Freebag testing and development

[Garnettz 0]

Freebag line deployment.
I have been asking around senior riggers who have been around for many evolutions in equipment. What I want to know is how was the system developed. We have come to universally trust the freebag line deployment system with the side pocket where lines are just pushed in.

From what I have gleaned so far Paraflite did the testing way back when but I want to know details. Would appreciate ideas or information on the testing and problems that may have been experienced during the testing.

Garnett E414 R19

[skydiverek 54]

From Bill Booth, talking about the bridle pockets and Para-Flite testing as well:

"Let me clear up one myth right now. The free bag system WILL NOT pull your reserve bag out of its container in the event of a horse shoe malfunction. A horse shoed 16 foot long, 2 inch wide, free bag bridle generates only about 2 pounds of force on the bag at terminal velocity. Most reserve canopies weigh over 5 pounds, not counting force required to extract them from the reserve container, especially if the main container is still closed. What the long wide bridle will do, however, is stabilize the bag, (if you reach back and throw it out of the container) so that it won't tumble through its own lines as it deploys.
So, if you ever experience a horseshoe malfunction of your reserve, don't just lie there and wait to hit the ground, sit up until you feel the reserve bridle hit you in the back of the head, reach back and pull on it until the free bag is out of the container, and then let go. The drag of the bag itself, helped out by the bridle, will then carry it to line stretch. I put out a film about this about 15 years ago, but a lot of people seem to have forgotten."

and

"The pull generated by a 2" reserve pilot chute bridle in a horseshoe configuration is about 2 pounds. I published a video recording that fact about 20 years ago. Reserves weigh at least 5 pounds. Plus, all modern reserve containers add a "containment" force to keep the reserve bag in the container during pilot chute hesitations, to prevent out-of-sequence deployments (which, by the way, have killed several jumpers using older containers without this safety feature). So, it usually takes at least 10 pounds of force to remove a reserve bag from its container. Therefore, a horse-shoed reserve bridle does not generate nearly enough force to pull your reserve bag out of its container. This is a good thing, because it prevents out of sequence deployments due to pilot chute hesitations.

The basic problem with two reserve pilot chute systems like my Vortex (which I developed years before the Catapult, but did not market) or the Catapult itself, is that they cannot tell the difference between a pilot chute hesitation (very common) and a reserve horse shoe malfunction (very rare). So, the second pilot chute on these systems can easily pull the reserve free bag above a hesitating primary (spring loaded) pilot chute, allowing that pilot chute to get into the lines below the free bag, thus totaling your reserve. So, the Catapult system actually encourages out of sequence reserve deployments, which as I said above, is a very bad thing. I tried to solve this problem with the Vortex, but was unable to do so. The Catapult does not solve it either."

and

"The freebag system only "Works" if the bag is first "ejected" from the container by some force OTHER than the horse shoed bridle. On the Paraflite dummy drops, this force was supplied by the tumbling dummy. Once the bag is out of the container (at terminal) it will blown upward by its own drag. A horse shoed 2" bridle only supplies about 1 pound of drag. Most reserves weigh at least 5 pounds, and it takes at least 10-15 pounds to pull the bag out of most modern containers. This is a good thing because of the likelihood of reserve pilot chute hesitation. If your bag falls out of the container while your pilot chute is hesitating, and gets above that pilot chute, you could be in a lot of trouble."

and

"In my tests, a horse shoed freebag bridle pulls only about one pound at the freebag end. Pockets on the bridle don't pull much more, and certainly not enough to pull a freebag out of a modern container. This is good, because the last thing you want during a pilot chute hesitation (common on internal spring-loaded pilot chute systems) is for your bridle to pull your bag out of the container and above the hesitating pilot chute. Reserve totals are rarely fun."

and

"With your main container (and riser covers) closed, it can easily take over 15 lbs. of pull to remove your reserve bag from the container. It takes a pilot chute of about 13" finished diameter to do that. Pockets on the bridle won't generate nearly that much drag. But the most important thing to consider, is that the second pilot chute can't "tell" the difference between a reserve horse shoe (which is very rare) and a reserve pilot chute hesitation (which is very common). Ask yourself this simple question: "Do you really want your reserve bag pulled out of the container by the secondary pilot chute while your main pilot chute is hesitating right above?" Sounds like a recipe for an entanglement between the heavy, spring loaded primary pilot chute, and your reserve lines to me."

