pchapman

So what exactly is or should be taught to newer skydivers about dealing with partial collapses? Countersteer to maintain heading (as much as possible without bringing the good side close to a stall), while doing a long stroke pumps of the brake on the collapsed side?? I didn't see anything about it in a quick search of the US SIM.

Yeah, basically mid afternoon onwards it was hectic, was a Santa Claus jump for the local kids, then a pre-planned 2 plane formation for a jumper doing his 500th (which got up just at sunset), and then everyone was trying to get the hell out of there to prepare for the annual x-mas dinner / presentations / party. There was more time to talk Sunday, given that it was solid cloud and hop and pops only... If you aren't totally lured by the turbines at Burnaby and Dunnville, do call the DZ back during the week to talk instead of waiting for spring. Those other two DZs are rather close together, but at least if someone doesen't like the atmosphere or needs a change of pace at one place they can go to the other for a while!

My normal minimum exit altitude: 1800', whether with a fast or slow canopy (Cypres off for the snivelly ones). While it is fun to joke about the AFF/PFF grads who won't exit or pull lower (even if 'legal'), let's face it, many people will want to approach anything new in skydiving with a little caution and without being highly uncomfortable. Nothing says you have to jump if you personally don't like the weather. That being said, many consider it good to be comfortable with getting out lower. I'd suggest doing things like: a) Throw oneself out of the plane a few times at a still comfortable altitude and hopefully find that it doesn't take very long to confirm that one is stable to pull, or that even with just throwing oneself out, it doesn't take long to get stable, belly to the wind, before the pull. b) Work one's way down in exit altitude when one has the chance, until comfortable down to say 2500'. c) Run the freefall numbers to remind oneself how little altitude is lost in the first few seconds (eg, CSPA charts show only 138 ft in 3 sec.) Here's my experience from another Ontario Cessna DZ which you can compare your experience to. Two weekends back a small bunch of us did hop and pops all day from 2000'-2200'. The group included those with fast, snivelly canopies. (Extra airspeed on exit helps a lot.) I figure that (excluding very low experience jumpers), the most conservative bunch of jumpers at the DZ would prefer no less than 3000', and might choose not go up unless they were sure of 2500'. Nobody bugs them for preferring a little more margin. But most experienced jumpers at the DZ will jump from 2200' (the CSPA limit) if that's where they are at and can't go higher. I think only half would choose to keep going up in those conditions (assuming they didn't just want to wait for a better day). There are things one will do occasionally but not make a habit of. Very occasionally over the years a load might jump from 1800' if that's all they got, but jumping would then stop. Anything lower would be regarded by all on the DZ as silly and wouldn't be condoned. Maybe good for bragging and campfire tales (like the couple long-delay wingsuit jumps from 2000' that one weekend) but not part of regular relatively low risk skydiving. Edit: I'm hoping we can keep this thread pretty much focused on the limits for "regular jumping", not 'crazy jump tales', BASE canopies, etc.

Nice to hear about the German reserve, of which little is heard on the left side of the Atlantic. Nice idea having the removable pull-down apex line for different inflation speeds. By "diaper", do you actually mean a diaper in the sense usually used for parachuting in the English language, where it wraps around the bottom of the canopy only? Then how is the canopy thrown out, and what is the handle attached to? Or is it (more likely) a "diaper" in the style of a hang gliding or paragliding emergency chute? In that case, is the "diaper" a bag or a 4-flap diaper? The paragliding reserves I'm familiar with tend to use a deployment bag. For paragliding, in English, the "diaper" term is only used for the four flap devices, where the flaps wrap around the canopy from four sides and closes at one point in the middle. Like the bags that have just one flap, the diaper is freebagged, and has the deployment handle directly attached to it. Diapers seem to be rare now in paragliding, but perhaps they are still used in hang gliding more often. Using a bag or diaper gets away from the awkwardness of the old skydiving bellymounts, where if there was no pilotchute, one had to gather up the folds of the canopy in two hands before tossing it away. I'm just trying to work out the technical details given different uses of words in different languages, and in different sports within a given language.

And I was shocked to see 3000 ft for US A licenses - bizarrely high! OK, I understand the ideas behind it, but it must be a relatively recent change? Through the 1990s in the USA it was 3000 student (or 3000/2800 for freefall vs static line), 2500 A & B, 2000 C & D. So historically, the Canadian heights weren't that much different from those in the US. Edit: The "fine print" in Canada is that listed altitudes are "at which the main parachute must be activated", which is a little different than the "container open" altitude someone mentioned for the US, although usually those fine distinctions are ignored.

