crazy

Great move! There are still a few important (IMO) objections and questions not adressed by your new suggestion. The main questions are: - what is the objective? (the trivial "saving lives" is not enough; it should at least be quantified) - do you have any evidence that the proposal is coherent with the objective? (applied to the fatalities in the USA in 2001, the proposal hardly saves any life) - did you seriously consider the possibility of adverse effects? (each time something makes the sport safer, skydivers find new ways to kill themselves) -- Come Skydive Asia

What's wrong with that? Once you have the name of the manufacturer and the website, it's not difficult to get additional info if you want to. On the left side of the screen there are the 2 words "last news". Move the pointer of the mouse over there and press the left button of the mouse. You will get news from ~6 months ago. If you know how to use google, from nervures and Denali, you can easily find parachutes of germany, an other manufacturer of drop paragliders. What else do you need? -- Come Skydive Asia

Nervures -- Come Skydive Asia

Yes and don't forget they also have to pull the freebag past an additional 1 and 2 flaps, respectively. What kind of spring is strong enough to pull the freebag past the flaps? The same as in DZ, the movie? Be careful with these things :-) -- Come Skydive Asia

Is it a pure coincidence that "Open Canopy Fatalities and Cypres saves are almost mirror images of each other from 1994 to 1998, but offset by a year" [Vic Napier, Open Canopies Fatalities][Dave Holmes, The Science of Risk Taking]? If the theory of risk compensation is nonsense, what are the plausible explanations? If there is no known plausible explanation, then the possibility of contra-intuitive and adverse effects of a wingload BSR should not be overlooked. -- Come Skydive Asia

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. 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

I put these in the model, it doesn't change the fundamental result: if you start the swoop with the same angle of attack, smaller canopies will have a longer swoop (but it's not anymore proportional to the size of the canopy). The problem is somewhere else. Defining the model from the angle of attack takes care of these trivialities. Anyway, the stall speed doesn't have so much effect on the length of the swoop because at that point, the large angle of attack induces a lot of drag, decelerating the canopy pretty quickly. The purpose of the model is not to say that the results of empirical experimentation are wrong. The only thing that it can do, at best, is helping in the interpretation of the results. There are empirical results to partly backup the model: the max swooping distance increases approximately linearly with the wingloading, up to 2.2. If it suddenly fails above 2.2 (varies with the canopies and the pilots), it might be because the hypothesis are not true anymore. A very irrealistic assumption is that all swoops start with the same angle of attack. In an ideal world, the pilot would be strong enough to have accurate input on the risers and keep the canopy accelerating and planing out along an optimal trajectory. In the real world, the input is whatever you can, and when there is too much pressure you have to release the front risers. At some point, it's plain impossible to have a near optimal input. Then, the swoop will star slower than the max speed, and this will have a serious impact on the distance: every mph below the max will cost more than 10 feet. Another important thing is that the cool dick points that you get with smaller canopies, start draging on the ground. -- Come Skydive Asia

Apparently, he was asking about the length of the swoop. As i got bored, i took a few minutes to figure out what the theory would say about this. If i didn't screw up (didn't spent too much time to validate the theory), in an ideal world, the length of the swoop is proportional to the inverse of the area of the canopy. A 50 sqft swoops twice longer than a 100sqft. A 10sqft swoops 10 times longer than a 100sqft. My hypothesis: - the lift coefficient is proportional to the angle of attack (Cl = l a) - the drag coefficient has a constant component and a component proportional to the square of the angle of attack (Cd = d0 + d2 a^2) - the coefficients l, d0, d2 are a characteristic of the type of the canopy and are independant of the size - there is no drag from the pilot and the lines - all the canopies start swooping at the same angle of attack and they all stall at the same angle of attack I spare you the equations. The important point is that the coefficient of drag has a component proportional to the square of the angle of attack. This quadratic component is a real killer as soon as the angle of attack is a bit bigger than the optimum, particularly at the beginning of the swoop. It might significantly contribute to explain why most people see the length of their swoops decrease when the wingloading (the speed and responsivity) increases above a given threshold. -- Come Skydive Asia

