Is Your Hand Deploy Pilot Chute Correctly Made?

[billbooth 10]

Yesterday, I responded to a post from a jumper who had a pilot chute in tow. Someone suggested that I post it here too. Here is the string:
Subject PC in tow... for real this time Reply

Posted by pilotdave (Enthusiast) (Full Profile)
How ironic... My first jump after posting a fake picture of myself with a "PC" in tow, I had myself a real life pilot chute in tow. Always wondered exactly what I could/would do in that situation. Everything happened so fast I barely had time to think about it. I didn't cut away. I reached back, grabbed my bridle, and yanked. The bag came right out, but I flipped over on my back so I watched it come off. Canopy opened with enough linetwists that I could't look up, but that was fine with me. Linetwists cleared themselves and I landed normally. I had originally pulled at 3500. First time I looked at my altimeter I was at 2000 but I had been under canopy for a little while at that point. It's hard to judge but i'd guess the whole PC in tow lasted no more than 3 seconds.
I talked to the DZO about it and he suggested that maybe I need a new pilot chute. He checked the tightness of my closing loop and it was fine (after I repacked). I did one more jump, had a kinda delayed opening... But it opened again with linetwists (probably my body position as I turned to see what was happening that time). After that I brought it straight to the most experienced rigger there and he found the problem right away. My kill line had shrunk (I bought it used), so the PC wasnt inflating fully. The center of the PC, where the handle is, gets pulled down too far. Cost to replace the kill line: $15. I think I can afford that. Dave
Reply from Bill Booth:
What happened to you is getting more and more common. Although I hold the patent on the hand deploy pilot chute, I never charged anyone a royality to use it, and therefore never published construction details. I'm afraid this has led to some poorly made pilot chutes as people have copied, but not copied EXACTLY, my original design. As a matter of fact, last Sunday, a jumper came up to me, said that he was having "pilot chute hesitations" on his Vector, and asked me to have a look. His problem, it turned out, was the same one I've seen countless times before...His pilot chute was made by "God knows who", and made incorrectly.
I don't know about you, but one of the the scariest malfunctions I can think of, is a streamered main pilot chute that has enough drag to open your main container, but not enough drag to lift out the bag. What do you do? If you just lie there and wait, the ground may "rise up to smite thee". If you pull your reserve, your main is going to simultaneously deploy, and main/reserve entanglements are rarely much fun either. What to do...Easy, don't jump an incorrectly manufactured or adjusted pilot chute.
So, how can you tell if your hand deploy pilot chute is OK? First, some basic definitions. 1. Apex - The center of the fabric part of your pilot chute. 2. Skirt - Where the mesh and fabric meet. 3. Base - The center of the mesh part of your pilot chute. 4. Centerline - One or two pieces of tape, of fixed length, that lead from the apex to the base. 5. Bridle - A piece of tape, doubled in the case of a collapsable pilot chute, leading from the base to the deployment bag. 6. Kill line - A single piece of line, on a collapsable pilot chute only, that runs from the apex, through the center of the pilot chute, and down through the bridle to the pilot chute attachment point at the bag, or in some designs, to the apex of the canopy. 7. Support tape - 4 pieces of thin tape, sewn to the mesh, leading from the base to the skirt. 8. Bias - Simply put, the direction the mesh stretches the most (a diagonal line, at 45 degrees to the little squares that make up most mesh used in hand deploy pilot chutes). Sorry for all that defining, but if you don't understand those terms, you won't understand what comes next.
OK, now the easy part. If you want your pilot chute to always function properly, simply make sure, in the inflated state, that no part of the skirt is above the apex. In other words, make sure neither your centerline nor your kill line is too short. I pulled the apex on my hand deployed pilot chute for two reasons. 1. It makes them open faster. 2. It yields 11% more drag. However, IF THE APEX IS PULLED DOWN BELOW ANY PART OF THE SKIRT, THE PILOT CHUTE WILL NOT FUNCTION PROPERLY.
How do I check that? First cock you pilot chute like you would during packing. Now hold your pilot chute UPSIDE DOWN by the bridle at the base. Simultaneously pull downward on the apex (handle) and each support tape where it touches the skirt. The apex should be equal to, preferable slightly "below", but never "above" the skirt. (Please remember, the terms "above" and "below", in quotes, refer only to the "upside down" pilot chute you are holding in your hands for this test.) Now look how your support tapes are sewn to the mesh. If they are sewn "on the bias" your pilot chute is properly constructed. If they are not sewn on the bias it means that the mesh halfway between each support tape IS on the bias and will stretch more than enough to allow the skirt to get way "below" the apex. Try it. It's like a round parachute with several different line lengths. It simply doesn't work very well. This extremely common construction error might not let your pilot chute fully inflate, or in extreme cases, inflate at all. If your pilot chute is "borderline" when it is new, then things will get worse and worse as it ages.
Now to "adjusting" a correctly manufactured pilot chute. Kill lines are usually made out of Spectra (Microline). Friction generated during the collapse sequence causes heat, and Spectra SHRINKS when heated. This means that your centerline could eventually get short enough to prevent your pilot chute from inflating correctly. Use what you have learned above to recognize this situation, and correct it.
This is just a BASIC primer on pilot chute construction, and does not address several other important design considerations such as fabric and mesh choices, and how pilot chute size vs. the weight of your main canopy affects seperation velocity, snatch force, opening shock, and malfunction rate. More about these another time.Bill Booth
Dave replied:
Wow, excellent advice. Tried the test and the apex is nowhere near the skirt. It's inches above. The end of the hackey handle doesnt even reach the level of the skirt.
The support tape goes in the same direction as the lines of the mesh, not 45 degrees to it. You're saying this is improperly made? Do all "real" parachute manufacturers install the support tape 45 degrees to the mesh? Do I have some sort of homemade pilot chute? There doesn't seem to be any kind of tag or marking to tell me who made it.
Watching the pilot chute as i pull it down through the air and let it inflate, I can CLEARLY see that the apex falls below the skirt. Until my incident, I wouldn't have know this is unsafe.
The rigger I bought my rig from gave me a one year warranty on everything. If he hadn't been evicted from the DZ and his house, I'd get my money back. I am quite shocked he sold me potentially (or definitely) unsafe equipment. The good news is he's gone now and I don't have to deal with him anymore.
Thanks for the info! I'm sure I'm not the only person relying on posts like this to keep me safe in the future. Keep it up! Dave
Bill's reply:
Your pilot chute is "unsafe" if it doesn't deploy your main correctly. What is "correctly"? You want your pilot chute to open your container and the pull your bag away from your container quickly, but not too quickly. If your pilot chute accelerates your bag away from you too slowly you have the potential for line twists because of the extra time your unsymmetrical deployment bag is exposed to the slipstream, or a bag lock caused by your suspension lines actually "blowing up" above your bag and entangling with it. Not to mention taking more altitude than necessary to deploy. If your pilot chute accelerates your bag too quickly, you have the potential for inertial line dump, high snatch force (when the canopy hits the end of the lines and is decelerated back to your speed), slider rebound (where the slider bounces off the slider stops and your canopy starts its opening sequence with the slider a few inches down the lines. OUCH), and a generally disorganized opening, increasing your chance of malfunction.
The ideal separation velocity, that is the speed which the canopy is traveling away from you at line stretch, is 50 feet per second. An acceptable range is 30 to 70 FPS. If a pilot chute causes separation velocity outside that range, I do not considerate it "safe". How can you tell what your separation velocity is? You can look at a video of one of your deployments and count video frames at 30 per second. An acceptable time from container opening to line stretch is 0.45 to 0.75 seconds, or about 13 to 22 frames. Any faster or slower and you are "asking for it".
Separation velocity for any particular system depends on the size, material, and construction details of the pilot chute vs. the weight of the bagged canopy. You of course also have to factor in deployment speed, what your lines are made of, and how you stow them. A very large pilot chute, constructed as yours is, might be perfectly "safe" with a light canopy. The construction details I gave you make the most efficient use of materials, and yield the most consistent results over the most number of jumps. Of course, if you pull the apex down far enough, no pilot chute, no matter how large, will do its job. That's what the "kill line" is supposed to do, isn't it...pull the apex down so far that the pilot chute totally collapses?
Bill Booth
Post Extras:

