pchapman

There are different factors at work. Having two canopies of the same design will tend to make them fly more similar to each other (than if they weren't the same design). Having the same wing loading will also tend to make them fly more similar to each other. However, having quite different sizes will tend to make them not fly the same, at least in certain ways. Different sizes may not change the speeds much. At the simplest aerodynamic level, speeds will be the same. But the drag area of the jumper will not necessarily scale the same as the drag of the canopy. So the trimmed angle of dive and thus the speed may vary a bit, as will the glide angle. What will change a lot is the dynamic feel of the canopy. Even if both are at the same wing loading, the smaller one will have shorter lines, less distance to travel to attain a particular bank angle, have less inertia, need less brake line movement for a given control surface deflection angle, and so on. The smaller one will be twitchier to fly. The PD article previously mentioned goes into that stuff in more detail if it is the one I'm thinking of. So I think one shouldn't throw out the idea that similar wing loadings tend to make canopies behave similarly. But also keep in mind that at a given wing loading, a larger canopy will be easier and smoother to fly, and a smaller canopy twitchier to fly.

Assuming the canopy is for BASE eventually, size it for BASE; don't worry about sizing it for skydiving. Let's say you're 200 lbs geared (based on your profile), thinking about a 280. That's .71 loading. I jumped an big 7 cell accuracy canopy loaded .65 for years. I never had a problem with high winds and would jump whenever others jumped. Ok, sure, sometimes if I messed up the spot or didn't pay attention I'd land off in the boonies, but that wasn't often. There were a couple compensating factors: it was a Cessna DZ so people got decent spots, and with a slow canopy I wouldn't be opening up high at 3,500'. Strong wind days did take some care -- Making sure to stay facing into the wind during much of the ride, and planning an approach that wouldn't let you drift far downwind. I liked making a fast downwind run at low altitude, then turning to face the wind at no higher than a couple hundred feet. The lower you set up, the less you can be in error if the wind isn't what you expected. And a run downwind offers much better visibility than facing the wind for a final approach from up high, blowing backwards, and trying to look back behind you, past your legs for a predicted touchdown spot. Usually by the moment of touchdown, wind shear brought the wind down enough that even if you were backing up on approach, you could touch down pretty much vertically and stay on your feet. So if managed properly I don't consider it a big problem to fly a lightly loaded 7 cell all the time. Besides, if you're gonna BASE at some point, suck it up!

Well, your experience will make a really good story down the road when you're an experienced jumper. You managed to find a situation where floating the PC through the air on the packing mat doesn't detect whether it will stay inflated in freefall. For the moment though, nice job getting a canopy out. Reaching behind you is never recommended -- one can waste a lot of time or half hitch the bridle around one's wrist. Still, I bet more than a few experienced jumpers would do the same thing, for one try before going to reserve. When it came to rigging that PC, something got seriously missed! (Edit: assuming the link didn't loosen, open up, and fall out, which is unlikely but possible.) I once walked by a novice finishing packing his first rig for the first time. Nobody was watching out for him as he had jumped the rig already, but it had been else's pack job. I casually asked if he had cocked the pilot chute properly. He responded, "Did WHAT to the pilot chute?" Uh-oh. He hadn't known about cocking collapsible pilot chutes. He hadn't known he needed to ask more questions, and some knowledge just hadn't made its way to him from other more experienced jumpers.

Lou: There's clearly still some confusion over what the K value represents and how round vs. square has anything to do with it. And that seems to include those who have checked out the .ppt slides in the other thread, which I'll have a look at soon. The K value represents a units conversion factor (due to mixed units being used in the D=KAV formula) and a descent rate factor to account for how long the parachute is exposed to the wind? But what's with the big round vs. square differences?

