pchapman

Good question about the fabric. In skydiving, companies never really tell us. If one were in paragliding, they would tell us. E.g., one paraglider material was GELVENOR LCN 0517 (C 17 ) 6.6 µ , nylon, 45 g/m^2. Edit: Looks like Southern Man posted first -- and presumably actually knows the answer!

Hello, Rhys, where are you?

I haven't done my homework, but are any of the candidates not way over on the right on social issues? It would be nice to have a Republican contender who was right of centre on economic/fiscal issues, but not a stereotypical Christian fundamentalist nutjob.

That's interesting. Here's the intro for reference: It appears to be a new 'diagonals at the shoulders' stitching bulletin. It's the first new UPT bulletin since their May 2011, which was this one: So the old bulletin was for the single person rigs. They updated the single row of stitching after that, to go to the "E" shaped stitching-- like had already been used on the tandem rigs "for some time". (From the bit I saw in the field, it seemed mainly big rigs that had stitching tear. Small sport rigs 10 years old had no problem, while I had to repair a couple 2 year old student rigs.) Now the new bulletin shows a case where the "E" stitching ripped out completely on a Sigma. It had been well used (including a hard opening), and they also found that the stitch pattern on some rigs may not be as tight as they had intended (stitches per inch). In practice at repacks, one is going to inspect that location on all rigs (although construction varies), and pay particular attention to UPT rigs.

You also have to distinguish between fatalities of students, and of experienced jumpers -- the latter being less under the control of the school and more responsible for their own actions. Since fatalities are relatively rare, for medium to small schools the outcome can appear totally random -- a dropzone might have no student fatalities for 30 years, or one that just happened to be in the last 5 years. While schools vary in the age of equipment, the level of facilities, and the experience of instructors, it is pretty rare to have a really bad school.

There are plenty of reasons why it costs. But you have a point, in some sense, skydiving is very simple. Fall out, pull, steer, flare. Pull a couple handles if there's a malfunction. Skydiving is super easy if you want to treat it like an emergency procedure. A pilot can bail out and make it down alive without training. And that would still apply if you give him a big square parachute not a round parachute. But in skydiving we train for all the little details to reduce the chance of not finding the handle, tumbling in freefall, not flaring right, malfunctions, etc. Nowadays we know more about falling out of airplanes, so we teach the little details, and it isn't OK to have a first time jumper death once every thousand jumps, or break ankles on 5% of them. Those are great statistics if you are a pilot of a burning airplane, but lousy for the sport of skydiving. Skydiving like other sports has its rules. We don't have complete freedom to do whatever we want. Part of that is because of the flying part of it all -- there are plenty of rules in aviation, we use the national airspace system, etc. It differs country to country. So our activities are often partially regulated by national laws. It is true that in some countries, if you did find equipment, and just found a pilot who you weren't paying (so that he wouldn't in effect have to have a business license for dropping skydivers), you could go jump into a friend's field with no training. You probably still have to follow some airspace rules about where and how the drops would be made. In some countries like the US and Canada, the sports organizations running skydiving are voluntary, so technically if you stayed off of dropzones owned by members, you could go learn on your own. But in the end, people go to where the infrastructure already exists and join national organizations and play by their rules. Since we integrate into national aviation & airspace laws, it isn't like rock climbing where you could hike into the back country and do whatever you want, live or die. (Yes there are land use regulations that can affect climbing, but I'm talking in general.) There are a lot of things in skydiving that aren't particularly "difficult" -- but there still are an awful lot of them to learn. And like many physical things, it is hard to learn out of a book or even youtube due to the lack of feedback in the learning cycle. You probably could learn a lot online, but when you come to a dropzone, they still have the standard packages for a standard price. You wouldn't go for a scuba course and say, "can you give me 30% off, because I've read every book I can on scuba and a buddy showed me some stuff." You'll probably end up paying the same as everyone else, just that you may progress faster and need less instruction down the road. But you still have to be tested and evaluated on your knowledge. The caveat is that without feedback while learning on your own, you can get all sorts of things slightly wrong -- so you end up taking as long to retrain and get the wrong ideas out of your head. While there is a lot of info online on particular skydiving skills, it would be rarer for there to be any complete first jump course from A to Z. While there are national organizations, every skydiving program is slightly different and suited to different equipment, aircraft, drop zones, and instructor preferences. So there is no such thing as a single book for a standardized national course, whether you pay for it or not. To have a big piece of land, parachute equipment, and aircraft, costs a lot of money. Somebody's gotta pay for that, and a lot fewer people want to skydive than want to go to an amusement park. The costs are spread over fewer people. You can pay about $300 for a first jump course, and only a small fraction of that goes to the instructor. As you make more jumps, the cost goes down and you contribute to the overhead costs a bit at a time as you are not just there for one jump. So the the huge amounts of money sure aren't going to the instructors. They're working for their money just like the guy who offers kitesurfing courses. I don't know about kitesurfing, but skydiving instructors do need to get various certifications for coaching and instructing depending on their role. Planes are very expensive to a significant extent because they are built in tiny numbers compared to say cars. And there are more rules about maintenance, than even a school bus I bet. Another thing you'll pay money for is to learn the techniques to jump with others in the sky, to learn the fine maneuvering skills required to dock on each other, and the safety procedures not to crash into each other in freefall and under canopy. (Aside: Skydivers know we're still working on that last one.) It isn't just about falling out on your own. In the end, pay to go through the system like everyone else. If one is a diligent student, that can speed one's progress a little and keep costs down in the number of jumps needed to get licensed. But there are no guarantees. =========== Edit: I gave a serious reply but there are some good humorous replies in the thread too. shah wrote: Skydiving is even easier once you find the cheat code. Pull down, down, left, right, left, right to get unlimited lives!

