pchapman

Wasn't our whole sport pretty much created using life saving equipment the military sold off ... as no good any more? (As for the condition of gov't surplus sewing machines, I have no idea.)

Didn't we have a whole thread on this video before, for some good ol' newbie bashing? I couldn't find it with a quick look however. Edit: The jumper probably wasn't going all that fast on deployment, although a little extra speed could be a factor. A more important factor could be the body position on deployment -- with the canopy deploying perhaps to one side of the jumper's back, one riser would be pulled down more than the other, creating a non symmetrical deployment, creating higher stresses at some points than usual. Still, that alone wouldn't normally split a canopy, so a strong possibility is that it was an older canopy where the canopy strength was already lowered. Edit 2: The center back top skin of the canopy tends to be an area of heavy wear. The center cell is also the division between the left and right riser line groups. As for why the canopy split along the center, the former can be a factor, and the latter, who knows, maybe.

Is that the one also known as a parabatic leg grip? (I'm not in tune with modern CRW practices.)

Thanks for the link. There has been plenty of talk in recent years about how AAD's might be slow to allow reserves to extract -- because of possible factors like small rigs, main canopies still in the container, and long closing loops. The PIA doc shows that they have at least taken some such things into account when checking AAD & harness compatibility. They do test with, for example , 1 inch longer-than-suggested closing loops. (It might be nice to vary the canopy size in the container too, to try overstuffing or understuffing the container. That, however, would affect bag extraction and not just the pilot chute launch being tested here.) Mind you, I wonder what would happen if an AAD failed the tests -- in some such cases, all AAD's might fail with that rig. Many of the potential issues have to do with the design of the rig, and nothing to do with the design of the AAD. The exception is if the AAD cutter truly is poorer at making a clean cut. (The PIA-suggested tests would entail building two different sized rigs and firing 36 cutters, so there is some time and money involved. That's for the suggested 'required' tests, while the 'optional' tests would double the number.)

Figured I could put this into Bonfire -- My year end video at the DZ last year included a very quickly made little parody of the Dexter opening sequence, from a rigger's perspective. Worth sharing I hope. http://www.youtube.com/watch?v=Hys0hrJ00AM

For those who can't easily open Eric's .odt Open Doc file, here's a conversion to PDF, even if this is a bit late to the conversation. It sketches his thoughts on deploying a reserve past a horseshoe, MARD and no MARD.

Nothing wrong with that, but of course it can go the other way too: If it is really expensive to downsize in ideal, teensy little steps, people will be more likely to downsize in one giant step, to get the rig they'll 'grow into' and be able to hang onto for years...

No complaints with you pointing that out. But I'd say that that won't cover all aspects of the situation. A Navigator will still be better than an ancient baffed out F-111 style Manta. But that's not what we want to compare: We may want to know whether or not a medium sized or less hybrid canopy maintains performance as long as a similar size all ZP canopy. I don't know the answers though, so for all I know you're right that hybrid canopies in general have been fine for longevity -- not just physically, but in performance, which counts at higher wing loadings.

Looks like the jumps are off a big fore-aft step on a rear door C-206, something like that? (A step like that seen on Porters.) Somehow you have to get your mind working right on exit to do that little hop off the step sideways (while still crouched), and then punch out into whatever variant of arch they have taught you. Hop off and punch forward your hips, kick the legs back, get the arms out. The standard way to do something like that in the air is to practice it a whole bunch on the ground. So that no matter what you brain is thinking -- "Scheisse!", "I'm falling!" or just blanking out with all the unexpected sensory input -- when you do a little hop off a step like that, you'll punch into the arch instinctively. Practice it at the drop zone, practice it at home too (as long as you know you already have the technique right). Now that you've done a few jumps already, the problems on exit may just be more of a mental distraction, nagging your mind. But at the same time, the good thing is that you're getting used to jumping out of a plane, flying a parachute, and landing safely. Thinking of it that way, that should help make it easier to focus mentally only on the exit, during the exit.

I wasn't around tandems much at the time, so I'm just going by what old documents seem to indicate about those days...

I looked up the history to understand the timeline better myself: In May 1993 RWS (UPT) issued their bulletin (PSB#050393) about mandatory AAD's for their Tandem Vectors, that would take effect Jan 1, 1994. At the time, only the CYPRES and versions of the Sentinel were accepted for Tandem Vectors. (The Sentinal was only electrical or partially electronic -- no microcomputer control, and the altitude sensing I think was by aneroid capsule still). Strong and the USPA also thought things over and by mid 1994 both decided they would go mandatory as of July 1, 1995. [Ref.: Strong Tandem News #16, Aug 1994] When Strong made their decision, the only allowed AAD for Strong was the CYPRES. (For various reasons, Vector tandem fatalities at the time were much higher than for Strong, which may have influenced them to act sooner.) It wasn't until April 1994 that the Tandem FXC was approved by RWS after testing. So its sounds like the Tandem FXC only arrived on the marked after the mandatory rule? (That timing would also explain why my Paragear catalogs of '91 and '93 show no Tandem FXC in the FXC ads.)

