pchapman

Kind of looks like one of those flares where the arms get too far out in front. Bad arm geometry for applying downwards pressure on the toggles. Add to that a Sigma canopy that has higher toggle pressures, and perhaps a stiff student resisting the flare, then any minor imperfection in the start of the flare gets magnified when it becomes hard to quickly add more flare to salvage the landing.

At one dz I'm at, handles touches and practice pulls are practiced by students when they are a little more advanced. It seems a decent compromise: Students get to touch their handles in freefall, but don't do it so early in their progression that they are likely to go terribly unstable or pull a handle accidentally. The practice pulls in freefall are introduced down the line when they transition from the student gear to the rental style gear. (Two handles rather than SOS. This applies both to PFF and traditional progression students). All novices and junior jumpers are also supposed to do a survival skills jump at the start of the season. Practice pulls in freefall get people used to the sudden head down dip that may happen depending on arm position. They are also supposed to do a handles touch during opening during that kind of jump, as if they were having a mal on opening. It's good for checking where handles might have shifted.

IAD is an accepted procedure, but, yes, it is more complex for the instructor than tossing static line students. The instructors do need more in depth training. There are procedures to control the bridle so that the bridle and PC stay near the student, and you don't have the student "getting away". Yes, you sure don't want to snag the bridle. I'm not an IAD instructor but one technique I've seen, for example, is to keep the PC held at the upper back (bottom of neck) of the student, with one's hand always following the student's movements. That should avoid having the PC still in the airplane while the student rushes out on the step and that sort of thing. I only skimmed the original video and I'm not sure how well the IAD was done in it.

Because the original poster is in the USA. EVERY thread about low bulk reserves goes like this: "Get an Optimum" - guy from USA "Hey there are a couple great European low bulk reserves too." - guy from Europe "Europe? Wasn't that something we bombed or saved or seceded from years ago? Irrelevant to US skydivers anyway." - guy from USA But seriously, are there dealers for the European equipment in the USA? Without that, it's hard to break into the US market. I know Chuting Star is a dealer for the Basik rigs (the Seven), but Basik reserves don't seem to be sold. (I just checked the store's web page.)

Why hasn't it been mentioned? Because we're not going to sit here and write down everything we know about canopy control. Of course you need to learn how to flare right, and learning to flare properly will help his landings. But the OP has somehow gotten to where he is with very little knowledge about canopy flight. How that happened, we don't know. Whatever good knowledge there might be on his DZ, doesn't seem to have been taught to him. There are bigger issues here than just fine tuning the flare. And you don't downsize first, and then learn to flare.

Poynters: "The ripcord led to cones or wire loops in each corner of the back side of the container; the cover wrapped around the canopy and lines and was secured at each corner. After the ripcord released the corners, it pulled a web strap which aided in removing the cover and then another strap under the top fold of the canopy assisted it into the air." Poynters has a small picture, but it still isn't clear to me just how that works. Possibly the strap inside did a zig zag of sorts through the folded canopy that would tend to move some of the canopy about when yanked. (Rather than just having the strap slide out from between the folds, leaving the canopy undisturbed.) Just guessing. Still it all seems to be a variation of "dump it in the air canopy first". Nice find. Pages 0956 to 0959 of that Flight magazine are about Irvin parachutes and Russell parachutes. P.S.-- Who needs a pilot chute anyway? They seem to be suspicious newfangled things. As quoted in the Irvin part of the report: "One respect in which it differs in design from some other parachutes, is the attachment of the small pilot parachute which springs out sharply when the rip cord ring is pulled during descent and pulls the large canopy out. But it is by no means necessary for safe functioning. The Irvin will open just as well without its pilot chute, which can be described as a sort of extra safety device. When the question as to its necessity was raised in America, the U.S.A. Air Services decided that if it was not absolutely essential it certainly did no harm and they decided definitely that it should remain. It speeds the opening of the parachute rather than retards it and thereby allows for safe jumps from very low altitudes."