[skybytch 273]

Thanks for reposting this Bill. I missed it in the other thread.
I just checked my p/c and it passes the tests. pull & flare,
lisa
[subliminal msg]My website Go Now[/subliminal msg]

[lazerq3 0]

Mr. Booth....Great post there however I'm not sure if you ever covered this but what are your opinoins or impression on the "Bungi " set up....I jump with a bungi and havnt had any problems so far. Just wondering what your feelings are on them!!
jason

[billbooth 10]

Jason;
The same basic construction rules apply to a "bungee" collapsible pilot chute. They, of course, have the advantage that you don't have to cock them after each jump. However, bungee pilot chutes have pretty much "lost favor" with the jumping community for several reasons. 1. They are hard to "calibrate" in the first place, that is open when you want, and stay closed when you want. 2. They tend to go out of calibration as they age (even temperature affects them). 3. They tend to re-open during the extreme swoops that are so popular today. Because people quit asking for them, we have not made one at the Relative Workshop for almost three years now.
However, if yours is working for the kind of jumping you do, I see no reason to change it. Just keep an eye on your bungee cord, and replace it before it gives you any trouble. But please be sure to use exactly the same style, diameter, and length of bungee cord as the original. I, for one, always liked the user friendly simplicity of the design. It just didn't work out in "real life".
Bill Booth

[riggerrob 643]

Bill,
Thanks for sharing our wealthy of knowledge.
Think I'll go lengthen my tired kill line.

