TECHNICAL RESCUE EQUIPMENT AND TECHNIQUES
This chapter discusses the equipment and techniques used in technical rescues.
Belay and Lowering Devices
Lowering and Raising
Traversing Systems (Tyrolean Traverse)
May 1992 Written by Steve Walker and Al Green
May 1998 Revised by Werner Hueber and Al Green
March 1999 Edited by Loren Castro
TECHNICAL RESCUE EQUIPMENT AND TECHNIQUES
It has been said that there are many ways to "skin a cat." This is particularly true for technical rescue rigging because of its complex nature and many diverse techniques. This chapter doesn't attempt to describe what is "best" or to describe the "art" completely; it does describe in detail the techniques that CLMRG uses to perform technical rescues. We will modify this chapter as new equipment and data become available. We highly recommend References 4-1 through 4-11 for additional study.
In this chapter, we outline safe and adequate procedures for technical rescues. We have been practicing and performing technical rescues since 1958, and many things have evolved over the years. We have incorporated new equipment and new techniques as we became convinced of their safety and utility. This chapter describes the equipment and techniques that we are using currently. We prefer to use commonly carried climbing gear as much as possible rather than special purpose equipment. We have to carry our gear to the rescue site, and the lighter our load, the better we can perform.
This chapter, along with "hut" nights and stretcher practices, gives you most of the rescue skills needed for high-angle technical rescues, but they don't prepare you for the "exposure." All members of a rescue team who work on the rock must be comfortable with this high-angle "exposed" environment. The average person doesn't have this comfort level unless he is an active rock climber.
The safety of everyone involved is paramount! The "on-the-hill" Operation Leader (OL) must be in charge and is responsible for assigning tasks and checking that everything is done safely and correctly. The OL must know all the technical rescue skills and the capabilities of all the participants. Assigning specific tasks requires that the OL be fully aware of the strengths and weaknesses of each member.
WARNING - - Even when properly performed, loss of life or injuries may result to you or the persons you are working with. The China Lake Mountain Rescue Group and/or authors accept no responsibility for loss, damage, injury, or death resulting from information contained in, or omitted from, this chapter. We wrote this for our CLMRG members for training purposes ONLY.
Rock climbers and mountaineers use a dynamic rope. This rope is designed to be elastic to reduce the shock on the climber and anchor system if a fall occurs. For general climbing, the norm in the United States is a single dynamic rope of 9.8, 10, 10.5, or 11 millimeters (mm) in diameter. Smaller diameter ropes (8.5 to 9 mm) are used with two-rope techniques and for special applications where high-impact leader falls are not expected.
Rescue workers use a static (low-stretch) rope for lowering and raising. This rope minimizes elongation when it's first loaded and additional stretch (creep) as the load remains on it. The mountain rescue community uses 7/16-inch or 11-mm diameter ropes for both the main line and the belay line. Table 4-1 gives typical specifications for the ropes we use.
Table 4-1 Typical Specifications for Ropes
|Description||Tensile Strength||Elongation (%)||Impact Force (kN)|
|11-mm dynamic (Blue Water)||12 UIAA falls||6||8.1|
|11-mm static (Blue Water)||6500 lbf (29kN)||1.6||Much higher|
Tubular webbing is available in a variety of widths and constructions. The most popular variety is 1-inch supertape, which we use to tie in the victim to the stretcher. A more recent development is a combination of nylon and Spectra ("the strongest fiber ever made"). Spectra comes in only one width (9/16 inch) but is almost as strong as the 1-inch supertape and equal to its abrasion resistance. The smaller width is a distinct advantage when the webbing must be clipped through a carabiner because it's less likely to side load (load the gate side of) the carabiner.
Runners are loops made from webbing. The loop can be made by tying a knot or by sewing. We use Titan sewn runners made from Spectra, which are significantly (about 1000 lb.) stronger than tied runners. The recommended knot for tying runners is the grapevine knot rather than the water knot because the water knot can "walk" and untie itself. Table 4-2 gives typical specifications for the webbing that we use.
