On 22 April 2019, a Eurocopter-Kawasaki BK-117C-1 helicopter (ZK-IMX) was being positioned VFR by Southern Lakes Helicopters from the operator’s Te Anau Heliport to the Auckland Islands for a planned medical evacuation of a fishing vessel crew member the following day. Although planned as a day flight, it was delayed and continued at night. As it neared the planned landing site on Enderby Island, it was unintentionally flown into the sea where, after briefly remaining partially submerged, it sank shortly after the three crew on board had escaped from it, one only with assistance from the other two.
The remote Southern Ocean location of the intended destination and the accident site. [Reproduced from the Official Report]
An Investigation into the accident was carried out by the Transport Accident Investigation Commission (TAIC). Relevant Recorded Data was available from a satellite-based flight following system accessible to the aircraft operator which provided the helicopter’s GPS position and height every minute. The last reported position was less than a minute before the accident and was the basis for the SAR response. The helicopter was also fitted with a Garmin 296 GPS and moving map display from which the memory chip provided the GPS flight track for the entire flight with a sample rate of between one and 20 seconds, including six points after the last known satellite transmitted position.
It was noted that the pilot had approximately 6,673 hours flying experience of which only 43 hours was night flying. His commercial pilot licence (CPL) was only valid for VFR and subject to a requirement to carry spectacles and a spare pair. In the three months prior to the accident, 43 of his total of 135 flying hours had been in BK117 aircraft. He had received initial Helicopter Underwater Escape Training (HUET) and training on the use of Night Vision Goggles (NVG) in 2013. Both the Paramedic and the Winch Operator had received training from the aircraft operator in Night Vision Imaging System (NVIS) use.
The flight departure was delayed but, once commenced, had proceeded normally, initially in daylight. However, by the time positioning for an approach to the intended landing site on Enderby Island had begun, it was night. The single pilot was accompanied by a paramedic who occupied the front left-hand seat and a winch operator who was seated in the cabin. The plan was that after landing, the crew would camp overnight on Enderby before conducting the medical evacuation of a seaman from a fishing vessel offshore the following day and returning to New Zealand.
All crew members carried NVGs and were familiar with their use. The crew found that “the hills and coastline around Port Ross and part of Enderby Island were visible
through NVGs but the pilot believed that the landing area was covered in cloud”. He therefore reported having devised an alternative approach to enable a descent below the cloud before following the coastline back to the landing area. The aircraft descended and was turning back towards the landing area when the paramedic in the left-hand front seat alerted the pilot to cliffs rising immediately ahead. The pilot reacted, but the helicopter hit the (flat calm) sea surface at speed and flipped upside down and immediately became partially submerged.
The pilot and the paramedic were able to escape unaided from the partly submerged helicopter but the winch operator in the rear cabin was knocked unconscious during the impact and was dragged from the helicopter by the paramedic. All three crew were wearing immersion suits which ensured they remained afloat and enabled them to make their way to shore which was about 100 metres away. The winch operator only regained consciousness during the swim to shore. Soon after the crew had evacuated, the helicopter sank. After sheltering under cover overnight, the crew were spotted the next day by one of the rescue helicopters sent to search for them and flown to Invercargill for a hospital check after which it was confirmed that all three had only suffered minor injuries.
The wreckage was subsequently located upside down in water about 15 metres deep and recovered (minus its tail boom and main rotors) three weeks later. Damage to the wreckage found impact forces and damage to the nose which confirmed that the helicopter had hit the sea surface at a shallow angle but at a speed that was consistent with the crew's accounts.
Why It Happened
The Investigation was able to confirm that the helicopter was operating normally at the time of the accident. It was found that “the pilot had misinterpreted the image seen through the NVGs as cloud covering the landing area when it was very likely to have been fog near the sea surface and downwind of the shore". The descent and approach was made using visual reference and the GPS map display but the rate of descent increased when the pilot, relying primarily on visual depth perception, formed the impression that the helicopter was further from the surface of the sea than it was. When the paramedic had seen an image through their NVGs and caused the pilot to initiate avoiding action, it was confirmed to have been 20-metre high cliffs several hundred metres ahead and rising above the height of the helicopter.