[TEB6363 0]

Yes, Thanks Bill.
Great thread and information.
:::OK, Canopy is Open, No Traffic Around, .. Why are these "Extra" Lines Draping Down??, Damn!

[polarbear 1]

Good post. I have noticed that some kill line pilot chutes have a length of tape that is attached to the base of the pilot chute (not the kill line) and runs to the appex of the pilot chute. This serves as a sort of spacer; when you cock the pilot chute, this length of tape should be pulled tight. If the tape can't be pulled tight during normal cocking, the kill line is too short (assuming the spacer tape hasn't shrunk, which I don't think will happen).
Interestingly, I had a pilot chute where the kill-line was too long(even after it had shrunk). It wouldn't collapse all the way. It won't cause a malfunction, but it pissed me off that I payed (extra) for a collapsible pilot chute and it wouldn't collapse all the way. I've since added a bi-monthly kill-line check to my rig maintenence.

[KATO33 0]

Pilot Chute set up A-O-K
Thanks for the Info and the heads up Bill

[lazerq3 0]

Thanks for the info Bill!!!
jason

[pilotdave 0]

Quote

I have noticed that some kill line pilot chutes have a length of tape that is attached to the base of the pilot chute (not the kill line) and runs to the appex of the pilot chute. This serves as a sort of spacer; when you cock the pilot chute, this length of tape should be pulled tight.

Yep, mine has about an inch of slack in it and the kill line is stretched tight. Definitely a problem and I'm quite mad that a rigger sold it to me this way. I wish someone would write an article, or some kind of document, with all kinds of tips like this for inspecting gear. I'm learning more and more, but I don't know what to be looking for on most parts of my rig. When I can't trust an experienced rigger to inspect it properly, I'd like to know how to do it myself (without becoming a rigger).
Dave
http://www.skydivingmovies.com

[billbooth 10]

Dave;
As you know, I have been doing just that recently, at least in regard to the three ring release and hand deploy pilot chutes. I could write volumes about reserve pilot chutes, toggles (Yes, toggles. You would be surprised how dangerous some toggle set-ups are.), riser covers, bridle protection, reserve cover flap tuck tabs and a dozen other subjects. But quite frankly, I'm beginning to get a lot of grief from some of my staff. Their complaint goes like this: "Bill, you have spent 35 years of nearly endless experimentation and observation to gain what knowledge you have of parachute systems. Now you're simply giving it away to people who aren't even our customers. It's your job to make our equipment the best in the world. It is not your job to give the results of hundreds of thousands of dollars of research to our compeditors for free. If you want jumpers to benefit from what you know, let them buy a Vector." In a way they're right, but at the same time I'm tired of jumpers being hurt or killed because of improperly manufactured or maintained gear. I have two children, a staff of 50 people, and an ex-wife who depend of me for their livings. What should I do?

[AndyMan 7]

Quote

What should I do?

Keep posting here, keep giving us your wisdom. Figure out a way that will tell you how many of us buy your gear. I suspect you might be impresed...
_Am
ICQ: 5578907
MSN Messenger: andrewdmetcalfe at hotmail dot com
AIM: andrewdmetcalfe
Yahoo IM: ametcalf_1999

[skycat 0]

Dave do a search of this Forum and swooping and canopy control, Hooknswoop has posted several articles on how to check different parts of gear, includeing pilot chutes and brake lines.

[riggerrob 643]

Bill,
Please continue sharing.
Please continue feeding T.K. Nick, the rest of your employees and your children, but screw your ex-wife.

[mgaillar 0]

Sounds like a double-edged sword, but here's my take. I am relatively new to the sport (60 jumps). I was fortunate enough to start skydiving at a dz that has fantastic instructors. I always felt well-informed when going through my student progression. I now skydive with confidence in my abilities to make sound judgments on the ground, in the aircraft, and during the skydive itself. I was taught basics in equipment maintenance and terminology. In short, I have a good foundation to build many floors upon.
In february, I had the great fortune to meet you, Bill, during Skydive U's, Search. You gave me a 2+ hour tour of your facilities. You relinquished gobs of information about your products with solid research to back it up. I even learned just how passionate you are about this sport with your continued goal of saving one more life.
Later that evening, I sat with you at the Perfect Spot with several on-lookers surrounding you and your laptop. You showed video clips and PPT presentations of your work. I learned a tremendous amount about rigs, not just RWS rigs. And with the history of RWS and "other" manufacturers, I never once heard you bash any of the competitors. Passion and professionalism.
My point in all this?? I continue to educate myself from your choice to share competent information. That makes me a safer skydiver. Your benefit, albeit micro in this case, is my order that was place for my first rig last month. I can't wait to receive my new V3!
Thank you, Bill!!
Matt
http://www.skydiveorange.com

[polarbear 1]

From a jumpers perspective, let me just say how truly aggrivating it is to sometimes not be able to find good information (especially technical info) on parachutes. The information shared by knowledgeable manufacturers can be invaluable.
Having said that, I also recognize the plight of the business man.
Anything you choose to share is appreciated.

