Mission Impossible: Newbie Question on AADs

[Michele 1]

So, the Sentinel/Elizabeth threads recently have got me thinking about AADs. No, not the debate "should I or shouldn't I". I already have made that decision.

My question is this: how exactly does one work? No, I don't mean how it works for the computer/sensor/thingy to determine to deploy, but rather, once it determines to deploy, what are the mechanisms it triggers (etc) to get a canopy over your head?

And how does the RSL figure into it?

And just to make your job actually impossible, get me to understand it! LOL, my poor non-mechanical mind is already cringing at the daunting prospect of understanding this.

Thanks!

Ciels-
Michele

~Do Angels keep the dreams we seek
While our hearts lie bleeding?~

[Jessica 0]

It cuts the reserve closing loop, which releases the pin, which allows the pilot chute to deploy. That's it! Beautiful in its simplicity.

Skydiving is for cool people only

[CanuckInUSA 0]

And to add to what Jessica has already said, the RSL is not a factor in the AAD's deployment.

Try not to worry about the things you have no control over

[drenaline 0]

hey Michele, its quite simple how a AAD works.

The AAD has a cillinder wich has a cutter inside. The cylinder is a lil bit longer than the size of a 9mm bullet and thin like a 22mm bullet, it has a hole where you pass the closing loop and when it triggers what it does is cut the reserve closing loop and the reserve PC spring does the rest of the work.

-------------------
| O <---cutter----| |==========
-------------------

you pass the bottom of the closing loop in the hole O. Inside the lil thing is a cutter that will cut the closing loop when its time. I can't find the manual to explain how it triggers but if am not mistaken it triggers like a bullet inside a gun, when the computer says its time to go, it sends a spark wich triggers the gunpowder and shots the cutter thru the cylinder making it cut the loop.

If am not mistaken there is another system of AAD that what it does is pull the pin like a RSL.

The reserve static line is linked with the main risers (the lil metal thing that holds the ring) and ruted to the reserve pin. When you pull red the main will fly taking one end of the RSL and when it stretchs it will pull the pin of the reserve.

AAD works with the closing loop and RSL works with the pin.

HISPA 21
www.panamafreefall.com

[Michele 1]

You're right, of course, about the RSL not figuring into the AAD firing. D'oh, I got that all bolluxed up. You'd think I'd understand better, but that's what this place is for, right? LOL...sigh...

I think what I am trying really hard to be delicate about and still ask, (and obviously not accomplishing) is this...could a partial pull on the reserve handle create something which would not trigger the AAD to fire...? Does that make any sense? And I know that was not delicate at all, and I apologize in advance should someone get upset at the question. Please no-one flame me for asking that.

Ciels-
Michele

~Do Angels keep the dreams we seek
While our hearts lie bleeding?~

[drenaline 0]

Quote

could a partial pull on the reserve handle create something which would not trigger the AAD to fire...?

Th AAD will trigger when the speed and altitude are correct, it doesn't cares about the pin or the closing loop, its independant. I have seen a case where the person having the emergency pulled the reserve pin and by the time the canopy was leaving the container, the AAD fired.

before I get flamed: the team mate saw him pull the silver before he saw a reserve out so we concluded that.

HISPA 21
www.panamafreefall.com

[skybytch 259]

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Th AAD will trigger when the speed and altitude are correct, it doesn't cares about the pin or the closing loop, its independant.

This is true for the Cypres, and, IIRC, the Astra. Not sure if it's true for the FXC 12000 or Sentinel though.

[indyz 1]

Quote

I think what I am trying really hard to be delicate about and still ask, (and obviously not accoplishing) is this...could a partial pull on the reserve handle create something which would not trigger the AAD to fire...? Does that make any sense? And I know that was not delicate at all, and I apologize in advance should someone get upset at the question. Please no-one flame me for asking that.

Disclaimer: I am not an experienced skydiver, nor a rigger.

If I recall correctly, only the Cypres and Astra cut the reserve closing loop. I believe that FXCs and Sentinels pull the pin mechanically. I have no idea how a partial pull on the reserve handle would affect these units.