Table 4-2. Typical Specifications for Webbing and Runners
|1-inch tubular webbing (Blue Water Climb-Spec)||4200 lbf.|
|9/16-inch Titan runners (Blue Water)||6600 lbf.|
A locking carabiner is preferred for rescue applications. The locking carabiner used for climbing is adequate for rescue applications. The typical strength rating for a locking carabiner is 22 kN or 4950 lbf. Two aluminum carabiners with gates opposite and opposed can also be used.
Do not use carabiners unless they are essential to the system being constructed. For example, tie the belay line directly to the stretcher rigging because the carabiner is unnecessary. Remember never to tie or loop webbing around the cable of a wired nut or other wired piece. And girth hitching runners reduces their strength just as tying a knot would.
We rely primarily on chocks, nuts, and active camming devices to form the required anchors. Placing these devices requires that rescuers are very experienced in using them correctly. Bolts can be placed if chocks or cams cannot be used. Don't overlook the use of natural anchors if they exist (e.g., large rocks or trees).
Bolts that are already in place are difficult to evaluate and should be examined very carefully before use. Quarter-inch bolts should be considered as marginal at best, and their use is discouraged. Pitons that are already in place are also difficult to evaluate, and caution is advised.
Table 4-3 provides strength specifications in pounds of force (lbf) for a variety of anchoring devices as a function of their size. Any device with a strength of under 2000 lbf should not be used for high angle rescue work. The smaller devices do not meet this criterion and are not listed.
Table 4-3. Typical Specifications for Anchoring Devices
|Camelots||0.5, 0.75, 4.5, 5||2700|
|Metolius (3- or 4-cam)||1-10||2700|
|Black Diamond Stoppers||6-13||2250|
|Wild Country Rocks||2-10||2700|
It is also important to note that a minimum of three devices are used to form a rescue load anchor. See "Load distributing anchor" later in this chapter.
The strength of bolts depends on many factors. If all other things are equal (skill of the person placing the bolt, type of bolt, etc.), then the rock itself will be the strength limiting factor. Assuming reasonably hard rock (e.g., granite), a 3/8" x 3" Rawl 5-piece construction type bolt will have both shear and tension strengths of about 5,000 lbf.
The "Air Traffic Controller" and many other belay devices of similar design are used primarily for belaying, but they are also excellent devices for rappelling. They are light and small and don't twist the rope.
The Münter hitch is a knot that provides friction for belaying or for controlling the descent of a rappeller. It works best with a pear-shaped carabiner (a "pearabiner"). The obvious advantage is that it doesn't require special gear-but it does twist the rope.
The Yosemite technique uses only carabiners. Two carabiners form the platform, and one or two across the platform form the brake bar. The two platform carabiners have their gates on opposite sides to form a solid base. Standard ovals work best because of their size and symmetry. This technique requires no special gear and doesn't twist the rope.
Technical rescue presents many opportunities to use pulleys. The simplest is a direction change, and a more complex application is a mechanical advantage (MA) for raising a stretcher.
A pulley is essential for these applications because of the friction of any alternative device
(e.g., a carabiner). A pulley is about 90 percent efficient while a carabiner is about 50 percent efficient. We use a ball bearing unit made for rescue applications.
Prusik minding pulley
The Prusik minding pulley (PMP) is especially designed for a belay technique that we discuss later. The side plates are sized to keep two tandem Prusik knots in place when used as the belay for a raising.
The edge roller is a special purpose pulley for use on a sharp edge to prevent rope damage and to minimize friction. The big disadvantage is its weight.
We use CMC Ultra Pro plastic edge protectors for the main and belay ropes. They are lighter weight and much easier to transport than edge rollers. For edge guards, we use pieces of a fire hose that can be opened and closed with Velcro. Edge guards are used where friction is not a concern (e.g., for protecting the anchor rope or belay rope).