The Investigation found that despite similar flights being a regular feature of the operator’s flight programme, the procedures for such a potentially challenging flight were inadequate. It also identified gaps in the New Zealand Civil Aviation Regulations (CARs) in respect of minimum safety requirements for helicopters operating under Part 119 and Part 135 AOCs in respect of HEMS operations, the use of NVGs and the recording of such use and in delivering CRM in operations conducted with a single pilot accompanied by a non-pilot crew member.
The Findings of the Investigation were formally documented as follows:
- While the pilot was using the GPS map display for navigation and NVGs to help maintain visual reference, the helicopter unexpectedly impacted the sea in controlled flight when the pilot lost vertical reference.
- The winch operator’s left-hand seat belt snap-on steel bracket broke in overload where it attached to the seat base.
- The crew’s training and skill in helicopter underwater escape techniques, the wearing of flight helmets and full immersion suits and their survival skills were significant factors in their survival from this accident.
- No alert signal was received from the ELT at the NZ Rescue Coordination Centre.
- The pilot met the minimum recency requirement for NVG operations, but was likely deceived by a well-documented visual illusion with NVGs caused by a low contrast surface which is commonly experienced over calm water and can affect judgement of height and spatial orientation.
- The operator’s exposition for single-pilot VFR operations into the Southern Ocean was inadequate to manage the risks associated with such operations.
- The risk profile for the flight changed significantly with the delay in departure time. This should have initiated a thorough operational risk assessment for an NVIS flight operation.
- The New Zealand CAA risk controls that define the minimum safety requirements for Helicopter Air Ambulance and NVIS operations significantly lag behind other jurisdictions and are no longer fit for purpose.
- The aircraft radio altimeter was not required to be fitted with an aural alerting function which provides significant safety protection for pilots wearing NVGs.
- The potential for CRM to be an effective risk control with non-pilot NVIS crew members in a single-pilot, VFR, Part 135 operation is undermined by the current rules. CAR Part 135 does not set a clear expectation about the role and duties of a non-pilot NVIS crew member or define an appropriate level of CRM competence that could contribute to the safety of an NVIS flight.
- The CAA requirements for pilots to log flight time did not require a pilot to differentiate between night flight and night flight using NVGs which makes NVG recency experience difficult to assess.
- The helicopter departed for this flight in an overloaded condition, exceeding the maximum certified weight limit by almost 300 kg (approximately 9 per cent of maximum certified take-off weight).
- Although the helicopter and crew were provided with the appropriate emergency survival equipment and crew training for this operation, they were unable to locate some of this equipment, despite it being accessible. The only emergency survival equipment that was effective was what they had on their persons at the time of the accident.
Safety Action taken by Southern Lakes Helicopters whilst the Investigation was being carried our were noted to have included rectification of procedures for single pilot VFR operations into the Southern Ocean “including engaging an external auditor and introducing a new standard operating procedure for Sub Antarctic Island flights”.
Two Safety Recommendations were made as a result of the Findings of the Investigation as follows, on 7 March 2023 and 22 February respectively:
- that the Civil Aviation Authority of New Zealand address the growing gap between New Zealand’s minimum performance requirements and technical standards for NVIS and helicopter air ambulance operations and current international best practices. [021/22]
- that the Civil Aviation Authority of New Zealand address the safety issue created by the fact that CRM competency is not yet an effective safety measure for helicopters operating under CAR Part 135. [022/22]
The Key Lessons arising from the Investigation were recorded, in summary, as follows:
- The minimum requirement for NVG currency does not equate to proficiency.
- Helicopter underwater escape training (HUET) and immersion suits can increase survivability.
- If the operation needs crew to wear immersion suits, they should also carry essential emergency items on their person.
- All crew with flight-related duties need to be aware of the importance of radio altimeters when conducting NVIS operations and how to interpret the instrument and its alerts.
- Pilots should ensure their NVG flight time is separately logged.
- Overloading helicopters is a safety hazard.
- To be effective, emergency equipment such as a life-raft must also be accessible in an emergency and deployable for the crew to use.
The Final Report was approved for publication by the Commission on 7 March 2023 and published on 20 April 2023.