NTSB Identification: DEN02LA028.
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Accident occurred Sunday, February 24, 2002 in Ferron, UT
Probable Cause Approval Date: 01/16/2003
Aircraft: Piper PA-32R-300, registration: N47465
Injuries: 4 Minor.
NTSB investigators may not have traveled in support of this investigation and used data provided by various sources to prepare this aircraft accident report.
Approximately 30 minutes into the flight, the engine began to "miss, backfire heavily and sputter." The number 1 cylinder temperature "shot off the gauge" with a red light warning light illuminated. The engine lost power and the airplane began to descend. The pilot made a forced landing on a highway. During the landing roll, the airplane struck a truck parked on the shoulder, shearing off its left wing. The airplane then overturned and skidded 300 feet to a halt. Engine disassembly revealed the magneto idler gear that drives the dual magneto was missing 8 teeth. Three of the teeth were displaced from the gear and exhibited signatures consistent with mechanical overload, while the remaining 5 had been ground off. The respective idler gear shaft bore(s) at the back of the crankcase and at the accessory housing were missing approximately 1/3 of their circumferential material. The fracture surface(s) exhibited signatures consistent with overload. The overload forces appeared to have been applied inboard, evidenced by the symmetrical displacement of the bore material at each end of the subject idler gear shaft.
The National Transportation Safety Board determines the probable cause(s) of this accident to be: a loss of engine power due to the ingestion of foreign object(s) into the meshing of the gears, causing a malfunction of the magneto idler gear and failure of maintenance personnel to detect the signs of imminent failure during a mandatory oil filter examination to be performed at the time of an oil change, annual inspection, or engine overhaul. Contributing factors were unsuitable terrain for the forced landing, high crosswind weather conditions, and a parked vehicle in the landing area. Full narrative available
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