pchapman

Thank you! So it isn't an unheard of situation. I couldn't subsequently find the bulletin anywhere on the web, and haven't heard back from TSE. The matter was briefly mentioned in a report from the BPA riggers' committee (www.bpa.org.uk/forms/council/Riggers%2011th%20April%202002.doc). The report mentions a bulletin coming first from TSE.

And the pilot chute doesn't stay quite as nicely rolled and folded up at 120 mph as on the ground, which clearly adds to the drag too.

To me it doesn't look like something that could happen in a repack cycle, especially to stiff looking dacron line. But I'm not that experienced and can only speculate. In comparison, something like soft non-resin-treated PD Spectra line, now that I've seen all chewed up from a jumper leaving brake lines and velcro unstowed in a gearbag after having a mal. But even then there were few strands torn, just a lot of bunches of strands pulled out from the weave. In your pic, are the strands actually torn or just heavily 'fluffed up'? The location you showed would be hidden if a rigger didn't open up the velcro flaps that are used on some reserve risers to hold the excess brake line. Or if the inspection were too casual, it might even be hidden beneath all the folded line, with the flaps open. Curious indeed.

I figure the most important reason why it is easier to stall on rears than on brakes is because using brakes, the maximum angle of attack before the wing stalls is higher. It isn't really about the speed at which some angle of attack is changed. With brakes, the curvature at the back of the wing is like putting flaps down on an aircraft, which allows the wing to keep generating more and more lift by going to higher angles of attack where the wing would otherwise stall. (Of course brakes don't physically affect the whole span of the wing.) With rear risers, the back of the wing is pulled downwards, distorting the wing in an odd way. This does increase lift, adds some drag (though not as much as for brakes), but who knows how the angle of attack at which it would stall will change. In any case, it won't increase greatly as when brakes are used. So during a landing, one can get a lot slower for touchdown with brakes, than with rear risers. The original post mentioned how Germain's book said that the angle of attack changed quickly when using rear risers, and slowly when using brakes (as brakes took time to drag the canopy back and swing the jumper forward). I don't think he uses a "proper" definition of angle of attack. In aerospace engineering terms, the reference line is from the nose to the tail of the original, undistorted airfoil. (Leaving aside some details). This reference line is not changed when flaps or brakes are moved downwards, even though this changes where the tail of the airfoil is. So using the aerospace engineering definition, distorting the airfoil suddenly, whether by rear risers or brakes, technically doesn't immediately change the angle of attack at all. But, as the shape of the airfoil changes, the lift produced by it will change -- and as I described earlier, the stall point may also change. Germain said that the angle of attack changed quickly with rear risers, perhaps because I think he uses a different definition of angle of attack, a layman's definition where it is defined as the line between nose and tail, wherever the tail may happen to move. So pulling rear risers clearly moves the back end of the wing downwards, including the tail, so according to this definition, the angle of attack has increased -- it's almost like trying to rotate the whole wing suddenly. Call this definition the 'visual angle of attack' for want of a better term. But that definition still causes problems. Pulling the tail down with brakes by say 18" is deflecting the tail down a lot more than when pulling the rear risers down 6", and thus brakes would change the visual angle of attack a lot more. The words in the book just don't make logical sense to me. I find Germain's explanations generally to be a bit mixed up when it comes to understanding detailed aerodynamics, or explaining aerodynamics clearly. But that being said, he does have a very good feel for what is actually happening to the parachute. So I'd generally trust his conclusions, even if the aerodynamic background isn't always clear. And his book still puts a lot of good stuff together in one place, something nobody else has done. In the end, when it comes to rears vs. brakes for reaching the stall, I think the main reason brakes don't stall you as easily is that one can pull brakes a lot further without causing a stall, as brakes deform the wing in a way that is quite efficient adding lift yet avoiding a stall, compared to pulling down on rear risers. Rear risers may not be able to add as much lift as brakes can, but they can add a moderate amount of extra lift more efficiently (with less added drag) than can brakes. (Among prior answers, I like what quade and mr2mk1g wrote. They are using the visual angle of attack definition I think. That's fine, as long as we can all sort out what definition each person is using.) Phew, how's that?

Perfect, thank you!! That's the point I was thinking of making for phoenixlpr. Try running a static line first jump class and advertising, "Our main parachutes malfunction at least one third of the time!" :) Edit to add: Actually I do deal with line twists and end cell closures in the course section dealing with "issues", but I still don't call them "malfunctions". AFFI just mentioned the case of a student landing with line twists. Valid point there. Presumably that wasn't on the first static line jumps? It does sometimes get tricky to teach students who are are past the first jump, added subtleties about parachute problems, that one doesn't address fully in the first jump course. And even in the first jump course, students need to realize that if they can't properly control the parachute, and are still up high, they need to use emergency procedures -- even if they can't quite match their problem to something specific they remember from the course.

