digurman 0 #1 August 12, 2003 I'm a new jumper with 40 jumps. I keep reading about people bouncing without the cypress firing. I read the cypres manual and noticed there is not mention of failures, mean time between failure (MTBF), or any of the data that would be found in a manual for other computing devices. As a systems analyst, even the most unreliable equipment I work with has a MTBF of thousands of hours. Why do these jumpers hit the ground without the cypres firing. Is it due to reduced speed from not cutting away partial failures or what? Why doesn't the device fire everytime a person comes down without a main chute open? Words aren't real Quote Share this post Link to post Share on other sites
Yoshi 0 #2 August 12, 2003 *** Why doesn't the device fire everytime a person comes down without a main chute open? *** To my understanding there have been a few cases where the person may have had a prtial canopy out (which could have slowed the person to the point where the cypress would not fire) but was still fast enough to cause fatal damage. -yoshi_________________________________________ this space for rent. Quote Share this post Link to post Share on other sites
Jimbo 0 #3 August 12, 2003 QuoteWhy doesn't the device fire everytime a person comes down without a main chute open? The Cypres isn't a magic bullet, it's an electronic device that is prone to failure (just like every other device on the planet). If you can't get over that then skydiving might not be for you. - Jim"Like" - The modern day comma Good bye, my friends. You are missed. Quote Share this post Link to post Share on other sites
nightjumps 1 #4 August 12, 2003 750ft above ground level at a speed of 78 mph (115ft per second) or more. Quote Share this post Link to post Share on other sites
tictoc 0 #5 August 13, 2003 Quote750ft above ground level at a speed of 78 mph (115ft per second) or more. I don't remember the specs but it was explaned to me and others at the last PIA by airtec that the cypress fires dew th a berometric pressure reading and not 750ft or higher. As you know thies change throut the day. I'm not trying to sound like an ass just trying to convay the way Airetech came acrossed. They didn't seem to be very nice about it.-------------------------------------------------------- Some one must go to the edge for others to be able to find it. But if you go be sure you can make it back. Quote Share this post Link to post Share on other sites
digurman 0 #6 August 13, 2003 I can get over it, Words aren't real Quote Share this post Link to post Share on other sites
sundevil777 93 #7 August 13, 2003 Quotethe cypress fires dew th a berometric pressure reading and not 750ft or higher. As you know thies change throut the day. It adjusts for slow, weather related pressure changes when on the ground. I'm pretty sure it is in the manual. Some have gone in without the cypres firing because they were falling below the threshold speed, others because it was not turned on.People are sick and tired of being told that ordinary and decent people are fed up in this country with being sick and tired. I’m certainly not, and I’m sick and tired of being told that I am Quote Share this post Link to post Share on other sites
nightjumps 1 #8 August 13, 2003 QuoteQuoteQuote750ft above ground level at a speed of 78 mph (115ft per second) or more. I don't remember the specs but it was explaned to me and others at the last PIA by airtec that the cypress fires dew th a berometric pressure reading and not 750ft or higher. As you know thies change throut the day. I'm not trying to sound like an ass just trying to convay the way Airetech came acrossed. They didn't seem to be very nice about it. Whenever the skydiver is on the ground, the unit recalibrates every 30 seconds to handle weather-based changes in atmospheric pressure. QFE (Surface Pressure), is the barometric pressure on the surface. If you set your altimeter to QFE, it will read Zero when you stand on the Runway. The Cypres interpolates that calibrated "barometric pressure" (QFE) and adds 750'. Its the same as if you took your wrist altimeter and set it on "0" just before going up and told it to fire your main on the way down if the needle was traveling between the 3,100' and 3,000' increments at greater than "X" speed within that 100'. Since you're a "Systems Analyst" think of it in terms of an If-Then-Else statement. Does that help? Quote Share this post Link to post Share on other sites
digurman 0 #9 August 13, 2003 Thaks to everyone for the info. Words aren't real Quote Share this post Link to post Share on other sites
apoil 0 #10 August 13, 2003 QuoteI'm a new jumper with 40 jumps. I keep reading about people bouncing without the cypress firing. I read the cypres manual and noticed there is not mention of failures, mean time between failure (MTBF), or any of the data that would be found in a manual for other computing devices. As a systems analyst, even the most unreliable equipment I work with has a MTBF of thousands of hours. Why do these jumpers hit the ground without the cypres firing. Is it due to reduced speed from not cutting away partial failures or what? I don't believe you have interpretted what you have heard correctly. To my knowledge there is NOT ONE SINGLE report of a cypres failing to fire when needed. Sometimes it fires when it isn't wanted. And sometimes the fact that it fires isn't all too helpful because the person under their reserve is in pretty bad shape, or in a really bad spot. However it is an electromechanical device and could conceivably fail. That's part of why it is subject to rigorous testing every 4 years, and retired permanently after 12. Quote Share this post Link to post Share on other sites
digurman 0 #11 August 13, 2003 I think I would code it with an "if then" without an "else" branch. Words aren't real Quote Share this post Link to post Share on other sites
nightjumps 1 #12 August 13, 2003 You may be right, I was thinking: Else; Don't fire. As long as you are good with how to get there, that's what's important. Take Air, Brother. Quote Share this post Link to post Share on other sites
