pchapman

Cool. This perceptual error was new to me. Scanning has long been emphasized in aviation... but that was more about how to cover large areas of sky given that our foveal vision in the centre is a lot better than the rest.

Oh, *US* style equipment. I was going to say that some US Marines could sell you a flag, cheap. (This is Bonfire, you know.) Anyway, you're on a roll these days for vintage gear, piisfish! Edit: How about the guys at the 'National Parachute Test Center' at Dunellon, FL? They're into selling round military jump gear, among other things, but might have some contacts among the re-creation folks.

I'm just killing time today so I'll answer. T-10 jump, travelling facing downwind on landing, but not too fast over the ground. From his helmet cam, it looks like he did feet, knees, hands on landing. The camera view stayed straight, no rolling whatsoever. Blowing the tibia and fibula does absorb some energy, softening the landing for the rest of your body, but I don't think it is the way to go usually. Presumably, he should have had a better body position to get a PLF in. Man, everyone is wearing GoPros these days. This has little relevance to civilian skydiving -- except that if you are going to hit harder, get yourself set so you'll automatically start your PLF on landing.

Also have a plan for what to do with your seatbelt, so that buckles don't dangle and interfere with the controls after you leave. It may be hard to refasten the buckles behind you and tighten up the straps while you are still in the cockpit, but perhaps they can tuck between cushions or similar. Make sure the pilot can do a slow jump run while still being at a safe speed. It can help if he knows he can power back and let the plane descend on jump run too, to reduce prop blast -- like a jump pilot for student jumpers.

"Why spring loaded main pilot chutes for students?" [Edit: Twardo has been around so may understand the history already, even if answering this simple question in general made me launch into all the history below.] While I don't know why that particular DZ (where ever it is) made its choices, I thought that in the US AFF program, for many many years it was mandatory to have a spring loaded pilot chute. (1980s and well into the 90s?) For the Canadian PFF program, we accepted throw outs from the start, something which to some at the time seemed a little more dangerous and casual than the US system but acceptable in requiring less specialized gear. The idea of having spring loaded PC's was that pulling a ripcord was simple, and it was safer in any attitude. Throw out PC's weren't exactly brand new when AFF really got going, but I bet the whole process of groping down on your hip (no BOC then), moving your arm a certain way, and holding your hand a certain way (not to entangle with the bridle) was seen as pretty complex. Especially for a student who hadn't progressed slowly through a static line program. And a spring loaded PC is the standard for deployment in any attitude if things go wrong, just like a reserve. (Even if it isn't perfect.) Great for students whose stability at pull time may not be great. Using a spring loaded PC for AFF students was seen as taking an extra step to provide the safest possible gear for students! In my 1991 ParaGear catalog for example, all the containers labelled as "Student" were double ripcord systems. Yet NOW, people wonder what all the fuss was about. As the AFF program matured, I guess people figured out that it was possible to run a successful program with throw out pilot chutes for students, right from the start. It had become such a standard of the US system to have spring loaded PC's that I get the impression that changing it was tough. In 2003 AggieDave wrote about Roger Nelson, who must have had a waiver to use throw-outs: I guess some DZ's kept going with the same philosophy to keep using spring loaded PC's. There's more than one acceptable way to learn to skydive after all. Yes there would be a change in procedures for a student going to different gear later on, but one can learn new things. [edit:] Looking some more into old posts, I see that in Australia and South Africa, it was mandatory to use spring loaded PC's for AFF through at least 2003. For a long time, globally, it seemed the "proper" way to do things. When did the US change??

See PIM 2A on the CSPA web site, section 6.17 on unusual situations with canopies. The USPA SIM, also available online, will also have something. The countries' recommendations differ slightly but a second point of view is useful. It may be better to go read & understand "the standard recommendations" first, before digging into the arguments seen on dz.com.

@chris Remember to have at least one GoPro filming the other GoPro's, because GoPro's are so cool. @twardo: [...]cool] Real men never dump above 2K!! REAL men never get out above that! Voila, see attached.

Main containers these days really aren't designed for spring loaded pilot chutes. A closing loop that isn't really slick, that zig zags at all between flaps, can have enough friction to slow the container opening. (And it would be worse, as Stratostar pointed out, for a loop coming from the pack tray or reserve wall, rather than the bottom flap.) Plus, the large stiffener that is typical in the bottom flap can restrict the pilot chute if the PC is stuffed well under it. There's a lever effect, requiring less force at the grommet, to hold the PC in place. Instructors who were around when spring loaded PC's were used with the American AFF program would have a better idea how likely it was to get hesitations in PC extraction. And then sometimes the PC jumps around in the burble for at least a second...

