pchapman

FWIW, I know a biplane paraglider has been built. A fun experiment, but it didn't lead to anything. Believe it was by the paragliding company Apco. Saw the pictures, but don't seem to have a copy. So a biplane ram air wing has been flown, but I don't know of a freefall deployable one. Peter Chapman Toronto, Canada

Another data point: My DZ in Ontario, Canada has six sigmas too. 1 1/2 years old. At least one also has a slightly bent pin.

Any photos of the Mr Bill landing???? ... that is of the round canopy getting full inflation (I think) just before water impact? My only photos are attached. From a 70 mm lens, point and shoot camera at the landing area. The first shows the separation of the two jumpers. The second shows the beginning of inflation. Unfortunately the water is not seen, but the bottom of the photo is pretty much the horizontal plane, judging from the trees. I'm guessing about 100' height with the canopy just starting to inflate. The jumper looks well head down too. Quite the rush. Thanks to Jason Bell and the other organizers & volunteers -- it was a great Bridge Day. Peter Chapman

That's why I say they shouldn't have to tell us all the details. But since their algorithm is a major part of the product -- in the sense that it affects the safety and main purpose of the damn thing -- it would be nice if they'd proudly say a little bit about what they've engineered into it. "So why is your product great?" "It just is. We're smart & experienced people, trust us."

Correction to what I wroted: Vigil or Astra or Cypres. None of the companies have really explained their data analysis precesses.(And they should be able to do so without fully disclosing their proprietary algorithms?!)

THAT MUST BE THE CORRECT ANSWER -- NOT MY ORIGINAL ASSERTION. Just as with the Javelins, it'll vary with whether rings are used or not. Still it's not something much advertised in the industry. I would assume companies at least did new drop tests when ring harnesses came out, unless their previous tests already included very complete data collection with load cells to determine riser forces. Peter Chapman

If you think about it some more, it does matter. Consider the history of the Astra vs Cypres debates -- The Astra was not liked because it sounded like its algorithms were too simple, that it could too easily be fooled. Firing only based on "current measurements" would be terribly dangerous. That all relates to the point I want to make: To me perhaps the most important issue is how the device handles errors and fluctuations in air pressure. I don't think it is clear to the skydiving community how either the Vigil or Astra does that. If all the readings were perfectly smooth and accurate, it doesn't much matter whether the device just measures altitude based on pressure, or calculates when one will be at firing altitude based on speed calculated from pressure changes. The actual pressure readings are going to bounce around due to air turbulence, body position changes, etc. Is working out altitude by integrating speed calculated from pressure better? Does all the integrating add error? Or how can it be used to make better estimates of the true altitude? Spikes in pressure readings would be recognized as not reflecting real altitude, as the skydiver could not be changing their freefall speed as suddenly as the readings would suggest. Algorithms to reject false data could be more sophisticated than just smoothing the pressure vs time curve.

I usually just do two overhand knots. For dacron closing loops, one overhand appears to be enough. I see many that way and feel comfortable with that. For spectra, I am not comfortable with one overhand. While a single overhand tends to work, I've done tests in the rigging shop where spectra (and not dacron) does let the knot slip right out when loaded to 100+ lbs. I'm not saying the tests replicate actual use, but the increasesed slipperiness adds some undertermined risk of knot slippage, so a backup knot is an easy way to add safety. If building spectra loops for others, I put in two very loose overhand knots so that the new owner will be visually reminded that I feel they should have more than one knot. Yes, knots other than an overhand hold better (like a figure 8). I'll reserve them for myself if desired but don't put them on loops for others to keep things more clear and simple for them. Peter Chapman part time rigger

They reduced the strength of the front reserve risers by 33%. Caught your attention? Can someone please confirm this? My memory is poor on it and I've been away from rigging for a month. I think most rigs use Type VII on the front reserve risers (6000 lb) and Type VIII (4000 lb) on the rear reserve risers. Building it that way fits well with the use of one layer of each of those materials for the main lift webbing. We don't see reserve riser failures happening with either type of material, so it isn't a big issue really. Many Javelins, for example, use the lighter type VIII for both sets of reserve risers. (Whether it is type VII plus VIII, or just VIII, depends on whether the harness uses rings or not. This has just been confirmed to me by a Sunpath staff rigger.) Not only that, but the Javelin has been recertified to the newer TSO C23d, using high limits of 300 lbs, 170 kts. Which also reminds me that the Mirage is only certified to the ancient "Low Speed Parachute" limit of 150 mph (not knots). That doesn't mean the rig couldn't take more, just that it hasn't been proved to the FAA. I find it funny that Mirage doesn't announce the reserve riser change in all their advertising. Hmm, something about marketing I guess.... :) Peter Chapman Toronto, Canada

