skydiverek 54 #1 March 28, 2005 I am trying to find out the percentage of mesh and fabric on different reserve PCs. I'm just curious how they are built, since I know there I advantages and disadvantages of certain designs. So far I know: - Vector 3: fabric 100%, mesh 0% - Wings: fabric 80%, mesh 20% Riggers - could you continue and complete the list with your estimates? - Racer: - Quasar II: - Javelin: - Infinity: - Mirage: - Reflex: - Dolphin: - Centaurus: - Talon/Voodoo: - Atom: - Sidewinder: Thanx Quote Share this post Link to post Share on other sites riggerrob 558 #2 March 28, 2005 Sidewinder uses a Vector II reserve pilotchute, ergo 100% fabric with no mesh. Most of the rest are 50% - 50%. The Stealth pilotchute installed in Voodoos and post 1993 Talons has more fabric than mesh, but that is because the spring is so long. Quote Share this post Link to post Share on other sites badlock 0 #3 March 31, 2005 There's also the "Powershot" from the Paratec Next-Container (see images) Don't be a Lutz! Quote Share this post Link to post Share on other sites payback462 0 #4 April 1, 2005 i think the VSE infinity is around 90% fabric 10% mesh, or about that (pic is in the manual) javelins are 50/50, or really close to it. as well as the reflex and the quasar i personally have my own opinions on what the best design is, but im going to keep them to myself Quote Share this post Link to post Share on other sites skydiverek 54 #5 April 1, 2005 Some opinions which design is better can be found in this thread titled "Reserve Pilotchute: Meshless or with Partial Mesh?" here: http://www.dropzone.com/cgi-bin/forum/gforum.cgi?post=476690#476690 Quote Share this post Link to post Share on other sites RMURRAY 1 #6 March 23, 2014 what matters is the cd (or in the end, drag) not mesh vs non mesh. was there a design change on the rig that towed the reserve pc? if not I cannot understand how the sell any... or used ones are sold at any price...unless like bill b says skydivers do not care about safety. Quote Share this post Link to post Share on other sites dpreguy 14 #7 March 23, 2014 What would be the value of knowing these ratios? Quote Share this post Link to post Share on other sites RiggerLee 61 #8 March 23, 2014 Well if you're interested in design it's a very relevant question. But I don't think it's well defined. Are we talking surface area? Vent area? Diameters? And I think there are a lot of other factors. Is there any shape to the fabric or mesh. For instance I've built PC's with both shaped panels and conical mesh. If you want to make this a real discussion I think that would be cool. But if you're just trying to make an end run around bad mouthing particular manufacturers then I think it's pretty weak. I'd much rather you just came flat out and said, "Hay! What's up with these towed PC's? Why aren't there any upgrades or replacement higher drag versions available yet? I mean manufacturers have responded much faster in the past with SB and upgraded pilot chutes for much smaller problems or perceived problems and there weren't even fatalities involved. Is that the problem? Now that some one's dead you are afraid to correct the problem for fear of admitting liability? I'm not saying that that's the case. But if you want to talk about it, man up and say it. Don't pussy foot around the topic with some discussion about design. I can go ether way on this. We haven't had a fun design question in a while. We also have not heard any thing about the PC in tow/delay issues for some time. The question isn't going away. And if the gear can not meet the TSO standards, as proved in the videos (plural), then the TSO should be void till the problem is corrected. I think there are real questions about the legality of some of this gear being jumped and the legality and liability of packing it as a rigger. When you sign that card you're saying that the rig can still meet the standards of the TSO. Pick a topic. Game on. LeeLee [email protected] www.velocitysportswear.com Quote Share this post Link to post Share on other sites riggerrob 558 #9 March 24, 2014 Mischevious .... How do you count Magnum pilot-chutes? They may have a cone of fabric and a cone of mesh .. similar sizes, but there is an extra cylinder of mesh hanging out the bottom .... because of the extra-long spring. Hee! Hee! Quote Share this post Link to post Share on other sites rifleman 61 #10 March 24, 2014 Completely noob questions here - if the reserve pilot chute isn't extracting the reserve, wouldn't it be advisable to make the RPC slightly larger (say an extra 4" diameter)? Also are RPC's ZP or F-111? Which is more effective (I get that F-111 needs to be replaced more often than ZP but if it's more effective then surely it's worth the expense)? As I say, noob questions, but I'm just interested and the next time I'm at the DZ I'll probably be asking one of the riggers anyway.Atheism is a Non-Prophet Organisation Quote Share this post Link to post Share on other sites RiggerLee 61 #11 March 24, 2014 I honestly don't think f-111 or zp makes that big of a difference in pilot chutes. A PC is really crude. In some thing larger where it can affect the boundary and the separation point like a round parachute it can have a noticeable affect on the oscillation and CD. Reserve PC's have been made from both. I think the size and design are more relevant. And you're question is not a completely noob question. I've been doing this for 20 years and I would really like to know why I am not allowed to put a larger higher drag PC in my reserve. That's a bit of a dig but there has been some discussion about this but nothing has happened. The truth is I'm not sure how easily some of these things could be corrected. A larger PC would really be more of a stop gap measure. Not a bad one but still a band aid. It might be fun to go back and time some of those videos. If you could take a guess at the speed where the bag finally extracted you could make a pretty good estimate of how much larger the PC would have to be to extract the bag in time to meet the TSO requirements. I don't have time at the moment. A better solution might be to just use an off the shelf TSO'd PC from another manufacturer, larger with a higher CD, but although that is permitted by the FAA it is forbidden by the rig manufacturers. And yes I'm stirring the pot here a little bit but I'm board and need some entertainment. So that's where we stand. When you have a malfunction and you need to cut away, from a perfectly reasonable height from which the FAA says that you're reserve should open, it will in fact tow into the ground and you will be laying there broken open like a ripe tomato. Now scream and run around in circles pulling your hair out for our amusement. And start stretching so that you will have the flexibility to reach over your shoulder and grab the bridle. Because that's your new emergency procedure. Deploy PC, deploy bag. Pull red. Pull silver. Reach back, grab bridle. Deploy reserve. Some body send him the link to the hand deploy. Mean while I will go and make popcorn. LeeLee [email protected] www.velocitysportswear.com Quote Share this post Link to post Share on other sites councilman24 36 #12 March 25, 2014 RiggerLee We also have not heard any thing about the PC in tow/delay issues for some time. The question isn't going away. And if the gear can not meet the TSO standards, as proved in the videos (plural), then the TSO should be void till the problem is corrected. I think there are real questions about the legality of some of this gear being jumped and the legality and liability of packing it as a rigger. When you sign that card you're saying that the rig can still meet the standards of the TSO. Lee But the TSO standard is in no way a quality control standard either of manufacture, component assembly compatibility, packing, wear or any of the other things that can effect performance like body position (towing over the shoulder on your back). Its best described as a design confirmation program. There is a quality control manual required that assures some minimum consistency of articles. But the TSO program really asks CAN the test article(s) meet the required test standard, not WILL all individual items or all combinations. Doesn't mean that any individual article the will meet requirements either as tested and certainly not under conditions not tested. What isn't tested? Almost everything. Certainly most of the sizes and nearly all of the size combinations of rig and canopy are not tested. Neither is routing the PC bridle over your shoulder on your back. There was absolutely no reason for that PC to be expected to extract the bag. I would argue that a rigger is not certifying that the rig would pass the TSO standards even under perfect conditions. Almost certainly that combination wasn't tested, obviously that particular set wasn't tested, and probably not even those sizes of canopy and container individually were ever tested. We're certifying that we followed the instructions, that as best we know with the information provided by the manufacturers that this combination should work. BTW that information is very minimal. About ten years ago when writing PIA TS-135 the French government was that insisting rig manufacturers list ever reserve/size that could be put in a particular model rig. Even this wasn't practical