pchapman

Thanks for all the background detail on filtering and smartwatch components, Yuri. Your stuff is always interesting. Westerly - Nice work spotting the issue that did turn out to be a bug!

"The elevator would stop moving and the door would be opening, but the altimeter elevation was still leveling out." Sounds much like simple averaging of the last few seconds of data to smooth out spikes and other random fluctuations in the data. Same applies for the 300-500 ft difference in freefall and 70-100 ft under canopy -- either way, subtracting a 30 ft static difference, looks roughly like a few seconds of freefall or canopy descent. The watch could use some other method than simple averaging, but in any case it seems like it uses a fairly wide time spread of data, and doesn't try to predict the current conditions based on some average using the past. At least the 30 ft difference over 10k (or even 2500 ft) ft isn't much in relative terms -- easy enough for any altis to differ that much. Of course we're using just a couple jumps as data but you weren't presenting the data as anything more than that.

@ the thread: I have always been a little skeptical about how much difference 'flattening the wing' makes, especially for non-high performance canopies. But it is the standard answer for want of a better one. Bringing the slider down can also change the 'feel' of the canopy, in cases where the slider is less wide and pulls the risers inward. Then there's the difference between 'dangling under the slider' vs. 'direct, widely angled connection from risers through lines to all of the canopy'. (To understand this idea, consider the extreme example of a slider 6" wide... you'd be swinging around under the slider almost suspended at a single point. Any turbulence or other canopy motions would be transmitted less directly to you; you would be less in-sync with the canopy motions.) This 'feel' thing becomes much more noticeable if loosening the chest strap where the risers do spread. The risers no longer are spread by the canopy 'from the chest' but 'from the hip' area. Loosening the chest strap can still have a benefit if you leave the slider up though. Loosening the chest strap won't make a docile canopy swoop, but it still allows one to move to a more upright position for landing when the canopy is flared back behind you. I've seen people with under a hundred jumps learn the technique of loosening the chest strap, and love it, allowing them to land better without almost tipping over backward. Loosening the chest strap isn't just for swoopers. (Although it should perhaps be introduced at a point where a jumper is getting comfortable as a licensed jumper, as it is a distraction after opening and increases the difficulty of finding handles in case of a canopy collision.)

Ok, fair enough, there are "a lot" of real numbers. The example with a rational one kept the example simpler, even if it wasn't exhaustive.

Best delivered in a stereotyped mobster voice. "... It ain't no threat or nuttin, I'm just sayin', do we understand each other?"

That's not actually true. Ok to close out this side issue, while I didn't read up on Lebesque integration, are we just talking about the following problem of 'common normal language' vs. 'precise mathematical definitions'?: - If we're talking about say physical objects in the real world sense, it you are picking out objects but have a zero probability of picking a particular one, then one is saying it is impossible to pick that one. So in normal real world use, it works -- probability zero is the same as 'impossible'. - But when one is talking mathematically, if one is picking say any number between 1 and 10, and are not limited to integers, but are using all real numbers (eg, 3.1415926535...) , then one has an infinite choice. So a random pick could possibly come up with "3.0" but has a zero chance of doing so because there are infinite choices.

[sarcasm] Love it! Poland started a war with Nazi Germany because it didn't give in to Germany's demands. Poland refused to negotiate on the Danzig corridor, the fools! Might is right! The US has more rights than others, because it's bigger! [/sarcasm] (And good luck with China by the way, hard to tell where that goes.) As for the Trump presidency, I'd actually be surprised if it didn't go full term. As a foreigner I'm a little surprised at how much the US makes the president a sort of king in his powers, despite how much 'checks and balances' are otherwise a cornerstone of the system. People aren't even clear on whether the president can be charged with crimes or disobey most of the rules of government...

For a crude, quick, ugly fix, I have sewn tucks in the seams of a d-bag to reduce it's volume. What I mean is to pinch an edge of the bag, and sew inboard of that edge. Getting a new bag might be better though, and then one still has the original to go with the rig when it eventually gets sold. (Of course one still has to be able to have good pin tension no matter what bag is used.)

