pchapman

I'm not sure how intelligent all of these questions are, but it is true that many questions are quite reasonable for people who don't know the sport, even if the questions still sound funny to us. It's the questions that show a total lack of understanding of physics (and not just skydiving) that sound the most stupid. One whuffo's intelligent comment after watching people land: "It's weird... the jumpers who look the most out of control ... the ones dropping & spinning out of the sky... they have the best landings." (It's not true all the time but she had a point!)

As for Burnaby Ontario this weekend, high winds kept us grounded until late in the day Saturday, after which we got 2 Otter loads. Few people were still around for RW, but Jeff Gemmell still enthusiastically organized dives for those of us left: Two 3-way dives! I don't know how things are turning out today, Sunday, but both actual and forecast conditions were bad so I left the DZ after a few hours. Forecast was for 60 knots and -11 C at 12000 MSL...

There's a well known Parachute Recovery Systems Design Guide available that's written by Theo Knacke, dated 1992. (It's a 512 page manual mainly on round parachute design largely for military purposes, full of detailed engineering.) I noticed that online at Irvin's web site, there is a 42 MB pdf file of the 1978 "Recovery Systems Design Manual" AFFDL-TR-78-151 by 3 authors including Knacke, that is nearly 500 pages, written for the US Air Force etc. I don't know to what degree the two are similar, as I don't have the 1992 book, and only just spotted & downloaded the 1978 document. Anyone know? Is the 1992 book done from scratch by Knacke based on what he learned during his long career? Or it is "just" an big update of the 1978 work that he was a main author on? The table of contents for the two don't look like a close match. In any case, it looks like if one has a passing interest in the subject matter, the 1978 document would be interesting to download. The 1992 book is likely a 'must have' for people in the industry, but it would be overkill for those with just a minor engineering interest in the aerodynamics etc. of parachutes.

The Partenavia breakup is a well known one among airshow accidents. As I heard it, the pilot's wife was doing the narration for the crowd. For the average pilot, yes. Yet a non-aerobatic aircraft can be flown fairly safely in aerobatics if carefully inspected and carefully flown by a pilot who doesn't make mistakes and knows energy management in order to keep the g's low. The classic example is Bob Hoover with his Shrike Commander, a plane roughly comparible to the Partenavia. He'd fly part of his airshow with one prop feathered, and then both feathered. (Seen the video where he pours himself a glass of tea while flying a barrel roll? Theres's a link at the bottom of http://en.wikipedia.org/wiki/Bob_Hoover)

Haven't seen it. I think that was the other RW book available at the time. I picked one of the two available books off the mail order lists...

Just curious whether anyone had found the book of use, or whether it was once popular, way back when. The book was published in '81 as a guide to RW, and I bought the 2nd edition in about '90 when I got my licence. I was trying to find some source of information on RW and that's what was available to buy. I found the book quite confusing, partially because I had so little RW experience that I couldn't truly understand its lessons in terms of real experience. A lot of the book dealt with the dive down to a formation and how to approach a formation. The other problem for me was that I was trained in aerodynamics, while the book had many incorrect statements about physics & aerodynamics. While it doesn't take an aerodynamicist to do good RW, it did take away from the perceived authority of the book.

As a general comment (even if the original poster knows this well): As far as I know 8015 is the property of the SAE and is available from them only by purchasing it. But I sure like to be able to know the standards by which my equipment may be certified. Also useful for those interested in certification, is to check out PIA's proposed TS-135 available from their web site.

There might be one more failure mode too, where the canopy starts to dump out one of the lower corners of the freebag, before the safety stow releases or all lines are paid out. This would result from freebag that is fairly open in the corners, and an old or weak safety stow stretching a lot, and maybe some sort of asymmetry in the deployment process. I believe this is something Jump Shack recently claimed in one of the threads about damaged reserves, but I don't recall exactly where. The point was that the safety stow didn't have to break for the canopy to get dumped. I don't know how likely this really is, but the idea should be part of the whole argument.

