NTSB Identification: LAX06FA129.
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Accident occurred Monday, March 13, 2006 in Santa Monica, CA
Probable Cause Approval Date: 03/26/2007
Aircraft: Beech A36, registration: N16JR
Injuries: 2 Fatal.
NTSB investigators either traveled in support of this investigation or conducted a significant amount of investigative work without any travel, and used data obtained from various sources to prepare this aircraft accident report.
The engine lost power during the takeoff-initial climb and the pilot ditched the airplane in the ocean. Examination showed that the number 2 connecting rod fractured from the crankshaft. Metallurgical examination of the connecting rod, and associated bolts, nuts, and bearings, showed that following the first nut and bolt separation, the overall separation was not instantaneous. After the first nut unthreaded from its respective bolt, subsequent increased loads on the opposite bolt then stripped the threads of the other nut that had partially unthreaded from its bolt. Furthermore, there was no evidence of cotter pin installation. In general, a properly torqued nut and connecting rod bolt will not loosen under normal operational conditions. The engine underwent a field overhaul 735.31 hours prior to the accident. At 233.59 hours prior to the accident, the cylinders were removed for a blow by condition during an annual inspection; however, the aviation maintenance technician who performed this work stated that he did not remove the connecting rods from the crankshaft. Review of the autopsy results and impact damage to the wreckage indicated that the occupants' use of shoulder harnesses would have significantly increased their chances of survival.
The National Transportation Safety Board determines the probable cause(s) of this accident to be: The failure of an aviation maintenance technician to properly torque and cotter pin the number 2 connecting rod bolts at their attach point to the crankshaft, which resulted in the separation of the connecting rod in flight, and complete power loss. Full narrative available
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