What happened
On 30 November 2003, a Hughes 369HS helicopter, registration ZK-HCC, was conducting a scenic flight near the head of Fox Glacier. While cruising at approximately 9,500 feet, the pilot noticed a sudden drop in engine power turbine speed and rotor speed. In an attempt to stabilize the aircraft, the pilot lowered the collective lever, which temporarily restored power as the aircraft descended to 6,500 feet.
However, the power loss recurred several minutes later. Faced with a continuing decay in engine performance, the pilot initiated an emergency landing at the base of the glacier. During the landing maneuver, the helicopter's right rear skid struck a large rock, causing the skid to break and the aircraft to roll onto its right side. While 4 passengers sustained minor injuries, no one was seriously harmed.
The investigation
Investigators examined the engine and the electrical components of the collective lever. They discovered that the securing nut under the "beep switch"—an electrical switch used to set the power turbine governor—had loosened. This instability allowed the switch to move excessively during normal operation, which eventually caused the electrical wire terminals to break.
This loss of electrical continuity triggered a power turbine governor underspeed condition, effectively forcing the engine to its minimum power setting. The investigation also noted that the pilot had relatively limited experience with turbine-engine helicopters, which may have impacted the speed of the diagnostic process during the in-flight emergency.