Jakee and Wendy W. make good points. Even for an individual (rather than a whole group) there are a mixture of viewpoints that all mix together and are exhibited at different times. On can't take one quote from a person as representing their entire view of the sport. There's also a difference between what people say and how they actually behave. A lot of the points made have some validity, but for every point it seems one can make a counterpoint. A typical item in the Edgework & Control paper: "By invoking fate, jumpers frame a skydiving death not as a matter of the inherent risk in the sport catching up with someone, but simply fate dealing the ‘victim’ a bad hand. This trump card, therefore, keeps intact the notion that the sport is not particularly dangerous if skydivers manage the hazards properly. " I can see some of that being true: there is a tendency to remove a accident from the concept of the risk we ourselves face, maybe because we don't expect to screw up in the way the victim did, we won't panic turn into the ground, or we are going to take better care of our gear. Yet at the same time, the statement is also partially wrong: we may see a death as both a bad hand from fate, and an example of the inherent risk. We know airplanes can kill you without you being able to do much about it, bigways can be more dangerous, you can't afford to mess up much in a swoop, and so on. I wonder to what degree some of the things discussed are just as prevalent elsewhere in society. I think most people try to believe that they'll make it home safe at the end of the day, whether they are skydiving, out at sea on a small fishing boat, or driving to work on snowy roads. Yet at the same time there may be some fatalism too, as even in mundane everyday existence we know there are risks. How to characterize the combination of all the different thoughts and feelings is difficult. Observational techniques aren't good at assigning numbers to things, but on the other hand, survey responses don't necessarily get at the truth either.

1.37 wing load at say 350 jumps? Boring.

Jason did some skydiving about 10 years back; I'm guessing 150-200 jumps. I corresponded with him a few years back. Attached is a version of the Edgework & Control paper. I'm not sure if it is the final version that appeared in the journal, but at the time he sent it to me it had been accepted for publication. The Lyng he refers to is Stephen Lyng, who I gather is well known for his study of 'edgework' as it has come to be known in sociology. E.g., he edited the book "Edgework: The Sociology of Risk Taking". Lyng also coauthored a paper (in the journal "Theoretical Criminality" 2001 v5(2) pp177-202!) where the authors went to Bridge Day and interviewed jumpers. Jason also did a published paper looking at gender and sexuality issues in skydiving songs, in particular the Crack Choir and Cock Chorus at the Lost Prairie boogie. That paper seemed to me a little over the top in over-analysis of the situation, even if it was valid social observation. (Sociology of Sport Journal, 2004, 21, 397-417) E.g., "Analyses reveal that men’s songs constrain the transformative potential of women in sky- diving by trivializing, marginalizing, and sexualizing them. Further, they reinforce male hegemony in skydiving through the construction of a hyperheterosexual masculinity. Mean- while, women’s songs resist male hegemony in the sport, laying claim to discursive and physical space. " I'll cut him some slack when it comes to the writing style. Just like guys at a boogie, sociologists need to fit in with their peer group too. I have also attached another paper of his, "Policing the edge: risk and social control in skydiving" (Jason Laurendeau and E. G. Van Brunschot, Deviant Behavior, 27: 173-201, 2006). I think Jason's research has since taken him away from skydiving to other behaviours, such as environmental activism. [Correction: While he is doing that, he is also looking at BASE.] As an experienced jumper I don't think I learned a huge amount from the papers. Still, it is is always interesting to read about perspectives of risk in skydiving, how skydivers react to it, and how skydiving is presented to outsiders. Jason was able to do so with some insider's perspective, which is rarely the case. The closing lines in the abstract you quoted bear keeping in mind. To repeat, "In the choices jumpers make about how they participate in the sport and the ways they interpret the experiences of themselves and other jumpers, they defend the position that their hazardous environments are within their control. When this position becomes untenable, they often draw on the notion of fate to construct certain hazards as outside of the sport, thereby sustaining their sense of control." It is almost a tautology -- we always feel in control except when we realize we aren't. While the statement doesn't look at the role of actual risk or control, still there is some point to it.

