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NiroSwiss

AAD Activation heights

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Was just talking at some ppl at the DZ about AAD and activation heights.

Some (all?) AAD (Expert for example) you can adjust the activation height, as the standard height is set to 750 ft..

--> as between 700 ~ 800 ft sometime is not "enough" or its just to low... Why would someone not set it to lets say 1000 ft or even a bit higher? Just to get some more ft

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A really bad car analogy I like to make:

Think of your AAD as an airbag. It is designed to activate as a last means to save your life when everything else has failed. You do not want your airbag to deploy while you are still 10 meters away from the tree you are about to hit.

The AAD can only measure falling speed and altitude by monitoring air pressure. It cannot predict or correct any other factors that might be in play at the time, which could possibly be made worse by a reserve deploying. Think of examples such as you trying to cut a line of that cutaway baglock which has knotted itself to your left foot.
The AAD firing parameters are set in such a way that the jumpers' time for dealing with the problem is maximised; ~750 ft above ground level is thought to be the absolute minimal altitude at which a reserve could succesfully open - provided the firing parameters are met.

The 'altitude offset' was primarily intended to compensate for difference in heigt (above sea level) between DZ and airfield.
"That formation-stuff in freefall is just fun and games but with an open parachute it's starting to sound like, you know, an extreme sport."
~mom

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This is a long time point of contention. The current trend is toward higher activation altitudes. The three major brands have slightly different defaults.

CYPRES 750 ft
Vigil 840 ft
M2 885 ft

These are the altitudes that older units are set for. DZ offsets are available for all three. But using that to raise activation altitude raises other possible issues. The Vigil uses the altitude correction function both for raising activation altitude of for DZ offset. The other two see this a separate function.

The good news is that all three have newer units with new software that allows the user to raise the activation altitude. Many people are choosing 1000 ft. However, they are also raising their minimum opening altitude. This is the main reason USPA and now CSPA have raised their allowable opening height to 2500 ft.

The downside is a greater chance of a two out situation. Or the end user changing settings and not really understanding all the implications. With increased control over the device people should be increasing their knowledge as well. But people are people.

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NiroSwiss

... Why would someone not set it to lets say 1000 ft or even a bit higher? Just to get some more ft



Because of the possibility of 'scaring' the AAD into firing when you don't want it to.

You have to remember the culture and attitudes back when AADs first came out.

They had a nasty habit of firing when they weren't supposed to.

And people pulled a lot lower than they do today.

So the designers tried to figure out the lowest possible altitude that would still most likely work.
As in, if you haven't pulled by then, you aren't going to. Or if you do it won't matter.

And still, some people pulled low enough, or had long enough snivels, that they were still going fast enough at 750' to fire the AAD and end up with a 2 out. I know one guy who did this a couple years ago, he ended up with the main and reserve tangling into a big ball of crap. There was an instructor in California (San Diego?) who went low after a student and had this happen a month or so ago, ended up with a two out that downplaned at the last second and was injured (it's in Incidents).

Obviously, pulling higher will reduce this danger. I routinely pull at 3k', so I have my CYPRES2 set to 1000. That extra second may (or may not) make some difference if I ever need it.

Other people have different opinions, and set theirs differently.
"There are NO situations which do not call for a French Maid outfit." Lucky McSwervy

"~ya don't GET old by being weak & stupid!" - Airtwardo

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I have a CYPRES and I increased the deployment altitude +200ft. For me personally, it makes a lot of sense. However, everyone must weigh the pro's/con's individually and decide for themselves.

Explanation from my point of view: The USPA lowest opening altitude for C-D license jumpers is 2,500ft (waiver-able 2k). However, C-D licenses used to be able to open at 2k without a waiver. This is probably why AAD makers have the firing altitude set so low.

Why this matters: You want a fair margin between your lowest opening altitude and your AAD firing altitude.

The logic behind my decision: I personally want at least 1000ft margin between my lowest opening altitude and my AAD firing altitude. Since I increased my firing altitude +200ft, that would place my AAD firing altitude somewhere near 950ft instead of 750ft. That allows for an extra 200 feet for my reserve to open in the event of an AAD fire. I like the idea of that!

The argument against increasing your firing altitude: If I open my main below 2000ft and my main takes 1000ft to open, my AAD could fire at 950ft and I could find myself in a "2 out" situation. Not good. However, that scenario should NEVER happen if I follow these rules.

I have a D license and my deployment altitude is somewhere between 3-3,500ft. My decision altitude for my main is 1800ft. If, I am disciplined and deploy by 2500ft, cutaway (if needed) by 1800ft, I should never encounter an AAD fire with a two out scenario; which is really the only potential negative of increasing your activation altitude.
This article addresses the question well.

https://parachutistonline.com/safety_training/ask_a_rigger/aad-activation-altitude

Also, kudos to you for asking the question.
Klaasic

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gowlerk

CYPRES 750 ft
Vigil 840 ft
M2 885 ft



This depends on the orientation of the jumper. Realize that when Vigil says 840 ft they mean as high as 1100 feet if you are falling back-first. I would assume the same applies to the other two as well.

