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Offsetting ADD opening Altitudes WAS: Fatality - Cross Keys - 3/25/11

 

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davelepka  (D 21448)

Mar 26, 2011, 10:42 AM
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Offsetting ADD opening Altitudes WAS: Fatality - Cross Keys - 3/25/11 Can't Post

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This is really easy to adjust on a Vigil 2.

It's also easy to adjust improperly. It's also easy to forget to tell your buddy it's been 'adjusted'.

The better idea is to use the default setting, and have that be more appropriate. The need to bump the min pull altitude up does stem from the need for higher AAD activation altitudes, it stems from the openings and speed of modern canopies.

When the AAD standard was set, 750ft at 78mph, Z-po canopies were just hitting the market. The average WL in those days was 1.1 or 1.2 at best.

Things have changed, and the old standard doesn't apply anymore. To toss the idea of a standad aside, and let everyone choose their own thing is dumb. You don't who you're dealing with, what their line of thinking is, or from where they draw their conclusions. You end up with a hodge podge of SOPs, and the inability to train or design gear around them.

The better thought is to modify the standard using the best and brightest minds we have in the sport. Move forward with training and gear designed to work within that standard.


(This post was edited by PhreeZone on Mar 27, 2011, 8:28 PM)


Bolas  (D License)

Mar 26, 2011, 10:59 AM
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Re: [davelepka] Fatality - Cross Keys - 3/25/11 [In reply to] Can't Post

I'm not saying we can't change the factory default, but allow customers the ability to change it if they choose to.

Perhaps leave the min deployment altitude as is, just create and raise a suggested one.


davelepka  (D 21448)

Mar 26, 2011, 12:44 PM
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Re: [Bolas] Fatality - Cross Keys - 3/25/11 [In reply to] Can't Post

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I'm not saying we can't change the factory default, but allow customers the ability to change it if they choose to

You already have the ability to change it, but the intention is for when you take off from one elevation and are jumping over another. You bastardize that feature when you use it for every Tom, Dick or Harry who thinks they know better and want to alter the AGL firing altitude.

In these matters, you create a standard, and build the system around it. Products can be designed to work with that standard, and skydives can be planned around that standard, and everyone is on it.


love2flyhigh  (D 30338)

Mar 26, 2011, 1:09 PM
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Re: [davelepka] Fatality - Cross Keys - 3/25/11 [In reply to] Can't Post

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To toss the idea of a standad aside, and let everyone choose their own thing is dumb.

I couldn't disagree more! The reason is of course, who knows what is going on better then the person using the equipment. If I pulled every time at 3 and had an average of 700 ft opening then why wouldn't I bump up the AAD activation. For me however the 750' mark is totally OK. Knowledge is power and we must continually adjust minimum opening altitudes to our own comfort zone and equipment performance.


Divalent  (C 40494)

Mar 26, 2011, 1:15 PM
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Re: [davelepka] Fatality - Cross Keys - 3/25/11 [In reply to] Can't Post

In reply to:
Quote:
I'm not saying we can't change the factory default, but allow customers the ability to change it if they choose to
...You bastardize that feature when you use it for every Tom, Dick or Harry who thinks they know better and want to alter the AGL firing altitude. In these matters, you create a standard, and build the system around it. Products can be designed to work with that standard, and skydives can be planned around that standard, and everyone is on it.
Okay, so I'm a student, so it is very possible I'm missing something here, but as far as I can tell, the only possible harm I could cause to someone else by programing a different activation altitude is if I lend my gear to someone else, and I don't inform him of that fact, who then pushes the limit and winds up with a 2-out. Is that right?

Because it seems to me that otherwise my choice (if I were so to choose) to have it fire at, say, 1200 ft rather than 750 (or 850, depending on the brand), affects no one. I mean, if I'm aware that I'm at 1200 and hadn't yet pulled, I hope I would be pulling it myself at that point; so it's not like anyone could ever complain I created a danger for them by pulling then, rather than later.

The SIM for group jumps expresses breakoff points relative to the altitude of the person with the highest pull level, so as long at that is that is adhered to, there shouldn't be a problem.

In this incident, (possibly fired when unstable resulting in an unusually slow opening) a higher fire altitude might have made a difference.


fasted3  (D 30104)

Mar 26, 2011, 1:34 PM
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Re: [davelepka] Fatality - Cross Keys - 3/25/11 [In reply to] Can't Post

In reply to:
Quote:
This is really easy to adjust on a Vigil 2.

It's also easy to adjust improperly. It's also easy to forget to tell your buddy it's been 'adjusted'.

