NTSB Identification: BFO92FA152.
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Accident occurred Sunday, September 20, 1992 in WESTON, WV
Probable Cause Approval Date: 09/28/1993
Aircraft: MOONEY M20K, registration: N99693
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.
AFTER BEING ALERTED TO AN OIL STREAK ALONG THE SIDE OF THE AIRPLANE, THE PILOT CHECKED THE OIL AND THEN DEPARTED ON A NIGHT FLIGHT OVER HILLY TERRAIN. WHILE IN CRUISE FLIGHT, THE PILOT REPORTED 'MOTOR TROUBLES' TO APPROACH CONTROL AND RECEIVED VECTORS TO THE CLOSEST AIRPORT. THIS AIRPORT HAD NO RUNWAY LIGHTING. THE PILOT WAS ABLE TO MAINTAIN PARTIAL POWER FOR ABOUT 14 MINUTES. DURING THIS TIME, THE ATC CONTROLER WAS UNSUCCESSFUL IN ATTEMPTS TO TURN ON THE RUNWAY LIGHTS AT THE CLOSEST AIRPORT, AND WAS UNAWARE THE LIGHTS WERE OUT OF SERVICE. THE PILOT THEN REPORTED 'ITS DEAD' AS HE APPROACHED THE AIRPORT. HE WAS UNABLE TO LAND AT THE UNLIT AIRPORT, DESPITE GUIDANCE FROM ATC AND ANOTHER AIRPLANE WHICH WAS IN THE VICINITY. THE AIRPLANE IMPACTED TERRAIN AND WAS DESTROYED. AN EXAM OF THE ENGINE REVEALED THE NO. 1 CYLINDER HAD SEPARATED FROM THE ENGINE CRANKCASE IN FLIGHT. A METALLURGICAL EXAM REVEALED EVIDENCE OF FRETTING DAMAGE ON THE ATTACHMENT FLANGE AND FATIGUE FAILURE OF THE ATTACHING THROUGH BOLTS AND HOLD DOWN STUDS.
The National Transportation Safety Board determines the probable cause(s) of this accident to be: TOTAL LOSS OF ENGINE POWER DUE TO THE INADEQUATE TORQUE OF THE NO. 1 CYLINDER ATTACH BOLTS AND STUDS, FATIQUE FAILURE OF THE BOLTS/STUDS, AND SEPARATION OF THE NO. 1 CYLINDER. FACTORS RELATED TO THE ACCIDENT WERE: DARKNESS AND HILLY TERRAIN, WHICH WERE UNSUITABLE FOR A FORCED LANDING.
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