What happened
On July 11, 2008, a UH-1H helicopter, registration NA-518, operated by the National Airborne Service Corps, was conducting specialized search and rescue training near Hualien. After completing various training maneuvers, including rope descents and forest penetration, the aircraft was positioned near a levee by the Matauan Creek training area.
At approximately 09:33, the aircraft began a precision hovering training session. During the initial takeoff phase, while flying at an altitude of approximately 20 feet and an airspeed of 15 knots, the flight instructor observed a low engine RPM warning. Simultaneously, the 'RPM LIMIT' and 'Master Caution' lights illuminated. The instructor noted that the engine speed had dropped to 6,000 rpm and continued to decline rapidly. The helicopter descended quickly and struck the ground, bouncing approximately 5 meters along the levee before coming to a halt. There were 7 persons on board, including the flight instructor, the pilot, a crew chief, and search team members; all occupants survived the impact, though the aircraft sustained substantial structural damage.
The investigation
The Taiwan Transportation Safety Board (TTSB) conducted an investigation involving several agencies, including the National Airborne Service Corps, Asia Airways, the U.S. National Transportation Safety Board (NTSB), and Bell Helicopter. The investigation focused on the mechanical state of the engine, the pilot's emergency response, and the aircraft's structural integrity.
Investigators examined the engine's performance and the cockpit instrumentation. While there was no flight data recorder available to definitively link the RPM drop to specific pilot inputs, the investigation looked into mechanical, weather, and structural factors. The investigation also reviewed the training protocols and the presence of non-essential personnel during the flight.