What happened
On May 20, 2023, a Robin DR 400/180 R, registration HB-EQD, departed from Les Eplatures airport for a scheduled discovery flight. The aircraft was carrying a pilot and two passengers. After an initial climb and transit toward the Brenets area, the aircraft's flight path became erratic. Witnesses on the ground observed the aircraft performing maneuvers resembling aerobatics, including a downward loop, before entering a descending spiral. The aircraft subsequently struck a steep, wooded slope in the Les Combes-Dernier area. The impact resulted in three fatalities and the total destruction of the aircraft.
The investigation
Investigators from the SUST examined the wreckage and identified critical failures in the aircraft's nose gear assembly. The examination revealed that the main nut for the nose gear pivot was missing, and its associated locking screw was also absent. Furthermore, the driving screw intended to hold the pivot in its normal position was missing, which allowed the pivot to disengage from its seat. Additionally, the investigators found that a castle nut securing a rudder control linkage on the pilot-side pedal was missing, and the associated threaded stud was damaged and bent.
Findings
Technical analysis established that the collision with the terrain was the direct result of a loss of control caused by a rudder pedal jam. This jam occurred because the nose gear pivot disengaged from its mounting due to the absence of the primary retaining nut and driving screw. Contributing factors included the inherent design of first-generation pivots, which allowed for downward movement when the main nut was absent, and the detachment of the rudder control linkage due to a missing castle nut.
Safety action
Following the investigation, the SUST issued safety recommendations directed at EASA and the manufacturer. The agency recommended that EASA, in collaboration with the manufacturer, establish measures to prevent the loosening of control linkage fasteners on the Robin DR 400/180 R model. Additionally, a recommendation was made for EASA to systematically apply Continued Airworthiness Review Item (CARI) procedures regarding fastening methods for aircraft with older type certifications.