Two trapped near Tarn Ridge
At 2:29pm on Sunday 12 November 2023, the Maritime NZ Rescue Coordination Centre received an alert from a personal locator beacon in the Tararua Range, near Wellington. Enquiries established the party was a group of two, on a multi-day “Northern Crossing” tramp from Levin to Masterton.
The beacon’s GPS position indicated the party were in a steep gully, approximately 500 metres east of Tarn Ridge Hut. Winds of 80-100 kilometres per hour battered the range and light rain fell from the thick layer of cloud obscuring the tops. The missing party’s exposed position combined with the severe weather would prove extremely challenging for both airborne and land-based rescuers. Over the next 29 hours, multiple agencies worked together to safely bring the two trampers home.
The following timeline is drawn from the Maritime NZ Rescue Coordination Centre (RCCNZ) mission log.
Sunday 12 November
2:31pm
Using the beacon’s registration information, RCCNZ unsuccessfully attempts to phone the beacon owner. Next, they phone the listed emergency contact, who shares the group’s intentions.
2:39pm
RCCNZ calls Masterton-based operator Amalgamated Helicopters. They are unavailable for the task and say the wind on the mountain tops is “probably over 100 km/h at present.”
2:45pm
The Grassroots Trust Rescue Helicopter (operated by Search and Rescue Services Ltd - Palmerston North) is contacted with the situation and weather information. They conduct a risk analysis then accept the task with a BK117 Helicopter.
2:46pm
Police are contacted and the Wellington Police SAR coordinator is informed. The coordinator contacts Land Search and Rescue groups in the region to check for volunteer availability.
3:30pm
The BK117 pilot reports that clouds are preventing them from reaching the beacon location from the Levin side. They fly north to look for a clearance, to attempt access from the east side of the range.The cloud wouldn’t rule out the deployment of field teams at lower elevations in the vicinity of the beacon location. However, severe winds and associated downdrafts could prevent that deployment.
4:45pm
RCCNZ contacts Headquarters Joint Forces New Zealand and discusses the use of an Air Force NH90 Helicopter. A formal request and approval process follows to task the helicopter.
4:46pm
MetService provides a detailed Search and Rescue Forecast for the Tararua Forest Park. “Today, patches of drizzle are developing. Winds at ridgetop level are forecast to increase to 95 kilometres per hour by midnight, with ambient air temperatures dropping to 4 degrees Celsius. The outlook for the next few days is poor.”
5:34pm
Wellington Police SAR coordinator confirms a field team of four volunteers from Wairarapa plus one reserve. Also, three volunteers on standby in Wellington. RCCNZ discusses three possible plans: A: deploy as close to beacon position as possible. B: deploy close to Tarn Ridge Hut, walk to hut and reassess. C: deploy to Mitre Flats Hut, then fly or walk to beacon position the next morning. Amateur Radio Emergency Communications volunteers are deployed to support field communications.
7:11pm
Wairarapa field team has been briefed and is ready for deployment from the Masterton Aerodrome.
7:17pm
NH90 Helicopter departs Ohakea and attempts unsuccessfully to reach the beacon location. They uplift the Wairarapa field team from Masterton Aerodrome but are unable to get close enough to the tops. They deploy the field team to Arete Forks Hut, which is closer to the beacon location than Mitre Flats Hut.
8:34pm
Field team intends to get some rest before departing at 5am. They plan to ascend an unmarked track up to spot height 1478m, before heading southwest along Table Ridge, then dropping down to the beacon location, arriving around 9am. If the missing party can move, they will escort them to Tarn Ridge Hut and wait.
8:52pm
RCCNZ checks in again with the missing party's family, keeping them updated with progress of the operation. This is one of many check-ins conducted over the course of the operation.
Monday 13 November
08:15am
The field team has reached the ridge, but are struggling to make progress in severe wind, low visibility and rain. They retreat to Arete Forks Hut for their own safety and prepare to approach the beacon location via the Waingawa River. RCCNZ and Police spend the rest of the morning discussing the options. There are field teams available from Levin and Wellington, which could approach from different valley systems. Weather is continually reassessed, with advice from the Masterton SAR Base, reports from the field team, local helicopter operators and MetService.
12:24pm
The Levin field team is assembled with the intention of deploying via NH90 helicopter to Tarn Ridge Hut, or nearby in the upper Waiohine Valley.
12:42pm
Sergeant Tony Matheson is appointed On Scene Coordinator. He coordinates field teams from Masterton Aerodrome, whilst RCCNZ continues to coordinate helicopter assets.
1:03pm
After a request from RCCNZ, the Grassroots Trust Rescue Helicopter makes another attempt to access the beacon, but the conditions prevent them from reaching that location.
2:21pm
A position report from the beacon indicates the lost party is moving towards the Wairarapa field team in the Waingawa Valley. The field team switches on their radio direction finding equipment.
4:35pm
The field team begins to receive the beacon’s 121.5MHz homing signal.
5:35pm
Voice contact is made with the missing party, who are beside a creek but separated from the field team by a waterfall. By 5:49pm searchers reach the two trampers, who are uninjured, but cold, wet and very tired. The weather has improved slightly, and the field team reports they are about 200 metres below the cloud base.
6:38pm
The NH90 Helicopter reaches the missing party and field team. All six people are extracted via a challenging winch recovery and then returned to the Levin showgrounds, where the operation concludes.
Insights:
Responder safety was paramount. Throughout the operation, responders showed a willingness to endure very difficult weather conditions, but before the situation exceeded safe limits, they retreated and alternative plans were made.
Operational flexibility was maintained. Several courses of action were developed by incident managers and team leaders, contingent on weather and resource constraints. When opportunities such as breaks in the weather presented themselves, helicopter assets were able to deploy teams closer to the beacon location, and eventually the missing party.
Weather was assessed continuously and comprehensively. The weather was the key factor affecting the rescue. Incident managers took advice from the Masterton SAR Base, reports from the field team, local helicopter operators and specifically generated forecasts from MetService to look for opportunities in the weather situation.
Helicopters are constrained by clouds and adverse winds. To reach a position where people can be transferred between the helicopter and the ground, the crew must be able to see the terrain. Cloud or heavy precipitation reduces visibility to nearly zero. In the lee of terrain, strong winds can create turbulence and severe downdrafts. These air movements can impact control of the helicopter to a point where it is not safe to continue.
Close coordination is required for complex rescues. This SAR operation demonstrated the value of collaboration between coordinating authorities. Local coordination of search efforts through the New Zealand Police with the support of RCCNZ in planning, provision, and tasking of assets (such as aviation) positively impacted the outcome of this operation.
Feature image: Land Search and Rescue field team boards the NH90 Helicopter during the operation. Courtesy Land Search and Rescue.
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This story was originally published in the September 2024 issue of Link magazine, which is produced by the NZSAR Secretariat for the wider search and rescue sector.