Searching with avalanche rescue beacons

The small electronic device known as an avalanche rescue beacon is the principal tool for finding buried victims.

A rescue beacon can be switched to either transmit or receive signals at a set radio frequency. Rescue depends on each member of a climbing party carrying a beacon, which during the climb is left switched on to the transmit mode. Searchers switch their beacons to the receive mode to zero in on the automatic transmission from a victim. A rescuer who has taken the time to practice with the battery-powered beacon, also called an avalanche transceiver, should locate a victim in short order.

Climbers will encounter beacons that use a frequency of 2275 hertz (most common in North America) or 457 kilohertz. The United States is switching to the world-standard 457 kilohertz frequency, with the change to be completed at the end of 1995. In the meantime, to avoid incompatibility, the American Association of Avalanche Professionals recommends the use of only 2275 hertz or dual frequency beacons through the end of 1995, and 457 kilohertz or dual frequency beacons only after 1995. Some models transmit both frequencies at the same time.

The main thing is that all the beacons in a climbing party transmit and receive a frequency in common. The workings are packaged in a crush-proof case inside a pouch that a climber typically straps around the neck and carries under the shirt. The device comes out for rescue work, and the searcher listens for transmissions through a tiny earphone carried with the beacon.

Initial beacon search

If the original quick scuff search for an avalanche victim turns up nothing, start an organized beacon search. The leader checks every beacon to be sure they are switched from transmit to reccive. A line of searchers spaced no more than 60 feet apart across the slope starts where the victim was last seen and works its way downhill.

Put the volume control all the way up on every beacon. Move in unison, stay in a straight line, and keep talk to a minimum. Searchers stop every 10 paces and slowly rotate their beacons left and right, then front and back, listening closely for a signal. When a signal is picked up, one or two persons start to track down the sound with a final beacon search. (If there is more than one victim, the rest of the line continues its work. As each victim is found, turn off his or her beacon so searchers won't continue to pick up those signals.)

Final beacon search

Using a single rescue beacon, the final searchers follow a very critical series of steps to zero in on the signal from the buried victim (fig. 12-48). This is what they do:

First of all, orient the beacon for maximum signal strength, moving the unit back and forth, front and back, to find the best position. Then reduce volume as low as possible while still hearing the signal. Keep the beacon in the same orientation as you walk in any straight line. As soon as the signal reaches a peak and begins to drop, again reorient the beacon for maximum signal, and then reduce the volume as low as possible. Holding this orientation, continue on the same path. When the signal fades out, mark the spot.

Without changing orientation of the beacon, turn yourself around and retrace the same pathway. When the signal fades out again, mark that spot. You now have a straight line bracketed at the end by points where the signal disappears. Run to the center of this bracketed line and make a 90-degree turn. Repeat the process. Reorient the beacon for maximum signal, reduce volume to the minimum, and walk in a straight line until the signal fades out. Mark the spot, turn around without disturbing

Point of second signal decline

Point of first signal decline

Point of second signal decline

Point of first signal decline

Signal detected i

Fig. 12-48. Beacon search bracketing: a, first bracket; b, second bracket; c, summary of beacon search bracketing. (Illustrations by Ray Smut ek, reprinted by permission, from "Avalanche Beacons." Summit [March-April I 1984.)

orientation of the bcacon, and retrace your steps until the signal again disappears. You now have another straight line bracketed by two fade-out points. Run to the center of this new line and again make a 90-degree turn.

Work fast and efficiently, without worrying too much about precision. Continue this process of making bracketed lines until the distance between fade-out points on a line is less than 6 feet. You are now very close to the victim.

Finally, on hands and knees pinpoint your missing partner by moving the beacon from side to side and front to back in a small criss-cross. A loud signal when the volume control is down means you are close. Then dig. Use the beacon to recheck the victim's location with each 2 feet that you dig down. You have successfully found your stricken partner as quickly as possible.

Avalanche Rescue Beacon

of first decline of second signal decline of first decline

Continue reading here: The Rope

Was this article helpful?

0 0