A spin is an aggravated stall in which an aircraft descends while rotating, often following a steep corkscrew path. It matters because a normal stall can usually be recovered quickly, but a spin adds yaw and roll that make the loss of altitude much more serious. Student pilots study spins to understand why coordinated flight, stall recognition, and correct recovery inputs are essential.
The key idea is that a spin is not just slow flight, it is stalled flight plus rotation.
Key Facts
- A spin requires a stall plus yaw, so both high angle of attack and uncoordinated flight are involved.
- Lift can be estimated by L = 0.5 rho v^2 S CL, but in a stall CL drops because airflow separates from the wing.
- The critical angle of attack is the angle where the wing reaches maximum lift coefficient before stall begins.
- In a spin, the descending wing is usually more deeply stalled and has more drag than the rising wing.
- Standard recovery memory aid: PARE = Power idle, Ailerons neutral, Rudder opposite, Elevator forward.
- Approximate altitude lost in recovery can be estimated by h = rate of descent x recovery time when units are consistent.
Vocabulary
- Spin
- A spin is a stalled, autorotating descent in which the aircraft follows a steep spiral path.
- Stall
- A stall occurs when a wing exceeds its critical angle of attack and airflow separates enough to greatly reduce lift.
- Autorotation
- Autorotation is the self-sustaining yaw and roll motion caused by unequal lift and drag on the two stalled wings.
- Yaw
- Yaw is rotation of the aircraft nose left or right about its vertical axis.
- Rudder
- The rudder is the vertical tail control surface used to control yaw and stop spin rotation during recovery.
Common Mistakes to Avoid
- Using aileron to lift the low wing, which can deepen the stall on that wing and make the spin worse.
- Pulling back on the elevator during recovery, which keeps the angle of attack too high and prevents the wings from unstalling.
- Adding power during the spin, which can increase yawing and rolling forces in many training aircraft instead of helping recovery.
- Confusing a spiral dive with a spin, which is wrong because a spiral dive is not necessarily stalled and requires different control priorities.
Practice Questions
- 1 An aircraft descends at 5000 ft/min during the first 6 seconds of a spin. Estimate the altitude lost during that time.
- 2 A recovery takes 4 seconds after opposite rudder is applied, and the average descent rate during recovery is 3600 ft/min. How much altitude is lost during the recovery phase?
- 3 A student pilot stalls while skidding in a turn with too much rudder. Explain why this situation is more likely to enter a spin than a coordinated stall.