Ruthers: John S. was talking about the force to pull the bag out of the container, how tight the container can be, rather than the other issue of the force that the pilot chute can apply. But yes there is the issue of how good a pilot chute one needs to have. Usually we make do with the same PC whether it is a student (or tandem reserve) or a PD 99 reserve.

To quantify things: (200 lbs + 25 gear)/170 = 1.32 wing loading at 75 jumps. And PD's wing loading table for the Spectre shows 221 lbs (1.3 loading) for 'experts', although 255 lbs (1.5 loading) as the absolute maximum suggested.

(off the main thread topic) Yet I've seen V3's a few years old where the RSL was chewing up the reserve risers. Had to sew a type III tape cover flap over the RSL area. The RSL hook and the harness pile velcro were the same width. Other rigs (newer ones?) have wider pile velcro, reducing the chance for stray hooks to catch on things.

I've got a Sansa Fuze. (Not the Fuze+ that has a bit fiddly touchpad) They're not as sophisticated in in the interface as the Sony's, but they are functional and have easy to read screens. No special s/w needed. (Except for transcoding videos, as they only take a very specific video format.) Refurbished ones are cheap and one can stick in a big uSD card. The controls are particularly good for activating without looking at them. Not the "best" solution but acceptable.

Big issues here are skydivers' understanding of the 300 ft thing, and the actual distance required to open a reserve. As for the "opens in 300 ft" thing, skydivers sort of know that as the requirement for reserves. But when one looks at the certification regs, it isn't quite as clear cut. (John Sherman of course understands this.) When testing reserves for opening after a cutaway, the jumper can be flying at speed under a main canopy, so it isn't starting with a vertical direction of motion, nor is it done from zero initial speed. And the high speed tests don't have to be done vertically -- typically it is a horizontal test from an aircraft, making it much easier to stay within a 300 ft limit. There's also a 3 second opening limit, so that helps restrict things a bit. (If one were doing 174 fps straight down, that would give 522 ft max, but that's only for an unrealistic full speed plus instant stop at the end, so a lower distance would be more typical.) There's a lot more to the regs but I think this is a reasonable simplification. The times and distances were I believe similar in earlier certification standards but I'm not sure off hand. Also, in certification tests I am a little suspicious about the definition of "functionally open". While that includes total speed and rate of descent limits, I wonder how accurately these are measured, whether in actual tests the clock has ever been stopped while the canopy is still mushing or diving, not yet in steady state flight, despite having full inflation and slider down. Nor do the tests have to reflect any sort of realistic container configuration, such as tight modern rigs. From a skydiver's point of view, whether or not it is realistic to have reserves always open within 300 ft, it all seems a big gyp. Now that's only based on skydivers' imperfect understanding of the certification rules, and companies have technically followed all the requirements. In the end, it really means I'm not quite sure how much distance it takes for reserves to open in realistic situations. Which makes it hard to plan for how high AAD's should fire, even if there is some evidence that altitudes might be bumped up a bit. An added complication is the whole belly vs back compensation, so you get existing AAD's sometimes firing at say 1100' if someone is finshing snivelling down through that altitude.

How about the "in the pocket" test? That one can pause and resume music, and adjust the volume, just by grabbing the gadget without looking at it? That's one thing some of us worry about touch screen devices, even if they allow large screens and otherwise easy to use interfaces.

These sorts of threads always end up bringing out certain themes. There's the BASE jumps, not really intended for the thread. Then there are the one-upmanship stories of deliberate low pulls (I've got 'em too), the stories from the old days with faster opening canopies, and the stories about losing altitude awareness. The latter are probably the most instructive.

Now there's something for discussion! ... in another thread at another time. But one can't help but snicker a little.

But it is reasonable for "the rules" to cover "most typical equipment". At some point, there is a judgment made that some equipment will be considered atypical and the user of the equipment should know the special procedures for that equipment. I won't get outraged if someone says, "arch after cutting away", because that is the wrong thing to do if you are jumping a bellymount, which I occasionally do.... So the "RSL lanyard catching risers or lines" is still the normal answer. More info can then be added for a more detailed answer.

