What happened
While approximately 45 miles from landing, the RPM of the left engine began to fluctuate. As the aircraft reached about 15 miles from the landing site, the left engine lost power altogether. The pilot reported that the aircraft was unable to maintain its altitude.
Unable to reach the runway, the pilot performed a ditching in Hodo Bay, approximately one-quarter mile from the shore and 1.5 miles from the airport. The aircraft gross weight at the time of the accident was approximately 9,108 lbs.
The investigation
Following the retrieval of the aircraft and the left engine, a mechanical examination was conducted. Investigators determined that the accessory gear drive shaft had failed due to torsional overload.
Inside the engine case, investigators found an area of gouging and abrasion located directly in front of the starter gear. The accessory drive gear is responsible for driving the left magneto, fuel pump, and propeller governor. Examination of the gear teeth revealed deep impressions on approximately 70% of the teeth, with evident material displacement and gouging.
Additionally, evidence suggested that the collector drive floating gear may have moved forward and made contact with the engine case. The investigation also identified evidence of mechanical interference within the accessory drive gear system.