or possible because of the "mystery bulk" issue. Or better said the volume variation (up to 10%) in both canopies and containers. One set of gear with the canopy at the small side and the container at the large side may fit fine. Those same models/sizes at the reversed ends of the ranges (small rig and big canopy) may not fit. Of course testing all the combinations is not even imaginable. Think about it. Only a couple of canopy sizes are tested, only a couple of containers, and if at all only one size combination at each end. You could almost be surprised when a rig does work.Is this what we want to know or believe? No. But it's reality. Should riggers say no to more of the rigs? Probably. Will the rigger down the road do it? Sure. Maybe you shouldn't have given that seminar on how to put 10 pounds of shit in a five pound bag..I'm old for my age. Terry Urban D-8631 FAA DPRE Quote Share this post Link to post Share on other sites JohnSherman 1 #13 March 25, 2014 QuoteRiggers - could you continue and complete the list with your estimates? - Racer: Racer : 50%-50% Open mesh (important) Here is a chart showing a summary of the Force vs. Dynamic Pressure (altitude & speed) of all know pilot chute tests. [inline Drag_Capabilities_of_Tested_pilot_chutes.jpg] Quote Share this post Link to post Share on other sites roostnureye 2 #14 March 25, 2014 JohnShermanQuoteRiggers - could you continue and complete the list with your estimates? - Racer: Racer : 50%-50% Open mesh (important) Here is a chart showing a summary of the Force vs. Dynamic Pressure (altitude & speed) of all know pilot chute tests. i didnt happen to see Vector 3 in that chart????Flock University FWC / ZFlock B.A.S.E. 1580 Aussie BASE 121 Quote Share this post Link to post Share on other sites pchapman 261 #15 March 25, 2014 roostnureye i didnt happen to see Vector 3 in that chart???? Same PC as a Vector II. Quote Share this post Link to post Share on other sites riggerrob 558 #16 March 26, 2014 Most reserve pilot chutes are made of F-111 fabric, while a few are made of ZP fabric. New F-111 fabric will pass zero to 3 cubic feet per minute of air, while new ZP fabric passes zero cfm. That makes for an insignificant difference in porosity and drag. At those porosities, the pilot chute configuration and number of needle holes make bigger differences. Porosity will only change after 40 or more pack jobs - roughly 20 years in service. By the time a pilot chute is 20 years old, many riggers will refuse to repack it. Quote Share this post Link to post Share on other sites riggerrob 558 #17 March 26, 2014 ... I would really like to know why I am not allowed to put a larger higher drag PC in my reserve. ... Lee ...................................................................................... If yo install a humungously, ginormous, over-sized reserve pilot-chute, it might create so much drag that it exceeds the ability of the safety-stow to hold the free-bag closed until line=stretch. Instead, it will jerk the free-bag off your back so quickly that you will suffer bag-strip, which will leave you still iin free-fall ... but without your free-bag and pilot-chute. The reserve canopy and lines will still be flopping about on your back. Sometime late, a side gust might push the reserve canopy off your back ... line stretch ... inflation ... etc. It is rumoured that this killed a Golden Knight about 30 years ago. That was back during the early days of square reserves. That accident motivated Para-Flite to invent Safety-stows (mid 1980s). Safety-stows are less likely to suffer bag-strip because their line stows are balanced. Quote Share this post Link to post Share on other sites RiggerLee 61 #18 March 26, 2014 In theory.... But I was referring to other TSO'd pilot chutes tested in the same speed regimes with equivalent deployment systems. Let's face it, every one, with the exception of Sherman, uses essentially the same safety stow deployment method. And there isn't that much difference in the speeds that the containers are TSO'd to. I think there is a good argument for compatibility. I think you could put a Mirage PC in a Vector 3. I think that with just a little work, minor change, snaps, Sandy could put a Stealth in a Wings. I do think that the fundamental problems in container design should them selves be addressed. But in the mean time I see no harm in upgrading our PC's. Because towing a PC into the ground is just not cool. LeeLee [email protected] www.velocitysportswear.com Quote Share this post Link to post Share on other sites JohnSherman 1 #19 March 26, 2014 QuoteIf yo install a humungously, ginormous, over-sized reserve pilot-chute, it might create so much drag that it exceeds the ability of the safety-stow to hold the free-bag closed until line=stretch. Instead, it will jerk the free-bag off your back so quickly that you will suffer bag-strip, which will leave you still iin free-fall ... but without your free-bag and pilot-chute. The reserve canopy and lines will still be flopping about on your back. Sometime late, a side gust might push the reserve canopy off your back ... line stretch ... inflation ... etc. It is rumoured that this killed a Golden Knight about 30 years ago. That was back during the early days of square reserves. That accident motivated Para-Flite to invent Safety-stows (mid 1980s). Safety-stows are less likely to suffer bag-strip because their line stows are balanced. No pilot chute will have enough snatch/drag to strip a bag off of a canopy if the bag is properly designed. The “Safety Stow” is not such a design. Any bag design must retain the canopy until the lines are extended in ALL CASES no mater how big or powerful the pilot chute is. A “Safety Stow” is a continuous loop of 1/8” Bunge cord folded in half and threaded into a channel grommeted on both ends. The loops exit the channel through the grommets at each end. This replaced the Buna-N “O” rings which were the root cause of the GK tragedy. This new design (the Safety Stow) provides no stiffener to hold the grommets in separation during line bight extraction and in practice is no better than the Buna-N “O” rings. This allows one stow to have an retention force of 12 pounds +/- and forces the other stow to have little or no retention force because the grommets are forced together during packing. Even though the stows are balanced they easily allow the loose stow to escape during bag extraction, especially at terminal. When one of two locking stows release on a “Safety Stow” bag it releases the canopy from the bag – “Line dump”. This is likely when using a Velcro pouch with only 12 square inches of Velcro is attempting to hold the mass of the entire length of lines in the pouch during extraction. This works well on low speed deployment but there is a vast amount of data which indicates a problem when this system is used at terminal. No manufacturer can prevent you from installing a better pilot chute, in a reserve, no matter what they say in their manual. They don’t have the authority to override the FAA permission granted in AC105. As long a there is no degradation of performance you may make the change if it is functionally compatible. Quote Share this post Link to post Share on other sites koppel 3 #20 March 26, 2014 JohnSherman. As long a there is no degradation of performance you may make the change if it is functionally compatible. How would one be expected to document this for the FAA?I like my canopy... ...it lets me down. Quote Share this post Link to post Share on other sites councilman24 36 #21 March 26, 2014 Drop tests. Impractical And if an incident the manufacturer will throw the rigger under the bus.I'm old for my age. Terry Urban D-8631 FAA DPRE Quote Share this post Link to post Share on other sites JohnSherman 1 #22 March 26, 2014 QuoteDrop tests. Impractical Drop test are no problem. I plan to do a bunch during PIA next year and I will use this procedure. Try it you will like it. Quote Share this post Link to post Share on other sites councilman24 36 #23 March 26, 2014 John, My answer was to was the feds would take as data that other than the OEM pilot chute would work in a rig.I'm old for my age. Terry Urban D-8631 FAA DPRE Quote Share this post Link to post Share on other sites JohnSherman 1 #24 March 27, 2014 QuoteMy answer was to was the feds would take as data that other than the OEM pilot chute would work in a rig. Terry, A presentation to the FAA with data collected from free drop test along with a demonstration of function and the feds would have to buy it as it would be correct. However, such a process is not necessary as a rigger has the authority granted in AC-105. But! That rigger had better be ready to present such data if the sky falls in, as they would be subject to severe pier and FAA review. This simple free drop test which I present works. It is sound engineering using traditional formulas. I present it for review to anyone who wishes to comment or question the procedure. Do the test I propose with the OEM pilot chute and the proposed pilot chute. Compare the data. If the results are satisfactory for justification of replacement then, document the tests and present it. While I say that such a presentation is not necessary there would be no harm in doing it in this case as it would validate the process. BTW: You must share the data here. Quote Share this post Link to post Share on other sites JerryBaumchen 1,047 #25 March 27, 2014 Hi John, QuoteIt is sound engineering using traditional formulas. You have this formula: Drag = Cd*So*Q Then you say: Cd is the Drag coefficient of the device. So is the Square footage of the device as shown in plan form. Q is the Dynamic pressure or 1/2 Rho V^2 V is the velocity in Feet per second. Where is V in the formula? JerryBaumchen Quote Share this post Link to post Share on other sites Prev 1 2 3 Next Page 1 of 3 Join the conversation You can post now and register later. If you have an account, sign in now to post with your account. Note: Your post will require moderator approval before it will be visible. Reply to this topic... × Pasted as rich text. Paste as plain text instead Only 75 emoji are allowed. × Your link has been automatically embedded. Display as a link instead × Your previous content has been restored. Clear editor × You cannot paste images directly. Upload or insert images from URL. Insert image from URL × Desktop Tablet Phone Submit Reply 0 Go To Topic Listing
