What happened
On May 1, 2001, a Mudry CAP 21, registration F-GDTR, was performing aerobatic training maneuvers over the Auch airfield in France. The pilot was executing a complex sequence involving a three-roll vertical climb, a pushed roll, and a descending vertical negative roll.
During the final phase of the maneuver, the pilot applied significant nose-down inputs to transition into the descending vertical component. At this moment, the elevator control linkage disconnected, rendering the aircraft uncontrollable in pitch. The aircraft continued on a vertical descent path and struck the ground. The impact resulted in the death of the pilot and the destruction of the aircraft.
The investigation
Investigators examined the wreckage and found the engine and airframe had impacted the ground in a nearly vertical orientation. While the engine was still producing power at the time of impact, the elevator control chain was found to be disconnected. Specifically, the clevis (guignol) was intact, but the ball joint (rotule) had separated from it. Although the bolt intended to secure the assembly was present, it had failed to actually pass through the ball joint itself.
Technical analysis revealed that during recent maintenance, the mechanic had struggled to assemble the tight linkage. The bolt had been inserted through the clevis without fully traversing the ball joint, effectively only pinching the inner ring of the joint in place. This improper assembly allowed the joint to remain temporarily seated during low-load maneuvers, but it eventually slipped out under the high-stress, rapid nose-down inputs required by the aerobatic maneuver.
Findings
- The primary cause of the accident was an incorrect reassembly of the elevator control linkage.
- The error was undetectable during standard control surface deflection tests or pre-flight inspections.
- The mechanic lacked a specific maintenance manual or procedure for the complex, blind assembly of this specific component.
- Time pressure to return the aircraft to service following a heavy maintenance visit contributed to the error.
- The absence of a secondary inspection (cross-check) by a third party meant the faulty assembly went unnoticed through several test flights.