What happened
On May 2, 2022, at the Blois-Le Breuil aerodrome, a Nicollier HN700 aircraft, registered F-PADB, was involved in a fatal accident during a check flight. The pilot had been performing several maintenance tasks on the aircraft, which included the removal of a specialized manual rudder control system previously installed to accommodate the owner's disability.
After completing the maintenance, the pilot informed the AFIS officer of his intention to perform a check flight. During the take-off roll on runway 02, the aircraft accelerated but suddenly entered a left roll. The aircraft tipped over and collided with the ground approximately 300 meters from the runway threshold. The impact caused the engine to be torn from the airframe. The pilot was evacuated by helicopter but succumbed to his injuries.
The investigation
The BEA examined the wreckage and the control linkages of the aircraft. While the elevator, trim, and flap controls were found to be functioning correctly, the investigation focused on the aileron control system.
Investigators discovered that the roll control cables had been incorrectly reinstalled following the maintenance work. Specifically, the stick was actuating the wrong cable, and the cables were inverted on the left side. This configuration meant that a left roll input caused both ailerons to raise, and a right roll input caused both ailerons to lower. Consequently, the aircraft was uncontrollable in roll.
Findings
- The primary cause of the accident was the incorrect installation of the roll control cables during maintenance.
- The pilot performed critical maintenance tasks alone, without an independent inspection by a qualified mechanic or third party.
- The pre-flight inspection failed to detect that the flight controls were moving in the incorrect direction.
- The removal of the manual rudder control system had left the control linkage in a state where errors were possible during reassembly.