What happened
During a flight, the crew evaluated two potential landing locations, ultimately selecting a site previously used by an AW139. This site was chosen because it was closer to the mission location and had been successfully used by another company aircraft in the past.
Upon arrival, the crew performed a reconnaissance hover but did not perform an orbit of the landing area. The crew noted that they bypassed the orbit to avoid a nearby residential area and due to prevailing weather conditions. While the crew's procedures did not mandate an orbit, such a maneuver could have provided a better perspective on the terrain and obstacles. The landing site featured sloping ground that was near the operational limits for the aircraft type.
After a briefing in the hover, the crew began the approach to the landing area. Although the site met the operator's 10 ft obstacle clearance requirements, the crew recognized the area was tight and planned for small, controlled movements. During the maneuver, the aircraft experienced unintended yaw and drift. This movement was not detected by the crew and continued until the tail rotor made contact with foliage.
The investigation
The investigation focused on why the contact was not identified during the maneuver. The crew did not realize the tail rotor had struck the tree until the aircraft was shut down at a different landing site. Several factors may have contributed to this lack of detection, including the light nature of the foliage and the aircraft's active vibration control system, which may have dampened any vibrations resulting from the impact.
While the Aircrew Operator (ACO) suspected a strike might have occurred during the initial approach, there was no physical evidence of damage to the airframe. However, the investigation noted that had the ACO communicated their suspicion to the rest of the crew immediately, it could have prompted a more informed decision-making process regarding subsequent actions.