What happened
On June 22, 2008, at approximately 22:20 local time, a Quad City Challenger II ultralight aircraft, registration OH-U545, experienced a loss of control during a test flight near Vampula, Finland. The pilot was conducting the second flight of the day under VMC conditions. During the flight, the pilot encountered difficulties maintaining control, specifically noting that a right-hand turn was insufficient despite applying full control deflection.
As the aircraft encountered wind gusts, it entered a left-hand spin. Although the pilot managed to recover from the initial spin, the aircraft entered a second spin following a power adjustment. Unable to arrest the descending altitude or prevent a leftward bank, the pilot performed a forced landing in a nearby field. The aircraft sustained heavy damage, including a bent right wingtip, collapsed landing gear, and a damaged cockpit floor, but the pilot escaped without injury.
The investigation
The investigation examined the aircraft's mechanical condition, the pilot's experience, and the flight parameters. Investigators looked into recent maintenance, including a repair made by the pilot to the left aileron hinge bolt and pushrod/pullrod, which had been damaged while the aircraft was parked.
Technical inspections revealed significant mechanical issues within the control surfaces. The left aileron exhibited insufficient effectiveness due to an ovalized hinge bolt attachment hole, excessive play in the control system, and loose fabric covering. Furthermore, the investigation found that the pilot's physical size limited the lateral movement of the control stick. The investigation also noted that the pilot had previously added an unauthorized 4.3 kg weight to the tail to adjust the center of gravity, which had caused vibrations during earlier flights.
Findings
- The primary cause of the accident was the aircraft entering a left-hand spin.
- Insufficient aileron authority prevented the pilot from regaining control of the aircraft.
- The pilot performed unauthorized repairs to the left aileron system.
- Mechanical deficiencies, including excessive play in the control linkages and an ovalized hinge hole, contributed to degraded control effectiveness.
- The pilot's physical anatomy (thighs) restricted the lateral movement of the control stick.
- The use of an unreliable anemometer as an airspeed indicator made it difficult for the pilot to accurately determine airspeed.
- The pilot's flight experience was limited, particularly regarding this specific aircraft type during the test flight program.
Safety action
- The investigators recommended that the Finnish Civil Aviation Authority clarify the experience requirements for pilots conducting test flights and provide necessary guidance to the Finnish Air League.