JohnSherman

It is the cutter. The fact that a cutter can fail and trap the loop. This act is "interferance with the normal operation of". Pass through cutters must be redesigned to allow the loop to release in case of "failure to cut" or we must find a way to get around this problem.

The FAA considers an AAD a "Black Box" and does not regulate them. They do not affect the TSO. The doctrine adopted by most of the H&C manufacturers is "An AAD must not interfere with the normal operations of the H&C". It has become recently apparent that cutters can trap the loop preventing deployment. This means that they, the cutters, can and do violate that doctrine. This is relatively recent information in the industry and remains unresolved. If the current cutters do violate that doctrine then all of the AAD’s in use today would become unusable. My position is that each jumper must make his or her own decision as to the benefit/risk involved pending redesign to a more compliant system.

It the pin blade which is .094 +/-.02 diameter will freely insert into a .104 diameter hole in a check block. Then it passes the specification test. We check out pins with a .101 diameter. As a pin manufacturer who understands the rotary swage process of cold forming the pin blade. I don't have a problem with straightening them a small amout. Do it between two pieces of wood so as not to upset the diameter or finish. The specs we use were written when the pins were used with cones with a metal hole. That application was much less forgiving than the cloth loop. Just about all of the info given so far in this thread is good. Caution must prevail

At 2000 feet, 1 second after a cutaway you have a decent rate of 36FPS (20FPS on initial descending canopy plus the additional 16 feet of the first second acceleration. The Rho for that altitude is .002242 Slugs, Apply (½ Rho V^2) the formula for Q, you have about 1.5 pounds per sq. ft. (1.5Q). With a Cd=.65 and an So=25 sq. ft. you get 16.25 Effective sq. ft. At his point in time you have 24.4 pounds of drag. If you need 75 pounds you could wait a second or so. Drag= Cd*So*Q

Thanks Peter, you are right on. It really doesn't matter how much extraction force is required if the pilot cute will handle it. When one of the manufacturers told a rigger that 75 pounds of extraction was acceptable. I noted that it would take a 25 foot pilot chute to do the job. That is If the pilot chute had a Cd of .65 or better. Pilot chutes must be qualified and marked with their effective size (Cd*So). We have 2 options on our reserve pilot chutes, Standard and SRP. The standard is 36 inches and the SRP is 30 inches. Both have a Cd of .84

Proposed Solution for Reserve Extraction Issue First we must acknowledge there are bad rigs in the field and that most of the problems occur with the main closed. A MARD won't help if the main is closed. The purposes of this effort are to surgically and methodically weed out those rigs and to develop a certification and testing procedure to prevent future occurrence. For the purpose of this discussion let us think about a horizontal plane with the wearer lying face down along that plane. Think of a protractor on the back of the jumper with zero degrees at the head, which is to the right, and one eighty at the feet, which is to the left. We can see that the first 20 degrees and the last 20 degrees are for all intents and purposes unusable. For clarity we acknowledge 90 degrees as straight up and perpendicular to the jumpers back. The field correction portion of this procedure must include a test for bag extraction. This test must be simple and indicative of the overall extraction effort. It must be made during the time when the rigger first opens the container by pulling the ripcord. It must be made with the main container packed and fully closed. It might be recommended that the owner don the rig and lay on their stomach for the test. They should pull the ripcord and the rigger could then, after pilot chute launch, test the extraction. The direction of the pull on the bridle for the extraction test should be 45 degrees up toward the head from the perpendicular or at 45 degrees on the protractor. Assuming the bridle is located at the top of the bag, which is at the top of the container, a pull in this direction would cause the top of the bag to lift and begin rotation as it is extracted. Selecting this direction avoids the airing of the issue of a difficult 20-degree pull or the seemingly impossible 160-degree pull direction. I have seen extremely difficult pulls on both directions but I believe the recommended direction will be the lowest pull we could expect to encounter while still being indicative of the overall requirements. It is the direction most commonly seen during actual deployments. We only get one bit at this apple ‘cause we can’t put all the work on the rigger that needs to be done. We really can’t ask them to do more. The force extraction limits must have a base line force described by rule. I would begin by recommending the weight of the bag and canopy plus ten (10%) percent. This percent overage is negotiable from my perspective and could go up quite a bit depending upon what others want. Certainly something must be added to allow for some friction. I could handle whatever as long as it didn’t go over two times (200%). Rules about what to do as a result of the test: The rigger is there to re-certify the rig. If their initial extraction test exceeds the base line limit, described above, then the rigger must consult the manufacturers instructions to see what limit the manufacturer has allowed on this container which was based upon the drag capability of the pilot chute. If the test results fall within the recommendations of the manufacturer then the rigger may proceed. If the initial inspection test procedure results fall within the baseline requirements then the after pack job test may be waived. If the manufacturers’ specification allow a greater than base line force then the rigger must, after closing the rig and before sealing it, pull the ripcord and repeat the initial test to assure the pack job is good enough to meet the manufacturers extraction requirements. If within compliance, the rig may then be reclosed with minimum disturbance or relocation of the bag and canopy. All other requirements being met the rig may be sealed. Certification and testing: The manufacturer must develop and publish the allowable extraction force for their container, as above. They must also publish the pilot chute requirements for that container. The pilot chute requirement would be specified as “Effective size” or physical size times the drag coefficient (Cd*So). This information would be published in the owners’ manual. It would appear as “Allowable Extraction force = xx“ and “Pilot chute effective size requirement = xx inches/feet”. Even if the containers extraction force doesn’t exceed the base line a minimum effective size of pilot chute must be specified. I really don’t think it matters how the manufacturer derives the maximum allowable extraction force. What really matters is the drag capability of the pilot chute. Here I believe is the difficult swallow for the manufacturers. All pilot chutes must be placarded with “Effective Size” (Cd*So) or they could be placarded with physical size and Drag coefficient, whatever. This identification of the capability of the pilot chute is necessary as they are components that could potentially be interchanged from rig to rig. With the containers marked with Max effort and pilot chute size requirements and the pilot chute marked with capability the assembling rigger may choose within those numbers. Lets face it, the manufacturers are going to have to test their pilot chutes and develop the numbers so as to placard them. I believe that the PIA could set up a deal with some school like Embry Riddle to test pilot chutes in the wind tunnel for a fee. I don’t care how they test them but the FAA ACO might… or not! Initially, in the field, only the extraction test may be made, as our pilot chutes aren’t identified with the “Effective Size”. As a policy I believe the PIA could require it’s members to publish the required data for their pilot chutes within an agreed upon time frame. “I know, how can they publish the allowable extraction force before they know the drag of their pilot chute”? They can’t, but I won’t tell.

