AVON, MS, USA
N73135
Air Tractor AT-401
DURING A TURN FOR A SPRAY PASS, THE PLT STATED THAT THE ENG QUIT. HE THEN OPENED THE CHEMICAL DUMP VALVE & LANDED THE ACFT PERPENDICULAR TO PLOWED ROWS IN A FIELD. THE ACFT THEN NOSED OVER AFTER TOUCHDOWN & THE PLT WHO WAS UNCONSCIOUS, WAS CUT FREE FROM HIS SEATBELT & SHOULDER HARNESS. EXAM OF THE ACFT AT THE ACCIDENT SITE REVEALED THAT THE MAGNETO SWITCH WAS POSITIONED TO 'BOTH.' THE ACFT WAS RECOVERED & THE ENG WAS STARTED & OPERATED NORMALLY WITH THE MAGNETO SWITCH POSITIONED TO THE BOTH POSITION HOWEVER WHEN THE MAGNETO SWITCH WAS POSITIONED TO THE LT POSITION, THE ENG QUIT. THE LT MAGNETO WAS REMOVED FOR DISASSEMBLY. EXAM OF THE LT MAGNETO REVEALED THAT A PHENOLIC GEAR WHICH DRIVES THE ROTATING MAGNET WAS DAMAGED WHICH PREVENTED THE MAGNETO FROM PRODUCING SPARK. NO DETERMINATION COULD BE MADE AS TO THE REASON FOR THE LOSS OF ENG POWER.
LOSS OF ENGINE POWER FOR UNDETERMINED REASONS DURING A TURN WHILE ON AN AERIAL APPLICATION FLIGHT. CONTRIBUTING TO THE ACCIDENT WAS FAILURE OF THE LEFT MAGNETO DUE TO FAILURE OF A PHENOLIC GEAR WHICH DRIVES THE ROTATING MAGNET.
Source: NTSB Aviation Accident Database
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