JohnSherman

You might find some useful information here: http://www.jumpshack.com/default.asp?CategoryID=TECH&PageID=RISERANALYSIS&SortBy=DATE_D There are additional papers about risers and 3 rings at the same location

The canopy is packed into a deployment bag which has its own hand deploy type pilot chute. All of which is packed into a direct bag with static line attached to the aircraft. The direct bag uses the canopy lines to close the bag in the traditional way while the inside bag uses the pilot chute bridle to close the bag. The idea is to deploy the second bag with the first bag, pushing the entire deployment downstream beyond the initial blast. It does take a bit more altitude but the slider comes down at the correct time.

I am looking forward to see the video but in the mean time I think I can explain our differences. We are comparing apples and oranges and pears. Line dump, Bag strip, etc. (all the same thing) is not necessarily a bad thing, in and of itself. What does happen is when the bag opens and the slider is not constrained it can move down the lines, it will have a different reaction to different deployments methods depending upon the orientation to the relative wind. There are Horizontal deployment and vertical deployment. There are two types of horizontal deployments, direct bag and ripcord activated. Verticals all work the same. In a vertical deployment, when you dump the lines, the unconstrained slider will drop down the lines away from the canopy increasing the "Plate" inflation area. Depending on how far the slider migrates down the lines the opening shock will vary. The more migration, the harder the shock. This can and has broken necks in the most severe cases. At low speeds after a cutaway you will never notice it. However, anything from a streamer up can be problematic. The SPEED bag absolutely prevents this, but you could use a rubber band, which does nothing to discipline the deployment of the lines. In a horizontal deployment, using a direct bag, the slider is blown down the lines during the deployment of the lines when the canopy is still attached to the bag and that big "C" occurs between the jumper, aft of and below the aircraft, and the canopy, still attached to the bag. During this moment the slider is exposed to a relative wind which blows it down the lines toward the jumper as the deploying canopy is actually upwind of the jumper. Hence the "Double Bag" with which the military is saddled. A SPEED Bag won’t help you much here except to keep the lines more orderly, but a rubber band could replace the “Double bag” The Horizontal deployment with a pin pulling static line doesn’t experience the big "C", as the top of the canopy is not attached to the aircraft and a true horizontal deployment occurs. In this orientation the slider is resisted by the relative wind holding it in place during the early stages of the deployment awaiting its normal function and the jumper is correctly downwind of the deploying canopy. In this configuration line dump, even if it happened, would not be noticed as the controlling device, the slider, is functioning normally and has not been forced away from the canopy by the relative wind and in fact is held in place until the canopy begins to spread. Once again the SPEED bag isn’t needed to keep the canopy and slider contained as the relative wind does the job. However, a more orderly line deployment would be bonus. I have found that the only way to define whether or not some high speed deployments were aberrant is to have instrumented the deployment and apply the “Stink Test” to the results. We know what a normal deployment graphic trace looks like and sampling at 500 times per second we can actually get a better picture than we can see on video at 30FPS. I have done a number of tests where they looked normal on video only to find aberration within the data. All this occurred before the SPEED bag was developed. Additionally, this is why, in our “Owners Manual”, we recommend the center of the slider be held in place by a rubber band secured to the inboard “B” line on all ram air canopies in all situations.

Kelly, At that speed 240KTs = 276MPH you would need to film at over 200FPS to even see it with the naked eye. The "Dynamis pressure" at that speed would be close to 200 Pounds per sq. foot. Line dump would occur in less than .1 seconds. So you might get 2 frames which had clues at to the actual event. Didn't "Riggerlee" just say they were tearing up pilot chutes at half that pressure. What kind of aircraft did you do that out of. I want one. John

The pertinent information would be put in the owners manual. As such you would be required to follow it. You don't have a scale which will go to 100 pounds? How do you measure ripcord pull force? I guess they can't afford a fish scale either. The manufacturer would determine the Effective Square Footage of their pilot chute and placard it as such. They would also placard the container as to what the "Effective Square Footage" of the pilot chute to be used must be. The rigger would confirm the compliance of the ESF relationship then they would use a fish scale to measure the extraction to confirm the compliance of the pack job. Please read:http://www.jumpshack.com/default.asp?CategoryID=TECH&PageID=Extraction_of_Rsv.&SortBy=DATE_D This isn't rocket science!