We have just begun a conversation to raise the deployment altitudes across the board by 500 feet. I have no objection to doing that, if it can be proven it will work. Root cause definition and backup data must be aquired and evaluated before such a move is made. As a parachute designer I understand the root cause of most of the failures and they do vary slightly from system to system. I do not believe that raising the altitude for AAD firing to 1250 feet will cause a reserve deployment bag, which takes 75 pounds to extract from its container, will find more drag for its undersized or otherwise inadequate pilot chute to generate more force. Nor do I believe that a pilot chute with a drag coefficient of .33 will increase its drag to a level necessary to perform its task. Nor do I believe that rigs designed with over applied cantilever flaps which are designed to reduce pin pull force will find a way to open, enough to allow the pilot chute out into the air stream in a extra 500 feet. Someone even said that this feature was intentional to prevent a “2 out” situation. These conditions and others that are found singularly or in combination create a mutually dependent failure mode that prevents a container of this type from being reliable enough for personnel use. I have a plan of corrective action written and I will post it very soon. I sent a copy to Cliff Smucker over a mounth ago and now he won't return my e-mails or phone calls. Oh! the politics of parachutes

At the 2011 PIA Symposium, in an interview with Douglas Spotted Eagle, UPT’s Bill Booth, http://www.youtube.com/user/VASSTTraining?blend=12&ob=5#p/u/30/tQuJr5wuvSw recommended raising the deployment altitude by 500 feet in reaction to 9 fatalities (at that time), that had occurred after an “AAD” activation at 750+/- feet. This was a tacit admission that some of his equipment might not be able to deploy a reserve within the required 300 feet, as some of the failures were on equipment of his manufacture. A seven-hundred-fifty foot activation altitude provides a safety margin of 250% over the TSO requirement of 300 feet for a reserve parachute to open. Booth’s recommendation would give a safety margin of 400%. According to sources, Robert Feldman, Attorney at Law (who does legal work for UPT & USPA), will make this proposal at the August PIA meeting. Do you believe that the 50 year old activation/deployment altitude standards should be changed or not, and why? Please vote in the pole and make you comments on the thread.

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.

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.

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.

