crazy

You should say "That *almost* all provides an extra margin of safety". If i understand properly your simplification, for all the cases where the winds at opening altitude are in the same general direction as the jumprun, you actually get less separation than expected. Billvon's "concise definition of exit separation" uses the difference of winds between exit and opening altitude. The formula is accurate and reliable... its application is not, because it relies on a time, computed by somebody, for a given jumprun, then communicated to the whole load. Since there is no visual reference to cross check, i foresee situations where the whole pass would use a completely wrong exit timing, because of improper computation, improper communication, or both. Hence, i'm not sure if the gain in accuracy usually results in more safety. However, it would be a great formula to warn you when your usual simplifications become unsafe. On these very few days, you could change your procedures to keep your extra margin of safety (and get rid of the worrying *almost*). Take the maximum difference of winds between exit altitude and the ground. Then everybody is safe even with high and low openings. -- Come Skydive Asia

I'm not quibbling. I fail to get your logic. The effect of the winds is the same (in drift distance/time unit) on a freefaller and on an open canopy. In addition, the risk of collision disappears as soon as the freefaller is lower than the open canopy. So, i don't really understand how the claim that "the person/group that exited after you is still drifting horizontally during their freefall" is relevant (the open canopy is drifting as well, and it doesn't really matter how much the freefalling group drifts while they are lower than the open canopy). If you could clarify with an example (with numerical values), i would appreciate. Then, the assumption that "they can catch up to you if they did not leave enough separation on exit" is true whatever the opening altitude. Hence, if it is a concern at 5000ft, please explain why it is not a concern anymore at 3000ft. -- Come Skydive Asia

Well, maybe we should clarify which horizontal we are talking about. I was talking about the horizontal at right angle with the vertical. Are you talking about an other one? Or are you assuming that the general direction of freefall is not vertical? So, what is your suggestion about opening altitude? Is it to open lower than the next group? I wish all S&TA would have your progressive views about safety :-) -- Come Skydive Asia

Where is the problem? At opening time, first they will be lower (they are falling much faster) and then they will have plenty of horizontal separation (they will have much less wind drift, something like 20seconds X 50kts = 500 meters). Looks like you spent a lot of time and effort to build a scenario where you think it's a problem to open higher than the next group. Can you spend even more time and more efforts to build a scenario that might convince others? Ok, let's say the next group were belly flyers as well... So, what's the point? they left way too early and didn't give enough horizontal separation. I agree, this is dangerous idiocy. Do you really think that opening lower than the next group generally increases the safety, just in case they would be the 2 seconds separation maniacs? Let me push the reasoning a bit further. if you open 1 foot, 10ft, 100ft, 1000ft or 10000ft higher than them, it doesn't make much difference if they are going to fall through your open canopy. So, lower has to be lower (30ft lower, for the length of the lines and a bit of margin :-). Since they are idiots, they might even forget to pull, which makes them good cypres candidates. So, to be really safe, plan ahead, switch the cypres off, and pull lower than cypres altitude, right? Here, i was optimistic, i assumed someone checked that their cypres is on. Well, there is obviously a flaw in this logic. Apparently, pulling lower than the suspected opening altitude of the next group, just in case they were idiots, doesn't sound like a great idea. So, can we please accept the fact that opening higher than the next group is not a safety violation when it comes to freefallers falling into opened canopies? -- Come Skydive Asia

If the odds of someone falling throught my canopy were high at 4500ft, i doubt they would be significantly smaller at 3500ft anyway (tandems and students open higher than 4500ft; most others lower than 3500ft). Hence, if someone argues that i can't pull high on a bad spot, because of that specific risk, i would point out that there is a serious issue with horizontal separation. Either people rely on vertical separation and this is the safety issue, or they they don't and there is no safety issue about pulling high (well except with the pilot for the quibblers). -- Come Skydive Asia

