PC in tow... for real this time

[pilotdave 0]

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
http://www.skydivingmovies.com

[freeflir29 0]

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Cost to replace the kill line: $15.

Much cheaper than a cut away!!! Glad it turned out OK......Reaching back to pull on the bridle introduces a lot of possibilities for disaster. On the other hand you aren't the first person I have seen or heard of taking care of a PC in tow this way. As long as you walked away it's all good! "It's all about the BOOBIES!"

[rgoper 0]

you handled that the same way i would've. but never forget, try once, try twice, institute emergency procedures, i've heard of people spending too much time trying to clear this anomaly, it can sure burn up some altitude, plus it's a high speed partial malfunction. good job!
Richard
"Gravity Is My Friend"

[FallRate 0]

If this was a case of you jinxing yourself...Hmm, perhaps I should post a "fake" picture of myself being molested by some of the DZ.com women!
FallRate

[SkydiveMonkey 0]

I can give you a real one if you want
When you participate in sporting events, its not whether you win or you're loose, its how drunk you get.

[flyhi 24]

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If this was a case of you jinxing yourself...Hmm, perhaps I should post a "fake" picture of myself being molested by some of the DZ.com women!

Gotta think bigger than that;"I won the lottery". If that works, I can buy all the fake pictures of DZ.com women molesting me that I want.
flyhi
"To understand Mankind, you must look at its two root words; Mank and Ind."

[airann 1]

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"fake" picture of myself being molested by some of the DZ.com women!

Dude, be careful... its like voodoo... if you mess up a step shyt gets weird....
One time I wished for a motorcyle - I got a go cart
Then I wished for a Horse - I got a Burro and her baby burro. That damn near gave me a childhood complex, but I struck it up to the old saying "Ann is a little different"
So all I am saying is if you wish to get molested by the beautiful DZ.com women......
It might get messed up in the translation and you wind up with a bunch of Sheep and Clay.....
That is all I am saying.......
Ann ~ www.AirAnn.com
Anyone want a Kitten?

[bbarnhouse 0]

*thinking be careful what you wish for......
It only takes a little pixie dust......

[lippy 918]

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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.

Well that's what ya get for confusing me. I spent all day trying to figure out how you got that damb computer into your containerCongrats on saving your ass dave!
-I live like a poor man, so I can play like a rich one
Roger

[pilotdave 0]

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Reaching back to pull on the bridle introduces a lot of possibilities for disaster.

I can imagine some bad things that could happen, and I did get flipped onto my back which coulda been bad, but doesn't cutting away and pulling the reserve also open up a lot of possibilities for bad stuff like entaglements? The pilot chute in tow is just one of those malfunctions that it seems like we're taught to just hope it goes away. Nobody ever taught me to yank the bridle (although I read about it being done), but it seems to be a more "proactive" way of dealing with it than just cutting away (or just pulling the reserve). It's interesting that I chose to do it that way though. I never actually THOUGHT about reaching for the bridle. I just did it. I didn't really realize I had done it until after it was done. Dunno if that's a good reflex or a bad one, but I'm pretty happy now!
Dave
http://www.skydivingmovies.com

[SkydiveMonkey 0]

Yanking the bridal worked, so you must have done something right !! When you participate in sporting events, its not whether you win or you're loose, its how drunk you get.

[billbooth 10]

Pilotdave;
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

[pilotdave 0]

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
Dave
http://www.skydivingmovies.com

[AggieDave 6]

Bill,
Great post, you should cross post that in the G&R forum, so others who don't read this forum can get a chance to see it too.
A human cannonball, I rise above it all
Up higher then a trapeze, I can fly

[billbooth 10]

Pilotdave;

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