What happened
On March 28, 1999, a private Cessna A185F, registration OH-CIJ, performed an emergency landing in the village of Pöntsö, near Kittilä, Finland. The flight was a private operation traveling from Äkäslompolo toward Peltovuoma.
During the flight, while at an altitude of approximately 900 ft, the engine suddenly lost power. The pilot attempted to engage the electric fuel pump, which briefly restored power before the engine failed again. In an effort to reach a suitable landing site, the pilot turned toward a nearby road, but the aircraft struck the treetops of several pine trees. The aircraft then entered a flat spin, rotating approximately 190 degrees and striking more trees before coming to rest in a snowbank. The aircraft sustained substantial damage, including a broken left wing and a crushed engine compartment, but the pilot and passenger escaped without injury.
The investigation
Investigators examined the aircraft' and the fuel system extensively. While the pilot had performed a fuel level check using a dipstick and drained water from the fuel filter cup, the inspection of the fuel lines revealed that the fuel system was contaminated.
Technical examinations of the fuel lines and the main tank's vertical drain valve uncovered the remains of two housefly bodies and some sediment. Further inspection of the fuel filter revealed small aluminum chips and a piece of rubber seal. The investigation also looked into a previous engine malfunction that had occurred in March 1998, which had gone undocumented in the aircraft's logbook.
Findings
- The immediate cause of the forced landing was a fuel delivery failure resulting in engine power loss.
- The root cause was the inadequate protection of the fuel lines following a major repair or wing removal, which allowed insects to enter the fuel system.
- The presence of fly carcasses in the vertical drain valve of the main tank created a blockage that restricted fuel flow.
- A previous engine malfunction in 1998, likely caused by similar contamination, was not properly recorded in the aircraft logbook or reported to the authorities.
Safety action
- It is recommended that mechanics and maintenance organizations use the main tank's quick-drain valve during every fuel system maintenance procedure to clear any accumulated debris.