WEEK 28
H2F brings you the ‘helicopter mayday of the week’ with a short accident report summary. I tell you what happened. You think more about why it happened. We all learn from it. Because that’s what accident reporting is for.
TITLE
Controlled flight into the sea during a dark-night NVIS medevac.
WHAT?
A BK117 departed New Zealand to pre position to a remote island for a medevac the next morning. Unexpected delays meant the 478km VFR positioning flight arrived after dark using NVIS for the arrival. During a descent intended to position below cloud, the helicopter struck the sea.
WHERE?
Close to New Zealand’s sub-Antarctic Auckland Islands.
WHEN?
22 April 2019. The flight had been planned to arrive in daylight, but departure delays resulted in arrival after dark. Final Report published 20 April 2023.
HOW?
On arrival, the pilot planned to descend through an area he believed clear of cloud and then follow the coastline back toward the landing site. During the descent, he relied principally on external visual depth perception supplemented by the GPS map display. The helicopter descended faster than the pilot perceived and he only initiated avoiding action from the surface when the paramedic saw cliffs immediately ahead and issued a warning just before helicopter struck the sea.
CONDITIONS?
The crew were operating in an exceptionally demanding visual environment. The islands are remote and uninhabited, with no artificial lighting to provide references at night. The moon had not risen, and predicted natural illumination was at its lowest level of the night, further limited by cloud and atmospheric conditions.
Fog was probably present close to the sea surface and downwind of the shore. Through the NVIS the pilot possibly misinterpreted this as cloud covering the landing area. The featureless, low-contrast sea provided poor depth and height cues creating a visual illusion.
OUTCOME?
The helicopter struck the water at speed and inverted. Pilot and paramedic escaped, but the winch operator was knocked unconscious and was pulled from the submerged cabin by the paramedic. All three wore immersion suits and swam approximately 100 m to shore, where they sheltered overnight before rescue the following day.
HUET training, helmets, immersion suits and survival skills were found to be significant factors in their survival. However, emergency beacons and survival equipment had been stored in a grab-bag that sank with the helicopter, and the life-raft could not be identified and retrieved in the darkness.
WHY?
The investigation determined that the pilot lost vertical reference and flew the helicopter into the sea. It also identified several interacting human, operational and systemic factors:
The delayed departure converted a planned daylight arrival into a dark-night NVIS operation in an exceptionally remote, low-illumination environment.
The pilot was probably deceived by a well-documented NVIS visual illusion associated with low-contrast surfaces, misinterpreting the visual scene and believing the aircraft was higher above the sea than it actually was.
Although the pilot met minimum NVIS currency requirements, investigators emphasised that currency did not necessarily equate to proficiency.
The operator’s procedures for single-pilot VFR operations in the Southern Ocean were inadequate for managing the associated risks.
Training concerns were raised about CRM for non-pilot crew supporting single pilots, including understanding and monitoring the radio altimeter.
Significant regulatory gaps existed in New Zealand’s requirements covering helicopter air ambulance operations, NVIS operations, CRM for single-pilot/non-pilot crew combinations, and recording NVIS flight experience.
REFERENCE?
Transport Accident Investigation Commission. (2023). BK117-C1, ZK-IMX, controlled flight into terrain (water), Auckland Islands, 22 April 2019 (Final Report AO-2019-005). Transport Accident Investigation Commission.
Note:
Accident reports selected from the following open source databases: US NTSB; UK AAIB; Flight Safety Foundation’s Aviation Safety Network; Australia’s ATSB. Ireland’s AAIU; Taiwan’s TTSB; France’s BEA; Spain’s CIAIAC. Germany’s BFU.
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