Your posted video is a lot of ground - sky. There is no way to design for such a scenario. Except provide for a more positive cutaway. One anecdote does not a parameter for design make. Not that it shouldn’t be considered. The designer must consider the overall picture. Did you know that there have been about 10 broken necks from Free bag deployments. They are very prone to line dump. The Velcro pouch will dump the lines at about 12 pounds. Only one of the safety stows has to release for the canopy to escape and because of the continuous nature of the safety stow, the off side stow looses all retention of its bight. All of this is unnoticeable at low speed cutaway, but when you get to higher speeds the principal falls apart. That 12 pounds to dump the lines is exceeded by about 10x and the low side stow is 5 pounds and the high side stow is also 12 pounds, you get a canopy right now! Before the lines extend. For those you believe every jump is a line dump I ask about the student at Sandwich who broke his neck on opening which killed him at the same time he broke his harness. I had a lawyer ask me to help him sue the harness maker. I told him the harness was OK while asking him what he thought broke the jumpers’ neck. That’s line dump, line strip, canopy dump, out of sequence deployment or whatever you want to call it. It’s all the same and must be avoided. The “Speed Bag” does that. It 100% prevents line dump and provides for a more orderly deployment, controlling the lines, accelerating the bag with each stow release to reduce overall “Snatch” and has been statically shown to reduce malfunctions from about 2 % to .03% at a sixth sigma level of confidence. It actually takes no more effort to deploy a “Speed Bag” than it does a Free Bag. See the Videos in our gallery, It is the top one: http://www.jumpshack.com/default.asp?CategoryID=Video%5FGallery

I said it because the manufacturer really doesn't have to test the container. But he must design it to not require an extraction force greater than the pilot chute drag. That to me seems intuitive. The assembling/repacking/inspecting rigger is the one who must measure and certify the extraction force is not greater than the manufacturer allows. The same as he must certify the ripcord pull force doesn't exceed the standard. Please read:http://www.jumpshack.com/default.asp?CategoryID=TECH&PageID=Extraction_of_Rsv.&SortBy=DATE_D

So what. The MARD is sometimes as fast as the Racer. The Racer has been out there for over 30 years and has always been that fast. The MARD has a comparatively short life. It takes a mininum of 10 years to field prove a reserve system. The Racer certainly has not had as many failures in that total time as the MARDs have had in their short life. European Riggers have reported to me a 15-20% failure rate on MARDs. If you are willing to risk your life on that "Rube Goldberg" system then go for it. If you believe everything UPT tells you I've got some good Florida land I would like to sell you. BTW: Life does not begin at line streatch. It begins when the rate of decent is arrested. People have been trying to divide the sequence for a long time to make excuses for their poor overall performance. Pull to open is all that matters. But if you are comfortable landing at line streatch so be it.

Of course you have to test the container. I will go farther and say that if you arn't designing your containers to to provide for a maximinum extraction force based on your pilot chute you arn't doing you job. When I started I only had the MA-1 but I knew what it drug and when I went to the free bag I set limits on extraction. Any designer who hasen't done that should take up setting pins at the bowling alley we send turkeys to. Sorry 'bout that but there is more to this business than looking good!