1) get a realistic evaluation of the actual risk. WL is not. A 0.1 lb/sqft difference on 2 different canopies are not representative of the actual risk. The flight characteristics are. If you don't have the flight characteristics, use the WL but excessively conservative (then the manufacturers will disclose the info). 2) make a realistic evaluation of the individual ability to manage the risk. Those who don't want to actively improve their skills can use the number of jumps but excessively conservatively (then they will get the motivation to get some training if they want to fly faster canopies). I'm talking about real restrictions there (500 jumps to fly above a WL of 1.3, 1000 to get a X-brace and 2000 to exceed a WL of 2.0). Basically, i suggest canopy pilot licences. 4 or 5 different, matching 4 or 5 categories of canopies/WL. It's what you'll find in some places for paragliders, aircrafts, motorbikes, boats... There are many ways to implement such a thing. For instance, open many different options and say that each removes 20-100 jumps from the default (drastic) requirements. A landing injury adds 50-500 jumps. Get a PRO rating you save 100 jumps. Attend a course you save 50 jumps. Win a swoop competition or an accuracy contest, you save 50 jumps. Coach a group of students on spoting, save 20 jumps... The individual ability shouldn't be evaluated only on pilot skills. Obviously, the ability to spot and chose a landing area is as important as the ability to flare properly. Last but not least, to improve the safety, a better understanding of the actual reasons of the accidents. There are quite a lot of other things, apart from WL, and checking carefully the accident reports would probably highlight the fact that there are many ways to prevent landing accidents (hangovers and lack of fitness cost a few femurs each year). But for this, we need proper reports for the accidents. The APF, for instance, logs every single incident, even the most usual malfunctions. -- Come Skydive Asia

I am using an actual example. Someone with 39 jumps called Lisa and tried to buy a sub-100 sq ft canopy a few months back. That's the world we live in now. Fine, there is an example! Assuming that the phone calls were not a troll, do you really think that this is a proper justification for a regulation? Be realistic and check in the fatality reports of the last 5 years, you won't find many 39 jumps wonders at a WL of 2.0. Hardly anything close to this blatant exageration. Besides, even though there were proper justifications for a regulation (i don't deny this), the suggested solution (a table setting the max WL/number of jumps) is not efficient (except if you extend the regulation to 1000 jumps, with extreme limitations), it is a harsh and unfair constraint for a significant number of skydivers, and it doesn't promote any kind of training (except falsification of the logbook). Such a regulation might even lessen the motivation of the canopy pilots willing to improve their skills. That regulation looks particularly arbitrary and inept when you compare with the regulation of other leisure (end even non leisure) activities around the world. There are many examples where the regulation reflects a realistic approximation of the risk, and match it with the individual ability to manage the risk. Skydiving is not like driving cars. It is not a necessity. It is a risk that we are willing to take for our own enjoyment, so, please, before deciding new regulations, make sure that the increase in safety is worth the decrease of enjoyment (if you don't, then a total ban of skydiving is the best regulation). -- Come Skydive Asia

Some time ago i already made similar comments about your analysis, but you never acknowledged the problem. So i ask again: why did you select the year 2002? If you select 2001, the results are very different. From the Us fatalities in 2001, i got: num - jumps - WL (lb/ft^2) - comments # 6 - 4700 - 2.0 - straight in approach, no flare (lost toggle?) #7 - 1 - ?? - backed up ino a hangar #13 - 900+ - 1.5 - low turn #15 - lots - ?? - After a CRW jump, front riser + lost toggle #17 - 40 - 1.1 - low turn to avoid power lines #21 - Experienced - ?? - low turn #23 - 80 - ?? - landing out in steep hills and obstacles #24 - 31000 - 1.4 - canopy collapse #25 - ?? - ?? - a 63 years old guy during a demo jump #31 - 201 - 1.3 - hit a roof, back from a long spot Your rule would apply only to #17 and #31, reducing the WL by 0.1, something insignificant, unlikely to save them. Both cases involve hazards, hence, better training and safer operations would be much more efficient than regulations about WL. 60% of these accidents are experienced or very experienced skydivers. Are you going to ask the USPA to regulate for experienced skydivers as well? In that case, the limit should be less than 1.4 for everybody, just to be on the safe side, right? Even "lost toggles" seems to be a more serious issue than WL in that list. Shall we add mandatory velcro gloves for everybody? 40% (likely 50%) of these fatalities involve hazards. Don't you think that there is something there? Apparently your analysis is biased because your sample is not really representative of the reality. It is based on the data from only one year. If you are that motivated to get the USPA involved (i object strongly on this point), then you should do a bit more homework. Did you check the fatality rates in other countries (apparently you use the fact that other countries regulate, as an argument for the regulation by the USPA). My personal guess is that the rate of landing fatalities is not directly related to the regulation. Denmark has one and also has an average rate of landing fatalities (right?); France has no regulation and a very low rate of landing fatalities (don' go there you'll get a heart attack for the WL and the toggle hook turns). An other objection is that WL is an extremely poor indicator of the risk (you could include the planform factor as well). In addition, when the technology and the training will improve, the values will become outdated and there will be more endless discussions to decide arbitrarily if 1.23 is an appropriate WL for someone with 200 jumps. Proper training, set of mind, and the supervision is way more efficient than arbitrary rules. Define a training program, or a high performance canopy licence, and you will probably get more support (including mine). Well, training programs exist since the mid-90s, so, what we really need is their application. -- Come Skydive Asia

