KING SALMON, AK, USA
N177BM
Cessna 185F
The commercial certificated pilot was back-taxiing on a runway in preparation for takeoff, and then began a 180 degree turn on the runway. During the turn, the pilot said he heard a scraping sound, the airplane wobbled and shimmied, and the right brake was not functioning. The right main landing gear strut collapsed near the axle attach point, and the right main wheel and tire rolled away from the airplane. The right wingtip and the propeller struck the ground, and the right gear strut was torn loose from its upper attach point. A postexamination of the right wheel and strut by the owner revealed the axle assembly separated from the lower end of the landing gear strut. There are four hex head bolts utilized to secure the axle to the landing gear strut. Each are inserted through the axle assembly and gear leg, and have a nut threaded and then torqued onto the bolt shaft. All four of the bolts were bent. Two of the nuts were stripped off their respective bolt shafts. The remaining two bolts were broken about mid-shaft. The owner of the airplane reported that about five days before the accident, new brake assemblies were installed on the airplane. The original bolts were re-used for the installation. One of the broken bolts was submitted to the National Transportations Safety Board's Materials Laboratory for examination. According to an NTSB materials engineer, the bolt was bent about 35 degrees, it had necking deformation adjacent to the fracture, and displayed features consistent with an overstress fracture in bending.
On September 2, 2001, about 1430 Alaska daylight time, a tundra tire-equipped Cessna 185F airplane, N177BM, sustained substantial damage while taxiing for takeoff at the King Salmon Airport, King Salmon, Alaska. The airplane was being operated as a visual flight rules (VFR) cross-country personal flight under Title 14, CFR Part 91, when the accident occurred. The airplane was operated by Bill Martin, Fish Alaska Inc., King Salmon. The commercial certificated pilot, and the sole passenger, were not injured. Visual meteorological conditions prevailed. VFR company flight following procedures were in effect. During a telephone conversation with the National Transportation Safety Board (NTSB) investigator-in-charge (IIC), on September 7th, the pilot reported that he was preparing to depart and was back-taxiing on runway 11 at King Salmon. He then began a 180 degree turn to depart on runway 29. During the turn, the pilot said he heard a scraping sound, the airplane wobbled and shimmied, and the right brake was not functioning. The right main landing gear strut collapsed near the axle attach point, and the right main wheel and tire rolled away from the airplane. The right wingtip and the propeller struck the ground, and the right gear strut was torn loose from its upper attach point. A postexamination of the right wheel and strut by the owner revealed the axle assembly separated from the lower end of the landing gear strut. There are four hex head bolts utilized to secure the axle to the landing gear strut. Each are inserted through the axle assembly and gear leg, and have a nut threaded and then torqued onto the bolt shaft. All four of the bolts were bent. Two of the nuts were stripped off their respective bolt shafts. The remaining two bolts were broken about mid-shaft. The owner of the airplane reported that about five days before the accident, new brake assemblies were installed on the airplane. The original bolts were re-used for the installation. One of the broken bolts was submitted to the National Transportations Safety Board's Materials Laboratory for examination. According to an NTSB materials engineer, the bolt was bent about 35 degrees, it had necking deformation adjacent to the fracture, and displayed features consistent with an overstress fracture in bending.
An overload failure of the main axle attaching bolts, and subsequent separation of the axle from the landing gear strut.
Source: NTSB Aviation Accident Database
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