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cheneyneel

Re: [cheneyneel] Cypres Investigations???

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.....Oh, and a "cutaway sensor" could be something as simple as a 2-wire connector with a shorting link that is tied to an RSL ring, for example. Very simple, no moving parts.


THE most common failures are with connectors >:(. A pin sliding in and out of a socket is most definitely a moving part.
A solution to this problem may be a small magnet and magnetic field sensor.
Still I don't like this idea, too many fault trees.
Chaos, panic, & disorder - my work here is done

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You can't do that with just a piezo pressure sensor and a timer.



No, you also need a microprocessor and a software program, or a fairly complex analog computer. The result will not be an exact altitude reading, but it will be close enough for acceptable safety margins. It's been demonstrated many, many times by Airtec.



With all respect to Airtec (and I have and use a CYPRES) all the algorithms in the world can't make up for absent information, and the programmers can't forsee every possible scenario. There is a real limit to what can be inferred from a pressure reading and a timer.
...

The only sure way to survive a canopy collision is not to have one.

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Given a change in air pressure, you can extrapolate either a change in orientation or a change in altitude. You can not accurately do both.



Stable falling results in a very constant increase in air pressure. Whereas tumbling should still have that constant increase in the overall smoothed graph, but with a lot of wobbling. I guess the trickiness is that the air speed of the tumbler may be very inconsistent.

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Maybe this is over simplifying things but, How about a second "wire harness" that would go inbetween the cutter and the unit (whatever brand) with a switch that the jumper can activate creating an open circuit to the cutter? A turn on when packing turn off after opening kind of thing.
James

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as discussed in one of the other threads, any additional connections to the cypres are a big hit to reliability. Lot of complexity added for a limited audience.

If you did want an off switch, best would be some sort of remote control and then with an audio confirmation from the unit. If the jumper didn't get it, he wouldn't swoop big.

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If additional connections are a big hit to reliability then design a "swooper" version of the cutter with the additional 2 wires and switch hardwired in. The big problem I see would be the routing of the wires and switch. A remote could be used for this but might increase the size of the cutter to much.
James

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It may be a daft question but wouldn't it be possible to add a second pressure sensor? It could be mounted on the front (MLW?), or a legstrap, giving you two (kindof three) readings - the air pressure at your back, the air pressure at your front and the difference between the two.

If you know that there is a (~300 feet?) difference from clean air to burble readings, you could find an algorithm to cancel out some of that and give a more accurate rate of descent reading allowing for tumbling etc as well as an indication of orientation. That could be factored into a calculation also of whether you had had a "canopy" descent speed for a certain length of time, indicating you had at some point had a good canopy.

Since we shouldn't be relying on an AAD for a low cutaway and if we are cutting away the chances are we are conscious and should be able to pull the reserve for ourselves in that circumstance the unit could work on the basis that once you had a good main out you were on your own. The only problem then would be that the swoop mode unit would be unable to help with lost/stuck reserve handles, stiff reserve pulls etc following a conscious intentional cutaway.

Then again, I know the pressure sensor is one of the bulkier parts of the unit, and I presume one of the costlier component parts which would presumably mean (once you factor in the costs of developing and testing entirely new algorithms) the unit would probably become awkward to fit and wear and expensive to buy for a very specific and limited target market.

So it probably may be more sensible to look along the lines of minimising risk of AAD fire on high-speed canopies by either not using the AAD or not doing manouvres liable to take it outside its tested envelope.

Sweep
----
Yay! I'm now a 200 jump wonder.... Still a know-it-all tho..

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So it probably may be more sensible to look along the lines of minimising risk of AAD fire on high-speed canopies by either not using the AAD or not doing manouvres liable to take it outside its tested envelope.



Ding! ;)

As far as I can tell, this is an issue only affecting the very highest level of performance swoopers. At DZ's all around the world, this issue is catching the attention of swoopers everywhere - but the reality is that most of us are nowhere near the activation speeds required to set it off.

It really is that simple - the kinds of dives where you want a Cypres are not the kinds of dives where you have the altitude to do a multiple rotation setup.

If anyone is doing ludicrously high speed approaches, they can leave the AAD on the ground.

_Am
__

You put the fun in "funnel" - craichead.

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If anyone is doing ludicrously high speed approaches, they can leave the AAD on the ground.


Agreed. I have been quiet on this thread, but...
If someone has the ability to exceed 78mph vertically under canopy, and does it intentionally, the situations that an AAD is designed for is the least likely thing to hurt them. I dont think having a "no-pull", "low-pull" etc is something they are really worried about, considering they are getting really close to freefall speed with a parachute above their head...

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>If someone has the ability to exceed 78mph vertically under canopy, and
> does it intentionally, the situations that an AAD is designed for is the
>least likely thing to hurt them.

I agree. I once talked to Sandy Reid about the problems with designing a Voodoo to accept a VX58 or something and a Teknko 98 reserve. Apparently the cypres took up a lot of room in the packtray. The odds of the jumper being injured or killed by a no-pul vs a landing incident on that rig are pretty astronomical, especially given that many such canopies cannot be taken to terminal.

