Self arrest is a mountaineering related maneuver in which a climber that has fallen and is sliding down a snow or ice slope arrests, stops, the slide by himself without recourse to a rope or other belay system. If you were looking for the car, please see Mercury Mountaineer. ... In climbing, belaying is the technique of controlling the rope so that a falling climber does not fall very far. ...

Self arrest can be performed by using an ice axe or by using the climber's hands, feet, knees and elbows. Ice arrest with an ice axe is a difficult maneuver, without it the probability of effectively arresting a fall is greatly diminished. An ice axe is a versatile mountaineering tool that practically every mountaineer will carry. ...

Self arrest techniques

With an ice axe:

The most important part of the maneuver is to get into self arrest position. In this position the climber is looking face down with feet oriented towards the valley, arms tucked in, one of the hands on top of the ice axe the other down the shaft. The top of the axe is against the shoulder or its vicinity and the pick of the ice axe in contact with the slope. Once in this position the climber arcs his body, so that it contacts the slope mainly in three points, the pick and his feet or knees, in order to bring as much of his weight to bear on the pick as possible.

This is easier when the climber falls face down and is sliding feet first towards the valley. If he falls in any other position, face up, feet toward the slope, etc, he must first orient his body in the optimal position by twisting his body and using the pick of the ice axe as a pivot point. In these cases the maneuver may be much more difficult to perform.

Without an ice axe:

Without recourse to an ice axe the climber should try to orient his body face down, feet towards the valley and to put, by arcing his body, as much pressure as possible in his hands and feet, or knees.

While wearing crampons:

In both cases a climber wearing crampons should put his feet up and use his knees instead. Putting weight on the feet while wearing crampons will cause their points to snag in the ice or snow, causing injury to the climber's ankles and sending him tumbling down the slope without control. Crampons on a ski boot Crampons are a framework of spikes that are attached to boots to provide traction on snow and ice. ...

Effectiveness of Self arrest

Self arrest is by no means an infallible technique. The chances of being able to arrest a slide in this way are estimated by reputable sources to be around 50% and they diminish rapidly in function of three factors:

- Angle of the slope: The higher the angle of the slope the harder to arrest a slide. Above certain angles the chances may be very close to nil

- Hardness of the slope: The harder the surface of the slope the harder it is to perform self arrest. In really iced up slopes the pick may fail to engage the surface or it may bounce with great force on hitting a snag making it difficult to even maintain control of the axe. Negative or neutral angle points are considered superior by some in this regard as they have a lower tendency to snag in the hard ice while others sustain that they will not penetrate ice as easily as positive angle points.

- Speed in performing the maneuver: The longer the time the climber uses before he starts to put weight on the axe's pick the longer he freely accelerates down the slope. If the climber is slow to perform the maneuver by the time he gets in self arrest position his speed may be such as to make the arrest impossible. Due to this phenomenon all climbers should at all times maintain the outmost proficiency in their self arrest skills. Many climbers would wisely dedicate a day at the beginning of the season to review self arrest techniques in order to maintain their proficiency over time. The maneuver should be practiced in all its possible variants.

Self arrest as a security measure

Self arrest is a measure of last recourse. In general one should not rely on self arrest to guarantee security while engaging a slope. Instead the appropriate techniques of self belay or roped belay should be used. Security experts have suggested that sole use of the rope without recourse to intermediate protection points, as done by roped parties during glacier travel, should be avoided in slopes. This technique may make self arrest almost impossible causing the fall of a single climber to bring down the entire party. In climbing, belaying is the technique of controlling the rope so that a falling climber does not fall very far. ...