Passing the Cypres arming altitude

[manseman 0]

At my DZ, somebody raised a concern that something funny might happen to a Tandem Cypres if the aircraft drops below the arming altitude (900m). This is not a terribly unlikely scenario on a jump run with several static line students. I've read the Cypres manual and can't find anything that suggests that there should be a problem (unless of course the take off elevation or set landing elevation is passed) and I'd just iike some confirmation that sinking back to the arming altitude isn't an issue.

[PhreeZone 20]

I have ridden the plane down with a tandem cypres on my back multiple times with out an issue. What is the potential issue?

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[manseman 0]

I'm guessing that the person who raised the concern in the first place got the impression that the Cypres might disarm itself or something like that if the arming altitude is passed while descending with the aircraft and that this could happen to a Tandem Cypres on a static line jump run. Nobody was confident enough to dismiss the concern.

[jurgencamps 0]

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At my DZ, somebody raised a concern that something funny might happen to a Tandem Cypres if the aircraft drops below the arming altitude (900m). This is not a terribly unlikely scenario on a jump run with several static line students. I've read the Cypres manual and can't find anything that suggests that there should be a problem (unless of course the take off elevation or set landing elevation is passed) and I'd just iike some confirmation that sinking back to the arming altitude isn't an issue.

If you got above the arming altitude, you just have to take care when you get lower again. The cypres is active and it will fire once the firing parameters are reached (altitude and vertical speed). So with a tandemcypres you get in "cypresland" at +2200 ft (1900 ft + a few 100 ft to compensate the burble on your back)
If the plane does not descends fast enough, the cypres will not fire.

[Hellis 0]

Its correct that the Tandem Cypres activates itself at 900 m.
But it will still be activated even if you drop below 900 m, if i understand it correct.
The deactivation altitude on Cypreses (except speed) is 130 feet or ~40 m.
If your static line jumprun drops below 40 m, then yes you have two problems.

[manseman 0]

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But it will still be activated even if you drop below 900 m, if i understand it correct.

Well, this "if I understand it correct" is the problem. I would also guess that this is the case, but I'm looking for information.

[Hellis 0]

Page 11 of the Cypres II manual says

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Like the Expert CYPRES, the Tandem CYPRES
ceases operation below approx. 130 feet (approx.
40 meters) AGL

And to me that means it will stay activated (if you have activated it) untill you reach 130 feet AGL.

[jurgencamps 0]

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But it will still be activated even if you drop below 900 m, if i understand it correct.

Well, this "if I understand it correct" is the problem. I would also guess that this is the case, but I'm looking for information.

It is correct. No need to doubt about it.
The cypres is "ready to go" once you climb above the "arming" altitude. Even if you drop below this altitude, it will stay "armed" and will fire once the firingparameters are reached. It will not fire once you get below 40 m.

[riggerrob 643]

Just another excuse to - follow Strong's advice - not to mix tandems and static-liners on the same load.

Strong's original logic was that S/L students were the most likely to do enough stupid things to deploy a canopy over the tail of the airplane ... and 3,000 feet is too low for a tandem to bail out.

[jurgencamps 0]

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Just another excuse to - follow Strong's advice - not to mix tandems and static-liners on the same load.

Strong's original logic was that S/L students were the most likely to do enough stupid things to deploy a canopy over the tail of the airplane ... and 3,000 feet is too low for a tandem to bail out.

Not only Strong, Relative Workshop/UPT said that to.

[manseman 0]

Yeah, that would definitely be the way to play it safe. And the student doesn't even have to do anything stupid to deploy over the tail if the static line for some reason is too short. Which has happened in the past...

I'll definitely be an advocate for, if possible, not mixing students with tandems and possibly other jumpers as well. At least not without some consideration. Another argument is that on a windy day it's quite possible for a light weight student dropped on a low jump run to still be in the air when the rest of the load gets out att full altitude. But I guess separate student loads are not going to happen when there are two students on the DZ and nobody else wants to go low. And when there's more tandems waiting than we can handle, well, in reality it's never going to be a simple decision.

Unfortunately, safety will probably always be traded for convenience (and money).

Anyway, I did mail Airtech regarding the original question and I did get the expected answer in case anybody else was still not convinced:
"HI Måns,

Your conclusion is absolutely correct, once you pass the arming altitude on climb to altitude, cypres is armed and keeps armed until the landing elevation (+40m ) is reached at end of jump/flight. You can descend into lower than 900m it will remain armed.

Always clean openings,

Jürgen Sennert"

[Hellis 0]

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