“Drop end 3:1” for crevasse rescue
This article was reviewed by IFMGA Certified Guide Rob Coppolillo, co-author of “The Mountain Guide Manual” and author of “The Ski Guide Manual”. Connect with Rob: @vettamtnguides and his website.
Credit to AMGA Certified Rock Guide Ryan Tilley, who made a video about this method. Kevin Govan @govanathon and Pierre_Gtr @biderchurch also mentioned it to me.
There are two primary systems commonly used for crevasse rescue; the “drop loop C”, and the “Z drag.” While they each have their pros and cons, the drop loop C has become the modern standard. Here's a longer article with pro tips on the drop loop C.
“Drop loop C” - 2:1 mechanical advantage
Pro: Brake knots in the rope don’t interfere with your hauling system.
Pro: You can prepare the crevasse lip to more easily pull out your unfortunate partner.
Pro: Puts the lowest load onto the anchor; (approx 1x your pulling force.)
Con: You usually need to carry at least twice the length of rope that’s between team members to be able to drop a loop. This usually means a two person team needs at least a 60 meter rope.
Con: if the middle person falls in on a 3 person team, this might be a problem, because the end person may not have enough rescue rope to reach them.
“Z drag” - 3:1 mechanical advantage
Pros: You can set up the haul system with a small amount of extra rope. This can allow teams to travel on a shorter rope.
Cons: Pretty much the mirror image of the 2:1 system: Brake knots can cause problems, and the rope often cuts into the lip of the crevasse.
Cons: Puts a larger load on to the anchor, (approx 2x your pulling force.)
However, these aren’t your only options. What if you could combine these systems to get most of the benefits and few of the downsides?
That's what you get with a “drop end 3:1”.
Benefits of the drop end 3:1:
Lets you prepare the lip so the rescue line doesn’t cut into the snow.
Brake knots are not an issue, ignore them.
Gives you more pulling power than a 2:1. (Both systems are easy to convert to a 6:1 if you need too.)
Easily reversible to a lower if needed.
Requires a LOT less rope! No need to have twice the amount of rope between partners, like with a drop loop.
Can be easier to rescue the middle person (that dirty little secret of crevasse rescue that often is not discussed when using a drop loop C.)
Allows a team to use a shorter rope. For a two person team using the drop C method, to maintain adequate spacing, maybe tie 3 or 4 brake knots (which take about 1 meter of rope each) AND for each partner to carry at least twice the length of rope as rescue coils, you pretty much need a 60 meter rope at a minimum. (This is counterintuitive for most people; a two person team needs a 60 meter rope, while a three person team can use a 50 meter rope!)
This also lets a three person team use a shorter rope. For example, you could have a three person team on a 40 meter rope: (11-9-middle-9-11) 9 meters between each climber, and each end person carrying 11 meters of rope.
Allows a greater spacing between climbers with the same length of rope. For example, in an area with large crevasses, a three person team might choose to use a 60 meter rope, and have 14 meters between climbers (16-14-middle-14-16) with this system. With a drop loop C system, you'd need to do at least 20-10-middle-10-20, with 10 meters between each climber, in case of a middle climber fall.
You learn ONE primary system that works in just about every scenario, instead of learning two different systems that may not work in every case and can be confusing to learn and remember, years later, in the heat of battle.
Drop end 3:1 crevasse rescue sequence (team of three):
Unfortunate Climber 1 falls in a crevasse. (The climbers on top remember that Climber 1 has the car keys, so they decide to pull ‘em out.)
Climber 2 (middle) and Climber 3 (end) on top arrest the fall.
Climber 2 builds an anchor and transfers the load by clipping their clip in bight knot to the anchor. Climber 1 is now secure on the anchor.
Climber 3 puts a friction hitch onto the rope to secure themselves, unclips from their clip in knot, and unties their clip in knot.
Climber 3, sliding their friction hitch along the rope to secure themselves, approaches the edge of the crevasse to check on climber 1.
Climber 1 calls up that they want/need to be hauled out.
Climber 3 ties a bight knot in the END of the rope, clips a locking carabiner to it, lowers the carabiner down to climber 1, and tells them to clip the carabiner to their belay loop.
Meanwhile, Climber 2 builds a 3:1 Z drag anywhere that’s convenient, such as on the backside of the bight knot that's clipped to the anchor.
Climber 3 prepares the lip of the crevasse a bit off to one side by carefully knocking off loose snow, and puts their ice axe onto the edge of the crevasse so the rescue rope won’t dig in.
Climber 2 and Climber 3 start hauling, climber 1 gets pulled up.
If this 3:1 for some reason doesn’t give enough pulling power, it's easy to convert it to a (theoretical) 6:1.
Assuming a 3 person team with a 50 meter rope, here’s the process in photos.
The rigging in these photos is compressed into a small area for the demo. In reality this is stretched out over much more rope.
The team is rigged and ready for glacier travel:
The middle person is clipped to the middle of the rope. (Side note: a good rope for glacier travel is a dry treated half rope. One good option is the Sterling Duetto 8.4 mm, which comes in convenient lengths like 30, 40, and 50 meters.)
The lead and end climbers, also clipped to the rope, are about 11 meters away (about 7 full arm spans, for me) either direction from the middle person.
The end climbers carry the extra rope (about 14 meters each) as rescue coils. This gives a rope spacing of 14-11-middle-11-14.
