NTSB Identification: NYC98LA074.
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Accident occurred Thursday, March 05, 1998 in LYNCHBURGH, VA
Probable Cause Approval Date: 06/21/2000
Aircraft: Beech A36, registration: N1559X
Injuries: 3 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.
Shortly after takeoff, the pilot heard a loud bang, felt a thump, and saw the engine cowling deflect upward. He reduced engine power, and turned towards the departure airport. After a second loud bang, followed by severe vibration the pilot shut down the engine, and performed a forced landing to a field. Examination of the wreckage revealed two holes in the top of the engine crank case which were over 8 inches in diameter. One of the engine's number six cylinder connecting rod bolts showed signs of a catastrophic failure, the other number six connecting rod bolt was intact and did not contain a nut. Examination of the number six connecting rod, and connecting rod bolts revealed severe mechanical impact damage to the threads of the intact bolt. The broken bolt had three different fracture features. One was consistent with failure in shear, a second was consistent with a tensile overstress separation, and the majority of the third had a rubbed appearance. The connecting rod bolts and nuts had been replaced 375 hours before the accident flight. The last annual inspection of the airplane was performed about 16 months prior to the accident.
The National Transportation Safety Board determines the probable cause(s) of this accident to be: Failure of the number six connecting rod bolt due to improper maintenance. Full narrative available
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