Incipient Spin Definition
The Incipient Spin is a term assigned to the transition phase during which a stall is propagating towards a developed spin. The recovery from an incipient spin prior to reaching one-turn is shown in the video below. This is for demonstration purposes only and should only be attempted in an aircraft certified for intentional spins.
Our goal as a pilot when faced with a stall, including slipping or skidding cross-controlled, and accelerated stalls, is to immediately and correctly apply the All-Attitude Upset Recovery Strategy (AAURS). The application of the AAURS is our first line of defense in recovering the aircraft to normal flight (i.e. Angle of Attack (AOA) less than Critical AOA).
Stall + Uncoordinated Flight
An airplane will only spin if both stall and yaw are present. If no yaw is present, then there will be no differential AOA between the two wings. With no difference in AOA between the wings, both wings produce equal lift, eliminating differential lift that causes autorotation. No autorotation, no spin. If the airplane is in coordinated flight, your only concern is the stall, which is eliminated by reducing AOA.
If the aircraft is uncoordinated at the stall and this yaw-roll couple / uncoordinated flight is allowed to develop while sustaining the stall, the aerodynamic forces on the aircraft will eventually drive the aircraft towards a different stabilized flight condition called The Spin. We need to stop the spin before it starts and the AAURS is how to do it. Although every stall does not result in a spin, it is important to recognize that every spin is always preceded by a stall. If we can “fix” the stall when it starts, we save ourselves the drama of having to deal with the spin. Note: Once in a fully developed spin, the aircraft will not respond favorably to the AAURS. When faced with a developed spin the pilot should immediately apply the NASA Standard Spin Recovery Technique (PARE) in the hopes of recovering from the spin, if recovery is possible.
When to Initiate a Spin Recovery vs a Stall Recovery
At what point do we make the decision to stop applying the stall recovery and revert to the spin recovery? That is an excellent question and the answer really depends upon the type, category and stall characteristics of the aircraft in question. For example, normal and utility single-engine certified aircraft must demonstrate recoverability from a one-turn spin (or a 3-second spin, whichever takes longer) in not more than one additional turn, but that’s it. After one-turn, there is no guarantee the aircraft is recoverable at all unless it is certified for spins. The vast majority of large multi-engine aircraft are not recoverable from the spin because the pro-spin inertial forces generated in the developed spin for these aircraft exceed the aircraft’s ability to generate sufficient anti-spin force (yaw authority) to “decouple” auto-rotation and return to normal flight. In these aircraft, it may be that the only option available is the early application of the AAURS and the only portion of the stall that offers a recovery option is during the initial stage, prior to development of rotation. The earlier the AAURS is correctly applied in the stall, the more likely the possibility of a recovery.
ALL-ATTITUDE UPSET RECOVERY STRATEGY
For further detail see Stall Recovery information and Templates found in AC 120-109A and AC 61-67C.
Here is an explanation of the factors that must be considered and managed in recovery from an incipient spin through the use of the AAURSTM.
PUSH: Reduce AOA (forward movement of the control column) to allow the wing to reduce AOA below critical AOA, reduce drag and to immediately transition from stalled flight to normal unstalled flight. Common tendencies are to either over-push causing excess nose drop below the horizon, increasing altitude loss, or a fore-aft pumping motion of the yoke causing one or more secondary stalls. While pushing, rudder use must also be simultaneously addressed. If there is any roll/yaw motion associated with the initial stall and the wing is still at or beyond critical AOA, the rudder should be used to stop the yaw-roll couple from developing. The amount of rudder used is only enough to coordinate the flight condition and should be accomplished in one application. Pumping or cycling the rudder is not a desirable technique especially for large transport category aircraft. Note that the rudder is not used to roll the aircraft wings-level in a stall recovery. Common errors in the use of rudder vary from not using it all to using it far too much, for too long. Rudder is critically important in an uncoordinated stall condition (such as a cross-controlled stall) to ensure the stall is not allowed to develop from a stall to an incipient spin.
ROLL: When the wings are clearly un-stalled and coordinated flight has been regained. The aircraft’s flight attitude must be immediately re-oriented to a wing’s level condition by rolling with aileron and coordinated rudder to the nearest horizon. Again, the aircraft should not be rolled by use of rudder alone at this stage. The primary roll control in normal (unstalled) flight is through the proper use of ailerons.
POWER: Smoothly add up to full power (dependent upon pitch attitude and acceleration) to increase airspeed and minimize altitude loss. We can do stall recoveries all day with the power at idle, however, an idle power setting is not assisting us in providing an adequate margin above the stall. Keep in mind that there are certain situations that selecting power to idle in the stall recovery is the proper action. Examples include high-torque single-engine prop aircraft and in a Vmc situation in a multi-engine aircraft.
STABILIZE: Once the other steps have been accomplished and an appropriate attitude has been established to let the plane accelerate / decelerate, with the wings level in coordinated flight, aft yoke movement should be applied to initiate recovery to a level or climbing attitude as required. The amount of elevator movement applied must ensure the aircraft remains below critical AOA (avoiding a secondary stall) at less than the limit load factor.
It is important for the pilot to know and understand that these processes can not be successfully reversed. The stall must be solved first, regardless of the flight attitude of the aircraft, then followed by solving the unusual attitude.
Please take a moment to have a look at the demonstration below to see how the AAURS effectively recovers the aircraft prior to completing one-turn of rotation from a cross-controlled slipping turn stall entry. This should only be attempted in an aircraft certified for intentional spins (such as an aircraft certified in the Aerobatic Category). Emphasis in all practical training should be for the stall recovery to be applied at the first indication of the stall in all aircraft. Please have a look at this demonstrated recovery.