Ascenders are camming devices for climbing a rope. The same or similar units can be used in hauling systems to hold the load in place and to get a new "bite" of rope. Climbers prefer devices with handles that facilitate "jugging." We use the Rescucender, which does not have handles but is stronger and more appropriate for rescue-specific systems.
We currently have two different stretchers-the aluminum Stokes and the Ferno/Thomson (usually called simply "Thomson"). Each has a specific application and specific shortcomings. Rescue equipment is packaged with the stretchers:
The following items are packed with the stretchers:
The following items are packed in the accessory bags attached to the stretchers:
Two hardware bags go with each stretcher. One is for setting up the main anchor and the other for setting up the belay anchor.
The following items are in the hardware bags:
The aluminum Stokes gets the most use. This is the most useful stretcher for mountain rescue applications because it breaks down into two sections and can be carried on a backpack frame. It's light and compact enough to be carried by one person and is solid enough for vertical raisings and lowerings. A wheel can be attached to this stretcher.
The Ferno/Thomson is a basket stretcher like the Stokes, but it's plastic with a metal frame. The advantage of the Ferno/Thomson is that it slides easily over snow and is solid enough for technical rescues. No wheel is available for this stretcher.
The Sked is basically a sheet of thick plastic that wraps around the victim. It's light and can be rigged to a backpack, but it's an awkward shape when packaged. It's transparent to X-rays, which allows X-ray examination of the victim before removing him. An advantage is that it works well in a confined space-generally not a consideration in mountain rescue. We don't use it for technical rescues.
This seat is a harness designed to backpack a victim. The seat is used to carry a victim on flat, sloping, or vertical terrain. The nature of the victim's injuries must not preclude the victim from being carried in a sitting position.
Figure 4-1 illustrates the set up of the seat. Tie a figure-eight-on-a-bight at the midpoint of a 20-foot, 11-mm dynamic rope. Tie the main and belay lines through the bight with a figure-eight follow through. The rescuer must wear a seat harness and tie directly into one end of this rope with a figure-eight follow through. Locking carabiners attach the adjustable-length blue suspension strap of the seat to the rescuer and to the main and belay lines. The 11-mm rope must be longer than the blue strap of the seat. Attach the other free end of the 11-mm rope directly to the victim harness with a figure-eight follow through. Attach the main yellow lanyard of the seat to the main and belay lines with a locking carabiner after the victim is secure in the seat. The victim's 11-mm rope must be longer than the yellow lanyard. During a high-angle or suspended lowering or raising, the rescuer's blue suspension strap is adjusted so that the victim's weight is supported completely by the yellow lanyard. In lower angle terrain, the rescuer shortens the suspension strap and carries more of the victim's weight on the pack-straps.
The victim is carried in the diaper seat with the leg loops. The shoulder straps secure the victim to the harness and must be adjusted so that the "Y" is located between the victim's shoulder blades.
Note that the 20-foot, 11-mm rope and the victim harness are not required for a carry that involves only flat or low-angle terrain.
For more details, refer to the manual that is located with the seat.
Figure 4-1. Rescue Seat Rigging
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BELAY AND LOWERING DEVICES
All the rappel devices described above can be used for belaying or lowering a single climber. For stretcher raising and lowering applications, however, a device must handle a much heavier load. A possible rescue load consists of stretcher, attendant, victim, rigging, and gear-a total of about 440 pounds. We use the following devices for rescue applications:
Prusik slings with Prusik minding pulley
Two Prusik slings with a PMP is currently the best solution for belaying a rescue load. We use two three-wrap Prusik slings made from 7- or 8-mm diameter cord. The shorter Prusik is made from 53 inches of cord and the longer one from 67 inches. A concern with this technique is the flexibility of the cord. If the cord is not flexible enough, it may not grab the belay line in a fall. The pulley keeps the knots in place during the raising. This belay system requires a skilled rescuer who has trained with this belay method. It also requires a load releasing hitch (LRH) in case the knots lock up.
