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CorvusCrypto

Why the cutter on AADs?

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Hey all,

Maybe someone can tell me why AAD manufacturers use a cutter to release the reserve pilot chute.

It seems to me that a cutter would be more likely to fail than, say, a rolling pin design where a pin keeping the closing loop in place were released. Plus cutting through fabric means more replacement and maintenance to ensure proper usage. Thoughts?

PS this came after reviewing a certain series of complaints and issues with the Argus system so now I'm really intrigued by the current AAD cutter designs.
"I would rather be ashes than dust. I would rather be a majestic eagle riding a missile across the sky with sparklers than be an old couch potato." - Jack London (paraphrased)

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In the past this was not the case but when the more modern generation of computerized AAD's came around the cutters were a semi off the shelf technology. It made instillation almost universal. It is imperfect. There has been a lot of discussion about developing a ballistic pin puller. Jump shack has been looking at this. I haven't heard much on it for a while. What I'd seen showed promise but I don't think it was ready as is. He was trying to make it a universal replacement part that could work on any rig and be installed in the field with out any approval from the rig or AAD manufacturers. And the bottom line is that it's just not that simple. You'll have to go back and read the old threads but I still think that a micro puller style design might be the way to go. I liked his inline concept but there is the potential for complications and I don't see it as being readily as universal of a solution as he seemed to think.

Lee
Lee
lee@velocitysportswear.com
www.velocitysportswear.com

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It is all about tolerances while sewing AAD pockets into reserve containers.
First generation Automatic Activation Devices (KAP3, FXC 8000, Sentinel and a dozen military devices) were all pin-pullers.
The primary disadvantage of pin-pullers is the tight tolerances between the grommet and the end of the pin-puller cable housing. The P-P power cable housing usually looks like a spiral-wound ripcord housing and lays parallel with the ripcord housing. If the power cable is anchored too far from the grommet, it pre-loads the ripcord and risks pre-mature activation. OTOH if the power cable is anchored too close to the grommet, it will not pull the pin(s) far enough to open the reserve.

OTOH tolerances are far looser on loop-cutter AADs. If the only thing you do is route the closing loop through the cutter (and leave the rest of the AAD dragging down the taxiway) an electronic AAD will save your sorry ass.

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Consider fashion back when Helmut Cloth was designing the Cypres 1, circa 1990.
Old-school mechanical AADs were big and bulky and had a bad reputation for "miss-firing" below 2,000 feet.
It was embarrassing - for a licensed jumper to wear an AAD.
One of Helmut's original "fashion" goals was to completely conceal the AAD within the container.

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hcsvader

How about instead of something that cuts the closing loop, what about something that releases the closing loop?



.............................................................


Yes.
I have often wondered why AADs didn't release the closing loop from the pack tray. It would be much simpler to build a mon-bloc with both the anchor pin and closing loop passing through the middle. Sewing tolerances would be as loose as tolerances for Cypres pockets.

Down-side, the deeper the loop is released (in the canopy folds and below more flaps) the greater the risks of packing mistakes causing the pilot-chute to hesitate.
We have already seen that an extra-long closing loop can cause a Mirage reserve pilot-chute to hesitate if the loop is squeezed between the raised edges of grommets.

Mirage owners please do not get offended. I was not singling you out for criticism, because I can demonstrate the same partial malfunction on the next dozen single-pin reserves.

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hcsvader

How about instead of something that cuts the closing loop, what about something that releases the closing loop?



This is essentially what I was thinking. You could make something like that in a day or so using basic electronics, a small dc motor, and reserve rip cord with a stainless steel pin (yay scavenging). And it could be sewn in anywhere that is best for the application while also being smaller than cutters. However, like riggerrob said, there is possibility of hesitation. However isn't this possibility going to be the same as with a cutter? The other option would be to have multi loop attachment to act as a splicer, but that's just adding complication.

One benefit outright is that as far as universal application, you could design something like that to work with any AAD.

hmmm.... I shall retreat to my workbench....
"I would rather be ashes than dust. I would rather be a majestic eagle riding a missile across the sky with sparklers than be an old couch potato." - Jack London (paraphrased)

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What makes you think that it would be more reliable than a cutter? It would still fail, it would just have different failure modes. Not saying it's a bad idea in itself, simply that you wouldn't know until you stress test it. But it doesn't seem to be that it would be necessarily better.


Now, if I understand your idea right...
One problem I see, it's simplicity of installation: if you want your device to hold the pin, then it would need to be somehow locked to the bottom of the tray, either by sewing or other methods. This complicate the device installation and removal, and also it would require some work to be retrofitted in existing reserve trays.
One of the nice things of current AAD+cutter design, is that they can be taken in and out in literally a matter of few minutes (beside the normal reserve repack time, of course, that's a different story), with no modification to the container except for the two sleeves for the cables and display and the little pouch for the control unit.
I honestly can't think of a simpler and more effective design.
On the other hand, the fact that I can't think of it, doesn't mean that it's not possible. :D
I'm standing on the edge
With a vision in my head
My body screams release me
My dreams they must be fed... You're in flight.

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I think a chemically activated sealed cutter will be more reliable given 20 years of banging about in a rig, possibly getting damp or wet, being exposed to desert sand and grit.

Also consider the electrical requirements of discharging a chemical reaction (which does the work) or trying to activate a mechanical device to do the work. The cutters are reasonably reliable and have the KISS principle applied well. I think continuing to innovate and improve cutter technology would be best.

-Michael

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I think the current cutter method allows for the maximum force to be applied in the smallest package. Any type of motor or solenoid would take up more space and cause more weight. Motors and solenoids are constructed of metal wire windings to create electromagnets. They also consume a significant amount of electricity compared to a cutter pin that can be fired by a very small amount of electricity.

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Quote

I think a chemically activated sealed cutter will be more reliable given 20 years of banging about in a rig



Chemicals would need to be in an extremely impervious casing. Any exposure to any element would cause decay. And that includes around whatever space around the cutter or the electronics entry port (needed to initiate) into the head.

Also, you cant test them without "firing" them.
Remster

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jumpwally

..thats like saying,," why the handle on the emergency brake ? ".... go skydive....:S



There is no such thing as an emergency brake. It is defined as a parking brake.
People are sick and tired of being told that ordinary and decent people are fed up in this country with being sick and tired. I’m certainly not, and I’m sick and tired of being told that I am

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If you wanted to continue discussing a closing-loop-release, I was thinking in terms of a shallow plate that would slide into existing rigs (Javelin or Vector). The plate would contain most of the electronic "guts" and a semi-permanent pin that the closing loop is tied to.
When you scare the AAD, it retracts the pin, releasing the closing loop.

Both MARRS and FXC have experimented with cutters laying in the pack tray, but eventually decided to use the AAD pockets already provided by Cypres.
A British firm also experimented with a hot-pin AAD that would melt or burn the closing loop when it got scared.

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