Cutter location and time to pack opening

[df8m1 19]

With the recent incident where the reserve failed to deploy in time, I was thinking about the issue with the location of the cutter, and the time it takes for the reserve container to open.

By design they are intended to open from the out side in (initiated by pin extraction), and a cutter located below the flaps, makes the container have to open from the inside out, and that takes more energy and results in a delay in container opening.

If the cutter is located anywhere else than bellow the free bag, there is a possibility of the reserve being locked in the container should the cutter fail to cut the loop and pinch it. Given that is the case, why not put the cutter on top of the reserve flap, between the pin and the flap?

At first glance placing the cutter on the same side of the flap as the pin would allow a cutter initiated opening to be just as fast as if the pin was pulled because the container is allowed to open as designed regardless of the method of opening.

I have been thinking about cutter design lately because I am designing one, and I am thinking of making a concept cutter that will go between the pin and the top flap. Additional benefits may be that the pin will be better protected from damage with the body of the cutter to support it and protect it, and it would help keep the pin from being pushed out from rubbing against the plane. The external cutter would allow inspection as well.

Now the combination would create a little more bulk under the cover flap, but until I make one, I don’t know how bulky it would be. I thought I would mention this idea to get some feed back from riggers, and if any manufacturers want to weigh in, that would be great to.

The idea of a reserve not deploying in time after an AAD firing is totally unacceptable and defeats the reason for having an AAD in the first place. If moving the cutter to the where the pin is takes some delay out of the equation, I think it is worth looking at.

[theonlyski 3]

You're also exposing the cutter cable to more damage. I will put money that more cutters are damaged in rigs where the cutter goes above the PC.

Not to say they don't get damaged below the freebag, but I'd bet there's less of them that are.

"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

[df8m1 19]

Quote

You're also exposing the cutter cable to more damage. I will put money that more cutters are damaged in rigs where the cutter goes above the PC.

Not to say they don't get damaged below the freebag, but I'd bet there's less of them that are.

You are correct that the cutter cable will not be covered by the container flaps. The type of cable used is very important given that, for example, the cypres cutter would not be a good choice to use for a top mounted cutter, as the plastic tail is easily broken and the solid wire cable is brittle.

The cutter that I would design would have a stranded wire cable that is better for repeated flexing, with braiding and foil shielding. Additionally there would not be a tail sticking out of the cutter to be broken.

None the less, everything has a plus and a minus to it. Durability of the cutter cable located outside the container flaps would have to be tested, and the results taken into consideration for the design of the cutter and its location.

Thanks for the feed back, keep it coming...

[f2t323 0]

QUOTE""If the cutter is located anywhere else than bellow the free bag, there is a possibility of the reserve being locked in the container should the cutter fail to cut the loop and pinch it. Given that is the case, why not put the cutter on top of the reserve flap, between the pin and the flap?""END QUOTE

(im quite new to the sport ,so please keep that in mind.)
Are you refering to the last reserve flap that the closing loop passes trough ...placing the cutter on top of the gromet and then having the pin sit on top of the cutter ???

if so ,i fail to see any advantage (if the cutter fails to cut and traps the loop).pulling the pin manually would do no good.

And if you have the cutter on top of the pin somehow ...same problem arises if the cutter fails to cut the loop and traps it .

my 2 cents worth ...which with the exchange rate is worth...

[pchapman 261]

Just wanted to make a correction to something that was said:

The Cypres cutter does use a stranded, shielded cable. The internal wires are also twisted for more physical and perhaps electromagnetic protection.

I was curious so just cut open an expired C1 cutter cable. While the wires are tiny, a view through a loupe confirms that there are lots of little wire strands within each of the two insulated wires, which are wrapped with a shield of more strands, within the cable overall.

[Edit:] I didn't check the C2 but doubt they made the cable worse.

If you want to argue that the Cypres cable is less beefy than the Vigil cable (whether or not that matters in practice), or that the C2 strain relief 'tail' is worse than the flexible tail on the C1, go right ahead!

[df8m1 19]

Quote

QUOTE""If the cutter is located anywhere else than bellow the free bag, there is a possibility of the reserve being locked in the container should the cutter fail to cut the loop and pinch it. Given that is the case, why not put the cutter on top of the reserve flap, between the pin and the flap?""END QUOTE

(im quite new to the sport ,so please keep that in mind.)
Are you refering to the last reserve flap that the closing loop passes trough ...placing the cutter on top of the gromet and then having the pin sit on top of the cutter ???

if so ,i fail to see any advantage (if the cutter fails to cut and traps the loop).pulling the pin manually would do no good.