You sir are a perceptive individual. Hear is the story about National. It is significant because of the NTSB report which questioned why there was no limitation placard. The reason there was no placard was that none was required. "Standard Category" parachutes were certified to 5000 pounds and because that is the level where we start loosing body parts it was felt this was an "Unlimited Category and required no marking. The reason the National Phantom 26' you mentioned came apart was that it's tests were inadequate. National engaged Theo Kanackie (Farther of the NASA Gimini Program recover canopies) to calculate the weight and speeds to achieve 5000 pounds so as to be able to certify in the Standard Category" 'cause the European market demanded it. Theo was contracted to develop weight and speeds for each of the Phantom sizes. He made his calculations using Dr. Cockrells model. However, he was never told the canopies used a diaper. His calculations were for canopy first deployment of infinite mass. Diapers were used in the actual testing. Theo didn't even know what a diaper was. Without getting to technical, diapers like bags reduce opening shock by about half if they work properly. Diapers have been known to "Spit "the skirt out of the diaper causing canopy first deployment. Just like the diaper wasn’t there. This usually occurs at high speeds.. Testing for national went fine with out "Spitting" until they got to the Phantom 22 which did "Spit the diaper and failed the 5000 pound test. The Phantom 22 was ultimately certified in the "Low Speed "category. What this means in practical terms was that all of the Phantoms larger than 22' , which were certified to the "Standard Category" (5000 pounds) were actually tested at 2800 pounds ( less than the 300o pound “Low Speed “canopy) approximately. The Phantom 22 was tested at about 1500 pounds. The FAA and the NTSB never investigated the mater thoroughly. The FAA was criticized for not having a placard on the failed rig identifying performance limitations. The FAA had no answer 'cause they didn't understand their own standards, which required no placard ‘cause it was unlimited. This was probably the beginning of the effort to require "Weight & Speed "testing .as a method of certification. While a myopic view would deem this to be a good method of certification it defies the ability to mix or match from other systems also certified to the same weight and speed. This concept of varying shock loads is easily confirmed by reading the PD reserve owners manual where it says different canopies from different manufacturers tested at the same weight and speed will produce different results.(end quote) So much so as to be able to disintegrate a weak harness when mixed with a hard opening canopy.

Back in the day to which you refer the Boston and Chicago FAA MEDO offices did required proof of measurement of the forces "Certified to", either 3000 of 5000 pounds. Their position was it’s required so prove it. I still have the force transducers and the Peak (only remembered the peak force experienced) meter we used to TSO the Racer to the Standard or unlimited category.. The New Jersey office did not enforce this requirement. Neither National or Para-Flite were required to make this measurement. I know this because of my association with Pioneer who dealt with the Boston office and my own experience with the Chicago office along with the fact I had a very close relationship with Para-Flite at that time. They convinced the MEDO, which is responsible for that area, that the Strato-Flyer would not even reach those force level when tested to the chart and the MEDO allowed them to get away with it. Fortunately the Strato-Flyer was a well built canopy. National was not so lucky but that is another story. Jim was correct about the chart. The chart was generated by Helmut Heinrich and included in the NAS 804 as a reference only. The original copies of the NAS-804 has a small font caveat below the chart which read "This chart is for an Air Force C-9 28 foot canopy only and is included for reference only". This caveat did not appear on all renditions of the standard when reproduced by the civilian community. I met Jim Reuter at the Houston AIAA conference during that time and we discussed the chart with Helmut who admitted that the chart was completely wrong and had no value for anything. This was after Dr. David Cockrell had presented his math model for opening shock. Dr. Cockrell’s model is in use today and I find it to be a useful tool. FYI the Formula is F=Cd*So*Q*Cx*X1

The premis is simple. Parachutes systems from different manufacturers certified to the same weight and speed can and do open at different force levels. Depending on such things as angle of trim, cut of the nose, size of the cells ect. Weight and speed can be used to certify a parachute system and works fine for a single system but can't be used for compatability guidance because of the different forces produced from different manufacturers,. Force loading can also be used to certify parachute system and can be further used to provide compatability guidance. See:http://www.jumpshack.com/default.asp?CategoryID=TECH&PageID=Compatibility&SortBy=DATE_D John

Drag on a pilot chute is based upon 3 things: Dynamic Pressure (Q) (1/2 rho*v^2) This is the resistance of the air or force aginst the falling body based upon speed and altitude. The physical size of the canopy and the Drag Coefficient of the canopy. Together make the "Effective Size" of the canopy. The formula is Drag=Cd*So*Q. 1 second after a cutaway you are moving with about 1.5 pounds per square foot of pressure to work with. Multiply the Effective Size of the canopy with the Q and you get the drag. A 36" pilot chute has a (So) Surface area of 7.06 Sq. Ft. This 7.06 feet is reduced by the Cd 'cause nothing drags at 100%. For example an MA-1 has a Cd of .65. Multiply .65 times the pgysical size to get the effective size then times the Q to get the total drag. It really doesn't matter what the extraction force is if the pilot chute can handle it. And believe me, not all pilot chutes are equal there are some which won't pull the hat off of your head let alone a bag out of a container. All pilot chutes should be marked with their "Effective size" John

There is no difference. The boundary layer is blown off the top of the wing the same in both cases. Additionally, Air Lock canopies also fail the same way. If air locks worked then ridge wings wouldn't stall.

