On April 18, 2002, at 1910 Pacific daylight time, a Beech 76, N6636J, collided with the ground and collapsed the landing gear during a practice single engine go-around at the Petaluma, California, airport. The airplane was operated by Sierra Academy of Aeronautics under the provisions of 14 CFR Part 91 of the Federal Aviation Regulations, and was on a local area instructional flight. The airplane sustained substantial damage. The commercial pilot flight instructor, the commercial licensed multiengine student, and one additional passenger were not injured. Visual meteorological conditions prevailed. No flight plan was filed for the flight, which originated at the Oakland International Airport, Oakland, California, at 1840. The flight instructor was interviewed by telephone concerning the accident on April 19, 2002. He stated that he was the flight instructor on board the aircraft at the time of the accident. The flight departed the Oakland airport at 1840 for a local area training flight with a multiengine student in the left seat and one additional student in the rear observing. The left seated student held a commercial certificate with ratings for single engine airplanes and instruments and was in a course to qualify for a multiengine add-on rating. After performing some airwork, the instructor had the student do a practice single engine VOR approach to the Petaluma airport in VFR conditions. The right engine was set to zero thrust for the procedure and the winds were straight down runway 29. They overflew the runway during the approach and circled to enter right traffic. During the approach he had decided to have the student do a single engine go-around. He stated that in hindsight he issued the go-around command at too low an altitude. The airspeed was above Vmc during the go-around; however, due to the low altitude at maneuver initiation, the airplane inadvertently touched down with full power on the left engine, causing the airplane to begin veering to the right. It became airborne again in a nose high, yawing, and right rolling attitude. At this point, he assumed the controls and reduced the power on the left engine. The airplane then settled to the ground in the nose high, yawed, and banked attitude with the right main gear off the pavement. The right main gear and nose gear collapsed. The instructor said that after thinking about the event, he believes that neither he nor the student were making aggressive enough control inputs to correct the situation in the early stages, and he may have waited too long before assuming control. He stated that there were no mechanical malfunctions or system failures with the airplane.