While I think it is useful to point out all the various factors that go into some sort of mathematically perfect spot, in practice I don't think things need to be that complex. The numbers spit out by a calculation could still be compared to normal practice in typical conditions, to help figure out what to do in atypical conditions. Let's say a common condition at the DZ is 10 mph ground wind from the west, rising to 30 at altitude. If the computer spits out a spot .9 nm west, but everyone knows that on a day like that the green light is turned on at .4 nm west, then one already has a guide about what degree the computer number should be varied for "real life" use. Admittedly one gives up some accuracy if one can't figure out how to simulate every aspect of the real process, but the idea is to help get a better spot, not a perfect one. Then when the computer helps calculate a spot for a day with weird winds and doglegs, one can make an adjustment given one's experience of the computer number vs. the real life number. It's hard to tell whether the idea of a little spreadsheet will get shot down because "it's too complex", or "it's not really that complex -- any decent spotter or pilot can figure it out."

Sure. The slower you start the harder you land. Why do you want to do that? I will argue that the answer can be, "Because I was told I'm a bad jumper unless I am able to?!" For years and years you would see statements saying how you should be able to land any canopy you fly from quarter brakes. This persisted into the era of crossbraced canopies, that even with a small canopy, you aren't able to fly it right unless you can make a landing from quarter brakes. The concept of landing from quarter brakes was for example in "Parachuting: A Skydiver's Handbook", 2003, but that was aimed at novices and likely thinking of F-111. Another source is the USPA SIM. The 2007 version says in 6-10: D. DOWNSIZING PROGRESSION 1. Before moving to a smaller size, a jumper should be familiar and comfortable with the following landing maneuvers on his or her current canopy: a. landing flare from full, natural-speed flight b. flaring for landing from slow (braked) flight c. consistent soft, stand-up landings within ten meters of a planned target in a variety of wind conditions d. beginning to flare, turning to ten-degree bank, and returning to wings-level before landing (My emphasis added.) No wonder someone asks about the issue. (Although in this particular case the original poster isn't in the USA.) Given the lack of detail in recommendation (b) above, jumpers had better be talking to more experienced jumpers before just going out and trying it. The partial brake concept is still out there, so it is natural to wonder if an old saying is out of touch with some new realities. That's not to say that having a little energy in reserve isn't a good thing. It's implied in a lot of those downsizing skills drills. E.g., that one can land one's canopy up hill or with a flared turn or in rougher terrain, that one feels comfortable landing one's canopy in other than perfect conditions. A couple of the well known skills drills, however, don't mention actually landing from a partial brake approach. While I still see a little value in the quarter-brakes-until-flare idea, I think it becomes less relevant at high wing loadings. It may be sufficient to just recommend being able to (a) comfortably land from unaccelerated flight, or (b) do an approach in partial brakes (e.g., when needing to slow things down or exercise glide path control over a bad area for landing), but learn at what point one can go to zero brake, and still have time and altitude to recover speed and plane out properly for a normal landing.

The page 71 thing: QUOTE: Ohio Lawsuit 1. David Roberts (tandem jump instructor), William Blake Milford (pilot of plane involved in the jump), Aerohio Skydiving Center, Inc. (drop zone). SPOT, LLC (entity which owned the plane involved in the jump), S.E., Inc. (manufacturer of the Dual Hawk tandem harness) and USPA (collectively, the “Defendants”) all are liable for the death of Ellen McWilliams. 2. USPA was negligent in reporting safety mishaps involving tandem jumps to the Federal Aviation Administration (FAA) or the other Defendants. 3. USPA misrepresented data about safety mishaps to the FAA, or the other Defendants, including lobbying the FAA that tandem jumping is safe. 4. USPA assumed a duty to keep tandem jumping safe and failed in this duty.

I jumped one time with the civilian club at the Canadian Forces base at Lahr, Germany, in the early '90s before the Canadian bases in Germany closed. The base was relatively quiet, with the jet fighters having left a decade or two before, and most of the helicopters off in some fragment of Yugoslavia. So there I was in front of a huge reinforced concrete hardened-aircraft-shelter, siren and rotating beacon going off, as motors slowly slid open the massive hangar doors. Revealed inside were the club's offices and their little C-182. A well protected DZ!

