aad cutter differences

[netslide 0]

Does anyone know of any differences between cutter assemblies from the different manufacturers?

They all appear to be the same generic concept. I know the connectors are different but besides that.

Also us there any reason why I couldn't use a different brand cutter on an aad device?

Are aads tsod in any way? I mean all the parts would be approved items just in new confuguration.

[wolfriverjoe 1,340]

netslide

...Also us there any reason why I couldn't use a different brand cutter on an aad device?

Are aads tsod in any way? I mean all the parts would be approved items just in new configuration.

No, AADs aren't "approved" by the FAA in any way shape or form.

BUT...

The requirement in part 105 is "in accordance with manufacturer's instructions"

I would think that using (for example) a CYPRES cutter with a Vigil control unit would be in violation of that.

"There are NO situations which do not call for a French Maid outfit." Lucky McSwervy

"~ya don't GET old by being weak & stupid!" - Airtwardo

[piisfish 135]

Blade Shapes are different from a manufacturer to another. Number of blades too (oscillate between 0 and 1).

Saying that they are all basically the same concept is saying a Cessna 172 and a Boeing 777 are the same concept. For example one manufacturer has used over 7 cutter versions over 15 years.

scissors beat paper, paper beat rock, rock beat wingsuit - KarlM

[JerryBaumchen 1,046]

Hi Joe,

Quote

"in accordance with manufacturer's instructions"

A question; does not that section refer to maintenance of the unit(s)? Something along the lines of, 'Shall be maintained in accordance with mfr's instructions.'

Jerry Baumchen

[piisfish 135]

Are aads tsod in any way? I mean all the parts would be approved items just in new confuguration.your logic is flawed. Re-read your question until you understand why

scissors beat paper, paper beat rock, rock beat wingsuit - KarlM

[netslide 0]

There are always updates to a particular component but what I am asking is can a superior part be substituted for an out of date or obsolete part without having to deal with any recertification? Say a ma ufaturer quit making a certain part but the was a similar and updated component that would do the same function without any major modification

[wolfriverjoe 1,340]

JerryBaumchen

Hi Joe,

Quote

"in accordance with manufacturer's instructions"

A question; does not that section refer to maintenance of the unit(s)? Something along the lines of, 'Shall be maintained in accordance with mfr's instructions.'

Jerry Baumchen

Hi Jerry,

Yes, but I would think that "mixing and matching" parts from different manufacturers would fall under that.

I have to say, that if I opened up a rig for an I&R and saw some sort of "cobble job" like that with the AAD, I would not sign off on it.

As always, I could certainly be wrong. And if so, I welcome correction.

"There are NO situations which do not call for a French Maid outfit." Lucky McSwervy

"~ya don't GET old by being weak & stupid!" - Airtwardo

[skytribe 16]

wolfriverjoe

I have to say, that if I opened up a rig for an I&R and saw some sort of "cobble job" like that with the AAD, I would not sign off on it.

I know that the cutters do work (or at least it can be demonstrated easily). That said, the connectors are different and would need to be modified to make the cutters and AAD's compatible.

That said, I'm with wolfriverjoe on this one, that is if I had a rig turn up with cutter/AAD that were from not from the same manufacturer, I'd let the customer know that I wouldn't be packing it. It is just not worth the liability for untested component combinations.

[mark 102]

skytribe

I know that the cutters do work (or at least it can be demonstrated easily). That said, the connectors are different and would need to be modified to make the cutters and AAD's compatible.

Do we know that the voltages for self-test are the same for different cutters?

-Mark

[skytribe 16]

Maybe not all cutter/AAD combinations but Kirk at para concepts knows much more. He was very knowledgeable about the various cutters as a result of the Argus AAD Issues with cutters.

As with most technology things, it may be possible to hack cutters together with different control units but these frankenAAD's I think would have very little benefit and much more risk. Risk to the user, rigger and various manufacturers - so I don't see this as even a vaguely remote possibility for happening in the real world in the US.

[df8m1 19]

mark

***I know that the cutters do work (or at least it can be demonstrated easily). That said, the connectors are different and would need to be modified to make the cutters and AAD's compatible.

Do we know that the voltages for self-test are the same for different cutters?

-Mark

As a "budding manufacturer" lol... I think I might be able to provide some information on this subject.