Brake bar rack
We use the brake bar rack shown in Figure 4-2 for lowering a rescue load, but we consider it to be inadequate for belaying. We have shown in a test case that the brake bar rack will catch a rescue load but will be destroyed in the process.
Figure 4-2. Brake Bar Rack
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Rigging for a high-angle lowering or raising (where the stretcher is horizontal) is illustrated in Figure 4-3. We use two lines for both lowering and raising-the main line and the belay line. The main line carries the load (the stretcher). The belay line should carry no load unless a problem arises. We tie large figure-eight knots into both of these lines at the stretcher end. All loose ends of the rigging system should be tied off using the pass back method or the half-grapevine knot.
Figure 4-3. Stretcher Rigging
The following points should be noted when assembling the rigging:
1. For the equalization yokes we use two 20-foot, 11-mm dynamic ropes. We use the double-bowline-on-a-coil knot for equalization. The large auto-lock carabiners in the accessory bag connect the yokes to the stretcher. We use a figure-eight-on-a-bight with safety for the tie-in to the main and belay ropes. One yoke should be shorter and should be used for the head to achieve a slightly head-up position. Pre-rigged equalization yokes are in the stretcher accessory bag.
2. The attachment loops for the main and belay ropes are tied as figure-eight-follow-through knots. The height of the rigging from the top rail of the stretcher to the main rope tie-in should be approximately 2 feet.
3. The attendant and victim tie-in uses a single 20-foot, 11-mm dynamic rope. The central figure-eight-on-a-bight knot should be very short and should be tied so that approximately 6 feet remain for the victim tie-in. The longer section is used for the attendant tie-in.
4. The stretcher attendant must be in position to guide the stretcher as smoothly and comfortably as possible down or up the wall. He must also be able to administer first aid in case of a medical emergency during the lowering or raising. This requires an adjustable tie-in in addition to the fixed tie-in to allow the necessary freedom of movement. We use two Prusiks to achieve this freedom of movement: One Prusik is clipped to the attendant's harness to adjust his vertical position with respect to the stretcher. The other is fitted with a foot loop to release tension on the first Prusik so that it can be adjusted.
5. Small end down is the preferred orientation for the large auto-locking carabiners clipped into the stretcher. The gates are always inward.
6. The stretcher tilt line should be attached to a reinforced cross-support for strength and so that the line will not abrade.
Rigging for a vertical lowering or raising (where the stretcher is vertical) is simple and requires only a secure attachment to the head end of the stretcher.
Figure 4-4 illustrates the proper method for securing the victim in the stretcher. Girth hitches must be tied at each end of the 1-inch-wide tie-in webbing and as necessary to accommodate injuries. The top rail of the stretcher must not be used for the girth hitches. Three tie-ins are used:
The first tie-in should have the first wrap go around the chest and under the victim's arm for a more secure torso tie-in and a less restrictive feel around the arms. Lower arms should be left unrestrained initially and tied with the Velcro wrist restraint strap as the last thing.
The second tie-in is around the lower part of the upper body.
The third tie-in is for the hips, legs, and feet. Start the tie-in at the hips and use one half of the 20-foot, 1-inch webbing for one side and the other half for the other side. Use the two ends of the webbing for the stirrups. These foot stirrups must be tied with a girth hitch immediately on both sides of each stirrup. The preferred method is the crossed stirrup shown in Figure 4-4. A slip knot must NOT be used because it can tighten around the foot and cause loss of circulation or other such complication. Do not use a foot stirrup if there is an injury to that foot or leg.
Pads should be used as needed to protect and secure the victim. Adaptations to the tie-in may be dictated by special first aid considerations.
Figure 4-4. Victim Tie-in
Edge attendant tie-in
Anybody acting as an edge attendant to assist with the stretcher must be tied into an adjustable-length personal anchor. See Figure 4-5 below for the recommended two-point load distributing anchor (LDA) method. A good solid single-point anchor may be used if a two-point system is not feasible.