Besides that "derterment" by itself sucks, specially to control a hobby, the overall ratio "perceived risk"/"actual risk" in skydiving already seems quite high compared to other activities, for instance driving and SCUBA diving. Hence i don't see any reason to increase the fear factor (and the stream of related irrational behaviors). Furthermore, your question implies that doing more is doing better, which is quite a dangerous path when you cope with safety issues. Doing the right thing, and nothing else, is usually much more productive. Now, this is really sick. I don't want to see gory pictures and footages. Most people i know don't want to watch such crap. I don't see why it would deter incidents and accidents; i can even imagine a few thrill seekers who would find some sort of perverse inducement there. I do skydiving for fun, not to watch gross, offensive, disgusting, and revolting material (for this, internet is much better). -- Come Skydive Asia

The suggestion is fine, but i doubt that you'll get any convincing data to back it up. First it will be extremely difficult to collect a reliable and significant set of data, both for the general population, and the swoop competitors. Then, even if you get the data, there is a fair possiblilty that it would be at variance with your belief (competitors might be willing to take more risks than the average skydiver and be more prone to injuries). Advanced canopy control classes might have an effect on the safety of the landings, but there are probably other significant factors to consider, for instance personal risk assesment or fitness. Hence, there might be better ways to promote advanced canopy training than meaningless statistics. -- Come Skydive Asia

I don't know what altitude; it's only a very innacurate guesssimate. I am too busy watching the airspace and the ground, to care about my altimeter. I learned on my own, trying to figure out the "visual guesstimate" of the proper entry altitude for toggle hook turns, through a slow process of trials and errors. 1500 jumps later, my swoops still suck, but i have fun and never had any landing injuries. My opinion is that apart for competitors wannabes, it is useless to know the exact swoop entry altitude. Anyway, flying repeatidly the same exact pattern, with the same exact input, is boring and might have adverse consequences. When the length of the swoop is only a secondary goal, it is safer, more fun, and more productive to use inaccurate visual guesstimates and to experiment with a wide diversity of input. This helps understanding a wider range of inputs, flight characteristics, and techniques to recover gracefully from turns initiated too high or too low. When the length of the swoop is the main goal, then, knowing the exact altitude is necessary to achieve consistent performances. In that case, using an accurate altimeter would definitely accelerate the learning process. -- Come Skydive Asia

Usually works, but this technique can result in a reserve ride. When the pud is released before the PC is inflated, the PC might return into the burble behind the back (specially if for some reason the PC interferes with the bridle). Since the container is open, the deployment bag will happily get out (at least partly), most probably assymetrically because you will be moving your body to have the PC clear the burble. At best, you'll get line twists. I just fully extend the arm away from the body, and the PC is in the airstream. I wait to feel the PC getting pulled out of my hand, but I don't hold the pud too firmly, so my hand is not actually pulled upwards. -- Come Skydive Asia

Now, i'm puzled. I thought that when you can't suppress the jerk off, the main effect is the back and forth propagation of a shake along the device. It would have a very significant effect on hard material, but not on soft material (like soft flesh). -- Come Skydive Asia

'Responsiveness' is still a buzzword. Is a stiletto more responsive than a crossfire2? Ask 10 people, you'll get 10 different answers. Are you considering the 'responsiveness' at full glide or at other flying modes (recovery from a dive for instance). How do you quantify the input? An absolute input (for instance 3 feet of left toggle) or "proportional" input (for instance 70% of the full stroke). One thing is sure: for a given model of canopy and a given wingloading, a smaller canopy will turn faster than the bigger one, from full glide, when you pull 3 feet of left togle on both canopies (because proportionally, it's a bigger input on the smaller canopy). Anyway, the answer to your question is that anyway, if you take two different pilots, the differences of morphology, style, and skills, will make the comparison meaningless. If you take the same pilot and add weight, he might find the bigger canopy less responsive because his arms and risers are still the same length (and there are also strong subjective factors). The article on PD site doesn't say much more than "different sizes have different performances". It doesn't provide any help to quantify or even qualify these differences. -- Come Skydive Asia

I don't know where your proves come from, but there are a few reasons to think that it's exactly the opposite (better lift/drag for the larger canopy; swoop competitors jumping with weight...) -- Come Skydive Asia