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I know of no single brand of any piece of skydiving equipment that is superior to competitive brands in all scenarios.

With that in mind, why not just use an FXC Astra instead of a CYPRES if an AAD is required for peace of mind or DZ rules, and high vertical speeds are induced on landing? It is easily switched off under canopy, and requires a slightly higher descent rate, IIRC, than does the CYPRES.

In this particular scenario, FXC appears to have the superior design, of the two.

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Interesting. Looks like airtec changed that website you were pointing to.



No... it's still there. It's the 2nd half of the page which begins with this bolded heading:
"The following text (placed on our website 2004) was totally valid for more than 14 years yet and in respect of the above is still valid for more than 99,9% of all skydivers."
TroyK

"Free your mind, and your ass will follow" - George Clinton

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> It may be a daft question but wouldn't it be possible to add a second pressure sensor?

Or just not make ultra high performance landings with the thing turned on.



A more practical compromise might be a switch that a jumper can trigger once under a good canopy that will increased the software's activation speed.

It's a compromise and the chosen speed will be a moving target but there may be an reasonable upper bound somewhere below terminal that will endure for a while, or even programmable at the jumper's choice.

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If you're going to have a switch, it should be an off switch. And that's complicated enough. Can you sufficently test this alteration before selling it to the few dozen or hundred jumpers that will continue to test it in the real world?

From a low speed cutaway, just going to 100mph costs you another second and 130ft of space. Will you have it?

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>A more practical compromise might be a switch that a jumper can
> trigger once under a good canopy that will increased the software's
> activation speed.

Thus guaranteeing it will not activate if you cut away below 1000 feet and don't deploy your reserve?

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If you're going to have a switch, it should be an off switch. And that's complicated enough. Can you sufficently test this alteration before selling it to the few dozen or hundred jumpers that will continue to test it in the real world?

From a low speed cutaway, just going to 100mph costs you another second and 130ft of space. Will you have it?



If I was a swooper in the danger zone I might.

An on off switch is no less complex to operate than a two mode switch. Tell you what, you can call it an on off switch and make it do what I've described.

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>A more practical compromise might be a switch that a jumper can
> trigger once under a good canopy that will increased the software's
> activation speed.

Thus guaranteeing it will not activate if you cut away below 1000 feet and don't deploy your reserve?



That would depend on your rate of descent when you chop. Turning it off guarantees you'll have no AAD save, having no AAD guarantees no AAD save.

Increasing the descent rate after an initial good openning moves you away from the danger zone for swoop activation (for now) while preserving the value of the AAD under a range of scenarios where disabling it or having no AAD offers no protection.

It's an imperfect world, all options are far from ideal, my suggestion is no different, but it seems like a reasonable compromise if you've already elected to take the extra risks.

P.S. notwithstanding the risk of forgetting to toggle the switch or jumping with it in the wrong configuration. A significant issue, but one where I think a speed toggle is safer than an on/off toggle under all circumstances.

Jumping with no AAD you're not going to forget to turn it off and have an accidental 2 out, that seems like a choice for the jumper. Tie a knot in your slider to remind you :P

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> but it seems like a reasonable compromise if you've already
> elected to take the extra risks.

That's fine. But any such change will have unintended side effects like the one I mentioned. It may well have others; it took 14 years to realize that a cypres can be fired by a descending canopy. Such changes should not be considered lightly, nor should they be considered a 'good compromise' until you find out exactly what the compromise _is_ (which often you won't know until you've done a heck of a lot of testing.)

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Yep, but saying that any idea needs a heck of a lot of testing is easy. Context is important and the alternative scenarios should be weighed in the ballance. People didn't wait all those 14 years to jump with AADs, there were scores of lives saved in the time it took to confirm the anticipated problem with swoop activation.

P.S. I have no sympathy for an argument that says swoop without an AAD while pointing out scenarios where an AAD will not fire if you jump with a modified AAD. That's not an unknown or surprising sidefect, it's merely a "glass is half empty" analysis of one side of the problem.

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Increasing the descent rate after an initial good openning moves you away from the danger zone for swoop activation (for now) while preserving the value of the AAD under a range of scenarios



I'm not understanding why a lower activation speed is necessary prior to deployment than afterwords. If a higher activation speed is used, shouldn't it still be lower than freefall terminal? If so, changing activation speed adds unnecessary complexity; just raise the activation speed throughout the dive. If the higher activation speed is higher than freefall terminal, the whole point is defeated.

Personally, it seems like an awful lot of work to keep from jumping an Astra, which is already well designed for swooping tiny canopies.

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I absolutely agree with your observation, but you can't have the best of both worlds.

All the higher activation speed does is provide an imperfect compromise by reducing the risk of a swoop activation while allowing protection for a range of scenarios that is otherwise unprotected. It definitely eliminates the chance of an AAD save for a number of scenarios, but that's no worse than deactivating an AAD or not jumping with an AAD.

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