What happened
On the night of 14 January 2003, a Kawasaki BK-117 helicopter, registration ZK-III, was performing an emergency medical transfer from Wellington Hospital to Masterton Hospital. The flight was conducted under visual flight rules (VFR) to transport a patient and medical staff.
During the flight, the pilot inadvertently overflew a waypoint, moving toward higher terrain. As the aircraft entered cloud cover, the pilot initiated an emergency climb to maintain altitude. During this maneuver, the helicopter struck treetops in the Tararua Range near Mount Tauherenikau. Despite the impact, the aircraft remained controllable. The pilot sustained a serious hand injury due to debris entering the cabin, while the other occupants were uninjured. The crew managed to navigate the damaged aircraft to Masterton Aerodrome, where they performed a successful emergency landing using a bed of old tires to protect the damaged landing gear.
The investigation
TAIC investigators examined the flight path, the aircraft's mechanical state, and the pilot's navigation methods. The investigation focused on the transition from visual navigation to instrument meteorological conditions (IMC) and the lack of specific operational guidance for night VFR flights. Investigators reviewed the GPS data, which showed the aircraft had overflown the intended waypoint by approximately 0.4 nautical miles before the pilot attempted to correct the course.
Findings
- The flight was being conducted on a route not typically used at night.
- The altitude maintained during the night VFR flight provided insufficient safety margins above the terrain.
- A navigational error led to the aircraft entering cloud cover, necessitating the emergency climb.
- The operator lacked specific guidance material in its manuals regarding practical procedures for night VFR operations.
- The pilot's rapid reaction to the radio altimeter alarm and the subsequent emergency landing were critical in preventing a much more severe accident.