Cypres "Misfires"

[petur 0]

A few days ago I stumbled onto an article on Cypres "Misfires" (written in '95). An excerpt from the article, written by the manufacturer (Airtec), follows:
"An altimeter doesn't actually measure altitude, it measures air pressure. It reads air pressure and converts that reading to altitude."
...as does any standard altimiter worn by jumpers...
"AADs have a tough job because the air pressure around a falling jumper varies from one location on his body to the next. If he's falling face to earth, air pressure is higher on his chest and lower on his back."
Knowing that the cypres is a very reliable safety add-on to skydiving equipment, while reading the article I couldn't avoid wondering if wearing a cypres could actually oppose danger to a jumper practising freefly maneuvers. Could a sudden change in position possibly generate a dual malfunction caused by the cypres? Is this something one should worry about?
The article can be found at http://www.pia.com/SSK/cypres/cyp13.htm

[NathanL100 0]

hmmm... I THINK that it can only be a hazard if your humming it in. I've heard that your cypress can be off a few hundred feet, but not thousands. So the only real danger is if you are deploying low and the cypress is off a little and you snivel through the firing range which is something like 800 ft (I think). I wouldn't worry about it because your probably not pulling that low. So yes the cypress can be affected by your burble, but not enough to to deploy your reserve at the altitudes that your talking about.
Blue Ones,
Nathan
A# 39553

[PhreeZone 15]

Misfires are rare, but they do occur. So do worn reserve closing loops breaking...
There have been instances of a cypres firing as the rig was sitting on a picnic table, a few misfires at a couple of grand in altitude but over all they are fairly reliable and don't fire unless you are low... way low...
Cause I don't wanna come back down from this cloud... ~ Bush

[SkydiveMonkey 0]

At the end of the day, a CyPReS is a computer. How many times has your PC had problems? They are reliable, but not infallible.
One tequila, two tequila, three tequila floor

[kallend 1,653]

<<reliable, but not infallible.>>>
Unfair comparison - CYPRES isn't running under Windows.

[SkydiveMonkey 0]

still doesn't mean it won't screw up though.
One tequila, two tequila, three tequila floor

[riggerrob 561]

The most common scenario for a Cypres "misfire" is: buddy tossed his main pilotchute below 2000'.
Main canopy opened really slowly.
He whistled through 1000' in a standup, staring at his slider.
The vertical body position exposed the Cypres (hidden by the reserve container bottom wall) to higher than normal air pressure. The Cypres read this is 750 feet.
The Cypres got scared.
The Cypres told the cutter to cut.
Bottom line is, buddy tossed his main pilotchute below 2000'.
No sympathy here.

[billvon 2,442]

>I couldn't avoid wondering if wearing a cypres could actually oppose danger to a jumper practising freefly maneuvers.
>Could a sudden change in position possibly generate a dual malfunction caused by the cypres?
>Is this something one should worry about?
It could, but it is unlikely. You can apply sanity checks to the data coming from the altimeter, based on certain rules (you can't accelerate at greater than 1G, you can't decelerate at more than 20G's and survive.) If the data doesn't make sense you can reject it. I'm not sure that Airtec uses this filtering algorithm - when I talked to them they wouldn't tell me - but I suspect they do.
Note that when you're below 1200 feet or so, that exact problem often does cause a dual deployment, because even a small error at that point can cause the cypres to think it should fire.
-bill von

[councilman24 36]

The descriptions that have been given over the years at PIA symposia indicates that the Cypres does use a filtering/averaging algorithm. And takes into account the location on the back in the burble. A major part of the product development was the algorithm design. No instantaneous change, especially well above the freefly breakoff of app. 4000' will be enough to meet the firing conditions. Sustained fall on your back might cause it to go off closer to 1000'. But, still if your going that fast at a grand you want it to fire. Also of note, the Cypres has two processors, one doing the main work and one performing diagnostics on the unit.
We'll all get to go out and play with them in 3 years when they start becoming paper weights.

[PhreeZone 15]

On the paperweight..... any one hear if Airtec is going to offer a trade in type program on the units?
Cause I don't wanna come back down from this cloud... ~ Bush

[kallend 1,653]

Landing with 2 out is bad, but with none out is worse.