riggerrob 558 #2 March 28, 2005 Sidewinder uses a Vector II reserve pilotchute, ergo 100% fabric with no mesh. Most of the rest are 50% - 50%. The Stealth pilotchute installed in Voodoos and post 1993 Talons has more fabric than mesh, but that is because the spring is so long. Quote Share this post Link to post Share on other sites
badlock 0 #3 March 31, 2005 There's also the "Powershot" from the Paratec Next-Container (see images) Don't be a Lutz! Quote Share this post Link to post Share on other sites
payback462 0 #4 April 1, 2005 i think the VSE infinity is around 90% fabric 10% mesh, or about that (pic is in the manual) javelins are 50/50, or really close to it. as well as the reflex and the quasar i personally have my own opinions on what the best design is, but im going to keep them to myself Quote Share this post Link to post Share on other sites skydiverek 54 #5 April 1, 2005 Some opinions which design is better can be found in this thread titled "Reserve Pilotchute: Meshless or with Partial Mesh?" here: http://www.dropzone.com/cgi-bin/forum/gforum.cgi?post=476690#476690 Quote Share this post Link to post Share on other sites RMURRAY 1 #6 March 23, 2014 what matters is the cd (or in the end, drag) not mesh vs non mesh. was there a design change on the rig that towed the reserve pc? if not I cannot understand how the sell any... or used ones are sold at any price...unless like bill b says skydivers do not care about safety. Quote Share this post Link to post Share on other sites dpreguy 14 #7 March 23, 2014 What would be the value of knowing these ratios? Quote Share this post Link to post Share on other sites RiggerLee 61 #8 March 23, 2014 Well if you're interested in design it's a very relevant question. But I don't think it's well defined. Are we talking surface area? Vent area? Diameters? And I think there are a lot of other factors. Is there any shape to the fabric or mesh. For instance I've built PC's with both shaped panels and conical mesh. If you want to make this a real discussion I think that would be cool. But if you're just trying to make an end run around bad mouthing particular manufacturers then I think it's pretty weak. I'd much rather you just came flat out and said, "Hay! What's up with these towed PC's? Why aren't there any upgrades or replacement higher drag versions available yet? I mean manufacturers have responded much faster in the past with SB and upgraded pilot chutes for much smaller problems or perceived problems and there weren't even fatalities involved. Is that the problem? Now that some one's dead you are afraid to correct the problem for fear of admitting liability? I'm not saying that that's the case. But if you want to talk about it, man up and say it. Don't pussy foot around the topic with some discussion about design. I can go ether way on this. We haven't had a fun design question in a while. We also have not heard any thing about the PC in tow/delay issues for some time. The question isn't going away. And if the gear can not meet the TSO standards, as proved in the videos (plural), then the TSO should be void till the problem is corrected. I think there are real questions about the legality of some of this gear being jumped and the legality and liability of packing it as a rigger. When you sign that card you're saying that the rig can still meet the standards of the TSO. Pick a topic. Game on. LeeLee [email protected] www.velocitysportswear.com Quote Share this post Link to post Share on other sites riggerrob 558 #9 March 24, 2014 Mischevious .... How do you count Magnum pilot-chutes? They may have a cone of fabric and a cone of mesh .. similar sizes, but there is an extra cylinder of mesh hanging out the bottom .... because of the extra-long spring. Hee! Hee! Quote Share this post Link to post Share on other sites rifleman 61 #10 March 24, 2014 Completely noob questions here - if the reserve pilot chute isn't extracting the reserve, wouldn't it be advisable to make the RPC slightly larger (say an extra 4" diameter)? Also are RPC's ZP or F-111? Which is more effective (I get that F-111 needs to be replaced more often than ZP but if it's more effective then surely it's worth the expense)? As I say, noob questions, but I'm just interested and the next time I'm at the DZ I'll probably be asking one of the riggers anyway.Atheism is a Non-Prophet Organisation Quote Share this post Link to post Share on other sites RiggerLee 61 #11 March 24, 2014 I honestly don't think f-111 or zp makes that big of a difference in pilot chutes. A PC is really crude. In some thing larger where it can affect the boundary and the separation point like a round parachute it can have a noticeable affect on the oscillation and CD. Reserve PC's have been made from both. I think the size and design are more relevant. And you're question is not a completely noob question. I've been doing this for 20 years and I would really like to know why I am not allowed to put a larger higher drag PC in my reserve. That's a bit of a dig but there has been some discussion about this but nothing has happened. The truth is I'm not sure how easily some of these things could be corrected. A larger PC would really be more of a stop gap measure. Not a bad one but still a band aid. It might be fun to go back and time some of those videos. If you could take a guess at the speed where the bag finally extracted you could make a pretty good estimate of how much larger the PC would have to be to extract the bag in time to meet the TSO requirements. I don't have time at the moment. A better solution might be to just use an off the shelf TSO'd PC from another manufacturer, larger with a higher CD, but although that is permitted by the FAA it is forbidden by the rig manufacturers. And yes I'm stirring the pot here a little bit but I'm board and need some entertainment. So that's where we stand. When you have a malfunction and you need to cut away, from a perfectly reasonable height from which the FAA says that you're reserve should open, it will in fact tow into the ground and you will be laying there broken open like a ripe tomato. Now scream and run around in circles pulling your hair out for our amusement. And start stretching so that you will have the flexibility to reach over your shoulder and grab the bridle. Because that's your new emergency procedure. Deploy PC, deploy bag. Pull red. Pull silver. Reach back, grab bridle. Deploy reserve. Some body send him the link to the hand deploy. Mean while I will go and make popcorn. LeeLee [email protected] www.velocitysportswear.com Quote Share this post Link to post Share on other sites councilman24 36 #12 March 25, 2014 RiggerLee We also have not heard any thing about the PC in tow/delay issues for some time. The question isn't going away. And if the gear can not meet the TSO standards, as proved in the videos (plural), then the TSO should be void till the problem is corrected. I think there are real questions about the legality of some of this gear being jumped and the legality and liability of packing it as a rigger. When you sign that card you're saying that the rig can still meet the standards of the TSO. Lee But the TSO standard is in no way a quality control standard either of manufacture, component assembly compatibility, packing, wear or any of the other things that can effect performance like body position (towing over the shoulder on your back). Its best described as a design confirmation program. There is a quality control manual required that assures some minimum consistency of articles. But the TSO program really asks CAN the test article(s) meet the required test standard, not WILL all individual items or all combinations. Doesn't mean that any individual article the will meet requirements either as tested and certainly not under conditions not tested. What isn't tested? Almost everything. Certainly most of the sizes and nearly all of the size combinations of rig and canopy are not tested. Neither is routing the PC bridle over your shoulder on your back. There was absolutely no reason for that PC to be expected to extract the bag. I would argue that a rigger is not certifying that the rig would pass the TSO standards even under perfect conditions. Almost certainly that combination wasn't tested, obviously