pchapman

Yes, well, you're lucky. Not all DZ's have a tunnel nearby that's part owned by the owners of the local DZ. The PFF program can be reduced from 1 pre-PFF jump plus 7 PFF's, down to just 5 PFF's (and fewer with 2 instructors) when 20 minutes of tunnel are included at the start. Conveniently, what's done at your DZ neatly matches what's in the new PFF manual. Probably because the guy who wrote the manual is also a chief instructor & owner at a DZ in your area, perhaps at your DZ.... Most jumpers have to do that 1 pre-PFF jump (tandem, IAD, SL) before being allowed to take the 7 jump PFF program. To skip the pre-PFF jump one can get a waiver from the CSPA. Probably not hard to get, but it shows that first jump PFF is not considered standard, unlike I think first jump AFF in the US. From what you say, it sounds like your DZ, even with its very good PFF program, still likes to see one tandem added on to the minimum number of jumps required. Tandem progression is also seen around at some DZs, with a number of working tandems before 1:1 PFF jumps. It requires a well organized system at the DZ. (i.e., not what I've sometimes seen, where the instructor is told while he's gearing up to catch the load, "by the way, your student is on level 3".) So don't look down on other systems just because you happen to be lucky to be at a very large DZ, with very professional owners, in a type of market that allows for a lot of tandems to help finance the DZ. [Edit: again, I'm making some assumptions about where you might jump as you don't specify exactly in your profile. There are other Montreal area DZ's too.]

Let us not forget that the Mirage TSO was originally for the Rapid Transit System; Similar situations. DRASTICALLY different timelines. Not sure if we're talking about a) the introduction dates for the Rapid Transit vs. early Paraphernalia Infinities or whatever they were called. or b) the introduction dates for the new Mirage vs the new Infinity. I don't know for sure when the new rigs were introduced, but from checking old websites on archive.org I get the impression that the new VSE Infinity was introduced around 1999, and the Mirage around 1998, or slightly earlier. Not a huge difference on that criterion. In any case, I'm not sure if it is better to be "newer" or "more established". So maybe the debate should just be about the current modern rigs...

I think that one had a dz.com thread of its own. It was a case where the formation was messed up after a small collision in freefall. Note that the guy doing the video, who nearly had a collision on opening, was looking forward and down for quite a while. Then he looks to both sides, throws in a quick barrel roll, and then sees someone deploying beneath & infront of him. One can argue whether he would have spotted the guy below even had he omitted the barrel roll.

Someone needs a new kicker plate! Has John Berry (as named from the youtube video) done a lot of round canopy jumping? Those Jumbo PC's are fairly rare and in demand. Impressive, a 58 year old reserve. I've had to ride a 36 year old round reserve, and jumped a 55 year old reserve as a main, but a 58 really goes well beyond! It did look like he did a bunch of right rear riser and perhaps a couple quick right toggle yanks while trying to fight the mal. Nice fast chop & reserve pull sequence, although it is hard from the video to tell what his body position was (seemed a bit upright), and whether he guarded his Capewells. The reserve opening sure is messy. It seems OK until one looks at things nearly frame by frame. Rounds can be that way, especially undiapered like his C-9. I saw the same in the photos of the two jumps of mine that I mentioned. There's the messy skirt, poorly tensioned lines whipping around, the temporary partial inversion. Yeah, there's a lot that happens too fast for the eye that you really don't want to know about. Here are some stills from this thread's video, during the reserve inflation: Kicker plate seen after the MA-1 pilot chute goes by: [inline j0.jpg] Canopy skirt: [inline j1.jpg] Lines: [inline j2.jpg] Temporary partial inversion: Initially it fills almost the whole properly inflated part! [inline j3.jpg] Temporary partial inversion getting 'squeezed out' as the canopy continues to inflate. Glad to have a very solid C-9 when the lower lateral band is rubbing across itself like that on an undiapered opening. [inline j4a.jpg] Slack lines, I think most likely as the last of the inversion works its way out. Maybe a bit of rebound / wake recontact. Hard to tell with the lens condensation. [inline j5.jpg]

I wonder if "stretching the lines" made sense in the days of ParaCommanders due to the high stretch of the 550 cord. To what degree lines actually took a relatively permanent "set", I don't know. (It won't quite be the same as just the elastic vs. plastic region for deformation of material, as we are talking about woven material.) When the industry got into Spectra, there some stretching is done at the factory. After all, one can't cut Spectra line to a consistent length unless one applies some force to take the initial stretch out of it. One reason to do a hop and pop on a new canopy is as a quality control check to see that it is flying OK. Perhaps safer at lower speed (and higher altitude) than at terminal (and lower down.) (And of course a hop and pop can be a quality control check for the jumper's piloting skills too...)

