A ground fall whilst being lowered from an instructor-led tree-climbing activity highlights cross-loading issue.
The participant fell from near the top of the activity having just begun to descend and having become detached from the rope.
The participant was being bottom-rope belayed by an instructor and was attached to the rope using a double action (twist & open) twist-lock karabiner. The karabiner was attached to fig.8 on a bite with a stopper knot and the belay loop of the participant’s harness.
It appears that the karabiner was cross-loaded as the participant lowered their weight onto the system with the belay loop loading the gate, and the rope the back bar. A combination of the cross-loaded karabiner and the loading and unloading of the system then resulted in the karabiner opening and remaining on the rope as the participant fell to the ground.
More commonly used alternatives are a variety of screwgate, triple-lock and quad-lock karabiners, together with captive eyes and other adaptations, as well as mallions and indeed tying in directly to the rope. This incident highlights that in some circumstances double-action karabiners are used as the single attachment point.
- Double action twist-lock karabiners can and have opened whilst being used to attach participants to the rope during climbing activities.
- The configuration in which they are being used should be carefully considered in light of this incident and the alternatives available.
- Where providers and/or operators of activities do not have considerable experience of such equipment they should seek the advice and guidance of an appropriately competent technical expert. In this instance such a person is likely to be an experienced holder of the Mountaineering & Climbing Instructors Award (MCI), the British Mountain Guides Carnet (BMG) or be a European Ropes Course Association (ERCA) trainer.