Wow, it's time for you to hang out with a better crowd! I can't believe that your instructors keep you at such a level of misinformation, particularly if it's those who used to sell one of my freefly videos, 2-3 years ago (without my agreement). The truth is that there are some freeflyers here. You can get decent coaching, with briefing, debriefing and video, at least for sitfly. You can also get strong ropes for head down (but you must have a proper sit first). Over the last 2-3 years we worked hard to create a freefly community here and we are 500% succesful (grosfion is not exagerating about the freefly chicks, we are invaded). Don't stay any longer on the Dark Side of the Force. Join us and get some proper fun little Padawan. Say hi on our forum and meet us for our next beer meeting (we can even tell you how to get free flow, twice a month, in Singapore). -- Come Skydive Asia

With less than 100 jumps, it's already good that you have a stable sit. It is normal that your fall rate fluctuates, but you don't necessarily need tons of jumps to fix this. Without a video, it is impossible to know what are your specific problems, but your fall rate varies because the area of your body catching the relative wind varies (i know, it's trivial). You can easily identify and correct the main problems in a few jumps, as long as you have a proper sit. So here are a few very general hints. If you can't keep a constant fall rate, it's either that you are too stiff or too loose, or both (loose legs and stiff shoulders for instance). Stiffness will tend to propagate small changes of position to your whole body. For instance, if your knees and hips are locked, then, when your feet are pushed upwards, your whole body will tend to flip. Looseness will create lots of unwanted moves, particularly in the legs. In both cases you have to improve the control of your joints. The main joints to control are the knees, the hips and the shoulders. To improve the control of these joints, it's better to have a "good" position: a neutral position where you have the maximum mobility, and where you don't waste too much energy to fight against the relative wind. The main points to reach this position, are the legs and the torso. The legs: keep a position half way between standing and squating, with a separation of 2 feet between your knees. It is much more comfortable than sitting in the kitchen chair position, and it provides you a much better control of your legs. Watch your legs and check that they don't move randomly. You need lots of tonicity (but no stiffness), and you have to be extremely reactive to bring them back to the proper position when the relative wind push them away. The torso: make sure that it is upright. A good way to control this is the position of your arms. If you can freely move your arms, particularly upwards and frontwards, then it should be ok. If you can't, or if you lose your balance and fall backwards while trying to do so, you probably have your arms locked behind you, with your torso leaning forward. To correct this, you have to move your legs a little bit backwards (easy from the half-squat position) while you bring your arms forward. Sometimes, all of this is strongly connected, and fixing one detail results in a dramatic improvement of the whole position. For instance, if your arms are locked in your back, moving them forward and raising them will improve your stability, straighten your torso, and improve the control of your legs. Trying other positions (standing, kneeling), and moving your limbs asymetrically might also help you to improve your position. A video and a proper debriefing help a lot. Even a picture can tell a lot (butt lower than the knees, knees together, oblique lower legs...) As you are jumping at a large DZ, it shouldn't be a problem to get this. You might even consider investing in a few coached jumps. -- Come Skydive Asia

I'm wondering why nobody uses this marvelous reefing system for reserves. Cutaway at 100 feet and it snaps open; have a premature opening head down and it opens slowly. Maybe their test pilots have a higher vertical speed while tracking than while arching. Maybe it's what they try to say... However, i can't figure out why the reefing system would care much about the vertical/horizontal thing. Mysteries of physics! Did anybody try to open a cobalt while tracking backwards? -- Come Skydive Asia

130 feet! I hope nobody buys this one. A change of barometric pressure would easily fool the altimeter by 50 feet. Add to this the error of the altimeter, and your AAD is still on when you reach the maximum vertical speed after your hook turn. Yes, and they still have no convincing answer about this. Why should we believe that a cypres won't fire after a hook turn, while it is so easy to set a pro-dytter off? -- Come Skydive Asia

