pchapman

Technically it does say "wind drift indicator or rate one turn". (Canadian PIM 1, Sec. 3.3. No change for many years.) So drop zones have an alternative to a WDI. But when I go to a Canadian DZ flying a Twin Otter or King Air, I don't seem to recall seeing either... :) At the DZ I jump most at, we still use WDI's. A bit of a bother but they are very good at showing the winds!

Nope no video. As it is hard to come up with ways for the rings to flip through during freefall or opening (or even, say, while hooking up in the aircraft), it comes back to the question whether I got in the airplane with the flip through. I can't avoid that question but I just can't see myself having missed that during inspection & gear up. I still need to talk to the other tandem instructor on the C-182 and to find the records of who packed the rig. And I'll play around with tandem 3-rings next time I'm at the DZ.

This weekend as an instructor on a tandem jump at near maximum allowed weight, I discovered one riser's 3-ring to be partially 'flipped through' after opening, where the middle ring had slid back part way through the large ring, and the middle ring was angled well forwards rather than vertically, as was the bottom of the riser itself. This configuration greatly reduces the lever effect of the 3-ring system. The yellow cable was jammed up against the AMP fitting and riser, with a slight bend in the cable, although not actually being sucked through the grommet. Under canopy, the top of the small ring can normally be moved with only a couple pounds of pressure (showing how little force there is on the white loop), but this time I found I couldn't budge the small ring while squeezing the riser and small ring with one hand. I landed OK with my first jump student. The middle ring shows distinct indentations where it was 'hammered' by the large and small rings during opening. The indentations are much deeper and sharper edged than the minor flat spots that occur on the middle ring over the course of many jumps. I think the middle ring is slightly distorted (bent, not ovalled), but it's hard to tell by eye. The cutaway cable is nicked and kinked slightly. A couple questions: a) Anyone know of similar incidents? I haven't found anything quite like it in the dropzone.com archives, although it has been mentioned that jumping with a flip through could or has broken risers due to the non-normal forces on the system. b) What to do with the riser? Given that the white loop for the 3-ring APPEARS undamaged, does that mean that it IS undamaged or not? One theory is that if no torn strands are seen, and no elongation is seen compared to another loop, then there is no loss of strength. (I don't know anything about stress, strain, yield strengths, etc. in woven fabric material.) At the DZ, we've grounded the rig for the moment, and we'll talk with RWS after the weekend. ========== Other details: It was a tandem jump on an RWS Sigma rig with a Sigma 395 canopy. The student weighed 280 lbs (at least as reported by the student), with an instructor weight of 150 lb. With the rig weighing about 50 lbs, that's a total of 480+ lbs, getting close to the Sigma certification weight of 500 lbs. (No I didn't check what the canopy weight limits would be after density altitude corrections are taken into effect -- PD-designed canopies tend to have that kind of thing listed, although at the moment I don't have info on paper about whether that is applied to Sigma canopy for recommended or certificated weights. We were close to the limits in any case.) Droguefall was normal but fast as expected. (125mph SAS average on the ProTrack). The opening was hard but not unusually so. Openings on the Sigmas are noticeably harder as the passenger weights increase. In particular, there tends to be a harder jolt and shake at the end of the opening, which is what occurred. The opening was on-heading as usual. After popping toggles, checking airspace, getting my passenger comfortable, etc., I checked the 3-rings. To check them after opening was taught when taking the tandem instructor course 3 years ago, although it is easy to get casual about it because one expects the 3-rings to be fine. As I didn't check right away after opening, we were getting down a bit in altitude by the time I thought through the situation, although still above recommended tandem emergency procedure altitude. It seemed most likely that if the riser and loop withstood the opening, it would be fine under canopy. So I chose to land the canopy. Still, there was the disquieting notion that there might be a not insignificant chance that the loop could let go from damage during opening, which can lead to not being alive. No spirals for the student! (I coached the student through the steering during some of the flight while I squeezed the top of the small ring towards the riser with one hand -- that seemed worth trying even though the forces on the top of the small ring were probably so high that one couldn't keep the 3-ring from releasing.) How did the flip through happen? Flip throughs on tandem rigs do occur on the ground from time to time and have to be fixed during packing. I can't imagine that there had been a flip through that remained undetected by the packer or the instructor (me). Is there anything packing-related that might make a flip through more likely? Say, if a riser were a little loose over the shoulder (rather than snugly pulled down towards the main container & putting slight tension on the 3-ring assembly)? Could the flip through have happened in the somewhat jerky opening? Perhaps one riser rotated away from the pack, yet unloaded for a moment, allowing the middle ring to slip 'back' through the harness ring? Would the unloading happen as the main bag lifted and lines stretched, with some whipping back and forth of the risers, or later during some part of an asymmetrical canopy opening? I'm not quite sure.

