JohnSherman

To that I say "Why" isn't the "Free Bag" going to release from the canopy no mater where it is, on the horseshoe? That's what a MARD does, is shorten the reserve bridle, that's where it gets its speed. What I am proposing is to take the MARD connection out of it and just shorten the bridle. A good pilot chute is a better anchor for deployment at all speeds than the variability of a malfunctioned main at any speed.

No, we used it (the 3 inch) because the 2 inch was polyester and the 3 inch was nylon. We knew the 2 inch didn't have enough drag and chose the 3 inch for those more drag and repack cycle. Interesting fact: It takes 1 second to deploy the bridle alone (it's about 16 feet from the top of the pilot chute to the top of the bag, the distance traveled in the first second of acceleration). We don't need 16 feet, we only have 8 feet max on our mains and that works well. A bad waist of altitude. Shorten the bridle and shorten the reserve deployment time.

I think we are talking semantics here. Under TSO C23b "Standard Category" is Proof loaded to 5000 pounds. The Approval by the FAA, under the Standard (5000 lbs) or Low Speed Category (3000 LBS), is the load rating. Maybe what you mean by load rating is the Weight and Speed to which a component or system is certificated to. I call that performance rating. To me "load" is in pounds force. BTW: You understand that is is not possible to properly match components for strength using the weight and speed system of certification. One more point: A Parachute Labs Reserves are marked with the "Maximum" Force encountered during testing rather than the "Average" which is called for. It seems foolish to me to list the Average force encountered when you are trying to assure the strength of the matted component won't be exceeded. If one were to match a harness with a capability of 2000 pounds to a canopy with and average of 2000 pounds then a max force would exceed the harness strength.

If someone has generated 5000 pounds opening shock at 180KTS and 264 pounds with a diapered square and it worked properly, can you imagine what the shock produced by that canopy at 100KTS and 200 pounds (normal terminal skydiver opening)would be? Jim was correct. He knew, as do I, the origin and foundation of the table. The author (Heinrich Helmut) acknowledged the total inaccuracy of the table 4 days before his passing at the AIAA conference in Houston. Dan Poynter can verify this. Additionally, this is why that chart should not be used for determination of weight and speed for TSO C23b components. I would disagree as the Racer harness Certificated under TSO C23b does have a rated load of 5000 pounds and we consider it unlimited in weight and speed. It was tested and certified to a measured load of 5000 pounds. This was done at 200 MPH with a 350 pound load with a navy conical undiapered. They were the most horrific openings I have ever seen. It sounded like a 155 howitzer.

Think about the difference stitch each makes. A Bar Tack makes a couple of rows of a 301 stitch covered by a dense application of perpendicular 304 stitches. There is more than one type of zig-zag. A 304 Zig-zag is simply a left to right and back stitch where a 308 is called a "Double Throw" zig-zag. It has a stitch in the middle of the left - right pass. I like to think about a zig-zag stitch ( both the 304 & 308) as a side view of a coil spring. It has the ability to be lengthened during a stretch of the fabric without stressing the thread. The 308 is stronger as it has the additional anchor stitch in the middle which acts as a pivot for the stretch. The bar tack has limited stretch because of the 3 passes of the 301 stitch under the zig-zags. On finger trapped braided lines the bar-tack has worked well but is intended to be only a anchor stitch for the finger trap. As a manufacturer I think either is OK for use in the field. We use the bar-tacker in production because it is faster and more automatic. However, every good rigger has a Double throw machine in their arsenal which is more valuable than a bar tack.

It appears that the opening peak had already occurred before the video begins. Opening shock is divided into 2 modes. Snatch and inflation. What we see on the video is inflation not the snatch. The stress in the jumpers body as he is pulled up and out of the frame suggests that he has endured a strong snatch force. This interpretation is not consistent with the movement of the goggles, described by the jumper, but that is not uncommon. I would speculate that he had a line dump.

I don't believe the rubber bands or the line set have anything to do with it. I see a partial line dump. I think some of the inside stows dumped causing the lines to tangle and allowing the bag to partially open. The release of the inside lines took the pressure off of the remaining stows holding the bag closed.

