Accident Details
On April 24, 2008, at approximately 1030 mountain daylight time, a Cessna 180, registration N180XP, experienced a structural failure during the landing roll at Blanding Municipal Airport, Blanding, Utah. The airplane was operated by the private pilot-owner under 14 Code of Federal Regulations Part 91 as a personal pleasure flight. It had departed Eagle City, Utah, about 30 minutes prior and was operating in visual meteorological conditions. No flight plan was filed, and no ELT activation was reported.
Sequence of Events
According to the pilot, the touchdown for the planned full-stop landing was smooth and uneventful. However, near the beginning of the landing roll, the airplane began turning to the left. The pilot applied almost full right rudder, but the left turn continued. The pilot then began to apply right brake in addition to the rudder input. As braking pressure increased, the right main landing gear leg separated from the airframe at the point where it protrudes from the fuselage. The airplane subsequently slid off the runway onto the surrounding soft terrain.
Damage Assessment
The accident sequence resulted in substantial damage to the aircraft. The outboard portion of the right wing was bent upward, the fuselage skin around the landing gear attachment box was torn open, and the tail wheel pivot assembly casting broke in two. Except for the failure of the main landing gear leg and the tail wheel pivot assembly casting, no other airframe or flight control anomalies were found.
Materials Investigation
Both the fractured tail wheel pivot assembly casting and the portion of the right main landing gear leg that remained attached to the airframe were submitted to the NTSB Materials Laboratory for examination. The metallurgical features on the right main landing gear leg were consistent with separation due to a fatigue fracture that had initiated in a corrosion pit under a gear leg clamping mechanism. Additionally, three smaller fatigue regions were detected within the shear lip of the fracture. Examination of the tail wheel pivot casting revealed a uniformly grainy fracture surface, consistent with an overload event.