NTSB Identification: ERA09LA490
14 CFR Part 91: General Aviation
Accident occurred Thursday, August 27, 2009 in Bainbridge, GA
Probable Cause Approval Date: 12/20/2010
Aircraft: PIPER PA-25-235, registration: N7339Z
Injuries: 1 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 airplane was performing a training aerial application over a farm field when the engine lost power and the pilot performed a forced landing to a field, where the airplane impacted a tree. A subsequent examination of the engine revealed that within the accessory section, the idler gear assembly, which normally transferred power from the crankshaft to the left magneto and the camshaft, had been displaced. The short shaft had also been displaced. The mounting plate retaining screws appeared to be sheared. The crankcase surface area around the screw hole exhibited rotational scoring, and the idler gear, located in the oil sump, had no missing or damaged gear teeth. Metal particles were found in the bottom of the crankcase and oil sump. The engine operating time was below the recommended time between overhaul. The failure sequence could not be determined, and although the left magneto had been replaced approximately 12 flight hours prior, the replacement of the magneto could not be correlated to the displacement of the idler gear assembly.

The National Transportation Safety Board determines the probable cause(s) of this accident to be:

A total loss of engine power due to the loss of camshaft timing as a result of the displacement of the idler gear assembly.

Full narrative available

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