Well done! Sounds good and safe... Any idea why a good and safe situation degenerated into a small problem between 3K and 1K? With that wind, you can travel quite a bit, downwind, between 1K and .3K (which is still a conservative altitude for the last turn), particularly with the brakes at 50% on a student canopy. Any idea why at .5K you are still undecided about your landing area? Given this last choice, you definitely made the perfect decision. Congratulations. Any idea why a small problem at 1K degenerated into a situation where you are left with at best one bad solution at 50-100ft? Face planting downwind with 14mph of wind is a serious risk, turning at 50ft is way worse. I know, it's unglamorous, but sliding on your butt might be safer than trying to run (14mph of wind + the speed of the canopy = 20+mph, enough to break an arm, a shoulder, or even the neck) Maybe it's time to talk with your instructor about long spots, flying in brakes, the wind, and alternate landing areas. -- Come Skydive Asia

this is an interesting comment. Now i'm wondering why so many manufacturers are trying to close the nose as much as possible... Just kidding (keeping the nose as close as possible significantly reduces the turbulences generated by the leading edge, specially on the top skin). If i understand their design properly, it is brilliant. The inlet drag is probably only slightly reduced on the bottom skin (a secondary problem), but it is significantly reduced on the top skin because the nose is closed from the bottom. This probably makes a very efficient leading edge. In addition, the bottom skin scoop might lock the accumulation point in front of the very small inlet (might improve the pressurization and reduce the risk of collapse). of course not (it is not x-braced), but it will still help the inlets to keep the proper shape. the x-wing is just a "normal" (not x-braced) high aspect ratio 9 cell, with a very efficient nose, a good airfoil, and a nice trim. A real bomb. Anyway, besides the trivial fact that the slowest generates more lift, it would be interesting to know why the rage goes faster. The airfoil of the rage is at least as efficient as the airfoil of the x-wing; hence, either it is significantly thinner, or the angle of attack is significantly smaller (or both). In both cases, a superior design of the nose helps a lot. I'm wondering why they don't produce it in small sizes. -- Come Skydive Asia

How do you jump from "rotate more then 90 degrees" to "somewhat hard openings much harder"? I agree that if the human body was rigid, there would probably be a higher angular velocity. However, considering the fact that the human body is flexible, the "more than 90 degrees" implies that the body will flex more, which is likely to reduce the angular velocity, and improve the absorption of the opening shock. In addition, I'm wondering if the effect of a hard opening is significant while the body flips over. Besides, opening in track doesn't necessarily mean that your body is pitched 25 degrees head down with a trajectory 45 degrees away from the vertical. The human body has a limited capacity to flatten out from a track or from a dive (the vertical speed can decrease lower than 65mph according to the pro-track). Increasing the angle of attack will not reduce the lift so much (might even increase a little bit) but it will increase the drag quite a lot for a short while. Properly synchronized with the opening sequence, this can give damn soft and slow openings. -- Come Skydive Asia

Did you try a x-braced size 98 recently? I'm wondering if there is that much difference with the blade. I tried a VX80 recently (i usually fly a nitro 88). Apart from the much shorter toggle stroke, the VX80 didn't give me such a thrill. It was a bit faster (smaller size + smaller angle of attack), but it gives much more room for error. Way easier to land (better bottom end flare), and extremely safe to dig out of the corner (longer natural recovery arc and shorter minimal recovery arc, less risk of a dynamic stall). Landing after a half brake approach is even easier on the VX than on the nitro. On the other hand, with its extra long lines, the VX feels sluggish. So, yes, a completely different animal, obviously higher performances... but in the same line as cloud9's comments, i'm still wondering why so many people think that x-braced are the next step after an highly loaded normal 9 cell. If that was the case, a x-brace pilot would be comfortable under a same size (or smaller) stiletto, which is hardly the case. -- Come Skydive Asia

Now that it's official, you have to tell a bit more :-) Are you going to produce it exactly as the blade, or will there be some differences like between the nitron and the nitro? when is the planned release date? Will there be a demo program, or will you replace it by a special offer again? -- Come Skydive Asia