The point is that the temperature sensor measures the temperature at or near the pressure sensor, as part of the process of measuring pressure accurately. It is about the temperature of the pressure sensor, not of the air outside. That's a separate issue of trying to convert a pressure into an accurate measure of altitude. ======= Regarding Nelyubin's post: Cypres 2 manual: storage +71 to -25 C, working +63 to -20 C Vigil II manual: working temperature +71 to -25 C (with this listed as the range in which the battery pack is designed to operate) Therefore both are virtually identical. Any differences are likely due to company decisions on how conservative to be in their recommendations, and not any underlying differences in design. So for neither AAD should you leave the rig in an unheated building in the middle of the Russian winter. Presumably someone from a cold climate will have asked an AAD company about such events, as it will have happened, and I doubt anyone advised them to throw out their AAD. (Although you could make the point that at least with the Vigil, you can go check the unit temperature on screen in the morning.) P.S.: Argus manual "Storage temperature: -40° to +80° Celsius Working temperature (inside reserve container): -30° to +70° Celsius " That's a little wider range. But without any other evidence I'm not convinced it is built fundamentally any differently.

Temperature sensors I'll bet that a temperature sensor inside the case would be useless for adjusting the lapse rate curve. The sensor would only be there to calibrate the pressure sensor or some such thing. (ie, if the voltage output of the pressure sensor varied when the temperature of the chip changed). To create an accurate lapse rate of pressure vs. altitude, from some standard graph under standard conditions (eg, some form of the International Standard Atmosphere), one needs to know the average air mass temperature from the measuring altitude down to the ground. In practice, just knowing the temperature of the air at the altitude where the temperature sensor is, will give a rough approximation. Pilots may do that when calculating true airspeed for example. A temperature sensor deep in the reserve tray, inside a box, is probably of little use for adjusting the pressure lapse rate curve. Especially because there will be plenty of times that its temperature will have little relation to outside air temperature -- maybe the rig was in a hot car or in a cool hangar just before the jump. Pressure lapse rates There is indeed some error introduced if an altitude "measuring" device doesn't know where its starting altitude is. The pressure change that at sea level gives an 800 ft jump in altitude, would give 930 ft if starting from 5000 ft. I'll be using 800 ft in my examples as a hypothetical CY-Vigus AAD's firing altitude. (FWIW, I'm using one particular pressure lapse rate formula, p [inHg] = 29.9212 * (1- (alt [ft]/145442.1)^5.25588. I don't have its source at hand but my old notes show this came from my search of the aeronautical literature as a decent formula.) But, AAD's do know their starting pressure on the ground, so they have a starting point. They don't need to know the true altitude at the airfield, just the pressure. Whether they calculate a curve or use a lookup table, I would guess (and hope) they don't use a linear relationship between pressure and altitude. For AADs they only typically need to be extremely accurate over a short distance, such as 800 ft off the ground, so a particular percentage error in a calcuation won't be a big deal. But absolute pressure errors in the sensor do still count for something. So lets say the sensor in a Cypres is off calibration, or it is off in a Vigil and the owner doesn't actually go and compare the pressure against some calibrated barometer or aircraft altimeter. (It's a nice to have feature, but in practice you don't hear of anyone