Another failure mode of Reverso-style devices?

A few days ago I noticed a situation where I could pull the climber's strand of my ATC Guide (in guide mode) without the device locking at all. Since I haven't read about this particular failure mode, I thought I'd share -- though it may be obvious to some.

The problem occurs if the first of two followers climbs above the belay in such a way that his/her rope runs between the two strands of the other follower's rope, like this (yellow being the first):

If the first's rope is sufficiently tight (not much force required though), the second's rope can run more or less freely, since pulling on it no longer rotates the device into a locking position.

From playing around a bit, I get the impression that things eventually turn out OK in many cases, but not all:

• If the belayer does not keep the first follower's breaking strand tight while the second follower is falling, the friction between the two ropes seems to result in both ropes being pulled through the device a bit. If that loosens the tension on the first's rope, the device can lock after all.
• If the belayer holds on to both breaking strands with one hand, his/her hand will be pulled towards the device by the second's rope running freely. When that happens, it's back to the first case.
• However, if the belayer holds the ropes separately or only holds the first follower's rope (tightly), it seems the device will simply not lock in case the second follower falls.

What do the experts think? Have I missed anything? I will certainly avoid that situation in the future, but I'm still not sure if it is a real danger or not.

but why are your followers above you in the first place? almost by definition they should be coming up from below you.

i could see how this could happen, maybe, but i've never seen it in real life

That's not a "failure mode." It's operator error.

Don't let your follower climb above the belay, period. You can't safely belay a leader in guide mode. So you've got one person free soloing with a rope and another person whose proper belay is being compromised. Just. Don't.

Well done for spotting this. Although no one should be above the belay, I can see this happen if the second pulled up some slack to clove a bolt, or was scrambling up to the trees. 

David Coley wrote: Although no one should be above the belay, I can see this happen if the second pulled up some slack to clove a bolt, or was scrambling up to the trees. 

Yes, exactly. It was a top-out, and my follower was simply a little too quick for me to pay out slack. And obviously, taking a factor 2 fall in guide mode isn't something I'd want to test.

BTW, I guess it will usually only happen when using twin-rope technique. If you clip the ropes separately, you kind of force your followers to solve the problem before arriving at the belay.

Sebastian Reichelt wrote:

Yes, exactly. It was a top-out, and my follower was simply a little too quick for me to pay out slack. And obviously, taking a factor 2 fall in guide mode isn't something I'd want to test.

BTW, I guess it will usually only happen when using twin-rope technique. If you clip the ropes separately, you kind of force your followers to solve the problem before arriving at the belay.

I'm curious to know what your response was at the time?

Señor Arroz wrote:

I'm curious to know what your response was at the time?

X2

The Mountain Guide Manual describes this failure mode.

The manual for the DMM Pivot describes this failure mode in diagram 7. "Braking function may be disabled if the two climber's [sic] ropes are entering the Pivot from different directions."

So don't do that.

Always better to use two guide modes for two followers instead of both through one...

To everyone who got hung up on the word "above": I meant it in a much less literal sense. My mistake. Think about third-class (or so) terrain at the top of a climb.

SethG wrote: The manual for the DMM Pivot describes this failure mode in diagram 7. "Braking function may be disabled if the two climber's [sic] ropes are entering the Pivot from different directions."

So don't do that.

I agree that the text you quote covers it in a general sense, but that diagram actually shows a different failure mode -- one that I think is more widely known. IMHO a big difference is that under normal circumstances it can only fail if both climbers weight the rope. But if the ropes cross in the way I described, much less force is required.

Cor wrote: Always better to use two guide modes for two followers instead of both through one...

While that will prevent the problem shown in the DMM diagram, it probably won't help if the ropes cross.

Thank you mbk, sounds like a book to check out.

Sebastian Reichelt wrote: To everyone who got hung up on the word "above": I meant it in a much less literal sense. My mistake. Think about third-class (or so) terrain at the top of a climb.

If it's 3rd class terrain why was the person walking away while roped up? That seems to be the failure, IMO, not the device design. Even just walking away on 3rd class creates a situation where one rope is in TR mode and the other is "leading." Even though that person doesn't need a belay it's a failure of them for not untying and of the belayer for not alerting them that they need to do that or to just stand by until the 2nd climber reaches the belay.

Señor Arroz wrote:

If it's 3rd class terrain why was the person walking away while roped up? That seems to be the failure, IMO, not the device design. Even just walking away on 3rd class creates a situation where one rope is in TR mode and the other is "leading." Even though that person doesn't need a belay it's a failure of them for not untying and of the belayer for not alerting them that they need to do that or to just stand by until the 2nd climber reaches the belay.

Yes, I agree. (And I never said it was a failure of the device design.)

This is a user error in my opinion.  The device is intended to work when the climbers are below it.

There are two other more subtle failure modes that are mentioned in the manuals but not everyone reads them. If the leader has placed a piece, then traversed to the belay, then there is a risk to the followers.    The first follower takes a fall or hangs on the device after passing the last piece, the device will be locked wide-open for the second  follower. It will not lock. 
 The other failure mode is when the device is not able to move freely into the direction of pull. This is more likely if the leader traversed  right before the belay, but could happen anywhere. Easy to avoid though. When the  leader set up the device he or she should pull all the slack out and verify the direction of pull and verify that is able to freely move inline m without interference. 