Terry, We had a lot of this happening when we first came out with the hood. I am attaching 2 photos; one is correct and one is wrong as is indicated in the title. I direct your attention to the one which is wrong. It has a RED arrow pointing to the conflict location which I see as the root cause. Note the actual steering line is crossing the riser from it's point of origin at the eye on the RIGHT side of the toggle under the toggle nose and up the left side. When the riser and the steering line load the steering line is forced to cross back across the riser, under the toggle, cutting the hood from bottom to top. [inline Toggle_Stow_Wrong.jpg] The admonition to the user is to assure the steering line doesn't cross under the toggle nose and is routed so that it goes straight up to the canopy from the toggle. [inline Toggle_Stow_Correct.jpg]

Interesting, before I said anything I would have to test it.

From the Racer Owners Manual. The Yellow Lolon cable comes from Loose and is their name for Nylon. Nylon being hygroscopic absorbs any lubricant over time. A well lubricated cable is necessary to allow the cable to pass through the nylon retainer loop under load. Cleaning the cable is actually unnecessary as the black goop on the cable is the residue of the cutting oil used in the housing manufacturing process. Oil lasts longer in service than silicone which seems to Hydrolyze within days where oil will last about a month depending on conditions. Due to the tolerances between the housing and cable I don't believe any amount of dirt will stop a lubricated cable from pulling through the housing. However an un-lubricated cable will fail to pull through the nylon loop with 10 pounds of loop load. The test is: Remove the end of the cable from the keeper on the back of the riser and pull the cable through your fingers. If it "Squeaks" like just shampooed hair then go back and oil it. Do not jump it unless it pulls through you fingers with NO resistance.

You should see what Kevlar thread does to the eye of a sewing machine needle. I use now and always have used spectra exclusively. I haven't seen the damage like you folks are talking about. I also use brass grommets. It seems to be the best combination.

From the "Quote" (above); I take it we have experienced this grommet wear with Vectran and Brass and Vectran and Stainless Steel grommets. Has anyone seen this with Spectra line and Brass grommets? Certainly, we have seen grommets with damage similar to the pics but that was from the Rapid Links hitting of the grommets. This is a wear issue. Does Vectran cause more wear on the grommets than Spectra?

Riser lengths also effect the arc-Anhedral, longer risers increase it and shorter risers decrease it. Also it changes the trim by moving the confluence point up you pull the nose and tail closer creating a slight curve to the bottom skin. By lengthening the risers you allow the curve to reverse. Designers design to a specific riser length or they should.

Lee, Thank you for the good words. You are correct: If you can get it in it will come out. But it sure is ugly when it is overstuffed. The pilot chute has enough drag to toss you around the sky. The container has no top corners to catch the bag Racer, because it works...

It restricts the mouth and retards inflation. See T-10 parabolic shape extended skirt consideration for example. Additionally, after inflation it directs flow to wrap around the surface reducing the drag/burble/low pressure/ area on top. Therefore; the lower Drag capability. Additional interesting fact: A pilot chute with a 50/50 design which has an “Effective Size” of 5.9 Sq. Ft and weighs 7 ounces will inflate and reach maximum drag capability in .667 second when free dropped by hand from any height. Bad assumption. It should be deployable from the belly to earth position but any good Skydiver knows to "Sit up and Dump". In fact most reserve deployments are from a more vertical position, after a cutaway for example. Think of the bag as a table cloth with a canopy (in a lump as in the bag) and the lines as they would be in the bag. Now pull the cloth. The cloth will move from under the lines before the bag has a chance to load the closing flap which is a vertical extension of the cloth. It works the same way when vertical. The fact is it has happened and will continue to happen until that design is improved. The other fact is the extreme difference in opening shock. Perhaps as much as 10 times has been my experience.

If one stow releases on the subject free bag the canopy comes out and can allow the slider to drop as it inflates before reaching line stretch. Ouch! There is no need to suppose any other scenerio as the SPEED bag exist and it was designed to speciffically address this problem. Tests at the USFA over a 3 year period showed the ability of the SPEED to almost eliminate malfunctions. They reduced their total malfunctions in a 3 year period to 1. Previous 3 year spans were generating as hign as 51 mals.

