Accident Overview
Shortly after departing, the aircraft's engine lost all power. The pilot executed a forced landing, touching down in a soybean field. The airplane, manufactured in 1941, sustained damage during the landing.
Examination Findings
Post-accident examination of the wreckage uncovered an electrical fault in the ignition system. When the magneto switch was placed in the "BOTH" position, an ohmmeter indicated that the circuit was grounded. Further inspection revealed that two ignition switch leads had become chafed over time, making contact with a screw and creating a direct ground path. This grounding effectively shorted the magneto circuit, preventing spark generation.
The chafing appeared to have developed gradually over a long period, likely due to vibration or abrasion against the screw. The wiring insulation had worn away, exposing the conductors.
Probable Cause
The engine lost all power because chafed ignition switch leads grounded against a screw, causing the magneto circuit to be shorted. This defect likely resulted from prolonged wear of wiring insulation.