I just had a look at the other threads and i found only one reference to a page with the actual kanji. It shows both the "ha" and the "katana" kanjis and doesn't tell which one is which. From other sources, this is the kanji for katana (source: kanji of the day). The kanji for yakiba/ha is near the bottom of this iaido page. Almost the same, apart an additional stroke to put the focus on the cutting edge of the blade (it means "cutting edge"). So, apart the big K theory (it looks like an edge cutting into something :-), what makes you think that the kanji on the PD ad means katana? -- Come Skydive Asia

Any idea why the sign says "ha" (or yakiba), instead of "katana"? -- Come Skydive Asia

Why would you do such a thing? When i pull, i want my PC inflate as fast as possible. A throw out with the handle at the bottom of the PC might make more sense if you really like unusual designs. A wild guess is that it might increase the risk to have the PC fall back in the burble (a very bad thing with a pull out because the container is open). Anyway, it's usually not a good idea to stay too long in freefall with an open container and the PC deflated. -- Come Skydive Asia

Remove the carricatural aspects, and of course i am convinced that economic infrastructures are good military objectives. In the "The Contemporary Law of Armed Conflict", L.C. Green explicitely refers to "economic targets that indirectly but effectively support enemy operations". It's not a new idea and there are many historical references. In addition to the economic infrastructure, there are the communications and information infrastructures as well. Not really material or combative support to the war effort, but very good military objectives. Again, not a new idea, with many historical references. Even though, i acknowledge that military practices vary a lot i'm wondering how you got these surprising views of military practices. Next time you refer to the Geneva Convention, at least read the title. POW are not exactly combattants. -- Come Skydive Asia

That's really funny because Chapter 22 of the Operational Law Handbook 2002 describes Special Operations as military activities conducted in time of war or peace. Special Operation Forces are described as soldiers, but there are clear references to SF without any uniform or distinctive equipment during their operations (the first of the Pacific Underwater Demolitions Teams were known as "naked warriors" :-). In addition to spying, guerrilla warfare, subversion, sabotage, support to escape and evasion networks, i particularly like the last two lines, the definition of Special Activities: These are activities that are planned and executed so that the role of the United States government is not apparent or acknowledged publicly (sic.) Either your paraphrase is very approximative, or there are some serious discrepancies in the different "laws" of war in America. "Paratroopers - and others who jump out of a perfectly good airplane - are considered combatants and may be attacked as they fall to the ground". Wow, we are all legal targets! Anyway, strictly speaking, a kid planning to spit on a soldier becomes a legal target as well (yes, body fluids are legally life threatening is some states). According to the Laws of Armed Combat, "Civilian buildings are lawful targets if they are being used to support the war effort". Hence, according to this definition, office buildings are lawful targets because they harbor companies contributing a lot to the war efforts (at least with the taxes, but also for their products). Information infrastructures are legal targets, even though they support essential emergency services and control critical parts of the infrastructure indispensable to civilians, especially in vulnerable urban areas. With these selected laws, several terror acts can be defined as "Special Operations on Legal Targets, with Collateral Dammage". A bit longer than "terrorism", but that's the beauty of legal verbiage. Sounds as good as the Klingons' Warrior Virtues. -- Come Skydive Asia

The drawback of experience is the stronger confirmation bias. Opinions are stronger, patterns are clearer, but they are not necessarily closer to the reality. The high number of newbies killing themselves at high wingloading might have no more reality than the high number of violence/birth/disasters during the full moon. The SkepDic's final comment: -- Come Skydive Asia