and

"Question: So why do we have 2" bridles in the first place?
Answer: Para-flite started it over 20 years ago. When they came out with the first square reserve, the Safety Flyer, they decided to "tinker" with a lot of other things too. The "free-bag" with its bungee "safety stows" and 2" wide "anti-horseshoe" bridle was the result. The Safety-Flyer was marketed with the Swift container system which had no pocketed corners. As a result, when you pulled the ripcord, the bag would simple fall out of the container. When they drop tested this combined system with a built-in "horseshoe" malfunction and a tumbling (unstable) dummy, the bag would simply be ejected from the container because of centifugal force (angular acceleration) and be pulled to line stretch by the force of the relative wind on the bag. The super long bridle allowed the lines to unstow, and the freebag allowed the canopy to open. The 2" width merely provided stabilization so that the bag did not tumble through the lines as they unstowed.

The anti-horseshoe system worked in those test conditions. However, as stated earlier in this thread, it will not work with a stable jumper using a modern piggyback system. The long, wide bridle has persisted out of inertia. i.e. No one wanted to go against an existing, "proven" system. Even though, I suspect, the wide bridle helps create and lengthen pilot chute hesitations, because of the drag it creates in the burble right above a stable jumpers back on initial pilot chute launch.

I have made one change recently, however. I had to shorted the bridle a bit to make the Skyhook work correctly. I kept the 2" width because of the stabilizing effect I noted above."

[riggerrob 558]

They experimented with a variety of line stow methods before settling on the line stow pocket and Safety-Stow.

Para-Flite did all the early development work because they were the first to certify square reserves during the late 1970s.

During the early 1980s, Gargano (Hobbit) and Security (X-210R) both introduced square reserves with diapers. Riggers were already familiar with diapers as they had been standard on new round reserve sew during the previous decade. They used Type 4 diapers with all the lines stowed in MIL SPEC rubber bands. Diapered squares could be quickly packed in to any existing container without modification, buying free-bags, etc.

Only the Racer factory continued to experiment with free-bags.
The first few Racer Free-bags were closed with MIL SPEC rubber bands and all the remaining lines were also stowed in rubber bands.
Then they made Racers with Safety-Stows (and line stow pockets) for a couple of decades.
Around 2000(?) the Racer factory introduced the Speed Bag with an extended closing flap that has holes for a dozen MIL SPEC rubber bands. All the rubber bands are locking stows so there is no line stow pocket.

Most free-bags are optimized for the low-speed edge of the envelope with only two locking stows and the lines laying loose in a pocket. Pockets are the best way to deploy lines at low speed. Just ask your local BASE jumpers or canopy formation guys.

[JerryBaumchen 1,047]

Hi Rob,

Quote

Most free-bags are optimized for the low-speed edge of the envelope with only two locking stows and the lines laying loose in a pocket.

I have no argument with your thinking.

However, every main canopy 'stowless' bag on the market ( that I am aware of ) uses a line stowage pouch in which the lines are merely 'stowed' like a reserve free bag. I would estimate that all of these 'stowless' bags are being used about 98% of the time at terminal.

'Stowless' bags using a line pouch are currently built with the line pouches being closed with velcro, magnets & tuck tabs. I have never heard of a problem with any of them.

Anyone else????

Some interesting history here for a lot of the newer jumpers.

Jerry Baumchen

PS) And the last that I knew, Strong Entr were using Type 12, Cond U for their reserve bag bridle line material.

[riggerrob 558]

....... last that I knew, Strong Entr were using Type 12 webbing, Cond U(n-coated) for their reserve bag bridle line material.
..... Correct!
And Racer uses (3 inch wide) Type 4 webbing for free-bag bridles. I suspect that is to reduce the number of different types of webbing in inventory.

[accumack 13]

The Safety Flyer was several years before the the Swift system which was Swift reserve, Swift Main and the Swift harness container The first lightweight production system approximately 16 lbs there were other one offs that other people built but not a production system and not ram air canopies.
You have few errors in your statements. I worked for Para_flite and was involved with the development along with Jake Brake, Dick Morgan and Elek Puskas. We ran many tests on each part of the system and know the reasons for why things were done the way they were.

[JerryBaumchen 1,047]

Hi Rob,

Quote

Cond U(a coated)

A typo?

Cond U is uncoated & Cond R is resin coated.

Quote

to reduce the number of different types of webbing in inventory.

Quite often the reason why.

Jerry Baumchen

[JerryBaumchen 1,047]

Hi mack,

Quote

We ran many tests on each part of the system and know the reasons for why things were done the way they were.

I for one would like to know anymore that you might want to provide.