That is an interesting debate. We've already heard how the nylon pouch can create some line wear. On the other hand, for many people, elastic bands are used on many normal d-bags. And elastic bands are so grippy that they may cause some wear. Consider that service bulletin that came out years ago warning about harness damage when people put elastics on their hip rings to secure t-shirts when jumping without a suit. Lines don't purely shear against elastics however, as elastics flip and invert as lines pull out of them. Still, it is unknown to me to what degree elastics might actually cause line wear too. So one is comparing wear vs. wear, not wear vs. no wear at all.

Interesting post overall. Was GZ's prior behaviour in the neighbourhood watch ever brought up? Had be done much of that before? If the defence could say that GZ had approached and talked to various people in the past whom he had reported to the cops, and there was never violence, then they'd be able to say that he didn't have any expectation of provoking a dangerous situation. That would go towards a self defence claim. But had he followed people before?

Oh god. John Sherman really has to stick to what he knows, and know what he doesn't know enough about. - He's totally wrong on air being non-compressible. (And keeps on arguing the point.) For low speed aerodynamics though, say under 200 mph, one can assume air to be incompressible, allowing simpler equations that are still very accurate. - He's wrong on air being a liquid, and equating liquid with a fluid. Technically there is a difference, even if in daily life we might tend to mix the terms up. - He's also effectively wrong when saying that in parachuting, Reynolds numbers can be ignored, because we're operating at 50,000 Reynolds or below. Yet much general aerodynamic data is for much higher Reynolds numbers, where aerodynamic results can be somewhat different, so one wants to be aware of whether some bit of data applies to higher or lower Reynolds numbers. (And besides, without doing the math again, I thought skydiving canopies are often up in the 10^6 or greater Re number. Whatever.) Still, it is nice to see someone showing us outsiders their data acquisition methods and data collected!

One of course has to be careful in conversations whether someone means their "glide" as the true glide ratio through the air, or the glide ratio over the ground with the current winds. Half brakes is a lot. I'd rather teach that "in general" 1/4 brakes as usually increases the glide ratio, for typical larger canopies. Once you get into 1/2 brakes, really slowing the canopy but probably not reducing descent rate much more, then it gets trickier to predict without data. When you get into small canopies that are built to be ground hungry, built with nose low trim, there things change a bit. They drop out of the sky with such a poor glide ratio, that when applying 1/4 brakes or 1/2 brakes or even 3/4 brakes (compared to zero brakes), it may improve the glide ratio. (I know that sometimes someone under a small crossbrace, in deep brakes, can almost stay next to a student flying at full flight under some big boaty canopy. As soon as the small canopy's brakes are let up, it drops away steeply.) At least all this is impression from the numbers I've seen and my experience.

.... A company which unfortunately others are saying is out of business, in another current thread!

Either you are entirely wrong, or you are using English words in ways completely differently from most anyone else. You make it sound like the pilots have to be looking inside the cockpit 100% of the time. Maybe you mean anything above 1% looking inside is "to keep their heads fixed inside", or that it includes checks back and forth from inside to outside. But you aren't using words that anyone else can interpret that way. As for being "required to monitor" some instrument, well duh, that doesn't mean 100% of the time to the exclusion of all else. Hopefully, back to the discussion of the accident.

GE's flight idle is in the 40% N1 range. Whatever the details of the conversation, I hope there's no confusion between the engine speed % and the thrust %. It's not a linear relationship at all. Lots of RPM can still equal little thrust.

So it is projected area, as used more commonly in the paragliding world? Is that mentioned in Jump Shack info? Maybe I missed it! In any case, that is a huge, huge change in comparison to how other canopies are measured in skydiving. (e.g., the old debate about PIA vs PD measurrment style). So the measurement is still based on the physical dimensions of everything stretched out fully (as in a 3-D CAD drawing), but not with aeroelastic effects modelled (ie, spanwise shrinkage as cells inflate), correct? Using inflated plan form would create a smaller number than other companies have, for the same canopy. So for the same number, a Jump Shack canopy would tend (all else being equal, which it is not) to pack bigger and fly bigger. Please correct me or clarify as needed!

