JohnSherman 1 #26 June 21, 2011 Peter, You are mostly correct. However, Force is the only parameter needed to decide about strength compatibility. In fact it is the only way this compatibility can be determined. The Weight and Speed give you the force. We only need to placard weight limitations for the purpose of landing softly. If the TSO Standard specifies a force load such as the "Standard Category" (5000) in C23b then there is no need to be concerned about performance limitations. If the force certified to is less than 5000 pounds then a Speed limitation is certainly required. The problem is this. The manufactures are cheap and lazy. It is much easier to test to a weight and speed than it is to measure force on a heavy drop. While I have never had a heavy drop failure of a parachute in 100's of tests. I have had a bunch where I got no data. Instrumentation is a B@$&#^. Wires break or get cut, batteries get loose for a fraction of a second and no data. I even had one land in a 25 foot diameter pond full of white milky liquid. I dropped drawers and jumped in to try to save the instruments. No luck. I can't tell you how many times someone forgot to turn it on. And on & on. When c23d (the current standard in effect) was written we required that a force level be placarded for the purpose of compatibility determination. TSO C23c is another matter. It has only weight and speed and is compatible with only the components tested. According to AC-105-2d force levels achieved when tested must be provided to the assembling rigger so he may determines strength compatibility. Listen to the Bitching from the manufacturers. “We will have to recertify” and so on and so on. This is hype. The science exists where a normal skydive can be made and the opening force measured. This is much easier today especially with a live jumper. We do it on a regular basis. This data can then be extrapolated to the weight and speed of certification. This process should be done several times to assure repeatability and accuracy. There are also other ways that I won’t expound on here. I just can’t imagine a manufacturer doing a heavy drop without trying to measure the force. I would consider it irresponsible. Quote Share this post Link to post Share on other sites
JerryBaumchen 1,048 #27 June 21, 2011 Hi Peter, Some 'trivia' for this discussion. Back in 1981 I was working in the Denver, CO quite a lot. One afternoon, I had some time to kill so I called Troy Loney up & went out and spent a couple of hours 'bs'ing' with him. He was a 1-man operation &, ~ the late '70's, he had obtained a TSO for his Centaurus rig. During his TSO testing he was able to convince the FAA to allow him to do the Strength Tests in a test machine rather than via actual drop tests. He took his harness to the 5,000 lb value, held it there for ~ 5 seconds, reduced the load to zero and did it all over again, three times. The FAA then accepted this as being in compliance with the Strength Test req'ment for his TSO application. What I see by this is that while we do not get the 'hoped for' 5,000 lb load test when following the chart in NAS 804 & using a C-9 canopy, we can be somewhat assured that a properly designed harness will actually hold the 5,000 lb loads. PIA TS-135 ( I have a copy of one version but am not sure that it is the version that the FAA used in their now-defunct TSO C23e ) has this: Section 4.3.6.3 STRENGTH TEST, ADDITIONAL MEANS OF COMPLIANCE HARNESS (ONLY) A harness may, at the manufacturer's option, be placarded with a higher average peak opening force than what was measured in 4.3.6 tests by performing additional tower drop tests as outlined below: It then goes on to specify the conditions for this testing. I think this excellent as it allows us to design & certificate a harness to far more than the canopies that will be attached to it. And this is why I wish that the FAA would allow this type of testing for the older ( TSO C23b & C23c ) harnesses so that they could then be placarded at some value that is known. As I said, just some fuel for the fire, JerryBaumchen PS) And for the record, I do not consider myself any type of expert in these matters. I probably know just enough to get myself into trouble. PPS) Back in 1979, when I approached the Seattle ACO about being allowed to do the Strength Tests in a test machine, as Troy had done, they would have nothing to do with it. Quote Share this post Link to post Share on other sites
masterrigger1 2 #28 June 21, 2011 Quote While I have never had a heavy drop failure of a parachute in 100's of tests. ...Maybe not on a single harness, dual container system, but we did on your Tandem system. We first pulled the reserve risers out of the harness. When we got that fixed by using Type 13 and multiple confluence wraps, we started blowing the center cells out. Of course this was when we were dropping the 525(?) ZP reserve. Probably 1992ish... Made for good video though. The last failure got us kicked off of the Elijay Airport when Elmo and your Navy rubber dummy landed in the woods right by someone's house!!!...... Sorry for the drift, MELSkyworks Parachute Service, LLC www.Skyworksparachuteservice.com Quote Share this post Link to post Share on other sites
RiggerLee 61 #29 June 22, 2011 This is actually a very interesting descusion but I have issues with some of the arguments being used. The phantom story has been around for a long time. I remember when Bland had his teath in it trying to get the FAA to make National retest them. No body wanted to hear about it at the time. I remember talking to him about it when it happoned. Just to clarify in case others don't understand what you mean by spitting I'll try to explaine. A lot of the mass of the canopy is in the lines on the diaper. At high snatch forces the tape that the diaper is sewn to runs over the top of the canopy through the crown lines and acts as a pully. If the Apex hole is larg enough it can pull the tape on the number one gore out of the fold in the canopy inside the diaper. Pops right out. Try it the next time you pack an Achudo style diaper like the National. As I recall, please corect me if my memory is off, all the lines pealed off the radial tape at the skirt and then the last one, the one on the diaper, poped at the finger trap down at the link. I read this as the center gore pulling out of the diaper, inflating (probably inverted), and pealing one line after another off the canopy all the way around till the last line broke exactly where you would expect at the finger trap. This is why I think all diapers should be on a heavier tape that runs up and formes a loop to the pilot chute. Think C-9 with a quarter bag. So there is no Pully effect caused by the mass of the lines. PS. I've blown up canopies this way my self. Been there, done that learning curve. I see this diffrently. I