Since reserve snags are a popular item in this thread at the moment, I'll add a minor story: A girl at the DZ, with maybe a hundred jumps or so, was jumping her first rig, a well used one with a round reserve. It wasn't quite the old days, more like 1991, so there still were plenty of used rigs with round reserves around. The actual reserve system, however, was from the old days -- a diaper-less round with the lines stowed in the pack tray. One day she mal'd, chopped, and went to the reserve. BAM!, a hard opening and a big holes in the canopy that weren't vents. One line broke and two panels were torn between reinforcing bands. She wasn't a big person and took the hard landing without real injury. What had happened? In the pack tray was one grommet with a flange bent up 90 degrees. Those old rigs weren't heavily reinforced around the 2-pin reserve closing loop, so the flexing tray allowed the edge of a grommet to stick up a bit, in the path of all those lines stowed in the pack tray on a no-diaper reserve. One line had snagged the grommet, resulting in the out of sequence deployment and luckily 'only' a broken line and a couple panels. Another time the same girl blew open the center top skin of her main from nose to tail. I was looking down at her after her opening and wondered for a moment what the wavy fabric was, but just went back to flying my own canopy. The canopy stayed inflated. (This was an F-111 7-cell, with maybe 150 lbs total on a 220 or so canopy.) After landing, she complained about the hard landing and crummy flare, and went to pack. She's yanking on the packing tabs one by one while flat packing, 1...2...3...and then #4 pulls way out from the rest of the canopy, attached to torn fabric. Only then did she realize she had had a mal. So in her few years in the sport before retiring to start a family, Sylvie had managed to blow up both a main and a reserve canopy. (While I do like the real old days stuff from the 60's and 70's in this thread, I hope there's some tolerance for newer stuff here, without getting finicky with dates! There is a "Scary Stories from Today" thread, but I haven't seen anything in between.)

The only recent North American use I've seen of the "POD" term was for a special deployment bag for a BASE system. I presume it was called a POD rather than deployment bag mainly because it was longer, about one third the length of a canopy being packed. It also happened to have a #8 grommet on top to allow the bag to slide up to the pilot chute, and used a reserve d-bag style pouch for stowing the lines. I believe the company is currently just calling it a sleeve instead. This is just a minor example of how an old term was reused for a type of deployment bag that in some ways resembled the original POD.

However, it may help jumpers that the main lift webs and chest strap aren't rigid beams, but are flexible and can in some cases move in order to better accommodate unusual loads. E.g., yanking the chest strap outwards in a 'V' shape doesn't just try to peel the strap away from the MLWs. The MLWs will twist, so that the forces along the chest strap feed (as perhaps intended) nearly straight along the plane of the MLWs. And if one has chest rings there's even more flexibility to allow good load paths. (Actually, isn't the load of someone pulling outward a little like the force of a jumper's torso pushing out on the chest strap while being pulled upright on opening, if the MLWs over the shoulder aren't taking all the load? So the pulling isn't entirely unlike something the rig might be designed for. Pulling downward along the direction of the MLW, however, is something I don't expect the chest strap to be designed for.) I wonder what rig designers actually have chest strap load information, rather than just designing by precedent, using designs at least as strong as what everyone else has done in the past! The issue of what types of loads chest straps are actually designed to handle, is unclear to me.

