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Binary93

Static line - student in tow causes

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Hi,

Just saw this clip of a student hanging on the static line. I'm very interested in all the reasons how this may happen? What are all the things you can do in packing to have this happen? (I'd like to focus my question completely on the packing issues rather than emergency procedures and the insane amount of luck these folks had)

Also, the static line appears to have broken (as we can't see the main canopy), are there any standards for this (that the lines are made to break at some point at some force on purpose)?

 

 

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The static lines themselves are not made to break.  The one in this video is capable of supporting the entire weight of the airplane and its passengers.  This static line did not break -- it is the reason why the jumper is in tow.  It simply failed to release at the main closing loop.  The failure to release is actually kind of hard to do, but the video is not clear enough to see why it failed to open the main container.  The static line only let go when the jumper pulled his reserve while he was still in tow.  (A better procedure for the jumper would have been to ensure the static line was cut before deploying his reserve, which would have allowed for a bit more separation between the inflating reserve and the airplane.)

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In the end the closing loop ripped out of the rig (maybe distorting the plastic in the flap enough for it to do so). The static line stayed intact.

From my 2009 post after it happened at the DZ I was at:

" It is thought that the tab of the static line went into the heavy dacron closing loop from the right instead of the left, which is not normal DZ procedure. [Packer error, not caught by instructor] Still, it was a surprise that the static line actually locked up on itself in some way, rather than just causing a hard pull for a moment while it rotated back to the right orientation. I've never heard of the DZ ever having anything like this happen before in its many years of operation. "

The question of hook knives always comes up. The DZ aircraft 'always' had a hook knife, and the instructor happened to also normally have one. But his got lost the previous week or something, and someone doing maintenance on the plane moved the big hook knife in the plane shortly before. While some will say 'The instructor should have checked for the knife!', it is one of those things people don't check all the time as it was standard DZ equipment on the plane. (Did you check for the fire extinguisher in the airplane the last time you boarded?)




 

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Wrong orientation causing the distortion in the plastic can hypothetically explain it I guess (though I agree, I would expect the jumper to rotate and eventually release the closing loop).

I agree with both the procedure (waiting for the cutting before the reserve) and the hook knife (being "standard piece of equipment"), there's lots of should've-could'ves here.

But what I'm mostly interested in is, aside from closing the rig from the wrong side (with respect to the plane door orientation), are you aware of any other don'ts one should be aware of while packing and checking the equipment to make sure this doesn't happen?

As a side note, it's weird that the static line didn't brake in this concrete occurence because we can't see the main canopy and even though the video is low quality, I'd expect it to be visible.

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The static line was made of some heavy tubular webbing or something like that, good for likely thousands of pounds of load. Note that this was a direct bag static line setup, rather than static line extracting a pilot chute or whatever those systems were like.

The student gear used an SOS system, so when the student pulled the emergency handle, it cut away the main too. The main canopy fell away at some point, rather than staying in the bag at the end of the static line. (What with the odd angles involved, I guess friction on the risers, despite being released at the 3-rings, could have extracted the canopy from the static line bag.)

As for do's and don'ts, the obvious lesson is to close any main container correctly to avoid bad things happening (freefall or static line), and that any 'pin check' (such as by an instructor) look for proper routing of the bridle.

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(edited)

At my dropzone we use the direct-bag system. The staticline has a flex pin connected to it, which goes through the closing loop to lock the container. A flex pin is basically a piece of steel cable, covered in a layer of plastic (so basically a steel wire inside of a plastic hose). 

A few years ago (I think in Poland?)  there were some incidents with tandem gear, where the plastic coating around a flex pin failed. The plastic was partially stripped from the steel, and the whole mess was blocked inside the closing loop, obviously keeping the container closed. This did not end well.

So it seems quite possible to me that a failed flexpin could cause a student in tow, altough I do not know of any cases where this actaully happened. Maybe the closingloop would break in this scenario? I'm not sure. 

This potential problem is why we check the flexpin for damage  during a gear check, just before boarding.

Edited by evh

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Flex pins are the most idiot-proof way to close static-line rigs, but they are not perfect.

When I maintained the gear at a S/L school, I always made sure there were a few spare closing loops and a few spare flex-pins and encouraged packers to replace them at the first sign of significant  wear.

Key point: flex-pins and closing loops are cheap, but airplane tails are expensive.

 

For tools - as important as hook knives - wise operations double-up or triple-up.

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In the Parachute Rigger Handbook is the following image. I'm not 100% sure but I think I saw the yellow 3-ring cables as pins for the static line. Is this something that's okay or something that should be strongly avoided? (I'm not a rigger, just trying to learn)

Thanks!

image.png.79185a06dd0d3ef49f072e516fc4d7fa.png

 

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It's been a while, but my old DZ had two Wings student rigs (purchased new in 03 maybe). S/L, freefall, even had a setup for a reserve side release so it could be used for AFF.

The freefall could be setup as a throw-out or a spring loaded PC ripcord. The ripcords were the black stuff.

The S/L were direct bag, with the pin on the S/L being the black stuff too. 
Not sure if they could be set up as Pilot Chute S/L rigs or not. If they could, we never did. 

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