I am certainly not ignoring Newton. In addition to embracing Newton I am applying micro timming to the process. What loads when. The PC loads the bridle which loads the bag. The lines will load next as they have less mass than the canopy. The lines are now pushing against the velcro and the safety stow is trying to retain the bight but it can't because there is no tension on the bight on that critical side. The canopy loads after this because it is bigger and has further to go. The resason the bight doesn't release every time is that the last stow of the 2 locking stows is not always on the side with no retention from the bungee. The GK fatility is as explained earlier and was the first documentation of line dump. Additionally another GK had a bag strip in Key West. It was wittnessed by a Randy Mathews who followed him down to a grand where the GK (Capt Keller if I remember right) sat up and got an instant canopy. Those were with the "O" ring but the Safety Stow has the same problem. Jay Engle had a Raven blow up in Colorado and it was attributed to "Over loading". It was in a Racer with a Safety Stow Free Bag. He was at terminal and the bag stripped. That Raven will take twice it's specified weight at terminal. He is the reason we finally put the "SPEED" Bag on the Reserve. It's optional on the main but not on the reserve. You may not have experienced it but Para-Flite did during testing of the Flyer. Additionally, This phenomeon happens so fast that you can't see it even on stop frame standard video. I have caught an ocasional single frame which hints at this. The only way to know it is happening is analysis of the data and the results of the tests. The industry has built some really tough canopies because of this problem and the inability to solve it. If I could guarantee that any canopy I built would always be used with a SPEED bag I could reduce the weight and bulk signifficantly.

My Bad. Velocity (V) is part of Q. I neglected to include the formula for Q (Dynamic pressure.) Q = !/2 Rho * V^2 Rho is the Density of air in Slugs per Cubic foot and Velocity is expressed in Feet per second. Rho at sea level is .002378 Good Catch Sorry 'bout that

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.

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.

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.

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]

Terminal Velocity is best called "Equalized Velocity" it is when the pounds of Dynamic pressure equalizes to your bodies pound for square foot loading. For a human body which has about 6 sq. ft. of surface area at say 180 pound or 30 pound per square foot. We accelerate until we reach that equalization. Terminal velocity for a pilot chute is the same. It is when it's drag equals its loading. For a Racer pilot chute its occures about 1/2 a second after release as it weighs about a half pound and has almost 6 Square feet surface area that is equal to .08 pound per sq. ft. Therefor it reaches its "Terminal" almost instantly. It requires 1/4 a second for the Vector 2 as it weight about a pound. Twice the weight half the drag. A drop heigth of 5 feet would do if you could measure the time accurately. As I show above they won't hit the ground at the same time. Try it, I have and the numbers corrilate well to wind tunnel testing. I am not doing drops, I am comparing pilot chutes if you are going to drop them side by side as in a race then they must weight the same. The weight is the drag. You ask "How fast do you have to go to produce 20 pounds of drag"? Simple, it depends on how much effective area your pilot chute has. If your pilot chute has an "Effective Area of 5 Sq. Ft. then you must be going fast enough to develop 4 "Q" or 4 pounds of Dynamic Pressure. 4 x 5 = 20. If your pilot chute has 2 feet of effective area then you will need 10 pounds of Dynamic pressure or a little longer in free fall befor you bag extracts. You method will run us into hundres of dollars my method is considerably simpler and cheeper. Additionally you must instrument you dropped load to measure rate of decent. I'll make the book. You tell me the pilot chute size and type and weight and drop heigth and I will predict the time.

Attached please find an Excel Spread Sheet set up with the imbedded math and instructions for how to test a pilot chute. I call this the "Free Drop Method". All that is required is a high place from which to drop, a scale to weight the pilot chute and a timer with which to time the decent. Video is a good idea to confirm timing. If you only wish to directly compare (a Side by side race) pilot cutes they must weigh the same. If you fill out the spread sheet it will do the math for you and the weights do not need to be the same. Share your results and comment here. I have also forwarded copies of this procedure to the PIA tech committee for consideration. Have fun, JS

I remember Para-Flite would set their toggles so that you could not stall the canopy without re-setting them. Other companies have gone the other way so as to impress you with the performance on that first jump. The truth is that you can't set the toggles at the factory. Toggle settings will vary with wing loading and density altitude. Experienced jumpers know that if they normally jump at low elevations and they go to high elevations their flair point will change. It will change from season to season. That is why you should check your stall point on every jump just after you clear the air. Flairing past the stall point is not a good idea as you loose lift and the point of greatest lift is just before an impending stall. What good is horizontal drag when you are plumeting vertically?