See page 10 http://www.vigil.aero/wp-content/uploads/Vigil-II-users-manual-II.0.6.pdf

page 3 http://www.m2aad.com/download.php?group=download2_soubory&id=101

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lyosha

***CYPRES 750 ft
Vigil 840 ft
M2 885 ft



This depends on the orientation of the jumper. Realize that when Vigil says 840 ft they mean as high as 1100 feet if you are falling back-first. I would assume the same applies to the other two as well.

See page 10 http://www.vigil.aero/wp-content/uploads/Vigil-II-users-manual-II.0.6.pdf

page 3 http://www.m2aad.com/download.php?group=download2_soubory&id=101

Yes indeed. And that is a good example of why people need to read and understand their AAD manual. But almost no one does.

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BobxMarley



The argument against increasing your firing altitude: If I open my main below 2000ft and my main takes 1000ft to open, my AAD could fire at 950ft and I could find myself in a "2 out" situation. Not good.

True, but in expert mode the AADs dont fire unless you're going some 75 MPH or faster. If you pull at ~120 MPH and 1000' later you're still traveling faster than 75 MPH, you have a problem and you may need your reserve anyway. Being that you're below your hard-deck at that point, the only remaining option to slow you down would be to deploy the reserve which is what the AAD would do anyway. Or am I missing something here?

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NiroSwiss

Was just talking at some ppl at the DZ about AAD and activation heights.

Some (all?) AAD (Expert for example) you can adjust the activation height, as the standard height is set to 750 ft..

--> as between 700 ~ 800 ft sometime is not "enough" or its just to low... Why would someone not set it to lets say 1000 ft or even a bit higher? Just to get some more ft



Originally AADs were thought of as totally set and forget. It was a common attitude, at least where I jumped, that if you had a legit AAD save then it was time to quit jumping. You aren't capable of skydiving safely but this way you get to quit instead of die.
I don't think people have that attitude anymore.Some of us still do, but mostly it feels as though it's being seen more and more like just another piece of gear.

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There are 2 main reasons I decided to increase the activation altitude of my Cypres2 to 1050 feet AGL (that is +300 above default setting).

1 - Over the past decade or so, there have been several fatalities (something like a dozen or so) where the AAD fired at the correct altitude, but the reserve failed to open in time to save the person. I have looked, and have been unable to find, any examples of people dying from having a two canopies out situation. That is not to say there aren't any, but it is at least far more rare of an occurrence. I know someone on here will spend hours looking for an example fatality just to say I am wrong. But the fact is that the probability of death from 2 canopies out is FAR less than the probability of dying from the reserve not having enough altitude to open.

2 - The dropzone I jump at the most has a geographical feature nearby that needs to be taken into account. Jump run regularly has jumpers in freefall over a hill that is 300 feet higher than the altitude at the landing area where one typically activates the AAD. If you are in freefall over this hill, which is a very real possibility, and the AAD fires at the correct altitude, you will be 450 feet above the ground. I am not comfortable with that. So adding 300 feet would put me right at 750 above the ground over this hill, and 1050 above the other areas.

Of course I have adjusted my opening altitude and hard deck accordingly.

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It would be nice if you could just enter in a custom altitude and deployment speed. I would like to modify the deployment speed. I think 78 MPH on pro mode for my M2 is way, way higher than I'll ever be going on my large canopy. However, the 45 MPH limit of intermediate mode is a tad slow. I haven't ever hit 45, but I've hit nearly 35 MPH before so it would be nice to be able to enter say 55 MPH. Also, the device activates at only 29 MPH in student mode which seems dangerously low. Even a student doing a few 360s on a large canopy can exceed that speed.

I am curious what orientation the m2 rated altitudes are measured in. It says 885' for pro mode, but is that 885' on your back? If so, what would be the rough translation to being belly-to-earth or while in a spin of some sort?

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faulknerwn

We had a rookie fire a student Mars on a Navigator 200, loaded around 1-1 . He did a 360 apparently around firing altitude. Ended up just trailing the pilot chute behind the rig but it can definitely be triggered.



Yep which seems ridiculous. The intermediate mode activates at 45 MPH I think and at the same altitude as student mode. Is there a scenario where having the AAD on student mode would save someone but putting it on intermediate and increasing the deployment speed to 45 MPH would not save them?

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Is there a scenario where having the AAD on student mode would save someone but putting it on intermediate and increasing the deployment speed to 45 MPH would not save them?



The student mode is designed for a situation where a student has a turning malfunction but is too overwhelmed to cut away. It happens sometimes apparently. Light students under large canopies can easily go slower than 45 MPH when this happens. Using a student AAD with these setting is going to cause too many two outs in my mind though. We do not use student AADs at our DZ for that reason. Others disagree. Again, you have to choose your compromises wisely.

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