After deciding to post an ad, it would be useful to have a confirmation page that shows the final ad, before the posting occurs. This can be done with posting to the Forums and is a very helpful last check to see that all is alright, including the visual formatting. Lack of the feature really messed me up -- I saw an error after seeing what I figured was the preview of my ad, used the back button on the browser, fixed the ad, and posted. But as I hadn't seen a preview but the actual ad, then I had 2 nearly identical ads posted. When I tried to erase the first incorrect ad, it was impossible: It will stay posted, and show as "SOLD" for 3 days. I got myself into a bit of a mess!

If one does loose a freebag, be careful when ordering: A friend ordered a freebag from a major manufacturer, and got just that -- the freebag, without the reserve pilot chute. The order taker must have been thinking in rigging terms, not in real life skydiving terms, and didn't help the customer get what they really wanted! (The freebag bridle normally is attached to the PC with a lark's head knot.)

Yeah, I realized the problem with the FAA altitudes varying with the direction of flight. I'll accept the best answer seems to be that they started counting at 2500' and just went up from there. I had to remember skydivers didn't start out at some arbitrary 'top floor', but worked their way up -- doing style and eventually even relative work 'way up high' at 7500'.

I'm curious: Why have jump altitudes historically been at "500's" instead of full thousands of feet? I'm guessing it followed the VFR cruising altitude regulations in the USA, where VFR aircraft cruise at the 500's and IFR cruise at the full thousands?

Dealing with the Cypres valuation issue only: The Aussies have their own currency, funnily enough. I can't vouch for the Aus $490 claim, but to the US $160 one has to add a US $80 battery pack and shipping both ways.

For Canada, the NavCan AWWS site (suggested by Bob.Dino) suggests one go to the Meteorological Service of Canada for historical data. e.g., http://www.climate.weatheroffice.ec.gc.ca/Welcome_e.html I've used it only a bit. It seems that only surface data is available for their reporting stations, but it does include hourly values. For temps in the atmosphere, who knows -- even the normal NavCan forecasts are for 3k, 6k, 9k, etc. feet ASL -- less detailed than what you are ideally looking for. Its always easier to get forecasts than historical data for weather. The best I can think of, is if one is doing something like reducing flight test data and need temps, make sure to get the forecast temps by calling Flight Service and then check the aircraft OAT gauge before exit...