Jerry Baumchen

PS) All of that was way before the internet so the rumor mills were running rampant.

[accumack 13]

the early Reserves were retained in the container by a bungee loop and needle fold of the 2" bridle. i agree most of the current reserve containers restrain the reserve. i do not believe this is a good thing as more than a few people have gone in due to a reserve that will not leave the container without excessive force when a main is still in its' container. I cannot recall anyone that died as result of a unretained reserve. Para-Flite reserves opened fast than any other reserve out there at the time as result their pack volume was higher due to the added strength required.
I am appalled at the length of time current reserves take to open and the number of people that have died even with an AAD that fires.

[pchapman 261]

Accumack, do you know anything about the development of the velcro-closed line stow pouch?

That seems to me a novel development for square canopy deployment, although I don't know all the history. Rubber bands or fabric channels had typically been used to restrain lines on previous rounds and squares in bags and sleeves.

[darkwing 4]

At the very considerable risk of disagreeing with Bill Booth, I will say that I have a clear memory of lengthy one-on-one discussions with Elek Puskas, and of seeing video showing deployment of a reserve with an intentionally horseshoed bridle. I recall very specific discussions with Elek about their intentional design for that specific issue.

It was also central to ParaFlite's design of their rig, the Swift, with a very open reserve container system, without the modern container design "feature" that holds on to the reserve bag even when the container is open.

To be clear, I am not saying that Bill Booth is mistaken, but I am saying that ParaFlite believed differently.

-- Jeff
My Skydiving History

[pchapman 261]

Accumack PM'd me and in conversation offered some additional info which I'm sure he wouldn't mind sharing:

Quote

The line stow pouch was to reduce whipping of the lines and line twists verses stowing we had lots of film shot by Randy Deluca showing the lines whipping and causing the bag to spin. For the main we had the free pack strap that had 1 stow in a rubber band and the rest of the lines coiled in the pack tray. after a year or 2 there were some reported line container side flap entanglements and that was stopped. The pocket with velcro solved the line flap problem. It was one of the simpler Items for the 1st ram air reserve. There have been a couple of improvements over the years in the way the velcro is sewn on the bag.

The bit about coiling the lines in the main container makes sense. Poynter's book 1 has some info on how to add loops to a main deployment bag, to allow stowing all of the lines, and not just the locking stows. Rigging organizations also came out with warnings about the coiling practice.

[JohnSherman 1]

Quote

And Racer uses (3 inch wide) Type 4 webbing for free-bag bridles. I suspect that is to reduce the number of different types of webbing in inventory.

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.

[riggerrob 558]

Over the years we have heard 3 different opinions about bridle length on free-bags.

The first opinion held that the bridle should be longer than reserve suspension lines to allow the reserve to open even if the reserve pilot-chute wrapped around an ankle.
For comparison, PD176 reserve A lines are 10 feet long.

Circa 2000, Bill Booth told us that you only need a 13 foot bridle to correctly sequence a Skyhook MARD.

Now Mr. Sherman tells us that we only need an 8 foot bridle.

Hmmmmm?
Do we hear a fourth opinion?

[accumack 13]

Para-Flite's original bridle was 2" cotton it was changed to 2" dacron polyester because cotton would cause the repack cycle to go back to 60 days because it was a natural material. This was shortly after the repack was lengthened from 60 days for canopies and containers that consisted of synthetic materials.

[JohnSherman 1]

Quote

Over the years we have heard 3 different opinions about bridle length on free-bags.

The first opinion held that the bridle should be longer than reserve suspension lines to allow the reserve to open even if the reserve pilot-chute wrapped around an ankle.
For comparison, PD176 reserve A lines are 10 feet long.

To that I say "Why" isn't the "Free Bag" going to release from the canopy no mater where it is, on the horseshoe?

Quote

Circa 2000, Bill Booth told us that you only need a 13 foot bridle to correctly sequence a Skyhook MARD.

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.

[hajnalka 0]

I think the bigger question is: How are the PC and bridle going to extract the freebag from the rig.

[Deyan 31]

riggerrob

Over the years we have heard 3 different opinions about bridle length on free-bags.

Circa 2000, Bill Booth told us that you only need a 13 foot bridle to correctly sequence a Skyhook MARD.

Just a little correction Rob. It's 12 ft total. 5 ft between the RPC and the Skyhook and 7 ft between the Skyhook and the free bag.

"My belief is that once the doctor whacks you on the butt, all guarantees are off" Jerry Baumchen