pchapman

One of Namowal's old pre-skydiving blog posts addressed the issue of how easy it is to attribute others' misfortune to being their own damn fault. (http://tailotherat.blogspot.ca/2007/06/schmicarus-schmicarus-where-are-you.html) Hmm, the cartoon can well be applied to skydivers (and slightly broken novice skydiver cartoonists)...

OK, RiggerLee beat me to it but I'll reinforce his point by what I've been typing up: There has been some debate about that. I don't know what people are saying these days but here's my take: While a swooper can change their drag and thus the overall dynamics of the flight & swoop, we are hanging by the 3 rings. So you could climb around your harness using it as a trapeze, and it would be like playing around while standing on a kid's swing -- in the steady state condition, your center of mass will remain directly below where it is hanging from (Ignoring drag effects for the swooper at speed.) So in that way, shifting in the harness will do squat. Now, maybe you can do something dynamically -- the physical act of swinging your legs forward could do something, just like under a swing set. And another exception is that in addition to hanging under our 3 rings, we will have brakes and sometimes risers in our hands. That can provide a little leverage for moving one's center of gravity. Even then, often all one would tend to do is change the angle that one swings under the 3 rings. So to oversimplify, if you are in your loose swooping harness and you push back on your rear risers while trying to lean forward, you'll just rotate your body, and the C of G will stay under the 3 rings. I haven't thought about it enough, but maybe you can find an angle to pull or push to pivot the C of G away from the vertical - but it seems hard to figure out any decent leverage to do very much of that. If you tried to do chinups from the top of the front risers, OK, but that's not what you need to do with the risers during the swoop. So if someone is leaned forward in their loosened harness, they are NOT "shifting their center of gravity forward", unless they also somehow are pushing on the risers in a way to hold themselves forward and not just rotate forward. As for what the line loadings and flight path and all such things are, that's going to be a complex interaction of the lift & drag & torque of the canopy vs. the drag and location of the jumper beneath. A complex subject in any case.

Sorry, I'll have to call you on that one -- it's a piece of aerodynamics people aren't often taught properly. In straight level flight, like for an airplane with an engine, the Lift is vertical and is matched exactly by the Weight. (Without getting into tail vs. wing lift details) But we're talking parachutes, gliding downwards at a fairly steep angle. The Weight is matched by a combination of the Lift (perpendicular to the descending flight path) and the Drag (parallel to the flight path). So it is 1 g unaccelerated flight, just that both Lift and Drag hold us up. The amount of Lift isn't typically a whole lot less than the Weight, but it is important to understand how Lift & Drag are defined when one is trying to understand even the basic aerodynamics of parachutes. If you used a parachute that descended on a 45 degree angle, a 200 lb jumper & gear would be supported by 141 lbs of Lift (angled 45 degrees forwards & upwards) and 141 lbs of Drag ( angled 45 degrees backwards & upwards) Sorry I don't have a diagram handy.

Chit disturber!

How is that going to help avoid bag-locks? They still have locking stows. I still find baglocks a bit mysterious. But freebags only have one two stows, one on each side, so there's no way for a stow to catch over some nearby stow. That would seem to massively reduce the chance of baglock. The few times I've heard of bag locked reserves, while I don't know all the details, I think it was more a case of an out of sequence deployment, where the bag somehow tumbled, bridle wrapping around the bag, itself, and the lines coming out of the bag. I suppose it is possible to have lots of line stows and avoid bag lock type situations, if the stows are small and tight, even if all next to each other. That's what one has on diapered round reserves. You could easily have 20 stows all up next to each other. A little spooky even for me, who has used round reserves, but I suppose they have a good track record -- because they aren't packed fast and sloppy like main bags with stows.

The loading on an airfoil is normally going to be weighted much more towards the front. That's a matter of basic aerodynamics of airfoils, but the difference between canopies will depend a lot on how the lines are arranged (eg, trim angle and location of payload relative to the canopy). You'll notice differences just from testing the forces on front vs rear risers on different canopies. Or reach up and pluck at individual lines, and you'll feel a big difference in how much force is involved. The weight the canopy supports will also be something like slightly less than the total weight of the jumper & gear (maybe 5-8%), because the weight is supported by a combination of lift and drag because the canopy is on a descending flight path (not level flight of course).

Note that varying "how high" answers may be a result of Above Ground Level vs. Above Sea Level measurements. In another thread someone said the altitude readouts on the "live" video were ASL.