The first two replies to this post are insufficient to make a decision. I can clarify something about the point the original author is trying to make, and to note a possible source of confusion, but I can't provide a definitive answer. The original author must be referring to the rule that one must not descend below the elevation of the takeoff or landing airfields, as stated in the Cypres 1 & 2 User's Guides. The manual doesn't state what to do if the aircraft does go lower. All I remember hearing is that the Cypres may recalibrate, believing that the ground level is at -75 ft in this case. What to do? One can't know what the Cypres is thinking, whether the short time "below zero feet" was sufficient for it to recalibrate or not! None of the options are perfect: - turn off Cypres - accept a possibly 75 ft lower Cypres activation altitude - fly at almost ground level, and when the Suunto or other precision altimeter shows a steady nearly zero feet, turn the Cypres off and on to recalibrate it at that level. I bet few would want to try this, and anyway the manual says not to turn on the Cypres inside a flying aircraft. There's also some confusion in Cypres documentation about the descending-below-takeoff rule vs. the 1500 ft arming rule. The text in Cypres documents say to avoid descending below takeoff or landing elevations. (Eg, Cypres 1 User's Manual section 7, Cypres 2 User's Manual section 8, Jump Pilot brochure on Airtec web site.) (There's actually more detail than that -- It gets messier if one deals with different takeoff and landing elevations. Some of the statements made by Airtec is slightly contradictory if applying formal logic, but are still understandable in real terms.) The diagrams that accompany the text differ slightly. The Cypres 1 manual does not show 1500 ft anywhere, but the Cypres 2 manual and Jump Pilot brochure do: The prohibited flight profiles includes a climb to 1500 feet before making dips down below different possible landing elevations. That makes it confusing: Is it only prohibited to descend below takeoff & landing if one has already gone past 1500 ft to arm the Cypres? If so, the diagram contradicts the text. I'd like to hear an explanation of this. But without further information, I'll assume that the both the texts' and diagrams' prohibitions apply. Therefore I bet the broader prohibition of the text does apply -- The prohibition on descending below takeoff & landing applies whether or not one has already crossed the 1500 ft mark. Has Airtec or SSK been asked about all this? While the manual does mention the special case of pressurized aircaft, I've never heard of this large helicopter pressure issue before.

Just for fun, here are web pages that have lists of "saves", where a rigger or loft lists their reserve pack jobs that got used. Any others out there? Other riggers mention their total of saves but haven't spent the time to put them all online. http://www.chutingstar.com/saves.php http://www.parachuteriggers.com/saves.htm http://web.ionsys.com/~pchapman/saves.htm (That's my own modest list.) http://keats.admin.virginia.edu/deanrigging/rigging_saves.htm Similar but not quite in the same category are a number of save stories from users of Precision reserves: http://www.precision.aero/saves.htm Then there's the big list that Airtec keeps on Cypres saves: http://www.cypres-usa.com/saves05b.pdf

The last 3 rigs I've only paid between $400-$600 total for the container and the reserve. They're older, they're not super freefly-friendly, but they work great for CRW. I agree with Wendy that extra rigs aren't necessarily all shiny new and expensive. I'm one of those jumpers with a decent 'fast rig' with a Cypres 2 plus a couple older rigs for CRW / wingsuit / accuracy / back to back loads, etc. Being a rigger helps to maintain & assemble all of this stuff. None of my rigs ended up costing more than the new Cypres 2 alone!

80-85 mph SAS sustained (15+ sec), in a tight, no-bootie RW suit while doing a solo tracking dive. See attached ProTrack graph. The ProTrack display showed 78 mph average, but I don't fully trust that. It's surprising how slow one can get. And this is from someone who does only the very occasional tracking dive and has under 20 wingsuit jumps. It does help a little that I'm thin - 6'1" and 150 lbs. (The ProTrack graph shows a faster dive at the start - I was experimenting with pitch angles. I get the impression that the peak at the end is a common ProTrack artifact at pulltime. As for the dip to 60 mph, it may also partially be an artifact, but might relate to flaring out before the pull.)

Yes indeed, old Cypres batteries are great in C cell flashlights. C-cell flashlights are hard to find these days, at least in my area. Do check the voltage to find higher voltage bulbs. I measured a couple expired Cypres batteries at 3.6V per cell. In a 2 C-cell flashlight, I've used bulbs that are for normal 4 cell flashlights (rated 6.15V), which make for a very strong flashlight. However, since 2 * 3.6V = 7.2V, a bulb for 5 cell flashlights would probably be better for bulb life.