that particular set wasn't tested, and probably not even those sizes of canopy and container individually were ever tested. We're certifying that we followed the instructions, that as best we know with the information provided by the manufacturers that this combination should work. BTW that information is very minimal. About ten years ago when writing PIA TS-135 the French government was that insisting rig manufacturers list ever reserve/size that could be put in a particular model rig. Even this wasn't practical or possible because of the "mystery bulk" issue. Or better said the volume variation (up to 10%) in both canopies and containers. One set of gear with the canopy at the small side and the container at the large side may fit fine. Those same models/sizes at the reversed ends of the ranges (small rig and big canopy) may not fit. Of course testing all the combinations is not even imaginable. Think about it. Only a couple of canopy sizes are tested, only a couple of containers, and if at all only one size combination at each end. You could almost be surprised when a rig does work.Is this what we want to know or believe? No. But it's reality. Should riggers say no to more of the rigs? Probably. Will the rigger down the road do it? Sure. Maybe you shouldn't have given that seminar on how to put 10 pounds of shit in a five pound bag..I'm old for my age. Terry Urban D-8631 FAA DPRE Quote Share this post Link to post Share on other sites JohnSherman 1 #13 March 25, 2014 QuoteRiggers - could you continue and complete the list with your estimates? - Racer: Racer : 50%-50% Open mesh (important) Here is a chart showing a summary of the Force vs. Dynamic Pressure (altitude & speed) of all know pilot chute tests. [inline Drag_Capabilities_of_Tested_pilot_chutes.jpg] Quote Share this post Link to post Share on other sites roostnureye 2 #14 March 25, 2014 JohnShermanQuoteRiggers - could you continue and complete the list with your estimates? - Racer: Racer : 50%-50% Open mesh (important) Here is a chart showing a summary of the Force vs. Dynamic Pressure (altitude & speed) of all know pilot chute tests. i didnt happen to see Vector 3 in that chart????Flock University FWC / ZFlock B.A.S.E. 1580 Aussie BASE 121 Quote Share this post Link to post Share on other sites pchapman 261 #15 March 25, 2014 roostnureye i didnt happen to see Vector 3 in that chart???? Same PC as a Vector II. Quote Share this post Link to post Share on other sites riggerrob 558 #16 March 26, 2014 Most reserve pilot chutes are made of F-111 fabric, while a few are made of ZP fabric. New F-111 fabric will pass zero to 3 cubic feet per minute of air, while new ZP fabric passes zero cfm. That makes for an insignificant difference in porosity and drag. At those porosities, the pilot chute configuration and number of needle holes make bigger differences. Porosity will only change after 40 or more pack jobs - roughly 20 years in service. By the time a pilot chute is 20 years old, many riggers will refuse to repack it. Quote Share this post Link to post Share on other sites riggerrob 558 #17 March 26, 2014 ... I would really like to know why I am not allowed to put a larger higher drag PC in my reserve. ... Lee ...................................................................................... If yo install a humungously, ginormous, over-sized reserve pilot-chute, it might create so much drag that it exceeds the ability of the safety-stow to hold the free-bag closed until line=stretch. Instead, it will jerk the free-bag off your back so quickly that you will suffer bag-strip, which will leave you still iin free-fall ... but without your free-bag and pilot-chute. The reserve canopy and lines will still be flopping about on your back. Sometime late, a side gust might push the reserve canopy off your back ... line stretch ... inflation ... etc. It is rumoured that this killed a Golden Knight about 30 years ago. That was back during the early days of square reserves. That accident motivated Para-Flite to invent Safety-stows (mid 1980s). Safety-stows are less likely to suffer bag-strip because their line stows are balanced. Quote Share this post Link to post Share on other sites RiggerLee 61 #18 March 26, 2014 In theory.... But I was referring to other TSO'd pilot chutes tested in the same speed regimes with equivalent deployment systems. Let's face it, every one, with the exception of Sherman, uses essentially the same safety stow deployment method. And there isn't that much difference in the speeds that the containers are TSO'd to. I think there is a good argument for compatibility. I think you could put a Mirage PC in a Vector 3. I think that with just a little work, minor change, snaps, Sandy could put a Stealth in a Wings. I do think that the fundamental problems in container design should them selves be addressed. But in the mean time I see no harm in upgrading our PC's. Because towing a PC into the ground is just not cool. LeeLee [email protected] www.velocitysportswear.com Quote Share this post Link to post Share on other sites JohnSherman 1 #19 March 26, 2014 QuoteIf yo install a humungously, ginormous, over-sized reserve pilot-chute, it might create so much drag that it exceeds the ability of the safety-stow to hold the free-bag closed until line=stretch. Instead, it will jerk the free-bag off your back so quickly that you will suffer bag-strip, which will leave you still iin free-fall ... but without your free-bag and pilot-chute. The reserve canopy and lines will still be flopping about on your back. Sometime late, a side gust might push the reserve canopy off your back ... line stretch ... inflation ... etc. It is rumoured that this killed a Golden Knight about 30 years ago. That was back during the early days of square reserves. That accident motivated Para-Flite to invent Safety-stows (mid 1980s). Safety-stows are less likely to suffer bag-strip because their line stows are balanced. No pilot chute will have enough snatch/drag to strip a bag off of a canopy if the bag is properly designed. The “Safety Stow” is not such a design. Any bag design must retain the canopy until the lines are extended in ALL CASES no mater how big or powerful the pilot chute is. A “Safety Stow” is a continuous loop of 1/8” Bunge cord folded in half and threaded into a channel grommeted on both ends. The loops exit the channel through the grommets at each end. This replaced the Buna-N “O” rings which were the root cause of the GK tragedy. This new design (the Safety Stow) provides no stiffener to hold the grommets in separation during line bight extraction and in practice is no better than the Buna-N “O” rings. This allows one stow to have an retention force of 12 pounds +/- and forces the other stow to have little or no retention force because the grommets are forced together during packing. Even though the stows are balanced they easily allow the loose stow to escape during bag extraction, especially at terminal. When one of two locking stows release on a “Safety Stow” bag it releases the canopy from the bag – “Line dump”. This is likely when using a Velcro pouch with only 12 square inches of Velcro is attempting to hold the mass of the entire length of lines in the pouch during extraction. This works well on low speed deployment but there is a vast amount of data which indicates a problem when this system is used at terminal. No manufacturer can prevent you from installing a better pilot chute, in a reserve, no matter what they say in their manual. They don’t have the authority to override the FAA permission granted in AC105. As long a there is no degradation of performance you may make the change if it is functionally compatible. Quote Share this post Link to post Share on other sites koppel 3 #20 March 26, 2014 JohnSherman. As long a there is no degradation of performance you may make the change if it is functionally compatible. How would one be expected to document this for the FAA?I like my canopy... ...it lets me down. Quote Share this post Link to post Share on other sites councilman24 36 #21 March 26, 2014 Drop tests. Impractical And if an incident the manufacturer will throw the rigger under the bus.I'm old for my age. Terry Urban D-8631 FAA DPRE Quote Share this post Link to post Share on other sites JohnSherman 1 #22 March 26, 2014 QuoteDrop tests. Impractical Drop test are no problem. I plan to do a bunch during PIA next year and I will use this procedure. Try it you will like it. Quote Share this post Link to post Share on other sites councilman24 36 #23 March 26, 2014 John, My answer was to was the feds would take as data that other than the OEM pilot chute would work in a rig.I'm old for my age. Terry Urban D-8631 FAA DPRE Quote Share this post Link to post Share on other sites JohnSherman 1 #24 March 27, 2014 QuoteMy answer was to was the feds would take as data that other than the OEM pilot chute would work in a rig. Terry, A presentation to the FAA with data collected from free drop test along with a demonstration of function and the feds would have to buy it as it would be correct. However, such a process is not necessary as a rigger has the authority granted in AC-105. But! That rigger had better be ready to present such data if the sky falls in, as they would be subject to severe pier and FAA review. This simple free drop test which I present works. It