mark

Looks like you're anonymous, which actually works better for my question to you: do you anticipate paying for your apprenticeship? getting paid? trading work for experience? I ask because I occasionally have requests to take on an apprentice and I'm curious what the expectations of apprentice-applicants are. Mark

Most folks agree because it seems intuitively obvious. Which two harness/container/reserve/AAD combinations would you test first, and why? Mark As we discussed earlier in the thread - I'd personally start with investigating reports from riggers who have identified tight combinations (as folks here have already said they've seen) and see if they're reproducible and then move onto quantitative drop testing for those that have questions about them. I believe BillVon suggested a different approach - only investigating those rig combinations which have been involved in suspect incidents. These are 2 possible options. There are certainly more. So far there has been exactly one rig reported by exactly one rigger, and that particular combination has not been implicated in any of the suspect incidents. Perhaps we might go with one of the rigs involved in the Z-Hills double fatality earlier this year, reported in the incident thread as What hypotheses would you test? Mark

Most folks agree because it seems intuitively obvious. Which two harness/container/reserve/AAD combinations would you test first, and why? Mark

I'll echo Terry -- any chance of a photo of the bent L-bar? Also, could you speculate on how the L-bar was loaded to make it bend? Mark

I had reverse step-ins on my Wonderhog Sprint. I liked that the pilot chute throw from the front of the leg strap was a much more natural motion than the half-twist an ROL requires. Mark

Then lay the canopy down and squash the air out of it. When you're done, the lines and nose will be in the same place as if you hadn't done that extra work. Mark

AC 105-2C and 105-2D both allow stuff to be attached to the outside of the parachute assembly as long as you take care not to impair the functional design. Mark

If it were up to you, would you do another 30 test drops to verify you'd identified and corrected the problem? Mark

That's the rub, isn't it. The 30-drop test series may be enough to identify that there is probably a problem, but may not be enough to determine exactly what the problem is nor how widespread it might be. Let's imagine I have a low reserve opening after a total malfunction on my Curv/Optimum-143/Katana-120, and that I get a similar opening in the retest series using exactly that rig. Should I test with bigger or smaller mains? It might be a problem with that particular rig. Should I test with the same canopies in another production model rig the same size? It might be a problem with that particular reserve make/model/size. Should I test with a low-bulk Icarus reserve of the same pack volume? I think my Curv reserve packs about as tightly as my Mirage. In case the problem is with the reserve canopy and not the container, should I test with the Mirage as well? Mark

Ok. Check my math, please: 30 tests have a 95% chance of detecting a problem if the underlying failure rate is at least 1 in 500. Now let's assume that we get a failure in that test series, duplicating the problem that led to the testing. What should be the course of action? Should we: -- continue to jump rigs with the same configuration until we can isolate the problem and identify a solution? -- ground other containers of the same make, model, and size and with similar-sized reserves until that combination has been adequately (whatever that is) tested? -- ground that particular reserve make, model, and size in other containers, until it has been adequately tested in other containers? -- something else? Mark

I'm looking for a statistical confidence level. 95%? 99%? Mark

I'm not against testing. I'm just trying to understand exactly what you're asking for. Let's say there is a container/reserve/main/AAD combination that has been involved in a fatality that we suspect includes a low reserve opening. How many test drops would you want to do for that combination? How sure would you like to be that your test drops would detect a problem? Would you do all the drops on the suspect rig, or would it be okay to test other rigs with the exactly the same combination of components? Mark

I'll take that as a personal attack. Mark

Several points here: 1. Yes 5% is acceptable on my end 2. I think the 3 second rule needs to hold up in at least 95 of 100 tests by the manufacturer. The same type parachute (not the exact same one) should be used in a SPC (Statistical Process Control) mode where a sampling on the finished product is pulled and then tested. 3. The same with a random rigger that packs the same: not necessarily the same factory rigger. MEL Making progress. How sure would you like to be that the actual failure rate of all the rigs with the same configuration is no more than 5%? What combinations would you test? Mirage Systems, for example, lists 42 main canopies and 9 reserve canopies for its MZS-size containers, which means about 400 different possible combinations. Mirage is okay with Cypres-1, Cypres-2, Vigil-1, Vigil-2, Argus, and MarS AADs, which means even more combinations. Plus the main container might be full or empty. How would you choose which to test, or would you want Mirage Systems to test all of them? (Not hitting on Mirage, particularly. All manufacturers would be in the same boat.) Mark

