Alan Cassidy in his excellent book Better Aerobatics dedicates a section in the chapter on competition spins on managing the threat of a changeover spin. This chapter and section merit careful reading until it is properly understood. The following is a very condensed summary.
Using a Lycoming powered aerobatic aircraft and spinning to the left, a one turn spin, because of the relative wind and the spin being only one turn, will leave the aircraft in a relatively shallow down line when the spin stops. Competition aerobatics end spins in a vertical down line. This creates a conditioning to move the control column quite far forward to overcome the shallow attitude and achieve a vertical down line.
Now let’s take a one and a half turn competition spin. On recovery the relative wind (you commence competition spins into wind) is pushing the tail into a steeper attitude, and the spin being more than one turn also results in the aircraft having a stepper down line.
Because of conditioning, and also some general misapprehension that a universal spin recovery involves full forward stick, the pilot pushes the control column past the vertical and in a short coupled aerobatic aircraft with strong pitch controls this may set up a dynamic inverted stall.
The aircraft entered a left turning spin in addition to left yaw will have a left rolling motion. The pilot used full opposite rudder (right) in recovery but because she or he pushed past vertical into a dynamic inverted stall, the aircraft enters an inverted or changeover spin (upright to inverted). The original left rolling tendency continues and unless you understand what has happened and look through the cabane struts to appreciate what is happening, your full right rudder has placed you in a right yaw inverted spin with a left rolling motion. If your conditioning is to continue to push the control column forward this will increase the violence of the spin. You took the correct anti spin actions but the spin has accelerated!
To recover apply full opposite rudder, i.e. re apply left rudder, and relax your white knuckle death grip on the control column by bringing it back to neutral. Inverted there is no rudder blanking (assuming you are not in a T-tail!), and re applying the left rudder and stopping the negative alpha of full forward stick will cause a quick recovery. Applying full power will also increase the effectiveness of the pitch and rudder controls, with some torque to assist in correcting for right inverted yaw.
As you might imagine, without understanding the threat of a changeover spin entering one ignorant of the dynamic is highly stressful.
An important supplement is the Law of conservation of angular momentum. In effect this causes the spin forces to accelerate as the aircraft moves closer to a vertical down line.
Understanding well what happens when jamming the control column forward in the belief of a universal panacea against spins reminds me of Bertrand Russell’s essay on universals.
“The man who has fed the chicken every day throughout its life at last wrings its neck instead, showing that more refined views as to the uniformity of nature would have been useful to the chicken.”
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