Background
The airplane, originally equipped with tricycle landing gear, was modified to a conventional tailwheel configuration under a Supplemental Type Certificate (STC). The conversion involved changes to the aircraft's control systems and landing gear structure.
Accident Sequence
During the landing rollout, the airplane began to turn to the left. The pilot and an instructor onboard attempted to correct the turn, but their efforts were unsuccessful. The airplane subsequently departed the runway and groundlooped.
Investigation Findings
An investigation into the incident revealed that the right rudder cable bellcrank torque tube had failed. Further examination determined that the rudder pedal assembly and the broken part did not conform to the design specified in the STC. The non-conforming components were found to be associated with the failure of the torque tube, which likely contributed to the inability to control the directional deviation during the landing rollout.