Now I'm impressed! Let's go. Landings kill. Not only high performance landings (these are less than 20%), not only high wing loadings (skydivers with 150-200 jumps died at WL of 0.8-0.9 psf), not only low timers (25% have 1000+ jumps), not only yellow canopies... landings can kill anybody. From 1988 to 2003, there were 44 landing fatalities (I didn't cross check) distributed approximately like this: - 21 imputed to a poor management of the landing pattern, including turning into wind (8), off DZ landings (6), obstacles (3), demo (3), and a small landing area. - 13 low turns for unspecified reasons - 5 attempts to do a high performance landing too low - 3 fatalities involving high winds, turbulences, or collapse - 2 possibly lost toggles Agreed, lots of things are into the same bag. But they are related to prerequesites to licences and ratings (mainly the A licence). They are supposed to be covered, both in the ISP and in the general recommendations. Maybe before adding new things, it would be a good idea to have a look at the existing SIM and check what can be removed (because it is not very useful) or improved. For instance: - there are already too many things in the SIM (it's always easier to add than to remove, but it's easier to focus on a small number of essential points than assimilating 300 pages) - the focus is not on the appropriate topics (put the focus on the WL and some people will overlook the procedures for landing emergencies if they have a conservative WL) - landing emergencies are not explicitely included in "5.1.A Practice Emergency Procedures" and "5.1.B. Prevention and preparation" (this is reflected in the training) - "5.1.F Landing emergencies" doesn't explicitely cover some important killers (turning into the wind, obstacle/collision avoidance close to the ground, bad spots) while it covers in detail problems usually easily survivable (water landing). - "5.1.I Low turns" is the main killer and it is the last entry! In addition, the way it is explained, some people might think "i'll be fine, i won't do any low turn" (i heared it many times) - The funny wording "5.1.C.4" is an inappropriate distraction (this is THE important thing and it's writen almost as a joke) - Landings are not explicitely covered in "5.2 Recurrency Training" (many people actually think it's all about freefall) - 5.3.b is not helpful. It should state "pilot skills" instead of "experience" and provide some guidelines. - lack of emphasis on the necessity to identify landing emergencies early - ... Some of my very personal suggested action: - reorder and rewrite some parts of "5 Skydiving Emergencies". Basically, rewriting together 5.1.F and 5.1.I, and moving them into "5.1.D", before all other types of emergencies. - make sure that everybody includes canopy emergencies in 5.1.a, 5.1.b and 5.2. Instructors and coaches should emphasize these points - "Practice" emergency landings before every jump (same as cutaway/reserve) - improve 5.2 and 5.3.b to provide helpful guidelines, for instance like in the ISP (drills and skill checks) - ... There are actually lots of extremely good points in the ISP that could be highlighted, or even moved into the general recommendations. From a completely different point of view, I also personnally think that there is a question of attitude WRT landing fatalities. When people blame the landing fatalities on the high wing loading, lots of people think "i'll be fine, i have a conservative wing loading" (almost half the fatalities are at wingloadings from extremely conservative to reasonable). When people blame the landing fatalities on the low timers, lots of people think "i'll be fine, i have more than 500 jumps (more than 1/3 of the landing fatalities involve skydivers with more than 500 jumps). When people blame the landing fatalities on low turns, many people think "i'll be fine, i don't do low turns" (most of the deadly low turns were not planned). If you acknowledge that landing emergencies can kill everybody, including yourself, then it's difficult to hide the scary reality behind misleading thoughts. There is not much choice left than be prepared for these emergencies. Landing emergencies deserve at least the same attention as freefall emergencies, in the training, the recurrency, and our pre-jump preparation. -- Come Skydive Asia

According to Michele's numbers, it is exactly 75%. The year before it was 33%. The cumulated value for 2001 and 2002 is 53%. Considering that ~55% of the skydivers have less than 250 jumps (USPA source), there are probably at least 65% of skydivers with less than 500 jumps. Of course, if you select the appropriate sample, you can prove whatever you want. Can i select 2001 to prove that jumpers with less than 500 jumps are extremely safe? What are the basis for this claim? My first guesstimate is that skydivers with more than 2000 jumps represent less than 10% of the community but significantly more than 10% of the fatalities. I don't remember the exact value, but i think around 14% over the last 5 years, for the fatalities where the jump number is available. According to Michele's numbers it's more than 12% of the landing fatalities. Apparently this would be an evidence that more experienced skydivers are less safe than less experienced skydivers. -- Come Skydive Asia