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what are acceptable reserve extraction forces

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I did a search and the thread that I found had no really useful information, so I am asking here. USPA and PIA issued an advisory recommending that the force required to extract a freebag from a rig while simulating a total malfunction be tested.
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2) When a reserve parachute is due for a repack, each owner should put his rig on (fully adjusted with the main parachute packed to simulate a total malfunction) and, in the presence of his rigger, pull the cutaway handle and reserve ripcord and have the rigger observe the pilot chute launch. Following this, with the aid of the rigger, carefully place the harness and container on a flat surface (or perhaps on someone else’s shoulders) and have the rigger extract the reserve freebag from the container by the bridle. Any anomaly to a normal, unrestricted pilot chute launch and freebag extraction should be thoroughly investigated and documented by the rigger and reported to the equipment manufacturers and PIA’s Technical Committee. Use this opportunity to ask the rigger any questions about the equipment and obtain a working knowledge of the parachute system.


so my question is what is an anomaly to a normal freebag extraction? How many pounds (or kilos, I can do math) of force should it take to extract a freebag from a rig.

I'm not looking to start one of those name calling pissing contests here, I just want to know what riggers feel is acceptable and what constitutes an anomaly.......

Thanks y'all

Pete Draper
Pete Draper,

Just because my life plan is written on the back of a Hooter's Napkin, it's still a life plan.... right?

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I've packed a few reserves, and never had one that I could lift the container up while extracting the freebag. Generally they will fall out if you pull it while standing up...

I will be packing a tight Mirage friday, I'll check to see the extraction forces with the main still packed (simulating a total)
"I may be a dirty pirate hooker...but I'm not about to go stand on the corner." iluvtofly
DPH -7, TDS 578, Muff 5153, SCR 14890
I'm an asshole, and I approve this message

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please let me know, I have had a few incidents recently that I would consider an anomaly, I have written to the manufacturer but the weekend here is Fri/Sat and they are just getting in to work as I'm leaving, so I haven't heard anything yet. I don't want to post anything negative until they've had a chance to see and analyze the info. But I would like to know what other professional in the field consider normal/acceptable
Pete Draper,

Just because my life plan is written on the back of a Hooter's Napkin, it's still a life plan.... right?

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I receive the anomoly reports sent to PIA. All 3 or 4 that we've gotten.[:/] We'd like to hear about things also. BUT the first call should be to the manufacturer if a rigger has a concern.

That being said my next comments are my own and not those of PIA or the Rigging Committee.

In discussions with some manufacturers they indicate that picking up the rig by the reserve bridle doesn't necessarily mean that the extraction force is too high. Especially if the main is still in the rig.

In my asking folks, including amny riggers involved with PIA, most riggers seem to automatically remove the main before opening the reserve. My skeptical nature lead me very early on when I started rigging Vectors (not II's or III's but ones) and other rigs with integrated riser covers (the main concerning feature) to always pull the reserve with the main packed if it was given to me that why. I've had some not so great launches and found the issue with the Quasars by doing this.

Many of the rigs pre Vector had some sort of staging mechanism, often an elastic loop holding the kicker flaps closed with a needle fold of the bridle. So, until the bridle was fully stretched out and tensioned the free bag couldn't come out. The new rigs were described as staging the deployment by the container design.

Some manufacturers do say the free bag should fall out. Be sure to ask if that is true with the main still closed.

What's an anomoly? Is it different than the other six rigs of that type you've packed. It is more than x lbs? And here is where you either insert a reasonable number or one from the manufacturer. What's reasonable? The lowest number I've ever seen quoted for the drag of a PC is 65lbs. Remember if the main is still in it's likely a high speed situation. If the main is out the extraction force may/will be less.

Manufacturers are working on gathering data to try to provide more guidance.
I'm old for my age.
Terry Urban
D-8631
FAA DPRE

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A lot of people here are saying that Jump Shack is a company that makes products from "the past", but If we have to objective, they are the only company that came up with document like this.
"My belief is that once the doctor whacks you on the butt, all guarantees are off" Jerry Baumchen

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A lot of people here are saying that Jump Shack is a company that makes products from "the past", but If we have to objective, they are the only company that came up with document like this.



...........................................................................

"Jump Shack got it right the first time ..." thirty years ago, but they have not done many updates since.
Whatever criticism you may level at Jump shack - and John Sherman - I may not always agree with them, but I still respect them at the end of the day, because John Sherman takes the time to research "stuff" - in detail - before he changes anything.
John is one of the few engineers working in the parachute industry. John started as an automotive engineer back before mini vans existed, and later transferred his expertise to the skydiving industry.
I may not agree with all of his decisions, but I still respect him at the end of the day.
Any time John Sherman talks, I listen.

P.S. I have also had the pleasure of working with Manley Butler, Sandy Reid, Mickey Cottle, Tom Clausen, etc.

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i am curious of this question myself, i have a reserve in my container that the manufacturer says will fit but describes it as a tight fit. Does this mean the reserve extraction will be slower than a reserve of a snug fit???