The better idea is to use the default setting, and have that be more appropriate. The need to bump the min pull altitude up does stem from the need for higher AAD activation altitudes, it stems from the openings and speed of modern canopies.

When the AAD standard was set, 750ft at 78mph, Z-po canopies were just hitting the market. The average WL in those days was 1.1 or 1.2 at best.

Things have changed, and the old standard doesn't apply anymore. To toss the idea of a standad aside, and let everyone choose their own thing is dumb. You don't who you're dealing with, what their line of thinking is, or from where they draw their conclusions. You end up with a hodge podge of SOPs, and the inability to train or design gear around them.

The better thought is to modify the standard using the best and brightest minds we have in the sport. Move forward with training and gear designed to work within that standard.

I agree with your post. Somebody setting their AAD 1000' higher might think they're safer, but the're not.


Deyan  (D 322)

Mar 26, 2011, 1:41 PM
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Re: [Divalent] Fatality - Cross Keys - 3/25/11 [In reply to] Can't Post

In reply to:
Because it seems to me that otherwise my choice (if I were so to choose) to have it fire at, say, 1200 ft rather than 750 (or 850, depending on the brand), affects no one. I mean, if I'm aware that I'm at 1200 and hadn't yet pulled, I hope I would be pulling it myself at that point; so it's not like anyone could ever complain I created a danger for them by pulling then, rather than later.

Just think about that....Cypres has activation altitude between 750 and 130 ft. If you move the upper altitude,you gonna move the lower as well. And in case of low cutaway and not finding the reserve handle,you are taking away the chance that AAD will start the reserve deployment for you.
If you wanna play with your AAD,do it. Just read the manual before that.

Blue skies


Premier billvon  (D 16479)
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Mar 26, 2011, 2:14 PM
Post #8 of 94 (3251 views)
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Re: [love2flyhigh] Fatality - Cross Keys - 3/25/11 [In reply to] Can't Post

>The reason is of course, who knows what is going on better then the
>person using the equipment.

In general the person who designed the rig/AAD knows a lot more about how their product is best used than the person using the equipment. Examples -

"I'm pulling at 2500 and my dytter flatline is at 2000, so I'll set my AAD to 1800 - if I haven't pulled by then I will definitely need it."

"I have a Vector with a Skyhook, and those things can open a reserve in 50 feet; I've seen it. So I'm going to set my AAD to 300 feet. That gives me a 250 foot margin; that should be plenty."

Now, person #1 will learn pretty quickly that he really doesn't know what's going on. Hopefully the experience will not injure him and he will adjust his firing attitude to a more reasonable number. Person #2 would likely not survive his "learning experience."

Are people really that misinformed out there? Absolutely. Ask ten people at any random DZ how a Skyhook works, how and where an AAD "arms", whether a cypres "decides to fire" etc etc. You'll get some creative answers.

That being said, letting people adjust their own firing altitude away from a default isn't a bad idea, as long as the default is set rather "firmly" (i.e. you really have to want to change it to be able to change it.) Overall that option will help well informed skydivers and harm some poorly informed skydivers. Is that a good thing overall? Perhaps.


popsjumper  (D 999999999)

Mar 26, 2011, 4:20 PM
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Re: [Divalent] Fatality - Cross Keys - 3/25/11 [In reply to] Can't Post

Peter,
The "firing" altitude is not about putting others in danger. It's about putting yourself in danger.


One thought: Some people have had delayed activations because they did not meet the rate-of-descent parameter at 750ft.
If they didn't meet it at 750, they wouldn't have met it at 1000 or higher so there's no benefit to raising the "firing" altitude in a case like that.

There are other situations that would argue against raising it....

More thoughts: Think about what happens when your main snivels through 1000 but opens before 750....both scenarios - activates at 1000, activates at 750.


(This post was edited by popsjumper on Mar 26, 2011, 4:43 PM)


mbondvegas  (A 49817)

Mar 26, 2011, 5:39 PM
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Re: [love2flyhigh] Fatality - Cross Keys - 3/25/11 [In reply to] Can't Post

In reply to:
Quote:
To toss the idea of a standad aside, and let everyone choose their own thing is dumb.

I couldn't disagree more! The reason is of course, who knows what is going on better then the person using the equipment. If I pulled every time at 3 and had an average of 700 ft opening then why wouldn't I bump up the AAD activation. For me however the 750' mark is totally OK. Knowledge is power and we must continually adjust minimum opening altitudes to our own comfort zone and equipment performance.

+1 No need to set new rules for all....just let people choose. The 2K minimum container opening alt....has worked just fine for years. For those (most) who open higher...setting their AAD to +300 offset is an option.