It's not about the material or the record of the CYPRES or anyother AAD or why I wouldn't allow the floating loop. It's about "if the cutter fails does it fail-safe?" "does it not interfear with the normal function of". We must make it better! We must make it fail-safe. I don't care if we use cutters which fail open or use pin pushers or pullers. Whatever we use must be fail-safe. That way we still have the oporitunity to save ourselves!

That's great Jerome! Show me the video! I didn't see it on your web site or Facebook Here is mine:www.jumpshack.com Chow

Parachute Labs. has all of the information to which you allude. Most manufacturers don't even know the capability (Cd) of their reserve pilot chute, ours is published as our allowable extraction forces. No it is not! However, the designer must not allow the container design to malfunction when over or under stuffed. We studied that issue over 20 years ago and established deployment control parameters, which could not change with, content size. These were dimensions for certain locations and they are the same on every Racer ever built. It ain't rocket science. We also tested our reserve pilot chute as well as both the old and new Vectors at the NASA Ames 7x9 facility. Results: Racer Cd=.84, Old Vector Cd=.79, New Vector Cd =.33. The changes to which you allude (single complete unit certification & altitude increases) probably would not help: “you can’t solve stupid and it is difficult to control greed”. At his point I find it difficult to remain civil. As I find it necessary to comment on the work of my peers. I can think of one or two that that are exempt from what I am about to say. But, generally, the people who make your gear are a bunch of ill educated copycats who can sew. The ones who are “inventing” and are being copied are not interested in doing much more than appeasing their client base. A Camel is a horse designed by a committee. If the committee is client base and the designer only panders to that base then you will get the results you are getting in today’s gear. The problems we are addressing here today aren’t new. I told BJ after he jumped the hole in Mexico that “it was good his main worked ‘cause his reserve wouldn’t have”. He just stared at me. This problem has been going on since then and this Yes, that is about where it all went wrong. I was heavily criticized for my stubbornness to change at that time. We did make some changes for that client base but we mostly lost market share to cosmetics and ignorance. All of that glitter was not gold or as my British friend calls them Gucci Rigs. Today we are paying the price, “and now there are eleven”. You are right it isn’t 1991 and SOME gear is different. I believe that the folks who weren’t diligent and made it different should pay a price for their negligence and sacrifice their ill-gotten gains. That is the way it works in our society. To make changes to appease ignorance is to reward those who didn’t do their homework and is unacceptable. Maybe one piece of cordura between the world and the freebag was better after all. I hope you wife is OK. Oh BTW: you don’t get to add the 300 feet to the distance it takes for the canopy to come out of the bag. It’s 300 feet from pull. Do you know of a rig other than a Racer that can do it?

Container Tension: Yes, we should not build containers that depend on container tension to stage the reserve deployment. If you grossly under stuff a Racer there is no tension and it will still stage. We box the lower corners of both our main and reserve. We do that to stage the bag. It doesn’t mater how tight the corner is, the bag will still stage. The bags are designed to rotate out by pulling the top of the bag and pivoting in the boxed corners. The main does use some tension to keep the bag from falling out if the pin is pulled on the ground. That tension is created when the bag is forced against the bottom of the reserve against the vertical partition. We rotate the bag from that location. We design our containers so that if the container is opened while walking or standing the bag won’t fall out. However if you remove the rig from your body it will fall out. My internal spec for this situation is that the bag should take no more than its weight to pull it out of the container. However, because we know the drag capability of our pilot chute we set the allowable bag extraction force to about double that. However, that can be better understood by reading: http://www.jumpshack.com/read/tech/Reserve_Bag_Extraction_Forces.pdf

Great question Lee. Here is the Jump Shack response: There should be no such thing as overstuffed. The manufacturer can't put that on the rigger. If a rigger can get it in then it should come out and deploy normally. Any rig which can be jammed from over stuffing is unsafe and should not be used. There are some great riggers out there who can pack anything. They should not have to worry about function because of fit. We publish a list of canopy volumes and recommended container sizes. We do this because of cosmetic reasons not function. I have seen some really bulging pack jobs on Racers, so overstuffed that the corners won’t tuck but they still work.