I just looked at their website. To give them their due, it was actually "Manafort found guilty on 8 counts in fraud trial; mistrial declared on others". Not so bad. But it did come after the headline item about the suspected killer of a young white woman having been caught -- and he's an illegal immigrant. Say what one will about the details, I suppose a murder can take precedence over politicians' white collar crimes.

Sending by email. Bigger than the upload limit allowed here.

Okay, but uncertified skydivers aren't really the issue when dealing with the reclosing issue: If 6 different FAA certified mechanics were involved with a plane, is that much different than if 6 FAA certified riggers were involved with a rig? Still, the rules are what they are. Maybe authorities would be more forgiving if the system involved detailed logs for the harness/container as well as the reserve. Then each item of work could be logged by the rigger responsible -- although that still gets away from the idea of "one rigger only per pack job, because it's easier to find someone to blame that way". I have seen a couple European countries use logs for each component.

I always thought it was stupid that in skydiving a rigger somehow had to take responsibility for the whole rig. For the rest of aviation it it isn't like "Oh, sorry, I can't check your magnetos -- or even open the cowling -- because another mechanic did your annual inspection and now they won't know who to investigate if you crash". But I still stick to the skydiving convention for reserves because that's what the US & Canadian organizations want. Some sort of made up liability crap.

That has been a common concern. I figure the issue is minimized if using tube stows only for the mouth of the bag, where the 2, 3, or 4 stows tend to be well separated -- not like the rest of the stows lined up side to side. Also, I'd rather have a bag lock than explosive opening. Of course maintaining one's stows is important, but if they break every few jumps (eg double wrapped mouth stows with elastics in some cases), then the maintenance hassle is less if using something that breaks less often.

Good points. The friction in the lark's head should reduce the stress on the joint, and I also placed the joint in that area when using Stoes. Someone did once publish on the web his method of building the stows at home.

I got the PIA email so thought it should be mentioned here: There a new bulletin on testing retaining bands that are made of natural latex rubber tubing glued shut. That sounds like Tube Stoes (old name) or Tube Stows (new name). Technically it is an "Informational Advisory" from the PIA, not a mandatory bulletin or anything from any manufacturer. https://www.pia.com/images/rocketlauncher/PDF/SERVICE_BULLETINS/TubularRetainerBands8-3-18.pdf Noteworthy: The test to be done is to pull to at least 25 lbs (12kg) for 5 seconds, and pull to 9 to 12 inches elongation depending on stow size. The test isn't technically intended for ones you have in use, as they say to not make parachute rigging use of any that are tested. My comments: Not included in the advisory would be elastics like Silibands & Silirings that appear are moulded with no seam, and are also not natural latex rubber but are silicone based. I would guess that in practice people using stows will probably just adopt a less destructive and formatl procedure and give the stows a good yank and double check that they are not all abraded and close to failure. I do notice that older tube stows change colour to a darker brownish colour as they age. Storing spare ones in cool conditions away from light seems better. Regular elastics also degrade over time, but if well stored can be in pretty good shape for many years. How much to trust old stows is a bit more up in the air now. The whole point of using stows rather than regular elastics is that their life may be 100+ jumps rather than a just a few, especially when doing the stows at the mouth of the bag.

