What happened
On September 9, 2014, an Air Loyauté Beech 200C Super King Air, registration F-GRSO, departed Lifou for Magenta as part of a non-medicalized medical evacuation mission. During the flight, the crew extended the landing gear and heard an abnormal metallic noise. They subsequently observed that the gear had failed to lock in the down position, as indicated by the absence of the three green indicator lights.
After attempting the emergency gear extension procedure without success, the crew decided to divert to Nouméa la Tontouta Airport to utilize better runway conditions for a precautionary landing. While flying over the airfield, air traffic control noted that the left main gear did not appear to be in a vertical position. The crew entered a holding pattern for approximately 45 minutes to reduce fuel weight and re-attempt the emergency extension procedure.
Upon touchdown on runway 11, the left main landing gear collapsed. The crew immediately feathered the propellers, shut down the engines, and cut the electrical power. The aircraft slid along the runway with the nose gear extended before coming to a stop. There were no fatalities or injuries among the crew and two passengers, though the aircraft was heavily damaged.
The investigation
The investigation focused on the mechanical operation of the main landing gear, which utilizes mechanical screw jacks for extension and retraction. Technical examinations of the landing gear actuators by the BEA laboratory revealed that two teeth on the pinion of the left main gear actuator had broken. This breakage was caused by fatigue cracks originating at the base of the teeth due to abnormal bending stresses.
Further analysis of the gears and pinions in both the left and right actuators showed similar damage patterns. The investigation also reviewed the maintenance history of the actuators, noting they had been replaced during a heavy maintenance phase in 2011 and had undergone a standard 1,000-cycle inspection in June 2013. No evidence of a previous hard landing was found in the maintenance records.