On April 5, 1994, about 1000 eastern daylight time, N187ER, a Mooney M20-J, registered to Embry Riddle Aeronautical University, experienced a gear collapse on landing at Daytona Regional Airport, Daytona Beach, Florida, while on a 14 CFR Part 141 instructional flight. Visual meteorological conditions prevailed at the time and a local company VFR flight following flight plan was filed. The airplane was substantially damaged and both pilots reported no injuries. The flight had originated about 90 minutes earlier. Both pilots stated that after executing a VOR approach they elected to terminate the flight with a short field landing on runway 16. The instructor pilot and the commercial rated student pilot both stated that they lowered the landing gear and confirmed it was down three times. During landing roll the left gear collapsed and the airplane then skidded off the runway and the other landing gears collapsed. Three pilot-rated witnesses stated that they observed the left landing gear not fully down before to landing. The instructor and student both stated that they did not hear the landing gear safety horn during approach. The airplane had been grounded the previous flight because of a faulty landing gear indication, and had a new gear limit switch installed along with a rigging check. After the accident the airplane was placed on jacks, the actuator rods were straightened, and the gear functioned normally; both electrically and manually.