Yeah I figure it is an artefact of changing body position. When tracking for separateion at the end of a bellyfly jump, I fairly consistently get a big, wide spike to 140+ mph. While the body position and airflow changes aren't that big, the gadget is clearly getting fooled. As I've said in some other ProTrack thread, if you want to dig more, export the track to a text file, import into Excel, and do your own averaging. The JumpTrack graph bases its numbers on averaging the previous 6 seconds of flight -- so there's a lag as well as data smoothing going on. That confuses the issue when it comes to comparing a particular speed at a particular altitude. I prefer a centered 3 second average to avoid the lag, but still provide some smoothing. (So each point on the graph is the average of all the quarter second data points from -1.5 to +1.5 seconds). I believe the ParaLog program on the market allows a similar averaging.

So are you saying your buddy the DZO is wrong? That Fred should only pay if he packed a mal BECAUSE he had his head up his ass? That is, if someone can prove he was sloppy or omitted some step, he'd pay, but if the mal "just happened" with no apparent cause, he shouldn't? Yes, the DZO makes the rules. But one can always check what is normal in the industry and argue one's case. Everything he has written has been pretty respectful. He simply questioned how the policies at his DZ differ from other DZs, as he personally is not convinced all of them are fair. I believe the "shit storm", to use your own words, is yours alone. As for the actual issue of students and renters paying for repacks (or even a lost main), I think that is an issue that is very poorly presented at DZ's. I'm not sure that very many students and renters are told what the DZ policy is, before they make the choice to rent gear. Before getting into what policy is "right", the renter at least needs to know what it is. I'm not even sure what the policy is at the DZ I'm at. There is a sign warning renters that the previous person who packed the rig -- often another student or renter -- isn't guaranteed to have done it right! But that's more about hard openings or mals, and not about who takes financial responsibility.

I'm trying to summarize some of the types of accidents being discussed: One category is accidents that actually kill skydivers on flights where they planned to jump. I guess that's what the USPA tends to report on. That category is part of a larger category, which are all accidents (fatal to skydivers or not) involving flights where skydivers planned to jump from the aircraft. These are actual jump operation accidents. Then there's the category of accidents involving skydiving industry airplanes and pilots in any other way -- such as ferry flights. These may not usually kill skydivers, but skydiving operators still care if their planes crash. Jumpers aren't going to be as directly worried about such accidents, but they still are indirectly affected by the loss of pilots and airframes and insurance losses. And they should be concerned if the flight was brought down by maintenance or piloting issues that could well have happened on a jump flight instead. With different types and levels of skydiving related aircraft accidents, we may simply need to define different categories of such accidents. So we won't all agree on what should be included in one big aircraft accident category simply called "skydiving accidents". === On a different subtopic, another example of a jump plane flying into a mountain was the case of the small Cessna in British Columbia a few years back. On the descent after dropping jumpers, in an area of unsettled weather & cumulogranite, the plane disappeared. The crash site wasn't found for many months. While it was "not my problem" for the jumpers who had already jumped, I can't imagine the situation was much fun for anyone at the small DZ where it happened.

The article on risk has some interesting info. But in the part that dealt with skydiving, I think it was wrong. It suggested (based on who they interviewed) that there is a link between (a) reduced fatalities from AADs and (b) increased "hook turn" fatalities, and that that postulated link is explained by risk homeostasis. It is funny that it the fatality stats work out that way, but if we had small zero-P canopies but no Cypres', we'd still be hooking them in. And some people would still be late on their reserve pulls, despite others hooking it in. (I'm leaving aside minor links like small snivelly canopies being partially the cause of people pulling higher in general, that may allow more time to fix problems, even if the canopy is snivelly.)

I've heard that occasionally from the USA. Never ever heard about it locally (Ontario, Canada). Most local riggers do seem to note it on the reserve card when the loop is changed. But that gets into a whole other topic of rigging standards for another thread! It doesn't help that the Teardrop manual says nothing about how to build a new loop. (And the way the old loop was built is of course not guaranteed to be right.) I'll post again once I hear back from the manufacturer.

I recently repacked a Teardrop rig, built in 2001, where the fingertrapped reserve closing loop was getting a lot of wear from the grommets in the external pilot chute cap. The grommets are installed with the sharp ridge at the junction of the two parts of the grommet facing up, against the closing loop. It might have been better for them to have been installed facing the other direction. I replaced the loop, and the repack card indicates other riggers had done the same nearly every year. Is this normal on a Teardrop? (I've only packed a couple, and I am waiting for a reply from the manufacturer.) The photo shows the grommets, although the loop is already the new one.

