What happened
The aircraft was engaged in agricultural operations, executing a swath run to spray crops. During this phase of flight, the engine experienced a sudden loss of power. At the time of the failure, approximately 200 yards of level field remained available for an emergency landing attempt.
After touching down on the remaining runway section, the pilot attempted to maneuver the aircraft to avoid colliding with nearby trees. During this evasive turn, the nose gear dug into the ground surface. This impact caused the aircraft to pitch forward violently, resulting in a nose-over accident.
The investigation
Post-accident examination of the engine revealed that the magneto coupling was locked and unable to rotate. Further mechanical inspection identified excessive play within the pawls, as well as worn striker pins and shaft splines.
Review of the aircraft logbooks indicated that Airworthiness Directives AD 78-09-07 and AD 82-20-01 had been complied with approximately 19 flight hours prior to the incident. However, the records showed that the make, model, and serial numbers of the magnetos were not entered as required by regulation.
Findings
The primary mechanical failure was attributed to the locked magneto coupling. Contributing factors included the worn internal components of the magneto drive system and inadequate record-keeping regarding specific part identification during previous maintenance.