What happened
On 20 December 1994, an aircraft type single-engine piston aircraft (registration N911SG) landed at Oulu airport in Finland during a flight from Germany to Russia. The aircraft was carrying a pilot, a passenger, and a company representative. Following the landing, the pilot notified air traffic control that the aircraft required refueling but did not specify the fuel grade. An air traffic controller subsequently informed the fuel provider that the aircraft required jet fuel.
During the refueling process, a tanker car delivered 664 litres of JET A-1 fuel into the tanks, which should have been filled with AVGAS 100LL. The company representative, acting as a crew member, supervised the process, confirmed the fuel sample, and signed the delivery receipt. The aircraft departed Oulu at 16:19 for Murmansk. Shortly after takeoff, air traffic controllers noted a low climb gradient. Approximately four minutes into the flight, the crew requested to return to the airport due to technical difficulties. During the approach, the crew issued a mayday call reporting that both engines were failing. The aircraft crashed in a forested area near the Laanila NDB. The impact resulted in one fatality and two injuries. The passenger died at the scene, while the pilot succumbed to injuries ten days later.
Findings
- The primary cause of the engine failure was the use of incorrect fuel grade.
- The aircraft's fuel tanks lacked markings indicating the minimum required aviation gasoline grade.
- Although the refueling nozzle featured an expansion designed to prevent jet fuel nozzles from entering avgas orifices, the nozzle tip was shaped as a Camlock coupling, which was small enough to fit into the reduced filling orifices.
- The company representative present during the refueling process accepted the fuel and authorized the delivery without verifying the fuel type.