Centaurus,
I have never seen rapid throttle movement defined. Certainly most operators of big pistons would consider three or four seconds excessively fast and constituting abuse of the engine! Normally the throttles are ‘walked’ up and down the quadrant by side-to-side wrist movement.
Power was always reduced gradually. From cruise at 31 inches to descent at 25 inches took several minutes of throttle walking. The next reduction was to 21 inches at 5 miles and 18-21 on base to 50 ft. When landing was assured further reduction occurred during the round-out and landing roll. The technique was not only to prevent detuning of the engine but also to avoid shock cooling.
For some handling insights on these engines try this thread: http://www.pprune.org/forums/showthread.php?s=&threadid=53550&highlight=GTSIO
Any mishandling of such engines will reduce engine life in a cumulative form, some actions more so than others. Sure I can’t unequivocally pin the failure in my instance back to the previous IRT but the consensus of opinion at the time was that the technique might not have helped. The metallurgy report found fatigue cracks in the gudgeon pin but obviously could not pinpoint the events that caused such cracks.
In arguing for throttle over mixture with such engines I think that courts would be swayed by the documentation at hand and the accepted code of practice implemented by the majority of operators. Try convincing counsel for the plaintiff that ‘on the balance of probabilities’ such a technique would not compromise ones duty of care particularly in the light of a mandatory SB to the contrary. Try arguing what constitutes rapid throttle movement when most operators think as in the thread above.