If we are getting into the exit order thing: I'll disagree with you. I still don't know how the BSR's matter here but I don't know the US ones well. And the guy may have meant the exit order doesn't matter IN CONTEXT for that jump, for where to put the wingsuiter and high pullers. He didn't mean "in all cases, ever", DUH. One could put the wingsuiter and high pullers out first or last, according to common exit order conventions. (Or indeed they could safely go anywhere in that load. Obviously more time needs to be taken by the presumably flat-fly high pullers if they went after the freefly group, but the same applies to tandems who may have cam flyers. Flat-fly tandems follow freefliers all the time -- but don't drift over them because they accept going a little extra upwind before exiting.) ========= Westerly, your bit about the coach rating was very appropriate though. The coach rating isn't about 'coaching everything' or 'coaching top athletes' but to address a particular niche for newbies. Canada has been doing it similarly for a long time -- I get the impression that the USPA got some of their coach ideas from the CSPA. The basic Coach rating here in Canada ("Coach 1") may be obtained with a very minimum of 75 jumps. Good for basic observation of a novice's skills. If someone gets huffy that "anyone with under 200 jumps really knows nothing these days", well, if a DZ has super high experienced AFFI staff to spare, nothing stops them from insisting that only higher experienced staff are used.

Now you probably know this, but to add to the above, here's one report: [From TheHill.com]

What's the name of it?

The UPT ones: Photo attached for reference. This was taken in 2010 so I don't know if design details changed. I never liked the concentric scrunched up bridle system for the kill line & bag retainer line, but the no-metal bag to bridle design looks nice.

How well accepted is it, to use a soft link or Slink to anchor the base of the main bridle at the deployment bag, instead of using a Maillon rapide link? I have occasionally seen Slinks used. A 2010 Chuting Star post said they assemble their rigs that way all the time, if the bag has a #4 or #5 grommet. Only a Reserve Slink is used, not a Main Slink. Recently however Parachute Systems issued a bulletin saying not to use that method on their rigs as they had a Slink pull through. (PSB-2018-01) So what's the acceptance these days of using a soft link? Well accepted? Only for #4 grommet? Not really, because it has been tried but very occasionally fails leading to a collapsed pilot chute? I hear that using a heavy duty key-ring style split ring seems to have some acceptance. Sewn bag-to-bridle connections work well but take a bunch of time to replace and 'standard' bridles are not set up for that. The standard Maillon rapide solution does tend to beat up the end of the bridle and sometimes the grommet too.

Yes, saying "you want a 7 cell" often actually means " you want a canopy which has been designed with the aspect ratio and nose inlets and thickness and other characteristics typical of historical 7 cell canopies that are built for conservative performance when it comes to on-heading performance and steering sensitivity" After all, PD Velocity & Valkyrie are "7 cells" according to the naming conventions we use, even if they may have 3 chambers between line groups instead of the traditional 2 for a canopy. I supposed fewer lines on a reserve might theoretically very slightly reduce the chance of tension knots, who knows. There have been reserves with 9 cells, but that's unpopular except for really big, heavy duty reserves where a few more lines could help structurally -- tandem reserves in particular. Nice to see you "just ask a question" instead of starting off with some (mock?) accusation and outrage about how the way the skydiving world works is all wrong and you have the superior way to do things! (Yes there are always things that aren't as simple as they seem or are confusing to the newbie due to how wording and naming conventions have evolved historically.)

I use Ultra Fine Point Sharpies, commonly available. The ink spreads a bit much if one presses too hard, but overall I prefer that over the uncertainty of ball point pens. Often with a ballpoint I had to 'prime' them by scribbling on paper first, before marking the Tyvek. But haven't compared the Sharpie to fancier ballpoints like that Zebra.

Edit: Ninjad by Gowler, who put pretty much my whole post into one sentence.

The old precision.aerodynamics.com is gone. The newer www.precision.aero is gone www.precision.net seems to be the (or "a") new copy of the site that works. Although the latest "News & Events" is still 2006. And some links fail, even to Service Bulletins. It may be tough to be a small skydiving manufacturer. But even for an older, simpler website, keeping it minimally updated would inspire more confidence...

Sounds like an editing issue in the laws. While I'm guessing it may have been intended to stop anyone physically interacting with the audience, it refers to only a regular performer, and is interpreted as referring only to regulars at any given premises. So newbies and out of towners on tour legally get to give an enhanced 'audience involvement' show compared to the experienced locals...