Rock Rescue Academy Part 3: Raising Systems
Bringing Up the Patient And the Litter Attendant
Much of the time, technical rescue involves falls, with rescuers descending to the victim and then raising or lowering that person in a litter or harness.
In this next phase of our SAR Rock Rescue Academy training, new technical team members learned how to package a patient for the raise and how to properly construct the raising system to bring the victim and the attendant--and sometimes a medic as well--back to the top.
As in my first two Rock Rescue Academy articles, I want to be clear that all of these skills are new to me and I'm not qualified to instruct. These articles are intended simply to share what I'm learning from a student's point of view and provide links to additional information. Of course, none of these skills should be attempted without proper oversight by a certified instructor and only after a thorough safety check.
That being said, these are the next set of skills and topics we covered in our training for high-angle rescue.
Photo (above): The rescue captured in the above photo occurred on Table Mountain, Cape Town, South Africa, said to be one of the most difficult rescue operations in years. The mission, managed by Wilderness Search and Rescue in winds gusting up to 64km/h, took more than six hours. For more on the story, see Thomas Sly's Flickr page.
The Ten-To-One Safety Factor for Rope Rescue Systems
A minimum rule of thumb for rescuers and rescue loads
Technical team students learned early on in the academy that there should never be any less than a 10-to-1 ratio between the weight -- or more accurately the force -- of the load (which is the "1") and the load capacity of the system (the "10").
In other words, if there's a single person going over the edge, and that person weighs one kiloNewton (kN) -- about 225 pounds -- then you want the load-bearing capacity of the weakest link in the system of rope/s, carabiners, anchors, pulleys, etc. to be no less than 10kN or 2,250 pounds.
More often than not in rescue situations, the load will end up being more than 1 kN, because you'll not only have the patient on the rope but also the attendant, a medic perhaps, a Stokes litter and other equipment. So a load of two to three kN -- or 450 to 750 pounds -- isn't uncommon.
I'm told fire departments use no less than a 15-to-1 safety factor. Also, I understand that this safety factor applies to a static system. When there is a shock force -- a major fall -- on the system, a 10-to-1 safety factor may be reduced to as little as 2-to-1. So you can imagine what the result could very well be if there's a fall on a system with less than a 10-to-1 safety factor.
Explaining Mechanical Advantage - An introduction to pulleys
In a rescue system, a mechanical advantage is needed any time you want to raise a patient and attendant back to the higher location. Mechanical advantage basically means spreading out work over time and distance.
This video demonstrates the basic principles of mechanical advantage.
A Three To One Raising System
Putting mechanical advantage to work
In a 3-to-1 system, the load (ie. the patient, attendant and equipment) will be raised one foot for every three feet of rope that is pulled through the system.
We set up a 3-to-1 system using two pulleys -- one near the anchor at the top (not shown in this photo) and the other closer to the load (pictured here) -- and two Prusiks, also known as "soft safeties". (One of the two Prusiks is pictured here in red.)
The pulleys in this system differ in that:
- The pulley at the anchor is stationary or fixed, meaning it does not move when the system is pulled on. We use a Prusik-minding pulley, so a rescuer doesn't have to mind it.
- The lower pulley closer to the load is a traveling pulley that moves when the system is pulled on.
While hauling, the system will need to be reset when the traveling pulley comes up to meet the stationary pulley and the load can't be pulled up any further. Resetting means expanding the system back to its original length in order to resume hauling.
Illustrating A Traveling Pulley
Each Prusik in the system performs a specific function:
- The Haul Prusik is the one closest to the load. It attaches the pulley system to the main line that goes over the edge and down to that load.
- The Ratchet or Progress-Capturing Prusik holds the main line while the pulley system is reset, so the progress that has been made in the raise so far is not lost ... meaning, the rescue load will not drop.
See how to tie a Prusik knot on AnimatedKnots.com.
Increasing Mechanical Advantage
For heavier rescue loads and/or fewer haulers
Generally speaking, the average person can pull about 44 pounds (or 20kg), when talking about a 1-to-1 mechanical advantage--ie. a person pulling up on a rope running directly to the load. So the more mechanical advantage there is in a system, the more a single person can haul, and the more people there are to haul, the less mechanical advantage will be needed.
As far as I know, the lowest mechanical advantage our team will ever use in a rescue situation is a 3-to-1, but oftentimes that will not be enough mechanical advantage based on the force of the load and the number of haulers available.
In that case, a 5-to-1 system would be one option for increasing the mechanical advantage. Then, the rescue load would be raised one foot for ever five feet of rope that's pulled through the system.
Changing from a 3-to-1 to a 5-to-1 is accomplished by running the line back down through a double haul pulley and then up towards the anchor again, perhaps through yet another pulley to perform a change of direction for the haul.
Like the 3-to-1, this is considered a Simple Pulley System, because there is one continuous rope running back and forth between pulleys on the load and the pulley or pulleys at the anchor.
Some basic principles of simple pulley systems are:
- If the final pulley closest to the haulers is fixed at the anchor, it is a "change of direction" only and doesn't increase mechanical advantage.
- The number of pulleys needed for a simple raising system, not counting a pulley used as a "change of direction," will be the mechanical advantage minus one.
- The mechanical advantage of a system is calculated by counting the number of ropes under tension on the load side.
There are also Compound Pulley Systems, which are basically one simple pulley system pulling on another simple pulley system, with the traveling pulleys moving towards the anchor at different speeds. Compound systems provide more mechanical advantage than simple systems with the same number of pulleys and with less friction.
