On May 20, 1998, at 1715 hours Pacific daylight time, a Piper PA-44-180, N2153B, collapsed the main landing gear after landing at the Fresno, California, airport. The aircraft, operated by Mazzeis Flying Service under the provisions of 14 CFR Part 91, sustained substantial damage. The flight instructor and private pilot were not injured. Visual meteorological conditions existed for the local instructional flight and no flight plan was filed. The flight originated from the Fresno airport at 1700 the day of the accident. In the instructor pilot's written statement to the Safety Board he reported that the purpose of the flight was to practice maneuvers in the practice area, and takeoffs and landings at an alternate airport. After performing the maneuvers, they flew to Chandler airport to practice takeoffs and landings. The instructor stated that the first landing was conducted with both engines operating. On the second approach for landing, he simulated a single engine approach. He stated that the approach was high and the student performed a go-around. On the next landing, he again simulated a single engine approach with a successful full stop landing. The instructor stated that both landings were "good." The instructor reported that they returned to the Fresno airport to terminate the flight. In the pattern he simulated an engine failure, and the student recovered and continued the approach and subsequent landing. After touchdown the aircraft started to move right of centerline. The instructor reported that he applied full left rudder to counteract the movement to the right. He stated that he stopped the aircraft on the runway and informed the tower that he thought they had a flat tire and he would like to get out and check. The tower approved his request and the instructor exited the aircraft. The instructor reported that the right main landing gear was broken, and he requested that his student shut down the engines. When he attempted to reenter the aircraft, the right main landing gear collapsed and the right wing struck the ground. In the instructor pilot's interview with a Federal Aviation Administration (FAA) inspector, on May 21, 1998, he stated that he had simulated an engine failure on the approach to Fresno and during the landing had a "moderately hard landing." The FAA inspector received an amended written statement from the instructor with no mention of a hard landing. The same FAA inspector interviewed the student pilot on May 21, 1998. She stated that the landing at the Fresno airport was hard and she was not sure if the aircraft was aligned properly with the runway during the landing sequence. The FAA inspector requested a written statement from the student pilot. In her written statement she stated that the last landing was not hard and that the aircraft was aligned with the runway during the landing sequence. The FAA inspected the aircraft and landing gear mechanism at the accident location. The FAA noted that the right landing gear had separated from the wing and that the front and rear attach fittings on the landing gear were broken exhibiting outboard stress. The FAA inspector reported that the landing gear collapsed towards the fuselage with rub marks located on the inboard portion of the tire. No further mechanical anomalies were noted.