A perfectly good question, although best for History &Trivia. The short answer: It goes back to at least 1918 when discussing parachuting from said airplane. And at least 1910 when using earlier names for airplanes, although probably not with reference to parachutes. The long answer: One question is how unique it is as a complete phrase, because "perfectly good" is sometimes used with other things. But to what degree? Sometimes there is an originating point for a phrase -- like how it looks like BSBD could have been inspired by a specific movie tagline from 1971, and then just happened to fit with the skydiving culture of the era. Even if it isn't known exactly who said the phrase first. Online searches certainly show the "Perfectly good airplane" phrase to be in common use, not just by people talking about skydiving. For example, an MIT aerospace engineering professor used it when discussing a recent airline accident. Plain web searches tend to get stuff written in the past 20 years for obvious reasons. So I went Google Books search, where I was surprised to see some really old uses of the term. Such as in Boys Life Magazine in 1930, or a story in Popular Science in 1928, or in the American Garage & Auto Dealer magazine of 1921. But none of those references applied to parachuting. It was used in reference to skydiving in New Yorker or Esquire magazine (I don't recall which) in 1968, so the idea was in circulation among a non-aviation audience. But the best I could find for talking about parachuting, is from the United States Naval Institute proceedings, Volume 44, Issue 2 in 1918, where they had a quote from someone writing in Scientific American (in 1918 or possibly the year before): Only a snippet is available to view. A full paragraph can be seen in my attachment. The writer suggests that giving military aviators parachutes is a good thing, that they are responsible enough not to abandon perfectly good airplanes. But do you really want to limit yourself to today's terminolgy? What about a "perfectly good flying machine"? In that case, that was mentioned in Practical Aeronautics in 1912 and Scientific American in 1910. The scanned text resolution in the latter case was unfortunately too low to figure out the context. If someone can find an earlier reference, be my guest

