Sit on This: Inverted Fall Harness Test

Here’s my big fall story: It’s 1997. I’m 400 feet up the 2,500-foot southeast face of El Capitan in Yosemite. Climbing alone, with a self-belay, I’m navigating over a loose and sharp section of the wall. Having free-climbed over a precarious flake a few feet taller than my body and about three times wider, I had then clipped a rusty copperhead (an aluminum piece of metal crimped onto a steel wire about as thin as headphone wire), lightly bounce on it and press my hand on the flake for balance. As I’m applying all my weight to the head it suddenly pops out. My hand instinctively catches the flake. I hear a grinding noise, watch the flake peel away from the wall and swoop out of the way.

Now I’m diving, headfirst while the flake follows me down the wall. The pitons I’d placed for protection stayed in place, but the slings I’d tied to them cut over the sharp edges. I kept falling, down, past the belay until the first piece off the anchor, a small cam, arrests my fall. I still remember how firmly the rope tugged on my inverted harness as I headed earthward.

Unhurt but shaken, I rappelled to the ground for the day. At the base was the flake, buried upright in the ground like a guillotine. I was lucky.

Inverted falls are extremely dangerous. This goes for traversing falls as well. Any fall that is not straight up and down leaves the body open for injury. Though all climbing falls pose the risk of injury, when falling inverted it’s not uncommon for serious head injuries or death to occur. On the fall listed above, I was climbing overhanging rock so the risk of hitting a ledge was almost non-existent. But ever since that fall, I have wondered what forces are applied to the harness while falling inverted.

Last autumn I toured a climbing gear factory and testing facility. The name of the factory is withheld from this article to protect the interests of the party. We spent the day attaching several harnesses to an inverted wooden dummy and, with a hydraulic machine, applied force to the harnesses until they failed under the load; a basic inverted fall harness test.

Every harness was more than strong enough to handle the types of forces found in the field when inverted. Massive internal trauma occurs at about 14kN (Kilo-Newton; this unit of force is about 2,800 pounds).

However, they broke at forces lower than during upright tests. This is because the leg loops take essentially zero percent of the load while the waist belt takes the full load while upright.  Of note, all the harnesses had the new auto-locking buckle (commonly called a speed buckle) found on many modern harnesses.

The findings below compare the inverted fail loads with pounds of force on the brands Arc’teryx, Black Diamond, Petzl, Metolius and Singing Rock.

Disclaimer. Inverted harness testing is not a standard test and therefore these numbers are not cross-checked by the manufacturers or the UIAA (the international mountaineering organization with strict safety standards followed by most climbing manufacturers). These harnesses had been used for several months before being tested, which may have slightly weakened them. 

Arc’teryx R320a

The buckle on the Arc’teryx was the smoothest of the harnesses in this test to operate.

The belt slipping leads to an unsteady graph before it outright slips at 7,085 pounds of force (lbf), then is retightened until the webbing slides all the way apart at 9,005 lbs. When it finally broke, the frayed webbing resembled a rat’s nest.

Black Diamond Momentum SA

The webbing broke at the waist belt buckle.It was a clean break, as if the buckle pinched the webbing before it could slip. The graph is slow and steady, until the harness fails at 11,645 lbf.

Petzl Sama 

The webbing broke similarly to the Black Diamond harness. The graph shows a more rapid spike with force until the harness fails at 9,530 lbf.

Metolius Safe Tech Trad

The webbing broke at the buckle, similar to what happened with the Petzl Sama and Black Diamond SA. The graph steadily climbed until the harness broke at 11,780 lbf.

Singing Rock Crux

When force was applied to this harness and it failed, it was the bar tack which extended over the belay loop and connected to the waist loop that broke free from one side. This released the belay loop from the waist belt at 7,415 lbf and sent the full amount of force to the leg loops.

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