Disclosure: My team and I are developing an advanced AAD for military and sport applications. I can only speak for my company's philosophies on design, functionality, and standards. Also forgive any spelling or grammar as I am in my mom's hospital room trying to be distracted from the reality of the moment.

OK... Lets start with AADs and a TSO. Unlike aircraft auto pilot computers and the like, there is no TSO that "directly" relates to a skydiving AAD. I stress "directly" as if one was to consider an AAD as a flight computer, then there are some design and manufacturing standards what could be applied, but to be clear, as of today, there is no correlation between any aviation electronics and an AAD.

If an AAD were to be TSOed in a manner consistent with aircraft flight computers, there would be component qualification requirements, redundancy requirements, software qualifications and requirements etc.. that would most likely triple if not quad droopel the cost of an AAD.

Personally, I am in favor of some kind of AAD standard, but in regards to performance assurance rather than hardware/software design, but that is a different topic from the OP's question..

A Cutter's NO-FIRE (hence forth NF), and ALL-FIRE (hence forth AF), power specs:

All of the pyro cartridge initiators used for parachute loop cutters use a bridge wire to initiate ignition of the propellant. There are many different bridge wire resistance and AF/NF power combinations, such as the standard 1.2 to 1.8 ohm, 1A/1W NF bridge wires that usually have 3W AF ratings. AADs do not have enough battery to last 4+ years and fire a 1A/1W NF at end of life and lower temperatures. Some special purpose cartridges have bridge wire resistances bellow 1 ohm and AF currents bellow 200mA. The cartridge will not fire at or bellow the NF speck and they will fire at or above the AF speck. However it is possible for the initiator to fire between the NF and AF current ranges.

Although AAD manufactures tend to keep their specks secret (and I will respect that as I know want some of them are so no names), the ones I am aware of have bridge wire resistance between 1.2 and 1.8 ohms off the top of my head that has had very little sleep in the past 36 hours lol. One may be .8 Ohms. NF currents range from 100mA to around 180mA/200mA and AF currents from 500mA to 800mA. In addition to the NF current speck, our hardware design has a NF safety so to speak that provides an additional level of protection against unintended firing.

The NF speck is relates to how sensitive the cartridge is to RF, Static, etc.. The AF speck relates to how much battery power is needed to fire the cartridge. Each AAD has a cutter detect method that checks the circuit from the AAD, through the cutter, and back to the AAD. This check usually passes a slight amount of current through the cutter to check the circuit continuity. All of the AADs that I am aware of have only one firing circuit and simply tie two cutters together. The potential problem with doing that is if one cutter of the pair is damaged, or even cut off, the presence of the other cutter will result in a test pass. Or, if the circuit was designed for one cutter, using two cutters from a different AAD could burn the firing circuit out.

As a comparison, our AAD design has two separate cutter circuits, which when used with a single cutter, are tied together creating some what of a redundancy (except they both use the same power source) and with a dual cutter configuration, each cutter has it's own firing circuit and cutter detection so if one cutter is damaged, it will detect that and fail the self test. I would not expect any combination of AADs and AAD cutters to result in a cutter fire during the self test, but when one mix matching parts, anything can happen.

Blade design:

Everyone knows that Airtec uses a single edge blade cutter, were as Vigil uses a cylindrical blade, as did Argus until they went out of business because their cutters failed to cleanly cut the loop. M2 had a unique piston type cylindrical blade (hard to describe) but at PIA I believe that I heard M2 switched to a single edge blade like Airtec. We are also using a single edge blade in our cutters. The material that AAD closing loops are made out of is very difficult to cut, and in addition, the metal grommets can drop down into the saddle that is created when a hole is drilled perpendicular to a radioused surface, which can result in the grommet contacting a circular blade. A single edge blade has proven to be the best so far at cutting reserve closing loop material IMO.

Mix and Match:

I can only assume that the OP has an Argus and is thinking about using an available cutter instead of the Argus cutter. If that is the case (regardless of the AAD/cutter combination) keep in mind why one puts an AAD in their container. Now think about the AAD firing circuit design specks, and cutter cartridge specks that one does not have. Just because an AAD will fire a cutter from a different manufacturer in a test chamber, it does not mean it will do that when the batteries are at the end of their life and/or are cold. In reality, the firing circuit design and cartridge design go hand in hand to create the greatest chance of successful operation when called upon in worst case conditions. Without truly knowing the design specks of both the cutter and AAD, one can not know where that specific combination of parts falls in the tolerance range. It may be way over in the "over kill" side, but it can just as easily be in the "barley operational in ideal conditions" side.

