What happened
On October 21, 2007, a Mudry CAP 10 C, registration F-BXHD, departed from Chavenay-Villepreux for a local aerobatic flight. The pilot, flying solo, performed various aerobatic maneuvers between 09:59 and 10:07 UTC. Shortly after the maneuvers, the aircraft headed southeast, and radar contact was lost at 10:08 UTC. The aircraft subsequently crashed into the Bois des Longues Mares in the Ramboult forest, near Saint Léger en Yvelines. The impact was high-energy, and the pilot was killed.
The investigation
The investigation focused on the flight control systems, specifically the elevator control mechanism. Investigators examined the wreckage and found that the elevator control cables were still attached to the control surfaces, but the elevator cable used for pitch-up commands had become detached from its tensioner.
Technical examinations of the cable assembly revealed that while the pitch-down cable was secured with safety pins and safety wire, the pitch-up cable lacked safety pins. Furthermore, the safety wire on the pitch-up cable was broken, and there was no evidence of the wire securing the long end of the cable to the tensioner.
Laboratory testing was conducted to simulate the stresses of aerobatic flight. The tests demonstrated that when using a brass tensioner with grooves, the use of safety wire alone—without the use of safety pins—could lead to the unravelling of the assembly under dynamic loads. The tests showed that once the safety wire failed, only a few additional flight cycles were required to cause the complete detachment of the cable from the tensioner.