Trained AvSAR responders should be able to quickly and effectively conduct a transceiver search. Responders must also maintain situational awareness and be able to guide and direct other responders on scene. Although circumstances are different in every incident, the basic search procedures and the stages of a transceiver search are the same in all scenarios.
Upon arrival on the scene of an avalanche incident, responders must:
In an organized rescue where the probability of a live recovery might be low due to the amount of time elapsed, performing avalanche control before exposing numerous rescuers to the slope may be the preferred option.
If a responder has seen the subject disappear and is above that point, the first action should be to immediately proceed to that point and mark it with two crossed poles. In an unwitnessed burial, interviewing other members of the group and evaluating entry tracks may help refine the likely search area.
Remote triage refers to the process of prioritizing resources to maximize the number of survivors when rescuers do not have direct physical access to the subjects. It begins as soon as the safety of the rescue party has been considered, and before any search actions begin.
When the search area is larger than can be searched with the available rescuers in parallel, it is important to focus efforts first on locations with the highest survival chances (high-priority search areas). These search areas include likely burial areas such as benches, above trees, inside corners, or at the bottom of run-out zones. Tracks and surface clues may help identify high-priority search areas in unwitnessed events, or in avalanches with no last-seen points. Areas where the subject could have sustained fatal injuries (i.e. from falls over cliffs, impacts with trees or terrain) are lower priority than areas where the run-out is smooth and survival chances are greatest.
In most cases, search members will have varying levels of response skill and capability, and may be experiencing some degree of shock. Some may be partially buried or injured themselves, or the group may be spread out over the terrain.
Everyone on the scene should participate in the search activities unless acting as the avalanche lookout, however it is beneficial to have someone take charge of the scene.
For the group leader, they must do the following:
For the initial transceiver searchers, they must do the following:
A signal search is the first phase of a transceiver search. The purpose is to quickly search the avalanche deposit in order to acquire a signal. The searcher should be running or skiing.
During this phase, it is important to maintain an appropriate search-strip width. Search-strip widths vary between different transceivers; manufacturers provide recommendations for each model of transceiver. The recommended search-strip width represents double the maximum effective range of the transceiver with a non-optimal orientation between the transmitter and receiver antennas, and with a 98% likelihood of detections.
Using the widest search strip possible will result in optimal coverage of the search area, and provide the highest survival chances. However, it may be prudent to reduce the search-strip width for the following reasons:
While performing the signal search, searchers should rotate their transceiver through all three dimensions at 1-second per dimension. The rotation should be done near the ear, while the rescuer looks at where they are walking. If a signal is detected only when the transceiver is orientated vertically, this means that the buried transceiver is orientated vertically as well. The searcher should continue until they can hold a signal while their transceiver is orientated horizontally, however they may be able to approximate the signal direction if they can get two points where the vertical orientation can resolve a signal.
There are two primary search patterns used in the signal search: a ziz-zag search pattern, and a straight-strip search pattern. The zig-zag search pattern is the preferred method with only one searcher and is commonly completed on skis. The searcher must ensure that the wide part of the triangle does not exceed the search-strip distance. Using the zig-zag search pattern requires that each leg of the search pattern ends at the edge of the deposit. The straight-strip search pattern is done with multiple rescuers covering the entire deposit at the same time.
The coarse search begins once a signal is obtained. The searcher continues to move rapidly in this phase, slowing down only as the distance gets below 10 meters. As the coarse search progresses, it is critical for rescuers on skis to balance between search speed and search precision. In the last stage of the coarse search (<10 meters), it is very easy to overshoot the burial site and lose time by having to walk back uphill. In particular, the last 5 meters of the coarse search should be conduced very slowly (transitioning from a coarse search to fine search).
The procedure for rescuers conducting a coarse search is as follows:
The fine search is done at a slower pace to provide the most accurate distance indication. The searcher holds the transceiver close to the snow surface and begins a series of right-angle ‘brackets’. Then, the distance minimum on each bracket is determined. Two or three right-angle brackets may be required to effectively determine the final location. It is important that the searcher holds the search transceiver at the same orientation and close to the snow surface in order to avoid changes in reception due to antenna orientation. The searcher must also complete each bracket fully by going past the lowest distance point until the distance indication begins to rise again.
The final fine-search location point may not be exactly above the buried subject due to the bending of the flux line. If there are multiple searchers converging in the fine search, it is not efficient for all searchers to continue with the transceiver search. One proficient searcher should finish the fine search and pinpoint, while someone begins probing systematically above. Other searchers should begin shovelling just below the pinpointed location.
With shallow burials (<1m), it is important to not waste time with bracketing. It is more efficient to start probing. Additional brackets only result in small gains in accuracy and can be very time consuming. Immediate proving will lead to the buried subject much more quickly at this stage of the search.
Square Probing. Square probing is the current best technique at pinpointing the exact position of the buried subject.
Square probe using the following steps:
Position Probing. Performed after a probe strike is made. Knowledge of the subject’s position is desired to facilitate shovelling and to more efficiently access the subject’s airway. This operation must be done quickly because time is of the essence.