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Spinning 101

Spinning 101

Recovery procedures that work—and ones that don’t

Spinning 101

Up to this point, the flight had been routine. Wide clearing turns ensured that this piece of sky was ours alone, and treated us to another view of the patchwork of fields and forests that constitute the valley southwest of the Cumberland Plateau. This quiet part of Tennessee offers a perfect training environment.

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.

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.

Spinning 101SPINS 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.

WHY SPIN TRAINING? Given that spin and recovery characteristics can vary considerably, does it still make sense to receive spin training in one particular make and model of airplane? Absolutely. You can memorize spin recovery procedures all day long, but until you’ve actually experienced a spin, how do you know you’d have the wherewithal to execute a recovery during an emergent situation? Pushing forward on the yoke during a spin can be downright counterintuitive—would you react correctly? How would you know what the appropriate control
pressures are?

One of the most important benefits of spin training is learning to perform a checklist (one from memory in this case) efficiently while the airplane is in an unusual attitude. To be sure, your first few spins will be eye-opening. Soon, your ability to assess the situation and act accordingly will improve dramatically. At a certain point, spins even become fun.

If stalls are uncomfortable, spin training can be just the thing. Last year I heard from Jack, a student pilot who had been signed off for his checkride. But Jack had an intense fear of stalls and could not envision taking his practical test. He decided to take the spin course. He learned that in the proper setting—an airplane approved for intentional spins, generous altitude in the proper airspace, great flight conditions, and knowledge of spins on board—spinning can be fun.

Without all those ingredients, however, spinning can turn disastrous. Jack returned home and completed his checkride with a keener ability to recognize the onset of a spin—and the confidence of knowing he can stop it.

For many pilots, stalls form the edge of the comfort zone because we all know that a spin could be lurking just around that corner. Spin training turns that corner in a safe, relaxed environment. Truly, there is nothing like going over the edge to recognize and appreciate the edge itself.

Catherine Cavagnaro

Catherine Cavagnaro is an aerobatics instructor (aceaerobaticschool.com) and professor of mathematics at Sewanee: The University of the South.

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