Maybe he has the same reason as many who jumped Stilettos in 1995... because they are fun and exciting to fly.

[Edit: looks like I didn't refresh the thread and everyone's been doing the weight calcs, but anyway...] He'd be a couple pounds lighter. I calculated the weight decrease from gravity alone to be about 1.2%, for about 39,000m or 128,000 ft altitude. (Ignoring buoyancy effects of the air or the not quite spherical shape of the earth or centrifugal effects.) That matches with a rough linear rule of thumb I once heard of about 1% decrease in gravity per 100,000 ft. (Even in lowish earth orbit, say 250 miles up, about 90% of gravity remains. The wikipedia page on Gravity of Earth is helpful.)

I guess Fournier has been trying to go high for a very long time. One French blog I saw wasn't specific but mentioned "1992, 1997, 2000, 2002" etc, when being skeptical about Fournier, so maybe Fournier has had big plans for longer than most of us in North America know about. Unfortunately the Paramag link from Twardo's post is not active, the one where Fournier's experience is questioned in the French magazine. I can't find the article online anywhere. The full mag may be online for subscribers only (rather than just a few selected articles, that are public). It would be the July 2008 issue of ParaMag. Fournier obviously did do a lot of organizing, whether or not there were questionable elements to his story.

OK, so Lindenwood is a frickin newbie and you know what kind of a pain in the ass they are. Yet presumably his advice isn't wrong about layering or not having to spend money on Under Armor or covering your neck. Doesn't seem particularly controversial to me. So, what's wrong with "well fitting leather motorcycle gloves"? I'm asking, really. I don't know anything about them, but looking at websites now, they look decent. Non-leather ones are sometimes too big and puffy looking. Some of the heavy leather ones, especially deerskin ones, look very much like the deerskin gloves I use here in Canada, that I got ages ago from Mark's Work Warehouse. Some motorcycling gloves with huge gauntlets look too bulky to be ideal but seem jumpable safely. In the end, no matter where your gloves come from, or who recommended them, you still need to make sure you can grab handles and toggles with some dexterity.

It does sort of look like that. Still, ya gotta be a bit clueless and/or have a crappy toss technique and/or be hypoxic for that. My first impression was that it looks like he hadn't jumped since about 1978... pull out that newfangled pilot chute and wave off with it...

The reserve attachment hardware looks reasonably strong to me. But what freaks me out a little on Russian style gear is the loose looking weave of the webbing, which makes it look like straps on a cheap backpack rather than the dense surface of many Milspec webbings. It probably is perfectly good, but it looks different...

See DN5A6015-001.JPG from the first post. Below the red cutaway pad, i.e., away from the 3-ring end of the harness, there are 2 "A-frame" shaped posts, part of the reserve attachment hardware attached into the harness. One can see a rod linking the two posts. When a reserve is being attached, the rod slides through a loop at the end of the reserve riser. So the Russian reserves aren't of a "quick attach" style at all; there's no hook or D-ring. The rod normally has a safety pin in it. Remove the safety, then with a push and twist one unlocks the rod and pulls it out. Once again, it seems logical enough.... but totally different than the US system. (I can't recall offhand if they use a cross connector strap or not -- since one shouldn't accidentally be able to unsnap one side.)

I won't say the name, as Beatnik has one and I have one (although mine has the older OSK releases). I do like how the Russians built their 3 rings "the other way around", putting the complex parts on the harness, not the riser. Reserve attachment point philosophy was also developed independently from the US.

Wow, really? So your Packer A's have to be ready to demonstrate setting up a sewing machine and sewing a French fell seam? Replacing lines? Sewing a properly folded patch on a canopy in an area that includes a seam? If so, you've got damn impressive Packers there. (I'm not really familiar with the FAA practical test standards, but I think I interpreted them correctly here, for the parts that apply to Senior riggers.)

A sort of Stockholm syndrome!

When my DZO got brand new rental gear (in place of the really old rigs they had), he clarified the policies with signs. The rental gear is always left unpacked with a bag to put the main canopy into. You rent it; you pack it; you don't get to complain that someone else's pack job gave you a slammer that messed up your neck, or gave you a mal where you are now responsible for replacing the main. It's a policy that's a bit unusual, but I sure see the DZO's point.

As a comment, I'm not sure the rules (whatever they are) are very clearly spelled out at some DZ's. It might also depend on whether one is a student or licensed. With skydiving equipment one does have the issue that with mals it can be difficult to apportion blame. All that can lead to conflict when something does go wrong...