Divalent  (C 40494)

Mar 26, 2011, 6:19 PM
Post #11 of 94 (2914 views)
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Re: [popsjumper] Fatality - Cross Keys - 3/25/11 [In reply to] Can't Post

Okay, I'm willing to learn, but I don't think these two scenarios would sway me. I do think everyone who uses an AAD should both act as if it will fail (so don't rely on it) and act as if it will NOT fail (so expect it to do what it was designed to do), and part of that planning requires knowing the altitude it is going to fire at, and doing things to avoid problems at that altitude. So although I do see you are more likely to get an AAD activation with a snivel following a low main deploy from some fixed altitude, if that happens, you didn't follow your plan. (And had you waited 2.5 seconds longer to deploy your main, then you get a 2-out at 750 ft with the current AADs. Question: if you had a 2-out because you deployed X seconds later (or 500 ft lower) than you planned, would you rather be at 1000 ft or 550 ft?)

Just to be clear, I'm pretty sure I understand the risk, but it seems to me the way to avoiding a 2-out with an AAD is the same regardless of the AAD fire altitude: deploy your main well above that level. It would be foolish to rise your AAD level 450ft and not factor that into your planning.

And the failure to trigger the AAD due to subthreshold descent rate just means that an AAD (regardless of trigger level) isn't going to do anything to save you. However, although the AAD won't help you, the trigger level might! Question: if you notice that you were falling at 60mph under a partial mal 1750 ft below the altitude where you deployed your main, would you rather be at 1250 ft or 750ft?


kuai43  (C License)

Mar 26, 2011, 6:35 PM
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Re: [Deyan] Fatality - Cross Keys - 3/25/11 [In reply to] Can't Post

In reply to:
Just think about that....Cypres has activation altitude between 750 and 130 ft. If you move the upper altitude,you gonna move the lower as well.

Umm... you think that's a problem? If you're happy getting a CYPRES activation at 130 ft., you've got more to worry about.


In reply to:
And in case of low cutaway and not finding the reserve handle,you are taking away the chance that AAD will start the reserve deployment for you.

Say, about 500 ft.?


Not that I'm taking the side of raising the firmware activation altitude of any AAD - first, I believe in altitude awareness - second, I believe in silver.


davelepka  (D 21448)

Mar 26, 2011, 7:03 PM
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Re: [Divalent] Fatality - Cross Keys - 3/25/11 [In reply to] Can't Post

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Just to be clear, I'm pretty sure I understand the risk

Let's be perfectly clear, there's no way you understand the risk.

Consider the number of software revisions to the Vigil. Each one was based on the fact that scenarios the designers had not envisioned or planned for became realities, and units fired when they were not supposed to. In that case, people who were actually building an AAD, and eventaully did market it successfully (and still do), were not aware of ALL the risks.

How about the Cypres? It was good as gold until canopies got fast enough to trick it into firing. Again, nobody ever thought that was a possibility in 1991, but sooner or later it became real enough that Cypres introduced it's first (and only) alternative expert model, the Speed Cypres.

How do those examples relate? Much like the Vigil guys found out, you have to account for EVERY possible situation a jumper could put the AAD in, and make sure it only fires when they really need it. Now if you want to make the AAD firing altitude a regular thing that jumpers adjust for themselves, you cannot just look at what you might do, you have to consider the actions of every jumper who might undertake adjusting their firing altitude. When you think of it in those terms, you can see that what you might do is of no consequence, it's what all the other jumpers might do that you need to account for.

How about the Cypres example? Well, you can't see the problem today, but what developments in skydiving are going to come along in the next 10 years? If you want to make jumper adjustable firing altitudes a regular thing on the DZ, what sort of new circumstances could a jumper devise to trick the AADs into firing at the worst possible moment?

One thing we don't need is another variable in the AAD department. There should be a standard firing altitude, and it should probably be a little higher than it is now. You might have to bump the min pull altitude, but that's more a result of the longer snivels, higher canopy speeds, and tighter reserve containers. Even if you left the AAD firing altitude alone, the current min pull altitude, which was developed in a much different time in skydiving, has seen better days. If you are going to bump it up, you might as well do the same to the AAD firing altitude, and buy yourself a second or two for murphy to rear his ugly head, and still land under a fully inflated reserve.


NexGenSkydiver  (D License)

Mar 26, 2011, 8:00 PM
Post #14 of 94 (2751 views)
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Re: [davelepka] Fatality - Cross Keys - 3/25/11 [In reply to] Can't Post

Why should the minimum deployment altitudes be raised for everyone just because some people want to raise the deployment altitude of AADs? To me, thats like saying we should raise minimum pull altitude because people jump wingsuits and add danger? I personally dont jump an AAD because of the canopies I jump, but that is my personal choice and what I decide is best for me. If you feel it is best to raise your minimum pull altitude then please change that for yourself, not the whole sport.


