Refueling Error
The aircraft, registered N911SG, arrived at Oulu Airport from Bremerhaven, Germany on December 20, 1994, at 15:03 local time. The flight was intended to continue to Murmansk, Russia. On board were the pilot-in-command, a passenger, and a representative of the operator company who was listed as a crew member. After landing, the pilot requested refueling from air traffic control but did not specify the fuel type. The ATC officer relayed the request to the fuel company, stating that the aircraft needed JET. Subsequently, 664 liters of Jet A-1 were delivered, whereas the aircraft required Avgas 100LL.
The refueling was performed by a tanker car dedicated to Jet A-1 and clearly labeled. The operator's representative was present, approved a fuel sample, signed the delivery receipt, and paid in cash. He instructed the quantity. The aircraft's fuel tanks lacked markings for minimum fuel grade, as required by airworthiness standards. The filler orifices had restrictors designed to prevent jet fuel nozzles from entering, but the tanker nozzle had a Camlock coupling tip smaller than the expansion intended to prevent misfueling, allowing the jet fuel nozzle to fit into the avgas orifices.
Flight and Accident
The aircraft departed Oulu at 16:19 on an IFR flight plan to Murmansk, with an alternate at Ivalo and a flight time of 1 hour 35 minutes. After takeoff from runway 30, the climb gradient was noted as low by the ATC officer. At 4 minutes 47 seconds after takeoff, the crew requested to return due to problems. At 16:25:25, they reported the field in sight and a DME distance of 6 nm. At 16:26:11, the crew transmitted a mayday stating both engines were stopping. A second mayday at 16:26:38 reported an emergency landing. Radar contact was lost at 16:26:30. Rescue units found the aircraft at 17:06 in a forest, having struck trees, flipped upside down, and been destroyed.
Occupants and Injuries
The aircraft door was shut; occupants were inside. The passenger in the back seat had been thrown from his seat and was found dead at the scene. The pilot-in-command, in the left front seat with his seat belt fastened, was seriously injured and unconscious; he died from his injuries on December 30. The occupant in the right crew seat, also with seat belt fastened, was injured but conscious; investigation revealed that person was actually a passenger.
Probable Cause
The accident was caused by incorrect refueling. This was made possible by a series of human errors, which together with the fact that the technical defenses failed, permitted the aircraft to be refueled with Jet A-1 instead of Avgas 100LL. The incorrect fuel caused knocking, which resulted in engine damage and eventual stopping of both engines.