Now that Ted is gone and Dan doesn’t participate in this forum, I guess It falls upon me to tell the story. The original Poptop Reserve was a chest mount designed and patented for Strong Enterprises by Dan Poynter. It was based upon the USAF emergency back. I licensed the rights from Ted for use on the back as a “Piggy Back” We called it the SST. It had 2 pins. Steve Snyder Enterprises entered a license negations with us which eventually collapsed. They built some 400 rigs at Stinethal in North Carolina. The video tapes from those days clearly showed a vast superiority in reserve deployment to the internal PC rigs. The marketing folks from the internal rigs denied that you could deploy a reserve in 2 seconds and claimed that their rigs were just as fast. “Tell a lie long enough and loud enough it becomes perceived as the truth”. That’s how the water got muddied about the speed of deployment. Without license or permission a British company jumped into the fray but failed to understand the design and made a mess of it so bad that the red bulletins (safety notices) stacked about an inch high permeated the field. Then the one pin internals came along and the public wanted a 1 pin poptop. We designed and patented one. We never released it as it presented more problems than were solvable and was not as good as the 2 pin. The “Quick loop” (closing loop for the reserve) was designed and it took all of the work out of the pack job as it was adjustable after the container was closed and pined. Professional riggers will now tell you that a Racer Poptop is easier to pack than any internal. Other Poptops were designed to take advantage of the superior design and they were mostly one pins. One pins require a large heave plate on the top of the spring to hold it place. These plates are heavy and in tests they fell away from a cutway main faster than the jumper. Despite efforts to force me to change the design I have never found anything even equal to Poynters original design except the Quick loop modification. For those who mention the possibility of line snag. They should speak with their rigger. Do not accept any pack job that will not allow a free passage of a line across the front surface of the container from any angle. Drag the line while it is in contact with the container across the poptop and if it snags the line the rigger needs to do it over. The idea is to make a recess like a baseball catchers glove into which the spring depresses. Done properly the poptop is less likely to catch a line than an internal. I am posting here a link to show just how fast a poptop is. The video compares it to a MARD. I suppose it will show you the disadvantages if there are any. http://www.youtube.com/watch?v=ze0Rcp7E0to

Risers can be any length the designer chooses. They certainly must consider the issues already mentioned, but their length should coincide with the line length. A Ram Air canopy has an arc with a point of concentricity at some point below the arc. The designer backs off this point to develop the overall line length then assigns a portion of this length to the riser. Longer risers shorter lines and vice versa. Ask the manufacturer what they reccommend for the correct length.

We tested to a max of 33PSF (Q) which occurs at terminal for a Freefaller (120MPH+/- @2000'). At 300 FPS your Q is in the neighborhood of 100+ pounds per sq. Ft. No wonder you were blowing everything up. See: http://www.jumpshack.com/Q.htm for the value of "Q" Pounds per sq. ft. The speed in FPS, Knots & MPH are across the top and altitude is the "Y" axis. I'll bet the video is blured I would imagine the amplitude is not any more but the frequency must be off the chart. In the test at Ames we tested refueling drogues to 200Q so I am aware of what you experienced. I have video from Ames with drogues at 200Q stable as a rock. I may post them for your entertainment, that is as soon as I get them all digitized. John

The first event in an opening sequence is "Snatch" which technically means "Accelerating the mass to speed". This sits you up into a vertical position. The next phase is "Plate Inflation". A high speed mal might not achieve this state. Snatch turns into a streamer. Your speed increases and both you and you passanger (if you have one) begin to have your feet float up and you find yourself on you back. Most of the time you don't realize it as you are looking up at the canopy. But note your neck angle is less. You are now effectively back in free fall on your back. Your malfuncrioned main is generating no drag. Remember Vasili in Guam. Look at his pictures. Let me expand upon the phrase "No Drag" I find it analogous to No Gravity. Astronautes will tell you there is no such thing as no gravity. They call it "Micro Gravity". So when I speak of No drag I mean Micro Drag, as technically, unless it is not decending there is some drag.

Come on Kelly, I did it years ago. I have published the maximinum extraction force for any Racer and my pilot chutes are placarded with the "Effective Size". If the pilot chute won't pull it out the extraction is to high. If I can do it so can everybody else. It's simple to find out what your drag is and limit anything over that. You don't even have to test the container. OH BTW: It was nice to have the Ames Wind Tunnel time but it is not necessary to do the job. I can and have used 2 other methods. One for developing the Cd for our tandem drogue. (.12)

Ever see a jumper on his back with a mal over his head, he is looking up at it, not releasing he is on his back. That’s a zero drag mal. Now release one riser. Of course a riser won't block a pilot chute. But it is a weight with some drag surface at the end of 10 feet of lines which are attached to about 6-8 feet of flopping flailing fabric which could easily overcome the pilot chute and it's bridle. I am not sure whether you are calling me stupid or those unconscious people who died when their AAD fired at 750 feet and their reserve failed to deploy. Or maybe you are calling the rigger who pack said rigs stupid. I agree that sometimes you gotta just shake your head but you shouldn’t just walk away. You gotta try. Yes, it is a lousy Standard and unfortunately the only thing we have. Better it than nothing. It is absurd to have a pilot chute standard that doesn't include measuring the drag but that is what we have and I for one have been campaigning to change it among other things. Have you been helping? While I do recommend transitioning from flat to head high during deployment. I don't believe that is what you are referring to. In my paper I recommend testing using this position, only as a compromise suitable to every rig, to measure extraction force by the inspecting rigger. I figure we can't ask a rigger to do this more than twice during an inspection cycle. If you like a different direction, say so. I could handle straight up at 90 degrees. I agree completely that such a scenario of giving up and assuming a flat and stable with a big burble is possible. But what does that say about our teaching if it is true. However, none of the incidents referred to in the advisory, that I have examined, have shown this to be the case. There are videos of high bag extraction force all over the web and more stories from riggers. Yet none of the manufacturers have made an effort to identify, and limit extraction forces or, pilot chute drag capability. By comparing the two numbers we have mathematical proof of function and guidelines for riggers.