[steve1 5]

Bill,
We all really appreciate what you have shared with us so far in this forum. I hope you continue this in the future, but at the same time you need to lookout for yourself. I don't know a lot about the buisness world, but some competitors can be really cut throat. So most of us know you can't share everything with us and that's fine. Thanks again for your help. Steve

[SkydiveMonkey 0]

Thanks Bill. What you have already shared with us has been great !! Helps the average skydiver (like me Danger could be my middle name. But it's Paul.

[rapper4mpi 0]

Bill, first I want to say that the new Vector 3 M-series is incredible. I am so impressed with the construction, quality, and comfort. The attention to detail is amazing. Gwen, Mark, and Niklas should all be given raises as they do a wonderful job with customer service. As an intructor myself, and being in the marketing advertising field, I do have one comlaint....Your web site and literature is a major injustice to the quality of your product. Just about every other manufacterers web site is light years ahead of RWS. One could argue that you guys are spending your time building and developing containers, and I think that is great! But please spend some time putting more useful information on your site to a potential buyer. The internet is a powerful thing as shown clearly here. Thank you for making a wonderful product that I will promote anytime!
-Rap

[skymedic 0]

Quote

I never once heard you bash any of the competitors. Passion and professionalism

funny thing about this....when RWS, Mirage, and Sun Path were at the winter expo at SDC......Mark from RWS never said a bad thing about eather of the other two....Bill H. from Mirage never said a bad thing about the other two.....I wish the same could be said about the sunpath guy a talked too....
hence the reason I no longer have a javelin.......
profesionalism goes a long way....even in a small "cottage industry" like skydiving....
Cheers....vasbyt
marc
"I have no fear of falling, I just hate hitting the ground"-The Badlees...

[rendezvous 0]

Well, Bill, by your sharing a part of your knowledge or atleast enough so that people can skydive safely the benefit of it in my opinion goes to RWS. I'm new to the sport and for a guy like me
the finer aspects of engineering from one container to another mean very little unless someone like you with experience and credibility comes and explains them, and that would want to be look at products that you deal with more closely than others. So my point to RWS would be that if I was hear you speak and share your knowledge base, my chances of buying a Vector would be more since I would know the people behind it more, else they are all the same to me. When it comes to buying containers, the advice that most of the instructors give is pretty much that all containers are round about the same, atleast for beginners like me looking for something. Those who do have some personal choices don't have compelling enough reasons to
influence my decision. When a person like you comes and talks and shares, thats what gives me the reason for looking at your product over what would otherwise would be a price driven choice. I guess it should be looked at as some healthy advertising for a change.

[billbooth 10]

Rap;
I agree. Relative Workshop's website sucks. That's probably because I hate almost everything about computers, which is probably because I know next to nothing about computers. I have, however, recently hired a website designer and told her to build a website the way we build a Vector. I can't wait to see how it turns out. The way I'm forced to spend money on computers, software, and the people to keep it all up and running, I'm beginning to think that soon, all of us will be doing nothing but selling computer services to each other, and no useful work will get done in the world anymore.
Bill

[rapper4mpi 0]

Bill I'm glad to see that you guys are onto this. Although some people may have access to a gear shop, some of us don't. So the only way to get our information is from the companies themselves. I would suggest checking out every other manufacterers site, seeing what they do well, and what they don't and making yours better! I can't wait to see it. If you ever need customer testimonials, just let me know.
-Rap

[Hooknswoop 19]

Bill-
I had the pleasure of attending your presentation last year at PIA about your new Sigma tandem rig.
I own a V304 and love it, absolutely zero complaints about the rig. Absolutely solid rig. I would buy another one if you made one w/ the same size reserve container, but much smaller main container. My canopy swims in the main container of the 304.
Hook

[billbooth 10]

Derek;
As you know, the V304 Micron is the smallest rig we make. However, I am glad to announce, for all jumpers with a highly developed death wish, such as you, that we are drawing up the plans for a V303 as I speak. When we started Vector III's in 1994, the smallest we made was a V343. So You see, I left plenty of room to go smaller. I hope this stops soon. I only have three smaller numbers left. If you guys don't cut this out, we may have to go negative. Bill