LAKE HUGHES, CA, USA
N9YT
CESSNA T210N
THE AIRPLANE WAS ON A U.S. NAVY MISSION AND FLOWN BY A NAVY AVIATOR; ANOTHER NAVY AVIATOR OCCUPIED THE RIGHT FRONT SEAT. WHILE OVER MOUNTAINOUS TERRAIN THE ENGINE SUSTAINED A CATASPHROPHIC CRANKSHAFT FAILURE. THE PILOT ELECTED TO PROCEED TOWARDS HIGHER TERRAIN BYPASSING LOWER AND MORE SUITIBLE EMERGENCY LANDING AREAS. INTERNAL COMMUNICATIONS BETWEEN THE RIGHT SEAT OCCUPANT, A MORE EXPERIENCED PILOT, AND THE PIC INDICATED THEY PLANNED TO STALL THE AIRPLANE PRIOR TO LANDING ON AN UPWARD SLOPING MOUNTAIN RIDGE. THE PILOT MISJUDGED THE ALTITUDE AND STALLED THE AIRPLANE. BOTH PILOTS WERE KILLED. THE INVESTIGATION REVEALED THAT THE CRANKSHAFT FAILED DUE TO INADEQUATE TORQUE OF THE THROUGH BOLTS CAUSING FRETTING AND GALLING ON THE CRANKCASE HALVES. THE ENGINE HAD ACCURED 618 HOURS SINCE MAJOR OVERHAUL AND HAD EXPERIENCED 7 VACCUM PUMP FAILURES DUE TO MISALIGNMENT OF THE CRANKSHAFT DRIVE GEAR. THE THROUGH BOLTS WERE REMOVED BY THE OPERATOR TO REPAIR THE NO. 3 ROSAN STUD 322 HOURS BEFORE THE CRANKSHAFT FAILED.
POOR MAINTENANCE REPAIR AND ANNUAL INSPECTION BY THE COMPANY'S MAINTENANCE PERSONNEL AND THE PILOT-IN-COMMAND'S MISJUDGING ALTITUDE. CONTRIBUTING TO THIS ACCIDENT WAS THE PILOT-IN-COMMAND INTENTIONAL STALL, IMPROPER EMERGENCY PROCEDURE, SELECTION OF UNSUITABLE TERRAIN FOR THE FORCED LANDING AND THE MOUNTAINOUS TERRAIN.
Source: NTSB Aviation Accident Database
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