What happened
The aircraft experienced an in-flight flameout while the pilot was maneuvering over a ridge line. This event occurred after the aircraft had been operating for more than one hour without refueling, even though fuel was available at the last point of departure. At the time of the engine failure, the pilot reported being only five miles from the intended destination.
The investigation
Post-acc examination revealed significant discrepancies regarding the fuel state. The pilot stated that the fuel gauges indicated six gallons remained on board. However, technical analysis suggests that approximately two gallons of this amount were unusable during level cruise conditions, with a larger portion becoming inaccessible due to fuel sloshing during maneuvers. An FAA inspector who drained the aircraft after the incident estimated that only about four gallons were actually present.
Findings
The flameout was caused by fuel exhaustion resulting from flow interruption. This interruption occurred because the remaining fuel could not reach the engine intake while the aircraft was maneuvering over uneven terrain. The pilot did not attempt to restart the engine. It is noted that the specific aircraft model lacks an auto-relight system, meaning the engine cannot re-ignite without manual intervention or external ignition sources.
Safety message
Pilots operating in mountainous terrain should ensure adequate fuel reserves are maintained well before reaching ridgelines. Maneuvering over such terrain can cause fuel sloshing, rendering usable fuel inaccessible even if gauges suggest otherwise. Refueling at intermediate stops is critical when operating near terrain limits.