What happened
On November 27, 2008, a Mudry Cap 20 aircraft, registration F-AZNZ, was performing a local flight departing from the Chavenay aerodrome. After takeoff, the pilot proceeded toward the Osmoy aerobatic zone, located approximately 25 kilometers from the airfield. During the transit phase, the aircraft's canopy opened and became completely detached from the airframe. Following the separation, the pilot performed a turnaround and successfully landed the aircraft back at Chavenay.
The investigation
The investigation focused on the mechanical state of the canopy and the locking mechanism. Examination of the aircraft and the canopy revealed that the detached component had struck the right side of the fuselage, punctured the upper surface of the right wing, and damaged the leading edge of the right horizontal stabilizer.
Investigators determined that the canopy jettison mechanism had not been activated and did not malfunction. The rear left lock was found in the locked position and showed no signs of damage, and the associated locking pin remained intact. Consequently, the investigators concluded that the lock had simply not been engaged with the pin.
Technical analysis of the canopy structure indicated that the frame is susceptible to deformation. It was noted that the canopy could be closed with the locking pin positioned adjacent to the lock housing without actually engaging. Because the rear lock is located behind the pilot's left shoulder, visual confirmation of a secure lock is difficult. During flight, aerodynamic depression can cause the rear left portion of the canopy to lift and twist, which may cause the front left portion to slip out of the forward hook.
Findings
- The primary cause of the accident was the insufficient verification of the canopy lock prior to takeoff.
- The pilot had visually checked both the forward hook and the rear lock but failed to detect that the rear pin was not properly engaged.
- The physical position of the rear lock makes it difficult for the pilot to visually confirm engagement during pre-flight checks.
- The structural flexibility of the canopy allows for a false sense of security where the lock appears closed but is not seated in the pin.