What happened
On September 8, 2013, at approximately 13:22, a Rans S-6 Coyote II ultralight aircraft, registration OH-U243, crashed near Haapavesi, Finland. The aircraft had departed from Haapavesi airport roughly 10 to 15 minutes prior to the accident for a local flight.
Following a single approach and climb-out over runway 12, the pilot was performing a standard landing pattern, likely flying a downwind leg for runway 30. Eyewitnesses observed the aircraft's attitude oscillating vertically several times during the end of the downwind leg, just as the aircraft would typically begin its turn to base. Subsequently, the aircraft banked sharply to the left and plunged into a field. The impact caused the aircraft to be destroyed and ignited a fire. The pilot, a 60-year-old with over 500 flight hours, sustained fatal injuries in the crash.
The investigation
The investigation examined the aircraft's maintenance history and the condition of the airframe. The aircraft, manufactured in 1990, had been upgraded with a Rotax 912 engine in 2010 and had undergone regular maintenance, including frequent strength testing of the fabric covering.
Investigators noted that the pilot had applied varnish to the synthetic fabric covering a few days before the accident. While the pilot had flown the aircraft after the application without noticing any changes, the post-crash technical examination could not determine if the varnish contributed to the accident due to the intensity of the fire. Additionally, medical examinations could not entirely rule out the possibility of a sudden medical event involving the pilot.