So with a single rope system, what's the third point of contact?
I will take the bait now
First the disclaimer, I am not currently accredited in Vertical Rescue so some of the information could be 'out of date'....
But, the single rope is the least point of failure in the system. If you are completing a rescue litter rescue, then you use a climbing rope of greater diameter than a single person rescue (I think 13mm or above).
This rope has a huge breaking strain of approx 5 tonne. (
Blue water ropes). The prussic lines, slings, knots in the Weston rig have less capacity and thus more of a concern.
So within SES we trust the rope implicitly because it is checked, logged and re-checked. Multi-point anchors are used whenever available.
So the three-points of contact for the rescuer are attachment to stretcher, attachment to rope above stretcher knots (via chest & waist harness) and physical to cliff (last one is dubious).
Other methods used by CFS in vertical rescue are banned within SES (eg seat belt devices delivered with rescue litters are not used. Each casualty is lashed into the stretcher at all times).
Has I stated before, lets agree to disagree until a multi-service standard is issued. But SES have done vertical rescue training for 30+ years that I have been associated with them.....
EDIT: Changed the link so it wouldn't make the page too wide