Most people will make a much bigger error in their estimation of 500 feet than 150 feet. Let's say that the error of the pilot is 20%, from 150 feet, this is 30 feet, he can save 15, he impacts to -15 feet, a decent hole. From 500 feet the error is 100 feet, he can save 50 feet, he still impacts to -50 feet, 35 feet deeper. A much bigger hole in the turf. There are efficient recovery methods for this. Teach the technique for recovery first. Once the pilot can still have a nice landing (even a decent swoop) after hooking too high, he won't be tempted to hook too low. if we are lucky, maybe together we hit 50%. -- Come Skydive Asia

for having been injured and unable to steer under my reserve, i definitely don't want to downsize. i had enough control & luck to crash into the peas so it was the best of a bad situation. I agree with you, there are different precautions to prevent being in that situation, but maybe you overlooked the actual risk of landing without any control. How often do you have line twists? You don't need to be injured to be out of control. Line twists are good enough. You load your blade at 2.2, right? Even though you are at the lower end of the recommended wing loading, if one day it starts spinning it might be very fast. you might end quite low with 10 full twists under your reserve. At that point you will have no control at all. you'll spend the next 20-40 seconds kicking like hell to get rid of the twists, while the canopy goes wherever it wants (downwind, trees, building, power lines, road...) I've seen quite a few reserve rides shorter than 40 seconds. Some were even less than 20 seconds. Once, the guy had plenty of time, to clear the twists, after landing. What realistic precautions do you suggest to prevent being in that situation? Do you honestly think you will never be there? Big reserves don't only reduce the impact. They also give more time. -- Come Skydive Asia

I agree, many relevant parameters are quite difficult do define and measure in a standard way, particularly turns. However, the speeds (vertical and horizontal) at full glide and at the minimum sink point and at the stalling point can easily be provided in standard conditions at different wing loadings (no need to be accurate to 0.1%). For most paragliders this kind of info is available: And i guess that this info is also available for the paragliders that you manufacture, right? Anyway, paragliders want to know this information; many of them wouldn't consider buying a canopy without knowing these characteristics. You're right, most skydivers would say "demo". Now, take two average skydivers, let them demo two canopies and ask them to compare them, you'll likely get two very different answers, sometimes contradictory. Looks that how the canopy feels to fly is a very subjective thing. It's not surprising because when we fly a canopy we are really overloaded with inaccurate data. This illustrates subjectivity quite well: You're absolutely right, there are still many people believing that a stiletto 120 is way faster than a sabre 120. Now, even though the airspeed at full glide doesn't change so much, it is still interesting to know which one is faster, which one is slower. It is even more interesting to know the vertical speeds (there there are significant differences) and the stalling point. Maybe you could show the way to your competitors Objective data is way cheaper and way more convenient than demo programs. In addition, without objective data, the skydiving community definitely misses a classification of canopies. Objective data increased significantly the safety and the level of understanding in the paragliding community. Given the increasing number of landing injuries and fatalities among skydivers, it might be time to make the same move. -- Come Skydive Asia

Thanks for your input. As you are involved in many ways in this topic, maybe you can give us more information about the policy of manufacturers (at least your policy), regarding the publication of the flight characteristics. Do you know why it is so difficult (or impossible) to get the basic flight characteristics and performance parameters of skydiving canopies? Why is there such a gap with the paragliding industry (it's much easier to get useful info about the performances of a paraglider)? I personally think it's quite disapointing to get lots of not very useful info about the geometry of a canopy (aspect ratio, span, min & max chord) up to the 3rd digit, while it's impossible to get any info about it's performances, not even the most basic info, such as the speed. It's not only disapointing, it becomes worrying when i consider it at the light of the initial question of this thread: As there is no information available about the performances of the canopies, the match between a given skill level and a canopy is done in the shadow of 2 powerfull blindfolds: wing loading and geometry. Wing loading is a powerful blindfold because two canopies at the same wing loading can have extremely different flight characteristics. Even though it's quite a fuzzy notion (there is not even a standard for the measurements), skydivers still happily discuss wingloadings up to the 3rd decimal while comparing canopies from two different manufacturers (like if there were so many common points between a stiletto at 1.25 and a Xfire2 at 1.22). Same thing for the geometry of the canopy: most modern main canopies are not rectangular, even beginners canopies. Comparing the degree of taper, ellipticity, or whatever planform factor, doesn't help much to figure out the actual performances. The regulation about canopies is in terms of wing loading and canopy geometry. This is really odd because these are very abstract numbers, extremely remotely related to the meaningful information: speed and acceleration. Taper doesn't kill skydivers. High speed impact into the ground does. So, which manufacturer is willing to publish meaningful (quantified) flight characteristics for their products? -- Come Skydive Asia