1. Vigil 1 is not approved. How about a hint as to why? (I haven't looked at a 1 vs. 2 lately. Form factor different enough or is it just that RI just doesn't like Vigil 1's all that much?) 2. 'must follow RI installation procedures' and 'see website and manuals' Is that standard boilerplate language or is there something super duper special about installing them, unlike AADs in other rigs? Just asking (even if doing so a bit bluntly)...

"Skydiving" was also great for those of us outside the USA. In addition to all the jumping, there were interesting equipment related articles, and current controversies that might never get into an official organization's magazine. There was no need to wade through the material in Parachutist that's organization-specific. (E.g., Lists of licenses earned.) On the USPA site I don't see any way to just subscribe to the magazine. My gut feeling is that it would have to come out cheaper per issue than Skydiving to be worth it...

In flight, due to airfoil aerodynamics, the fronts will tend to take more of the load. But I'm not sure that riser loads on opening are higher on the fronts. This is despite knowing that (at least towards the end of the inflation?) one can pull down on rear risers. Some of the Parks College Parachute Research Group data show higher rear riser loading on opening. But that was just one paper with graphs for a Sabre 210 or similar and I haven't checked the rest of their data & conclusions. Also, early in the inflation, the canopy is aerodynamically more like a flat plate, or maybe a cupped plate. The nose is gradually pulled down due to the trim angle the canopy was built with, and the outer tail is pulled down more sharply by brakes. I'm not sure all that biases strongly in favour of either front or rear loads. Overall, I can't say for sure whether fronts or rears take more load on opening, but it isn't as clear cut as it is for flight under canopy.

The stomach drop feeling is certainly less in skydiving. There has been the discussion about the degree to which wind resistance slows the vertical component of the drop (vs the horizontal), and to what degree the two can be treated independently, and the degree to which jumpers may get some lift on exit depending on body position. In any case, I think that part of the issue is also the influence of (a) other sensations and (b) the degree of familiarity with the situation. In skydiving there is all the noise and wind blast, enough unusual sensation to begin with, that for many, there's no falling feeling noticed even from their first jump. While one's body may be signalling a sudden drop, one may not notice it with those other strong inputs coming in, including ones that signal to the brain that one does have some support -- The wind pressure may suggest to the brain that one isn't totally weightless and falling. If one thinks about it one might notice the dropping a bit. But eventually it becomes 'normal' and not noticed, like someone wearing glasses can pretty much forget that they are on. I remember getting a bit of the falling feeling back, when I was a novice jumper, when I did an exit on my back for example. It was a body position I wasn't yet used to, so I could for just a moment get that feeling of falling unexpectedly.

I was thinking that it would be a good idea for jumpers to do a yearly review of their past season, to think about any incidents or near-incidents they had. These things can be useful food for thought for the future. It's a simple idea but I've never heard it mentioned before. Skydivers do study accident reports, and some DZ's might even review the previous season on a Safety Day. But we could do a personal review too. It is easy to think, "I was safe. I didn’t hurt myself, and no mals either. No problem!" But that may be glossing over a number of little incidents. Maybe there was that dig out of the corner on a swoop that just avoided hitting the ground, there was that load where separation on opening was too small, that toggle fire that was probably from sloppy packing, that time someone "came out of nowhere" while was under canopy, that time one didn't secure that baggy sweatshirt and it was covering handles in freefall, and so on. These things may or may not be one's fault or fully under one's control. They don't always mean one screwed up, but they need to be considered as they influence safety. Some of these things -- especially the awkward moments that one would prefer to forget, and didn't actually scare anyone badly -- are easy to forget months later, but if written into the logbook at the time they can be summarized later. There are those sayings, true or not, about how for every fatal accident there may be 10 accidents that could have been fatal, and 100 incidents that might have been accidents. There are a lot more of the little problems to learn from than the big problems. These things add up and it can be instructive to catalog them at season's end, despite thinking that one is a reasonably safe skydiver. While jumpers will accept different kinds and levels of risks in the sport, there's still an important difference between an intentional low pull and getting sucked low before one realized it. Anyone else find that whatever their impression of their last season is, when they really start to think about it, they remember a bunch more little things that didn't go that well? (Disclaimer: Now don't get the idea I'm just here to harp about safety. I have been known to push a few limits.)

