What happened
On August 24, 2004, at approximately 16:43, a privately built and owned Colibri MB 2 ultralight aircraft, registration OH-U373, crashed into a rye field near Mäntsälä, Finland. The pilot had arrived at the private airfield for a practice flight. Prior to the accident, the pilot performed several takeoff runs on runway 22, during which they experienced difficulty maintaining the aircraft's heading. Between these practice runs, the pilot stopped the aircraft with the engine still running and opened the canopy to speak with bystanders.
The final takeoff occurred at approximately 16:25. After circling the airfield for about 10 to 15 minutes, the aircraft flew northwest toward Mäntsälä. Witnesses observed the aircraft flying normally before it suddenly entered a steep dive, rotating around its longitudinal axis to the right. The aircraft struck the ground at a vertical angle of 40–50 degrees, causing the total destruction of the aircraft and the immediate death of the pilot.
The investigation
The investigation examined the wreckage and the flight sequence. Investigators found that the engine had remained running until the moment of impact. While the aircraft did not break apart in mid-air, the canopy frame was found separated from the cockpit. The canopy lock was in the open position, and the limiting rope had snapped. Fragments of the acrylic canopy were found scattered along the crash path, with some pieces located 7/00 meters away from the impact site, indicating the canopy had opened while in flight.
Findings
- The accidental opening of the canopy lock lever during flight was the primary cause of the accident.
- The sudden opening of the large canopy created intense aerodynamic drag, which pulled the nose to the right and induced a rapid roll and steep dive.
- The pilot was unable to recover the aircraft due to the extremely low altitude at the time of the failure.
- Contributing factors included the possible absence of a tension spring in the lock lever and the lack of a secondary safety catch to prevent accidental opening.
- The pilot's limited recent flight experience and aggressive control inputs also contributed to the accident environment.