is sound engineering using traditional formulas. I present it for review to anyone who wishes to comment or question the procedure. Do the test I propose with the OEM pilot chute and the proposed pilot chute. Compare the data. If the results are satisfactory for justification of replacement then, document the tests and present it. While I say that such a presentation is not necessary there would be no harm in doing it in this case as it would validate the process. BTW: You must share the data here. Quote Share this post Link to post Share on other sites JerryBaumchen 1,047 #25 March 27, 2014 Hi John, QuoteIt is sound engineering using traditional formulas. You have this formula: Drag = Cd*So*Q Then you say: Cd is the Drag coefficient of the device. So is the Square footage of the device as shown in plan form. Q is the Dynamic pressure or 1/2 Rho V^2 V is the velocity in Feet per second. Where is V in the formula? JerryBaumchen Quote Share this post Link to post Share on other sites Prev 1 2 3 Next Page 1 of 3 Join the conversation You can post now and register later. If you have an account, sign in now to post with your account. Note: Your post will require moderator approval before it will be visible. Reply to this topic... × Pasted as rich text. Paste as plain text instead Only 75 emoji are allowed. × Your link has been automatically embedded. Display as a link instead × Your previous content has been restored. Clear editor × You cannot paste images directly. Upload or insert images from URL. Insert image from URL × Desktop Tablet Phone Submit Reply 0 Go To Topic Listing
skydiverek 54 #5 April 1, 2005 Some opinions which design is better can be found in this thread titled "Reserve Pilotchute: Meshless or with Partial Mesh?" here: http://www.dropzone.com/cgi-bin/forum/gforum.cgi?post=476690#476690 Quote Share this post Link to post Share on other sites RMURRAY 1 #6 March 23, 2014 what matters is the cd (or in the end, drag) not mesh vs non mesh. was there a design change on the rig that towed the reserve pc? if not I cannot understand how the sell any... or used ones are sold at any price...unless like bill b says skydivers do not care about safety. Quote Share this post Link to post Share on other sites dpreguy 14 #7 March 23, 2014 What would be the value of knowing these ratios? Quote Share this post Link to post Share on other sites RiggerLee 61 #8 March 23, 2014 Well if you're interested in design it's a very relevant question. But I don't think it's well defined. Are we talking surface area? Vent area? Diameters? And I think there are a lot of other factors. Is there any shape to the fabric or mesh. For instance I've built PC's with both shaped panels and conical mesh. If you want to make this a real discussion I think that would be cool. But if you're just trying to make an end run around bad mouthing particular manufacturers then I think it's pretty weak. I'd much rather you just came flat out and said, "Hay! What's up with these towed PC's? Why aren't there any upgrades or replacement higher drag versions available yet? I mean manufacturers have responded much faster in the past with SB and upgraded pilot chutes for much smaller problems or perceived problems and there weren't even fatalities involved. Is that the problem? Now that some one's dead you are afraid to correct the problem for fear of admitting liability? I'm not saying that that's the case. But if you want to talk about it, man up and say it. Don't pussy foot around the topic with some discussion about design. I can go ether way on this. We haven't had a fun design question in a while. We also have not heard any thing about the PC in tow/delay issues for some time. The question isn't going away. And if the gear can not meet the TSO standards, as proved in the videos (plural), then the TSO should be void till the problem is corrected. I think there are real questions about the legality of some of this gear being jumped and the legality and liability of packing it as a rigger. When you sign that card you're saying that the rig can still meet the standards of the TSO. Pick a topic. Game on. LeeLee [email protected] www.velocitysportswear.com Quote Share this post Link to post Share on other sites riggerrob 558 #9 March 24, 2014 Mischevious .... How do you count Magnum pilot-chutes? They may have a cone of fabric and a cone of mesh .. similar sizes, but there is an extra cylinder of mesh hanging out the bottom .... because of the extra-long spring. Hee! Hee! Quote Share this post Link to post Share on other sites rifleman 61 #10 March 24, 2014 Completely noob questions here - if the reserve pilot chute isn't extracting the reserve, wouldn't it be advisable to make the RPC slightly larger (say an extra 4" diameter)? Also are RPC's ZP or F-111? Which is more effective (I get that F-111 needs to be replaced more often than ZP but if it's more effective then surely it's worth the expense)? As I say, noob questions, but I'm just interested and the next time I'm at the DZ I'll probably be asking one of the riggers anyway.Atheism is a Non-Prophet Organisation Quote Share this post Link to post Share on other sites RiggerLee 61 #11 March 24, 2014 I honestly don't think f-111 or zp makes that big of a difference in pilot chutes. A PC is really crude. In some thing larger where it can affect the boundary and the separation point like a round parachute it can have a noticeable affect on the oscillation and CD. Reserve PC's have been made from both. I think the size and design are more relevant. And you're question is not a completely noob question. I've been doing this for 20 years and I would really like to know why I am not allowed to put a larger higher drag PC in my reserve. That's a bit of a dig but there has been some discussion about this but nothing has happened. The truth is I'm not sure how easily some of these things could be corrected. A larger PC would really be more of a stop gap measure. Not a bad one but still a band aid. It might be fun to go back and time some of those videos. If you could take a guess at the speed where the bag finally extracted you could make a pretty good estimate of how much larger the PC would have to be to extract the bag in time to meet the TSO requirements. I don't have time at the moment. A better solution might be to just use an off the shelf TSO'd PC from another manufacturer, larger with a higher CD, but although that is permitted by the FAA it is forbidden by the rig manufacturers. And yes I'm stirring the pot here a little bit but I'm board and need some entertainment. So that's where we stand. When you have a malfunction and you need to cut away, from a perfectly reasonable height from which the FAA says that you're reserve should open, it will in fact tow into the ground and you will be laying there broken open like a ripe tomato. Now scream and run around in circles pulling your hair out for our amusement. And start stretching so that you will have the flexibility to reach over your shoulder and grab the bridle. Because that's your new emergency procedure. Deploy PC, deploy bag. Pull red. Pull silver. Reach back, grab bridle. Deploy reserve. Some body send him the link to the hand deploy. Mean while I will go and make popcorn. LeeLee [email protected] www.velocitysportswear.com Quote Share this post Link to post Share on other sites councilman24 36 #12 March 25, 2014 RiggerLee We also have not heard any thing about the PC in tow/delay issues for some time. The question isn't going away. And if the gear can not meet the TSO standards, as proved in the videos (plural), then the TSO should be void till the problem is corrected. I think there are real questions about the legality of some of this gear being jumped and the legality and liability of packing it as a rigger. When you sign that card you're saying that the rig can still meet the standards of the TSO. Lee But the TSO standard is in no way a quality control standard either of manufacture, component assembly compatibility, packing, wear or any of the other things that can effect performance like body position (towing over the shoulder on your back). Its best described as a design confirmation program. There is a quality control manual required that assures some minimum consistency of articles. But the TSO program really asks CAN the test article(s) meet the required test standard, not WILL all individual items or all combinations. Doesn't mean that any individual article the will meet requirements either as tested and certainly not under conditions not tested. What isn't tested? Almost everything. Certainly most of the sizes and nearly all of the size combinations of rig and canopy are not tested. Neither is routing the PC bridle over your shoulder on your back. There was absolutely no reason for that PC to be expected to extract the bag. I would argue that a rigger is not certifying that the rig would pass the TSO standards even under perfect conditions. Almost certainly that combination wasn't tested, obviously that particular set wasn't tested, and probably not even those sizes of canopy and container individually were ever tested. We're certifying that we followed the instructions, that as best we know with the information provided by the manufacturers that this combination should work. BTW that information is very minimal. About ten years ago when