Accident Overview
During the initial climb phase, the pilot observed smoke in the cockpit and heard a backfire from the engine. Shortly thereafter, the engine lost power. The pilot executed a forced landing in a field characterized by rough and uneven terrain. During the landing roll, the aircraft struck a ditch, resulting in damage to the airframe.
Investigation Findings
A post-accident visual inspection identified that the left exhaust muffler had failed at its outlet. This failure allowed hot exhaust gases to enter the engine compartment. The hot gases subsequently damaged the voltage regulator, alternator, and the magneto wiring (P-leads). With the P-leads compromised, the magnetos would have been rendered inoperative, which is consistent with the loss of engine power.
Maintenance History
The airworthiness directive AD 76-23-03 mandated an inspection of the exhaust system every 100 hours of operation. Records indicated that the last compliance with this directive occurred on August 18, 1982. However, the aircraft had accumulated only 50 flight hours since that date, remaining within the inspection interval.