LOSS OF AIRCRAFT CONTROL DURING A GO-AROUND, DUE TO FAILURE OF THE FLIGHT INSTRUCTOR (CFI) TO ASSURE THAT THE MINIMUM CONTROL SPEED (VMC) WAS MAINTAINED. FACTORS RELATING TO THE ACCIDENT WERE: SHUTDOWN OF THE LEFT ENGINE, WHICH WOULD HAVE PREVENTED NORMAL GEAR EXTENSION, AND POSSIBLE HABIT INTERFERENCE BY THE CFI (DUE TO THE NUMBER OF AIRCRAFT THAT HE HAD RECENTLY FLOWN).