Whoah. You're getting at the issue of a "non-destructive test" in a general sense, and "Non-Destructive Test (NDT)" in a technical engineering sense. So we can have different levels of testing: 1) tests that are non-destructive, even to items that are tested "bad" (weak, damaged, out of spec, whatever). (e.g., the ultrasound, magnetic particles, x-ray, or whatever doesn't cause damage in any case). You're making the point that that's true NDT. But there's also: 2) tests that are non-destructive when the parts are OK. So you can do a 100% sample and not destroy every item that comes off the production line. However, for a bad part, one either: 2a) destroys the whole item (e.g, the cable failed the tensile test, it broke) or 2b) destroys only the section of the item being tested. So it isn't destructive to the whole item, just the section being tested, so that one can theoretically save the production item by fixing the section that failed. (e.g., ripped canopy panel, or other localized damage to the tested item) I'm not sure we can use the term "destructive testing" either. I may be wrong, but that is normally defined as testing something to its breaking point. For us, that would be ripping every spot on a canopy we test, and recording the breaking strength. So we need terminology for something in between. Then we can better argue about whether TS-108 is a Locally-Non-Destructive-To-Good-Items-But-Locally-Destructive-To-Failed-Items-Test. (Note: I have no certifications in any of NDT, DT, or LNDTGIBLDTFIT.) P.S. That's interesting about actually seeing reserves fail at pull test locations.

Ok, I got the word back from Aerodyne. Initial emails from them did somehow get spam filtered but things got sorted after the holiday break. It looks like one does have the option whether to use the triangular folding or not. I guess with the triangular option, one would add some arguably insignificant twists in the bridle. From their email, my emphasis: Where there is a Skyhook, their 2010 manual showed up and down folds for the last part of the bridle, but their Aug 2011 manual revises that to side to side. A minor detail. They also now know that the older Icon manual was accidentally removed from the web site; they'll put it back. Not sure about misprint issues in the new manual though. The Aug '11 manual didn't distinguish the old Icon from Icon Sport from Icon Pro, so that remains to be made clearer once they update things.

Interesting. I double checked the TSE manuals, which seem only to say that their rigs "should" be returned for inspection after 10 years. In other words, I'm free to ignore TSE; there's no mandatory limit. Don't know if that's different for anyone in the UK due to other BPA regs. (Nice thought there councilman -- keep one's 1st rig normal... and go weirder as one accumulates rigs & knowledge.)

Firelites are OK. They fly fine if not overloaded. There was a main canopy version that seemed to be common enough back in the day. Under 1:1 wing load is no problem. I personally don't like the design style with line attachment flares for a reserve, but the canopies and similar ones were very common. (And indeed continue to be built, although are rarer.) I'm not in tune with UK gear so wasn't aware there ever was a 2 pin Teardrop. They've built 1 pin Teardrops for many years with no mention of 2 pin ones on the TSE site. However, the 1 pin Teardrop has often been called a "1 pin Teardrop", suggesting that there was a 2 pin at one time. I bet the 2 pins are rare even in the UK. Your profile isn't filled in so we have no idea which country you are in. Thomas Sports Equipment gear is very rare in the US for example. As others are saying, we can't evaluate the rig without knowing exactly how it was built and what modifications it might have had -- AAD pouch, main & reserve pin protection, bridle stowage, pilot chute stowage, riser protection. If the rig is OK, whether for skydiving in general or just belly flying or whatever, the price better be low enough to account for any limitations compared to newer gear.

Depends on the rig. In some brands the cutter is at the base of the loop so when the reserve is out, the loop is still in the cutter. In other rigs, the cutter is on one of the flaps, so the flap moves off the loop when the pilot chute jumps out or the freebag is pulled out. Then the cutter would close and cut nothing. Have a rigger show you some day if you can, to understand the internal parts of rigs better.

