ANC98IA096

The certificated commercial pilot was landing on runway 21, a paved runway, in a tailwheel equipped airplane. The pilot stated that after rollout she made a left turn to exit the runway, and the right main landing gear leg separated at the wheel attachment bolt holes. The right wing struck the ground and sustained minor damage. Metallurgical examination of the failed gear leg revealed multiple fatigue cracks originating from various corrosion pits located within the bolt holes. The operator noted that the airplane had been involved in a previous ground loop accident, and that the airplane had been used extensively for off airport landings utilizing wheel/skis. The failed gear leg had been inspected using a dye-penetrant process about 300 flight hours prior to the gear leg failure. Presently, there are no Cessna or FAA specified inspection intervals for this component. Landing gear legs are replaced 'on condition.'

On July 5, 1998, about 1400 Alaska daylight time, a wheel equipped Cessna 185 airplane, N3347L, sustained minor damage while taxiing at the Homer Airport, Homer, Alaska. The airplane was being operated as a visual flight rules (VFR) on-demand passenger flight under Title 14, CFR Part 135, when the incident occurred. The certificated commercial pilot, and the two passengers aboard were not injured. Visual meteorological conditions prevailed, and VFR company flight following procedures were in effect. The flight originated at the Seldovia Airport, Seldovia, Alaska, about 1345.

During a telephone conversation with the National Transportation Safety Board investigator-in-charge on July 5, the pilot reported that she had just landed on runway 21. She stated that after rollout she made a left turn to exit the runway, and the right main landing gear leg broke. The right wing struck the ground and sustained minor damage.

A metallurgical inspection of the lower portion of the broken gear leg was conducted at the NTSB laboratory, and revealed fatigue crack origin sites within the upper attaching bolt hole walls. A scanning electron microscope (SEM) examination revealed fatigue cracks initiating from multiple corrosion pits located within the bolt hole walls. Hardness tests performed on the numbered face of the landing gear leg ranged from 42.3 to 51.2 HRC, with an average of 47 HRC. The specified HRC range is 48.3 to 50.0 HRC.

The operator reported that on August 29, 1992, the incident airplane had been involved in a ground loop accident. The airplane sustained substantial damage, and was rebuilt over the next 6 years. The operator noted that while the airplane was undergoing repairs, both gear legs were removed and dye-penetrant inspections were performed. No anomalies were detected, and the gear legs were reinstalled, and placed back in service. She said that the broken gear leg had accumulated about 300 hours in service since the 1992 accident, and subsequent dye-penetrant inspection.

She added that prior to the 1992 ground loop accident, the airplane had been involved in extensive wheel/ski operations.

At the present time, Cessna maintenance procedures do not have required inspections intervals or life limits on landing gear legs. Cessna 185 landing gear legs are considered "on condition" items.