Courting disaster by "demonstrating" Vmca
It is well known that requiring a student to fly a Vmca "demonstration" in a ME aircraft to prove some sort of competency is fraught with danger of mishandling and all the potential for a spin. Colleague described how he was instructing on a C310 where Vmca was being conducted by the student. You know the sort of thing - instructor demonstrates - student practices until certified competent.
A fraction of a second after the nose of the Cesnna 310 began to yaw after the limit of the rudder had been attained, the aircraft went into a vicious spin so quickly that the instructor was completely caught off guard.
After several turns in which considerable altitude was lost, standard recovery action finally took effect and the aircraft bottomed out 1400 ft above terrain leaving three very frightened occupants. However the box marked "VMCA tested" was ticked off of course.
My bet is that scenario has been repeated a thousand times in different light twins, yet from what I can judge the Vmca exercise is a mandatory part of initial multi-engine training. If a fully developed spin is considered an aerobatic manoeuvre and few light twins are certified for aerobatic flight, then surely any manoeuvre such as Vmca that risks an incipient and perhaps a dangerous full spin on a ME aircraft should not be part of a training syllabus.
After all, when flying on one engine in a ME aircraft the student can feel the amount of rudder needed to prevent yaw so why "practice bleeding" just to have the student see how close you can fly to Vmca before flicking inverted? Seems pretty lousy risk management to me.