Some basic principles of compound pulley systems are:
- The mechanical advantage is calculated by multiplying the mechanical advantage of the simple pulley systems. So if you have a 3-to-1 pulling on a 3-to-1, you'll have a 9-to-1 mechanical advantage.
- To minimize the number of resets that will be necessary, the last pulley system closest to the hauler/s will need to be anchored far enough back to allow each pulley system to "collapse" or max out at the same time. With a 3-to-1 pulling on a 3-to-1, the last 3-to-1 will need three times the reset distance.
A Change Of Direction or "CD"
When raising a load, sometimes it's necessary to change the direction of the pull if, for example, there are obstacles such as boulders or trees in the way. This is accomplished with the use of another pulley, either on the same anchor as the raising system or on another anchor, which may be another tree.
A change of direction doesn't affect -- or doesn't add to -- the mechanical advantage of the system.
In the photo above, my teammates and I are practicing a hot change over in the SAR building, with the person who's standing (tan pants) pulling tension on the line to act as the load.
The green strap you see is webbing, tied into a loop with a water knot and attached with a carabiner at one end to the anchor (the red "bear claw") and, on the load end, to the main line with a carabiner and a (yellow) Prusik. This Prusik is attached out beyond the rescue rappel rack, which is used for lowering. Once the Prusik is set (locked) and the weight of the load is lowered onto that Prusik, this system bypasses the rappel rack, so that device can be removed from the line and the raising system can be set up.
In the picture, the load is already on the green strap and yellow Prusik as my teammates assemble a 3-to-1 raising system with pulleys.
(Note: There is another--and easier/simpler--method of doing a "hot changeover" that my new technical teammates and I were taught, but I don't have a photo. This alternate method eliminates some steps, making the change much more efficient.)
Cold Change-Over vs. Hot Change-Over
People on the ground or people on the rope
A cold change-over is when a lowering system is changed to a raising system without the load on the rope. In this case, the attendant may be firmly on the ground below, packaging the patient for the raise, without any force on the system.
A hot change-over, by comparison, is when the lowering system must be changed to a raising system while there is a load (ie. an attendant) on the rope, mid-face.
These terms may be used to describe the reverse as well, when a raise must be change to a lower.
(Note: The term "hot change-over" is also used to describe changing from a rappel to an ascend mid-face. Or vice versa.)
During a cold change-over, those tending to the main line and belay don't have to worry about the attendant or the patient, only about getting the system changed properly and as expeditiously as possible. During a hot change-over, however, the integrity of the system must be maintained so there isn't a fall; there should be as little movement as possible of the load.
Setting up for a raise: My teammate attaches the haul Prusik to the main line, wrapping it three times for a heavy rescue load.
Building a Simple Pulley System
This video gives a good demonstration of a rescue lowering and raising system, using a 3-to-1 mechanical advantage pulley system along with a brake bar. The instructor will show you how to change over from a lower to a raise.
Securing the victim in a litter or rescue basket
Properly secured in a litter, the patient will not slide up, down or out no matter how the litter is oriented--horizontal, on its side, feet down, head down, or face down. Often when raising the patient in the litter, the litter will end up in a vertical--or pike--position just before coming up over the edge.
The patient may or may not be placed on a backboard and may or may not have his or her head and neck secured.
One has to take injuries into account when packaging a patient, but, at the same time, the goal is to get that person to safety. And that will likely involve some unavoidable additional discomfort.
Some things to think about when packaging a patient:
- Talk to the patient and let them know what the plan is.
- Use a backboard if there is any potential spinal injury, which there most often is where there's been a fall.
- Use padding if possible--ie. under the knees--and head and eye protection. (We have a litter with a clear head shield.) The patient will be more secure and comfortable in the litter is there is padding is packed around their body.
- Protect the patient from the environment. Prevent heat loss or, to the contrary, sun exposure and too much heat.
- Packaging a patient on their side may be a good choice to protect their airway if there's a chance they may vomit.
- Avoid tying the patient in too tightly--using too much compression--so as not to impede circulation.
Properly strapped into a Stokes litter, a patient will be secure when the litter is vertical.
Start With The "Grady Straps" Configuration - This prevents movement up, down, left, or right.
Note: This is not the complete patient packaging set-up for high-angle rescue. This Grady Straps configuration would be followed by additional tie-ins in a zig-zag pattern, cross-straps, and foot loops as long as an ankle or foot injury doesn't prevent them.
See Wikipedia for more information on Grady Straps.
The Spider Attachment & the Litter Attendant
A Litter Pre-Rig Spider or "Bridle" is a commercially designed system for raising the litter with an attendant attached to guide the litter and tend to the patient. This rigging is adjustable, meaning the attendant can lower the head or foot of the litter to keep it level, to maneuver around obstacles such as overhangs, or to move the litter in a pike position for bringing up over the edge.
During a raise, the litter attendant pushes off the cliff face with their legs, while pulling the litter with their arms to keep it away from the rock. At times, the attendant may need to move above the patient--suspended between the patient and the spider--particularly when negotiating an overhang.
The attendant will likely have to do a lot of maneuvering, both of themselves and the basket while on a raise, definitely not an easy task.
Read About High-Angle Rescue
High-Angle Rescue Field Guide
Another Recommended Technical Rescue Resource
Our Rock Rescue Academy: My other articles about the training....
This content is accurate and true to the best of the author’s knowledge and is not meant to substitute for formal and individualized advice from a qualified professional.