Incident Overview
During a landing, the aircraft's landing gear extended but did not lock into position. The flight crew attempted to resolve the situation by following both normal and emergency gear extension procedures, but these efforts were unsuccessful. Upon touchdown, the landing gear collapsed.
Investigation Findings
A post-incident investigation revealed that a fatigue crack had developed in the hydraulic actuator of the right main landing gear. This crack allowed hydraulic fluid to escape, which prevented the actuator from functioning correctly and thus the gear from locking. The loss of hydraulic fluid was identified as the direct mechanical reason for the gear's failure to lock.
Maintenance Background
According to maintenance records provided by the operator, the hydraulic actuators had been inspected for leaks and alignment approximately 28 flight hours prior to the incident. The inspection did not detect the fatigue crack or any other anomaly at that time.