I am kind of talking to myself in this thread, but I know a few people interested in these kinds of messy details. I received a PM from Klaus (vidiot) who describes his experiences with the Paralog software he developed: (and didn't mind having this posted)

The source of the error has been explained to me by a jumper who PM'd me. (She can speak up if she wishes.) As suspected, there turns out there is averaging applied to the speed that the Protrack outputs. If one calculates speed from the altitude output (which is every quarter second for the Protrack), the speed bounces up and down rapidly, while the Protrack's output shows a smoother speed. How large are the fluctuations? In the data collected each quarter second, the speed calculated from the recorded altitude often varies by 10 to 20 mph between each data point. A spreadsheet provided to me shows that the Protrack's speed output exactly matches that calculated by averaging the previous 6 seconds of speeds (the ones calculated for every quarter second of data). I have confirmed the same with my data. Technically, "averaging the last 6 seconds of speed" is exactly the same as "calculating the speed based on the altitude change from 6 seconds ago to now". I'm guessing that it is the latter that Protrack does, as it is easier computationally. (The exact match assumes using a simple "distance = speed times time" calculation, not a trapezoidal Simpson's rule etc.) The benefit of averaging is a smoother, more easily interpreted speed graph in JumpTrack, that removes some of the error created by rapidly fluctuating airflow around the instrument. The disadvantage is that rapid changes in the skydivers actual speed will create errors in the output. By averaging the previous 6 seconds of speed data, there is a significant lag in the output speed, compared to the real speed. That created the discrepancy or error asked about when this thread was started. On my jump, when slowing down rapidly from head down to flat, the speeds reported were too high. Very roughly, the speed data was "about 3 seconds old". That accounts for the output TAS values implying (through integration) a greater distance travelled (1425 ft) than the Protrack altitude records showed (1012 ft). If one makes the same calculations, using the speed from 3 seconds before the moment being calculated, then the speeds imply a distance of 1122 ft, much closer to the 1012 ft the Protrack recorded. The averaging used also explains one reason why Protrack output is not shown for some seconds after the calculated time of exit. CHOICE OF AVERAGING The averaging method used by the Protrack is very simple, but may be appropriate given the cost vs. technology tradeoffs that are necessary. One possible improvement would be to average the speed over 6 seconds, centered on the present time, i.e., 3 seconds into the past and 3 seconds into the future. Such averaging would remove the "lag" in the speed, but would introduce some "anticipation". For example, if a jumper were bellyflying and then suddenly sped up in a stand, the speed record would show a slight rise prior to the time where the jumper went into a stand. The challenge is to find a smoothing scheme that dampens out sudden pressure fluctuations, but does not damp out (to too great a degree) actual changes in the skydiver's speed. I made charts showing different averaging schemes -- averaging over the past 6, 3, or 2 seconds, and averaging over 6, 3, or 2 seconds centered around the present time period. My personal preference was for one of the centered averages (to avoid lag), over 3 seconds. Using a 6 second time period just seems too long relative to the time scale of actions in a skydive. As for more sophisticated data smoothing techniques, I won't touch that now. (E.g., Fourier transforms & frequency filtering, rejection of data that implies excessive accelerations, etc.) Attached are three charts. Because of the size, I haven't attached my original Excel spreadsheet. Two charts compare the Protrack's averaged output to the raw speed data calculated from its quarter-second data. The charts also show what the curves would look life if shorter timer periods were averaged, and centered rather than using only data from the past. [Edited to add: One chart is for a jump labelled as head down, but actually included a mix of body positions. The other jump was a 16-way bellyfly formation. ] The third chart shows an idealized jump with hypothetical data, to give a clearer visual impression of some of the effects of data averaging. (It uses simple linear or instantaneous changes in speed for the most part.) It's really a bit simplistic, and not all that necessary if you are familiar with the concept. IMPLICATIONS FOR PROTRACK DATA ANALYSIS Knowing that there is this averaging over the past 6 seconds significantly changes the way we must look at ProTrack data in JumpTrack. If one really wants to interpret the data better, one needs to export the data from JumpTrack to a text file, and then import it into Excel, and write any averaging scheme one prefers. Otherwise, one needs to be aware that all speeds output are a little "out of date". Therefore when slowing down (e.g., head down to flat, or after pulling) the speeds shown for a particular time and altitude are too high. The opposite is true when speeding up (e.g., acceleration early in the jump). It is unfortunate that the manufacturer's calculation method is not mentioned in the manual (at least the one I have, to the best of my reading ability).

