What happened
On July 1, 2013, a SZD-9 bis 1E glider was performing a winch launch at the EPBA aerodrome. Shortly after the aircraft became airborne, at an altitude of approximately 50 meters, the rear cockpit canopy cover opened and detached from the glider. The glazing of the canopy struck the ground and shattered; however, the aircraft itself sustained no structural damage. Following the detachment, the pilot completed the launch sequence, performed a circuit over the aerodrome, and landed the aircraft safely.
Prior to the flight, the instructor had verified that the rear canopy cover was properly closed and locked.
The investigation
The investigation focused on the mechanical integrity of the canopy locking mechanism. Upon inspection of the locking knob, investigators determined that the spring pressure holding the knob in place was significantly weaker than that found on other SZD-9 bis 1E (Bocian) gliders in the fleet.
During the takeoff roll, the student pilot performed an excessively abrupt control input, causing the glider to land heavily on both the front and tail skids. This impact likely caused the locking knob to move due to inertia, which, combined with the insufficient spring tension, allowed the lock to disengage.
Findings
- The primary cause of the incident was the insufficient spring pressure on the canopy locking knob, which failed to maintain the lock against inertial forces.
- The heavy impact on the skids during the takeoff roll, caused by abrupt student pilot control inputs, provided the physical impulse necessary to dislodge the weakened lock.
Safety action
Following the incident, the following preventive measures were implemented by the operator:
- A fleet-wide inspection of the spring pressure on all other SZD-9 bis 1E gliders operated by the Bielsko-Bialski Aero Club was conducted.
- The incident was reviewed with flight instructors to emphasize the importance of rigorous verification of the canopy locking and securing procedures.