And if you have the cutter on top of the pin somehow ...same problem arises if the cutter fails to cut the loop and traps it .

my 2 cents worth ...which with the exchange rate is worth...

I did a poor job of wording the initial post.

If the cutter is located bellow the free bag, if it fails to cut the loop, the reserve can still be opened by pulling the pin, however, should the cutter cut the loop, the container has to open from the inside out which is opposite of how it was TSO tested. But none the less, should the cutter pinch, the jumper can still open the reserve their self. In this configuration, the AAD has the least affect on the reserve operation should the pin be used to open the container.

Now, some manufacturers have moved the cutter above the free bag to help minimize the delay of pack opening when a cutter opens the container from the inside out. In this configuration should the cutter fail to cut the loop, the reserve will be trapped in the container. My thinking is if the cutter is going to be above the free bag to begin with, why not put it right under the pin so the container opens as it was TSO tested.

I am not saying that placing the cutter anywhere above the free bag is better than bellow in regards to the risk of locking the bag in the container. My thinking is, if the manufacturer has requires the cutter anywhere above the free bag, if you can take advantage of an opportunity to allow the container to open as it was tested, then why not?

If the cutter is below the free bag, the cutter can not lock the bag in the container, but the pack opening most likely will be affected because it is opening from the inside out. If the cutter is located bellow the pin, the bag could be locked in the container, but the pack opening time would be the same as if the pin was pulled. In any case, making a cutter that cuts the loop is critical. Given a cutter that will cut the loop, having it just bellow the pin would allow a faster pack opening then with the cutter at the bottom, because of how the container flaps open.

I still do not like how I worded what I am thinking, so if I have fallen short again, let me know. Also feel free to let me know what you think.

[ksaylor1 0]

Maybe I'm just not thinking about it correctly, but the way I see it, the spring-loaded pilot chute pushes the closing flaps out of the way the same way whether it's allowed to do so by the loop being cut or by the pin being pulled. Either one of those events just allows the spring to do what springs do. I'm having a hard time wrapping my head around the "inside-out vs. outside-in" argument. I would need some 1000 fps video to compare what the two look like. Maybe DSE can help us out?

Ken

[df8m1 19]

Quote

Maybe I'm just not thinking about it correctly, but the way I see it, the spring-loaded pilot chute pushes the closing flaps out of the way the same way whether it's allowed to do so by the loop being cut or by the pin being pulled. Either one of those events just allows the spring to do what springs do. I'm having a hard time wrapping my head around the "inside-out vs. outside-in" argument. I would need some 1000 fps video to compare what the two look like. Maybe DSE can help us out?

Ken

There are several flaps on a typical reserve container, and most of the time the grommets on each flap do not line up when packed. This results in the closeting loop zigzagging from loop to loop making close to 90 degree turns which has a lot of mechanical advantage to over come. This is very important to remember when the container is opened by cutting the loop from with in the container (bellow the flaps).

The loop is attached at the back of the container and as each flap is pulled over, the loop is threaded through it’s grommet. One by one each flap is pulled and the loop threaded through each flap’s grommet and the pin is inserted in the loop to keep the container closed.

When the pin is pulled, the top flap is allowed to lift off of the loop which allows the loop to move freely across to the next grommet, and when the next flap relaxes and lifts off the loop, the loop is relaxes and the process continues until the pilot chute is allowed to extend. It is important to note that when the pin is pulled, the grommets lift off of the loop and the loop is not “pulled thought” the grommets.

Something to keep in mind that you should be able to relate to is when you are closing your main container, after you pull the loop through a grommet, I bet you pull the pull up cord to the side, bending the closing loop at a 90 degree angle, and put your knee on it to hold it. You probably have noticed that pulling the loop to the side makes it easer to keep it from being pulled back in while you are threading the pull up cord through the next flap. There is a mechanical advantage that is created when you pull the loop to the side, and a reserve closing loop can zigzag a couple of times on a reserve container, so that results in the mechanical advantage being multiplied with each zig and each zag.

When the reserve container is opened by pin extraction, the flaps lift off of the loop, allowing the loop to un bend and align with the next grommet that lifts off of the loop and allow the loop to un bend again and align with the next grommet, etc.

