Incident Description
During the landing roll, the aircraft began to vibrate and then rotated to the left. The instructor pilot shut down the engine. Subsequently, the right landing gear collapsed. Prior to landing, the pilot and instructor had visually checked that the landing gear was down.
Examination Findings
Post-incident examination revealed that the main gear actuator piston for the left main landing gear was broken. The fracture surface exhibited beach marks characteristic of fatigue crack growth. Further analysis indicated that the fracture outside the fatigue region resulted from a single-event overload, not from the fatigue crack itself. The extent of damage prevented a determination of when the actuator piston had initially broken.
Maintenance Records
Review of the aircraft logbook showed that the main landing gear actuator piston had accumulated 1,530.2 hours since installation. No other anomalies were noted during the on-scene examination of the aircraft.