Why not stick to the relevant and useful parameters? For instance, for a given canopy, with a given size, and a given wingloading: - vertical and horizontal speed at full glide; - minimum vertical speed (and associated horizontal speed); - stalling point; - length of the toggle stroke, from full glide to stall; - turn rate and speeds (vertical & horizontal) with 1, 2 and 3 feet of input; - speeds (vertical & horizontal) and recovery arcs (natural & minimum) after a radical 180 toggle hook turn; - minimum altitude loss in a 360. All of these are easy to measure. How many manufacturers provide this? Why don't they publish this kind of objective performance parameters? -- Come Skydive Asia

If you are talking about collapses, there is an argument against speed. A canopy will collapse because the accumulation point (the point of highest pressure) moves away from the openings in the nose. When this happens, faster means more pressure outside; this means that the canopy will deflate faster. Still about collapses, there might be an argument for slow speeds: the effect of the accumulation point moving to the top skin is much worse than when it moves to the bottom skin. So, it is safer to fly with the accumulation point a bit lower. One way to achieve this is to increase the angle of attack (which reduces the speed). Of course, the limit is the risk of stall. Now, if you are talking about the comfort of the flight (feeling the humps and bumps in turbulences), then you are absolutely right, faster gives a much more even flight. Kind of driving faster on dirt roads to reduce the discomfort of the uneven surface. The speed is more steady because you spend less time in each turbulence. In addition, each turbulence has less effect on the vertical speed because the lift is proportional to the square of the speed. If you fly at 10mph, a gust of +10mph will multiply by 4 the lift of the canopy; if you were initially flying at 30mph, the same gust would multiply the lift by less than 2. -- Come Skydive Asia

That's basic physics. The best way to know is to try it. If you can't wait until your next jump, you can experiment with a rope and a load (let's say 100 lbs). Hang up the load and try to reduce the distance between the load and the anchor point at the top of the rope. If you pull vertically, you have to pull at least 100lbs, else there is no effect at all. On the other hand, as soon as you push on the middle of the rope, you create an angle, hence the distance shortens. For instance, if you push with the same strength that you would need to lift 10lbs, you create an angle of ~6 degrees, this shortens the distance by ~5%. If you push with "50lbs", the distance shortens by ~25%. Back to skydiving, when your canopy recovers from a dive, your apparent weight increases (let's say it becomes 300lbs), and most of the load is on the front risers (let's say 30% on each front riser). If you try to pull straight down, you will do nothing else than hurting your hands as long as you don't pull "90lbs" or more with each hand. However, pushing on the risers, 1 foot above the 3-rings, will easily create an angle of a few degrees. This small angle will shorten the distance between the 3-rings and the bottom of the lines, maybe by 1 or 2 inches. This sounds small, but 1 inch will increase the recovery arc significantly. That's surprising. When you pull on the front risers, you still have the rear risers to hold part of your weight. This force is transmitted to the harness, hence to the leg straps. Even though it's much less than your full weight, it should be significant, like 30-40% of your weight. -- Come Skydive Asia

At this point, rather than pulling vainly downwards on the front risers, push them frontwards. This will be much easier and it will increase significantly the recovery arc. If you were not that high, then you will still have a decent swoop and a soft landing. If you were way too high, just add more input progressively when the canopy slows down. This way, you can easily keep the speed and the dive a bit steeper than the normal glide, hence no surge; you might even still have a decent swoop. Get used to this technique, then you will not be tempted anymore to hook too low. Alternately, you can pull the risers sidewards. Both techniques will distort the front risers, hence reduce the angle of attack (which increases the recovery arc). Pushing frontwards has an additional effect, it also keeps your body further back. -- Come Skydive Asia

whatever the exit order, with 1 freeflyer and 1 belly flyer, the freeflyer opens first (well, i'm sure a smartass can find exceptions). Looks like the exit order is a non-issue on this one. -- Come Skydive Asia

Come on, are you serious? There are quite a few different degrees of being broken. Then, do you have convincing evidences that a square canopy is more forgiving than an elliptical canopy when it comes to a panic turn? As a counter-example, for panic turns, a nitro is more forgiving than a sabre, even though it is a high performance elliptical. First, the toggle stroke is much longer, then, after a toggle turn, the minimum recovery arc is shorter. In addition, it is less likely to stall while trying to dig it out of the dive. Well, if you want to compare canopies, it might be a good idea to compare them at same size and and same wing loading (lengths, areas, and volumes don't scale the same way). Compare the likely outcome of someone doing a panic turn under a safire 120 and under a vx 120. Personally, i don't see any obvious difference (the shorter stroke of the vx is balanced by its better efficiency when it comes to dig it out of the dive). Either the vx is underloaded and it is a tame liner, or the safire is overloaded and it is a killer as well. -- Come Skydive Asia