Flightcell DZMx instrumental in New Zealand helicopter accident investigation

In September 2023, a Kawasaki BK117 B-2 air ambulance crashed into dense native forest on New Zealand’s North Island during a mission to rescue an injured hiker on Mount Pirongia. Miraculously, the pilot and crew escaped unharmed.

Dispatched from Hamilton Airport late in the afternoon, the helicopter was conducting a winch recovery due to the region’s rugged terrain when it suddenly lost altitude while descending on the windward side of a ridge. Investigators from New Zealand’s Transport Accident Investigation Commission (TAIC) concluded there was a greater than 99% probability the aircraft entered vortex ring state (VRS) – a dangerous aerodynamic condition that can cause a rapid and uncontrollable descent due to loss of rotor lift.

The helicopter’s altitude at the onset of VRS – 291ft above ground – left insufficient time for recovery, resulting in a hard impact with the forested terrain.

Flight data from the onboard Flightcell DZMx system, a voice, tracking, and data unit compliant with the Federal Aviation Adminstration’s regulation 135.607 requirements, proved critical in the investigation. The unit recorded flight parameters, including trajectory, pitch, descent rate, and GPS position, at one-second intervals. This data enabled Flightcell to reconstruct the aircraft’s flight path and identify the exact moment VRS was triggered at 17:06:55.

TAIC has issued several safety recommendations, including that Kawasaki revise the BK117 B-2 flight manual to include specific guidance on VRS, and that New Zealand’s Civil Aviation Authority promote the adoption of VRS alerting systems and enhanced pilot guidance through the International Civil Aviation Organization (ICAO).

The incident underscores both the risks of complex rescues in mountainous terrain and the value of flight data monitoring in enhancing safety and understanding accidents.

Flightcell recently launched Flightcell Controller, a new compact and intuitive interface to control the Flightcell DZMx PLUS.