating a
rolling, yawing, and pitching motion. The airplane is
basically being forced downward by gravity, rolling,
yawing, and pitching in a spiral path. Spin-an aggravated stall and autorotation.

The autorotation results from an unequal angle of
attack on the airplane's wings. The rising wing has a
decreasing angle of attack, where the relative lift
increases and the drag decreases. In effect, this wing is
less stalled. Meanwhile, the descending wing has an

increasing angle of attack, past the wing's critical angle
of attack (stall) where the relative lift decreases and
drag increases.

A spin is caused when the airplane's wing exceeds its
critical angle of attack (stall) with a sideslip or yaw
acting on the airplane at, or beyond, the actual stall.
During this uncoordinated maneuver, a pilot may not
be aware that a critical angle of attack has been
exceeded until the airplane yaws out of control toward
the lowering wing. If stall recovery is not initiated
immediately, the airplane may enter a spin.

If this stall occurs while the airplane is in a slipping or
skidding turn, this can result in a spin entry and
rotation in the direction that the rudder is being
applied, regardless of which wingtip is raised.

Many airplanes have to be forced to spin and require
considerable judgment and technique to get the spin
started. These same airplanes that have to be forced to
spin, may be accidentally put into a spin by
mishandling the controls in turns, stalls, and flight at
minimum controllable airspeeds. This fact is additional
evidence of the necessity for the practice of stalls until
the ability to recognize and recover from them
is developed.

Often a wing will drop at the beginning of a stall.
When this happens, the nose will attempt to move
(yaw) in the direction of the low wing. This is where
use of the rudder is important during a stall. The
correct amount of opposite rudder must be applied to
keep the nose from yawing toward the low wing. By
maintaining directional control and not allowing the
nose to yaw toward the low wing, before stall recovery
is initiated, a spin will be averted. If the nose is allowed
to yaw during the stall, the airplane will begin to slip in
the direction of the lowered wing, and will enter a spin.
An airplane must be stalled in order to enter a spin;
therefore, continued practice in stalls will help the pilot
develop a more instinctive and prompt reaction in
recognizing an approaching spin. It is essential to learn
to apply immediate corrective action any time it is
apparent that the airplane is nearing spin conditions. If
it is impossible to avoid a spin, the pilot should
immediately execute spin recovery procedures.

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