... and my "free" t-shirt and sweatshirt, sent to me for doing a favour for a US skydiving company, cost me about $15 in taxes and customs fees because their full value was declared. In another case, I was fortunate that a reasonably well known US gear store was actually willing to mark my almost-new canopy as "returned to owner after maintenance", with a low value for "maintenance", thus keeping the border taxes down.

That last post shows a manual from 1994. I also received a 1994 manual when I emailed Thomas Sports Equipment a couple weeks ago. So that must be "the current manual". It seems like a bizzare company, at least to someone like me in North America with little exposure to it. The company has been around a long time, and they have interesting rigs that at first glance seem to be carefully thought out. (Especially compared to the early days where I thought I recalled them basically doing copies of common North American rigs.) Their web site has no manuals, bulletins, tips, or any of those things one expect to see from a manufacturer. Riggers need to be able to confirm that they are using the most current approved instructions for a particular rig. So it seems there's only one manual, 13 years old, that covers all their models...

I largely made my choice of first DZ based on the information that all the local DZ's had available. As this was in '88, I was looking at their mailed brochures, rather than websites. I went for the DZ that put the most detailed information in their brochure, and indeed even put injury statistics in. (This was the Grand Bend Sport Parachuting Centre in southern Ontario, Canada.) This was in contrast to most other DZ's, that often seemed more oriented to marketing than information. Most DZ's trumpeted how they had big safe soft landing parachutes and whatnot, but didn't really say much about why their systems or methods were safe or at least safer than the other guys. As a somewhat techy guy, I was impressed by the DZ that would dare mention injuries, and also give me the most detail about how jumps would take place. I'd prefer a realistic appraisal of potential dangers over marketing hype. I wouldn't be surprised if there are a lot of people whose selection criteria are quite different.

While it may be the ideal, I find going for the low man doesn't happen much if it is in the jumpers' self interest to not do so. If it's a bit of a zoo (the formation fallen apart), but everyone is generally in the same chunk of sky, the low man is someone logical to start rebuilding on. But if a fun jump one-point 8-way formation is almost complete, and one person goes a little low, the rest think 'tough luck' and contine on with at least getting a nice 7 way together. They'd rather fly what they've nearly got than try a tricky restart from scratch. Although if they're all paying attention, they would try to punch it out (arch more & fall faster) to help that little-bit-low guy get back up. Certainly they don't break the 7 way and go into a massive dive bombing attack on a guy who is a hundred feet below! So it could be quite dangerous if the "rule" were drilled into a newbie's head without also emphasizing it's limits.

It's a little disappointing to see the way United Wonderhog Technologies (or whatever their name) wrote their bulletin. First the nitpicking: Page 1 says #300107. Page 2 says #301007. Both pages say "Quality Assurance Department."... The bulletin does not note that it is changed in any way. The number is the same, the date is the same... but the content is different (adding the clear heat shrink). I've already complied with the first version of the bulletin, but now my work doesn't match what I wrote down as having been complied with. Finally, they continue to make the whole bulletin mandatory before the next jump. So one can't jump the rig unless one has gone out, searched around, and found the right type of heat shrink. Sigh. [Edited to add: I don't want to be harsh on them, but any sloppiness in writing a service bulletin has a significant effect, especially on any rigger trying to do things by the book, as the FAA expects.]

What's the background on this whole recommendation from Sun Path? Most rigs are used just fine with or without an RSL. Do the owners just personally like RSL's a whole lot? Is there some particular fear of a lawsuit if they don't make an RSL available? Or do they just dislike it when someone removes the RSL without doing anything else, leaving the hook velcro to chew up the opposite reserve riser? As a rigger I dislike that too...

I came across a pilot chute pouch of a type that's new and odd to me. (This is a trivial post, but this is History & Trivia...) It's a square nylon hip mounted pouch, with central slot from which to extract the pilot chute. In the evolution of rigs, it looks like it is past the cordura belly-band stage, but prior to the Spandex leg throw-out stage. I only looked at the rig briefly, but it's a British rig from the early 80's, a Wonderhog-style rig that I understand was built by GQ. (The bottom of the rig shows evidence of later conversion to a pull-out.)

To expand on that, it's not always a one way road towards smaller and less safe. The pendulum may swing back and forth on issues, due to some ever changing combination of fashion, safety, convenience, cost, common practice, technology, group mentality, etc. Sometimes the desire for some good attribute gets taken a little too far. Hard helmets gave way to lighter frappe hats and later often to the freedom to jump with no helmet at all. But then the hard helmet came back, even adding on face shields -- not simply due to some supposed rational logic about safety, but also newer lighter technology, and things like faster 4-way. Another example is the quest for lightness, as the sport evolved from the heavy 1960s military equipment. Some containers could be purchased that were just thin parapack, to shave weight compared to cordura. Some reserve canopy designs (rounds) got so light weight that they were later looked on with distrust. One example of the pendulum swinging back on this issue was when the popular lightweight Phantom round reserves had to have extra Kevlar bands sewn to them. Soon it didn't matter much, as jumpers went to square reserves with different issues. Jumpers now don't mind the weight of a solidly constructed rig, or having extra reinforcement tapes adding bulk to their reserves, yet there is pressure to have as small a reserve as one can get away with.

