By analysing the anchor line and casualty lift line in detail we can see the many advantages of this system .
The most important advantage is that the anchor line can be redirected directly over the casualty . The final redirect point would not be suitable for a direct attachment of the belay line directional as it is too far out on the branch , and the force would be applied at 60 ° to the lever arm of the branch causing excessive bending moment ( torque ). Set up as shown , the force applied at each redirect is of either low magnitude or optimal direction .
Secondly , the anchor line can be installed through multiple branch unions without any need to worry about friction . If the main line were to be redirected at multiple points with the intention of using it to lift the casualty , an
efficient directional pulley would be required at each redirect . This might be time consuming to install , depending on the tree size and architecture . The anchor line can still be lowered if necessary but does not need to be pulled through against the friction at each redirect .
Finally , the casualty lift system can be installed on the ground through an efficient pulley , checked , and then hauled into place by pulling on the tail of the anchor line . If the casualty is conscious , it may then be possible to perform a ground-belayed self-rescue . If a rescue climber must ascend to the casualty , the entire lift and belay system has been pre-installed and checked before they reach the casualty and their task requirements are simple and linear .
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