Probes revisited: Is the avalanche probe still essential?

Abstract

The avalanche probe is an inseparable part of your rescue kit, according to AAIRE. Historically probing was the only means to locate a burial. Is it still always necessary to carry one? Rather than make a binary decision to carry a monolithic kit, we propose the snow climber picks gear based on risk, but always carries a subset. Unlinking probes from the kit may improve overall safety.

Background

Originally burials were probed with wood wands or poles, but rescuers came to carry dedicated probes of jointed aluminum alloy tubing, starting around 1970.

Burials were coarsely located via debris, hounds or trailing red thread from the victim. Then rescuers pinpointed the victim with a laborious line or grid, using their probe.

When avalanche beacons were introduced, spot probing was still required. These analog beacons could only be located manually, by listening to amplitude and estimating distance. Beacons also remained rare, making the probeline an important option. 

Digital beacons increased user guidance and accuracy of search. Electronics improved with a crystal oscillator, so frequency no longer drifted over time. Transmissions were bumped from low frequency (2.2kHz) to medium frequency (457kHz), shrinking flux lines and streamlining the search pattern. The beacon could even detect overlap, potentially filtering multiple burials. Beacons still struggled to pinpoint a burial consistently though, due to natural distortion of the signal amplitude, especially under deep snow. The probe remained necessary for spot probing.

Next, digital beacons were upgraded with extra reception antennas, interpreting distance with 2x higher accuracy. After careful bisection, rescuers can now usually reach the burial with their first probe strike. Even in the worst-case nullity scenario (distant beacon oriented vertically) 3-antenna beacons can now resolve competing maximums. Some beacons now use their extra antennae for transmission as well (selective orientation), so even rescuers with obsolete mono-antenna receivers can excel in this worst-case scenario.

As these improvements were made, avalanche gear has shrunk in weight and bulk. Beacons have lightened from ~300g to 150g. Aluminum shovels appeared in better alloy grades, allowing a lighter design in the 600g range, including 7075 models at only 400g. The probe, formerly the lightest and least bulky member of the kit, (~300g) now begins to feel more significant.

Analysis

The fast and light climber takes a hard look at all gear. Is the probe still an absolute necessity for avalanche rescue? Does making rescue gear a monolithic, inseparable kit improve safety?

Choice-Supportive Bias

Generally we rationalize bringing rescue gear we’ve packed in the past. For expensive items, climbers exhibit attachment to the item - psychologists call this post-purchase bias. Similarly, we’re more likely to defend techniques we’ve followed in the past. Since probes have been essential kit for 50+ years, it’s important to realize this penchant and keep a fresh perspective.

Safety is the System

The principle of modern safety is to guard against the unknown. Formerly we tried to become omniscient of risk, then estimate hazards to reach an ideal decision. Death or injury was attributed to an individual and their imperfect choices.

Today, we acknowledge our “limited omniscience”. Rather than simply anticipate specific hazards, we create safe layers that protect against unknown risk. Safety now focuses on building this layered system rather than making perfect decisions.

For avalanches especially, it seems we don’t know very much about risk. While snow science has evolved, it seems snow science classes and expertise do not actually reduce avalanches. 

As an example, a team taking an AAIRE2 class recently triggered an avalanche in which the head instructor was buried and one student died (Beck Canyon). The avalanche occurred after performing many snow tests throughout the day and finding no risk. The forecast center CAIC had just downgraded overall risk. Clearly, if AAIRE instructors cannot predict an avalanche - during an actual avalanche class - the ‘unknown’ unknown is high.

From this viewpoint, is it safe to even make a decision about carrying an avalanche kit? If our focus is safe systems, the climber might consider carrying a kit in all snow conditions. If so, we need the kit to be as light and packable as possible. This brings extra scrutiny to the probe.

Marginal Benefit 

How much does the probe still benefit avalanche rescue? As explained above, formerly it was necessary - beacons were imprecise. Today, it seems with the very latest beacons and bisection techniques, searchers are able to always pinpoint with the beacon alone (tests). Some instructors have started advising to skip probes and dig right away. This also streamlines the overall process, eliminating cumbersome probe retrieval and latching. As BCA manuals say, “Simplicity is Speed.”

According to tester Steve Achelis, almost all three-antenna transceivers now get within an inch or two of the pole, even with a misoriented transmitter beacon over 3 meters high.

Even if beacon-based search is off somewhat - perhaps due to a very deep burial - does striking the victim with a probe help? Examples suggest otherwise. First, deep burials are rarer than other types, and chances of survival are much lower. Many probes are only 220cm and cannot strike these deep burials anyway. 

Next, the victim cannot actually be recovered with a precise, perfect hole. In all deep burials, the surrounding snow must be excavated. Essentially the team must “strip mine” the region of snow, regardless of exact position. If the team must clear the slope of snow anyway, the utility of the probe strike begins to fade. If the team periodically optimizes based on fresh beacon readings, and probes with material at hand (ski poles, skis, etc), it seems the dedicated probe benefit is marginal.

Returning to the Beck Canyon incident, the victim was buried to 2.7m. Coordinated under an expert, it took the team of five over 40 minutes to dig out their victim. If such massive, wholesale excavation is required anyway, the probe benefit seems to diminish.

Probing Considered Harmful?

Besides delaying rescue, probing can mislead. While class training always probes uniform snow, real avalanche debris is heterogenous. Buried ice blocks, logs, rocks and chunky snow lead to false and ambiguous strikes. The radio-based position is mostly immune to those factors.

Furthermore, rescue protocol is continue probing until a strike is reached. If the probe is of borderline length or mishandled, rescuers may become dismayed after no strikes. Panicked rescuers also usually probe on a plumb line, further shortening their reach. Hence a probe spiral may misfocus the rescue on distant debris, rather than the accurate original position.

Vendor Bias

The climbing world generally looks to vendors for guidance on techniques and gear. While makers are experts, they do skew their instruction toward purchase. For example, while the UIAA is a neutral body, their Alpinism manual describes prusik hitches as outdated, advocating the Petzl Tibloc instead. Looking closer, the manual is sponsored by Petzl, perhaps suggesting a bias.

Similar bias may exist in the mere necessity of some gear. Probe vendors like BCA advocate the essential necessity of probing, but we need to balance that with self-interest. This bias is propagated somewhat to neutral authorities like AAIRE and UIAA, who are sponsored by (or merely receive free gear from) vendors.

Conclusion

The probe is handy for avalanche rescue, but success is now possible without it. Probing is no longer essential. Rather than treating avalanche gear as a tripartite kit, we suggest bringing some of the gear, all of the time. For example, just carrying a light (150g) beacon like the Micro BT Button, even when risk is low. This refocuses our gear as an ever-present layer of safety, rather than a heavy kit that’s left behind based on perceived hazard. Ultimately, by selectively packing rescue equipment, we can improve safety.