In regards to a rigger packing a "home built" AAD/cutter combo in someone else's rig... If your rigger says "sure no problem".. find another rigger.. just my opinion...

Over All Cutter Design:

Although I believe over 25 years of performance has proven that a singe edge blade loop cutter is better than a circular blade loop cutter, the over all cutter design differences have plusses and minuses associated with them respectively.. Most if not all AAD manufactures have a minimum closing loop tension speck, meaning they require a minimum amount of tension to assist the cutter in severing and releasing the loop. I have witnessed this effect first hand when we were testing the main deployment system on a spring loaded main rig we use for AAD testing. We use two AAD closing loops, one going through the cutter and regular rip cord, and the other one is a safety that has a ripcord that is mounted on the left hand side. The safety prevents the main from opening if the AAD were to fire un expectedly during a test. Safety is a must....

When we used a standard main spring loaded pilot chute, we noticed a hesitation after firing the cutter (no named), so we switched to a newer reserve pilot chute (which had a more powerful spring) it popped as it should when the cutter was fired. IMO, a cutter should not require any loop tension under any circumstances, in order to cleanly separate the loop.

Design Evolution:

As was pointed out, there have been many changes to cutter designs over the years, some relating to the pyro cartridges and some to the cutting portion. Also there are different materials used for cutter bodies and blades, as well as hardness levels. Even Blade piston diameters vary as do piston seals that are used.

I really caution anyone who is thinking about using parts for an AAD that are not authorized by the OEM.

[mxk 1]

David, I'm assuming you've taken apart cutters from various manufacturers. Do you have any photographs you can share? I'm just curious what their internal construction looks like.

Is there anything fundamentally different about Vigil cutters that would make them safer than what Argus had, or are the basic problems with cylindrical blades still the same?

[pchapman 261]

I posted some pics of a Cypres cutter in 2011, when I opened one up to test fire it:
http://www.dropzone.com/cgi-bin/forum/gforum.cgi?post=4099034;

(The video I made of firing a "sawed-off Cypres" cutter at plywood isn't up on the web any more. But I still have a bunch of Cypres 1 cutters sitting around...)

[netslide 0]

This information really gives me some things to think about, my intentions of learning more on this subject is due to my wanting to design my own personal aad system there are several features that I would like to develop but have yet to see them in a commercial unit. As far as the software goes that tends to be a specialty of mine but I am trying to figure out a few of the hardware items. I have had good success so far in making some software adjustments to my astra unit. But in my chamber tests some still need work. I have a cutter test probe but am wondering how a real cutter would react if any differently

[gb1 2]

Hello PC. Just love the cypress test you performed. My question is: Will a Cypress cutter cut a single loop clean, with no tension on the loop?

[pchapman 261]

gb1

Hello PC. Just love the cypress test you performed. My question is: Will a Cypress cutter cut a single loop clean, with no tension on the loop?

Airtec does claim "Superior cutter design, has always cut the loop cleanly, even with no tension on the loop". I never actually tested that configuration with one loop as I figured they were being truthful about that!

(I know there was more concern about that for the Argus, in particular for the earlier less hardened cutter designs.)

[betzilla 56]

Quote

I have had good success so far in making some software adjustments to my astra unit.

Well that's sketchy...

[RiggerLee 61]

First let me say that I think your little project is really cool. There are several of us on here that are basically mad scientist. The guy above is a good example. His company Freefall Accessories...

https://freefallaccessories.com/

builds every thing from a very nice line of altimeters to the old pin pullers we used on our suborbital rockets and every thing in between. They are leading the charge in a whole new generation of AAD's with far more processing power and sensors. But they are just the first. Eventually we will see new generation AAD's from all the old companies.

