C2/​2010L Air­craft ac­ci­dent at Si­il­in­järvi on 20 Jan­u­ary 2010

15.11.2011

An aircraft accident took place at 11.26 on Wednesday, 20 January at Siilinjärvi Lehdonkylä village. A Cessna TU206G aircraft on power line inspection flight hit the ground and was destroyed. The pilot of the aircraft and the passenger, a power line inspector, were slightly injured.

The aircraft took off from Kuopio aerodrome and reached the power line to be inspected about three minutes after take off at 30 – 90 meters above ground level. The pilot adjusted airspeed to 80 – 90 kt resulting in a clearly lower power setting as compared to normal cruising speed setting. Approximately two minutes after starting the power line inspection the pilot noticed that the engine was running unevenly and coarsely and at the same time was losing power. Despite measures taken, the pilot was unable to recover engine power resulting in reducing air speed and the already existing low altitude had to be diminished to maintain air speed. Soon the pilot realized that the flight would end in a forced landing and radioed this to the air traffic control. The pilot managed to maintain control over the aircraft so that fatalities were avoided during a forced landing into the forest. The aircraft was destroyed.

The investigation focused on the aircraft engine and equipment contributing to its running. The engine was disassembled but no mechanic fault or damage contributing to engine malfunction was found. The fuel system of the aircraft was working and the fuel used was clean and according to standards. In order to determine the factors related to the engine malfunction, a simulated flight was flown, simulating engine power settings used on the flight and monitoring engine behavior during adjustment of engine controls and using the magneto switch and electric fuel pump. Engine failure did not occur. During the investigation it was found out that the pilot did not have training or experience in low flying or power line inspection. The pilot’s experience in the accident aircraft type can be considered low, too. During flight this became evident in lack of routine which led to pilot’s inadequate performance during engine failure.

The accident was caused by engine failure during flight, which as a result of loss of power, led to unprepared forced landing. Engine failure was probably caused by too lean fuel mixture. The emergence of the situation was contributed by both the pilot’s handling of the engine and low outer air temperature. The development of the failure into an accident was the result of the pilot’s action as he failed to enrich the fuel mixture after the beginning of the engine failure. Contributing factors were the pilot’s inexperience in low flying and the lack of needed training.

The investigation commission issued a safety recommendation to the aviation company to revise its flight manual regarding training requirements so that it includes the needed theory and flight training for low flying.

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