Ultralight Aircraft Crashes into Power Lines over Lake Hirsijärvi

Casualties unknown • FI

A single-engine Ikarus C42S struck a 20 kV power line while performing a low-altitude landing site inspection, resulting in the death of the pilot.

What happened

On August 8, 2006, at 20:16 local time, a privately owned Ikarus C42S ultralight aircraft, registration OH-U396, crashed into a 20 kV power line over Lake Hirsijärvi in Kisko, Finland. The aircraft, which was equipped with floats, had departed from the Inkoo archipelago approximately 35 minutes earlier with the intention of visiting the lake.

During the flight, the pilot performed a landing site inspection. While flying northwest over the prospective landing area at a speed of 62 knots (115 km/h), the aircraft struck the power line cables at an altitude of approximately 20 meters. The impact severed the lines and caused the aircraft to plunge into the lake, where it remained floating in an inverted position. The pilot, who was the sole occupant of the aircraft, sustained fatal injuries.

The investigation

The investigation established that there were no technical defects on the aircraft prior to the accident. The pilot had prepared for the flight using GPS data and maps, but the power line was not indicated on these resources, nor was it marked on official aeronautical charts.

Investigators examined the visibility of the hazard and found that the power line was extremely difficult to detect from the air. The supporting pylons, located 27 and 270 meters apart on opposite shores, were obscured by trees, with their tops positioned below the treeline. Furthermore, the power lines lacked any warning or identification markings. The investigation also noted that the pilot's method of inspecting the landing site—flying at very low altitudes—did not align with the training instructions provided by the Finnish Aeronautical Association, which recommend inspections at much higher altitudes (between 90 and 305 meters).

Findings

  • The pilot failed to detect the power line while flying at a low altitude over the lake.
  • The 20 kV power line was nearly impossible to see from the air because the supporting pylons were hidden by trees and the lines lacked warning markings.
  • The pilot's habit of performing the initial landing site inspection at a very low altitude, below treetop level, contributed to the collision.
  • The power line was not documented on the GPS, satellite imagery, or aeronautical charts used during flight planning.

Probable cause

The accident was caused by the pilot's failure to detect a 20 kV power line while performing a low-altitude landing site inspection, a hazard made nearly invisible by the lack of warning markings and the fact that supporting pylons were obscured by trees.

Frequently asked questions

What happened in the 2006-08-08 aircraft accident near FI?

A single-engine Ikarus C42S struck a 20 kV power line while performing a low-altitude landing site inspection, resulting in the death of the pilot.

What aircraft was involved and where did it happen?

The accident on 2006-08-08 involved a aircraft, registration OH-U396, at FI.

What was the probable cause of the accident?

The accident was caused by the pilot's failure to detect a 20 kV power line while performing a low-altitude landing site inspection, a hazard made nearly invisible by the lack of warning markings and the fact that supporting pylons were obscured by trees.

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