Figure 4-5. Attendant Tie-in
Selecting a site for anchors depends on the situation. Some important considerations are loose rock; availability and location of physical features like cracks, flakes, trees, and boulders for placing anchors; edge features (important for getting started and rope management); and adequate room for rescuers to work.
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For a technical lowering or raising, at least two strong anchors are required. Call one the main anchor and the other the belay anchor. Both anchors must be "bombproof" because each must be able to hold the rescue load, and the belay anchor must be able to catch a fall if the main anchor fails. We don't discuss here the individual placements (e.g., slings, camming devices, chocks, pitons, bolts) needed for the anchor. The rescuer's rock climbing experience in placing protection provides the expertise for "bomber" placements.
Load distributing anchors
A single placement is not considered adequate even for a belay anchor in climbing and certainly not for a rescue anchor that must carry the load of victim, equipment, and rescuer.
A system to distribute the load among several anchor placements is essential.
The term "self-equalizing anchor (SEA)" is commonly used for this anchor system. However, the system is not really self-equalizing. It distributes (not necessarily equally) the load over the included anchors and allows for a reasonable change of direction. So we use the more appropriate term "load distributing anchor (LDA)."
There are many ways to construct an LDA. We use the system illustrated in Figure 4-6. The construction requires approximately 20 feet of 11-mm dynamic rope. It consists of a bowline-on-a-bight knot with short and long loops to connect to the anchors and a double-figure-eight knot to connect to the main or belay line.
The following guidelines are important in constructing an LDA:
1. We use a three-point anchor system for the main and belay anchors. The angle between adjacent legs of the three-point system should be less than or equal to 30 degrees. The length of the outer legs must be 12-15 inches (see Figure 4-6).
2. We use 5 locking carabiners. Doubled non-locking carabiners with opposite and opposed gates is an alternate method in lieu of a locking carabiner. Locking gates should be on the side away from the rock, if possible.
3. The rope should be a 20-foot, 11-mm dynamic rope.
4. Extend the anchors to the LDA, not the LDA to the anchors. The maximum drop if one of the anchors fails must be less than one foot. This means that the circumference of the large loop must be less than eight feet.
5. The angle between the outside anchor legs at the load should be less than 60 degrees.
6. The system must not include a marginal anchor. If a marginal anchor fails, the entire system is stressed unnecessarily.
7. Don't get so involved in looking for a three-point anchor that you overlook a natural anchor (e.g., huge tree, big rock).
Load releasing hitch
A Larson load releasing hitch (LRH) (see Reference 4-1) uses 20-foot, 8-mm accessory cord, two pear-shaped locking carabiners, and one standard locking carabiner. Tying this knot is easier with two people because the carabiners must be held in the proper position. Tie the ends of the cord with a figure-eight. Put one pear-shaped carabiner at the middle of the cord. Tie a Münter hitch with the doubled cord on the other pear-shaped carabiner at least one foot away from the mid-point carabiner (see Figure 4-7). Pull the mid-point carabiner toward the Münter hitch until it nearly touches, then reverse direction and pull the mid-point carabiner away from the Münter hitch until they are separated by about six inches. Make several wraps around the doubled cord between the Münter hitch and the mid-point carabiner until there is just enough space left to push a bight of rope through between the doubled cord just in front of the mid-point carabiner. Start with this bight and chain the extra double cord up to the figure-eight, then lock off the chain. Use the third carabiner to clip from between the double cord (just in front of the figure-eight) to the mid-point carabiner (see Figure 4-8).
To release the LRH and extend it for use, unclip the third carabiner
from the mid-point carabiner and unlock the chain. Before undoing the
clip the third carabiner between the double cord (just in front of the
and completely around the double cord just in front of the mid-point
so that the LRH cannot come completely apart. The chain can then be
and the wraps removed until the LRH begins to extend.