writing PIA TS-135 the French government was that insisting rig manufacturers list ever reserve/size that could be put in a particular model rig. Even this wasn't practical or possible because of the "mystery bulk" issue. Or better said the volume variation (up to 10%) in both canopies and containers. One set of gear with the canopy at the small side and the container at the large side may fit fine. Those same models/sizes at the reversed ends of the ranges (small rig and big canopy) may not fit. Of course testing all the combinations is not even imaginable. Think about it. Only a couple of canopy sizes are tested, only a couple of containers, and if at all only one size combination at each end. You could almost be surprised when a rig does work.Is this what we want to know or believe? No. But it's reality. Should riggers say no to more of the rigs? Probably. Will the rigger down the road do it? Sure. Maybe you shouldn't have given that seminar on how to put 10 pounds of shit in a five pound bag..I'm old for my age. Terry Urban D-8631 FAA DPRE Quote Share this post Link to post Share on other sites JohnSherman 1 #13 March 25, 2014 QuoteRiggers - could you continue and complete the list with your estimates? - Racer: Racer : 50%-50% Open mesh (important) Here is a chart showing a summary of the Force vs. Dynamic Pressure (altitude & speed) of all know pilot chute tests. [inline Drag_Capabilities_of_Tested_pilot_chutes.jpg] Quote Share this post Link to post Share on other sites roostnureye 2 #14 March 25, 2014 JohnShermanQuoteRiggers - could you continue and complete the list with your estimates? - Racer: Racer : 50%-50% Open mesh (important) Here is a chart showing a summary of the Force vs. Dynamic Pressure (altitude & speed) of all know pilot chute tests. i didnt happen to see Vector 3 in that chart????Flock University FWC / ZFlock B.A.S.E. 1580 Aussie BASE 121 Quote Share this post Link to post Share on other sites pchapman 261 #15 March 25, 2014 roostnureye i didnt happen to see Vector 3 in that chart???? Same PC as a Vector II. Quote Share this post Link to post Share on other sites riggerrob 558 #16 March 26, 2014 Most reserve pilot chutes are made of F-111 fabric, while a few are made of ZP fabric. New F-111 fabric will pass zero to 3 cubic feet per minute of air, while new ZP fabric passes zero cfm. That makes for an insignificant difference in porosity and drag. At those porosities, the pilot chute configuration and number of needle holes make bigger differences. Porosity will only change after 40 or more pack jobs - roughly 20 years in service. By the time a pilot chute is 20 years old, many riggers will refuse to repack it. Quote Share this post Link to post Share on other sites riggerrob 558 #17 March 26, 2014 ... I would really like to know why I am not allowed to put a larger higher drag PC in my reserve. ... Lee ...................................................................................... If yo install a humungously, ginormous, over-sized reserve pilot-chute, it might create so much drag that it exceeds the ability of the safety-stow to hold the free-bag closed until line=stretch. Instead, it will jerk the free-bag off your back so quickly that you will suffer bag-strip, which will leave you still iin free-fall ... but without your free-bag and pilot-chute. The reserve canopy and lines will still be flopping about on your back. Sometime late, a side gust might push the reserve canopy off your back ... line stretch ... inflation ... etc. It is rumoured that this killed a Golden Knight about 30 years ago. That was back during the early days of square reserves. That accident motivated Para-Flite to invent Safety-stows (mid 1980s). Safety-stows are less likely to suffer bag-strip because their line stows are balanced. Quote Share this post Link to post Share on other sites RiggerLee 61 #18 March 26, 2014 In theory.... But I was referring to other TSO'd pilot chutes tested in the same speed regimes with equivalent deployment systems. Let's face it, every one, with the exception of Sherman, uses essentially the same safety stow deployment method. And there isn't that much difference in the speeds that the containers are TSO'd to. I think there is a good argument for compatibility. I think you could put a Mirage PC in a Vector 3. I think that with just a little work, minor change, snaps, Sandy could put a Stealth in a Wings. I do think that the fundamental problems in container design should them selves be addressed. But in the mean time I see no harm in upgrading our PC's. Because towing a PC into the ground is just not cool. LeeLee [email protected] www.velocitysportswear.com Quote Share this post Link to post Share on other sites JohnSherman 1 #19 March 26, 2014 QuoteIf yo install a humungously, ginormous, over-sized reserve pilot-chute, it might create so much drag that it exceeds the ability of the safety-stow to hold the free-bag closed until line=stretch. Instead, it will jerk the free-bag off your back so quickly that you will suffer bag-strip, which will leave you still iin free-fall ... but without your free-bag and pilot-chute. The reserve canopy and lines will still be flopping about on your back. Sometime late, a side gust might push the reserve canopy off your back ... line stretch ... inflation ... etc. It is rumoured that this killed a Golden Knight about 30 years ago. That was back during the early days of square reserves. That accident motivated Para-Flite to invent Safety-stows (mid 1980s). Safety-stows are less likely to suffer bag-strip because their line stows are balanced. No pilot chute will have enough snatch/drag to strip a bag off of a canopy if the bag is properly designed. The “Safety Stow” is not such a design. Any bag design must retain the canopy until the lines are extended in ALL CASES no mater how big or powerful the pilot chute is. A “Safety Stow” is a continuous loop of 1/8” Bunge cord folded in half and threaded into a channel grommeted on both ends. The loops exit the channel through the grommets at each end. This replaced the Buna-N “O” rings which were the root cause of the GK tragedy. This new design (the Safety Stow) provides no stiffener to hold the grommets in separation during line bight extraction and in practice is no better than the Buna-N “O” rings. This allows one stow to have an retention force of 12 pounds +/- and forces the other stow to have little or no retention force because the grommets are forced together during packing. Even though the stows are balanced they easily allow the loose stow to escape during bag extraction, especially at terminal. When one of two locking stows release on a “Safety Stow” bag it releases the canopy from the bag – “Line dump”. This is likely when using a Velcro pouch with only 12 square inches of Velcro is attempting to hold the mass of the entire length of lines in the pouch during extraction. This works well on low speed deployment but there is a vast amount of data which indicates a problem when this system is used at terminal. No manufacturer can prevent you from installing a better pilot chute, in a reserve, no matter what they say in their manual. They don’t have the authority to override the FAA permission granted in AC105. As long a there is no degradation of performance you may make the change if it is functionally compatible. Quote Share this post Link to post Share on other sites koppel 3 #20 March 26, 2014 JohnSherman. As long a there is no degradation of performance you may make the change if it is functionally compatible. How would one be expected to document this for the FAA?I like my canopy... ...it lets me down. Quote Share this post Link to post Share on other sites councilman24 36 #21 March 26, 2014 Drop tests. Impractical And if an incident the manufacturer will throw the rigger under the bus.I'm old for my age. Terry Urban D-8631 FAA DPRE Quote Share this post Link to post Share on other sites JohnSherman 1 #22 March 26, 2014 QuoteDrop tests. Impractical Drop test are no problem. I plan to do a bunch during PIA next year and I will use this procedure. Try it you will like it. Quote Share this post Link to post Share on other sites councilman24 36 #23 March 26, 2014 John, My answer was to was the feds would take as data that other than the OEM pilot chute would work in a rig.I'm old for my age. Terry Urban D-8631 FAA DPRE Quote Share this post Link to post Share on other sites JohnSherman 1 #24 March 27, 2014 QuoteMy answer was to was the feds would take as data that other than the OEM pilot chute would work in a rig. Terry, A presentation to the FAA with data collected from free drop test along with a demonstration of function and the feds would have to buy it as it would be correct. However, such a process is not necessary as a rigger has the authority granted in AC-105. But! That rigger had better be ready to present such data if the sky falls in, as they would be subject to severe pier and FAA review. This simple free drop test which I present works. It is sound engineering using traditional formulas. I present it for review to anyone who wishes to comment or question the procedure. Do the test I propose with the OEM pilot chute and the proposed pilot chute. Compare the data. If the results are satisfactory for justification of replacement then, document the tests and present it. While I say that such a presentation is not necessary there would be no harm in doing it in this case as it would validate the process. BTW: You must share the data here. Quote Share this post Link to post Share on other sites JerryBaumchen 1,047 #25 March 27, 2014 Hi John, QuoteIt is sound engineering using traditional formulas. You have this formula: Drag = Cd*So*Q Then you say: Cd is the Drag coefficient of the device. So is the Square footage of the device as shown in plan form. Q is the Dynamic pressure or 1/2 Rho V^2 V is the velocity in Feet per second. Where is V in the formula? JerryBaumchen Quote Share this post Link to post Share on other sites Prev 1 2 3 Next Page 1 of 3 Join the conversation You can post now and register later. If you have an account, sign in now to post with your account. Note: Your post will require moderator approval before it will be visible. Reply to this topic... × Pasted as rich text. Paste as plain text instead Only 75 emoji are allowed. × Your link has been automatically embedded. Display as a link instead × Your previous content has been restored. Clear editor × You cannot paste images directly. Upload or insert images from URL. Insert image from URL × Desktop Tablet Phone Submit Reply 0