Re: the couple posted images. Yeah that was a neat one... a pull-off from the top wing of a Jenny or similar. When Life posted their photos, it was discussed in a History & Trivia thread. Based on looking at car racing web sites, it seems to have been at the now closed Ontario Motor Speedway by Ontario, California. There are some other photos in the sequence but the labels all differ so they aren't as easy to find. Even in '72, Jenny's were rare and old chutes like that even more so. Looks like the it was an unsleeved round, and with reinforcing bands at strange angles, it seems more like a Hoffman Triangle or god knows what, rather than a conventional gored round canopy. Also looks like the jumper went without a reserve. While I might expect this from an airshow in 1952, I didn't for 1972.

A few comments on things mentioned in the thread: - I don't consider it such a fantastic display of skill that he ditched it OK. Still, it seems like some good decision making considering there isn't much flat land in NYC. They presumably put it down nice and evenly, without dropping it in from 20' or catching one engine in the water first. It probably helped they were on a flat river and not dealing with oceanic swells. - The A320 has almost no manual reversion -- but there is a little if all the power is out: There are rudder cables that would work with a little dihedral effect to create turns. And there is mechanical pitch trim, although I'd bet it is slow and tricky to use well. - We haven't quite figured out A320 APU and RAT use here. (Time to check some aviation forums...) In one of the online manuals it suggested that if hydraulic power drops too low, the Ram Air Turbine drops out and activates automatically to maintain sufficient hydraulic power for the controls. - If they lost all engine power, the descent angle wouldn't be that steep. Airliners with their clean fuselages and long efficient wings actually have glide ratios better than your average light plane. Maybe 16 or 18 to 1 in all the numbers I see. Light planes may only be 8 or 10 to 1. That's all at best glide speed, without the drag of flaps to slow before landing. An airliner will be moving fast along its glide path, so high descent speeds can still result if the glide angle is poor. For example: I don't know A320 speeds, but let's take a conservative 150 knots at a 14:1 glide ratio. That's only a 1100 fpm descent -- a fraction more than a student skydiver under a Manta. But if the glide ratio goes down to 6:1 lets say with some flap out, then the descent rate is up at 2400 fpm. That is getting high, although a small crossbrace canopy in full flight may be doing 1900 fpm easily.

Hey Hackish -- check out Poynter's, it has a little bit of info (not a lot) on the steels used and the manufacturing process.

And I just replaced one too, the first in years. Found on an older Vector III the first time it came to me for repack. Measured over 10 degrees of bend. That was too far from normal for me. Whether or not the strength was OK, it could be more easily dislodged as it stuck up, and might start adding to the pull force. I can't comment on the exact metallurgy involved with bent pins, but the steels used are pretty ductile in order to let the pins be swaged onto the cable. One can take pliers and bend pins 180 degrees (E.g., using old belly mount reserve handles, and the 180 degree bend, allows for resetting FXC's that need a maybe 50 pound pull.) If done too quickly or with too tight a radius the pins will break, but with a little care it works. I imagine there would still be some microscopic cracking from straining the metal past its elastic point, but bending it that much still shows that pins have some reserve of strength in such situations.

I dunno. Maybe I'm just being contrarian tonight, but it isn't that rare to see rigs with reserve pins that have gotten that little set to them, where they still stay flat against the flap. Nobody changes them and they stay that way for years. Maybe more so for the terminal style pins, like on Javelins. Someone else will remember better.

