There is a nice series of comments and pictures posted on the treebuzz site today about a climbing accident while using this type of ascenders. It is similar to the discusions that we encountered recently on our board about back ups for mechanical ascenders. Now I understand why if one side of the ascender fails to grab the rope on this type of set up, the climber takes a ( posibly) fatal fall.
Here is the link for those interested. You may have to copy and past the link in order to make it work.

http://www.treebuzz.com/forum/showflat.php?Cat=0&Number=28587&Main=28524#Post28587

Reading through the treebuzz thread, it appears the accident occured when the climber was footlocking a doubled rope. If I understand this technique correctly there are two ascenders essentially bolted together, each side of the ascender grabs one leg of the rope. If one side of the ascender fails to grab a leg of the rope then the rope slips out of the crotch and drops the climber.

Correct me if I'm wrong in understanding how this rig was set up and failed. Thanks!
-moss

Case in point for a secondary backup!
This is why the norm of having two separate tie-ins to the saddle at or above the waist at all times has been well established by long vertical groups and should be imposed by tree climber groups as well.

As Tom Dunlap suggests in the treebuzz thread, it might be time for arborists to stop using the secured footlock ascending technique and replace it with belayed or backed up SRT.

Note: the secured footlock technique either with a prusik or double ascender holding both legs of the rope is traditionally used by arborists and is not commonly used by rec climbers (as far as I know).

Just so I'm not confusing anyone (I know most of you understand) the secured footlock ascending technique is not the same as the very safe DRT with a Blake's or other friction hitch.
-moss

Moss, You are correct in your description of the accident. If one side of the kong ascender comes off the rope, the rope just comes completely off the TIP branch and the climber drops on the ground ( mostly a fatal fall). This is a clear description of what happened to this guy. There's definitely a need for some type of back up on this type of climbing system. Now, I see why!!!!!!! Ouch!

1. simply tying the ends of the line togather to create a loop MAY have prevented such an accident, as the knot MAY have reached the failed ascender in time to prevent that fall. The root should be examined however to understand why the ascender failed. Could go back to the previous failed ascender discussions...

2. Secured footlock is FAST. I doubt many who use it would trade for SRT techniques as Tom D. suggests unless there are cheap, easy to use, and competitivly fast systems that come on the market. I know it should be safety first, but someone pays the bills too.

Climb Safe!
Icabod

Cam, great suggestion. I can definately see that working, even if you tied just a slip knot at the bottom, it'd be a quick on-quick off way to fix it.

Hmmmmmmmmm

love
nick

Icabob, I was thinking of the same idea of tiying a knot at the bottom of the rope but I do not think that will work for this problem since you will still go all the way down to the grown but you will be traveling in a loop instead of a simple rope. The ideas posted on the treebuzz about having and alternative back up system sounds like the most likely solution. Now I understand why they make competitors use a separate belay rope tied to their back harness in the ISA tree climbing foot lock competition. There have been several of these accidents described before in the treeebuzz site. Read the old postings there for a better background.

No, you won't slide all the way to the ground. The worst that I see happening is that you will ruin either your ascenders or the rope. Picture it in your mind (or better yet, set it up:

Each side of the ascender is holding on to it's side of the rope, the knot is at ground level. You go up, say 30 feet. The left ascender doesn't grab (but the right DOES). The right ascender is pulling the right side down, which pulls the right side up which allows you to descend while at the same time causing the knot to rise up to the left side of the ascender. Because you're in a 2:1 system now, the knot will meet you at the 15 foot level, where the knot will jam below the ascender, bringing it and you to an abrupt and probably uncomfortable stop...the right ascender will still be holding on.

The knot works if only one side grabs.

love
nick

Icabod,
Can you post the knot solution on the Buzz?-- since it's possibly a great solution and I think that it should get to Mark as an idea for his crew to use, even besides the prussik or whatever he said he would have them now employ as a backup.

Also, can you explain why you think SRT is slower than footlock? The only dif. I can imagine is putting on the gear. You still have to set a rope, and I think, ropewalking with a frog system from what I've tried is very fast up the rope.
Thanks.

Nick and Charlieb, You are assuming that the knot is "traveling" up on the side where the ascender is still holding to the rope. The most likely situation is that the knot will be going up on the opposite side ( the one with the failed graving side and the climber will pass the knot going up to the TIP on his way to him hitting the ground. Now if the knot is tied a good distance up from the groung say 10 feet up, then your idea of the loop will apply and the climber may stop 10 feet up in the air. This guy in the accident fall down from about 15 feet high. When you are going up this way( footlocking) it will be very difficult (or somehow dificult) to bend over and tie a knot below your feet, and them continue going up. Let's give it a try and see.

Hmmm, if the rope comes out of one side of the doubled ascender then what Oldtimer says is correct, the knot will keep on going over the tie-in point. If the rope stays in the non-grabbing side of the ascender then the knot will stop the climber's fall assuming the climber is attached to the doubled ascender by a runner. The climber will bring the ascender down with them so the knot will stop the fall whenever it reaches the climber/ascender

It make sense that if the knot catches in the ascender the climber will fall halfway to the ground from where they were when the failure occurred. If the climber is at 40 ft. then 20 ft. down to a hard stop could cause serious injury.

What are the typical heights that working arborists climb with secured footlock? Are they regularly doing 40-60 ft secured footlock climbs? Or do arbos usually switch over to other techniques when the tie-in is over say 50 ft. ?
-moss

Most of the arbos guys/gals that I have seen working go up foot locking they usually have a prussic knot holding them to the rope (both sides) so the problem described above w/ the Kong mechanical ascenders is not an issue. They usually change back to another type of set up while working in the tree using a friction knot like the Blake's or something similar. If the climber falls while ascending foot locking, the prussic grabs both sides of the rope and there is not opportunity for the climber to fall down to the ground. Unless he grabs the rope in top of the prusik in a panic and that is another matter all together. ( A different type of potential accident, which has been disscused in another post before by Joe Maher in one of his Blogs . "On Prusiking" )
Here is the link to that one:
http://www.treeclimbercoalition.org/TreeTalk/article.cfm?articleid=37

1. If the rope is IN the ascender it will stop you half way to the bottom, as the knot will travel in the direction of rope payout.

2. If the rope is not in the ascender then you are truly screwed. BUT, you can prevent this from happening simply by clipping into the top holes as I've previously mentioned here. Clip the bottom too if you think you will put lateral pull on the handles.

3. Somebody send me a link to the thread on BUZZ, I'll send up my solutions, there's too much info there to do a search now-a-days!

Icabod,
The Buzz discussion is at:
http://www.treebuzz.com/forum/showflat.php?Cat=0&Number=28524&an=0&page=0#28524
In an effort to speedily get at least the concept of your solution to Mark for his crew, I posted a simple explanation there already. Please read it and clarify and post other suggestions so Mark can think about them. I hope you don't mind.
Like he said, when these accidents hit close to home then safety becomes the first priority.
Also, could you also explain what you mean by clipping in to the top holes and clipping in to the bottom.
Thanks.