I used to think the Y-harness mods were a knee jerk reaction to stupidity, for a miniscule number of deaths compared to other human activities. Well, I still think that. But after my ridiculously liability-conscious DZO introduced them, it sure makes me feel a hell of a lot better when I'm deploying with some fat-assed, limp-bodied student infront of me, even when I've cranked the leg straps deep into their flabby thighs. God some students are horrible, "it's like they've never skydived before". So I really do like having those Y-straps on the Sigmas I jump, just in case. (I like the way those Sigma Y-straps incorporate bungees, so the student can be restrained without stopping them from lifting their legs, as long as the strap isn't over tightened. Are Strongs like that? Too tight a Y strap can also pull the leg straps out of position while putting the harness on the student -- just a minor thing to watch for, to make sure the leg straps are properly positioned, and don't just appear tight because they're been yanked back by the Y-strap bungees.)

Ah, that's the "in" that shows up in the small words on screen bottom " next maint. in". If you didn't just see the screen for a split second and miss perceiving the first digits of the maintenance date, or the screen wasn't half obscured, or there's no apparent damage to the LCD screen.... then it is a bit of a mystery to me! If you cycle the unit off and on, did it come up again?? (Obviously one would rightly hesitate to jump any AAD if an error seemed to have happened, even if the error cleared next time around.)

The corners of the rectangle where a tensile test is done are marked in indelible ink. (And some other info is written in, if doing the round canopy tests exactly according to the National or PIA bulletins.) The tests aren't done on top of each other. Well, that's the assumption and what seems normal to do, but I don't recall offhand whether it is technically prohibited. Still, there are certain sections of panels on the rounds, next to the mesh, which are to be tested. If one actually has an old round in service that got packed a couple times a year and you did all the prescribed tests all the time ... by now you'd have a whole pile* of test points all over a 2 ft by 2 ft section. And those round canopy tests are 40lbs, not 30 like for PD's, so it is really starting to stress the fabric. * eg, not being quite exact with dates: (2012-1989)*2 = 46 pull tests per panel by now I don't pull test my Phantom 24's quite that much....

It is possible that for thinner, smaller individuals, the leg straps don't easily tighten right down. A LITTLE bit of looseness shouldn't be a problem except mentally. Leg straps don't have to be super tight, but you don't want too much slack from legs to shoulders either. Leg straps can OK being a little loose for example if the main lift web is snug so you are tightly contained from crotch to shoulders up against the shoulder straps. If there is looseness there, on opening the chest strap can ride up a lot and be up against your throat. Not a good feeling, not good for being able to look around, and dangerous if it went too far. That does happen when a harness gets too loose. (But you aren't going to fall out just because of that.) So see if there is other gear that fits tighter, or make sure the leg straps are absolutely tightened all the way (with one set of the ends of the leg pads folded away to prevent the leg pad ends from stopping the harness being fully tightened). If that's still not enough it gets trickier. A DZ might be willing to remove a bartack in the leg pad to allow the pad to slide back a bit on the strap, allowing more tightening. Make sure your instructors are aware of the issue so they can see what can be done. I've also heard of people finding pads to slip over the leg straps, both to compensate for crappy foam if the student gear is older, and to bulk up the leg strap area a bit. (The pads might be ones sold for protecting one's shoulder from a seat belt.) As for the fear that newbies get in the sport, well, that's a common issue and there are plenty of threads about overcoming fear. Hell, that's part of the fun of throwing yourself at a planet. And it's kind of a hazing ritual, as we experienced jumpers get to crack a smile at the newbies. Still good for you for standing up for yourself and deciding not to jump when you felt uncomfortable. It may cost you money and embarrass you but skydivers need to be ready to back down too. [edit:] P.S. - Standard procedure on dz.com is that if a slender girl is uncertain about gear fit, we guys request that she post photos of herself in underwear, so we can better evaluate the situation. That's also the way the world works...

I bet it is the "Recovery Systems Design Guide" from the then Irvin company, for the Air Force. Google AFFDL-TR-78-151

But can't the USPA ban something within its own environment, that is, USPA DZ's? (Whether or not DZ's listen to them.) E.g. the USPA banned batwings for a long time. It is interesting that the USPA generally doesn't issue directives on rigging issues -- unlike say the CSPA, BPA, and APF, whatever their relationships are with national aviation & rigger rules.