CEN10LA207

The certificated flight instructor and student pilot planned on performing a full-stop landing on the runway. After making a normal touchdown, and as the airplane slowed down, the right-main gear collapsed. The right wing impacted the runway and the light-sport airplane sustained structural damage. A postaccident inspection of the airplane revealed that the three bolts attaching the right-main landing gear had failed. The bolts were sent to the Safety Board Materials Laboratory for examination. The examination noted that the two outboard bolts both had crack arrest markings, consistent with fatigue cracking from multiple origins. The third bolt (inboard) had signatures of necking and bending of the grip diameter and fracture characteristics consistent with an overstress separation. Prior to the accident, the airplane manufacturer had issued two service bulletins to address concerns with the proper torque on the landing gear bolts and replacement of the bolts. A review of the accident airplane maintenance records showed that the proper torque inspection service bulletin had been complied with; however, the replacement of the landing gear bolts with stronger bolts (service bulletin) was not applicable to this light-sport airplane.

On March 7, 2010, about 1400 Central Standard Time, a Tecnam P92, Light Sport airplane, N323BR, sustained substantial damage when the landing gear collapsed after landing at the RWJ Airpark (54T), Baytown, Texas. The airplane was registered to 323 BR, Inc. and operated by the Flying Tigers Flight School. The flight instructor and student pilot were not injured. Visual meteorological conditions prevailed, and the flight departed Ellington Field (EFD), Houston, Texas, about 1230. The flight instructor reported that they were doing a full stop landing on runway 08 at 54T. He added that it was a smooth landing and as the airplane was slowing down the right-main gear collapsed. The right wing impacted the runway. After turning off the engine, fuel, and (electrical) master switch, the student pilot and flight instructor exited the airplane. An on-site inspection of the airplane revealed that the 3 bolts holding the right-main landing gear, had failed. The bolts were sent to the Safety Board Materials Laboratory in Washington, D.C., for examination. The Materials Laboratory Factual Report noted that the two outboard bolts both had “crack arrest markings, consistent with fatigue cracking from multiple origins”. The third bolt (inboard), had “necking and bending of the grip diameter …. and fracture characteristics consistent with an overstress separation.” The bolts submitted to the lab appeared to be UNI 5737 bolts. Tecnam Service Bulletin, P92/001, issued August 7, 2007, required an inspection of the landing gear bolts (within 10 hrs), for proper torque. If the bolts required replacement, the service bulletin listed bolts conforming to MS specifications instead of the UNI specifications. Tecnam also issued service bulletin, SB 004-CS, that recommended owners replace the original bolts with the MS bolts; however, the bulletin was not mandatory, nor did it apply to N323BR due to serial number.