Some thoughts that focus more on the real world than the ideal world: -- You'll get an idea of common size ranges (relative to the main canopies) in the Classifieds anyway, if you are looking at buying used. -- Let's face it, very often the reserve size people buy is "the smallest they dare". Someone might figure that they can handle a PD143 without any real problem, and then buy a 126 (the next size down) because they really want something small on their back, and that way they should be able to handle it well enough. After all, for main canopies, if you're really comfortable with a given size, then trying out one size smaller, if one is being careful, is normally considered OK. (Although for reserves there's the added complication that they don't fly like most mains.) On the other hand, the person who thinks they'll be comfortable on a 143 may decide they'll go one step the other way, up to a 160, for that extra margin in case of a bad landing area, unconscious AAD save, injury, etc., and that the bit of additional bulk shouldn't be a problem. It all depends on one's personal philosophy. -- From the idea mentioned above, of hoping to 'be able to handle one size smaller', one can make this rule of thumb: The reserve should be no more than one size smaller than the main, for novice to intermediate jumpers. I think that may be reasonably true, but open to attack because it is so short! -- Time is a factor. A novice may plan to keep a rig for a few years, and after the first season or two downsize the main. They don't want too big and bulky a rig. So they buy a rig with a relatively small reserve that they think they'll feel comfortable with next season... despite being a little uncomfortable with it this season. It's a calculated risk that some accept. Reserve sizing ends up being part of the whole issue of long range planning of downsizing progression and how long to keep a particular rig or main canopy. -- Despite all the differences in personal preferences, what is a decent wing loading? A couple experienced people mentioned a 1:1 wing loading. That sounds quite reasonable and fits well with what manufacturers say. PD's recommended maximums: Most of the time it is 0.85 for Novice 1.0 for Intermediate 1.15 for Advanced 1.4 for Expert [Based on their weight vs. canopy chart. These numbers hold for most sizes but don't apply in some cases for very large or small canopies.] Aerodyne for their Smart recommends: 1.0 for Novice & Intermediate 1.4 for Advanced (but that seems to correspond to PD's Expert category, as Aerodyne doesn't have an Expert category.) Precision's R-Max: Couldn't find any info on their web site. There are no specific definitions of categories like Novice or Intermediate, however. (I won't get into issues concerning high wing loadings with older designs of reserves, or the desirability of lighter wing loadings for very light jumpers.) -- One answer in this thread suggested that mains should be sized to be compatible with the reserve in case of a two-out. For safety's sake, that seems true on its own. But in practice I don't see people paying attention to that factor. Or at least, other factors dominate the decision. (It can be argued that for very small main canopies, a bigger reserve is better, for the much more likely case of a plain reserve ride, compared to the rare but dangerous 2-out situation.) A lot more could be written on the reserve size subject to provide a real guide to novice jumpers.

I can't find anything to dispute that. The only thing I've ever found in the Canadian Air Regs is for demo jumps over built up areas etc. Then the reserve has to have been packed by a "certificated parachute rigger". Other than for that, a bogus reserve pack job etc. is just an internal CSPA matter. (I hope everyone still feels free to discuss the 'bogus pack job' issue as it would apply in their own country, whether that's the USA, Canada, or anywhere.)

There have been good posts about the "dealing with danger" aspect -- such as what all is covered in skydiving training, and how one is trying to act in an informed, responsible and safe manner. Another aspect is to address the "why would one want to jump out of airplanes?" issue. It can be a photogenic sport so for me it helped to show videos to friends & relatives. One could pick something well shot and edited, showing beautiful skies, people having fun in the air, nothing too extreme or filled with skydivers acting like maniacs. After seeing videos, I've had little old ladies say they now understand why I skydive.

Two weeks ago Friday I packed some tandem reserves for the DZ. Saturday morning an instructor does his tandem recurrency jump, first of the season, with an licensed jumper on front who had never done a tandem. The instructor has a problem with stuck toggles and goes to the reserve. Good practice indeed for the instructor & excitement for the passenger! Sunday evening after Easter dinner with relatives I swing by the DZ & pack the reserve up again...

I don't repack the main canopy. Why? It seems to be one reasonable way to do things, it is the way I learned it, and is the way it 'usually seems to be done around here'. The main risers are disconnected to make the reserve packing easier, to flex the risers briefly at the rings, and to clean the cables. After the reserve is done, the risers that were carefully laid aside are reconnected and the customer told to do a repack since it is considered his responsibility to confirm that the reconnection is correct. Often I close the main container with one or two flaps as a temporary measure to make the rig easy for the customer to carry off, yet still remind the customer that a repack is needed. (Some jumpers may choose to un-bag the pack job, do a line check while the canopy is still rolled, and re-bag the canopy, 'saving' part of the pack job. But that's an advanced technique done at the jumper's discretion.)