Hi Hackish: You mean the wrong way being an extra fold back of the free end, so that the excess stows not on the main part of the chest strap, but across the other side of the buckle? If that's correct: I'm not yet convinced that that's bad. I see the point that if the free end gets pulled away from the buckle, it will eventually rotate the buckle so that it loosens off, just like when one pulls up on the edge of the buckle to loosen it. But that takes a lot of rotation to accomplish, and if the free end is stowed in an elastic as usual, it stays in place. Also, one might argue that the extra fold is one extra change of direction that could add friction to the system. That's a bit theoretical though. Your idea did get me to go and play around with my chest strap. I played with repeatedly pushing the main lift webs closer and yanking them apart, giving them a bunch of 'cycles' to try to loosen the chest strap. This is on a rig with a single layer strap, which would make it loosen more easily. I found the 'extra fold back' way actually better than the 'normal' way. In the normal way, when the MLW's are pushed together and pulled apart, both parts of the chest strap loosen and tighten -- that's both the main part of the strap and the free end that is snugged up against it with a keeper. When it all loosens there's a big loop of loose strap going around the parts of the buckle. But with the extra fold back method, only the main part of the chest strap loosens and tightens. The free end, with a keeper keeping it in place on the other side of the buckle, never loosens. So there is less that gets loose every time the MLWs come closer. After many repeated cycles, the chest strap stayed tight while with the normal way of stowing the strap, the chest strap got looser and looser. With the normal way, the free end was still stowed in its keeper, but the whole thing kept sliding closer to the buckle. The way with the extra fold, back over the buckle, seems to actually be superior in my test in reducing the chance of loosening off after being unloaded. I don't know what the answer is here. Is folding the chest strap back over the buckle considered by some others wrong too? I fold it that way; I find it convenient to set up and makes it easier to pop the excess out to loosen the chest strap after opening. Interesting topic in any case as I don't recall anyone ever discussing which way is better or acceptable.

Just noticed this in the original post. While body type will be a significant factor, I would add that it certainly isn't the only factor and shouldn't hold people back from believing they can do a good track. Just my opinion from one isolated example I saw: One time I watched from the ground as a 20 way round (or something similar) broke and tracked. The jumpers tracked away simultaneously, spreading out in an expanding circle. But one dot shot out from the expanding circle, steadily gaining significant extra distance compared to all the rest. Who was this guy who was blowing everyone else away?! I watched the jumper closely until landing. It did turn out to be an experienced jumper -- at least a couple thousand jumps -- but more surprisingly, he was a short, stout, tubby f*cker.

Johan: AS8015 might be out on the web somewhere but is rare. Normally the SAE that controls it will sell it for $50+. TSO-C23d basically says 'follow 8015', and 8015 lists all the different strength tests & drop tests that manufacturers do. But Jerome has a point. That one paragraph is one of those things that seems to be totally ignored, on the face of it. Customers wouldn't stand for parachuting companies forcing them to use only a particular brand of reserve. But the interpretation could be disputed; one of those things that give riggers hours of fun on this site arguing about what things mean and what rules apply. That paragraph 5.1 talks about qualifying stuff either as components (canopy, harness/container) separately, or together as a system. If it is as a system, "The airworthiness of a parachute assembly, including other separately approved nonoriginal components, is the responsibility of the manufacturer who performs the certificating tests for the parachute assembly. The manufacturer shall publish and make available a list of interchangeable components which have passed the following tests [...]". One might argue that that doesn't actually say all components MUST be certified as a system, just that it says who is responsible IF everything is certified together. So unless there's other wording elsewhere, nothing says one can't assemble a system from multiple certified components -- a certified harness from one place, a certified reserve from another. That's where, at least in the US, FAA rigger rules on rigger discretion come into play. But that's a bit of rules lawyering and there may be plenty of counterarguments. Still in the end: IF nobody cares about what reserve goes into a PdF rig, then it is OK because nobody will stop you. Or does one hear of PdF grounding rigs of theirs they find with others' reserves?