What happened
During an approach to the Tai Keystone, a helicopter experienced a tail rotor strike while attempting to land on the vessel's helicopter landing site (HLS). While the pilot was aware of certain hatch cover obstacles and positioned the aircraft to avoid them, this maneuver resulted in the aircraft being positioned over the 'H' rather than the designated yellow touchdown circle. Consequently, the tail rotor moved into the obstacle-sensitive sector, where it made contact with a port-side handrail that had not been removed.
The investigation
The investigation focused on why the handrail remained on the landing site and why it was not detected by the pilot. It was determined that the vessel's crew was utilizing an outdated version of the International Chamber of Shipping Guide to Helicopter/Ship Operations checklist. This specific version lacked a dedicated requirement to check for or remove handrails and stanchions. While the marine pilot had identified handrails and instructed the crew to remove them, the port-side rails remained in place.
Furthermore, the visibility of the obstacle was compromised. The handrails were painted yellow, which matched the surrounding permanent ladder and other vessel fittings, making them difficult to distinguish against the green HLS surface. The investigation also noted that the pilot's reconnaissance at 300 feet was likely insufficient to identify the rails due to their size, shape, and lack of color contrast.
Findings
- The port-side handrails were not removed prior to the helicopter's arrival.
- The pilot's positioning of the aircraft placed the tail rotor outside the obstacle-free sector.
- The crew used an outdated checklist that did not include a specific check for handrails.
- The yellow color of the handrails made them difficult to detect against the landing site environment.
- Regulatory guidance from the Civil Aviation Safety Authority (AC 139) lacked specific instructions regarding the marking of objects within the HLS clear zone.