doing it. Lucianofly gave a good if rare example of someone with a fleet of Vigils actually comparing the pressures shown on them all, to help detect an anomaly!) Anyway, say the AAD is at sea level and is supposed to fire at 800 ft, so (by my calculation) it is looking for a .85455 inHg reduction in pressure. But say that the sensor is off by 2% in its accuracy, which (in one direction) would make it think it is starting at 557 ft. When it sees a .85455 inHg loss of pressure, and thinks the AAD is 800 ft over the ground, it turns out to actually be at 813 ft above the ground. Not too bad actually, for an error coming from a 2% sensor error. (The error in height, 813 vs 800, is only 1.69%). BUT, if the AAD were more sophisticated, it could do much better: If the AAD looked for a certain percentage decrease in pressure, rather than a certain absolute decrease in pressure, the error would be much less. (Pressure after all does decay in a non linear way, so a ratio is a much better approximation.) So instead of looking for .85455 inHg pressure decrease, it would be looking for a pressure that is 97.147% of the original. Then my calculation shows it will fire at 796.9 ft, rather than 800ft. That's an improvement, off by about 3 ft not 13 ft. In that way, even a 2% error in the sensor gives only a 0.4% error in firing altitude. Who knows if AADs are smart enough to behave this way. An engineer should easily see the principle; but the answer depends on the computing power available. (These errors will change with altitude, so using the sea level to 800 ft case is just an example.) Temperature errors Now there's another confounding variable, the temperature of the air over the height being measured. I'm not sure of the correct calculations off hand, but I can use an approximation. The error in altitude is approximately 4 ft per 1000ft of height above a known reference point (eg, airfield), per degree Celsius away from the International Standard Atmosphere temperature (for that particular altitude). Colder air produces lower true altitudes than measured from the pressure. Example 1: Sea level DZ, -5 C in winter, ISA temperature at that altitude is set at 15C, so the temp is 20 C low, with the AAD trying to fire at 800 ft. The error would be 800/1000*20*4 = 64 ft. The AAD will fire about 64 ft low. Example 2 would be Denver in summer. Say 5000' elevation, where ISA should be 15- 1.98*5000/1000 = 5.1C. If the actual summer temp is 20 more than that, or about 25 C, the approximate calculation will this time give 64 ft high. Using a pilot's circular slide rule to calculate corrected altitude from pressure altitude, should give a more accurate answer, as it will provide for calcuations that are not linear but ratio based (or logarithmic). The slide rule suggests the error is more like 55 ft. So were talking about firing 55 ft high for an 800 ft firing altitude, or about 7% high. All this shows that temperature errors, over ranges that are wide but are encountered in practice, can cause some significant AAD errors, although not huge amounts. I kind of doubt that AADs have any way of compensating for this, but I just don't know. Conclusions? Hard to tell since we don't know how AADs actually calculate things. But all this gives some idea of how big errors in firing altitude might be, when an AAD is being fooled by atmospheric conditions other than some idealized situation, or due to errors in the pressure sensor. It isn't that Cypres' couldn't implement some sort of pressure readout, as Military Cypres' do that. (Just guessing that it is probably the altimeter setting readout, which is what the pressure would be at sea level, rather than the pressure actually seen at the moment.) AAD's also have to calculate vertical speed, but at least by looking at height alone, we can see some of the issues in AAD errors. Algorithms Abedy wrote: Ah, that's all the Airtec secret stuff!

