Staying put

ACR ResQLink

I’ve finally bought myself a Personal Locator Beacon (PLB; an ACR ResQLink in my case), which I obviously hope I’ll never need to use. I was on the edge of buying one a couple of years ago, but put it off for a while when things changed. It arrived in the mail a few days ago.

Several SAR incidents were making the news on the day that my PLB turned up. One of these occurred in the southern Ruahine Range. In this most actively-reported case, a PLB was activated by a tramping club group which had taken a wrong turn in bad weather.

In the Pohangina vicinity (here’s a map) they’d planned (according to the club’s trip schedule) to head up Shorts Track, follow the tops over .1380, .1405, .1350 and down to Ngamoko Hut, before eventually returning somehow via Toka Trig and down Knights Track. A navigation error in bad weather on the first day, however, in the vicinity of Whaingapuna (.1405), resulted in the group ending up in Piripiri Stream. They changed plans to attempt to follow it out to farmland, but found themselves bluffed by a very high waterfall.

Contour lines on topo maps can sometimes be deceptive. Without further info I’m curious if they followed the stream down a gradual (but possibly tough) descent for a several kilometres, before it surprised them by dropping more steeply into a waterfall. Being the Ruahines, with thick alpine vegetation such as Leatherwood being common at certain elevations, an un-planned detour could easily turn into a demoralising, waterlogged nightmare without an easy escape. If anyone has clearer detail on how and where the party actually came to be stuck, it’d be awesome.

Having waited out the first freezing night, the group decided to activate their PLB, but still needed to wait for that entire day, a second freezing night, and further into the following morning before help could arrive. In its weekly incident report, the RCCNZ (initially handling the response) reported:

A helicopter was tasked by RCCNZ from Palmerston North, but could not locate the trampers due to low cloud. The beacon was also transmitting positions over a wide area. No GPS position was received from the beacon despite it being a GPS-enabled beacon. A second attempt to send in helicopters and ground teams was delayed by an extreme weather event hitting the area and then darkness fell. Land SAR teams were deployed and the decision was made to transfer the incident to the Police as a Category 1 incident as they had better communications with the search teams.

Contrary to the stereotype helicopter-zip-in-zip-out easy-to-document-by-film-crew PLB rescues that have been recently portrayed in oblique 22-minute episodes of High Country Rescue, this incident involved a significant search component despite the use of a PLB, and despite that PLB having been designed to be GPS-equipped.

An interesting perspective to read on this operation is that of the Palmerston North LandSAR group (via Facebook). It details more about the two Air-Force Iroquois (limited by weather), working with several LandSAR teams who, in the absence of being able to exactly locate or reach the source of the PLB transmission, walked into the range regardless:

“The weather was still horrendous; very heavy rain, hail and strong winds. The team considered the weather but graciously accepted the task to walk in to check out the identified destination hut. They had hand-held DF [Direction-Finding] gear and were getting intermittent hits from the beacon. They got as far as the tops by late evening and decided to camp there for the night.”

Today’s 406 MHz PLBs can be GPS equipped to transmit an exact position, though some less expensive models don’t have that functionality, and merely transmit an emergency signal with identity information to satellites overhead. If a position isn’t transmitted, either because the GPS equipment is inhibited or because it’s non-existent, it’s generally possible for the satellites to triangulate an approximate position after several hours of listening, but only to within a circle of about several kilometres. It could possibly be worse in situations such as this where the signal was bouncing around, and that type of region can still be daunting to search if the geography and conditions are unforgiving.

Modern PLBs also transmit on 121.5 MHz in parallel, and search aircraft usually carry equipment to be able to accurately home in on signals as they fly overhead. This can still be hindered, however, if aircraft are unavailable or unable to fly. The PLB involved was designed to transmit position information and it’s unclear why this didn’t occur, but having the subjects stuck in a deep ravine may have prevented the device from obtaining a fix on the necessary satellites. Having its transmission bouncing off the sides of that ravine also complicated matters for the available and slow-moving ground-based direction-finding equipment, whilst it anecdotally appears that bouncing signals were the cause for different satellites to place the party at varying locations up to 7 km apart.

I think this is a great example to demonstrate at least a couple of important things which have always been generally good advice where PLBs are involved:

  • carrying a PLB is definitely no excuse to shirk on emergency survival preparations, including portable shelter, as it can still take time for help to arrive, and
  • after making the decision to activate a PLB, it’s critical to avoid moving from that position unless absolutely necessary, even if it’s tempting to do so to continue to try and find a way out.

In both of these respects, the group certainly did the right thing after the PLB was activated. They were equipped to stay put, potentially for several more days (according to their claim). If they had decided after several hours, or after a day, to try and climb around the waterfall or return the way they came, it would have largely hindered the efforts of those around them to slowly home in on and reach the signal.

Activating a PLB is a serious decision that can’t be undone, and should never be taken lightly. It causes a request for help to be relayed to rescue authorities in up to two places—the country in which the PLB is registered, and the country responsible for the location in which the PLB has been activated. In New Zealand, this authority is the Rescue Coordination Centre of New Zealand (RCCNZ), a division of Maritime New Zealand of which I’ve been critical in the past for how it communicates, but which I could also not fault for its efficiency or professionalism in responding to rescue requests.

Upon activating a PLB, a chain of events is started that won’t stop until rescue officials are satisfied that no further action is necessary. Even if it takes time for a response team to reach the source location, moving away from that area will nearly always confuse matters, slow things down and put everyone involved at higher risk than they need to be.

This entry was posted in musing and tagged , , , , , , . Bookmark the permalink.