What happened
The incident occurred while the aircraft was conducting an external load operation. The pilot was attempting to land the helicopter after completing a lift with an external cargo sling. As the aircraft descended, the long line connecting the helicopter to the load became entangled in nearby tree branches.
This entanglement caused the long line to wrap around the tail rotor assembly. The mechanical interference prevented the tail rotor from functioning correctly, leading to a loss of directional control and a subsequent hard landing. Upon impact with the ground, the aircraft sustained substantial damage to its rear structure.
The investigation
Post-accident examination revealed that the primary failure mode was mechanical entanglement rather than system malfunction. The long line had wrapped around the tail rotor blades and hub. This physical obstruction caused immediate damage to the tail rotor assembly. Additionally, the force of the hard landing resulted in damage to the tail boom and the tail gear box. No evidence of pre-existing mechanical failure was found prior to the entanglement event.
Findings
The investigation determined that the sequence of events began with the long line snagging on vegetation. This action pulled the line into the rotating tail rotor system. The resulting damage compromised the helicopter's ability to maintain heading during the final phase of flight. The pilot reported a hard landing, which was consistent with the observed structural damage. The external load operation required precise spatial awareness to avoid overhead obstacles.
Safety message
Pilots conducting external load operations must remain vigilant for potential entanglement hazards. Long lines can easily snag on trees, power lines, or other structures during low-level flight and landing phases. Maintaining situational awareness of the load path relative to surrounding terrain is critical to preventing similar incidents.