SEA08LA110

During the landing roll, the pilot began to apply right rudder and right brake in order to compensate for the airplane turning to the left. During that sequence, the right main landing gear leg separated from the airframe at the point where it protrudes from the fuselage. The airplane then slid off the runway onto the surrounding soft terrain. An inspection of the gear leg by the NTSB Materials Laboratory determined that the metallurgical features discovered 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. In addition to the fatigue region at the origin area, three smaller fatigue regions were detected within the shear lip of the fracture.

On April 24, 2008, about 1030 mountain daylight time, a Cessna 180, N180XP, experienced the collapse of the right main landing gear strut during the landing roll at Blanding Municipal Airport, Blanding, Utah. The private pilot and his passenger were not injured, but the airplane, which is owned and operated by the pilot, sustained substantial damage. The 14 Code of Federal Regulations (CFR) Part 91 personal pleasure flight, which departed Eagle City, Utah, about 30 minutes prior to the accident, was being operated in visual meteorological conditions. No flight plan had been filed. There was no report of an ELT activation.

According to the pilot, the touchdown for the planned full-stop landing was smooth and uneventful, but near the beginning of the landing roll the airplane started turning to the left. He therefore applied almost full right rudder, but that did not stop the left turn. The pilot then began to apply right brake in addition to the rudder input. As the pilot increased the breaking pressure, the right main gear leg separated from the airframe at the point where it protrudes from the fuselage. The airplane then slid off the runway onto the surrounding soft terrain. As a result of the accident sequence, the outboard portion of the airplane's right wing was bent upward, the fuselage skin around the landing gear attachment box was torn open, and the tail wheel pivot assembly casting had broken in two. Except for the failure of the main landing gear leg and the tail wheel pivot assembly casting, there was no evidence of any other airframe of flight control anomaly.

Both the fractured tail wheel pivot assembly casting, and the portion of the right main landing gear leg that had remained attached to the airframe were submitted to the NTSB Materials Laboratory for further inspection. According to that inspection, the metallurgical features discovered 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. In addition to the fatigue region at the origin area, three smaller fatigue regions were detected within the shear lip of the fracture.

The inspection of the tail wheel pivot casting determined that its fracture surface contained a uniformly grainy surface consistent with an overload event.