Actually, the safety aspect of velcro slider stows is a complete urban legend. In 22 years of skydiving I had never, ever heard of a "snag" incident, I can't provide solid evidence of such an incident, but somebody, somewhere has gotten spooked by "velcro loop thingies". A few years back a European fellow visited my DZ. He was quite surprised to see a jumper with one of the velcro slider holders, because they were banned in his country. Can't recall where he was from. Some place like Germany, Netherlands, ???? So I bet there has been a fatality that at least looked like it was influenced by a velcro slider holder; otherwise the national skydiving organization would not have (over)reacted in that way. Peter Chapman

It's not entirely unlike skydiving, for there are rules but you gotta keep your head on a swivel because the aircraft involved aren't ones that typically fly long, straight courses from one predetermined point to another. In some countries glider pilots are required to wear chutes, in others, like Canada and the US, it is less common. Not sure how much. Chutes are worn during contests, however, because of the increased risk of collision. The Big Sky Theory also works somewhat when bailing out -- it would be quite unusual (probably even extremely rare) for someone bailing out to be hit by parts of the airplane they departed. As you gain experience with skydiving and the aviation world, you'll begin to notice how useless newspaper reports are about technical matters in aviation, such as the causes of an accident. Reporters have to try to become instant experts on every topic they cover, and it just doesn't work. You'll hear things like "the parachute failed", whether the parachute failed or the jumper failed to use it properly. Peter Chapman Toronto, Ontario

Regarding the old Parachute School of Toronto: They did train many, many people over many years. However, there was at least one more fatality than Mike wrote about, one that would be ammunition for Bill B.: In August 1993 an advanced student there, with about 15 jumps, died in a main-reserve entanglement. His ParaCommander malfunctioned and his manually deployed belly mount round reserve entangled with the main. Students there were not taught to cut away. I don't know whether the student followed proper deployment procedures or not, tho' one jumper from the DZ told me he probably had. There is some risk in dumping one chute out past another. (On the other hand, in paragliding they have good success with hand deploys, tho' differences in equipment and technique make that a whole new topic.) In the end we are left to argue whether it is useful to practice intentional cutaways, and the safety of the equipment to use for it. Should it be fancy custom built gear? (And even so, is the gear suitable for the average jumper, I believe Bill asked. After all, experienced skydiver Rob Harris went in when he got a little mixed up with the handles a 3-canopy stunt rig). Or does one just slap on an old belly mount with separable links to one's regular rig? (That's the way we do it in Canada, right or wrong.) Sure the 3rd chute might fail with a higher probability because the 2nd chute (one's reserve) can't be jettisoned, but aren't we expecting the 2nd one to work? If doing a jump on one's reserve with a belly mount tersh is bad, then what about taking up CRW, or buying a high performance canopy? Won't a few years of jumping like that create a significant chance that one will have to use one's reserve, and now with no 3rd chute to back it up? One's answer depends on how we compare the acceptability of risks chosen more or less intentionally. My experience some years ago was that I had never had a reserve ride. So I planned to do an intentional with a belly mount, but for various reasons the jump didn't happen. Later I took up CRW, and voila, the problem got solved: I had my first reserve ride within a couple years. Which was crazier, trying to do an intentional with an old belly mount, or taking up CRW? Although I can't agree with Bill the Bearded One on the whole topic, I can see that an "intentional" should not be taken lightly. The jumper should be educated on the risks of doing one, and become familiar with whatever gear they choose to use. Also, a plain vanilla intentional cutaway doesn't come anywhere near simulating what a real malfunction situation is like (eg, spinning-on-your-back). Peter Chapman

A couple other minor issues to note: 1) Hip rings vary in their design depending on manufacturer and length of harness and container. Some rigs have the ring between the leg straps and the main lift web, while the lateral strap to the backpad of the container is a webbing junction higher up. On other rigs, the ring does also connect to that lateral strap. Either way, the front and back part of the leg straps may or may not articulate relative to each other where they connect to the ring. Which method is best, I can't comment on with any authority. 2) I'm guessing hip rings would be of even more benefit to someone short. On a short person's non-articulated rig, the stiff sewn junction for the leg straps starts just below the cutaway and reserve handles. For a taller person's rig, there's a few inches more webbing in between those two points, so even without rings, there's a lot more flexibility in the harness.