The team has brake knots between each climber to hopefully limit the fall distance. (This is optional for a three person team, but can be a good idea in some situations.)
Whoops, the lead climber (Klimber Kettlebell), falls into a crevasse!
The partners on top arrest the fall. The middle climber builds an anchor and transfers the load by clipping their clip in bight knot to the anchor. The end climber on top secures themselves to the rope with a friction hitch, unties their clip-in knot, and unties any remaining brake knots. This frees up all of the remaining rope (25 meters) to use for a rescue.
On the back side of the connection to the anchor, tie a butterfly knot as a secondary anchor point. This is optional, but has some benefits: it makes an easy-to-clip, uncluttered anchor point, can help keep rope strands from pinching/twisting/crossing, and makes it easy to build a 6:1 mechanical advantage system if you need it later.
Approach the lip of the crevasse carefully, you don't want to knock down a bunch of snow onto your partner. They’re already having a bad day, don't make it worse. Be sure you’re secured to the rope with a friction hitch.
Ask your partner what they need. In this case, let's assume they yell, “Pull me up!”
In the END of the rescue rope, tie a bight knot and clip a locking carabiner to it. Do not lock it.
Lower this locker to your unfortunate partner.
“Drop end”, get it?
Unfortunate partner clips locker to their belay loop and locks it. They are now secure on the “dropped” strand and are ready to be hauled out on this strand.
Prepare the lip of the crevasse.
If you can do this off to the side a bit from your unfortunate partner, that's a good thing.
Knock down loose snow that’s under the rescue strand, and put an ice axe or something similar under the rope so it doesn't cut into the snow. Onto the original strand your partner fell on, secure your axe so it doesn't fall in and get lost. (Securing the axe is not shown in the photo).
Pro tip: if you think you need to rappel into the hole to render assistance, it's easy to add your rappel device with an extension below your friction hitch, which greatly simplifies getting back out of the hole in guide mode. Here's a detailed article on that technique.
Build a 3:1 Z drag haul system with the rescue rope. Use the butterfly knot you tied as the anchor point. You need a progress capture in the system; here I'm using a Petzl Micro Traxion.
Pro tip: dig out a little hole with your hands under the Traxion pulley. This prevents snow/ice from jamming into the toothed cam. =^)
In this example, we assume that the two partners doing the rescue have a Traxion and a pulley to use. Using both of these, you get a calculated mechanical advantage of 2.7 to 1. Not quite a 3:1, but about as good as it gets. Quite a bit better than the calculated mechanical advantage of a drop loop C, which is 1.9 to 1.
Note that in the real world, the friction over the lip of the crevasse will further reduce the actual efficiency any hauling system.
Nice! You’re ready to haul.
Push the “tractor” friction hitch as far as you can toward the edge of the crevasse.
Start pulling on your 3:1. With a 3:1 system, the load on the anchor is two times the force of your pulling. So, keep that pulling force slow and steady by trying to walk slowly and continuously backward, rather than doing a “1,2,3 HEAVE,” type of pull, which can put a higher peak load on the anchor.
As your victim gets close, be sure to check on them often to be sure they don't get pulled up into the crevasse lip.
keep a good eye on them.
Reset the system as needed.
Here's a close-up of the 3:1 Z drag.
If you need more pulling power, it's easy to convert this into a 6:1 system.
There are various ways to do this, here's one that's pretty simple. Add a clove hitch, prusik loop or rope grab onto the pull strand, and clip the backside of the rope coming off of your secondary anchor to this.
You have now have a 2:1 on top of the 3:1, giving you a 6:1 theoretical mechanical advantage. To move the load 1 meter, you need to pull 6 meters of rope through the system.
This puts a load on the anchor of approximately five times the amount of pulling force you’re applying. If you're gonna use a 6:1, be sure your anchor system is as solid as you can make it. If you started with a single buried deadman anchor, you might want to add another one and try to equalize the two pieces.
The calculated mechanical advantage of this is around 4.7 to 1. If you had one additional pulley, you could put it on the purple carabiner, and increase your mechanical advantage to around 5.1 to 1. Friction at every change of direction reduces your efficiency. The more pulleys you can use, the better your efficiency.
Tip to increase pulling efficiency: if you have one pulley, it's best to put it closest to the strand that is getting the initial pulling force. In this case, I moved the pulley from the initial 3:1 friction hitch onto this new rope grab.
Here's a close-up of the 6:1 mechanical advantage rigging, called a “C on a Z”.
We built a 2:1 on top of the 3:1. This is called a compound pulley system. You multiply the two forces together to get a 6:1.
Here, I pretended I was a bit short on gear, so I used a clove hitch on the pull strand. Yes, resetting that means untying and retying, which is a hassle. Any sort of rope grab (prusik, Tibloc, Traxion) works better, but hey, be resourceful and use what you have.
So, that's a look at the drop end 3:1 for crevasse rescue.
It's fast to set up, it's one simple system that you can use in just about any scenario, it requires minimal gear, and you can easily increase it to a 6 to 1 if you need the turbo pull.
Is this “better’ than the drop C? Could the drop end 3:1 become the new standard practice?
Now I get it, there are many different approaches to crevasse rescue and I have no illusions that this is suddenly going to become to go to method. People are very attached to what they’ve learned. But methods evolve, better systems are invented, and it's good to keep an open mind about something that just might work better than the way you're doing it.
Give them both a try and see which one works for you.