RMURRAY 1 #6 March 23, 2014 what matters is the cd (or in the end, drag) not mesh vs non mesh. was there a design change on the rig that towed the reserve pc? if not I cannot understand how the sell any... or used ones are sold at any price...unless like bill b says skydivers do not care about safety. Quote Share this post Link to post Share on other sites
dpreguy 14 #7 March 23, 2014 What would be the value of knowing these ratios? Quote Share this post Link to post Share on other sites
RiggerLee 61 #8 March 23, 2014 Well if you're interested in design it's a very relevant question. But I don't think it's well defined. Are we talking surface area? Vent area? Diameters? And I think there are a lot of other factors. Is there any shape to the fabric or mesh. For instance I've built PC's with both shaped panels and conical mesh. If you want to make this a real discussion I think that would be cool. But if you're just trying to make an end run around bad mouthing particular manufacturers then I think it's pretty weak. I'd much rather you just came flat out and said, "Hay! What's up with these towed PC's? Why aren't there any upgrades or replacement higher drag versions available yet? I mean manufacturers have responded much faster in the past with SB and upgraded pilot chutes for much smaller problems or perceived problems and there weren't even fatalities involved. Is that the problem? Now that some one's dead you are afraid to correct the problem for fear of admitting liability? I'm not saying that that's the case. But if you want to talk about it, man up and say it. Don't pussy foot around the topic with some discussion about design. I can go ether way on this. We haven't had a fun design question in a while. We also have not heard any thing about the PC in tow/delay issues for some time. The question isn't going away. And if the gear can not meet the TSO standards, as proved in the videos (plural), then the TSO should be void till the problem is corrected. I think there are real questions about the legality of some of this gear being jumped and the legality and liability of packing it as a rigger. When you sign that card you're saying that the rig can still meet the standards of the TSO. Pick a topic. Game on. LeeLee [email protected] www.velocitysportswear.com Quote Share this post Link to post Share on other sites
riggerrob 558 #9 March 24, 2014 Mischevious .... How do you count Magnum pilot-chutes? They may have a cone of fabric and a cone of mesh .. similar sizes, but there is an extra cylinder of mesh hanging out the bottom .... because of the extra-long spring. Hee! Hee! Quote Share this post Link to post Share on other sites
rifleman 61 #10 March 24, 2014 Completely noob questions here - if the reserve pilot chute isn't extracting the reserve, wouldn't it be advisable to make the RPC slightly larger (say an extra 4" diameter)? Also are RPC's ZP or F-111? Which is more effective (I get that F-111 needs to be replaced more often than ZP but if it's more effective then surely it's worth the expense)? As I say, noob questions, but I'm just interested and the next time I'm at the DZ I'll probably be asking one of the riggers anyway.Atheism is a Non-Prophet Organisation Quote Share this post Link to post Share on other sites
RiggerLee 61 #11 March 24, 2014 I honestly don't think f-111 or zp makes that big of a difference in pilot chutes. A PC is really crude. In some thing larger where it can affect the boundary and the separation point like a round parachute it can have a noticeable affect on the oscillation and CD. Reserve PC's have been made from both. I think the size and design are more relevant. And you're question is not a completely noob question. I've been doing this for 20 years and I would really like to know why I am not allowed to put a larger higher drag PC in my reserve. That's a bit of a dig but there has been some discussion about this but nothing has happened. The truth is I'm not sure how easily some of these things could be corrected. A larger PC would really be more of a stop gap measure. Not a bad one but still a band aid. It might be fun to go back and time some of those videos. If you could take a guess at the speed where the bag finally extracted you could make a pretty good estimate of how much larger the PC would have to be to extract the bag in time to meet the TSO requirements. I don't have time at the moment. A better solution might be to just use an off the shelf TSO'd PC from another manufacturer, larger with a higher CD, but although that is permitted by the FAA it is forbidden by the rig manufacturers. And yes I'm stirring the pot here a little bit but I'm board and need some entertainment. So that's where we stand. When you have a malfunction and you need to cut away, from a perfectly reasonable height from which the FAA says that you're reserve should open, it will in fact tow into the ground and you will be laying there broken open like a ripe tomato. Now scream and run around in circles pulling your hair out for our amusement. And start stretching so that you will have the flexibility to reach over your shoulder and grab the bridle. Because that's your new emergency procedure. Deploy PC, deploy bag. Pull red. Pull silver. Reach back, grab bridle. Deploy reserve. Some body send him the link to the hand deploy. Mean while I will go and make popcorn. LeeLee [email protected] www.velocitysportswear.com Quote Share this post Link to post Share on other sites
councilman24 36 #12 March 25, 2014 RiggerLee We also have not heard any thing about the PC in tow/delay issues for some time. The question isn't going away. And if the gear can not meet the TSO standards, as proved in the videos (plural), then the TSO should be void till the problem is corrected. I think there are real questions about the legality of some of this gear being jumped and the legality and liability of packing it as a rigger. When you sign that card you're saying that the rig can still meet the standards of the TSO. Lee But the TSO standard is in no way a quality control standard either of manufacture, component assembly compatibility, packing, wear or any of the other things that can effect performance like body position (towing over the shoulder on your back). Its best described as a design confirmation program. There is a quality control manual required that assures some minimum consistency of articles. But the TSO program really asks CAN the test article(s) meet the required test standard, not WILL all individual items or all combinations. Doesn't mean that any individual article the will meet requirements either as tested and certainly not under conditions not tested. What isn't tested? Almost everything. Certainly most of the sizes and nearly all of the size combinations of rig and canopy are not tested. Neither is routing the PC bridle over your shoulder on your back. There was absolutely no reason for that PC to be expected to extract the bag. I would argue that a rigger is not certifying that the rig would pass the TSO standards even under perfect conditions. Almost certainly that combination wasn't tested, obviously that particular set wasn't tested, and probably not even those sizes of canopy and container individually were ever tested. We're certifying that we followed the instructions, that as best we know with the information provided by the manufacturers that this combination should work. BTW that information is very minimal. About ten years ago when writing PIA TS-135 the French government was that insisting rig manufacturers list ever reserve/size that could be put in a particular model rig. Even this wasn't practical or possible because of the "mystery bulk" issue. Or better said the volume variation (up to 10%) in both canopies and containers. One set of gear with the canopy at the small side and the container at the large side may fit fine. Those same models/sizes at the reversed ends of the ranges (small rig and big canopy) may not fit. Of course testing all the combinations is not even imaginable. Think about it. Only a couple of canopy sizes are tested, only a couple of containers, and if at all only one size combination at each end. You could almost be surprised when a rig does work.Is this what we want to know or believe? No. But it's reality. Should riggers say no to more of the rigs? Probably. Will the rigger down the road do it? Sure. Maybe you shouldn't have given that seminar on how to put 10 pounds of shit in a five pound bag..I'm old for my age. Terry Urban D-8631 FAA DPRE Quote Share this post Link to post Share on other sites
