Airplane ailerons control rolling motion around the longitudinal axis, yet in a spin their effect is reversed. Applied ailerons may increase the spin rate; continuously altering wing lift, they generate stronger drag on the already-low wing and deepen the autorotation. For recovery, most flight manuals direct pilots to neutralize the sticks: neutral ailerons remove lift asymmetry and let the rudder dominate. In some certified designs, however, coordinated aileron-with-rudder inputs are used to change the angle of attack and drag of each wing, helping to break the stall and stop the rotation.
Expert behind this article
Jim Goodrich
Jim Goodrich is a pilot, aviation expert and founder of Tsunami Air.
What is the relationship between spin and aileron in aerodynamics?
Spin is a special category of stall resulting in autorotation about the aircraft's longitudinal axis and is maintained by balance between aerodynamic and inertia forces and moments. When the pilot is able to control the aircraft's roll by turning the control yoke or sidestick, the intended motion is a bank that rotates the airplane about its longitudinal axis. However, once the aircraft enters a spin the same aileron input can slow the roll or, if one aileron is pointed up and the other down, can even cause the plane to fly farther from the spin axis without necessarily stopping the autorotation. Because spin has a shallow rotating downward path approximately centred on a vertical axis, the ailerons operate in a highly disturbed, stalled flow field. Therefore, their authority is reduced and their effect on the roll of the spin is limited to modifying the balance between aerodynamic and inertia forces and moments rather than immediately terminating the spin.
How do ailerons affect a spin?
Manipulating ailerons to correct a dropping wing likely induces spin. Neutralizing ailerons slows a spin by helping both wings reach the same angle-of-attack, reducing rolling and yawing moments. Down ailerons increase the angle of attack of their wing. Raising the inside wing this way drives that wing deeper into stall and makes the spin worse. One aileron up and the other down will aggravate the situation by increasing drag on the already-stalled wing and adding adverse yaw that accelerates rotation. During recovery, ailerons are best kept neutral so the wings stall evenly and the auto-rotative force weakens; the real control is through rudder and elevator.
What happens when you use an aileron in a spin?
When the pilot moves the aileron while the aircraft is already spinning, the consequences are immediate and usually worsen the spin. Raising the low wing using the aileron will stall even more because the inside wing is the low wing in spin and is already at a higher angle of attack than the high wing. Any attempt to lift that low wing increases its angle of attack and therefore its drag, producing an even stronger autorotative force. Downward deflected aileron puts the left outboard wing close to stalling angle, so the increased angle of attack of the left wing reduces lift and increases drag. Simultaneously, the upward deflected aileron on the opposite side still generates maximum lift, but the net effect is that the low wing stalls more deeply. The result is additional asymmetric lift and drag that tightens the rotation instead of stopping it. Thus, the aileron stalls even more because each wing is stalled and the differential aileron deflection aggravates the stall. Consequently, incorrect aileron input is as bad as wrong rudder pedal; the Britten-Norman Islander training incident that ended in a spin began with exactly this mistake.
Using the opposite aileron - rolling the wheel toward the high wing - produces the same undesirable outcome. You are increasing the angle of attack on the outside wing, so the low wing, already at higher angle of attack, is driven still deeper into stall. The extra drag created on the already-stalled low wing forms an even larger yawing moment, so using the opposite aileron in a spin merely accelerates the autorotation. Recovery is initiated by maintaining a pro-spin elevator and rudder only long enough to match the rotation, then promptly applying full opposite rudder and moving the stick forward; small aileron inputs are consciously avoided.
Why must you not use ailerons in a spin?
You must not use ailerons in a spin because ailerons do not work well on a stalled wing. Once the wing is fully stalled, their surfaces sit in separated airflow, so deflecting them cannot create useful lift. Instead, they add drag and deepen the autorotation. Using ailerons while stalled tilts the lift vector sideways and increases the down-going wing's drag, giving the spin a stronger auto-rotative force. The result is a quicker, tighter spiral that turns a simple stall into a fully developed spin. Therefore, you keep ailerons neutral and let the rudder do the work. You select the opposite rudder, hold it, then ease the elevator forward until the stall breaks and rotation stops, all while you check the stick is neutral so the wing sees no extra aggravation.