[AndyMan 7]

Quote

There have been instances of a cypres firing as the rig was sitting on a picnic table, a few misfires at a couple of grand in altitude but over all they are fairly reliable and don't fire unless you are low... way low...

The investigations related to freak misfires - like when it was sitting on the picnic table at Aerohio - ended with the belief that the electronics were picking up electro magnetic interference (EMI) from a cell-phone in use nearby. For a few years following this, Airtec ordere the control units encased in a EMI shield. This usually was a bluish plasic lense the covered the control unit.
Newer units have EMI filters built into the control units, so they don't need the blueish filter. I haven't heard of any of these completely freak misfires since they started installing filters.
However, this is yet another good reason not to take a cellphone onto a jump-plane.
_Am
ICQ: 5578907
MSN Messenger: andrewdmetcalfe at hotmail dot com
Yahoo IM: ametcalf_1999

[GrumpySmurf 0]

Aye, but considering it is built for an embedded environment, I would be willing to wager the Airtec folk stressed the software and hardware to some significant extremes (in terms of temperature, moisture, ESD, pressure fluctuations), in an attempt to confuse the unit and characterize performance. Your PC is actually quite reliable - it's the software that is crap

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[GrumpySmurf 0]

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However, this is yet another good reason not to take a cellphone onto a jump-plane.

Or do what the flight attendants tell you - turn it off

[Engovatov 0]

>QNX only supports the Intel x86/Pentium architectures
Bull. QNX supports x86, PowerPC, MIPS, Super H, ARM, StrongARM, and XScale. Wild guess would be it is a rad-hard version of MIPS in the avionics...

[GrumpySmurf 0]

The only variant I was/am familiar with is QNX 4 for Intel and clones (that is what I was trained on at the QNX office in Kanata) - have they expanded thier line and are starting to moving into the realms of VxWorks and pSos - or was I napping during that seminar several years ago? .

[Engovatov 0]

>or was I napping during that seminar several years ago?
That's more of a recent development - since 6.1: currently supported hardware is listed here: http://support.qnx.com/support/hardware/platform/processors.html
Wonder what they could use on an avionics for version 4? Do not know about F16, but for space apps, even 386 equivalents are fairly recent development (in hardened version) - in military development cycle time frame of course..

[RTB 0]

If you trade in an old Cypres for a new one there will be a small discount. They don't want to offer a large discount because it will seem unfair on those who sold theirs cheaply because they were close to twelve years.
(This information came from Kai Koerner Airtec).
René

[Jussi 0]

"you can't decelerate at more than 20G's and survive"
best i´ve heard that somebody has survived is around 40G´s...
was done by some AF guy really long time ago.. i can´t
remember details, but it was some kind of test on human tolerance on g forces.. iirc, he was sort of banged up after that.. ;)

[AndyMan 7]

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he was sort of banged up after that..

Thats an understatement. If it's the guy i'm thinking of, his eyes were bleeding. picture THAT. He did recover, though.
He was also in a good 7 point harness, which among other things, restrained his head - preventing any neck injuries.
I suspect that with a lesser harness the g-force might've even decapitated him.
_Am
ICQ: 5578907
MSN Messenger: andrewdmetcalfe at hotmail dot com
Yahoo IM: ametcalf_1999

[Jussi 0]

iirc, he never fully recovered..

[GrumpySmurf 0]

Ahh, now I be enlightened. Thanks for the link, I remember them getting the 'peacock feathers' up about them about being used in military hardware, that was back in '98/'99 (when I talked to them last, I've since moved to the land of VxWorks - sadly, not nearly as nice an OS as QNX *sigh* - pretty much requires sloppy programming to deal with OS design flaws, but more work to be found with it and food on the table is a good thing

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[Engovatov 0]

>VxWorks - sadly, not nearly as nice an OS as QNX *sigh* - pretty much requires sloppy programming to deal with OS design flaws, but more work to be found with it and food on the table is a good thing
That to put it mildly.. Do not like VxW at all.. had all sort of problems, especially with compiler support with it for our sattelite platform, but hey - I moved on to nice fat Java/C++ development land instead..
But back to the original topic - do they use any integrated enviroment on Cypres at all? Guess not.. couple of custom coded DSPs should do the trick I think...