Personally I love to tinker with stuff. Things become really dangerous when I become board and have spare time on my hands. So I totally get you wanting to tinker with an AAD project. To really do some thing interesting though I think you'll have to start from scratch. And in a very technical since I don't see any thing stopping you from building your own AAD and even jumping it. That is if you can convince some one to pack it for you. To the best of my knowledge no manufacturer even approves an AAD for their rig. There is no list of what they say is OK, because they don't want to touch the liability. And to the best of my knowledge the Argus is the only AAD that any manufacturer has disapproved. I'm speeking of the US. So technically there is to the best of my knowledge nothing stopping you from building your own and even selling it to others. What I don't think you grasp is the enormity of the project. Beyond the liability the reason that no one has ever felt the need for an approval or testing program or any type of certification is that, at this point, every one who has undertaken this has been a large well funded enterprise with a good testing program. They've all had glitches but that's normal. What's amazing is how few and how small they have been.

Today we are getting into the age were any body can tinker with this stuff. There has been discussion of the idea of an open source AAD project. In theory between off the shelf components and 3D printers some one with a little basic skills could make there own AAD. The problem is that these are not toys. You don't just laugh with your friends when they break, blow up, catch fire, or have a melt down. Your life may depend on it. It could save you, but it could also kill you. An AAD can KILL YOU. Further more an AAD can KILL THE PEOPLE AROUND YOU. You may not be old enough in the sport to remember when you could not get on a load if you had an AAD on your rig, but I do. People would not jump with you. The reliability of the second generation of electronic AAD's ie. Cypres, changed all that. But the original selling point of the cypres was that it was hidden. No one would know that you had it in your rig. I really don't want to go back to that. To really do this right is a pretty big endeavor. There are all kinds of failure modes that you probable have not thought of. I say that having recently listened to a lecture on failure modes of an AAD at PIA from one manufacturer. And another two years earlier from another. And these are people that have been building them for decades. If you wanted to start a company and do this. I'd say go for it. The market is wide open. The changes that are coming will make all the existing manufacturers obsolete. All you need is ten million dollars in funding. But I don't see any way for you to develop and test an AAD as a hobby project. And I don't think I would want to gamble my life jumping around you with it out side of the controlled conditions of a testing program. And I don't think any one would want to gamble a million dollar air craft on your project. And an AAD can take down an aircraft. Canopy deployed on climb out can take that tail right off.

My concern is that if these open source projects go forward it will erode the trust that has built up in this industry over the years. It would force the industry to start approving or disapproving installations. That would change the liability and not in a good way. Home made AAD's would quickly be outlawed, and by default others approved. It's a can of worms that no one really wants to open.

Lee

Lee
[email protected]
www.velocitysportswear.com

[skydiverek 54]

gb1

Hello PC. Just love the cypress test you performed. My question is: Will a Cypress cutter cut a single loop clean, with no tension on the loop?

Yes, it will, many videos of that on YouTube:

https://www.youtube.com/watch?v=wXq39D8ACTA


.

[skytribe 16]

RiggerLee

To the best of my knowledge no manufacturer even approves an AAD for their rig.

http://strongparachutes.com/library/Documentation/Tandem/Approved%20DHT%20Components.pdf

http://strongparachutes.com/library/Documentation/Tandem/Approved%20TNT%20Components.pdf

Well there's two containers that have Approved component lists which include AAD's.

[RiggerLee 61]

Good example. And that's interesting because a lot of people have resisted doing some thing like this. I think it dates to when Strong made AAD's mandatory on their tandems. I don't think they wanted people going out and putting old poorly maintained FXC's and things in them just to for fill the requirement. The trade off is that it adds one more form of liability that they might face in court one day.

Lee

Lee
[email protected]
www.velocitysportswear.com

[JerryBaumchen 1,046]

H Lee,

Quote

Good example.

See the attached for some other examples.

Jerry Baumchen

PS) This is just something that I have cut & pasted for future reference.

PPS) Oopsie, had the wrong attachment; this one has a number of entries.

[df8m1 19]

mxk

David, I'm assuming you've taken apart cutters from various manufacturers. Do you have any photographs you can share? I'm just curious what their internal construction looks like.

Is there anything fundamentally different about Vigil cutters that would make them safer than what Argus had, or are the basic problems with cylindrical blades still the same?

I would rather not comment on "existing" competitor's products. I take exception to Argus as they have exited the market without addressing the well established cutter issue. I do not recall any Argus AAD malfunction problems, and some are still being used. I will say that I would be pleased if all the AADs went to single edge blades in their cutters.