It's a complex situation and most of us just don't have data, if we don't have access to military reports etc. I myself have just scratched the surface of it all. Clearly some military practices are conservative and equipment is just tossed without spending the time & money to test each set of gear extensively. Nylon does degrade over time though - more on that after. There's also the problem of how strong equipment needs to be, and how things are certified. If a harness is certified to 5000 lbs, does that mean it should be condemned if it tests to 4900? Or is the thought of age and wear built into the initial calculations on how strong a harness should be? Typical certification standards specify initial values but not what kind of safety factors are built in. (Other than say testing to X % extra weight and speed.) So even if we know that something lost 10% of its strength, we don't know if that is acceptable. Reserves are of course tested brand new, and fabric isn't excessively strong to begin with, so there there will be more concern over even small amounts of strength loss. E.g., say we have a one size fits all 40 lb test for old rounds, but one is looking at an older canopy that used fabric that was only a 42 lb spec to begin with instead of a 45 lb spec. Is it really a non-destructive test even on new fabric, with non-professional test methods? Is the test fair for the older style fabric? And what if older canopies could take a 35 lb test only, just how bad is that? Even in aircraft there aren't clear standards on how strong is strong enough. You can operate a 1946 light aircraft with wooden spars, or a WWII fighter. While you have to inspect for spar corrosion or cracks, it is legal to fly them, even if everyone would agree that flying them hard, right up to their certification limits of strength, might not be the best thing. Since I don't have a coherent overall theory on the whole issue, I'll just throw in a few odds and ends: 1. From some web site on textile chemistry by the American Chemical Society: 2. Attachment 1 is from a 1968 US Army Technical Report 68-45-CM on nylon aging. It notes how their parachute fabric improved in 1963 due to new heat and light resistant nylon, and suggests that the nylon continued to be improved. So the inherent quality varies with age of manufacture too. 3. In the same paper, small strength losses were seen over time, along with an increased dispersion of strength within a large sample. But the evidence was messy and can't be summed up easily. 4. Attachment 2 is from a circa 1994 paper on "Storage Life of Parachutes" by a US lab associated with the military (Sandia Labs). It concludes that strength losses in 25-30 year old parachutes are very low based on previous research, and they found no real strength loss in one particular 29 year old canopy. Yet some strength loss was seen in some cases so as usual the paper calls for further research.

A local instructor: "If the wind sock has a hard on... somebody's gonna get fucked." A rule posted at a boogie: "Deploy at least one parachute before impact." Instructor to me, when I got signed off for the A license: "You now have a license to kill... yourself."

That's a fairly novel reason for a mal, not being able to reach due to sore arms from a day in the tunnel! On final, having the DZ visible in the distance ahead is an interesting little visual cue to show that one may be heading downwind, given a normal spot. Looks like about 30 seconds under canopy.

Plenty of companies have developed GPS guidance systems for parachutes. But finding something off the shelf for rocket recovery might be an issue. I agree, dorbie, that it sucks to develop the recovery system at the same time as the rocket. It's like an untested engine on an untested airplane. But sometimes, there isn't much in the way of good options. Thanks for the writeup, Lee.

GPS & computer & servos added, so it can fly back, instead of having to chase your rocket across miles of desert...

Fun to see some parachuting stuff beyond the usual sport skydiving. Guess you must have a copy of Knacke in addition to the usual Poynter's sitting on the shelf. Where do you find other design guidelines? AIAA Decelerator Systems conference papers might help a bit, but really one would need contacts with others who have done such high speed work. The ballute sounds solid, 5.5 oz Nomex, lots of Kevlar reinforcements, even if it didn't work in the end. I'm curious how the ballute is deployed, and sequenced relative to whatever the rocket is doing near the apogee. What was being used as the descent canopy? Custom built, or an old tandem main, something like that?

she is a beauty. Love the blast handle

OK, YOU don't, with 400+ jumps. The idea is for NOVICES to learn to feel the canopy without the visual distraction. It's a teaching technique. The specific numbers and timings reported for the SIM are a bit odd. One should be able to get the right effect by closing eyes and doing one flare, taking one's time (no 3 sec rush), and opening eyes to check one's surroundings between each flare attempt.

I don't know to what degree pilots follow the rules nowadays, but that'll learn them to wear the appropriate clothing for the outdoor temperatures. One hears stories like 'there I was, out of control over the snowy Sierra Nevada mountains in a t shirt & flight suit, hoping I wouldn't have to eject'.

I'm sure they can, but good luck to them. When I got my rating, I never saw any paperwork saying I had to do anything any particular way. No federal law, nothing I could see in the PIMs. But of course we are all expected to be conscientious in our work -- So if I deviate it'll be for a reason I can defend as an acceptable industry practice, or something following the intent of the manufacturer even if the words are wrong. Edit: Hey Rob, after we debated the "follow the rules!" issue where we both took hard lines with it, now we're back to "what is reasonable for a rigger to do".

