What happened
On August 26, 2001, a Grob G103C TWIN III SL motor glider, registration PH-9CO, was conducting a local instructional flight from Midden-Zeeland airport. During the final approach for runway 27, the aircraft was flying at a relatively low speed with a high nose attitude and extended airbrakes.
At an altitude of approximately 80 meters, the forward cockpit canopy suddenly opened and remained in the fully open position. The student pilot attempted to close the canopy but was unsuccessful. This event caused the aircraft to yaw to the left, subsequently entering a left-hand spin. The aircraft completed a 360-degree rotation before impacting a beet field south of the runway extension. The student pilot sustained fatal injuries, while the instructor suffered severe injuries and fell into a coma.
The investigation
The investigation examined the aircraft's mechanical condition, the cockpit control configuration, and the flight sequence. Investigators analyzed the design of the Grob G103C TWIN III SL, specifically noting that the handles for the airbrakes and the canopy release mechanism are located near each other on the left side of the cockpit. While the handles differ in color, shape, and required physical effort, they are positioned such that they can be confused.
Witnesses confirmed that the pre-flight checks had been performed and that the handles were set to the locked position. The investigation also looked into whether the aircraft's weight and balance were within limits, confirming that the loading was legal. Furthermore, the investigation reviewed the possibility of the canopy opening due to aerodynamic forces or pilot error in handling the controls.
Findings
- The primary cause of the accident was the accidental activation of the canopy release lever instead of the airbrake lever.
- The cockpit controls for the airbrakes and the canopy locking mechanism are positioned closely together, which can lead to confusion.
- The aircraft was in a high-nose, low-speed configuration during the approach, a state that made the aircraft susceptible to the aerodynamic disruption caused by the opening canopy.
- The student pilot was unable to re-secure the canopy once it had been released during the flight.