I am glad you enjoyed it. That makes the effort worth it. Thanks! The only pilot chutes tested are the ones shown. I believe Manley Butler did some testing but I have never seen anything published. I don’t believe that any other pilot chutes in the industry have been tested. THEY ALL MUST BE! The area of the pilot chute is what the manufacturer claims. Except for the V2, which we had to measure at the largest point. However, the physical measurement is of no significance as we only measured drag force and "Q" in the tunnel. If you divide drag by the "Q" you get "Effective size" which is what matters when evaluating. Effective size = Cd*So As to the variations, or the low side during dumping, that data is in an old fashion fanfold computer print out 1 inch thick. I still have it and sometime when I go to the shop (probably after the holidays) I will take a look for you. However, I don't see the need except for academic curiosity. What matters is the high side as that kind of oscillation will only occur when the device is tethered or very heavily loaded while being towed as a drogue. Nancy once tried a 24 inch Racer hand deploy for tandem drogue. Someday I will post that video (when I find it). It threw both Nancy and her passenger all over the sky. It is funny to watch as the pilot chute seems to remain stable but the tandem pair are oscillating violently below the pilot chute.

I have been asked, by several folks, as this thread has progressed, how can you test a pilot chute? Well we did it a number of years ago. I searched for the tapes all weekend and just got them digitized and uploaded. It is a boaring 8 minutes but your comments as to the occilations will be interesting. Enjoy: http://www.youtube.com/watch?v=Zva4gHVX_zI

***That is also why we reccommend a hand deploy pilot chute be packed into the bag of a direct bagged main on a student rig. -------------------------------------------------------------------------------- Can you explain this? When we first developed the RSL for the Racer it wes tested by two separate outfits. One used a tri-conical and taped the long fold at both ends and in the middle. They direct baged it and it would not pull the ripcord with the cross connector RSL. The other outfit did the same thing with a 28' C9. It worked. Remember neither had a pilot chute but based upon the tri-conical faiure we reccommend to all direct bag static line users a hand deploy and bridle be attached to the top of the canopy as a drag back up in case of streamer.

Tested to what standard? Do you or anyone else for that matter know the effective size or drag capability of their reserve pilot chute? Just because it passed a couple of drop tests with a selected reserve in a selected container doesn't mean it will do the job with an overstuffed container. What happns when the rig gets into the field and someone over stuffs it. The extraction force goes up beyond the capability of the pilot chute and you get failures at 750 ft when the AAD fires. See USPA Skydiver Advisory 3/10/10 Compatability is the issue. We must have maximinum allowable extraction force for every container and drag capability of every pilot chute to provide the rigger with mixing and matching guidelines. This is why the MARD is conceptually flawed. A maled main has zero drag, a collapsed pilot chute has zero drag. The reserve pilot chute has an unknown drag and the bag extraction force is unknown. And people think this is a well designed system!

Sure it does! That is one of the reasons we use a Cross connector; To maintaine the integrity of the drag. That's the big problem with single sided RSLs, they don't always produce enough drag. That is also why we reccommend a hand deploy pilot chute be packed into the bag of a direct bagged main on a student rig. To not use a cross connector is to forfit any drag you might have had within the malfunctined main. Additionall it controles the flailing of the off side riser which could cover the pilot chute from the air stream. Additionally, we found it to be useful in pulling the ripcord.

