This May 2008 accident report is provided by the National Transportation Safety Board. Published as an educational tool, it is intended to help pilots learn from the misfortunes of others.
Aircraft: Ercoupe. Injuries: None. Location: Penngrove, Calif. Aircraft damage: Substantial.
What reportedly happened: The plane was in cruise flight when the engine lost power. The pilot noted the oil pressure fluctuated and the engine sputtered. Attempts to restore power were unsuccessful and the pilot executed a forced landing in an alfalfa field. The grass was 2 to 3 feet high. During the landing roll the plane skidded sideways and the tail dug into the ground. The airplane’s tail cone was buckled, and the right vertical stabilizer and rudder were bent.
FAA inspectors found that both magnetos had frayed primary wires, known as P-leads, which could have been shorting out and intermittently killing the ignition system. They noted numerous additional maintenance discrepancies with the airplane, however, none of these would have contributed to a loss of engine power. According to the inspectors, the airplane’s most recent annual inspection was completed about two months before the accident. The maintenance discrepancies found by the FAA inspectors, including the frayed “P” leads, should have been repaired during this annual inspection.
Probable cause: The loss of engine power resulting from frayed magneto “P” leads. Contributing to the accident was the lack of suitable terrain for the forced landing.
For more information: NTSB.gov