NTSB Identification: SEA98LA133.
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Accident occurred Sunday, July 12, 1998 in OAKVILLE, WA
Probable Cause Approval Date: 01/11/2000
Aircraft: Beech 23, registration: N8719M
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.
The engine began vibrating violently and losing power without warning while in cruise flight. Unable to maintain altitude, The pilot-in-command executed a forced landing in a soft, open field. During the roll-out, the nose landing gear separated and the left main landing gear collapsed. Post-crash engine examination revealed that the 7/16' exhaust valve on the number 3 cylinder had failed. Reconstructed log books (engine) noted that previous log books had been lost, and that the engine had been overhauled in 1966, about 978 hours before the accident. The Airworthiness Directives (AD) listing in the reconstructed log books for the engine noted that an AD requiring recurrent inspection and replacement of 7/16' valves and/or valve guides (depending upon which camshaft was installed) did not apply due to the serial number of the engine. The associated service bulletin did, however, list the serial number of the engine as requiring compliance. No record of compliance with this AD note prior to the reconstruction of the log books was found, and no record was found as to which camshaft was installed at the time of the reported overhaul.
The National Transportation Safety Board determines the probable cause(s) of this accident to be: Loss of power due to the failure of an exhaust valve, and overloading of the landing gear. Factors include the failure of maintenance personnel to verify proper compliance with an Airworthiness Directive related to the exhaust valve, and soft terrain. Full narrative available
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