see this this as an example of a design defect. One that can cause aberant hard openings. It's not really a probblem of conpatability between TSO's. It's a fundomental failure of the testing requirments to catch a flaw. Why? Because it doesn't happen every time. Your not required to do that many high speed drops. I don't recall the exact number you have to pass, if some body can help me out? But the point is you can get lucky. You can squeak through with a design that could and probably should blow up on you. It should have failed the TSO C23b testing but it didn't. That's my opionion. It should have ben caught right there but it squeaked through. This is also an interesting subjet but it's not relevent to the thread. It didn't break the harness as I recall, it just blow it self up. Totally irrelevent to which TSO. And for thouse of you saying that phantoms are irrelevent, can you say Raven M? I'm not trying to throw stones here but it's a perfect example of a modern skydiving canopy that can have aberant hard openings. And it can knock the snot out of you. Yes they had attachment point problems but the core issue is that it can from time to time slam the shit out of you, which led to the line problem. Again no deffenition of compatability will help you here. It's inadiquite testing. And even then the harnesses seem to do a pritty good job of surviving. This is going to cause unholy hell if we try to follow it. I question whether it's worth it. I've seen harness damage, but how many total harness failures can we count? I seem to recall a racer loseing one side of a chest strap but I'd catagorize that as an extream asymetric opening. I don't hold it against you. And I don't think the ability to with stand high symetric loads on opening would save you from that. It's not speed or the weight of the opening that does that but how it opened. And I'll bet that I could tear any rig apart like that. In point of fact I've never personally seen a harness tear apart and drop some one to their death, but I have seen or know personally of several people that seem to have died of hard openings, torn aortas, or are paralized. Harnesses didn't fail. They died in them. All mains by the way but you see so many more main openings... Bottom line is I don't think this is what we need to be worrying about. LeeLee [email protected] www.velocitysportswear.com Quote Share this post Link to post Share on other sites
JohnSherman 1 #30 June 22, 2011 How come this was never reported to us? I have asked my staff members and no one knows about it. First of all the risers are an intergral/continous part of the main lift web and diagonal back strap. Your discription defies that construction. Additionally If you found such a condition the FAA requires an M&D report. Did you file one? We certainly never recieved one. That canopy (525ZP)did open hard, no question, but to open that hard would require line dump, a result of bad packing or deficient rubber bands. I'd love to see a copy of the video. Quote Share this post Link to post Share on other sites
masterrigger1 2 #31 June 22, 2011 Quote How come this was never reported to us? I have asked my staff members and no one knows about it. First of all the risers are an intergral/continous part of the main lift web and diagonal back strap. Your discription defies that construction. Additionally If you found such a condition the FAA requires an M&D report. Did you file one? We certainly never recieved one. That canopy (525ZP)did open hard, no question, but to open that hard would require line dump, a result of bad packing or deficient rubber bands. John, They all were reported to you after the test drops. Danny Page was working for you then. I was working with Danny Page , Red Payne, and also Chris Gay. This was also when we combined testing of the canopy, H/C, and the small reserve pilot chute. Quote I'd love to see a copy of the video. You should have some copies , but will see if Red or Chris happens to still have some VHS cvopies of them. BS, MELSkyworks Parachute Service, LLC www.Skyworksparachuteservice.com Quote Share this post Link to post Share on other sites
JohnSherman 1 #32 June 22, 2011 Those test were conducted by Flight Concepts to certify them to build that canopy. They were not conducted by us. Page was there as an observer and he never reported those results to us. I do remember giving them a SRPilotchute just to prove it would do that big job. But a harness coming apart -Never. We use the same design today on both tandem and single. If there had been a failure it would have necessitated a design change. I would ask the moderator to move this section of this thread to somewhere else as it is off the subject and muddying the water about the compatability issue which is the single biggest issue facing the industry today. Compatability is the route cause of Reserves failing to open after an AAD 750 foot activation. Quote Share this post Link to post Share on other sites
masterrigger1 2 #33 June 22, 2011 Quote Those test were conducted by Flight Concepts to certify them to build that canopy. They were not conducted by us. Actually, It was Glide Path at the time (first series of test drops) and they were co-leasing or sharing the drop aircraft. They were testing the then Nova 7 Reserve. We were testing both the Racer Tandem and canopy at the same time. these were heavy drops for the two of them. Also, at that time George Galloway (Precision) was building the canopies that you had designed. Glide Path/Flight Concepts then later began manufacturing the canopies. Quote I do remember giving them a SRPilotchute just to prove it would do that big job. Funny that you mention that.. It actually did it's job, but most had a split in the fabric post drop. Quote But a harness coming apart -Never. We use the same design today on both tandem and single. If there had been a failure it would have necessitated a design change Well I guess I just need to find the video!...or you could just simply ask Chris Gay or Red to back up my claim. Quote the water about the compatability issue which is the single biggest issue facing the industry today. You are talking about two completely different compatabilty issues. One deals with TSO compatabilty. The later deals with sizing compatabily (fit). Quote Compatability is the route cause of Reserves failing to open after an AAD 750 foot activation. I agree, but also H/C design issues are about 50% of the problem. BS, MELSkyworks Parachute Service, LLC www.Skyworksparachuteservice.com Quote Share this post Link to post Share on other sites
pchapman 261 #34 June 22, 2011 QuoteThey were testing the then Nova 7 Reserve. Now there's something for discussion! ... in another thread at another time. But one can't help but snicker a little. Quote Share this post Link to post Share on other sites
