Cessna 172RG N5095V accident near Kissimmee, Florida

Probable cause

A fatigue failure of the right main landing gear pivot assembly, which prevented the landing gear from extending.

NTSB analysis

The pilot was not able to obtain a positive gear down-and-locked indication and noticed that the right main landing gear (MLG) only extended about halfway down. After unsuccessful troubleshooting efforts, he performed an emergency gear-up landing, which resulted in substantial damage to the underside of the fuselage. Examination of the landing gear system revealed that the stub shaft of the right MLG pivot assembly was fractured and exhibited characteristics consistent with a torsional fatigue fracture containing multiple origins. Before the accident flight, a company mechanic observed some hydraulic fluid on the MLG leg and assumed that there was a leak from the pivot gear O-rings, which he replaced.

The Federal Aviation Administration previously issued an airworthiness directive (AD), which included an inspection of MLG pivot assemblies for cracks, in accordance with a manufacturer's service bulletin. The AD did not call for repetitive inspections. At the time of the accident, the airplane had been operated for about 7,755 total hours and about 1,800 hours since the time of AD compliance. The airplane service manual contained a supplemental inspection that included initial visual and eddy current inspections of the MLG pivot assembly for cracks in the spline area at 3,000 hours in service with repeated inspections every 500 hours thereafter. The visual and eddy current inspections had not been nor were they required to be performed on the accident airplane.

Text from the NTSB. Open the NTSB docket for ERA12LA070 for the full record.