BlindBrick  (C 35382)

Mar 26, 2011, 8:12 PM
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Re: [davelepka] Fatality - Cross Keys - 3/25/11 [In reply to] Can't Post

In reply to:
In these matters, you create a standard, and build the system around it. Products can be designed to work with that standard, and skydives can be planned around that standard, and everyone is on it.

The thing is there is no standard. Every AAD brand has a different set of firing parameters.

-Blind


Divalent  (C 40494)

Mar 26, 2011, 8:48 PM
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Re: [davelepka] Fatality - Cross Keys - 3/25/11 [In reply to] Can't Post

In reply to:
Quote:
Just to be clear, I'm pretty sure I understand the risk
Let's be perfectly clear, there's no way you understand the risk. ...
I guess I wasn't clear. My statement about understanding the risk was with respect to the specific scenario that Popsjumper raised about getting more 2-outs. I thought the context was plainly evident, as it followed a paragraph specifically addressing that scenario, and the additional words (indeed, the whole paragraph) that followed the fragment of the sentence you quoted immediately dealt specifically and solely with that scenario. (I apologize for confusing you.).

Anyway, I recognize the danger of unintended consequences in any change, whenever made, but that should be a principle that councils caution, not inaction. Since I'm new to the sport, I'd be the last guy to speculate what future techniques, skills, equipment, or disciplines might arise that would lead to new risks with the current generation of AADs. But even if I was prescient enough to know what was coming, the future is not yet here, and as an initial go at considering the issue, vague speculative future possibilities seem less urgent to consider than identifying existing dangers based on what skydivers do today. Which is what Im trying to understand: what is it that jumpers do today that would increase the risks (beyond the benefits) by giving people to option to raise the trigger altitude 500 ft or so.

Maybe Im missing something obvious, or I am overweighing the benefits. Again, the incident this thread is discussing, like some others, might have had a different outcome if the AAD fired higher. Or, perhaps I am underweighing the downsides: I think this is the message I'm getting back from people. If so, I am all ears. Im here to learn. Help me see what I'm missing.


davelepka  (D 21448)

Mar 26, 2011, 9:10 PM
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Re: [BlindBrick] Fatality - Cross Keys - 3/25/11 [In reply to] Can't Post

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The thing is there is no standard. Every AAD brand has a different set of firing parameters

They are all very similar. Within 100ft and a couple mph of each other.

Given that any change would have to be at least 300 ft to be of significance (Bill Both was saying 500ft), the less than 100ft of difference between brands is hardly significant, and they are all essentially the same (which is the definition of 'standard').


Bolas  (D License)

Mar 26, 2011, 9:41 PM
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Re: [davelepka] Fatality - Cross Keys - 3/25/11 [In reply to] Can't Post

If an AAD's primary purpose is still for an incapacitated jumper, consider this:

An incapaciated jumper's AAD fires and the incapacitation is such that the reserve opening does not revive them.

A body slumped under even a reserve will cause it to turn. A canopy not under control can be influenced by wind. In these scenarios, a higher reserve opening may actually be worse as the extra altititude can allow the spin to become faster and/or the canopy more influenced by the wind.

The above assumed normal on heading reserve deployments. Factor in the incapacitated person spinning in freefall and causing line twists, entanglements, etc, and a higher deployment altitude could be even more dangerous.


(This post was edited by Bolas on Mar 26, 2011, 9:42 PM)


captain1976  (D 7183)

Mar 26, 2011, 10:28 PM
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Premier billvon  (D 16479)
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Mar 26, 2011, 10:31 PM
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Re: [captain1976] Fatality - Cross Keys - 3/25/11 [In reply to] Can't Post

>Also to be considered is a Cypress set to fire at 750ft arms itself at 1200
>ft. Raising it 500 ft means its arming close to 1800 ft.

The cypres arms on the way up, not on the way down. Nothing would have to change to move the firing altitude up.


captain1976  (D 7183)

Mar 26, 2011, 10:39 PM
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Re: [billvon] Fatality - Cross Keys - 3/25/11 [In reply to] Can't Post

In reply to:
>Also to be considered is a Cypress set to fire at 750ft arms itself at 1200
>ft. Raising it 500 ft means its arming close to 1800 ft.

The cypres arms on the way up, not on the way down. Nothing would have to change to move the firing altitude up.