Wasn't it BJ Worth who kept on getting work for setting up the skydiving stunts in a lot of Bond movies? Guess he was out of work on this movie. Not that I mind the direction the movie has taken; no need to automatically have a skydiving stunt each time.

Re: Source of Cl and Cd. Looks like Yuri started with curves like on the aerodynamics web page he linked to in his original post. The numbers are not based directly on wingsuits, but just on a standard airfoil. Yet they are a starting point if one can't find better data. Cd seems taken pretty much directly from the wind tunnel results for a NACA 0015 airfoil, a pretty basic symmetrical airfoil. Cl is shaped like that for the 0015, but peak values are lower, perhaps simply adjusted to avoid being too optimistic, to reduce the max lift to drag ratio to some assumed best value, like the 2.8 in his graphs. Not sure exactly how the heights of the two peaks were chosen relative to each other. I personally have not convinced myself just what the lift slope should look like. On the one hand there are airfoils with a clear pre-stall lift peak. On the other hand, a wingsuit is a very low aspect ratio device, despite the distinct wings outboard of the body, so one might use as a model some delta or blunt flat plate that has a more continuously increasing lift curve, without the "real airplane wing" pre-stall lift peak. One has to dig to find aerodynamic tests on anything even vaguely close to a wingsuit in shape.

YuriBase's posts get a little intimidating and occasionally overenthusiastic on the mathematics. But be that as it may, Yuri's math here looks right. I especially liked the convenient analytical solution to Vx and Vy which didn't require sine's and cos's (which I went through to confirm the numbers -- looks like it's all set up for sea level, 80kg as the assumptions). Where did you get those equations, or did you derive them, Yuri? The shape of the curves depend heavily on the inputs for lift and drag curves. Without debating exactly what they should look like for a wingsuited jumper, they look reasonable as a starting point -- based on the tested characteristics of a simple airfoil, with L/D kept down to an assumed maximum. In the example given, Yuri allows a good low angle of attack lift coefficient (like a 'real wing' pre-stall) that creates a big lump in the L/D curve, which in turns creates the big squiggles in some of the other graphs -- So that at the same body angle one might be in flight at either high or low glide ratio. If one has a much smoother L/D curve, perhaps for a person tracking without a wingsuit, one doesn't get those effects. (I once did similar graphs, for that situation.) As Yuri says, this all assumes that a jumper can trim at any angle of attack, with a zero pitching moment. Without that assumption, it just means that they might have to 'skip' certain areas on the graph because they can't consistently hold a certain angle of attack, at least with whatever body shape gives the assumed lift & drag curves.

To put it all another way, you are pointing out how it is easy to confuse pitch angle with angle of attack. It is difficult (particularly for the novice) to have a feeling for the angle of attack of the relative wind, so we naturally tend to use our pitch angle relative to the horizon as a reference, without always realizing what the AoA is. A "good body angle" isn't useful if it isn't matched to an appropriate glide path. All this can indeed be an issue after turns, where (without experience) one tends to forget one doesn't automatically and instantly fly fast in the direction one points. Even if one has the ability to yaw 180 degrees in an instant, that won't necessarily change one's velocity vector at all.

At the DZ I instruct at, students either progress through a traditional static line program, or the less common tandem program. I've never felt the tandem program at our particular DZ to be that successful in terms of value for money, so I am interested in this thread. At the DZ, I think the instruction for the tandem program could be improved, to make sure the high dollar jumps (compared to a static line jump) aren't wasted. Tandem instructors earn normal tandem pay when taking a student through subsequent tandems. Even for decent instructors this is poor incentive, compared to taking up some other plain tandem student. (Is this normal?) Instructors probably aren't particularly comfortable with the whole progression program, simply because any given instructor only deals with such jumps very infrequently. Currently the tandem program begins with a standard first tandem jump. (Although more can be taught if one knows the student will continue.) Jump #2 introduces figure eight turns, plus of course "a bit of everything" from gear check through landing. Jump #3 is the clearance jump with the student leading the whole jump. Assuming the student has performed well, especially when it comes to altitude awareness and pulling, then the student takes the static line ground school course (at no cost), does one static line training ripcord pull for that first solo jump, and then feeds into the normal static line progression starting with a 15 second delay. (This is in Canada. This is an unusual system, as the DZ has never had any PFF / AFF style program for the students to feed into.) For years we used to have another jump in the sequence that came before the current clearance jump, where the student would do a roll to the left and to the right, with a little instructor assistance, before the drogue was out. The intent was to make the student comfortable with unusual attitude recovery. Although it must have helped in that way, in the end I think it was deleted as not being a good enough simulation of going unstable while solo, as well as there being the issue of picking up a lot of speed if the exercise took a while.

