What happened
In the Kamarang area of Guyana, a Eurocopter AS 350 B2 helicopter, registered C-GNMJ, was performing routine mining support operations. At approximately 1725 local time, the pilot attempted to coil a 120-foot longline while maintaining a stable hover. As the aircraft descended to roughly 10 feet above the ground, the pilot encountered significant binding in the flight controls.
During this period of uncontrolled flight, the pilot struggled to maintain the aircraft's attitude and altitude. The helicopter experienced erratic movements in pitch, roll, and yaw. In an attempt to manage the situation, the pilot reduced the throttle, which caused a rapid decay in main rotor RPM. The helicopter subsequently descended quickly and struck the ground, bouncing before coming to rest. The impact caused substantial damage to the skids, tail boom, and main rotor head, though the pilot escaped without injury.
The investigation
The investigation focused on the sudden onset of control restrictions and the potential for hydraulic system malfunction. Investigators examined the flight control components, specifically the servo actuators and accumulators. Laboratory testing revealed several physical anomalies in the hydraulic components:
- The lateral servo actuators exhibited inconsistent travel rates, with extension speeds significantly faster than retraction speeds.
- High internal fluid leakage was identified in the left and forward servos.
- The left lateral servo accumulator depleted its pressure 1.7 times faster than the right lateral servo accumulator.
Additionally, the investigation looked into the possibility of electrical anomalies affecting the hydraulic system's functionality and evaluated the pilot's ability to manage the transition from hydraulic-assisted to manual flight controls.