To be more helpful this time around: Yup, it is those approx 1/8" divisions that are the "squares". There's nothing sacrosanct about the difference between a 1 square long tear vs. a 2 square long tear, but "less than 1 square" in size is often used as a guide to what is a small tear not worth fixing. And that's true even in the PD reserve manual, for example.

Sounds like an evolving issue that we'll eventually hear more about, something where the specifics haven't been on skydivers' radar before. What differs for VSE risers compared to most others is the AMP fitting that integrates the grommet in the riser to the hard housings in the risers. Obviously that gets looked at too, whether it could have any unexpected influence.

The supposition is that someone with 100 jumps might actually have been close to a parachute, maybe touched the fabric, and considered looking at it. Unless the whole DZ only flies ZPX. .... OK, I just did a test. At 6' from parachute fabric, I can see the squares on it, with near 20/20 vision. The view is much better and clearer from about 3' away. So there are those who hope that someone with 100 jumps has at some time been within 3' of a parachute, with eyes open (and with corrective lenses if physiologically required). Edit: Usually I try to be nice to newbies. Today though, I'm feeling a little sarcastic. Time to get off DZ.com for a while.

They don't mention a cause, other than to say that the location of the wear can vary, and that there may be various contributing factors. So one infers that there might be some roughness on grommets on risers and cutaway cable housing ends, and thus on some grommet dies? Grommet problems are much more rare these days than 20+ years ago, before stainless was common and when standards were lower.

Poynters says approx. 180 sq. ft. for the 'Star. I don't have a manual and I've only seen a later Strato Cloud manual about (at ukskydiver.co.uk).

What I find interesting is how so many believe that that statement was a command from 911 not to follow. 911 may well have meant that. But they didn't say "Do not do that" or even "Please, we'd prefer if you don't do that". The phrasing used makes it sound like following or not following are both valid options. GZ could easily have interpreted the statement as, "We don't need you to do that. That's above and beyond what is required of a civilian. We'll send the police. But if you want to follow, we can't tell you what to do in your exact situation, and indeed it may still be a very useful action, but we can't specifically recommend following someone at this stage." It's like saying someone doesn't need to run into a burning building to save a person. It may be a stupid move or a heroic life saving move. But a 911 dispatcher on the phone can't well say that "you need to run into that burning building and risk your life!". This interpretation issue may have some use to the case as it affects the perception of whether GZ listens to rules & authority and was 'in control', or does whatever he pleases.

You're right that people can't be expected to know all the answers, even if their questions can be annoying. Even so, one hopes that people would have some idea that they're probably missing information about a field of human activity, and don't just follow ancient stereotypes. OK: "So how exactly do you steer your chute?" Not so OK: "You can steer your chute??" OK: "What kinds of competitions are there?" Not so OK: "There are competitions? All you do is fall. What are you competing in, not dying?"

See how far you've come? Now YOU are the one giving out advice on dropzone.com to newbies!

Fuck you! ... oh, wait...

But what's the answer? I don't know. Threaten to start bombing and invading? Well, the targets are too big for that. When Snowdon was in Hong Kong, should the US have promised to send Chinese dissidents back, on the principle that all criminals, political included, should be sent home to stand trial? Trade sanctions? It would be no good to the US with China, who knows what it would be like with Russia, and it would mean spirited to the world with the likes of Ecuador. Anything other than straightforward legal attempts at extradition etc. might make things worse for the US's image??

To add to that, to get really picky: For many years, they did require hand tacking in the Icon manual, but NOT in the Smart manual -- so it was not necessary for a Smart in another rig. But now the Smart manual does show it. (The manual that is labelled as being revised January 2010 but has pages labelled revised August 2011.... silly.)

But only for a year after expiry and only when buying a new unit.... something jumpers often forget when they cling to old Cypres'. (Cutters used to be the same as the rest of the Cypres but at some point they upped the life from 12.25 years or 12.5 years, to 14.5 years. So they go a little longer.)