Sebastian Reichelt wrote: While that will prevent the problem shown in the DMM diagram, it probably won't help if the ropes cross.

Thank you mbk, sounds like a book to check out.

I'm just saying, use two for two people..  It is inherently safer, and easier to manage.  How you going to lower one of two climbers if necessary with one device...

Props to Sebastian for posting this, especially in view of the inevitable backlash about him allowing it to happen.  If we can get past the contemplation of what terminology to apply (device failure mode or operator error or party incompetence or...)  the fact is that he's showing a dangerous configuration that should be avoided.  That's the point and that should be the end of the story.

But if we are going to wrangle over terminology, when you have a device that is supposed to perform a certain function, and if will fail to perform that function if climbers do something really pretty ordinary, then by god that is a device failure mode in my book.  These forums are full of accounts of device failure modes, some with bad and even fatal consequences, and whenever one of these failure modes manifests itself, we get a chorus of operator error accusations. This happens even when the failure mechanism is unknown, revealng an underlying bias that anything that goes wrong must be the operators fault.

When I listen to these chastisements, I sometimes think my climbing takes place in a different universe than others.  Others seem to function in a place where the ropes are always arranged appropriately, nothing is out of place, and everything is, well, just perfect.  In my climbing world---and after more than 60 years I know a thing or two about efficiency and proper practice---things insist on remaining messy, sometimes unpredictable, occasionaly wrong, very occasionally dangerously so, and, well, just imperfect.  Might a second somehow step up past the belay on easy ground at the top?  Absolutely!

Kyle Tarry wrote:

This is really, really easy to do, you just tie off the climber you don't want to lower with an overhand catastrophe knot on their brake strand.

Yes, but it's more complicated than that.  What if one is injured?  Why not have them separated?

And here is a quote taken from an article about two followers on one auto-block:
"One very important thing to keep in mind is that if one follower falls and locks the device, it will not catch the other follower’s fall. When belaying two followers, you need to tend each rope closely"

So if one falls first, knocks the other climber off (assuming they are both climbing at the same time..) and the belay was already locked for the first one, the second faller is toast.

Something particularly of note for this situation: the operator of the device and the climber making the error are likely two different people. It's not the belayer who is climbing above the anchor, it's the climber.

The climbing community could learn a lot from the airline industry here: analysis of airline accidents showed that prosecuting or publicly shaming airline staff for their mistakes only caused people to hide their mistakes, it didn't prevent mistakes. The FAA now generally tries to cultivate a culture of analysis for future prevention rather than blaming and prosecuting, and the result is that airlines now have processes locked down so thoroughly that there has been only one death in an a domestic commercial airline accident in the last decade (there was 10 years of a perfect record up to 4/17/2018).

What this "operator error vs. device failure mode" argument is really about is blame, which absolutely does not save lives.

Cor wrote:

Yes, but it's more complicated than that.  What if one is injured?  Why not have them separated?

And here is a quote taken from an article about two followers on one auto-block:
"One very important thing to keep in mind is that if one follower falls and locks the device, it will not catch the other follower’s fall. When belaying two followers, you need to tend each rope closely"

So if one falls first, knocks the other climber off (assuming they are both climbing at the same time..) and the belay was already locked for the first one, the second faller is toast.

I'm not sure this follows: if both ropes are in the proper configuration, and no rope is preventing the other from braking itself in the plaquette, how is the second follower subject to the fall hazard? Each strand will lock independently on itself. 

Kyle's catastrophe knot tie-off should be sufficient if the device needs to opened up to lower a follower while belaying a second.

FosterK wrote:

I'm not sure this follows: if both ropes are in the proper configuration, and no rope is preventing the other from braking itself in the plaquette, how is the second follower subject to the fall hazard? Each strand will lock independently on itself. 

Kyle's catastrophe knot tie-off should be sufficient if the device needs to opened up to lower a follower while belaying a second.

Sure.  If you happen to tie off a knot.

But, if both climbers are climbing.  One falls.  Moments later (while the block is loaded) second climber falls, the device will not lock properly.   Set something up at home and try it.   It of course is easier to simulate with skinny ropes.  It might Not screamingly drop the person (although not sure on this) but it does in fact slip, and let rope through.

David Kerkeslager wrote: Something particularly of note for this situation: the operator of the device and the climber making the error are likely two different people. It's not the belayer who is climbing above the anchor, it's the climber...

What this "operator error vs. device failure mode" argument is really about is blame, which absolutely does not save lives.

I think this is a different kind of beast from the airlines. If I'm stupid enough to thread the rope in my Grigri backwards, just for example, and let my climber go 30 feet up the wall at which point they fall off and die because I threaded the rope wrong, that's on me (and them for not checking my device before climbing). It's not a "grigri failure mode."

Any device can be misused. There's nothing totally idiotproof.