$810 for an apparently very little used, all black, 1982 Jumbo PC. Wow.

Hey, I just realized I have the scanned manual for a Northern Lite, 'sport piggyback', from Para-Phernalia. But even that manual shows the two reserve loops going through the freebag, side to side. It is an early manual as it is mainly about rounds, with added Supplemental instructions for Swift reserves etc. Even for rounds, the pullup cords are shown coming from a double ended closing loop at the bottom of the pack tray. So you're saying you have something even earlier? I'll upload it to parachutemanuals.com in case anyone needs it.

I've also thought that the main reason for stiffeners is to spread the load, anchor the grommet securely, and avoid wrinkling. The Racer side flaps without hard stiffeners are not the "last flaps" like on many designs -- a top flap is the last one to close (unless anything has changed recently). So that hides the side flaps somewhat. On the other hand, on the Racer I use, the side flaps are in good condition after a lot of use, with just the type 4 tape reinforcement around the grommet. While lines tangling with flap stiffeners is very rare, I have an aversion to rigs with stiff flap ends, but very soft & floppy flaps, especially if they don't taper down to the tip quickly. A hard chunk way out at the end of a soft flap is not an ideal design.

And the type of reserve (and to a lesser extent its age) is also needed for anyone to offer suggestions.

To add to what jon stated about STOL kits: The DZO I mentioned before had one plane outfitted with a STOL kit (prior to the Wing X stuff) but wasn't impressed. The problem is, he's more interested in a good best climb rate at 85 mph (or whatever) than better handling at 60 mph or better short field angle of climb over trees at 60 mph. STOL kits aren't necessarily made for what a DZO is looking for.

I think that a rough answer is that both forces create the opening -- extra pressure inside, and suction outside on parts of the curved, expanding parachute. I'm guessing that the suction is a lesser factor, but still an important one. Inside, air eventually starts getting into the almost closed mouth of an initially streamered parachute, and as long as the canopy isn't too porous, fills up the apex of the canopy and starts to push the canopy outward, creating a bulge up there. The pressure inside can go above what the steady state wind pressure (dynamic pressure) would be, as the column of air comes to a sudden stop. Meanwhile on the outside, as the air just outside the canopy first hits the bulge of the canopy, it can be pressing inwards there (positive pressure), trying to keep the bulge from expanding. (So it isn't suction everywhere.) But as the air goes further, as it flows up and over the bulge it will create outwards lift (negative pressure) -- basic Bernoulli stuff. And in the turbulent flow behind the parachute, where the airflow isn't staying attached along the curve of the parachute, the air pressure will be a little bit lowered, also creating a little suction -- that would be "the burble" to skydivers. Even in engineering sources describing parachute openings, the focus tends to be on the slug of air getting inside and filling the canopy from the apex down. That's true, but doesn't go into the source of the forces trying to move the canopy fabric outward, where it is both inside pressure and outside suction. (E.g., http://accessscience.com/content/Parachute/486500 from Jean Potvin of the Parks College Parachute Research Group. This very brief overview of parachutes includes a description of parachute openings. It does mention the suction aspect, but tends to focus more on the internal pressure aspect.) So it is important to remember that there are suction forces at work too. I saw one old military study where the suction forces outside were similar in size to the positive pressures inside, when at a point say two thirds the way up the canopy, early in the inflation process, before the canopy had spread to nearly full diameter. While not knowing what contributed more to the inflation overall, it shows that at certain points and times, it can be close to a 50/50 split between the two complementary forces. I haven't seen enough sources to really understand the exact mix of forces vs. time vs. location, whether overall it is 50/50 or 75/25, for the mix of what "caused" the opening to happen. Modern computational fluid dynamics work should have a good handle on what the pressures are, but I can't find any good reference from quick internet searches.

clicky http://www.youtube.com/watch?feature=player_embedded&v=Hm8DW7CF7dQ One can just see that they used an anti inversion net on it. The opening is typical for a round without a slider: some parts of the canopy push outward as it pressurizes, while other whole "lobes" of the skirt & canopy are still being held inwards towards the centre, so the process is not symmetrical at all. What is interesting is how much the fabric is fluttering when it isn't 'pressurized' from either side, when neither bulged outward by the slug of air filling the canopy from the top, nor bulged inward just below the inflated part. The area which flutters is pushed towards the skirt as the canopy does the usual thing where it inflated from the top. Looks like a full speed video of a similar test, with the lights on is at: http://www.youtube.com/watch?v=ola9cG3RgOM There the canopy snivels a while but I think it is a low speed test, based on the speed of a few items flying by in the breeze.

