Kris 0 #26 June 10, 2003 QuoteI believe the cypres manual says that it will not fire below 400 feet. Incorrect. It will not fire below 130' AGL. The information is on page 9 of the user manual.Sky, Muff Bro, Rodriguez Bro, and Bastion of Purity and Innocence!™ Quote Share this post Link to post Share on other sites
markbaur 0 #27 June 10, 2003 QuoteI believe the cypres manual says that it will not fire below 400 feet. My Cypres manual says about the Expert Cypres in section 2.1: "It activates the EOS when it detects a rate of descent higher than 78 mph (35 m/s) [note this is vertical speed, not speed into the relative wind] at an altitutde of apx (sic) 750 feet above ground level (AGL). In the event of a breakaway below this height Cypres will operate down to apx (sic) 130 feet AGL. Below 130 feet AGL opening is no longer useful. For this reason, Cypres ceases operation below apx (sic) 130 feet AGL. Airtec doesn't tell us the algorithm for deciding there is a breakaway, but based on what we know about the rest of the program, it's unlikely to be just a height/vertical velocity calculation. It should be possible to figure out when the initial freefall-to-canopy transition occurs, then to calculate approximate canopy descent rate, and to use that in turn to tell the difference between an acceleration due to canopy maneuver and acceleration due to breakaway. If so, and if Airtec has included such a routine in the software, than a hook-induced Cypres fire would most probably be a mis-fire. Sections 2.2 (Student Cypres) and 2.3 (Tandem Cypres) don't say anything about minimum firing altitudes, although the student section does warn that it's possible to exceed the vertical speed limit of 29 mph with a normal canopy. Mark Quote Share this post Link to post Share on other sites
Watcher 0 #28 June 10, 2003 QuoteSections 2.2 (Student Cypres) and 2.3 (Tandem Cypres) don't say anything about minimum firing altitudes, although the student section does warn that it's possible to exceed the vertical speed limit of 29 mph with a normal canopy. And I have seen it, we somehow ended up with a student cypres in one of our sport rigs when 6 of our cypreses (or however you want to pluralize it) went in for their 4 year check. The jumper induced a front riser turn on a Pro 170 loaded at 1.1:1 and after he did so he felt himself slowing down and sure enough 2 canopies out, as he had fired the cypres off. At which point with the lines clear and the main trying to downplane, the jumper released the main and landed safely. --Jonathan Bartlett D-24876 AFF-I Quote Share this post Link to post Share on other sites
andy2 0 #29 June 10, 2003 [QUOTE]Airtec doesn't tell us the algorithm for deciding there is a breakaway, but based on what we know about the rest of the program, it's unlikely to be just a height/vertical velocity calculation.[/QUOTE] A canopy "swooping" at a speed of 70 mph isn't descending 70 mph at all. A cypres works on altitude, pressure, etc, therefore you'd have to have a pretty steep dive, to get up to 70mph descent rate, right? --------------------------------------------- let my inspiration flow, in token rhyme suggesting rhythm... Quote Share this post Link to post Share on other sites
crazy 0 #30 June 11, 2003 QuoteAirtec doesn't tell us the algorithm for deciding there is a breakaway, but based on what we know about the rest of the program, it's unlikely to be just a height/vertical velocity calculation. Considering the fact that the cypres was probably not designed for modern canopies (i remember a joke 6-7 years ago, about a 43 sqft canopy clocked at 92 mph on a 120 yards long swoop), i'm still wondering why i should believe that their complex algorithm will not misinterpret the data after a steep front riser hook turn. QuoteA canopy "swooping" at a speed of 70 mph isn't descending 70 mph at all. A cypres works on altitude, pressure, etc, therefore you'd have to have a pretty steep dive, to get up to 70mph descent rate, right? When someone is clocked at 90mph, on a 60 degrees dive, then the vertical speed is 78mph (60 degrees is a realistic value). When the canopy planes out, the raw variation of air pressure is likely to overestimate the vertical speed. At this point, there is a problem: the speed is close to the activation speed, and the data is inaccurate. Airtec claims that they solve this problem with a sophisticated algorithm taking into account 7 parameters. Unfortunately, they don't publish the algorithm. They don't even list the parameters (what can they measure apart combinations of air pressure and time?). So, it's not so much about how fast the canopy goes, it's more about Airtec's ability to solve the problem. There were enough test jumps at wingloadings up to 2.5 to show that they did a good job up to this limit (apart that they never explain why a unit shuts down). Above 3.0, who really knows what?-- Come Skydive Asia Quote Share this post Link to post Share on other sites
andy2 0 #31 June 11, 2003 [QUOTE]When the canopy planes out, the raw variation of air pressure is likely to overestimate the vertical speed.[/QUOTE] But by the time it planes out it would be below 130 feet AGL. And as someone said, the cypres is "smart" knowing that a canopy can't descend to 100 feet AGL then bounce back up to 300 (variation in pressure). I thought the problem was +130 feet AGL as you were setting up your "hook" "carve" whatever and building massive speed dropping in. Below 130 feet AGL the cypres wont activate. Correct? --------------------------------------------- let my inspiration flow, in token rhyme suggesting rhythm... Quote Share this post Link to post Share on other sites
Treejumps 0 #32 June 11, 2003 No matter how fast canopies get there will still be a significant diference between a diving turn under canopy and a body accelerating in freefall. For thoese who also base jump this will be more obvious because in base you can feel the true accelration of gravity (33'/sec^2). Under a canopy, even a very small one, lift is being generated, and in a dive the lift being generated would have to be substantial. These forces prevent the pilot from coming even close to the acceleration of freefall. To see for yourself (don't take my word for it) go make a 5 sec freefall from a fixed object, and I'm pretty certain you will notice a big differnce in acceleration from a hook turn. At 2.4 on a VX my time out flat lines regularly. My cypres is removed because its a hassle to take it out to swoop water. Tree Quote Share this post Link to post Share on other sites
raymod2 1 #33 June 12, 2003 QuoteUnder a canopy, even a very small one, lift is being generated, and in a dive the lift being generated would have to be substantial. These forces prevent the pilot from coming even close to the acceleration of freefall. I think you're forgetting the fact that lift is perpendicular to the line of flight. It does not always point up and it does not always oppose gravity. Quote Share this post Link to post Share on other sites
DutchSkyCam 0 #34 June 12, 2003 Question is: Can a Cypres fire on a high performance dive... Answer: A far as I know there has NEVER been a documented cypres fire during a swoop attempt... (don't believe airtec??? If it happened it would have been posted on this forum, the incidents forum, rec.skydiving and lots of other places... WE WOULD HAVE KNOWN). Note: As I understand, most (if not any) swoopers loading their canopies above (say) 2.7 don't have a cypres installed but it has been tested in a fannypack... (they never got it to fire)... Airtec acknowledges that -now, or in the close future- they cannot guarantee a cypres wil not fire in an extreme dive... Make up your own mind, You should be safe up to a wingload of 2.5 (and even higher on larger canopies)... I load my Velocity 103 @ 2.35, the flatline on my pro-dytter goes off at most (if not all) of my landings. I set-up/start my 180/270 deg. swoops between 500 and 700 ft... I have jumped without a Cypres for years, I just installed on again because I don't believe I will descent over 78 mph in a swoop... Barry Quote Share this post Link to post Share on other sites
