Re: [billvon] Conclusion to the fatality at Elsinore June 21, 2008

[popsjumper 2]

Why, yes. I was responding to BillV's Post #21 and re-emphasizd your Post #2.

My reality and yours are quite different.
I think we're all Bozos on this bus.
Falcon5232, SCS8170, SCSA353, POPS9398, DS239

[Bill_K 0]

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Why, yes. I was responding to BillV's Post #21 and re-emphasizd your Post #2.

Well you helped to shape me as a skydiver, what I can say...

Be safe, take care!

[erdnarob 1]

I can just agree that AAD functions are not well understood. Being of an inquisitive nature this is what I know about AADs.
1) Cypres, Vigil, Argus and Astra cut the reserve closing loop when firing conditions occur. Normally you should get a pilot chute launch and then a parachute deployment if the rig is well designed and well packed. The second A of AAD means ACTIVATION not deployment. When I turn the key in my car I activate the engine starter, that does not garanty that the car engine will start running. To do so, you still need a car in good order (batteries, starter, gas, firing system...)

2) Cypres needs to get at 1500 ft or more to arm itself and get ready for firing (firing set up at 750 ft in Expert mode)
3) Argus needs to get at 1400 ft or more to arm itself to get ready for firing (firing set up at 800 ft in Expert or Standard mode)
4) Vigil needs to get at 150 ft or more to arm itself to get ready for firing (firing set up at 840 ft in PRO mode)
5) Astra needs to get at 1700 ft or more to arm itself to get ready for firing (firing seet up at 1000 ft in EXPERT mode)

Speed for firing (coupled with firing set up altitude) to get firing:

1) Cypres 35 m/s or 78 MPH
2) Vigil 35 m/s or 78 MPH
3) Argus 35 m/s or 78 MPH
4) Astra 40 m/s or 89 MPH


If somebody is in a upright position (main starting to deploy or else) and get the firing conditions, since there is no differential pressure anymore between the chest and the back, the AADs (Cypres, Vigil and Argus) will fire 260 ft above the set up firing altitude (firing altitude is only good when falling on your belly). Since the Astra has the pressure sensor in the front (right main lift web) the 260 ft extra doesn't apply when in upright position.

Note: The 260 ft is the altitude equivalent to the difference of pressure between chest and back (when falling on your belly) due to the partial vacuum in your back.

Conclusion: If you are doing a normal jump and if you have to do a cut away below say, 1500 ft expect to get your AAD firing. If it does not fire then you were just at the limit.

Learn from others mistakes, you will never live long enough to make them all.

[ficus 0]

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3) Argus needs to get at 1400 ft or more to arm itself to get ready for firing (firing set up at 800 ft in Expert or Standard mode)

Since you're being exact, the Argus fires at 820 ft (250 m).

[billvon 2,396]

You guys are getting so stuck in the numbers you're missing the bigger picture.

Arguing over 800 vs 820 feet is like measuring the depth of water in your swoop pond and saying "it's 3 feet, 4.1734 inches" and arguing over whether it's 4.1734 inches or 4.1735 inches. After all, if you don't know that, how will you ever set your audible to know when to begin your swoop?

AAD's sense barometric pressure via an analog, temperature compensated silicon sensor. The pressure changes during the day. The temperature compensation isn't perfect, and temperature changes, too. Your rig and freefall position affects what the pressure is (and it's not precisely by 260 feet.) The pilot chute takes time to deploy the parachute, and THAT depends on altitude, descent rate and packing.

All of which means that it is completely pointless to argue over 800 vs 820 feet. It's not even accurate to within 100 feet, much less 20 feet. In most cases, your AAD will open your reserve in time for reserve inflation before impact in freefall. In most cases, it will NOT open your reserve in time for inflation before impact if you cut away around 1000 feet. 1500 feet and you have a shot at getting a good canopy before impact. (Assuming you don't pull the reserve of course.) We can draw these conclusions because we have seen this actually happen in the real world of changing air pressures, inaccurate sensors, changing temperatures and varying deployment speeds.

[xenaswampjumper 0]

What amazes me here is that everyone is going around in circles trying to prove a point. I think that the most important thing to remember is that what happened to Rick is a terrible accident, but it goes to show that anything can happen to anyone at anytime, no matter how good you are, how careful or how many safety devices that you have or don't have!

Statistics are just that, #'s
Anything can happen up there. So arguing over numbers, speed and barometric pressure just seems pointless. The bottom line is you AND YOUR GEAR can do everything right and you can still die..........

till later have fun & love each other seeya mb65johnny gates....
In skydiving, the only thing that stops you is the ground..............
PMS# 472 Muff #3863 TPM#95

[erdnarob 1]

Thanks Ficus for the figure. Billvon, we are on a rigging forum here and any information and precision made are more than welcome. According the latest info on the Argus web site, Ficus is right. Now, as I said, a particular thread can lead to another one more or less related to the original, no cause for panic here.
Now listen to me well, in order to understand fully how the AADs are working you have to understand the following: the 260 ft altitude translating the difference of pressure between chest and (exactely) the inside of the reserve where the AAD is placed (provided the main is still in its container otherwise the aerodynamics changes) when falling on your belly is a figure that has been estimated by all AAD manufacturers in order to designs their devices. That's why when falling on your belly the AADs (Argus, Cypres and Vigil) having their pressure sensors in the electronic box in the reserve container and provided your speed is 35 m/s or higher will fire when they "feel" the altitude of 260 ft higher than your actual altitude (for instance, when falling on your belly and having a speed of 35 m/s or higher, the Vigil will fire when "feeling" the altitude of 1100 ft in your back. At that very moment you are actually at 840 ft (1100 ft - 260 ft = 840 ft all right!). My Vigil 1 dowloaded data confirmed that when I had a low pull at Perris while I was in an uprightt position and my main was beginning to inflate. That was confirmed later by Vigil people after studying my data. In that occasion it was determined that the very beginning of my deployment had been made at 1377 ft. However I agree with Billvon when he says that obviously, all those figures are subject to manufacturing tolerances (plus or minus x ft or y m/s).

Learn from others mistakes, you will never live long enough to make them all.