I was in contact with the rigger. He said it was the first time he assembled those type links and had a tough time getting clear info on how to do it. Only later did he see a clear picture and by then had forgotten how he'd done it. Since the Aerodyne manuals have shown a clear drawing for at least the last 2 years, he probably wasn't working off a manual. He may have had vague or misinterpreted verbal instructions. I seem to recall that Aerodyne ships gear with almost no paperwork, just a CD of manuals. This can make it a little awkward to quickly get gear assembled for someone unfamiliar with it. The lesson is a simple one about reading the effing manual if one isn't absolutely sure about something potentially critical.

Attached is a photo of how the link was found, once rotated out of the riser. It's still a bit hard to see what's happening... but of course that's the issue when inspecting. The other attachment is the drawing from the manual for that Aerodyne soft link design.

I came across reserve soft links that weren't assembled according to the instructions. They were of the 'ring' type, like Aerodyne, Precision, and PdF use. (Not the PD tabbed Slink type.) The links had the end of the line simply lark's headed around the ring. The line did not first pass through the loop at the other end of the line and then pass over the ring. It looks 'fairly' safe and secure but the load path isn't as the manufacturer intended, and the line larks headed on the smooth ring does not tend to stay cinched as tight as normal. I just want to double check that there aren't any alternative soft link assembly methods I haven't read about. Sometimes in rigging there are 'accepted' or 'approved' techniques not mentioned in the manual -- but I haven't seen that this is the case here! I changed the links back to the factory method, and it will be discussed with the rigger, who is experienced and current. Other details will not be divulged.

Gary & Brian will obviously realize that there could be problems in getting more than just a small amount of skills transfer from the 'training', to real swoops over ground. A streamer just doesn't have the same visual picture & cues as the ground has. The streamer might help more when one is working to learn swooping a particular object (like an entry gate). On the other hand, the streamer drifts with the wind, so it isn't useful in training to plan one's approach for different wind conditions. It concerns me that the descent rate of the streamer would tend to train a jumper to "aim low". A jumper just aiming straight for the top of the streamer may pass above it because it is moving down away from the aim point. Lead vs. lag pursuit curves come to mind. Not leading the streamer enough may also result in intercepts that succeed (and are successful in the jumper's mind), but only because the jumper maintained a high rate of descent without a full flare. Aiming low and maintaining a high descent rate are not good behaviours to transfer to the real ground swoop. All this reminds me of the experience some people will have in catching freebags under canopy. I've only done the airplane & toilet roll thing. In any case it sounds like fun and may provide some extra canopy skills. I look forward to reports too.

I got the impression that the life jacket exception is an exemption from the requirements of the whole paragraph. Otherwise it's not much of an exception. There would be little point in being allowed to take along emptied non-refillable cartridges (if they are indeed non-refillable). Agreed! Check ahead.

There appears to be an exemption for life jacket cartridges: "NOTE: There is a compressed gas cylinder exception for both carry-on and checked baggage that allows 2 compressed gas cylinders fitted into a self-inflating life-jacket and 2 spare cartridges with the approval of the aircraft operator." It's on the TSA page http://www.tsa.gov/public/interapp/editorial/editorial_1188.xml but unfortunately NOT in the pdf list found on the page previously posted. A similar exemption exists here in Canada.

1 reserve ride in ~1500 jumps at #608 It was a CRW wrap so when the whuffos and students ask about canopies failing, the simple answer is still that I've never had a canopy malfunction on opening.

No personal attacks allowed in the forums. (On dead people too?)

In this discussion, does 'body position' refer only to the body shape, rather than both body shape, and body angle relative to the horizon? Our jumping terminology may not be consistent on such things. If body angle were being included, then of course it is normal to start more head down and then angle less head down. If body angle were not, then the issue is more interesting. (If I'm not being clear, an example is that if someone found that 20 degrees angle of attack were ideal at every speed, and a 1:1 glide ratio were the best achievable, then the jumper would start 70 degrees head down and eventually transition to 25 degrees head down as forward speed picked up.)