NTSB Identification: SEA00LA032.
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Accident occurred Wednesday, December 15, 1999 in HELENA, MT
Probable Cause Approval Date: 05/17/2001
Aircraft: Cessna 140, registration: N2739N
Injuries: 1 Uninjured.

NTSB investigators may not have traveled in support of this investigation and used data provided by various sources to prepare this aircraft accident report.

The pilot stated that on his second touch-and-go landing at the airstrip, about half way down the runway, the left wheel separated and the airplane nosed over. FAA inspectors observed that the left wheel and gear extension had separated from the left main landing gear leg and were found off the runway on the left side. Surface tracks indicated that the airplane had been tracking along the centerline of the runway, and that the airplane had continued to track down the centerline for an additional 30 yards before it nosed over. The four left main landing gear extension attachment bolts were inspected by the NTSB's material laboratory. Examination revealed that all four bolts were bent through the shank portion; however, none of the bolts were separated. Additionally, the threads in each bolt were scraped on the convex side of the bend, as if from sliding out of the bolt hole. Three of the four bolts exhibited what appeared to be stripped threads of their corresponding nuts in their thread grooves. No evidence was found of the presence of a nut on the fourth bolt. Records revealed that the airplane had received an annual inspection on November 11, 1999, and it had accumulated seven hours of operation since that inspection.

The National Transportation Safety Board determines the probable cause(s) of this accident to be:

Separation of the left main landing gear. Factors include inadequate preflight inspection by the pilot, and inadequate inspection at the time of annual inspection by maintenance personnel.

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