Flight Training - September 2014 - 36

Ready. As Pete pulled back on the yoke, increasing the angle of attack, the whine of the stall horn
warned what lay ahead. The ball in the inclinometer
drifted farther away from center, attesting to a lack of
coordination. At the stall, the airplane rolled smartly
to the left-upside down, then right side up once
more. The blaring horn chided that stalled wings are
not part of a natural flight condition. Fields sailed by
faster and faster and became almost a blur. We used
our reference to count the revolutions in this left
spin-one...two...three.
Pete closed the throttle and released the yoke and
rudder controls. The yoke rotated to the left as the
ailerons tucked into the spin. After two additional
turns, the airplane showed no sign of recovery. Pete
next tried deflecting the rudder to slow the rotation
and pushed the right pedal to the floor. Nothing.
Other measures clearly were necessary. Finally, Pete
neutralized the ailerons and pushed forward on the
yoke. In less than a turn the whirring stopped, and he
was able to pull us out of the dive.

THE RUDDER IS NOT SUFFICIENT TO
ARREST THE ROTATION. THE STALL
MUST BE BROKEN FIRST TO ENTER THE
RECOVERY PHASE OF THE SPIN.

36 /

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Pete, my student for the day, had already demonstrated proficiency in recovering from a spin using
the procedure prescribed in the pilot's operating
handbook (POH) for the Cessna 152:
1. Ailerons-Neutral
2. Throttle-Close
3. Rudder-Full Opposite to the direction of the
spin.
4. Yoke-Forward briskly to break the stall.
5. Hold these control inputs until the rotation
stops.
6. Rudder-Neutral and make a smooth recovery
from the dive.
We had moved on to exploring the effects that
various controls have on spin dynamics and recovery. By letting go of the flight controls, Pete saw that
the airplane did not recover by itself, and the rudder
alone failed to slow the rotation perceptibly. In the
Cessna 152, the elevator is the most important control
surface for spin recovery.
SPINS DEFINED. A spin is an aggravated stall with
autorotation-one or both wings are stalled and the
airplane rotates about a vertical axis. The outside,
upward-moving wing has a lower angle of attack and,
therefore, less drag. The inside, downward-moving
wing has a higher angle of attack and greater drag.
If both wings are stalled, the inside wing is more
deeply stalled. This imbalance of forces and moments
perpetuates the rotation. In a stable spin, the inertial
forces increase to balance the aerodynamic forces.
A spin consists of four phases. During the approach
to the stall, the flight path is primarily horizontal.
Following the stall, a lack of coordination results in
a roll and yaw that produces autorotation. During
the incipient phase, the rotation rate increases as the
inertial forces build and the airplane starts descending. It's usually easier to recover from a spin during
this phase. The incipient phase lasts through the
second turn for many general aviation airplanes.
The developed phase begins when the inertial
forces have increased and are in balance with the
aerodynamic forces, and the rotation rate stabilizes.
Here the flight path is vertical and, because of higher
inertial forces, a recovery typically is more difficult.
Finally, the recovery phase begins when a collection
of control movements, in concert, upsets the balance
of forces and the rotation stops. It's the phase that
every spin should have.
Once in the developed phase, the Cessna 152 will
not recover using the "hands-off" approach, as Pete
demonstrated above. In this model, the rudder is not
sufficient to arrest the rotation. The stall must be
broken first to enter the recovery phase of the spin.

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Flight Training - September 2014

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