Primary finding
Probable cause
The failure of the landing gear leg due to a fatigue fracture caused by corrosion.
Investigator assessment
Analysis narrative
The pilot-in-command stated he experienced a moderately hard landing and the right main wheel separated from the landing gear at the upper bolt holes which normally secure the axle to the landing gear leg. Metallurgical examination of the gear leg showed that the failure stemmed from area of fatigue cracking that initiated from crossion pitting in the bolt holes and exterior surfaces of the lower portion of the gear leg.
Source record
Factual narrative
On May 28, 1993, at 1715 Alaska daylight time, a wheel equipped Cessna 185 airplane, N80124, registered to and operated by the Pilot-in-Command, experienced a hard landing and subsequant landing gear failure at Sigley's private Airstrip located near Bulchitna Lake, Alaska. The business flight, operating under 14 CFR Part 91, last departed Kenai, Alaska, and the destination was the accident site. Visual meteorological conditions prevailed and no flight plan was filed. The airplane was substantially damaged and the Commercially Certificated Pilot-in-Command and the two passengers were not injured. According to the Pilot-in-Command, he experienced a moderate hard landing and the right main gear broke away at the wheel axle upper bolt holes. The airplane settled onto the remaining gear leg, veered right, and nosed over. Metallurigical examination of the fractured gear leg showed that the separation of the landing gear leg stemmed from areas of fatigue cracking that initiated from corrosion pitting in the bolt holes and exterior surfaces of the lower portion of the leg. Further, the metallurgist stated that the gear leg was composed of high strength steel, a material that is susceptible to fracture in the presence of relatively small defects. -