What happened
On 11 December 2006, a Kawasaki-Hughes 369HS helicopter, registered ZK-HDJ, was performing a commercial transport operation near Mount Ruapehu. After completing a day of weed control tasks for the Department of Conservation, the pilot agreed to pick up two additional passengers from the edge of Crater Lake.
The aircraft was heavily loaded with five people on board, including the pilot, a crewman, and three passengers, along with various gear. During the departure from the lake's edge at an elevation of approximately 8,330 feet, the pilot found the aircraft unable to climb above the surrounding terrain. In an attempt to gain airspeed and reach the best-angle-of-climb speed, the pilot descended toward the lake. This maneuver resulted in the helicopter striking the water surface before coming to rest on the shore. The impact destroyed the aircraft and caused three serious and two minor injuries among the occupants.
The investigation
The investigation examined the aircraft's performance, the pilot's decision-making, and the physical configuration of the cabin. Investigators noted that the pilot had previously removed the cabin doors and several seat cushions to facilitate rapid passenger loading and unloading during the day's earlier tasks.
Analysis focused on the weight and balance of the aircraft, as the pilot had not formally calculated the total weight of the passengers and their equipment. The investigation also looked into the pilot's experience with mountain flying and the specific challenges of operating at high density altitudes, where engine and rotor performance are significantly reduced.
Findings
Several contributing factors led to the accident:
- The pilot failed to accurately assess the total weight of the passengers and their gear, leading to an overloaded or critically high-weight condition.
- There was a lack of adequate planning for the specific requirements of the mountain flight task.
- The aircraft's configuration was unsafe, as the removal of seats and doors, combined with the fact that some passengers were not secured by seat belts, increased the risk to occupants.
- The pilot's attempt to use a descent to gain airspeed in a high-altitude, high-weight scenario resulted in the loss of terrain clearance.
Safety action
The investigation identified several critical safety issues requiring attention:
- The necessity for improved training and supervision for pilots operating in complex mountainous terrain.
- The dangers associated with removing seats and neglecting the use of seat belts in helicopters.
- The importance of carrying life jackets during flights where water landings are a foreseeable risk.
- The need for more effective regulatory oversight to ensure industry compliance with safety standards.