At one DZ I jump at, they had 6 182's at one time, all outfitted with Wing X over the years, by the DZO. This is all off the top of my head so I don't know the details: A big part of it was the gross weight increase you get out of the kit. (Up to 2900 lbs?) That was valuable for the late 1960s C-182's he had: They were late enough models to have the wide body, so they could take people, but were too early to have increased gross weight from the factory. Over the years those 182s were up engined to 260 hp, perhaps another useful factor -- the combo of extra power and span would work well together for climb. How it worked out exactly for weight of jumpers vs. cycle time, I don't know. But the DZO found the conversion valuable when the DZ only had Cessna's, with the DZ depending on them.

Figured I might as well upload the video of my first jump on my PZ-81 a couple years back: http://youtu.be/oBUayyTdPoI The short video includes the deployment -- without a bag, it is messy, and the opening was snappy even for a low speed hop and pop. (But perhaps the pilot chute controlled reefing works better at higher speed, who knows.) (And for a little carnage, there's the classic mid air collision video where a guy with a PZ-81 spirals into Beatnik under his Delta II. http://www.youtube.com/watch?v=S8wET-7GmHc)

To add one more thing, the manufacturer's quote that Twardo dug up refers to using it as a belly mount. It was also available as part of piggyback rigs. The impression I've gotten is that it seems to be well regarded in Eastern Europe. Very old fashioned now, but remembered fondly for being a reliable canopy for saving your ass.

Yes for the sit down landings, feet would still be deployed as shock absorbers. You're right about wanting to protect one's ass (and spine). Only after a soft touch down at low speed is established, then someone can just ease themselves down onto their butt instead of trying to balance and stay standing. Experienced jumpers with leg issues sometimes do the same. However, there is also the sliding landing -- an option when one has too much horizontal speed but there's no big vertical speed. PLF's are best if there's significant vertical speed, but if the landing area is smooth, a slide (properly done) is safer if there's only a lot of horizontal speed left. That's another skill to learn eventually. As for strutting around in your own rig, yeah, you'll do that when you get one. You'll be wearing it around the house too, and looking at yourself in the mirror...

PZ-81 yeah baby! Triangular, Rogallo style canopy, no bag, webbing slider is pilot chute controlled, Kevlar-like lines. A nice flying canopy. (I've got one to play with as a main, and they are mentioned in some History & Trivia threads.)

Ok, so it looks like "milking" may be a poor term to use on its own as it has different meanings to different people. You can milk all the slack bits of line to the canopy or to the risers and have a real mess there. Bad. One would have to be more specific about just what part of the lines are being milked when using the term. So I think what Wendy said is a reasonable way to put it, although it is tough to explain in text on the internet: Going back to the original post: Things may not be that bad when the canopy is over your shoulder -- only very slight differences in the lines may make them dangle in different curves and look sloppy. A BIT of sloppiness is OK because it can be fixed when the canopy is laid down -- that's a chance to put tension on the canopy and on the lines right at the canopy, to pull the lines tight, away from the harness. (Make sure the harness is anchored well and not sliding across the floor. More experienced packers can handle packing with less tension, but novices will have more trouble.) Pretty much at every stage one re- tensions the lines if they lose tension -- something which is easy to have happen. It can happen when laying the canopy down (so re-tension the lines), when the canopy is S-folded (so re-tension), when one is starting to stow the lines (so re-tension). But when doing the stows, don't overdo taking unevenness out of the bulk of the line, as that may make the next stow too uneven. If the lines started out well tensioned, then there shouldn't be too much unevenness 'coming out of' the line when making each stow.