Figure 4-7. Load Releasing Hitch, Part 1
Figure 4-8. Load Releasing Hitch, Part 2
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LOWERING AND RAISING
During a lowering, the main line to the stretcher is allowed to run through the lowering device slowly and uniformly. The speed is at the demand of the stretcher attendant. We use the brake bar rack for lowering. The number of bars are determined by the load. The rope must be passed over the first bar (see Figure 4-9). An LRH is essential for passing a knot.
The belay line is allowed to run through the belay device (tandem Prusik slings with PMP) without holding the load. The belay must always be ready to take the load if needed.
A raising involves pulling the stretcher up a steep wall. In almost every case, a mechanical advantage (MA) system is required to accomplish this task. We use a Z system as shown in Figure 4-9. The main line is pulled in increments (bites) whose length depends on what the Z allows. A clamp (e.g., Rescucender or triple-wrap Prusik) on the main line holds the load while a new bite is taken. An LRH should be used between the Z system and the anchor in case a knot must be passed (see Passing a Knot).
The belay line is pulled through the tandem Prusik slings, which are tended by a PMP. Very little slack should be in the belay line.
Figure 4-9. Z System
Belay techniques for raising and lowering
Tests by various teams and agencies have cast doubt on traditional techniques for belaying rescue loads. The articles by John Dill in the summer and fall 1990 issues of Response (see Reference 4-2) are required reading. These tests have shown that the triple-wrap tandem Prusik knots with a pulley is a viable belay technique (see Figure 4-10).
We use two 7-mm Prusiks (tied with a double-fisherman's knot) of different length (53 inches and 67 inches). Three wraps are used around the belay rope. Make sure the knots are tied neatly with the bridges of the knots on the same side. Clip the two Prusiks and the Prusik minding pulley (PMP) into a pear-shaped locking carabiner in the following order: long Prusik first, then the shorter Prusik, and then the pulley (again, see Figure 4-10). Then clip this locking carabiner into the belay LDA in series with the LRH. When properly positioned, the Prusik knots will be about 4 inches apart. The belayer must be experienced in using the Prusik belay and must be very attentive to keep the knots taut but free running. On a lowering, the belayer should hold both Prusik knots with one hand and pull out some belay rope using the thumb and wrist to form a bight of slack (see Figure 4-11 and Reference 4-1). The rope should be flaked so that it will enter the tandem Prusik system smoothly from the side without twisting. Reference 4-3 recommends that the belayer should grab both knots and slide them along the rope, twisting the extended hand 90 degrees for slack. The belay line should never have more than 4 inches of slack.
When belaying a raising, the tandem Prusik may be tended by the PMP as the belay rope is pulled through it. For passing a knot safely, two sets of Prusik slings must be available. An LRH is required in case the Prusik knots lock up. After using the LRH, always re-tie it so that it will be ready for its next application.
Avoid using the belay rope without back-up for shifting the load during a raising or lowering.
Figure 4-11. Tandem Prusiks and Belayer on a Lowering
In case a lowering or raising over more than one rope length is required, tying ropes together may be more advantageous than setting up additional anchors and systems for raising and lowering. Passing knots in the main and belay lines requires considerable additional training.
1. In the belay rope for a raising (the belay is not holding the load): Place a second set of tandem Prusik slings approximately one foot below (downhill of) the knot and clip them to the LRH with a separate sling and locking carabiners (independent of the original belay). Remove the PMP and place it with the second set of tandem Prusik slings below the knot. Remove the original tandem Prusik slings.
2. In the belay rope for a lowering (the belay is not holding the load): Let the knot get close to the PMP. Place a second set of tandem Prusik slings above (uphill of) the knot and clip into the LRH. Remove the original set and the PMP. The PMP can then be placed with the second set of tandem Prusik slings. This leaves about a foot of slack in the belay line until the stretcher is lowered a little to remove the slack.
