What happened
On May 3, 1999, an Akrotech G 202, registration F-WSKY, was performing aerobatic training maneuvers near the Ancenis aerodrome. During the flight, the pilot was executing a series of basic figures to prepare for a training program. While performing a right-hand roll, the aircraft's canopy suddenly shattered and detached from the airframe. The sudden loss of the canopy caused fragments of plexiglass to strike the pilot, resulting in head injuries.
During the separation, a portion of the canopy locking mechanism was thrown backward, impacting the aircraft's right horizontal stabilizer. Despite the structural damage and the debris inside the cockpit, the pilot was able to maintain control and successfully land the aircraft at Ancenis.
The investigation
Investigators examined the wreckage of the F-WSKY and the flight site, which was located within a designated aerobatic box between 1,500 and 3,500 feet. The aircraft, a two-seat tandem kit plane, was found to have lost almost the entire canopy, leaving only the hinges and parts of the carbon fiber frame.
The investigation focused on the design of the canopy assembly, which consisted of 7mm thick plexiglass set into a carbon fiber frame. The canopy operated on a single axis via two hinges on the right side and was secured by two locking pins. Investigators noted that the carbon fiber fuselage is significantly more rigid than the canopy frame itself. They also analyzed the load factors recorded by the aircraft's analog accelerometer, which showed a peak of +6.8g and a minimum of -2.5g during the flight.
Findings
Technical analysis revealed that the canopy frame was subject to intense aerodynamic forces, particularly during asymmetrical maneuvers. Because the fuselage is more rigid than the canopy, the frame must absorb significant stress. The investigation identified two critical structural weaknesses in the frame:
- The lack of rigidity in the forward section could allow the frame to deform, potentially causing the locking pin to disengage from its housing.
- The central area of the frame, near the opening handle, was prone to notable deformation, a weakness exacerbated by the hole drilled for the handle axis.
Once deformation began, the interior of the canopy acted like a scoop, catching the wind and creating massive aerodynamic pressure. The investigators concluded that the canopy frame was undersized, leading to the structural failure and the subsequent explosive rupture of the plexiglass.
Safety action
Following the accident, the manufacturer implemented structural reinforcements to the forward canopy frame and added a third anchoring point at the opening handle. These modifications have since been applied to G202 aircraft operating in France.