One reason might be is that zero all-electronic AAD's existed until the CYPRES was introduced at the start of 1991.

Agree on the attitude. Just a side note to others: PackingJarrett's big accident wasn't related to downsizing. More of a rigging error in a multi-sport aerial activity.

Probably not a big deal to make the switch. Ideally find a larger Pilot to try out, so you aren't downsizing and going on a different style canopy all at once. FWIW, on the Brian Germain chart, which is not perfect but a standard starting point for argument, suggests a 156 canopy minimum at your point. You'd reach a minimum recommended of 150 at 100 jumps. A Pilot is a pretty docile tapered canopy. One alternative for you: get current for the season (if you aren't already), then do a few hop & pop jumps on the Pilot to try it out, then go back to the Tri for your regular jumping for a while to build some more experience.

Talk about throwing money around: You'd hope that if someone has actually spent the cash for a top of the line reserve, they would remember its name. It's like saying "My car is a high end SUV from Lexis" or "Audio" or "VMV".

Sorry, the cement block (in a deep enough river) will end up moving horizontally as fast as the river flows. Otherwise it would continually be getting drag from the side... and thus change its horizontal speed until there is none. Are you somehow thinking that gravity will tend to "straighten it out", making it fall more vertically? That won't matter. The only way for the object to avoid a push from the side is to move horizontally with the medium. You are right that something really dense, with a lot of mass compared to the drag area, will take more time until the flow around it can get it moving fully with it. I guess we think of such things as "having a lot of inertia", even if technically that has nothing to do with drag but only mass. I'll trust Kallend since he seems to know what he's doing. (Eg, 2nd order modified Euler's method in his numerical simulation. Doesn't prove anything, but you can't do that if you're clueless.) I will grant you that dense objects will take longer than we might expect to get to equilibrium and move almost fully at the speed of the fluid around them. That applies to concrete blocks, and to some extent skydivers. I'll also grant you that an object will only very slowly approach the speed of the fluid around it, when close to that speed. The cement block will reach 75 mph horizontally after a while, then ever more slowly approach 80. Theoretically it only approaches 80 asymptotically and thus never reaches it, but in practice it'll be pretty much at 80, so close that you'll never measure the difference. Mr Kallend might have been hasty in mentioning 6-8 seconds -- given that his own numerical simulation out on the web suggests longer periods. For example, one can run his freefall simulation with a 115 fps airplane speed, about 80 mph. That's an equivalent problem -- there's an 80 mph horizontal wind on the object, so when (or to what degree) does the object start to move 80 mph horizontally? It takes about 15 seconds for the 80 mph forward throw to be largely lost, but about 25 sec for the trajectory to be essentially vertical to the eye. In other words, 15-25 seconds rather then 6-8 for a skydiver to conform to the horizontal airflow around him. The time will be significantly less for less of a horizontal relative flow -- so for all I know, 6-8 seconds might work when thinking about 20 mph wind, not the 80 mph being used in the recent posts as an example. (I'll guess that one simplification in the freefall program is that the modelled drag area of the skydiver is the same from any angle, rather than calculating different drags for different angles, from a maximum for wind on the belly, and least for wind on the head. That'll affect the results somewhat.) To reiterate: Although it can certainly take longer than a few seconds for a dense object to reach the horizontal speed of the fluid flow around it, a concrete block in freefall or in a river WILL reach the horizontal speed of the flow around it.

(Type 13 for the Racer MLW actually, 7000 lbs. Reserve rear risers are type 8.)

Much appreciated, that's a very nice solution, threading a short riser through the 3-ring! That solves a lot of the direction-of-pull issues. Not much space on some mini ring rigs, but in general it'll work. (If I want to do that, I'll have to scrounge a couple more links and visit Beatnik & his new harness machine. The picture is of an '84 Racer, a rig that was old even when I bought it as my very first. Any old skydiver should know why there's a tiny divot added to the harness rings, which were forged in 1982.)

Speaking of things one isn't entirely sure about... there's that technique of 2 sets of mini rings within a large main ring. Maybe it works really well, but it is hard to feel warm and fuzzy about it the first time you see it. Even if that is the way it was or is done on a Strong Tridem in the one photo Jerry had.