Remember the other system with the pouch and bungee stow will perform much different from the Speed Bag. This difference is the little dance a bag with rubber bands does as each stow releases in turn. First one side then the other. This dance was wrongly dissed by some folks in the early years and vestiges of this mistake still exist in some peoples minds. The wobbles are good. They accelerate the mass toward "speed" a little bit at each wobble. Remember that "Snatch" is the acceleration of the mass to speed. If "Speed is acquired suddenly then the force is more concentrated and noticeable. If "Speed" is acquired gradually then the negative acceleration is gradual. Softer smoother openings. The Velcro pouch only requires 12 pounds of force to eject all of the lines at once. The Velcro is in peel. The Bungee stow was found unable to maintain a balanced release force left to right, in test done many years ago for PIA by Bob Nixon From Relative Workshop and myself. We found the force could not be maintained or was it predictable because there is no mechanism to keep the two grommets separated. The recorded forces were in the neighborhood of 12 pounds on one side and 5 pounds on the other. 5 pounds will not retain the stow during deployment. Creating a potential for Line dump. Flat on the ground this all works smooth and that is the problem.

What everyone is missing is the fact that the table or floor acts as a holding hand during a run out of a bag and canopy deployment on the ground. Observation can only be made if the bag hits nothing but air. If it bounces off the ground the ground and the bounce will bias the dynamics and the observation. Note the video on our web site referded to by Scott is of Peter doing the run out. At no time until after the canopy is out of the bag does anything hit the ground. Notice how the bag spins and jumps. If the ground or a table were to be encountered it would abate the total force and disrupt the sequence. As to only one side opening this is normal as the canopy will follow the path of least resistance during extraction. It is only necessary for one side to open for the canopy to excape. The Air Force Academy was experiencing some 15 mal/year out of some 850 jumps. They made their own Speed Bags with our permission and reduced their mals the first and second year to ZERO. They had one in the 3rd year of testing which the Speed bag had nothing to do with. We all use Speed Bags on our mains and have for over 10 years. If you want to learn about them I suggest you do the same. If you do you will be putting one on your reserve after you see the difference.

Seth I am adding the 29M to compensate for the failure of the altimeter to update in real time. Splitting the hair of time, not exact but a reasonable assumption when dealing with a device that only updates once per second. By using 2 methods: counting frames or reading the Metric altimeter we can see by both your method and mine that the opening is in excess of 300 feet. I concede that your formula is more precise but I was giving the benefit of doubt. I only examined the first deployment. BTW: How do you explain the loss of 5 frames per second on the altimeter update? John

The hand is quicker than the eye. Look at the “M” in the lower corner of the altimeter; it is in meters and if you are familiar with the device, as am I, you will know it has an update rate of once per second producing a possible error of whatever the descent rate per second is. I recorded the altitude in meters from just before the reserve pilotchute became visible to a point where the slider is down. That is 660 meters down to 589 meters - a difference of 71 meters, which converted to feet equals 233 ft. The lagging update of 29 meters in a second (watch the update just before opening for this indicator), or 95 feet added to the 233 equals 328 feet. Additionally, I counted the frames for the same duration. I got 126 frames. At 30 (29.95) frames per second that is equal to 4.2 seconds. Applying Newton’s Acceleration formula of 1/2AT^2 + 2T with an initial Rate Of Descent of 20 FPS we get 322 feet. The math indicates 322 feet and the altimeter indicates a possible 328 feet. Either way you look at it, this demo fails to meet the required 300 feet allowed for TSO certification. I’ll bet if there were a better/faster demo we would be seeing it. Additionally, this video appears to be slightly accelerated. I am counting 24 frames per second instead of the normal 29.95 (NTSC). This is based upon the update rate of the altimeter, as it seems to be updating every 24 frames. Because video is “time accurate” we would have to advance the time lines by 25 percent to be time accurate. The test fails even without this time adjustment. But I can’t help wondering where those 5 frames per second went. This video is but another attempt to “Bamboozle” the public. It does not answer nor does it address the nagging question of why did the Vector reserve fail on more than 3 occasions when the AAD was certified as having fired at 750+/- feet. The military stated, upon completion of a fatality investigation, and I quote: "A drag force analysis of the [redacted] revealed that the solid nylon design; which constricts airflow through the 6-inch diameter base opening, produces minimal drag." Here are my opposition’s pre-programmed and often-repeated answers to these facts: “The military doesn’t know what they are talking about.” “It just goes to show you can’t test a pilot chute in a wind tunnel.” IMHO this is physics in the key of C