Incident Description
On August 8, 2020, at approximately 11:15 local time, a glider pilot with a passenger on board departed from Kąkolewo airfield (EPPG) in a PW-6U glider (registration SP-3881) for a training flight. The pilot, who had about 750 total flight hours (including 290 as an instructor), occupied the rear cockpit. The glider was towed by an aircraft and released at 600 meters altitude. After gaining about 400 meters in a thermal, the pilot began performing aerobatics. Following a sequence of figures at 400 meters, the glider climbed again in a thermal, reaching 1200 meters over the airfield before starting another aerobatic sequence.
During the execution of a loop at approximately 600 meters, when the glider was in the vertical climb phase (end of the first quarter of the loop), the rear canopy separated from the glider. As it fell, the canopy struck the vertical stabilizer, causing scratches. The pilot completed the loop, reduced speed, deployed the airbrakes, and landed without further incident.
According to the pilot's statement, before takeoff he ensured that both the front and rear canopies were properly closed and locked. The canopy was later found broken on the runway. The canopy opening lever on its frame was displaced 30 mm from the closed position. During post-flight inspection, the operator noted that the canopy locks (pins) were not deformed, indicating that the canopy most likely opened due to the lock becoming unlatched. The incident occurred during the 296th flight of the glider, which had a total flight time of 153 hours.
Findings
- The canopy detached during a loop at about 600 meters altitude.
- The canopy struck the vertical stabilizer, causing scratches.
- The canopy opening lever was found 30 mm from the closed position.
- The lock pins showed no deformation, suggesting the lock released spontaneously.
- The glider had accumulated 153 flight hours over 296 flights.
Probable Cause
The most likely cause of the incident was the unlocking of the right handle/lock of the canopy due to clearances that developed during the glider's operation.