Interesting one Jerry! A separable link plus webbing and ring is in some cases an alternative to an RW-6 when such a separable 3 ring isn't available. Another method for attaching a belly reserve is to put a separable D-ring on the harness (around the MLW) just below the base 3 ring. For any upward pull it just presses against where the 3 ring is built into the harness. The attached pic shows this for a separable RW-6 ring, instead of a real D-ring. (I set it up for the photos so isn't screwed on tight.) The pic shows it on an old rig where there's no mudflap that has to be pushed aside. For the RW-6, I have it attached so it 'points away from' the regular 3 ring to minimize interference, although that would put greater bending loads on it if loaded towards the top of the rig. Not sure what's best. I haven't used this method yet but have heard it being done, whether keeping the belly canopy as the final canopy, or deploying it as the first canopy (to be chopped). Any opinions on this system? Once again it is not a perfect solution at all. At least it'll only damage your chest strap if you open head down.

Forces on the rig aren't much different than for any low mounted bellymount .... but I'll grant you that containers now don't travel as far down the back as a military style backpack! We're still back to the question of what tools have been available for the job at your average DZ for intentionals onto their reserves. Maybe, compared to the very occasional ones in my local area in the '90s and early '00s, nobody really did them at other DZs??

I figure it is unlikely for the harness to have a structural failure. But yes, it is a last ditch thing, and could strip handles, hit up agains the chest strap, and cause some damage. But considering you would have used it only if your reserve failed, you might consider yourself lucky. Interesting to hear that someone actually used such a canopy! The deployment system from an old military belly mount is also not ideal. Better would be a method to toss the bagged round canopy with a long bridle out away from anything above -- like the style used for a paragliding reserve or a proper skydiving tersh. Seemed to be standard procedure around here though, because it was easily available. Sometimes one has to use a particular rig, because that is being tested, and one can't go modify it permanently. So sewing in new ring attachments, or renting some fancy 3-canopy factory rig isn't of use. Two harnesses can also have issues -- if you have a partial mal on your regular reserve, and toss out a belly mount 3rd canopy, you may be dealing with canopies pulling in different directions, crushing you in between. (Like someone local doing an intentional two out, who ended up choked unconscious by dual harnesses and risers pulling opposite directions.) Hard to find a perfect answer.

And it says nothing against wearing a second harness, or indeed using separable D-rings to add a belly mount to the existing harness. One may or may not like that solution, but it doesn't actually alter the TSO'd harness being worn. Sparky's point about the 105.3 definition of a reserve parachute is certainly an important one to this thread -- that's what suggests you need a certified reserve that you are not planning to use, that doing an intentional with just two canopies is illegal. If you are planning to use the certified reserve, then for that jump it is not a "reserve parachute" which must be "an approved parachute worn for emergency use [etc] " If doing an intentional cutaway, would strapping a belly mount to your harness with separable D rings be acceptable? I'm thinking it is OK legally. (It isn't ideal technically, but was the way that people locally used to do intentionals any time I heard of them or did them.) This parachute would be an "approved parachute", even if the method of attachment is non-standard. Other parts of part 105 mention things like "approved reserve parachute, and approved single person harness and dual-parachute container". So that's saying that the approved parachute is a separate thing from the harness. So you don't need a second approved harness underneath, for example.

Normally, round parachutes open harder at high altitude. Say, three to four times as hard at 40,000' than low altitude. [Reference: Knacke] It might not work quite the same with reefed ram air parachutes; it might be not quite so bad. Still I can say: At high altitude a jumper will take longer to get to the local terminal velocity. (One outside analysis of the planned Red Bull jump suggested 45 seconds to the peak speed.) But once at it, the dynamic pressure at say 800 mph is going to be the same as when the jumper is doing 120 mph or whatever near sea level. So that's 6.7 times as much actual speed, and thus by squaring it, 44 times as much actual kinetic energy to deal with. (Well, one isn't slowing to a canopy descent rate of zero, certainly at high altitude, but we're just looking at rough numbers here.) Whether all that energy matters depends on how fast the parachute opens -- it would be no problem only if the canopy takes a lot longer to open, with a long long snivel. On a regular skydive, if a canopy inflates fully in a very short time, the G forces get excessive when at terminal. Don't go slider off at terminal velocity. Deceleration loads are only acceptable when the full inflation starts at lower speed. So normally we need that reefing from the slider so the partially open parachute slows us somewhat before it snaps fully open. To reiterate, the wind pressure felt on a high altitude jump at high altitude terminal will be like 120 mph down low -- so there's plenty of force trying to open the canopy. The part of the deployment process where the canopy fills with air is less of a factor for squares than rounds, but in any case that inflation is affected more by the volume of air (even though it is very thin air), than the density. So the tendency, at high speed & altitude, is for much more rapid canopy filling, because there's a lot more cubic feet of air going by every second. Thus overall you still have plenty of wind pressure like usual, tons more energy, and faster canopy filling. This sounds like it should lead to much harder openings. Unless the slider somehow guaranteed a really long snivel in some manner I don't understand, a high altitude, high airspeed opening would be extremely hard.

He was indeed a great contributor in History & Trivia! Who is going to challenge us with "name that airplane" now??