3. In the stretcher rope for a raising (using a 3:1 Z system): The Rescucender that is moved to take a new bite can simply be placed on the other side of the knot. The load is then pulled up until the knot is close to the Rescucender that is holding the load. Place a Prusik (8-mm cord, triple wrapped) on the load side of the knot down at least 2 feet below the knot and clip it into the LDA. Set the Prusik to hold the load with minimum movement when the load is transferred from the Rescucender. To transfer the load, the Z system must be pulled just enough to allow the top Rescucender to be released. After the Prusik takes the load, the Rescucender and top pulley can be moved down past the knot by extending the connection to the LRH about two feet. With this accomplished, the Z system can be pulled again to allow the removal of the Prusik that was placed to hold the load during transfer.
4. In the stretcher rope for a lowering (extra Rescucenders normally used for raising are available): Let the knot get to about one foot before the brake bar device (do not let the knot get locked up in the brake bar). Attach a Rescucender down the rope below the brake bar device, and clip the Rescucender with a sling and locking carabiner to the LRH. Allow the Rescucender to take the load, then move the brake bar device to the other side of the knot and clip it into the LDA (not the LRH). Release the LRH until the brake bar again takes the load, and then remove the Rescucender.
The single most important thing for good communication is that one person is in charge and has full control of the exercise. This person might be called the Safety Officer (SO), Operation Leader (OL), or something else. We use the term OL. The OL is responsible for everything (which doesn't mean that he does everything). The OL makes assignments for each task that needs to be done and checks each setup to make sure that things are done safely.
Communication be>omes important after the individual assignments are accomplished and the raising or lowering is ready to begin. The OL coordinates the process. Initially, the OL starts all actions. When the stretcher and attendant are ready to start moving, however, the attendant initiates the actions. Only the attendant knows whether he wants to start, stop, go faster or slower, etc.
The method of communication depends on the situation. Simple voice commands work well while everyone is at the anchor site. After the stretcher has moved away from the anchor site, hearing the commands might be difficult. The OL should assign one person to the edge to watch the stretcher's progress and relay commands as needed. Radios should always be available and used if necessary.
Some teams recommend a whistle code, and it has some advantages. A whistle is easily heard, and the source can't be confused (assuming only one whistle is on site). However, you must remember a possibly complex code. A simple "one blast for start" and "two blasts for stop" isn't enough.
A hand line attached to the stretcher can be used to guide the stretcher from the ground and to help the stretcher attendant in directing the stretcher and providing an offset from the direction of the main line.
An additional rope between the anchor and the ground can be used to provide an offset so that the stretcher can be moved over such obstacles as large overhangs. The stretcher is attached to the guiding line with a tether sling at the yoke and a pulley. This guiding line is under little tension and can be hand held by a rescue team on the bottom.
This line is similar to the guiding line, but it is anchored at the bottom and is under medium tension. The tracking line can be used to position the stretcher out beyond major obstacles such as overhangs during high-angle raisings and lowerings.
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TRAVERSING SYSTEMS (also called TYROLEAN TRAVERSE)
See Reference 4-4 (Reed Thorne: "Offsetting The Technical Evacuation" 1997 North American Technical Rescue Symposium) for a detailed discussion. Reference 4-5 provides detailed illustrations.
A traverse is a technique to cross a river or deep canyon or even to descend a very steep face. Basically, this technique requires a bombproof anchor on both ends with lines strung across. Be aware that tremendous forces can be generated on this system. In general, understanding the physics of placing a load on ropes and anchors for rescue techniques is important; for the highline, it is critical.
