What happened
On August 8, 2020, at approximately 11:15 LMT, a PW-6U glider, registration SP-3881, departed from Kąkolewo Airport (EPPG) for a training flight. The aircraft was being operated by a pilot with approximately 750 total flight hours, including 290 hours as an instructor. The pilot was seated in the rear cockpit, accompanied by a passenger in the front seat.
Following a tow takeoff, the glider climbed to 600 m before releasing from the tow plane. After reaching an altitude of approximately 400 m within a thermal, the pilot began performing aerobatic maneuvers. A second sequence of aerobatics commenced at an altitude of 1200 m. During a loop maneuver, while the aircraft was in a vertical upward climb at approximately 600 m, the rear canopy detached from the cockpit. The canopy fell and struck the aircraft's vertical stabilizer. The pilot successfully completed the loop, reduced airspeed, deployed aerodynamic brakes, and landed the aircraft safely.
The investigation
The investigation examined the condition of the aircraft and the cockpit locking mechanisms. Although the pilot stated that both the front and rear canopies had been verified as properly closed and secured prior to takeoff, the investigation found the canopy opening lever on the frame was displaced 30 mm from the closed position. The canopy was found shattered on the runway.
Post-incident inspections of the SP-3arg revealed that the canopy locking pins (bolts) had not been deformed. This indicated that the canopy likely opened because the lock itself had become disengaged.
Findings
- The primary cause of the incident was the unlocking of the right canopy handle/lock due to looseness developed during the aircraft's operation.
- The impact of the falling canopy caused damage to the vertical stabilizer, which sustained scratches.