If recovery from a stall is not made properly, a secondary stall or a spin may result. A secondary stall is caused by attempting to hasten the completion of a stall recovery before the aircraft has regained sufficient flying speed. When this stall occurs, appropriate forward pressure or the relaxation of back elevator pressure should again be performed just as in a normal stall recovery. When sufficient airspeed has been regained, the aircraft can then be returned to straight and level flight.

A spin may be defined as an aggravated stall that results in what is termed “autorotation” wherein the airplane follows a downward corkscrew path. As the airplane rotates around a vertical axis, the rising wing is less stalled than the descending wing creating a rolling, yawing, and pitching motion. The airplane is basically being forced downward by gravity, rolling, yawing, and pitching in a spiral path.

Minor weight or balance changes can affect an aircraft’s spin characteristics. For example, the addition of a suitcase in the aft baggage compartment will affect the weight and balance of the aircraft. An aircraft that may be difficult to spin intentionally in the utility category (restricted aft CG and reduced weight) could have less resistance to spin entry in the normal category (less restricted aft CG and increased weight) due to its ability to generate a higher AOA and increased load factor. Furthermore, an aircraft that is approved for spins in the utility category, but loaded in the normal category, may not be recoverable from a spin that is allowed to progress beyond one turn or 3-second spin, whichever is longer (refer to 14 CFR part 23, § 23.221(a)).

The primary cause of an inadvertent spin is exceeding the critical AOA while applying excessive or insufficient rudder and, to a lesser extent, aileron. Insufficient or excessive control inputs to correct for Power Factor (PF), or asymmetric propeller loading, could aggravate the precipitation of a spin. At a high AOA the downward moving blade, which is normally on the right side of the propeller arc, has a higher AOA and therefore higher thrust than the upward moving blade on the left. This results in a tendency for the airplane to yaw around the vertical axis to the left. If insufficient or excessive rudder correction is applied to counteract PF, uncoordinated flight may result. A classic situation where PF could play an important role in a stall/spin accident is during a go-around or short field takeoff where the airplane is at a high pitch attitude, high power setting, and low airspeed. In an uncoordinated maneuver, the pitot/static instruments, especially the altimeter and airspeed indicator, are unreliable due to the uneven distribution of air pressure over the fuselage. The pilot may not be aware that a critical AOA is approaching until the stall warning device activates. If a stall recovery is not promptly initiated, the airplane is more likely to enter an inadvertent spin. For example, stall/spin accidents have occurred during a turn from base to final because the pilot attempted to rudder the airplane around (skid) so as not to overshoot the runway nor use excessive bank angle in the traffic pattern. The spin that occurs from cross controlling an aircraft usually results in rotation in the direction of the rudder being applied, regardless of which wingtip is raised. In a skidding turn, where both aileron and rudder are applied in the same direction, rotation will be in the direction the controls are applied. However, in a slipping turn, where opposite aileron is held against the rudder, the resultant spin will usually occur in the direction opposite the aileron that is being applied.

Before flying any aircraft in which spins are to be conducted, the pilot should be familiar with the operating characteristics and standard operating procedures, including spin recovery techniques, specified in the approved AFM or POH. The first step in recovering from an upright spin is to close the throttle completely to eliminate power and minimize the loss of altitude. If the particular aircraft spin recovery techniques are not known, the next step is to neutralize the ailerons, determine the direction of the turn, and apply full opposite rudder. When the rotation slows, briskly move the elevator control forward to approximately the neutral position. Some aircraft require merely a relaxation of back pressure; others require full forward elevator control pressure. Forward movement of the elevator control will decrease the AOA. Once the stall is broken, the spinning will stop. Neutralize the rudder when the spinning stops to avoid entering a spin in the opposite direction. When the rudder is neutralized, gradually apply enough aft elevator pressure to return to level flight. Too much or abrupt aft elevator pressure and/or application of rudder and ailerons during the recovery can result in a secondary stall and possibly another spin. If the spin is being performed in an airplane, the engine will sometimes stop developing power due to centrifugal force acting on the fuel in the airplane's tanks causing fuel interruption. It is, therefore, recommended to assume that power is not available when practicing spin recovery. As a rough estimate, an altitude loss of approximately 500 feet per each 3-second turn can be expected in most small aircraft in which spins are authorized. Greater losses can be expected at higher density altitudes.

The spiral mode is an autorotation mode similar to a spin. The center of rotation is close to the centerline of the airplane but the airplane is not stalled. Many airplanes and gliders will not spin at forward CG locations but will spiral. Many airplanes will enter a spin but the spin will become more vertical and degenerate into a spiral. It is important to note that when the spin transitions into the spiral the airspeed will increase as the nose goes down to near vertical. The side forces on the airplane build very rapidly and recovery must be effected immediately before exceeding the structural limits of the airplane. Release the back pressure on the stick (yoke), neutralize the rudder and recover from the steep dive. As in stall and spin recovery, avoid abrupt or excessive elevator inputs that could lead to a secondary stall.