I deleted my post until I can verify what I always thought to be factual. But I do think there is an arming altitude at a point above the firing altitude.


(This post was edited by captain1976 on Mar 26, 2011, 10:41 PM)


davelepka  (D 21448)

Mar 27, 2011, 5:13 AM
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Re: [Bolas] Fatality - Cross Keys - 3/25/11 [In reply to] Can't Post

Quote:
Factor in the incapacitated person spinning in freefall and causing line twists, entanglements, etc, and a higher deployment altitude could be even more dangerous.

More dangerous? Than going in without a fully inflated reserve? Not in my book it's not.

As to your 'theory', most canopies will very quickly meet their 'trimmed' airspeed. If that trim dictates a turn of a certain speed, the canopy will meet that within the first revolution or so. So for your theory to be correct, the reserve would have to open just high enough to only allow one revolution at most before impact. Is that how close you want to cut your margins? One revolution of a seven cell reserve in brakes?

Quote:
A canopy not under control can be influenced by wind

All canopies are influenced by wind. Somtimes even those 'under control' cannot overcome the influence of wind, that's when people start backing up or landing off. That influence, however, has nothing to do with turns, just the distance the canopy can fly. In terms of an incapacitated jumper, the odds that the wind will improve or degrade their eventual touchdown point are even. Maybe the wind blows them into a pile of fresh-cut hay, and cushions their landing, maybe it blows them in to a vinyard, and they get impaled on one of those poles the vines grow on.


popsjumper  (D 999999999)

Mar 27, 2011, 7:47 AM
Post #23 of 94 (2397 views)
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Re: [Divalent] Fatality - Cross Keys - 3/25/11 [In reply to] Can't Post

OK, Peter.

If you can guarantee that you are going to deploy a main at altitude X on every jump, then by all means have at it and offset your AAD to fire at (X - "in the saddle") altitude.

I do not recommend that for anyone.


davelepka  (D 21448)

Mar 27, 2011, 8:07 AM
Post #24 of 94 (2377 views)
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Re: [Divalent] Fatality - Cross Keys - 3/25/11 [In reply to] Can't Post

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Im here to learn

Doesn't seem like it. Seems more like you're here to nit pick details and act like a bitch.

I just caught on to ahy Popsjumper keeps calling you Peter, he knows you personally, and is an AFF instructor at your home DZ. With only 19 jumps to your name, I can only assume that you are a student of his, and the fact that you won't seem to accept what he's telling you is how I came to my conclusion above.

There are very few certainties in skydiving. Every time you insert a new variable, there's a ripple effect that sends waves of change through many other areas of your jump. Make it a huge variable, like every jumper personally setting their own AAD firing altitude using their own logic and conclusions, and you greatly multiply the number of chances for those jumpers to be wrong, and for those choices to bite them, or others.

There was an incident where a door popped open in a 182 as it was just clearing treetop height. It seems this caused a rapid change in the cabin air pressure and one (maybe two) Vigil AADs fired. So you have an aircraft at 50 or 100 ft, the door open, and reserve PC flying all over the place. The fact one of them did not get out of the door is just luck, but if it had, there's a fair chance there would have been several fatalities.

This was not a scenario anyone envisioned, or even thought could happen, but it did. Now we know just a hitch more about the Vigil and how it works. Vigil might even create a software 'patch' to cure the problem, but even if they don't, at least we know.

Once you have every jumper independentaly setting their AADs anyway they want, we lose much of what know because it's based on years of expereince working with the AADs as they were designed. They never intended for jumpers to set the firing altitude with respect to AGL to suit their own needs. The entire programming is designed around the default settting.

Beyond all that, you really need to shut your pie hole, and open your ear holes a little more. Like I said above, there are very few certainties in skydiving, so there are very few 1000% correct answers. Anyone can dig and twist and manipulate a situation to prove they are right in some way, but that doesn't mean they are right in most ways, and in skydiving, you have to play the odds.

The odds are that your instructor, and just about everyone on the DZ knows more than you.


(This post was edited by davelepka on Mar 27, 2011, 8:09 AM)


Ron

Mar 27, 2011, 8:23 AM
Post #25 of 94 (2346 views)
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Re: [Divalent] Fatality - Cross Keys - 3/25/11 [In reply to] Can't Post

Quote:
Question: if you notice that you were falling at 60mph under a partial mal 1750 ft below the altitude where you deployed your main, would you rather be at 1250 ft or 750ft?

It does not matter, I can pull the reserve any time I feel like it.

You seem to think you have to wait for the AAD and therefore you want to make it fire higher. The AAD is a back up not part of your procedures.


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