I haven't dealt with this recently so it I can't guarantee every detail is right. The main obstacle is the location, which falls under the "built up area or open air assembly of persons" rule. Such locations require a Special Flight Operations Certificate. (See Canadian Air Regs part 623) That means having a Canadian EJR or the US PRO rating. In additions to the landowner's permission, one would need that of the municipality. Plus there are other basic rules on ground crew, equipment, winds, landing area diagrams etc. All the paperwork gets faxed in to TC 2 weeks ahead of the jump for approval. If you can find someone with a farmhouse and field away from the town, then one can do without the SFOC. There can still be the problem that if two people stand outside and look up at you, that could constitute an "open air assembly of persons", depending on Transport Canada's mood. On the other hand, the rules state "into or over" such an assembly -- so as long as one can jump & land off to the side of any crowd, one may be OK. That issue is unclear to me. An SFOC would normally also be needed for jumps through airways, which tend to be everywhere anywhere remotely close to population centres. But there's a blanket exemption in place (from CAR 602.23 and 603.37). Then one doesn't have the EJR rules etc., but only needs simple things like the land owner's permission and radio contact with ATC that varies in detail with the exact class of airspace. Even where there are airways, unless there's a big airport nearby, below 2200' AGL there's typically uncontrolled airspace, and no airways or radio rules to deal with. So out in the countryside, one could just do a low jump in to a friend's place without talking to any authorities at all. Any pilot could drop you, but if there's any compensation for the pilot in any form, one needs a commercial pilot. Typically one would rent the plane & pilot from a local DZ anyway.

Has anyone looked into what degree of hazard there might be from the use of lead in rigging? Anyone care? The main concern, I would think, would be from shot bags full of lead pellets, where the rubbing pellets would release lead dust that would contaminate the rigging loft. Same applies to handling weights for weight vests & belts. I've build weights with steel shot (but bulkier & rusty) or switched to small plates of lead. Some shot bags may be plastic lined, but that tends to abrade. When rigging at home, I end up just pulling books off shelves when packing weights are needed. I try to minimize shot bag use, wash my hands, and vacuum (although I'm not sure about particulate size). While some riggers appear to use weights for better control when packing squares, in other places shot bags are only used for occasionally packing round reserves. At least the lead seals on reserves shouldn't abrade much. But then a lot of seals get tossed into the garbage instead of being taken to the hazardous waste dump. There might have been an article in Skydiving in the late 1980s on the subject of lead in rigging lofts. I haven't gotten around to looking into what current industrial practices are for the use of lead.

After seeing the interesting thread "instersting finds..." [sic] that dealt with some WWII Japanese parachute systems, I though I'd post about one I saw on TV. I was intrigued because it seemed to show hip rings well before Sandy Reid's patented Flexon design. (US patent #5277348. Rigging Innovation's site, last time I checked, incorrectly listed 5277378.) The patent makes claims to both harness articulation with metal rings at the hip, and leg straps that terminate at those rings. The patent does acknowledge previous designs where a diagonal strap goes through a ring and continues on to the chest -- which is like this Japanese harness. I get the impression that the patent ideas are sufficiently unique because a regular skydiving harness, with rings added, would be more comfortable and flexible than the older idea of continuous webbing going around the leg and up to the chest (rings or no rings). Attached is a low quality photo taken from TV, and a drawing off the web. The harnesses were worn by Imperial Japanese Navy pilots in WWII. The photo shows a harness only, while the graphic suggests that a seat pack parachute can be clipped on. The Allies tended to have clip-on chest packs for aircrew, but seat packs were normally built-in. The British used chest mounted release boxes in WWII, but I recall that the webbing went through loops of webbing (not rings) at the hips.

Leroy -- I did forward the photos to her - I think the web versions are fine - thanks.

Interesting! (I didn't see that post when searching before making my post, and still can't find it.) The ring stamps were the same on the bent 2002 rig as and on a similar 2001 rig that was also jumped by heavy guys, but which has apparently undistorted rings. I haven't yet compared to newer rigs. I'll post again down the road whenever I find out what the factory tells the owner.

A jumper at my DZ discovered that the hip rings on his Wings container were starting to get quite distorted, bent into an oval shape. The rings have the Wichard stamp and are also marked 316L (which sounds like the grade of steel). I've seen the same markings on other Wings hip rings. I think there's no part number to distinguish it from other rings. Since the bend had become quite sharp on one ring, the rig was taken out of service and is being sent to the manufacturer. It's a rig from 2002, and both the original and current owner are in the 230-240 lb range. Nobody noticed the problem -- neither the owners, other jumpers, or riggers including myself -- because the bending process was so slow and gradual over the years. Only now is there a sharp bend in one ring, and the two rings are clearly different. Given all the variations there are in hip ring joint constructions, everyone just thought that that production run or model year had been built with oval forged rings. It's easy to see when something that's supposed to be round is oval, but it's harder to notice that something oval is a little more oval that it was 6 months ago. This is the kind of error that can slip through an inspection, where the manufacturer's intent is not known. That's a whole topic in itself.