Lee brings up some good points regarding the potential trend for "hobby" AAD engineers playing with AADs and causing some potential catastrophic results, and with that regulation that the end user will ultimately have to pay for. Not to say that some standards would not necessarily be a bad thing, but most regulations are written by people who do not know, or understand anything about what they are regulating and are usually emotionally motivated... Not a good combination...

I think that the liability has a self regulating effect as if a manufacturer puts out a bad product, it will cost them in court.

To the OP... Of all the AADs that are currently available to play with... Why the hell would you use an Astra??? couldn't find anything older or more out of date?? lol (that was sarcasm)... That explains you asking about up grading components.. My first thought is to hack an Argus, or cypress perhaps which would be a better platform IMO.. My second thought is you mention that you are a programmer, and if you have enough hardware background to be "up grading" out dated components on someone else's platform, then as Lee mentioned, why not just make your own AAD?

I am curious as to what you are trying to do? Are you trying to do something better than Airtec and Vigil are doing? Again keep in mind that the AAD that you have chosen to use was designed and built decades ago. Don't get me wrong, if all you intend to do is dummy drops with it, and you have a static line safety so the container can not open until the static line pin has been removed, then have at it, just be careful, dropping something from a plane is not as easy as one would think. You don't want the dummy going through a roof of a house or a car, or on a road, etc...

Additionally, as Lee pointed out, one's ability to author good code does not an AAD logic expert make lol.. It all comes down to what you are trying to do I guess.

I started the "open source AAD" thread because I was tired of hearing from all the coders out there saying how easy it would be to build a better AAD lol... Need less to say it did not go anywhere :)

I have two professional and well seasoned programmers, one works with the operating system and firing code, and the other handles the mass data transfer, storage, and analytics. The systems programmer has experience with autonomous vehicles and missile guidance systems and he said that our AAD firing algorithms are more complex than anything he has worked on. Failure modes will keep you up at night lol... What ifs will give you nightmares..

Does FXC no longer support the Astra? Can you not get cutters for it?

[df8m1 19]

JerryBaumchen

H Lee,

Quote

Good example.

See the attached for some other examples.

Jerry Baumchen

PS) This is just something that I have cut & pasted for future reference.

PPS) Oopsie, had the wrong attachment; this one has a number of entries.

Jerry,

Is my understanding correct that the container manufacturers are really only approving the cutter and not the AAD as a whole? Don't they do their cutter fire tests and make a judgment as to if the cutter being tested for compatibility interferes with the TSOed operation of the reserve?

Strong Enterprises is the only exception that I am aware of, as I know they actually drop tested tandem vigils and the first bunch went in. As I recall Vigil said the cutter AF speck was too high and the firing circuit was not able to fire them. Vigil resolved the issue. Does anyone know if any other container manufacturer actually tests the ability of an AAD that is applying for approval, to fire as advertised?

[RiggerLee 61]

I don't think that's the kind of testing they are doing.

Their first concern is that the AAD not interfere with the normal deployment mode, ie. when they pull the rip cord manually.

There was a project back when we first started to understand that the cutter firing the loop caused the container to behave differently. What they were really looking at was container design and cutter placement. It was the cutter under the PC vs. cutter above the PC argument, and beyond that how the container it self behaved. In the past Airtec and others did their own testing on containers and they decided things like cutter location. We started to realize that we needed a broader metric of testing over the full spread of containers that a manufacturer builds, not just a single example that had been sent to Airtec years before. Over that time fundamental things had been changed in some of the designs. For example there were several iterations in the Javelin container since the early 90's when airtec tested it. So PIA and the manufacturers kind of came up with their own "testing/certification" program. It's a good size metric of test in a number of conditions looking at sensitivity to a number of factors. But it's all about the container design. And I think it's all table top. Don't remember the details. Point is it was focused on the container not the AAD or the cutter. I think they were looking a using a little hook knife style devise in place of the cutter. It was potentially a lot of test. As far as AAD "certification testing" goes that's the only program I recall. The argus was more a "Holy shit, it wont cut a limp loop!" thing. And based on the location of some of the cutters, people spazed. And rightly so. If it interferes with the normal mode... Then it violates the TSO. That's been the argument all along. The airworthiness is based on normal testing. Not the AAD. Argument for letting them put it in is that it can't hurt any thing and does not interfere with the "normal mode".

Lee

Lee
[email protected]
www.velocitysportswear.com