We recently published a technical article on why aircraft stalls happen and how to prevent them. In short, a stall can occur when an aircraft reaches its critical angle of attack, causing a reduction in lift and, eventually, loss of altitude and control.
When recovering from a standard stall, pushing the nose down will get air flowing over the wings again, and when safe to do so, pilots can smoothly pull up while adding power to fly level again. Some kinds of stalls can be more challenging to recover from, such as a deep stall where a T-tail renders the elevators ineffective, but what if you find yourself in a spin?
What is a spin?
Spins are a yaw-aggravated stall, resulting in a downward spiral or corkscrew path. Although both wings are in a stall in this state, one is significantly more so than the other. Drag on the more deeply stalled wing increases while, at the same time, the higher wing generates comparatively more lift.
Combining these forces makes the aircraft auto-rotate toward the lower wing with more drag, putting it into a fully developed spin and leading to the helix shape as it falls.
How to recover an aircraft in this situation?
Recovery may be impossible if the aircraft’s center of gravity is too far aft. Otherwise, a four-step procedure with the acronym “PARE” may break the stall on both wings during an upright spin. To begin, “P” stands for “Power Idle.” For smaller aircraft, where a spin is more likely to occur than massive airliners, cutting the power can help pilots get the plane into a nose-down position.
Next, you have “A,” which means “Ailerons Neutral.” By removing any aileron input and bringing things to neutral, the wings can more easily reach a similar angle of attack, reducing the yaw motion. If you try to force the inside wing up with ailerons, you’ll increase its angle of attack, potentially making the situation direr. Rolling the ailerons into the spin may accidentally force a spin in the opposite direction. So how do you stop the yaw motion?
“R” stands for “Rudder Opposite,” and as you probably guessed, it means to add rudder in the opposite direction of the spin. This action should eventually stop the rolling and yawing movement the aircraft has placed itself in, and with this step complete, the plane is ready for recovery.
The final step is “E,” or “Elevator Through Neutral.” Applying forward elevator will bring the aircraft back under the critical angle of attack, and though initially, it may feel like you’re spinning straight down, this will quickly break the stall. Once the plane flies out of the spin, you should return the rudder to neutral, bring the nose up, and add power to reenter controlled flight.
Difference between a spin and a “flat spin.”
As with any stall, spins can happen regardless of speed. And in the case where forward airspeed has dropped to zero, the plane spins around its vertical axis as it plummets straight down in what’s called a “flat spin.” A flat spin is less recoverable than a standard spin, though the procedure to try first is the same. If recovery is impossible due to a lack of airflow over the elevator, adding power first may make rudder and elevator inputs more effective.