pchapman

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.

Can you clarify this? Are you saying it wasn't just a plastic handle, but a plastic 'cable'? Not some sort of suspension line material for the 'cable'? Some early rigs did have cutaway cables that were not like the yellow Lolon stuff that nearly everyone uses now. Back in the early '90s I recall coming across an old unused rig with what seemed to be white (I think) cutaway cables. I tried to see the metal cable inside but the 'cables' were pure solid flexible plastic. Bizzare, I thought. Is that related to what you were writing about? Or is my memory off?

One DZ I know has a decent test chamber made out of plywood. Put a couple altis inside the window, use a vacuum cleaner and tap valve to regulate altitude, and use a stopwatch to measure the rate of descent. It's not aerospace quality but allows a DZ with a bunch of FXCs to actually do their 6 month checks at a low cost. I tried a few jumps with a bag of 3 FXC 12000's on my belly. I did continuous toggle spirals (trying for the fastest descent possible) under a Sabre 135. I didn't set off any FXC's at 1.3 wing loading, but when I went to 1.4, some started going off. While that's just a few jumps, it was encouraging to see that it took a fair bit more than student wing loading to set them off. (The book value is 46 mph vertical.)

As a private pilot, the many previously-mentioned items apply. Also, there's the mindset: Pilots learn to try to always think ahead to evaluate hazards, and they plan & practice for all sorts of emergency scenarios. This transfers very well to skydiving. You also learn that people you know will die in the activity. (Pilot & skydiving experience works the other direction too: Skydiving allows one to experience the air in a more direct way than many forms of aviation, leading to a better gut understanding of wind, shear layers, turbulence, micrometeorolgy.) Being an aviation person before jumping also convinced my instructor to let me do a short AFF/PFF style jump at a time when basically nobody else was doing first jump AFF's. The rest of the class did static line, I got a short freefall from 6000' for the same price!

Short answer: What Gary Peek said. Long answer: If you only work off the Protrack screen: 1. Don't use the maximum speed. It often picks up unrealistic spikes. 2. Use the First Half average speed, not the Overall average speed because the latter tends to include too much of the bottom end of the dive, which may include unrealistic spikes. 3. Use SAS speeds to better compare to others' data, and to one's own data from other days and dropzones. To delve more into the data, get the Jumptrack software so one can see the graph to better understand what is likely real, and what isn't. But there's still a big problem with the Jumptrack graphs: data averaging. The manual doesn't tell you that the data is smoothed by averaging over the previous six seconds. Some averaging is OK; the problem is that it uses the previous 6 seconds, rather than 3 previous, and 3 future. That means the speed graph result tends to be shifted about 3 seconds later than reality, which makes it very confusing to correlate any speed with an event that took place at a particular altitude. To get around this averaging problem, you need to look at the raw data, and then average as you see fit. I prefer a 3 second centered average as the best compromize between jagged peaks in the quarter second data points, versus over smoothing from using too long a time period. To see the original data and average as you see fit, either a) buy the Paralog software which I understand gives one a lot more choice in how data is presented, or b) export to a text file from Jumptrack, then load the text file into Excel to create one's own graphs. Regarding spikes in speed: I find that the Protrack, mounted on the outside of my Protec helmet, often records a many-second long acceleration to a very high speed, like 155 mph, when starting to turn and track away from a belly fly formation. Or, body position during a freefly jump can also cause spikes. For example, during head down practice where I was doing simple turns, and transitions to and from a sit, the Protrack recorded a couple big swings in speed. Supposedly down to 95 mph, and 7 seconds later, 185 mph SAS. I think not. When calculating the average speed of the dive (or the first or second half of that), the first 15 seconds of the dive is excluded. That's great, as it pretty much excludes the period before terminal is reached. But at the bottom end, only 7 seconds is excluded. That's far too little these days with high breakoffs, long tracks, and long snivels before one is slow enough to have the Protrack record that one has deployed. So the Protrack's overall average speed tends to include stuff at the bottom end one isn't trying to measure, including any unrealistic speed spike on breakoff. (I find the Protrack is fine for long sustained tracks, just not for fast transitions into a track from other activity.) Even the SAS airspeed won't quite be right unless one gets into dealing with air mass temperatures and thus density. Temperatures can be entered into Jumptrack, but that's excessive for most applications. Just accept that the Protrack has to make some reasonable and not perfectly accurate assumptions about the atmosphere, to translate pressure changes into one's vertical speed. So in some areas the Protrack on a helmet has its issues. Not all the issues will necessarily go away if mounted elsewhere. In other areas the Protrack is pretty good. I certainly see the difference in speeds between tandems with light, medium, and heavy people. Or the difference between an RW jump that felt fast, average, or floaty. I can see these differences even when just using the First Half speed, rather then checking Jumptrack graphs after the weekend.

Re: the canopy posted by pchapman Well I gave it a couple days so I'll say what it is. canopy.jpg depicted a Sutton Flow-Form parachute. I'm curious about it myself, and only know what I copied out of a 1987 Canpara magazine. The canopy was designed by Steve Sutton, who was on the Canadian team in '72 and apparently got a silver medal at the worlds in accuracy. He experimented with his accuracy canopy ideas for years, got a few patents, and by the time of the photo, was working with Strong Enterprises to develop the canopy. While the canopy never went anywhere, it is interesting to see that it got as far as being represented by a major manufacturer. The canopy is supposed to have various vents on "top and bottom surfaces, the inside ribs and the trailing edge", that may open or close depending on the mode of flight. It would be fun to track down the patents some day! It's simplest to attach a scan of the short article that accompanied the photo.

As for the Buckner parachute, I seem to recall the 3 suspension lines then cascaded, and the cascades included catenary style lines that were mainly horizontal, joining other lines that went up to the canopy. Difficult to describe, but it reminds me of a suspension bridge. Somewhere there's a better photo out there. Here's another canopy to identify.

I knew a girl and her boyfriend who were both advanced students at the DZ. She had her first mal, which freaked the boyfriend enough that he quit the sport. She continued on to get her license. (Not that long afterwards, she moved to another city, so the boyfriend was history, one way or another.)

Finish the story, will you! How many points did you turn?