NTSB Identification: LAX07LA234.
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Accident occurred Friday, July 27, 2007 in Ramona, CA
Probable Cause Approval Date: 03/31/2008
Aircraft: Piper PA-24-260, registration: N8637P
Injuries: 2 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 pilot was performing a test flight to confirm the operation of newly installed avionics. During the return flight to the airport, the engine began to "backfire" and then lost all power. The pilot went through the emergency checklist, but was unable to restart the engine. The pilot force landed the airplane in a dirt field with the landing gear retracted. Both fuel tanks were found to be approximately 1/2 full. Further examination of the airframe revealed a short circuit of both magneto grounding leads in the electrical wiring between the magneto switch and the magneto. The investigation determined that he wiring harnesses were original to the airplane, which was manufactured in 1964. Investigators were able to successfully start the engine and perform a run-up under two separate conditions. The first engine start occurred after investigators disconnected both p-leads at their respective magneto terminals. The second engine start occurred after new electrical wire was connected from the magneto switch to both magnetos. Investigators noted the general overall poor condition of the p-lead electrical wiring. A review of the engine logbook revealed that the engine had been returned to service following a 100-hour inspection about a month prior to the accident. The engine logbook entry indicated that maintenance personnel checked wires, cables, and hoses for condition and security.

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

A total loss of engine power due to a short circuit between both magneto ground leads. A factor in the accident was the inadequate annual/100-hour maintenance inspection regarding the wires.

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