It was odd to look at leroydb's photos as I realized the woman in the reflection is a friend. You never know when you might end up in someone's photo from some unexpected angle at an unexpected time...

I don't know what the answer should be to this question, but it may be useful to compare to other aviation activities, which happen to be heavily regulated: In the US I believe one can get one's private pilot license for powered aircraft at 17, while one can fly solo as a student at 16. (In Canada, the student certificate can be had as early as 14.)

At what level of wetness should a BASE rig not be jumped? We know that wet canopies are jumped regularly at Bridge Day, for example, and other threads have discussed opening characteristics for damp vs. dry canopies. But where is the point at which it is best not to jump a dripping wet rig? I'm asking as I'm not an experienced BASE jumper, and a couple friends at Bridge Day this year were not permitted to make second jumps because their rigs were "too wet". They had made their first BASE jumps there with gear rented from one of the major BASE companies, landed in the water near the shore, and had the rigs repacked by an experienced BASE jumper. At the gear check on the bridge, a staff member questioned the wetness, and called over a second staff member for another opinion. The jumpers were asked / told to not jump the rigs, so they stood down for the day. I wonder if it was more the container or the canopy that was retaining excess water. A container could be wrung out a little, so to speak, but with a canopy, I'm not sure what is practical other than laying it out to dry for a while. Certainly some people at Bridge Day had their canopies spread out next to the packing area to dry, but I don't know if they were 'done for the day' or not.

Pilot: Will H. from southern Ontario Suit: all white Prodigy Leisure Sports Photography's pics of his landing in the top row of photos at: [Edit: full URL deleted - doesn't work if not already viewing the site.] See www.leisuresportsphoto.com - the people who do the Bridge Day photos every year - in the 9 to 10 am landings section, page 5 of 7.

Hope the shirts are the version without the extra joke printing on the back -- that kept me from buying one the last time I saw the shirts. In 2003 someone (Lonnie?) organized all the Canadians they could find at Bridge Day and got a photo of about 30 of them... almost all clothed in the Canadian BASE shirts.

Skydivingmovies.com didn't seem to have any videos of Para Commanders... so I added one. On the weekend a friend and I did a CRW 2-stack with a square and my Para Commander. He had done such stacks many years ago. The docking speed was of course a source of nervous anticipation! The attached pic shows the hit, when I'm hidden in/under the square, and the square's tips have swung forward. The square then went back to flying normally, although slightly bent, and flown in maybe 2/3 brakes. We didn't try to land the stack. Round-square dock 2006: http://www.skydivingmovies.com/ver2/pafiledb.php?action=file&id=4976

Yup. The DZ I'm at has a couple of its static line student rigs still with FTS or APS reserves. The canopies do look very weird and lightweight with no diagonal tapes on the ribs, although to compensate, the longitudinal bottom seams at the line attachments are heavily reinforced.

The DZ I'm at (with Cessnas and 7 Sigma rigs) seems to do just fine with coveralls for students, available in various sizes, somewhat colour coded by size. No cuffs at the bottom of the legs, so they're easy to slip on. (Perhaps the most popular is the orange one with "D.O.C. Transport" on the back.) Whether good or bad, we've never worried about the extra 'control power' students might have with something other than a tight jump suit. That being said, we always want to pick a suit that's not excessively baggy. We happen to also have a few old RW style suits for small women, that are tight enough to help keep the speed up a little when there's a videographer.

Yeah, fun idea. Perhaps something like the airbags used to drop landers on Mars. However, the numbers tend to get a little awkward. If I got the numbers right, from 120 mph that'll take a 24 ft thick airbag if one wants a 'comfortable' landing at 20g's. (Assuming constant deceleration, ignoring rate of onset issues, etc.) That 20 g's is the range of ejection seat accelerations, although it would be easier on the body when flat and not sitting. If one dials up the deceleration towards the limits of human tolerance without major injury (usually), lets say 50 g, one could get away with an only 9 1/2 foot thick airbag. So it may be easier to build a giant airbag on the ground than to encapsulate the jumper in a personal inflatable airbag. If I were the engineer tasked with coming up with the design of that personal airbag, I'd probably think, hey, wouldn't it be a lot lighter and simpler just to just give this guy a parachute instead?