JohnSherman 1 #13 March 25, 2014 QuoteRiggers - could you continue and complete the list with your estimates? - Racer: Racer : 50%-50% Open mesh (important) Here is a chart showing a summary of the Force vs. Dynamic Pressure (altitude & speed) of all know pilot chute tests. [inline Drag_Capabilities_of_Tested_pilot_chutes.jpg] Quote Share this post Link to post Share on other sites
roostnureye 2 #14 March 25, 2014 JohnShermanQuoteRiggers - could you continue and complete the list with your estimates? - Racer: Racer : 50%-50% Open mesh (important) Here is a chart showing a summary of the Force vs. Dynamic Pressure (altitude & speed) of all know pilot chute tests. i didnt happen to see Vector 3 in that chart????Flock University FWC / ZFlock B.A.S.E. 1580 Aussie BASE 121 Quote Share this post Link to post Share on other sites
pchapman 261 #15 March 25, 2014 roostnureye i didnt happen to see Vector 3 in that chart???? Same PC as a Vector II. Quote Share this post Link to post Share on other sites
riggerrob 558 #16 March 26, 2014 Most reserve pilot chutes are made of F-111 fabric, while a few are made of ZP fabric. New F-111 fabric will pass zero to 3 cubic feet per minute of air, while new ZP fabric passes zero cfm. That makes for an insignificant difference in porosity and drag. At those porosities, the pilot chute configuration and number of needle holes make bigger differences. Porosity will only change after 40 or more pack jobs - roughly 20 years in service. By the time a pilot chute is 20 years old, many riggers will refuse to repack it. Quote Share this post Link to post Share on other sites
riggerrob 558 #17 March 26, 2014 ... I would really like to know why I am not allowed to put a larger higher drag PC in my reserve. ... Lee ...................................................................................... If yo install a humungously, ginormous, over-sized reserve pilot-chute, it might create so much drag that it exceeds the ability of the safety-stow to hold the free-bag closed until line=stretch. Instead, it will jerk the free-bag off your back so quickly that you will suffer bag-strip, which will leave you still iin free-fall ... but without your free-bag and pilot-chute. The reserve canopy and lines will still be flopping about on your back. Sometime late, a side gust might push the reserve canopy off your back ... line stretch ... inflation ... etc. It is rumoured that this killed a Golden Knight about 30 years ago. That was back during the early days of square reserves. That accident motivated Para-Flite to invent Safety-stows (mid 1980s). Safety-stows are less likely to suffer bag-strip because their line stows are balanced. Quote Share this post Link to post Share on other sites
RiggerLee 61 #18 March 26, 2014 In theory.... But I was referring to other TSO'd pilot chutes tested in the same speed regimes with equivalent deployment systems. Let's face it, every one, with the exception of Sherman, uses essentially the same safety stow deployment method. And there isn't that much difference in the speeds that the containers are TSO'd to. I think there is a good argument for compatibility. I think you could put a Mirage PC in a Vector 3. I think that with just a little work, minor change, snaps, Sandy could put a Stealth in a Wings. I do think that the fundamental problems in container design should them selves be addressed. But in the mean time I see no harm in upgrading our PC's. Because towing a PC into the ground is just not cool. LeeLee [email protected] www.velocitysportswear.com Quote Share this post Link to post Share on other sites
JohnSherman 1 #19 March 26, 2014 QuoteIf yo install a humungously, ginormous, over-sized reserve pilot-chute, it might create so much drag that it exceeds the ability of the safety-stow to hold the free-bag closed until line=stretch. Instead, it will jerk the free-bag off your back so quickly that you will suffer bag-strip, which will leave you still iin free-fall ... but without your free-bag and pilot-chute. The reserve canopy and lines will still be flopping about on your back. Sometime late, a side gust might push the reserve canopy off your back ... line stretch ... inflation ... etc. It is rumoured that this killed a Golden Knight about 30 years ago. That was back during the early days of square reserves. That accident motivated Para-Flite to invent Safety-stows (mid 1980s). Safety-stows are less likely to suffer bag-strip because their line stows are balanced. No pilot chute will have enough snatch/drag to strip a bag off of a canopy if the bag is properly designed. The “Safety Stow” is not such a design. Any bag design must retain the canopy until the lines are extended in ALL CASES no mater how big or powerful the pilot chute is. A “Safety Stow” is a continuous loop of 1/8” Bunge cord folded in half and threaded into a channel grommeted on both ends. The loops exit the channel through the grommets at each end. This replaced the Buna-N “O” rings which were the root cause of the GK tragedy. This new design (the Safety Stow) provides no stiffener to hold the grommets in separation during line bight extraction and in practice is no better than the Buna-N “O” rings. This allows one stow to have an retention force of 12 pounds +/- and forces the other stow to have little or no retention force because the grommets are forced together during packing. Even though the stows are balanced they easily allow the loose stow to escape during bag extraction, especially at terminal. When one of two locking stows release on a “Safety Stow” bag it releases the canopy from the bag – “Line dump”. This is likely when using a Velcro pouch with only 12 square inches of Velcro is attempting to hold the mass of the entire length of lines in the pouch during extraction. This works well on low speed deployment but there is a vast amount of data which indicates a problem when this system is used at terminal. No manufacturer can prevent you from installing a better pilot chute, in a reserve, no matter what they say in their manual. They don’t have the authority to override the FAA permission granted in AC105. As long a there is no degradation of performance you may make the change if it is functionally compatible. Quote Share this post Link to post Share on other sites
koppel 3 #20 March 26, 2014 JohnSherman. As long a there is no degradation of performance you may make the change if it is functionally compatible. How would one be expected to document this for the FAA?I like my canopy... ...it lets me down. Quote Share this post Link to post Share on other sites
councilman24 36 #21 March 26, 2014 Drop tests. Impractical And if an incident the manufacturer will throw the rigger under the bus.I'm old for my age. Terry Urban D-8631 FAA DPRE Quote Share this post Link to post Share on other sites
JohnSherman 1 #22 March 26, 2014 QuoteDrop tests. Impractical Drop test are no problem. I plan to do a bunch during PIA next year and I will use this procedure. Try it you will like it. Quote Share this post Link to post Share on other sites
councilman24 36 #23 March 26, 2014 John, My answer was to was the feds would take as data that other than the OEM pilot chute would work in a rig.I'm old for my age. Terry Urban D-8631 FAA DPRE Quote Share this post Link to post Share on other sites
JohnSherman 1 #24 March 27, 2014 QuoteMy answer was to was the feds would take as data that other than the OEM pilot chute would work in a rig. Terry, A presentation to the FAA with data collected from free drop test along with a demonstration of function and the feds would have to buy it as it would be correct. However, such a process is not necessary as a rigger has the authority granted in AC-105. But! That rigger had better be ready to present such data if the sky falls in, as they would be subject to severe pier and FAA review. This simple free drop test which I present works. It is sound engineering using traditional formulas. I present it for review to anyone who wishes to comment or question the procedure. Do the test I propose with the OEM pilot chute and the proposed pilot chute. Compare the data. If the results are satisfactory for justification of replacement then, document the tests and present it. While I say that such a presentation is not necessary there would be no harm in doing it in this case as it would validate the process. BTW: You must share the data here. Quote Share this post Link to post Share on other sites
JerryBaumchen 1,047 #25 March 27, 2014 Hi John, QuoteIt is sound engineering using traditional formulas. You have this formula: Drag = Cd*So*Q Then you say: Cd is the Drag coefficient of the device. So is the Square footage of the device as shown in plan form. Q is the Dynamic pressure or 1/2 Rho V^2 V is the velocity in Feet per second. Where is V in the formula? JerryBaumchen Quote Share this post Link to post Share on other sites