A couple people PM'd to ask for the original data so a spreadsheet is attached, with the JumpTrack data and my calculations. Its one thing if the Protrack can't accurately measure reality (because of the limitations of using air pressures around one's body to calculate altitude); it's another thing if the results it outputs are inconsistent within themselves. Let me know if I've made an error somewhere.

We know that a ProTrack can give erroneous results in some circumstances, because of the changing airflow it is exposed to when head mounted. I've noticed a different type of error, where the speed data does not match the altitude data, if one integrates the speed across time to give distance. I figured that ProTrack speed data (as viewed on a computer with JumpTrack) would be calculated from the ProTrack's internal time clock and the altitude it calculates from pressure data. The error is confusing because it is a mismatch between different data that the ProTrack outputs. I noticed the error on a jump where I was coming out of head down and slowing down before pulling. I looked at a 5.75 second block of data (with data shown for every 1/4 second), in which the altitude changed 1012 feet. The speed at the start was 189 mph (TAS) and 122 at the end. It's easy to see something is wrong: If we know that a jumper takes about 5.7 seconds to fall 1000 feet, at 120 mph, then how could I have taken about that much time for that much distance, when I was much faster at the beginning and only reached that sort of speed by the very end of the time interval. (Using SAS speeds doesn't change the results significantly.) Doing a rough integration of speed across time gives an altitude loss of 1400 feet or so during those 5.75 seconds, instead of the about 1000 the ProTrack showed. To make the distance work out right, my freefall speeds would have to be about 30% less (134 to 87 mph). My gut feel is that the reported speeds are indeed too high, but that doesn't explain why. I can't understand why the internal discrepancy exists. Is there something in the way that speed and altitude are calculated, and raw data is filtered?? I did email the manufacturers recently but haven't yet heard back.

My ProTrack's output (viewed on the computer with JumpTrack) always shows a big spike in speed during the tracking off from an RW jump. The spike typically goes up to 140 to 160 mph SAS. It does start at the altitude I remember as break off, and continues through the short track until the speed drops off quickly during canopy opening. The spike has also happened for a group tracking dive, after the point where we broke from the moderate speed tracking, to an agressive track before pulling. The spike is sure to be erroneous, as I don't drop away from the formation in some sort of bad, diving track. My ProTrack is mounted externally on a ProTec helmet. I don't know how an internal mount or other helmets might affect things.

An obvious correction to my own post: The new container went around the backpack and lateral webbing.

They seem to be extremely rare, and produced only on a custom basis, whatever their name may be. I saw some members of the Australian style & accuracy team at the 2003 World Championships with such add-on main containers. The new container went around the backpad and main lift webs, using large areas of velcro to stay fastened. It provided a new bottom flap (plus BOC) and side flaps. The original top flap and pin cover flap of the rig stayed in use. The original side and bottom flaps were just tucked away underneath the main d-bag as far as I could tell, but I didn't inquire about exact positioning. The add-on containers' construction looked quite professional. This arrangement allowed the jumpers to convert one rig (and one Cypres) between accuracy jumping, and style or fun jumping with smaller canopies.

