What happened
On June 30, 2010, an EV-97 Eurostar ultralight aircraft, registration OH-U430, crashed near the Jämijärvi airfield during a cross-country flight. The flight was intended to pick up a passenger from Jämijärvi and proceed to Tampere-Pirkkala aerodrome.
Shortly after takeoff, the aircraft's canopy opened mid-flight, causing various items, including documents and briefcases, to fall from the cockpit. Following the opening, the aircraft maintained an altitude of approximately 120 meters while losing airspeed. After a brief period of level flight, the altitude dropped rapidly to about 50 meters. The aircraft then experienced a significant leftward turn and a loss of speed before impacting the ground nearly vertically, approximately one kilometer west of the airfield. The impact occurred less than one minute after takeoff, resulting in two fatalities and the total destruction of the aircraft.
The investigation
The investigation examined the mechanical state of the canopy locking mechanism and the environmental conditions at the time of the accident. Investigators found that the aircraft's canopy had undergone some modifications, but the installation was incomplete. Specifically, a critical part intended to enhance the reliability of the lock had not been replaced. The investigation also looked into the manufacturer's instructions regarding these modifications and the pilot's actions following the canopy opening.
Findings
- The primary cause of the accident was the loss of aircraft control following the opening of the canopy. The airflow disturbance from the open canopy caused severe vibrations in the horizontal stabilizer, elevator, and control stick, and induced a significant nose-down tendency.
- The pilot likely attempted to close the canopy during the emergency, which led to a failure to properly monitor essential flight parameters.
- The canopy opened due to aerodynamic forces caused by strong, gusty winds, which induced momentary structural deformations in the airframe.
- While the manufacturer, Evektor-Aerotechnik a.s., had issued a bulletin to improve the locking mechanism, the aircraft was not fully updated. One vital component remained unreplaced, partly because the manufacturer's instructions for installing the new parts were inadequate, and partly because the owners believed the existing modifications were sufficient.
Safety action
Following the investigation, two safety recommendations were issued to the manufacturer, Evektor-Aerotechnik a.s.:
- The manufacturer should publish emergency procedures in the EV-97 Eurostar pilot's operating handbook for situations where the canopy opens during flight.
- The manufacturer should issue a corrected instruction bulletin for the canopy locking mechanism modification to ensure it accurately reflects the required installation procedures.