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>the manufaturer says will fit but describes it as a tight fit. Does this mean
>the reserve extraction will be slower than a reserve of a snug fit???

"Tight" and "snug" are generally the same thing.

In general:

If the extraction force of the reserve is such that the bag is retained before the PC gets to full extension, and then releases the bag, then reserve extraction forces are appropriate. Worst case for retaining the bag is probably deploying your reserve on your back; the rig should not release the bag until the PC starts pulling on it. Worst case for releasing the bad is probably a low speed cutaway; the rig should release the bag as soon as you have fallen any significant distance away from your main.

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If the extraction force of the reserve is such that the bag is retained before the PC gets to full extension, and then releases the bag, then reserve extraction forces are appropriate.



That's the part that concerns me Bill, "and then releases the bag" if I can (with the main in as a total mal sim) pick the rig up by the reserve bridle, then swing it through 720 degrees and not extract the freebag/reserve, is it a cause for concern, or would the pilot chute generate enough drag to extract that puppy? When is a tight fit too tight? When testing in the loft, how many pounds of pull force should I have to exert to be able to be happy that in an aad fire at < 1000 feet the freebag would release in time?
Pete Draper,

Just because my life plan is written on the back of a Hooter's Napkin, it's still a life plan.... right?

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That's the part that concerns me Bill, "and then releases the bag" if I can (with the main in as a total mal sim) pick the rig up by the reserve bridle, then swing it through 720 degrees and not extract the freebag/reserve, is it a cause for concern, or would the pilot chute generate enough drag to extract that puppy? When is a tight fit too tight? When testing in the loft, how many pounds of pull force should I have to exert to be able to be happy that in an aad fire at < 1000 feet the freebag would release in time?



I think that would probably be too tight for my comfort.

I would try to have someone don the rig, lay down (simulating a belly to earth position) and tie a slip knot on the bridle, then a scale on it, and see how much force it takes to get it to come out.

I could see how some rigs wouldn't want to release easily if pulled directly up (towards the yoke) but I can't see how it would hold if pulled back (straight up from the backpad).
"I may be a dirty pirate hooker...but I'm not about to go stand on the corner." iluvtofly
DPH -7, TDS 578, Muff 5153, SCR 14890
I'm an asshole, and I approve this message

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I could see how some rigs wouldn't want to release easily if pulled directly up (towards the yoke) but I can't see how it would hold if pulled back (straight up from the backpad).


Actually I did that! Got my trainee to lay down wearing the rig, then attached a scale to the bridle and started pulling at about a 30 degree angle. At first he started to slide across the floor (he weighs 140 lb) and the scale crept up to 40 lbs before the rig gave up the freebag....
Pete Draper,

Just because my life plan is written on the back of a Hooter's Napkin, it's still a life plan.... right?

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I could see how some rigs wouldn't want to release easily if pulled directly up (towards the yoke) but I can't see how it would hold if pulled back (straight up from the backpad).


Actually I did that! Got my trainee to lay down wearing the rig, then attached a scale to the bridle and started pulling at about a 30 degree angle. At first he started to slide across the floor (he weighs 140 lb) and the scale crept up to 40 lbs before the rig gave up the freebag....



I would ask the MFGR if that is acceptable. I personally think that's way high... but the MFGR might know something about the construction of the PC that could allow it to easily pull more than that. Then remember, it could be sub terminal, so the PC wont load as much right off the bat.

Tough call... how was the bulk distribution on the packjob? Did you see a way you could reduce the bulk a bit in the area it was binding?
"I may be a dirty pirate hooker...but I'm not about to go stand on the corner." iluvtofly
DPH -7, TDS 578, Muff 5153, SCR 14890
I'm an asshole, and I approve this message

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I personally think [40-pound extraction force is] way high... but the MFGR might know something about the construction of the PC that could allow it to easily pull more than that. Then remember, it could be sub terminal, so the PC won't load as much right off the bat.



How much drag does a pilot chute generate in a normal deployment and in a subterminal deployment?

Mark

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22 pounds?

I cannot remember where I read it, but 22 pounds comes to mind.
The logic means that friction should retain the heaviest reserve (read tandem PD 360 reserve), preventing it from falling out before the reserve pilot chute is definitely pulling. Most pilot chutes will pull 80 pounds or more.
If friction is not consistent, then manufacturers add bungee staging loops (see Strong Dual Hawk and UPT Sigma) to ensure that the pilot chute is pulling more than 22 pounds before the freebag can be extracted from the container.

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so I repacked the rig and put it back on Raju and had him lay down on the floor. He pulled the reserve and the pilot chute launched just fine. I tied a slip knot in the bridle, stood on a chair (much to the amusement of the fire-fighting trainees in the next room) and pulled upwards at 90 degrees with my scale. This is still a tough extraction and the scale hit 38 lbs before the rig gave up the freebag. It also required a sustained pull, in other words the scale didn't get to 38 and the bag just popped out, during the pull (from about 30lbs onwards) it required a sustained pull to have it rotate upwards and out.