This isn't a particularly important post; it's just something I'm curious about -- a question with a whole lot of opinion thrown in. While downsizing is often discussed, I can't recall hearing much about attitudes towards the role of the borrowed canopy. What are the attitudes today on lending people canopies smaller than they normally fly, whether to help them move to an even smaller canopy they bought, or just to fly for a few jumps to gain experience? BORROWED CANOPIES FOR DOWNSIZING: In some sort of ideal world we might all buy a canopy one size smaller than the old one, and jump it for a whole season before going down one more size. But in reality people don't have the money for that, and many skydivers aren't actually going to be in the sport "forever". So they want to have something small and zippy sooner than ideal. It is common for someone to buy a canopy a couple sizes smaller than they now fly (especially at the novice level), but before they fly it, they put 10 jumps on a canopy half way in between what they now fly and what they just bought. So borrowing a canopy is a great way to make a more gradual progression in canopy size without spending huge amounts of time and money buying canopies. On the other hand, it can be seen as a way to downsize too quickly. Doing 10 jumps on a borrowed canopy and being able to flare it in normal conditions, doesn't mean that the next size down is what one should be flying from then on. BORROWED CANOPIES FOR VARIETY: Canopies may also be borrowed to get experience with different styles of canopies and flight habits, to become a more well rounded and aware skydiver. "OCCASIONAL DOWNSIZING" or BORROWED CANOPIES FOR A BIT OF FUN & EXPERIENCE: One reason for borrowing smaller canopies, that I like, is to get a taste of a smaller canopy, without having to fly that canopy all the time. Jumping the smaller canopy isn't being used to downsize immediately thereafter. The jumper gets a bit of practice on the smaller canopy without having to deal with it in everyday conditions, day after day, on every jump. The canopy may be more likely to be treated with extra respect, to be flown carefully, with less aggressive landing approaches. Sometimes it seems that the first jumps on a canopy are safer than the later ones, when the jumper agressively starts to "try stuff" or assumes they have the canopy mastered. There is still the caveat that the jumper should best be able to handle their larger canopy proficiently first -- all the stuff about emergency flare turns etc. Using a smaller canopy may increase the risk per jump for the skydiver, but if they only borrow the smaller canopy a few times, the per-year risk is still much lower than if they bought that canopy. (The per-year risk issue is interesting: If an experienced jumper chastises a newbie that the newbie is 10 times more likely to hurt themselves on any given landing, the newbie might be able to claim, "Okay, you do 200 swoops a year, I do 20. So our risk is the same. If I start jumping a lot more, then I'll make changes.") So to me it feels like borrowing smaller canopies is a way to get a little extra excitement and challenge, and learn some skills on the smaller canopy, without giving up one's everyday bigger canopy. Jumping a smaller canopy a few times may give a jumper more respect for the canopy, some actual experience as to why not to buy such a canopy, rather than simply having to listen to the skygods tell him he's not ready. (Although the emergency flare turn etc. flight drills are a good way of giving the jumper some of that experience too.) On the other hand, jumping a canopy a few times may make the jumper want it even more. Is it sometimes seen as too much of a risk to let people do occasional, temporary downsizing, before they are good and ready? Or is it still an acceptable practice? Rigid regulations on canopy wingload and downsizing would reduce the frequency of occasional downsizing. My bias is having downsized in the old days, early 1990s, where there was little downsize progression theory. While I only owned a big F-111 accuracy canopy, I borrowed small stuff from friends from time to time. So I got to fly a Jonathon 92 at 1.85 wing loading, when I had 200 jumps, on a low wind day. My downsize experience was that I had done 3 or 4 jumps on each of a 160 ZP, 135 Sabre, 120 Sabre, and 120 Stiletto & Jedei. There seemed to be no general feeling in those days that the person who lent the 92 to me had done anything wrong. If they wanted to risk grass stains on the rig, fine. In any case, I do like that nowadays there is much more emphasis on actually teaching people how to fly smaller canopies well.

What was it about the design of the different sleeves that affected opening shock so much?

While it is important to get the manuals, it also helps to find out what experienced people are doing in the field. Sometimes its hard to tell whether what's in the manual is Correct, Good, Normal, or not. My justification to say the above: When my local DZ bought Sigma tandems in '02 (after having used Strongs), we started out learning to pack according to the manual. When a very experienced instructor arrived to teach the tandem instructors course, he kept on saying about the pack jobs, "you don't need to do it that special way -- just do it the regular way" or "we now do it this way instead". Tandem exits also vary between the manual and actual practice, due to the age of some of the manual's contents. The Vector tandem manual that came with the Sigmas showed one type of exit that I gather most in the industry has stayed well away from for many years. (Poised, facing forward, all the way out on the step of a C-182 etc.) Even with reserve packing opinions differ -- I've always packed the PD reserves in the Sigmas in the special way they show in the manuals. But last year we bought another Sigma, and its reserve pack job from the factory was done in a very different manner. Interesting!

[...] Is that Scott and Meriah(sp?)? Yes that was them!