What happened
While operating in cruise flight, the aircraft experienced a complete loss of all engine power. In an attempt to restore power, the pilot performed several actions, including switching fuel tanks and activating the electric fuel boost pump. However, the engine failed to restart. The pilot subsequently landed the airplane in a rocky riverbed, which resulted in the aircraft nosing over.
At the accident site, a witness observed that fuel was leaking from both wings. Upon inspection of the cockpit controls at the scene, the magnetos and the electric fuel boost pump switches were found in the ON position.
The investigation
The NTSB investigator-in-charge and an FAA airability inspector conducted a mechanical examination of the engine. During this process, they operated the engine on the aircraft and observed no anomalies.
As part of the detailed inspection, investigators removed and internally inspected all flexible fuel lines. Additionally, the electric fuel pump and the bypass valve were removed and tested. The investigation included following all troubleshooting procedures outlined in the IO-520 maintenance manual, and no mechanical defects or anomalies were identified during these tests.