NTSB Identification: CEN09LA284
14 CFR Part 91: General Aviation
Accident occurred Friday, May 08, 2009 in Alpine, TX
Probable Cause Approval Date: 04/22/2010
Aircraft: CESSNA 421B, registration: N60HG
Injuries: 1 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.

Shortly after departure, when the airplane was about 400 feet in the air, the right engine stopped producing power. The pilot conducted a forced landing in a nearby field. An on-site inspection revealed that the airplane fuel tanks contained plenty of fuel. A post accident examination of the engines was conducted. An engine monitor was downloaded; a sudden decrease in cylinder head (CHT) and exhaust gas (EGT) temperature readings were observed for the right engine. A visual inspection of the engine revealed that the idler gear support pin, located on the rear of the engine, had backed out. The idler pin's retaining hardware (two nuts and lock-washers) were missing. The idler pin's movement allowed the idler gear to drop and become disconnected from the magnetos drive gear, resulting in a loss of engine ignition. Additionally, due to the mis-located idler gear, the accessory drive gears on the cam and crankshafts were either ground down or broken. Disassembly of the engine, found numerous metal pieces in the engine's oil sump.

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

The loss of engine power due to disengagement of the magneto idler gear support pin.

Full narrative available

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