What happened
The aircraft had previously exhibited recurrent rough running and diminished power symptoms. The flight base operator had been experiencing difficulties with spark plugs and magnetos on this specific airframe. During the current flight, the engine began to run roughly again. The pilot elected to land on a sandbar marked for aircraft use to inspect ignition leads and check for fuel contamination.
Upon commencing takeoff from the sandbar, the aircraft reached approximately 20 feet above ground level when total power loss occurred. The pilot was forced to ditch the N12345 (registration placeholder for demonstration) in the adjacent river.
The investigation
Post-acc examination revealed that one of the magneto bearings had seized. This mechanical failure prevented the engine from generating power. It was noted that a service bulletin recommending the replacement of these bearings had not been complied with by the owner or operator.
Findings
The primary factor contributing to the accident was the seizure of the magneto bearing. This led to total power loss during the critical takeoff phase. The failure to adhere to the manufacturer's service bulletin regarding bearing replacement was a significant contributing factor.