Trying to put the video in perspective, it isn't like it showcases world-class skydiving. (I jump at Skydive Toronto and have seen the draft video.) It's not like Skydive Toronto is a major southern US dropzone. The video is about the jumps and the fun that jumpers had at our DZ in 2006. It's all stuff that matters most to those of us who were in the jumps or have friends in the jumps! All the best stuff that got filmed is there (well, except for a couple deletions for things the DZO really shouldn't see, and perhaps shouldn't be repeated). That being said, the guys who put it together - Bart, Marc, and James - spent a huge amount of time on it, learning more about the professional quality software used, trying to get all the clips just right (arguing down to the point of individual video frames...), editing multiple viewpoints when there was more that one camera on a jump, finding good music, and so on. So look to the video not for world beating skydiving, but for what should be a fun year-end DZ video that's really well produced and shows off skydiving well. Although Skydive Toronto has sent a bunch of jumpers to the world championships over the years in accuracy, freeflying, and canopy piloting, we're not a famous bunch. Well, except for Jay Moledski and Johnny Zuliani, who both started at Skydive Toronto... Wish we had video of them being guided in by radio on their first jumps!

Well that sucks... for instructors with under 500 tandem jumps, having to do a tandem within every 30 days, or else have to do a recurrency jump. Ninety days I've gotten used to, so that every spring at a northern DZ we instructors have to do one of those tandems with an experienced passenger (at our own cost with rig rental, at the DZ I jump). I'd find the 30 day rule a big annoyance to worry about, if people actually bother to follow the rule. Although more likely to be an issue in spring or fall, even in summer it could come up. Maybe an instructor can be jumping at the DZ only every second weekend due to other commitments in life. Then if there's even one jump weekend away at another DZ or boogie (or focusing on other types of work & instruction at the DZ) and then there's a weekend of bad weather, bang, the instructor needs another recurrency jump. It seems to be another example of creeping "professionalism" in the sport --- Good for some, bad for others. I'm actually Vector/Sigma rated only (and maybe 400 tandems), so I'm just hoping such requirements don't spread any further.

Here's a pic from ParachuteHistory.com where there's a page on it.

In defence of simplicity: Around my DZ the feeling is that one doesn't need a design with tabs sticking out far to both sides of the type 17 risers, or some fancy downwards facing hinged tab as has also been described. Sometimes the ones sticking far out to the side are just too stiff, and a pain to get the slider back over, when trying to pack. (Brian G.'s might be flexible enough to avoid this. But they still aren't the prettiest, if that matters.) Locally it seems sufficient to just wrap a piece of webbing around the riser! Or, I think, even just sew a couple layers of webbing on the front of the riser. Just about anything catches the narrow stainless slider grommets. This is especially true when yanking the slider up or down, and the slider grommet is on an angle, rather than being perfectly centered and perpendicular to the risers. (Brass grommets, a bit wider internally, might need a bit wider slider lock). I'm not advocating any particular design, but that's my amateur observation from building a few slider locks over the years. Attached is a pic of one I made earlier with a simple wrap of a thick non-milspec webbing around the riser. I made it stick out a bit from the sides, but it caught the slider too well to be convenient when packing - so one side was hacked off with a hotknife. A newer one wouldn't be made to stick out any more than the thickness of the webbing.

The Jump Shack PC drag claim has been around a long time, so I'd like to confirm that the comparison is against other types of PC's that are in current use. Also, Cd on its own is not enough. One could have a 6 inch diameter pilot chute with great Cd drag characteristics, but much less drag than a 42" PC. It's the combination of Cd and a reference size (some measure of diameter) that makes up the total drag.

It has been mentioned how other sports seem to exist just fine in the USA with kids involved, but with the counter argument that skydiving is different in terms of actual risk of death, rather than just injury. But even compared to other forms of aviation, skydiving is more restrictive. Teens can solo a powered airplane at 16 (with instructor supervision), and get their full private license at 17. Or solo a glider at 14, with licence at 16. [USA & Canada numbers] (I often heard tales of how some airline pilot's son or daughter soloed a dozen different types of aircraft on their 16th birthday.) At first glance, businesses teaching people to fly seem to have no more problem with liability with minors than with any other newbie.