WPR25LA102

During the takeoff roll for a simulated short-field takeoff, the right main landing gear wheel did not immediately rotate, and the right main landing gear leg subsequently collapsed. Postaccident examination found that the right main landing gear tubular spring had separated near its inboard end, with the tip of the fracture about 4 inches outboard of the airframe connecting bolt hole. Further examination revealed a spiraling crack that traveled inboard from the tip of the teardrop-shaped fracture surface to the connecting bolt hole and extended through the wall thickness at the bolt hole. Multiple areas of fatigue were identified on the fracture surface of the smaller inboard piece. The fatigue emanated from the outer diameter corner of the connecting bolt hole and was consistent with fatigue occurring over a long period of time. Some features on the fracture surface were consistent with fast fracture due to overstress, and galling was observed in rub damage consistent with metal-to-metal contact during movement between the hole surface and the outer diameter of the mating connecting pin. The spiraling crack was visible when viewing the tubular spring through the cabin floor inspection hole positioned directly above the fracture. Although the crack was possibly present but went unobserved during previous 100-hr or annual inspections, the investigation was unable to identify when the cracking in the visible area began.

Review of maintenance records showed that an annual inspection was completed on March 11, 2024. The most recent recorded maintenance was a 100-hour inspection, which was completed on November 7, 2024. On February 23, 2025, about 1500 Pacific standard time, a Cessna 172S airplane, N137RJ, was substantially damaged when its right main landing gear collapsed during a takeoff attempt in La Verne, California. The flight instructor and student pilot were not injured. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 instructional flight. According to the flight instructor, he and a student pilot were conducting a simulated short-field takeoff. They taxied the airplane into position on the runway and stopped. The student pilot held the brakes while increasing engine power and released them after about three seconds. As the brakes were released to begin the takeoff roll, the left main landing gear wheel rolled, but the right main landing gear wheel did not immediately roll. About one second later, the right main landing gear leg collapsed and the right wingtip and right elevator contacted the runway. Postaccident examination of the airplane found that the right wing, horizontal stabilizer, and elevator sustained substantial damage, and the right main landing gear tubular spring was separated near the inboard end, with the tip of the fracture about 4 inches outboard of the connecting bolt hole (see figure). Examination of the right main landing gear tubular spring by the NTSB Materials Laboratory revealed a spiraling crack that traveled inboard from the tip of the teardrop-shaped fracture surface to the connecting bolt hole. The crack extended through the wall thickness at the bolt hole. Multiple areas of fatigue were identified on the fracture surface of the smaller inboard piece. The fatigue emanated from the outer diameter corner of the connecting bolt hole and was consistent with fatigue occurring over a long period of time. Features on the fracture surface beyond the flat area were consistent with fast fracture due to overstress. Rub damage was observed on the bolt hole surface adjacent to the fracture surface. Evidence of galling was observed in the rub damage consistent with metal-to-metal contact during movement between the hole surface and the outer diameter of the mating connecting pin. Figure. View of the inboard segment of the separated tubular gear spring prior to removal from the airframe. The fracture and spiraling crack in the spring can be seen through the floor inspection hole.