One fundamental characteristic I don't like about Racers is that the reserve has to be compressed "all at once". On other rigs, the reserve goes in the container, a flap is closed, temporary pinned, another flap is closed, temporary pinned, and so on. At each step one can work the reserve a little more to shape and compress it, and make sure there'll be enough slack in the closing loop to close the remaining flaps. On the Racer, all the flaps go over the bodkins with nothing to really compress the bag. Then the pilot chute is pulled down onto the pack to tighten it all at once. It works but I prefer the more gradual process. (I don't have a lot of experience packing Racers, however.) Peter

Agreed. One can't just write dust devils off as something that only happens off in California, or in the middle of summer. A week ago my planeload saw one in southern Ontario Canada on a nice spring day that can't have been above 75 F. We were climbing out when we saw it a few fields away, showing a tight core on a ploughed field, with dust extending above our 1000' altitude. Dust devils do exist here in warmer and thermally months, but they're still rare enough that nobody thinks about them as a drop zone hazard. Peter Chapman Toronto, Canada

For a few years I thought about doing an intentional to have experience with my reserve, but never got around to fully organizing it. Then I started doing some CRW, so last summer the problem solved itself. After my friend and I both cut away from our canopy entanglement, it looked like I'd back up my Phantom 24 to a landing near the pea gravel bowl. But a stronger wind starting at 200 ft grabbed me and made the ground race by pretty quickly, surprising both me and onlookers. The rate of descent felt OK, but I was a little tense about the upcoming landing with the high horizontal speed. My landing was 75 m downwind of the bowl, rolling backwards. (I should have turned slightly to be able to roll to one side, or tried the trick I didn't think about at the time, which is to twist ones' position under canopy to face the desired direction. This was only my second jump on a round.) The landing was a little rough, with a bit of whiplash action from the backwards somersault, but I wasn't sore at all. I jumped up, started hauling in the partially inflated round, and shouted out, "Now THAT was a fun jump!" Winds on the DZ anemometer were 15-18 mph, gusting 20. I was loading the Phantom 24 with a total suspended weight of a moderate 170 lbs. Since I'm a rigger, and the weather turned bad the rest of the day, my friend and I spent a leisurely afternoon repacking our reserves and untangling chopped mains. No extra cost at all! Round canopies can be neat although a little more nervewracking when it comes to planning the landing.

To add to this -- One debate about dealing with turbulence has been whether to fly in zero brakes or slightly braked, eg 1/4 brakes. Whether or not 1/4 brakes is aerodynamically superior or not, there are 2 reasons why jumpers may prefer better having a little brake on in turbulence, that I haven't seen discussed: 1. By having the toggles pulling against the hands instead of up all the way against the brake rings, the jumper can feel the varying pressures on the brake lines and thus on parts of the canopy. This can help in understanding what's happening to the canopy. (Paraglider pilots, who fly canopies more sensitive to parts of the wing folding under, consider brake line pressures an important source of information on the status of their wing. Is one wingtip picking up lift and getting more pressure, or is one tip getting 'soggy'?) 2. Some canopies and jumpers have the brakes set up with a little slack in the control lines when the brakes are up all the way. Pulling down a little removes the slack from the system (ie, the tail of the canopy isn't deflected) so when the jumper wants quick response in turbulent air, moving the controls will have a more immediate effect. So even if you think quarter brakes is the wrong way to go, just a little bit of brakes may be useful. Peter Chapman 850 jumps, occasional paraglider pilot

