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Rustam's avatar

I guess one potential, perhaps not so obvious, source of error which can creep in (even if you start out with correct amount of rope each side):

When John pays out rope, he can't be sure how much of that is (mostly) lowering himself, versus inadvertently (slightly) lowering David... (or vice versa)

If e.g. John is partially lowering David, then John will eventually run out of rope for himself...**

Case A: the rescue guys think David was 75ft up, with 75ft of rope below him, so it seems the rope did actually remain even on both sides. If so, the error was simpler: when David paused/bounced, John lost control and let go of his rope altogether (sliding down to the ground rapidly from 15ft, at which point the end went through his ATC and David went into freefall...)

**Case B: conceivably David was ACTUALLY ONLT AT 60FT HEIGHT, with 75ft of rope below him, because John had accidentally lowered David by 15ft while (mostly) lowering himself (thus giving away 15ft of rope which John needed for himself). Hence, John reaches 15ft above the deck, runs out of rope and "suddenly felt like he was falling"...

So there seems two different possibilities/explanations...

[Apologies if that sounds completely obvious to normal people - my brain started off by dreaming up a complicated source of error (case B - trying to add/subtract 75ft/15ft to look for an uneven rope position somehow) - and went round in circles for 30mins before realising it was most likely the absolutely simplest error - Case A- one guy (for whatever reason) just "let go of the rope", dropping the other guy - but seemslike Case B is worth thinking about...] [I imagine this type of error could creep in if e.g. one climber puts more weight on their feet, stops and starts a bit more, or one is slightly heavier etc]

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