When we test parachutes or anything else, what we are doing is taking a sample. We can't be 100% certain our sample is representative of the whole; we settle for some percentage less than that, usually 95% or 99%. We are also interested in the failure rate of the population as a whole, in the case, the failure rate of a particular combination of container/reserve/main/AAD. What I think you are saying above is that you would find a failure rate of 5% to be acceptable. Is that right? If so, how sure would you like to be that the failure rate of the population as a whole is 5%? Another way: how sure would you like to be that your sample is representative? Mark

Other posters have suggested that gear be (re-)tested to be sure it works to standard. Would you be in favor of that? If so, what level of statistical certainty would be acceptable? Would you want to be say, 95% confident that a particular container/reserve/main/AAD combination failed no more than one in a thousand times? Or would you want a different confidence level (99%?) or failure rate (no more than one in 10,000?)? Mark

Me too. Although the distance along the actual trajectory has been plausibly 300 feet, especially considering the illusion caused by the airplane moving away from the release point. I don't know if any manufacturers are taking advantage of the ambiguity of "vertical." -- C23b is silent with respect to the altitude required for opening. For a total malfunction, time to impact from 500 feet is more than 3 seconds. -- C23c "high speed" tests are strength tests, not functional tests. You're right about the ambiguity of "fully open." The developers of AS8015B agree with you, which is why the term in C23d is "funcitonally open" and has a definition. Mark

What level of statistical certainty would you test to? For example, would you want to be 95% confident that the failure rate of any particular combination of container/main/reserve was less than one in a thousand? Mark

The standards have stayed essentially the same throughout TSO evolution, even as the language has gotten more exact. Short version: 3 seconds or 300 feet. For C23f: essentially the same as C23d below. For C23e: nothing was ever certified under this TSO. For C23d: manufacturers can choose either 3 seconds or 300 "vertical" feet. I think the intention of "vertical" is what we normally think of as vertical, that is, the trajectory at the end of a 10-second or longer freefall, rather than the vertical component of the trajectory of a load as it is released from an aircraft in flight. 48 drop tests are required, at a variety of airspeeds, some with the main compartment full and some with it empty (no special provision for "overstuffed" or "extremely loose"). Also for C23d: 8 drops, with a maximum of 2 seconds or 300 feet from breakaway to functionally open reserve. Also for C23d: 5 drops with deliberate line twists. Allowable opening time is 4 seconds. Finally for C23d: opening times/distances are increased for weights above 250 pounds (to allow particularly for tandem rigs). For C23c: the phrasing is not exactly the same as for C23d, but the requirements are essentially the same. For C23b: 12 drops, 170 pounds, 70 mph, opening time 3 seconds. With line twists, 4 seconds. Mark

Ha ha. _You_ don't need to sign a piece of paper, but the S&TA does. The S&TA needs to file the waiver in writing on the waiver form in the SIM, then send it to the USPA Regional Director and USPA Headquarters. (USPA SIM section 2-2, para C.) Mark

I don't think you'll find many who think 2k is a good hop-and-pop altitude. But there are many, including me, who think it can be an adequate altitude. Mark

Source? Mark

I can't recall seeing specific specs published anywhere. Many kill lines require some sewing or bartacking to replace, so it's no more trouble to make them from scratch than it is to field-install a partially fabricated one from the factory. The kill line needs to be long enough to cock the pilot chute. You'll know the pilot chute is fully cocked if the limiter/centerline tapes (the ones that run parallel to the kill line from the base of the pilot chute to the apex) take the load. Run an overlength piece of line through the bridle and finish the pilot chute end of the kill line. Cock the pilot chute, and temporarily tie the bag end of the line to the link, 1-2" (3-5cm) close to where the line emerges into the bag. Then check to see the pilot chute collapses correctly. When the pilot chute is fully collapsed and held up by its base, you should see just mesh around the edge. If there is a rim of fabric, the pilot chute is not fully collapsed and will pinwheel. This is not a safety issue, just a pain to unwind to pack. The pilot chute should not turn inside-out so completely that it stresses the stitches holding the two sides of the bridle together at the pilot chute end. If it does, lengthen the kill line slightly and try again. Once you've verified correct operation, then make the link-end knot permanent by fingertrapping and bartacking. An ugly bartack with contrasting thread will allow you to pick the stitches and lengthen the kill line if it shrinks. Mark

I sent one in on 1 July, received it back on 22 or 23 July. Subtract two days UPS shipping each way leaves about two weeks. Looks like they are back to normal schedule. Mark

Routine service takes about two weeks plus time in transit. If your Cypres has to go back to Germany, then service takes longer, although there is no extra charge. Mark