As others have said, it depends a lot on the condition of the canopy. A really old, worn, but usable canopy will be worth only a couple hundred I'd guess. I'm no parafoil expert but have learned a few things about them. Old Parafoils were built with support tapes that were much heavier than normal for canopies these days. Foils in general are quite durable I hear, but the early ones are bulkier than necessary. Old Parafoils may also have an old style reefing system, like the spider slider with the bridle going from the bridle up through heavy grommets in the canopy. This is both an ancient technique and very bulky because of reinforcements. Even if a normal slider and pilot chute were put on instead, some of the extra bulk will remain. So there's nothing badly wrong with an old 'foil, but they are a little odd compared to modern canopies or even modern Parafoils. Peter Chapman FX 88, Parafoil 282

Yeah - The MPAAD is supposed to have the closing loop fit right through it, and be mounted next to the backpad with a window added. But what about the aluminum plate that's typically in containers to provide a base for the closing loop & cypres washer?? Some can be fairly big, which would make it difficult to orient the MPAAD so one could see whatever controls it has thru a window.

Sometimes a chute with a blown top skin can continue to behave relatively well: About 10 years back, a girl at my DZ had the top skin of her old F-111 chute blow open almost from nose to trailing edge on opening, on one of the center cells. (The nose tape and trailing edge held.) She had perhaps 200 jumps at the time, and the chute was lightly loaded, say 150 lb under a 220. I saw it happen from above, having pulled higher than her on the same load. She landed normally, and didn't notice that anything was wrong with the chute until finding the gaping hole while packing. Only then did she realize why she remembered that the canopy turned poorly and had a shitty flare that jump. This example is just one data point, and shouldn't be used to suggest not cutting away. That's a decision the jumper has to make for themselves.

I think it can work. A student is taught how to turn left, turn right, and flare. So they can be taught an additional sign of a serious malfunction. It's not just the shape of the canopy, or whether they immediately find themselves spinning. I try to tell students that -- in the end -- it also matters whether the canopy will do what it is supposed to do when they fly it. Does it fly straight when the toggles are let up or during a flare? Does the wind noise go down when you flare? Does it turn left or right when left or right toggle is pulled? Still, there can be mals that are hard to interpret for a novice, like the one that started this thread. The canopy was 'sort of' rectangular, and it probably 'sort of' responded to control inputs properly. It may be a dropzone myth, but I heard of a student who cutaway because something didn't quite seem right...it turned out the canopy was a different color than the one they saw in the training video...

The coldest I've jumped in was -20 C (-4 F), 2 weekends ago, where the air temp was actually fairly constant at all altitudes up to the 10500' exit. Ground temps were around -15C to -20C (5F to -4F). On that jump, with a partner and I doing sit or head down, we both got frostbitten skin on our noses. The skin went quite white so it was easy to see after landing. The skin warmed quickly in the heated packing trailer; during the following week some minor skin peeling occurred. Technically it can be called frost nip because only the skin apparently froze, not the underlying tissue. Fingers were quite cold but acceptable on that jump. So a constant -20C is just beyond my desired limit without a full face helmet or a neoprene face mask. I've had other jumps where the temperature at exit was -15 to -20C, but never had a frostbite problem presumably because exposure time was too low -- the air at lower heights was warming up, with ground temps more like -5C or -10C (23 to 14 F).

