What happened
Approximately one and a half hours into the flight, the pilot initiated a standard procedure to switch the fuel supply from the right tank to the left tank. Immediately following this action, the engine began to run roughly before progressively losing power. Despite attempts to correct the issue, the pilot was unable to restore normal engine operation or maintain altitude.
The aircraft continued its descent until it impacted a body of water estimated to be 20 to 30 feet deep. Upon impact, the airplane sank and was not recovered from the water.
The investigation
Because the aircraft was not recovered, physical inspection of the airframe or engine was not possible. Consequently, the specific mechanical reason for the loss of engine power could not be determined through forensic analysis.