However, when the loop is cut bellow the flaps, the loop has to be pulled through all the grommets at the same time, and when the loop is ziged and zagged from grommet to grommet, there is a lot of resistance, just like with your main closing loop that you pull to the side. Instead of the flaps lifting off of the loop, the loop is pulled through all of them at the same time which requires a lot of power when the grommets do not line up, and because of the pin in the top flap, the force from the bottom up ward keeps the flaps tight against each other which is like you knee on your main loop.

When I say “opens from the inside out”, I mean that the cut end of the loop is pulled through the bottom flap first, then the next to bottom and so forth until the it is pulled though the second to top flap’s grommet. There have been reserve containers that have not opened at all after a clean cutter fire because of the mechanical advantage from long closing loop zig zaging from grommet across to grommet, which required more power to pull the loop through all the grommets than the pilot chute spring had.

Some rigs have their reserve grommets stack up inline, which IMOP is the best design regardless of whether a cutter is used or not.

Perhaps another way to think about it is to imagine a flower opening. The outer petals open first and the layer by layer until it is open. Now imagine a flower opening in reverse, with the outer petals opening last. It will take more power to push through all the petals than if they opened from the outside in.

Does that help you to picture what the difference is in pack opening from a pin extraction or cutting bellow the flaps? It is important to understand how your gear works, never be afraid to ask questions or challenge answers for that matter.

[jhh166 0]

I have a possible illegitimate fear - has a cutter on the top ever failed to cut the loop and pinch the loop therefore trapping the pilot chute and leaving the reserve ripcord rendered useless?

Has this ever happened? I must have gotten the idea from somewhere I admit it may be a stretch but it is enough to keep me from buying a container with the cutter placement on top of the rpc..

[GobbleGobble 0]

Yes.

[df8m1 19]

Quote

I have a possible illegitimate fear - has a cutter on the top ever failed to cut the loop and pinch the loop therefore trapping the pilot chute and leaving the reserve ripcord rendered useless?

Has this ever happened? I must have gotten the idea from somewhere I admit it may be a stretch but it is enough to keep me from buying a container with the cutter placement on top of the rpc..

Yes, that has happened. That is why it is so critical to have a cutter that is designed for use in a reserve container and to cut the closing loop material. It is impressive to see a cutter cut a cable, but I have dikes that will cut cable very nicely, but will not cut 300 lb Spectra to save your life.

Your comment on choose of gear by design is why I think it is critical to completely understand how a container works, and the difference between the different containers prior to buying one.

More that not a decision is made because of how a particular container looks, or an instructor has one, which is fine as long as you know how it will work with an AAD for instance, as the instructor may not have one in his rig so the location of the cutter didn’t factor into his decision.

I had the benefit of being able to watch the DZ rigger repack reserves at the end of the day, and that allowed me to see the differences in design, how AADs were installed.

[gowlerk 1,903]

If you are thinking of putting a device outside, on the top flap, perhaps some kind of pyro charged pin puller can be devised. I'm fairly certain this was looked at and rejected about 20 years ago, but maybe fresh eyes can see this problem differently.

Failing that a pin that incorporates a cutter would seem logical. But of course it would require unprecedented co-operation with container makers.

This would likely be the largest change in thinking since cones were replaced.

Always remember the brave children who died defending your right to bear arms. Freedom is not free.

[df8m1 19]

Quote

If you are thinking of putting a device outside, on the top flap, perhaps some kind of pyro charged pin puller can be devised. I'm fairly certain this was looked at and rejected about 20 years ago, but maybe fresh eyes can see this problem differently.

Failing that a pin that incorporates a cutter would seem logical. But of course it would require unprecedented co-operation with container makers.

This would likely be the largest change in thinking since cones were replaced.

John Sherman is very pro pin pusher, and I may be making some prototypes for him to play with.

Personally I like the idea of just using the pin, but in the same breath I remember when the pins were braking and the thought of that makes me break out in a cold sweat, so I as much as I like the pin puller or pusher idea, I am more for a totally separate method of pack opening as a back up.

Each person will have their own preference, and I think it is good to look at everything as everything has pros and cons to it, as well as things to be learned from development efforts.

[woppyvac 0]

I have a hard time seeing any benefit from the pin and cutter being in contact with one another. I imagine a scenario where I have a main mal with a skyhook and wonder how the routing would be hindered because it would add additional packing mishaps with routing of the RSL/Skyhook Lanyard. I imagine a scenario where I have no RSL/Skyhook and the pull force need to slid the pin over the cutter and out of the loop would be increased or halted because of friction etc. Simply put you'd be adding more potential mishap opportunities with the manual/rsl/skyhook pin extraction process. Just my observations - it you can design something beyond my vision that'd appease those worries than rock n' roll!