Well Bill, now that you have personally jumped into the fray, and indicate you understand the dynamics, I have 5 questions. What is the minimum drag you will allow for the malfunctioned main? What is the minimum drag you will allow for the collapsed drogue or pilot chute. What is the minimum combined drag of the malfunctioned main and the collapsed pilot chute or drogue? What is the maximum reserve bag extraction force you allow on your containers? Is your MARD system TSO’ed? If no, have you asked the FAA for a reading on the requirement?

Remember the "Green Star"!

Neither Bill Booth nor I would ever argue with Nancy LaRiviere. Put her at the top of the list.

From what I saw in the Video you don't need it. Your pilot chute launches and obviously drags and your bag extraction force is low. MARD are for rigs who have a lously pilot chute launch which has low drag anyway and with bag extraction forces which allow the rig to be swung around by the bag bridle. Not at all, I am saying that when a MARD link attaches to the reserve bridle with intent to prempt the reserve bag extraction function. It is acting as a reserve pilot chute and should be tested as such. Yes, the main pilot chute should be Certified in this case. Additionally, its drag capability should be documented along with the max allowable container extraction force. That's mathmatical proof of system function. The components which link the main pilot chute to the MARD link should be certified to bridle standards. In the videos I clearly see one riser attached to the rig (what you are calling RSL, so be it) the other or off side riser is perpedicuular to the streamer line, the lines are spread and all that stuff flying around scares me. I know you talked to the guy in Deland, didn't something like that happen to him? How perceptive of you to understand the function of the length of reserve ripcord as the governing factor. That a first for the industry and I am not being snide, Imean it as a compliment. However, the instulation of the incorect ripcord would violate the TSO. I can't fix stupid. I may or may not have been to the specific one to which you refer but I have been to a few where it was discussed. I agree about not going there and have not proposed it. I believe we have minimum regulation s for a reason. To protect the public is the job of the TSO. If products are released without consideration of TSO requirement and consultation with the FAA the manufacturer is being irresponsible. The lust of the almighty buck has got them by the balls. I am a capitalist to the core but unbridled capitalism is as evil as unbridled comuninism. Corporations large and small must play by the rules. I would be pleased to know if any of the current MARD producers have ever contacted the FAA about this question.

Lars, Now that we have been formally introduced I feel I can speak to you directly. I wasn't trying to bust your chops but I feel that in a Forum such as Gear & Rigging there should be no hidden identities. I do know some manufacturers do do that. They have admitted it to me. I believe in the light of day. The fact that we can deploy a reserve in 2 seconds and a Tandem in 4 seconds is a long established fact. We do it by honing all of the components to their maximum performance. For example the Drag coefficient for the reserve pilot chute is .84. It's the highest Cd for any pilot chute anywhere. It was tested by NASA at NASA Ames. (BTW: All reserve pilot chutes should be tested and placarded with their capability). The extraction effort of our container plays a part. It is limited to 110% of the weight of the bag and canopy. My published data calls for a max of 16 pounds, this is because of heavy tandem canopies. We are looking at different videos. That is why we are getting a .5 second differential. I was quoting the deployment on the Jump Shack home page. I believe the difference of what you got and what I got is about .5 seconds and is not germane. It is academic.. They both occur in about 2 seconds. I would like to link you to more videos on my site but it is producing errors and I can’t send you the file as it is too big for DZ.Com. Send me your outside E-mail and I will send you some interesting stuff or you can wait until the site is fixed. If there was a cost to the Racer reserve deploying in 2 seconds it has never come to light. We have been deploying reserves in 2 seconds for 30 years. They used to say it wasn't possible. BTW: It takes about the same time for a terminal opening. The distance increases because you are going faster. But now they can't deny it because the MARDs can do it. The Mard does it by shortening the bridle. If I shorten my bridle to say 5 feet I could cut off some distance from the 97 feet it now takes, Footage, I hope will be forth coming. I have prepared the bag and it is packed. I don't think it will ever be released as I do like the long bridle, but it will be a neat demonstration. Now, to the meat of your question. How do we make canopies inflate faster? Try this. The dynamics of the drag of the pilot chute is such that it creates a tension between the high dragging pilot chute and the bag. I believe it actually stretches the bridle during line deployment. The tension is extended through the bag and into the canopy lines which accelerate the canopy out of the bag into a more rapid inflation. Failing that theory I don’t have a clue, but it does it and it has done it for 30 years, and that is what is important. John