What happened
On June 11, 2016, a Grob G 103, registration OK-8144, was performing circuit training flights at Frýdlant airport. During the third flight of the session, while approaching the fourth circuit turn, the front cockpit canopy opened unexpectedly. The pilot managed to close the canopy; however, during the final approach to runway 26, the canopy opened a second time.
While attempting to reseal the canopy, the pilot's concentration was diverted from flight controls. Consequently, the glider touched down on the grassy area approximately 65 meters before the runway threshold. Upon touchdown, the left wing made contact with vegetation, causing the aircraft to rotate 180 degrees around its vertical axis. The glider continued to slide backward for approximately 75 meters before coming to a halt 25 meters from the runway threshold. The pilot was uninjured.
The investigation
The ÚZPLN examined the aircraft's locking mechanism and the sequence of events. The investigation established that the aircraft was airworthy and the pilot was fully qualified. The investigation focused on why the canopy failed to remain closed despite the pilot's attempt to secure it after the first incident.
Technical analysis of the locking system revealed that if the canopy frame is not perfectly seated, the locking rod may hit the edge of the second eye (part of the canopy) prematurely when the handle is moved to the forward locked position. In such a state, the spring pressure on the locking rod is insufficient to fully engage the second and third eyes located on the fuselage. The investigation noted that if the canopy is correctly closed and locked, spontaneous opening without structural damage to the locking components is impossible.
Findings
- The pilot failed to maintain sufficient concentration on the landing phase due to the distraction caused by the canopy malfunction.
- The pilot likely failed to verify the correct locking of the canopy before the flight or may have confused the canopy locking handle with the flap or trim controls during the flight.
- The primary cause of the accident was the pilot's loss of concentration on flight controls while attempting to resolve the canopy issue.
- The aircraft sustained cracks to the fuselage and wings, as well as cockpit damage, all resulting from the ground contact and subsequent rotation.