Woot Woot!

[Southern_Man 0]

Quote

When I say “opens from the inside out”, I mean that the cut end of the loop is pulled through the bottom flap first, then the next to bottom and so forth until the it is pulled though the second to top flap’s grommet. There have been reserve containers that have not opened at all after a clean cutter fire because of the mechanical advantage from long closing loop zig zaging from grommet across to grommet, which required more power to pull the loop through all the grommets than the pilot chute spring had.

Your theory makes logical sense but I would be interested to see actual tests conducted so the differences (if any) could be documented.

"What if there were no hypothetical questions?"

[councilman24 36]

Current cutters are routinely damaged by careless riggers using various closing devices (crank tools). I think having the cutter above the last flap would make it more susceptible to damage and perhaps make using kneeling plates and other tools more difficult or impossible.

The short amount of loop left from a cutter above the bag is much less of a problem.

Two pyro pin pullers were marketed (if rejected, rejected by the users) for use on piggy back rigs with the Sentinel SSE MK2000, the MK2100, and the Mars FF-3 AAD's. One was a Sentinel option and used the full size cartridge in a remote location. The other was a 'micro' pin puller which fit under the pin protector flap and pushed against the loop. I'm not sure whether Sentinel marketed it or someone else. Sentinel soon left the market and neither were very popular.

I think you'll find little advantage and great resistance to a cutter just under the pin. Also you will have to accommodate the 'square' pins used in UPT and other systems.

Good talking to you at the Symposium.

I'm old for my age.
Terry Urban
D-8631
FAA DPRE

[df8m1 19]

This is the kind of feed back I was hopeing for. This was just an idea that popped up in my head and I thought I would put it out there to see if others come up with the same drawbacks as I did, or pointed out advantages that I did not think of.

I like being able to talk about ideas openly, I think it gets people thinking about how their gear works and may learn something they did not know.

We are all in this together, when any gear fails a jumper, it affects us all. I have many legal pads full of good ideas at the time, which after time thinking about it, were abandoned... This is the creative process...

[df8m1 19]

Quote

Quote

When I say “opens from the inside out”, I mean that the cut end of the loop is pulled through the bottom flap first, then the next to bottom and so forth until the it is pulled though the second to top flap’s grommet. There have been reserve containers that have not opened at all after a clean cutter fire because of the mechanical advantage from long closing loop zig zaging from grommet across to grommet, which required more power to pull the loop through all the grommets than the pilot chute spring had.

Your theory makes logical sense but I would be interested to see actual tests conducted so the differences (if any) could be documented.

If I remember correctly, cutters were located bellow the free bag as a standard practice, but there was a 4 way that went low and all their AADs fired, but none of their reserve containers opened at all. It was attributed to a long closing lop that zigzagged back and forth, and possibly less spring force from the loop being long.

The result was some manufacturers tested different cutter locations to try to prevent that from happening with their containers, hence cutters are in several different places depending on the container.

There is a cutter / container compatibility test that the manufacturers use to evaluate the time from cutter activation to container opening. However it does not take into consideration the pack job ageing over the 180 day cycle.

[DigitalDave 0]

I know virtually nothing about rigging, but I've always wondered why there is a cutter in the first place. It seems like some sort of spring loaded, or explosive pin puller would do the same job without the worry of having to cut the loop. Or possibly some quick release lock on the bottom of the loop ..

I assume there is some technical reason that cutting the loop is better than extracting the pin.

[df8m1 19]

Quote

I know virtually nothing about rigging, but I've always wondered why there is a cutter in the first place. It seems like some sort of spring loaded, or explosive pin puller would do the same job without the worry of having to cut the loop. Or possibly some quick release lock on the bottom of the loop ..

I assume there is some technical reason that cutting the loop is better than extracting the pin.

The Cypres was born as the result of a reserve pin being bent to the point were it could not be extracted, and a fatality resulted.

By design, opening the container by means of severing the closeting loop provided a secondary method of pack opening that did not use the pin.

There are several different methods that have been patented to sever the closing loop over the years, but the cutters are used for other applications and were small and available.

I am talking with John Sherman about developing a pin pusher that he wants. Perhaps that will end up replacing the cutters, but personally I like having a separate method of pack opening should the pin brake or be damaged. Each person will have their own preference.