Here's a long answer for you and anyone else: It can be a more relaxed sport than skydiving, providing a lot more time airborne. I've had flights of an hour just ridge soaring along a 200 foot high hill, and flights of a few hours at better sites. When the winds and weather don't cooperate, though, then you get to do a lot of parawaiting or short glides straight to the bottom of the hill. Being a skydiver helps somewhat in paragliding, mainly just in general comfort with being airborne, having a feel for speeds and descent rates, evaluating wind and weather, and having a basic understanding of aerodynamics. But there are so many details that are different, where one has to really pay attention to the differences. Not only are the canopies big, but they're trimmed to fly efficiently, not like the ground-hungry trim angle used for many skydiving canopies. Their large size means they react more slowly than small ZP skydiving canopies, but the long lines, high aspect ratio, and improved aerodynamics mean that the canopy has more of a mind of its own when the canopy becomes distorted as in a stall. The canopy can build up a lot more momentum, and can't be flung around as quickly as a small skydiving canopy. Still, very advanced pilots do some incredible aerobatics, including loops and helicopter spins. As people have said before, paragliding has its own instructional system, and it is dangerous to try to do without. At the very beginner level, however, paragliding is so ludicrously easy to do; anyone can be taught to fly short flights down a hundred foot training hill in smooth winds in a few hours. Although paragliding can include floating about in nice conditions, it can also involve a lot of concentration. There's risk from being closer to the ground for longer. If ridge soaring a smaller site, one may be repeatedly flying back and forth fifty feet off the trees. Any misjudgement of the turns or of changes in the wind can result in dropping into the trees. (Just what conditions a paraglider pilot will fly in depends a lot on their local sites, whether they are flying low ridges or high mountains, ridge soaring, or flying in thermals.) Because of paragliders' low speeds, and the tendency of winds to speed up as they cross over hills, paragliders can't fly in as strong winds as hang gliders do. Paraglider pilots must be careful not to get "blown back" over the back of the hill, where the turbulence can literally be a killer. Compared to skydiving, a paraglider pilot needs to learn more about micrometeorolgy. At least skydivers are given a basic understanding of thermals and turbulence around obstacles. Paragliders do have to be flown more carefully than parachutes in stronger wind or thermal conditions. (And those are also the conditions where it is easier to stay airborne.) Paragliders are subject to partial collapses, typically where one tip or one whole side of the canopy will fold under. Everyone trains for dealing with it, preventing the canopy from starting to spiral, and reinflating the collapsed side. Paraglider stalls can be quite violent and are normally not done until one is experienced. A bad recovery can sling the pilot into the lines and canopy. If a pilot is not aware of the feel of their canopy, it isn't hard to stall one side of the canopy when making a deeply braked turn. It's easy not to notice that kind of stall creeping up, even on a student canopy. Ground handling a paraglider in moderate winds takes practice. The pilot is dealing with a giant kite that'll pull them off their feet and drag them into the bushes if they don't handle it right. One can spend hours practicing ground handling, just kiting the glider on level ground. Some background flight & construction data: Paragliding canopies are normally quite large, 24 - 28 sq. metres (260 - 300 ft sq). Glide ratios are above 6:1 even for beginner wings now. Speeds are slow, such as 35-40 km/h in full flight (22-25 mph), and 50+ km/h (30+ mph) using the speedbar -- a sophisticated equivalent to pulling down the front risers but using a foot-actuated cord. The cell count (counting each chamber, so a "9-cell" skydiving canopy would be =18) is about 35 to 75. Aspect ratios 5 to 6. Peter Chapman (25 hours paraglider airtime)

Any idea what kind of plastic is being used as stiffeners for secondary riser covers or tuck tabs at the shoulders? Main flap tuck tabs are often .060" plastic, I hear, but flexible secondary riser covers might need to be .030" to keep them thin and flexible. From different sources I've heard of HDPE, LDPE (for more flexibility) and Nylon MDS being used for stiffening. Peter Chapman

Here's my personal list of suggestions for background on-line reading. Perhaps others have better info: RWS pictures on a well built 3-ring & riser: http://www.relativeworkshop.com/support/tech_risers.html (There was a DZ.com post which I can't find right now, where someone from RWS -- I thought it was Booth himself -- did find some relaxation of the rules in the above article acceptable (whatever that means), when counselling someone with a particular set of risers that didn't meet the specs in the document. My handwritten notes were: Regarding Rule A that the big ring touch the tape for the 2nd ring, a 1/8" gap would be acceptable. Regarding Rule B, pulling the loop out to the side of the riser to check slack, 1/4" was still acceptable.) A 1995 RWS bulletin: http://www.relativeworkshop.com/pdf_files/techpsb_120199.pdf Jump Shack articles: (Go to www.jumpshack.com, Technical Articles) The following two provide info on inspection for correct construction: -- Jump Shack 3-Ring Inspection Instructions -- The 3 Ring: What It Is, And How It Works The following cover other riser related topics: -- Cause Of Type 17 Riser Failures Identified -- Type 17 Riser Study -- The 3-Ring System - Retain and Release Sub-System -- Analysis of a Riser 1997 Skydivemag (the British magazine) article on 3-rings - about reversed risers and force ratios.: http://www.bpa.org.uk/skydive/pages/articles/oct97/kitnews.htm RWS also has 3-ring construction diagrams available, but I haven't checked about how to obtain / buy them. Sorry no clicky. Peter Chapman