Figure 4-12 illustrates a basic highline. The main or track line, a low-stretch 11-mm rope, is anchored on both sides, and the load hangs off this line. The force on the anchors and the rope is a function of the sag in the rope. A table in Reference 4-6 shows the tension generated for various spans, sags, and loads . One revealing example is that for a 100-foot span with a 4-foot sag and a 200-pound load, the tension is 1250 pounds. Since a safety factor of 10 is recommended for such systems and assuming a perfect anchor and a rope strength of 6000 pounds, it is clear that the safety factor is not achieved. A 10-foot sag for a 100-foot span is required to obtain a safety factory of 10. For a 200-foot span, a 20-foot sag is required. Without a load, two people can pre-tension the track line without an MA. A 3:1 Z system with no more than four people pulling should be used to adjust the tension with the rescue load in the middle of the span (see Reference 4-3).
Figure 4-12. Highline Rigging
The safety line, a low stretch 11-mm rope, provides the necessary back-up or belay. The rescue load, consisting of victim, attendant, and stretcher is attached to the track and safety lines with a 2-inch double pulley. The tag lines, 11-mm dynamic ropes, are used for moving the stretcher with victim and attendant across the track line. Both lines should be tied into anchors via tandem triple-wrapped Prusiks and a PMP. Both sides need an attendant to move the tag lines through the Prusik belays. A brake bar and a Z system can be added on either side if a lowering followed by a raising is required.
This highline system uses only one track line, a low stretch 11-mm rope. The tag lines, low stretch 11-mm ropes, are used as belay lines. Figure 4-13 (see Reference 4-5) illustrates the rigging for the track line and tag lines at the anchors on each side.
The track line is tensioned with a 2:1 MA that is attached to the rope with tandem triple-wrapped Prusiks. Use only ONE person to pull for tensioning without a load. Failure to follow this rule could overstress the track line when a load is on the line. With a rescue load hanging from the track line, up to a total of six persons may be used with a 2:1 MA to tension the track line. The tension should be backed off when it is not needed any more to clear obstructions.
The maximum practical length of this highline is 300 feet.
The tag lines are connected to the anchor with tandem triple-wrapped Prusiks and a brake bar on one side and a 2:1 MA on the other side. The two tag lines are attached to the pulley with triple-wrapped Prusiks and a figure-eight. Figure 4-14 (see Reference 4-5) illustrates the rigging. The pulley should be a Kootenay pulley with three holes to attach the stretcher and the two tag lines or a two-inch pulley with a rigging ring or plate clipped into the pulley with a locking carabiner. Each tag line must be secured like a belay line. A person on each end must operate the belay system in complete coordination with each other to make sure that there is never any slack in either tag line.
Figure 4-13. Kootenay Highline System
Figure 4-14. Kootenay Highline Rigging
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4-1. Kenneth N. Laidlaw: "Considerations for Technical Rope Rescue and Introduction of TAC Rope Kit." 11/20/96, www.basarc.org
4-2. John Dill: "Are You Really on Belay?" Response, Summer and Fall 1990
4-3. Padgett, A. and Smith, B. (1998) On Rope: North American Vertical Rope Techniques for Caving, Search & Rescue, and Mountaineering. Huntsville, Alabama: National Speleological Society.
4-4. Reed Thorne: "Offsetting The Technical Evacuation" 1997 North American Technical Rescue Symposium.
4-5. Rick Lipke: Technical Rescue Riggers Guide. Conterra Technical Systems Inc. 1997
4-6. May, W. G. (1973) Mountain Search & Rescue Techniques. Boulder, Colorado: Rocky Mountain Rescue Group, Inc. 301 pp.
4-7. Setnika, Tim J. (1980) Wilderness Search & Rescue. Boston: Appalachian Mountain Club.
4-8. Mountaineering: The Freedom of the Hills, Sixth Edition, 1998. The Mountaineers. Edited by Don Graydon and Kurt Hanson
4-9. Vines & Hudson (1989) High Angle Rescue Techniques. NASAR.
4-10. CMC Rope Rescue Manual.
4-11. Steve Hudson: Myths and Urban Legends of Rope and Prusik Cord Selection
for Rescue. North American Technical Rescue Symposium, Long Beach, CA, November
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On-Line 4/30/99 JGW