What happened
On December 28, 2022, a pilot was performing a wave flight over the Beskid Śląski mountains in an SZD-48-1 Jantar Std. 2, registration SP-3719. After a flight lasting over five hours, the pilot began a descent toward the Aleksandrowice airfield (EPBA). At an altitude of approximately 1,200 m AGL, the pilot extended the aerodynamic brakes and deployed the landing gear.
At approximately 15:15, while flying over the western part of the city of Bielsko-Aia at roughly 800 m AGL, the movable portion of the cockpit canopy detached from the fuselage. The canopy rotated on its rear hinge and struck the aircraft's horizontal stabilizer booms, causing damage to the paintwork and deforming a variometer tube. The pilot, distracted by sudden loud noises, turbulence, and the influx of cold air into the cockpit, did not immediately realize the physical impact of the canopy hitting the tail. The pilot declared an emergency, checked flight controls, and successfully landed the glider at the airfield without injury. The detached canopy was later recovered from a residential area approximately 2.6 km northeast of the airfield.
The investigation
The PKBWL investigation focused on the mechanical state of the canopy locking mechanism and the pilot's actions during the configuration change. The investigation examined the cockpit ergonomics, noting that the right-side canopy locking lever is located immediately adjacent to the landing gear lever. The investigators also considered the environmental conditions, including turbulence and the pilot's physical state after a long-duration flight.
Findings
- The primary cause of the incident was the pilot accidentally striking and unlatching the right-side canopy locking lever while moving the landing gear lever forward, which created a gap between the canopy and the fuselage.
- Mechanical play (looseness) in the canopy locking mechanism contributed to the instability of the closure.
- Vibrations caused by the use of aerodynamic brakes, combined with atmospheric turbulence, induced oscillations in the canopy that eventually caused the second (left-side) locking lever to disengage.
- The pilot's fatigue, cold exposure, and reduced perception following a multi-hour high-altitude flight likely prevented the detection of the accidental lever movement.
- The pilot's heavy winter clothing and use of a seat cushion for thermal insulation may have hindered visibility or increased the likelihood of accidental contact with the cockpit controls.