I will be reporting this to the manufacturer for their opinion, but would welcome other opinions from technically minded riggers......
Pete Draper,

Just because my life plan is written on the back of a Hooter's Napkin, it's still a life plan.... right?

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22 pounds?

I cannot remember where I read it, but 22 pounds comes to mind.
The logic means that friction should retain the heaviest reserve (read tandem PD 360 reserve), preventing it from falling out before the reserve pilot chute is definitely pulling. Most pilot chutes will pull 80 pounds or more.
If friction is not consistent, then manufacturers add bungee staging loops (see Strong Dual Hawk and UPT Sigma) to ensure that the pilot chute is pulling more than 22 pounds before the freebag can be extracted from the container.



isnt 22 pounds the max pin extraction force? rather than the reserve pc force
regards, Steve
the older I get...the better I was

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I personally think [40-pound extraction force is] way high... but the MFGR might know something about the construction of the PC that could allow it to easily pull more than that. Then remember, it could be sub terminal, so the PC won't load as much right off the bat.



How much drag does a pilot chute generate in a normal deployment and in a subterminal deployment?

Mark



Don't know... figured the MFGR would. ;)
"I may be a dirty pirate hooker...but I'm not about to go stand on the corner." iluvtofly
DPH -7, TDS 578, Muff 5153, SCR 14890
I'm an asshole, and I approve this message

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I personally think [40-pound extraction force is] way high... but the MFGR might know something about the construction of the PC that could allow it to easily pull more than that. Then remember, it could be sub terminal, so the PC won't load as much right off the bat.



How much drag does a pilot chute generate in a normal deployment and in a subterminal deployment?

Mark



Don't know... figured the MFGR would. ;)



And that's really the whole point.

It has been quite some time since the USPA and PIA published the warning about tight reserve containers.

The manufacturers should have responded by doing all the testing and measuring and publishing the result for all to see.

If we build rigs that rely on the tightness of the container to stage the deployment, this information should be in the manuals for all to see.

To date, as someone else has mentioned, only Parachute Labs (Jump Shack) seems to have published anything.

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22 pounds?

I cannot remember where I read it, but 22 pounds comes to mind.
The logic means that friction should retain the heaviest reserve (read tandem PD 360 reserve), preventing it from falling out before the reserve pilot chute is definitely pulling. Most pilot chutes will pull 80 pounds or more.
If friction is not consistent, then manufacturers add bungee staging loops (see Strong Dual Hawk and UPT Sigma) to ensure that the pilot chute is pulling more than 22 pounds before the freebag can be extracted from the container.



isnt 22 pounds the max pin extraction force? rather than the reserve pc force



.........................................................................

Yes, 22 pounds does relate to maximum pull force on reserve ripcord pins, main deployment handles and cutaway handles, but I was trying to relate it to the weight of a reserve canopy.

I don't have the manual in front of me, but a vaguely remember tandem reserves weighing in the range of 22 pounds. A container should hold a 22 pound reserve until the reserve pilot chute is definitely pulling.

Most pilot chutes can easily pull more than 80 pounds.

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Most pilot chutes can easily pull more than 80 pounds.



How about at sub terminal speeds?
"I may be a dirty pirate hooker...but I'm not about to go stand on the corner." iluvtofly
DPH -7, TDS 578, Muff 5153, SCR 14890
I'm an asshole, and I approve this message

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Keep in mind that the forces can vary quite a bit, depending on whether the PC "snatches" the bag out as in would with a terminal deployment, or whether it is a slow, sustained pull, as would be more likely during a sub terminal deployment.

Something that is of much greater concern if there isn't much altitude to play with....

38 - 40 lbs though, seems quite high to me....
My computer beat me at chess, It was no match for me at kickboxing....

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How much drag does a pilot chute generate in a normal deployment and in a subterminal deployment?

Mark



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

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What's an anomoly? Is it different than the other six rigs of that type you've packed. It is more than x lbs? And here is where you either insert a reasonable number or one from the manufacturer. What's reasonable?



In the absence of any kind of a range of data from the manufacturer so far, I decided to use Terry's Criteria. It just so happened I had 5 more of these rigs to inspect so I tested the extraction forces required on each. The least was 22 lbs and the highest was 32 lbs all at an angle of about 85 degrees from the horizontal.

I am pretty confident that the rig that aroused my curiosity in the first place was an "anomaly" - of the 5 only 2 were capable of being picked off the ground by the reserve bridle and only 1 of those could be swung around, and then only 1.5 revolutions before releasing the bag. The first rig was swung through 720 degrees and showed no signs of giving up the bag until manually/forcefully extracted. Going to wait another couple of days to get a clearer response from the manufacturer though.......
Pete Draper,

Just because my life plan is written on the back of a Hooter's Napkin, it's still a life plan.... right?

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