What happened
On March 3, 2021, a Cap 10B/C aircraft, registration HB-SAW, departed from Geneva Airport (LSGG) for a flight training session focused on aerobatic maneuvers. The flight was conducted under Visual Flight Rules (VFR) with an instructor and a student pilot on board.
During the session, the instructor directed the student to perform two consecutive left rolls. While the first roll was completed successfully, the student failed to maintain the correct attitude during the second roll, resulting in the aircraft's nose being too low relative to the horizon while flying inverted. The instructor identified the error and instructed the student to correct the attitude by pushing the elevator. However, the student instead applied a pull input. This error caused the aircraft to enter a downward half-loop, leading to a rapid increase in airspeed and a maximum recorded acceleration of 8 g. The aircraft lost approximately 400 meters of altitude during the maneuver. Following the event, the crew returned to Geneva Airport and landed without further incident.
The investigation
The Swiss Transportation Safety Investigation Board (SUST) examined the technical and operational aspects of the event. The investigation confirmed that the aircraft's weight and center of gravity were within prescribed limits and that the pilots held appropriate licenses. No mechanical failures or external environmental factors, such as weather, were found to have contributed to the incident.
Technical analysis focused on the structural impact of the high G-load. The Cap 10B/C is rated for a maximum load factor of 6 g. The recorded 8 g load exceeded this limit by 1.73 g. The manufacturer, acting as the type certificate holder, subsequently declared the aircraft unairworthy, stating that the airframe and engine could not be restored to a safe condition.
Findings
- The primary cause of the incident was a significant exceedance of the load factor resulting from a student pilot's execution error during an aerobatic maneuver.
- The student pilot applied a pull input instead of the required push input while flying inverted.
- The instructor was unable to intervene in time to prevent the high-G maneuver.
- The structural integrity of the aircraft was compromised by the 8 g acceleration, leading to the permanent grounding of the airframe.