TrickyDicky 0 #13 August 13, 2003 To the best of my knowledge, the expert cypress will fire only with a total or pilot chute in tow, else you're going just too slow. Also remember, if you chop a bad canopy, you have to get up to the firing speed. So from a main mal (streamer, spinning, holes etc) its gonna be a few second before you get up to speed again. Isnt there also a height at which the cypress wont fire cos there's no point; you reserve wont even reach line stretch, 150ft? UK Skydiver for all your UK skydiving needs. Quote Share this post Link to post Share on other sites
slotperfect 7 #14 August 13, 2003 Cypres Misfires IMHO the CYPRES is a VERY reliable device. I don't know which specific incidents you are referring to, but remember that not all jumpers choose to use a CYPRES. There are many threads about that here. My experience with both Airtec (the manufacturer in Germany) and SSK (the authorized US service center) has been very positive. Perhaps you can ask your question about MTBF to them? Cliff Schmucker is your POC at SSK, and Gerard Fetter your POC at Airtec.Arrive Safely John Quote Share this post Link to post Share on other sites
ryoder 1,384 #15 August 13, 2003 Quote Isnt there also a height at which the cypress wont fire cos there's no point; you reserve wont even reach line stretch, 150ft? The Expert Cypres won't fire below 130 feet."There are only three things of value: younger women, faster airplanes, and bigger crocodiles" - Arthur Jones. Quote Share this post Link to post Share on other sites
goose491 0 #16 August 13, 2003 QuoteQuote Isnt there also a height at which the cypress wont fire cos there's no point; you reserve wont even reach line stretch, 150ft? The Expert Cypres won't fire below 130 feet. I don't get it? I mean I understand that you likely wont get to line stretch from this height but why would they actually program a deadline like that at all? Surely, it isn't to save the jumper a repack . Isn't programing a certain height at which it won't fire just asking for problems? (i.e. if it's reading pressure incorrectly for any reason, it might raise that altitude and not fire higher?) I don't get it. I'm such a firm beleiver in the whole "Every bit of drag counts" concept that I'd want it to fire even for the fabric of the reserve pilot chute over my head! And then I'd be pulling my fox racing shirt out from my belly hoping to cup some more air with it.... and flapping it up and down too! My Karma ran over my Dogma!!! Quote Share this post Link to post Share on other sites
pilotdave 0 #17 August 13, 2003 I think they are afraid of misfires due to hook turns. I could be wrong but I think the minimum speed for a cypres to fire is attainable in a dive with a fast canopy. Dave Quote Share this post Link to post Share on other sites
TrickyDicky 0 #18 August 13, 2003 Then why dont we hear of them happening more often? Im sure people have done swoop type manouvers through 750ft before, not coming into land. UK Skydiver for all your UK skydiving needs. Quote Share this post Link to post Share on other sites
Harksaw 0 #19 August 13, 2003 Quotedon't remember the specs but it was explaned to me and others at the last PIA by airtec that the cypress fires dew th a berometric pressure reading and not 750ft or higher The barometric pressure in comparison with the ground barometric pressure is how the Cypres (and all altimeters I've heard of besides GPS) tells whether it is below or above 750 feet__________________________________________________ I started skydiving for the money and the chicks. Oh, wait. Quote Share this post Link to post Share on other sites
tictoc 0 #20 August 13, 2003 Quote The barometric pressure in comparison with the ground barometric pressure is how the Cypres (and all altimeters I've heard of besides GPS) tells whether it is below or above 750 feet I know this. I was simply stating what Cypress told us over and over and over again at PIA. And that is that it is not a foot reading that it goes off of but a pressure reading.-------------------------------------------------------- Some one must go to the edge for others to be able to find it. But if you go be sure you can make it back. Quote Share this post Link to post Share on other sites
lazyfrog 0 #21 August 13, 2003 cypres will not fire if it's not turned on, cypres will fire below ground (or much above) if you set altitude on the wrong side (arrow up or down) cypres will fire but not cut the loop if someone with bad intentions routed the loop outside the cutter ---------- Fumer tue, péter pue ------------- ourson #10, Mosquito Uno, CBT 579 Quote Share this post Link to post Share on other sites
kallend 1,623 #22 August 13, 2003 The device only knows about the local pressure it measures, the rate of change of local pressure, and the calibration pressure it measured when it believed you were on the ground. All else is derived by making some (quite reasonable but not infallible) assumptions. The local pressure measured in your container during freefall can be affected by fall rate, body position and rate of change of body position, container design... all of which variables will affect the device's ability to detect accurately your altitude and fall rate. Then there's partial malfunctions, wing suit jumps, etc. to worry about. So a CYPRES may not fire when you want it to, not because the device is unreliable or has a low MTBF, but simply because the measureable parameters don't meet the firing criteria.... The only sure way to survive a canopy collision is not to have one. Quote Share this post Link to post Share on other sites
Remster 24 #23 August 13, 2003 QuoteNobody expects the Spanish Inquisition Remster Quote Share this post Link to post Share on other sites
billvon 2,400 #24 August 13, 2003 > but why would they actually program a deadline like that at all? Below that height, it is more likely to cause problems due to misfires under canopy than save your life due to a 'correct' fire. Quote Share this post Link to post Share on other sites
billvon 2,400 #25 August 13, 2003 >To my knowledge there is NOT ONE SINGLE report of a cypres failing to fire when needed. Talk to Bryan Burke; he's seen a few failures of the type you describe. One reason they are not reported often is that when the cypres fails it shuts itself down to avoid misfires. People interpret this as "the jumper didn't turn the cypres on" rather than "the cypres failed." Quote Share this post Link to post Share on other sites