So some conclusions about C23b from John S. seem to be: -- One needs to know speeds, weights, and force levels as well when mixing and matching components, because different canopies will produce different forces on the harness at a given weight and speed. That's pretty obvious when one thinks about it, but it is easy to overlook too. -- Some C23b canopies may not be able to take the forces they were supposed to take, even though in practice they may be good to whatever speeds & weights they were tested to successfully. How bad that is, can be argued. If a canopy can be built to open slower, it can be built lighter. But I can see that one wants some excess strength if there's much chance at all that a small percentage of the time, much higher forces could be generated. So a lightweight round may be OK as long as the diaper, when used correctly, is highly reliable in function. (I have a little more of a fixation on rounds than most people, because I jump vintage equipment at times, and so deal with round mains & reserves.)

[Just writing this as a skydiver interested in certifications, but no experience with TSO testing:] I agree with the PIA's response that the new AC105 has problems when it comes to C23b. But some of what was in the PIA statement also has problems when it comes to C23b. I contacted the PIA about this and one rigger agreed (in his opinion) that their response should have been better on that particular issue. The way C23b was handled, with a lot of uncertainties about the forces actually generated by different canopies, sure makes it difficult to integrate with more modern certifications. Some C23b equipment has no weight or speed limitations listed, because that wasn't part of the certification. On the other hand, some do have limitations listed by the manufacturer. It isn't clear how hard those limits are supposed to be. In some cases, weight limits seem like they are partially about tolerable rates of descent rather than structural limits. The problem with the PIA response stems from referring to that old NAS804 table which was about C-9's only. The PIA's response to AC105D would mean that the combination of a strong harness and a lighter weight reserve might end up approved to a very high level of weight and speed, because that's what comes out of reading the NAS 804 chart. John Sherman made the offhand comment: I'm not sure what that's about, maybe the whole thing about adding Kevlar bands to Phantoms, well after they were certified. But anyway, a tiny bit of public information about C23b certifications came out in an NTSB report after a Sukhoi 29 pilot bailed out at high speed in 1996 and blew every line off his Phantom 26, probably because of pulling while still at extremely high speed, way above recommended Phantom limits. [the report is # FTW96FA151 ] From the report, it appears that when the Phantom series were certified, the choice of speeds and weights were theoretically calculated to give the 5000 lb load, and the NAS-804 table was NOT used because it was deemed inapplicable. The canopies were tested to a far lower weight and speed than on the table. The NTSB report suggests that the theoretical calculations were not backed up by any measurement during testing -- so the actual loads on the canopies is unknown. It is unclear how the FAA may have approved the theoretical procedure, as no paperwork remains after so many years. This isn't to say that the theoretical calculations weren't right; just that it is very hard to now decide how strong C23b canopies are, without going through new certification tests. All this matches nicely with the types of things John Sherman wrote here, how the C23b certification process could vary between FAA regions and between parachute companies. So the real strength of any canopy from C23b will in some cases be "who knows", making it difficult to integrate with newer C23 versions that list specific tested weights, speeds, and forces.

I don't believe there is a definition anywhere of when a reserve is no longer a reserve. In grey areas it is up to the rigger to determine airworthiness. The description in the Raven manual (written many years back) obviously has its issues and isn't a clear cut definition of what is allowed. Depending on interpretation, it makes it sound like one jump with the canopy in the main container is allowed, before packing it as a reserve, and that an intentional cutaway later on would ground the reserve. A few jumps on a reserve doesn't destroy it, whether from a main container, as an intentional cutaway, as a needless cutaway from a popped toggle, or as cutaways due to a poorly packed, out of trim main canopy. Even for a PD reserve with its service limits, you could do 25 jumps on the reserve before PD would like you to send it back for checks...

No big conclusion, no null hypothesis to disprove. Just one of those things where new information is extracted from a bunch of data. Never seen such info summarized before. One would indeed learn more from, say, checking the reserve ages of all jumpers at different DZs. I just found it interesting to see the age ranges of reserves being used. They're certainly not all nearly new.

Great, no location, no profile, totally new accusation without details. Care to provide more info?

When I return to the Atmonauti.com page, with its annoying Flash crap, it still has all this pseudoscientific posturing about things like the nature of lift, and statements like, "Tiezzi invents the Atmonautics, a new science that studies the use of the human body in the atmosphere". Move over physics and aerodynamics, Atmonautics is here! Despite the insufferable nature of those guys, I do like playing with a little atmo as an amateur when I find someone else to try it with. Atmo is a term that is useful in distinguishing the type of dive, whatever the politics behind it.

I was curious about how old reserves have been, at the time they were used. So I went through my own saves list of 49 so far. This doesn't really mean much; it's just a matter of curiosity about the numbers, and something one can't see by looking through the typical saves lists on the web. A histogram is attached, showing reserve ages at time of use. Data was collected by year only. The average is 10-11 years, with the most common age being 12 years. Only one was a round, the very first, 18 years old at the time. The oldest were 24, an original Swift deployed after a CRW wrap last year, and a Firelite in rental gear this year. Saves on jumpers' own gear 15-20 years old is less, but certainly does happen. The second graph shows the saves chronologically, and also breaks the gear down into the 31 owned by jumpers, 7 tandem rigs, and 11 other dropzone owned rigs (student or rental gear). That's just to give an impression of the type of rigs involved, but the different types used in different years don't mean much, as the amount I've packed for DZ's has varied greatly over the years. The DZ rig reserves have tended to be a little older, for the ones I packed.

Most were many years back; he came back to the sport recently.