As we've seen, a wide variety of people can become successful skydivers. One can have tradeoffs -- some people who are good, are also going to push too much to achieve more, and thus get into trouble, such as becoming swoop statistics. So they might both be "good" skydivers, until the day they are not. So does that mean they were suitable or not? There are always things that make the jumper safer, like good spatial ability, and perception of distances and speeds. Some people just have more trouble with flares or getting to the landing area in different winds. Yet some problems can be 'trained out' to a sufficient extent to be safe, so it isn't often black or white whether someone is inherently suitable. If someone doesn't "get" something, is it because they really have little ability in that area, or is it fixable if they are given a lot of other training? (Just like someone who sucked at music class in school -- maybe they could reach a decent standard with extensive training by an expert, or do they simply not have the ear for it?) Then there's self awareness. If you suck at some optional aspect of skydiving, but are aware of it (rather than being "unskilled AND unaware of it"), you can avoid it and thus be safe. Trouble with the long dive down to a big way? Then be a floater, not a diver. Getting older and can't think quite as fast? Time to upsize and pull a bit higher. It has been mentioned that it is important to be able to handle stress, of the type caused by situations which can be physically dangerous. But one also needs to have that awareness & appreciation of danger, to be aware of things that SHOULD be causing just a little stress, in order to result in proper thought & behaviour. That awareness & appreciation will come from different sources, including skydiving knowledge -- the sky is a different environment so we have to learn what is dangerous; we can't rely on evolution to give us built in cues. I know of a student who was asked to leave the sport after a couple low pulls including at least one AAD activation. It wasn't just their poor performance, but that they were so unaware of the danger they were in. I believe in the debrief of the last jump she said something about being caught up in watching the pretty clouds... If you can't keep up and be aware of danger, or have an attitude that blinds you to appreciating danger, those are cases where the person (at least at that time) is not suitable for skydiving. That's where people on the DZ worry about the guy who just seems clueless, maybe even more than the guy who is out to break the rules (if it is likely only to harm himself). That brings us to attitude (or whatever one wants to call it), something which may or may not change easily over time. Whatever their skills and ability to perceive danger, that may not help if someone has an attitude that leads to deliberate choices of excessively reducing safety margins. How all these different factors mix together, who knows. The mental factor is often way more important than the physical factor.

I go for scenario A. My opinion is that exit timing is primarily there to provide horizontal separation for freefall, tracking & opening, where we are moving fast and aren't always looking where we are going. What happens afterwards, is secondary. Yes canopy collisions are a serious concern, but at least we're moving under 60 mph typically and supposedly looking where we are going. There are always people opening at different altitudes, with different wing loadings, with different flying styles. Why would scenario A be bad, with 2 groups of 4 all open same time, same altitude? If it were 'bad', I guess we could never do an 8 way or 20 way dive again. So stage the exits to provide horizontal separation, and worry about landing separately -- that's down to pattern discipline, landing zone size, landing zone rules etc.

Find and talk to old timers, see if someone has gear in their closet. That can be by word of mouth, just talking to older jumpers who might know someone who isn't jumping any more. Talk to DZO's; long time ones may have stuff stored away. Contact people on dz.com who have written about recently jumping vintage canopies; occasionally they might want to sell a less used item or have a line on something they don't need. Very occasionally things come up in classifieds here, or on eBay -- although in the latter case people sometimes expect too much money. As for Texas, Larry Fojt is someone who is known for doing vintage gear jumps and having multiple canopies. He's on facebook but haven't seen him on dz.com. (I'm hanging onto my Paradactyl and my ParaCommanders!

I see that the Argus manual (at least one from end 2010) says That opens up the awkward issue of documentation of when the AAD was first used. Not when the dealer got it, not when the user got it, maybe when installed in a rig and tested, maybe when the rig was first jumped? Where is the proof of that date, especially if it isn't the original owner? One might easily have a couple months extra, above what the displayed date is. The rule doesn't say 48 months, or +/- 3 months, or anything like that. So is 4.4 years still "4 years", but not 4.6 years? And if one sends it at 4.4 years, is it 3.6 years the next time? I'm all for sticking to mandatory AAD checks if the manufacturer requires them, but the wording could be more instructive in this case. I could see a rigger saying that since the date is more than 4.00 years since manufacture, therefore send it in. It depends on the type of proof the rigger wants: Does he pack something if there's no proof that something is wrong, or does he refuse to pack if he has no proof that everything is absolutely correct? But if a rigger were generous, one might let it go this time, with a note written on the repack card for a mandatory check at the end of the next full 180 day repack cycle. That's just making something up, but is the kind of thing that's nice to a customer but doesn't let them get away with totally ignoring AAD servicing rules. Wonder what US dealers like Chuting Star or ParaConcepts think. Hey, this is on ParaConcepts' site: That's a very generous interpretation, that one can go to 4.99 years multiple times. So is that just an opinion like anyone else's, or is that the official interpretation that they got from Argus when the company was still active with AADs? ChutingStar's site just says every 4 years, so there's no clarification there. [Edit: By the time I finshed all this, DiverMike provided a different interpretation of what ChutingStar wants -- end of 4th calendar year. But that penalizes anyone with a December manufacture date, so I'm wondering if it is supposed to be just 4.99 years. So I think we still need to get something more official from the dealers / distributors. ] Someone should ask Mike & Kirk at the companies. And of course don't forget the rule in the newer manuals to replace the battery at every repack. (Although I'm sure I'd ignore that if it is an unscheduled repack in the middle of a cycle, because the rule is written in a ridiculously inflexible manner.)