Friday, March 4, 2011

Avalanche transceiver refresher

You might think with snowshoeing treks there would be little or no risk but to the contrairy if you are trekking in an area with snow there will be hazards. Often when snowshoeing the hazards are from above, you might be traveling along an easy track in the valley bottom but above you might be slopes that are completely loaded and ready to deposit volumes of snow on the valley below. many of the more adventuress snowshoe routes venture into areas that have avalanche risk and many of the guide books give information  on slopes that can be potentially hazardous.

From the Prarion towards the Aravis
As an International Mountain Leader you required to have an underlying knowlegde of safe travel in the middle mountains in summer and winter. Assessing avalanche risk and be able to use and teach the practical application of avalanche transceivers is a pre-requisite of the qualification.  Although this season hasn't demanded a massive amount of transceiver use becuase of the low avalanche risk in the middle mountains it is essential that you undertake regular refreshers in search and rescue so itf anything does go wrong you are able to act fast.

Mont Blanc from the roof of the Prarion telepherique
So we ventured out using the Prarion telepherique to get us up to 1850 mtrs so we had the use of deeper snow. From the top of the lift  we took the track to the right that leads you over the top of the telepherique. At this point we followed the snowshoe tracks towards the summit of the Prarion at 
1902 mtrs and found an area that was quet and open with plenty of reasonably deep snow.

ARVA avalanche transceiver
Electromagnetic signal
Starting with the avalanche basics... how does the transceiver work, how does it transmit? we were using ARVA devises which have a duel antenna this is a reasonable and afordable unit. Wearing the unit close to your body it is activated by plugging in the strap around the body to enable SOS mode. The unit transmits a series of signals that leave and return to the unit in an consentric pattern. The search devise is enabled in search mode and locks in to one of the transmission radiuses and takes you in an arc back to the victim.

Following the direction, distance and bleep indicator to home
 in on the victims transceiver
Once a signal is detected (on the ARVA) it is indicated by 3 ways... on an LED screen by distance in meters and arrow to show you direction of signal plus bleep (distance between bleeps gets shorter the nearer to the victim). Following the direction of the arrow, reducing the distance and listening to the bleep will hopefully lead you to the vicim.

Micro grid search at ground level
When the distance has been reduced to a couple of meters move the transceiver to just above the surface of the snow. Move it forward and back and keeping the unit in the same plane at all times you need to find the transceivers stronget signal (beeps closet together and minimal distance). At the strongest point move the unit laterally again mark the lowest distance to form a cross. At this point its time to start probing starting and the marked point and moving out in a spiral plunging the probe perpendicular to the slope and feeling for something soft opposed to hard and frozen snow or ground. 

Probing to find the victim
Once the victim is located (in our case the ruck sac with transceiver inside) we started to dig. Time is of the essence as generally people cannot survive over 20 mins under avalanche debris. Obviously it would get a little more complex if multiple victims need to be located and a whole range of techniques need to be adopted. Successful rescue is totally dependant on the speed of recovery, team work and an effective rescue approach are essential

Digging to find the victim

In practice it all seems reasonable and do-able, in reality under the panic of a real life emergency it must be truly terrifying especially when searching for close friends or family or clients... time its the crucial factor here so by being totally comfortable with the methods, if in this unfortunate situation arises being prepared would make the chances of success more feasible.

For more information of avalanche awareness & rescue see:

For avalanche awareness courses see:

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