On October 3, 2001, at about 1145 central daylight time, a Piper PA-30B-160, N8402Y, registered to Aviation Training Services, Inc., operating as a Title 14 CFR Part 91 personal flight, crashed in the vicinity of Clarksville, Tennessee. Visual meteorological conditions prevailed, and no flight plan was filed. The aircraft received substantial damage, the commercially-rated pilot-in-command was not injured, and the CFI-rated second-in-command/aircraft owner received minor injuries. The flight departed Clarksville's Outlaw Field about 45 minutes before the accident. According to the left seat occupant and prospective buyer, the flight was conducted for the dual purposes of, (1) aircraft check-out for the prospective buyer, and (2) pre-purchase check-out of the aircraft. Following about 50 minutes of air work in the local practice area, they returned to the field for practice landings. After two full-stop landings by the prospective buyer, he asked the right seat occupant/seller/CFI how the aircraft handled with an engine failed. At 500 feet agl, on the third takeoff, the seller retarded the left throttle to idle and instructed the prospective buyer to fly the landing pattern and land in that configuration. At 20 feet agl, during the simulated engine failed landing, the seller said, "let's go around", and advanced both throttles. The aircraft quickly yawed and rolled left, and assumed a vertical, (estimated 80 degrees) nose down attitude, hit the ground in that attitude, cart wheeled at least once, and came to rest upright. As to who was pilot-in-command during the loss of control of the aircraft, the left seat occupant stated, "Since the aircraft had become the instructor's plane on the go-around initiation, I stopped myself from pulling the throttles back on top of his left hand since I figured he was much more capable to handle the engine-out than I was and I respected his ability. He is a good pilot and had recently given me a biennial flight review and IFR proficiency check ride." Additionally, he stated, "My conclusion is that we were below Vmc and that the only possible recovery was to retard the good engine and try to touch down in a straight and level attitude. In 3 seconds, we didn't have the time nor the altitude to recover otherwise." According to the right seat occupant/CFI/seller, "On the third takeoff a simulated engine failure was conducted. The approach was correct, and approx. 10-15' above the runway I decided to abort the landing. I instructed the student to perform a go around. He applied power to both engines by advancing both throttles to full power. The left engine failed to respond, and the airplane yawed to the left. This caused the left wing to drop and made contact with the runway. The aircraft then cart wheeled to the left making contact with the ground with nose. This motion continued to the left until the other side also made ground contact." On November 28, 2001, during a follow-up telephone call to the NTSB, the CFI/seller stated that he thought the probable cause of the left engine hesitation was the throttle being advanced "too quick" from its pulled back/idle position following the simulated engine out pattern and approach. He stated that although the two pilot's statements contradicted who actually pushed the throttles up for the go around, he, as CFI, was considered the pilot in charge. The record of telephone call is an attachment to this report. According to an FAA inspector, on a two engine go-around following a simulated failed left engine approach, the left engine failed to respond to power application as quickly as the right engine, resulting in an immediate left yaw and roll, a dragged wing tip, and a cartwheel. Both wing tips were bent rearward, and both engines were torn from their respective mounts. Postcrash inspection of both engines revealed no discrepancies with their respective magnetos and fuel servos.