(Reprinted by kind permission of the editor 'Summit' magazine)


THE article "Avalanche Search Today" by Walter F. Lorch— Summit, April, 1974, presents a valuable introduction to electronic avalanche rescue. Mr. Lorch's report is based on experiments which were performed under controlled conditions in Switzerland during the winter 1973-74. We believe that readers of Summit may be interested in some additional informa¬tion about these devices. Skadi was the first of this equipment to be used in regular ski patrol operations and has proved itself by saving several lives in actual avalanche accidents. A lot can be learned from these accidents, for example, although the buried skiers were found and dug out within ten minutes, all were already unconscious. We will be happy to supply more detailed information about these accidents.

Fortunately, no one wearing a Skadi has yet lost his life in an avalanche accident. However, one must realize that no piece of electronics can protect one from avalanches. All that an avalanche rescue transceiver can do is to assure a more speedy recovery of the body on which the transceiver is located—dead or alive. Obviously, the transceiver will do no good if it becomes separated from the body—for example if it is carried in a pack which is ripped off by the avalanche. It is recommended that the transceiver be carried in a securely closed pocket.

Probably the single most important point not brought out in the referenced article is that all of these systems do not operate on the same frequency and therefore equipment of different manufacturers may not be compatible with each other. Skadi- U.S.A. and Pieps-Austria both operate on the same frequency— 2,275 Hz and are operationally fully compatible, although they differ in many other respects. Skilok-British operates at 10 kHz, Autophon-Swiss operates in the range 400 to 510 kHz and Lawinenspecht-Yugoslavia at approximately 100 MHz. The last three frequencies are by international agreements assigned to Aircraft/Marine Navigation and Communications and to FM broadcasting. Disregarding considerations of legality and possible need for licences, the main problem with operating in a radio band is that avalanche rescue operations can be interfered with by powerful radio transmitters, some of which come on the air spontaneously at totally unpredictable times.

Both the U.S. Forest Service and IKAR—International Com- mission for Alpine Rescue—are attempting to stem the prolifera¬tion of incompatible equipment and have endorsed the frequency of 2,275 Hz, at which Skadi and Pieps operate, as an international standard for avalanche rescue. This frequency was selected after much research and experimentation with other frequencies. One of the major considerations which led to the selection of this frequency was that its use leads to simpler, and therefore, hopefully, more reliable equipment. The reason for this is that this frequency is in the audio range so that many of the compo¬nents required by a radio system can be eliminated, e.g. modulations, local oscillators, mixers, demodulators, I.F. amplifiers, etc.

Parties which are using different equipment can become involv¬ed in the same avalanche accident. For example, consider the accident which occurred in the Cariboos on February 17 of this year (1974). One party of skiers released a major avalanche which roared down 3000 feet vertically onto two other ski parties standing in the runout area. In all 20 people were caught, 4 were injured, 2 seriously, and one skier was killed. This accident is particularly appropriate to this discussion because all Of the skiers involved, as well as the rescuers, were equipped with electronic avalanche rescue transceivers of various manufacture. Two of the parties in the accident were equipped with Skadis and one with Autophons. A fourth party, which assisted in the rescue operations, was equipped with Pieps, which it will be recalled is compatible with Skadi but not with Autophon. It can easily be imagined that with so much diverse equipment involved in the same accident, quite a bit of confusion can result when it is known that all of these units are not operationally compatible. Anyone contemplating purchase of this type of equipment should be certain to buy only units which operate at 2,275 Hz. This frequency is already the most widely used in North America and all avalanche transceivers manufactured in the future should operate on this frequency.

During the past winter hundreds of professional Ski Patrolmen participated in Skadi clinics which included the following standard test problem. A single searcher was asked to locate and to dig out a Skadi which had been buried three feet in the snow at a distance of approximately 150 feet from the starting point. The simulated avalanche path was about 150 feet wide and more than 250 feet long. A total elapsed time of from 5 to 10 minutes from the start of the search until the Skadi is actually out of the snow is considered as passing. It is not easy to complete this problem in this amount of time and you can expect that it will take longer the first time you try it. A person who is not familiar with this equipment will usually be hesitant in its use and will start to dig for the victim without pinpointing the exact location ; both of these errors waste a lot of valuable time. We found that it usually takes much longer to dig the transceiver out than to locate it, even when a full size shovel is available.

It is therefore important to pinpoint the exact location so that only a minimum size hole need be dug and thus the total time required to complete the problem can be reduced. It is during the final phase of the search that practice and training pay off the most.

Although all of the electronic avalanche rescue equipment is relatively simple to operate, you should carefully read and follow the instruction manual both as regards maintenance (charging and replacement of batteries) and rescue operations. An avalanche accident is not the place for on-the-job training. Unfortunately, Murphy's law, which states that if something can be done wrong someone will find a way to do it, applies here. For example, during the clinics we have observed the following errors which could be disastrous in actual use :


Skadi carried with switch in OFF position instead of on TRANSMIT.

Search attempted with Skadi switched to TRANSMIT instead of RECEIVE.

Search started with volume control turned all the way down instead of all the way up.


Transceiver is off. It is impossible to home in on it.

Transceiver cannot pick up buried unit and will interfere with other searchers.

Will not find the victim unless the searcher walks right over him.

One should also be on the lookout for the man who either joins a rescue already underway or merely stands on the sideline to observe. In several simulated *and at one recent real avalanche accident such a latecomer unknowingly disrupted the operation because he had left his unit on transmit. Some of the equipment will even pick up signals from units operating at other frequencies if the range is short enough. For example, Autophon will pick up Skadi and Pieps at a range of a few feet.

When properly used, avalanche rescue transceivers are very effective ; for example, the Swiss computed that one Skadi equip¬ped rescuer will search an area as fast as 490 men with probe poles. Therefore a large number of would-be-rescuers are not needed and may, in fact, hinder the operation.

Obviously, the safest approach is never to expose oneself to avalanche danger. When this is not possible the chances for survival can be considerably improved by equipping all members of the party with avalanche rescue transceivers and making sure that everyone is proficient in the use of this equipment.


  1. Avalanche Search Today, Walter F. Lorch, SUMMIT, April, 1974.
  2. Bericht uber die Prufung von technischen Hilfsmitteln zur Ortung von in Lawinen verschutteten Personen, Dr. W. Good. Interner Bericht NR. 496. Eidgenossisches Institut fur Schnee- und Lawinenforschung, Davos, Schweiz, 28 August 1969.
  3. Avalanche Victim Detector VS68 "Barryvox", Autophon Brochure 1584 20.A.274.
  4. Testbericht "Lawinenspecht" 1973, Dr. W. Good. Interner Bericht NR. 531, Eidgenossisches Institut fur Schnee- und Lawinenforschung, 12 April 1973.
  5. USFS Avalanche Handbook, Ronald Perla. In preparation-anticipated date of publication, 1974.
  6. Check to the "White Death", Internationale Seilbahn Rundschau 4/1973. Technical University of Graz, Austria.
  7. Avalanche Notes, U.S. Forest Service Westwide Avalanche Network.


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