What happened
A Cessna 210K, registration N5767J, was performing a cross-country flight from Aalborg, Denmark, to Colmar-Houssen, France, when the engine lost power. The flight, which included a pilot and one passenger, had been operating with the landing gear extended due to a long-standing technical issue.
While approaching Colmar, the pilot contacted air traffic control to request landing priority, reporting a drop in oil pressure. Shortly thereafter, the engine power decreased significantly. Realizing an engine failure was imminent, the pilot identified a field for an emergency landing. During the final approach, the aircraft struck vegetation and a road before overturning in a cornfield. The two persons on board sustained serious injuries, and the aircraft was destroyed.
The investigation
The investigation focused on the aircraft's fuel management and the discrepancy between the estimated and actual fuel on board. Investigators examined the engine, fuel tanks, and the refueling process at Aalborg airport.
Key findings included:
- The engine and fuel system showed no mechanical defects that would cause power loss, though the engine oil pressure had dropped below manufacturer minimums.
- The refueling area at Aalborg was not level, which prevented the tanks from being filled to their true maximum capacity.
- The aircraft was equipped with recessed fuel caps, which do not allow for easy visual verification of a full tank, unlike raised caps.
- The pilot relied on the Engine Data Monitor (EDM) for fuel tracking, but the initial fuel quantity entered into the system was incorrect.
Findings
The primary cause of the accident was fuel exhaustion resulting from a combination of several factors:
- The pilot refueled on a non-horizontal surface, leading to a fuel load that was approximately 6 US gallons less than the maximum usable capacity.
- The pilot entered an erroneous initial fuel quantity of 90 US gallons into the EDM, creating a false baseline for all subsequent calculations.
- An inappropriate engine power setting and air-fuel mixture during cruise led to a fuel consumption rate higher than the pilot's estimates.
- The pilot's attention was likely diverted by monitoring declining oil pressure, causing him to overlook the actual fuel state.
- The pilot was unaware of an FAA Airworthiness Directive regarding the specific difficulties of refueling this aircraft model using recessed caps.