about the technology underlying NVG, which multiplies available light, particularly infrared light not otherwise visible to the human eye, but do not create ambient lighting that doesn’t exist otherwise. On the night of the accident, the moon was below the horizon and celestial illumina- tion was minimal. Limitations on contrast resolution are particularly acute over fea- tureless surfaces such as large bodies of calm water. The available light the night of the accident, as estimated by the UK Meteorological Office on request from the TAIC, was one one- thousandth that of a full moon. Interviews with the crew along with
The accident aircraft, a 1996-model Kawasaki BK 117 C-1. (TAIC / Southern Lakes Helicopters)
The helicopter flipped over and began to fill with water. The pilot and paramedic escaped underwater, and the paramedic rescued the winch operator, who was knocked unconscious. The sea was “dead calm.” The paramedic tried to retrieve the life raft and the survival supplies packed in the aircraft’s emergency bag but couldn’t find them in the dark before the helicopter sank. The winch operator regained consciousness. The crew’s immersion suits provided enough buoyancy to enable them to pad- dle 100 m to shore, where they climbed through a kelp bed onto the rocks. They took shelter in the bush but, without the personal locator beacons and other gear lost in the emergency bag, were unable to attract the attention of a P-3 Orion airplane that passed overhead or vessels they could see offshore.
The Rescue The operator’s chief pilot saw that the flight-tracking signals had stopped updat- ing and tried to reach the crew by satellite phone. After confirming that the satellite tracking had not malfunctioned, the chief pilot contacted the Rescue Coordination Centre New Zealand (RCCNZ) at 8:08 pm, 25 minutes after the accident. The RCCNZ in turn arranged for a Royal New Zealand Air Force P-3 Orion to initiate a visual
86 ROTOR MARCH 2024
search and asked five fishing vessels in the vicinity to assist. The P-3 took off at 10:51 pm and
arrived on the scene the next morning about 1:20 am, but low cloud cover pre- vented its crew from conducting a low-al- titude search, so they dropped flares and attempted an infrared search for warm bodies. The first fishing vessel arrived in the area at 11:23 pm. One of the fishing boats diverted to Bluff with the patient who’d suffered the initial emergency. The other vessels established a search grid that located the helicopter’s left sliding door. Three rescue helicopters launched at 10:15 am the next day and reached the scene in 27 minutes, where they spotted the aircrew’s brightly colored immersion suits and evacuated them to the hospital in Invercargill.
The Investigation Eighteen days after the accident, a private contractor retrieved the main wreckage from the sea floor. The tail boom had sep- arated and drifted away and was not found. Examination confirmed that the helicopter was functioning normally at the moment of impact. The pattern of damage to the fuselage and main-rotor hub informed the TAIC’s reconstruction of the angle and velocity of impact. The TAIC report goes into some detail
GPS tracking data from both the satellite link and an onboard unit provided more detail into the flight’s final moments. As the helicopter descended, the paramedic began providing altitude callouts that were neither expected nor requested by the pilot—instead they were based on the barometric altimeter, which the pilot had not reset for local atmospheric pressure since leaving Invercargill. The difference resulted in readings about 50 ft. higher than given by the radio altimeter, which was not easily seen from the left seat. The pilot set the radio altimeter for progres- sive descents but did not monitor its alert light as he scanned for surface refer- ences; the altimeter did not give audible alarms. Though their employer’s operating specifications called for a maximum descent of 300 ft. per minute (fpm) on NVG, an initial descent rate of 500 fpm increased to 1,200 fpm as the pilot tried to drop down into what he thought was a clear area. The paramedic, who had no training in aviation instrumentation or phraseology, warned the pilot to check his “speed” rather than “descent rate,” which the pilot interpreted as “airspeed.” The cliffs they saw at the last minute were only 20 m (66 ft.) high, and the pilot recalled being “surprised” that the heli- copter was so much lower than expected. TAIC investigators took pains to note the latitude provided by regulations
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