Re: the freefall stability debate I'm not sure there is one simple answer as stability can vary so much -- a novice can fall really stable, or start spinning or tumbling wildly. I think some of the worst spins happen to those who are trying to fly arched, belly to earth, which would be what a novice skydiver would try to do -- but not necessarily someone trained in military bailouts. Military aircrew in the WWII era may have been trained to dearch in freefall, essentially falling on their back. The US did some high altitude bailout tests in WWII to look at the issue, as aircrew often bailed out high (say, 20,000'+) and delayed opening until down low (say well under 10,000'). I really don't know any results or statistics, but in emergency bailouts they didn't all go spin themselves semi-conscious and not pull. Having a bag tied on one's belly will be less destabilizing if one is dropping dearched on one's back than arched on one's belly. The degree of destabilization or stabilization also depends on the weight & density of the bag. I'm not sure how dense a bag of paper bills is, and how tightly wrapped they would have been. Without considering other factors, this gives different possibilities for what Cooper would try to do, depending on where he acquired parachuting knowledge. In conclusion: I think that so far, not enough weight has been put on the possibility of him intending to fall on his back (if he didn't pull right off the ramp). I don't know for sure, but for someone with a pouch on his belly and minimal freefall skills, falling on his back could increase the chance that he would be relatively stable and not turning all that fast, compared to being on his belly. Edit: of course the high exit speed wouldn't help getting stable. But at least look at IAS not the higher TAS.

The 2010 Aerodyne Icon manual shows a method of folding the reserve bridle in a triangular shape, something they never had in their manuals in the past. The first part of the bridle is folded in a V fashion as it long had been. The part ontop of the kicker plate is no longer side to side but triangular around the closing loop. I'm wondering if everyone is following that, or if Aerodyne allows one to fold the bridle in the previous more conventional manner? Confusing the issue is that on their website, there's a single Icon manual, now revised Aug. 2011, but it shows Skyhook only. It explicitly states what sections are for the Skyhook version -- but there are no other sections for no skyhook. One can take the Skyhook sections and guess what might be done without -- in which case the last bit of bridle would be folded side to side directly under the PC. Aerodyne just presents one manual, and doesn't seem to say anything like, 'follow the manual that was current when the rig was built'. Technically Aerodyne is all screwed up -- if one is an FAA rigger who has to legally follow the manual -- it would mean one cannot pack any Icon without a Skyhook... So, realistically, what are people doing for Icon's without skyhooks? a) the old way - last part of bridle side to side on the bottom of the kicker flap, partially under the PC b) the 2010 way - last part of bridle triangularly c) Skyhook way - last part of bridle side to side directly under the PC I'll probably go back to (a) as it is a common industry technique. Another issue is that the triangular folding method will twist the bridle -- half a turn every fold. The text says nothing about alternating folds over and under to prevent this, or any other method to prevent it. The photos don't seem to show any way to prevent it either, although they are too indistinct to be sure. What do you do about that? Seems pretty silly to put something like 3 full twists in the bridle. Aerodyne's instructions also seem to assume no extra reserve lines will be left over once one has put the stows in the elastic tubes. Sometimes one does get an extra fold of lines left. It seems reasonable to just leave the extra stow loose in the pouch like any other system, but their instructions omit this possibility (again leading to one of those 'technically impossible to follow instructions' situations.) Yes I did contact Aerodyne. Emailed them nearly a week ago and heard nothing. There could be a reasonable excuse, busy staff, wonky spam filters, whatever. While I'll try again, I'll ask here too. I'm not an FAA rigger so don't legally have to follow the manual. But these sorts of screwups piss me off because they put FAA riggers into situations where they can't legally pack a rig, or have to do something stupid when packing them. FAA rules don't allow for "common sense" or "industry standards". Correct me if I'm overlooking anything here.

Interesting to see the US has gone this route, to get students altimeter oriented from the start. Canada still uses the traditional way of not needing it for under 15 second delays. While there is some added safety in having an alti, one traditional reason to not have one was that it was a piece of small, expensive equipment that one didn't want the shmucks going through the FJC to lose or drop on concrete. Once the masses were thinned out, with some becoming more serious students, then give them one. I wonder if IAD / S/L FJC teaching has changed at all with the new rule - traditionally no altitudes were mentioned. Now it becomes a little more complex, but one can be more specific about when not to cutaway, to avoid those dangerous low cutaways.