D'oh, Lisa beat me to it. I should just skip fact-checking next time.

[drenaline 0]

from the Para Gear catalog:

Quote

FXC Model 12000
The function is to withdraw the ripcord pin (main or reserve) in the event the parachutist reaches a preset altitude with a rate of descent exceeding 65 fet per second. Under normal conditions the unit does not operate.

I think as a safety thing they all must be independent, or else it can fail. This is just a wild guess.

HISPA 21
www.panamafreefall.com

[eames 0]

Quote

It cuts the reserve closing loop, which releases the pin, which allows the pilot chute to deploy. That's it! Beautiful in its simplicity.

Right, except it doesn't release the pin, it just cuts the closing loop, which allows the container to open. The pin has nothing to do with it. With a Cypres anyway. I guess it's all just how you want to look at it.

Michele: No, a partial reserve handle pull isn't going to stop anything from opening.

Jason

[PhreeZone 15]

The 12000 is a ripcord puller. It attaches to the pin and actually pulls it. It could really care less about if you've already pulled or not... it will still pull. Cool thing on the 12000 is you can chamber test it after any fire and have it back in service for free in about 20-30 minutes.

Yesterday is history
And tomorrow is a mystery

Parachutemanuals.com

[Remster 24]

Quote

It attaches to the pin

I know we're in knit-picking territory now, but it doesnt attach to the pin. It is linked to the reserve cable by a metal ring. The FXC will pull the cable in a very simmilar way as a RSL will (but obviously for different reasons).

Remster

[bobsoutar 0]

[could a partial pull on the reserve handle create something which would not trigger the AAD to fire...? ]

Simple answer Michele - No! Not with a Cypres anyway.

[diverdriver 5]

And if you're going through airport security don't EVER describe a Cypres loop cutter in this manner:

Quote

The cylinder is a lil bit longer than the size of a 9mm bullet and thin like a 22mm bullet,

Just call it a "loop cutter". Don't call it a .22 caliber anything. Don't call it a cartridge.

Remember: "Loop cutter".

The Sentinel AAD can also have what is known as a "Pin Pusher". It has a device that when activated expands. Part of the metal "pushes" on the loop while the other part pushes the pin out. Think of it as the "jaws of life" type motion. Stick it between the two parts you want to seperate.

The beautiful thing about Cypres is that it cuts the loop. It is independant of the pin in case the pin were to be bent and hard to pull.

Chris Schindler

[PhreeZone 15]

Sentinels use replaceable cartridges that are what the airlines have a ban on. They quit selling them to the sport market in the early 90's but still offer them to the military and other markets. The Design was first used in 1959 and remained popular until the early 80's. Thats a long time for anything in skydiving to stick around. The Sentinel was around for world records going from 30 to over 100, from the days of Twin Beeches being special to the introduction of turbine planes to skydiving. In PPM vol 2 they claim a confirmed 1000+ saves due to this device and an estimated 5000 actual times it was used.

Yesterday is history
And tomorrow is a mystery

Parachutemanuals.com

[Zennie 0]

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Remember: "Loop cutter".

And that's only if they get too inquisitive. Otherwise, I'd tell them it's a "reserve deployment device".

- Z
"Always be yourself... unless you suck." - Joss Whedon

[Spy38W 0]

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Just call it a "loop cutter". Don't call it a .22 caliber anything. Don't call it a cartridge.

Remember: "Loop cutter".

Just my two cents, but I prefer to say it releases the reserve parachute, make it sound like it's a pin or something. I just cringe at the word "CUT" anymore.

--
Hook high, flare on time

[nacmacfeegle 0]

"reserve deployment device".

Sounds way better than say "barometric detonator and explosive bolt".....

--------------------

He who receives an idea from me, receives instruction himself without lessening mine; as he who lights his taper at mine, receives light without darkening me. Thomas Jefferson

[riggerrob 561]

To summarize:

FXC 12000 uses a bloody big spring to pull the reserve ripcord pin.

Sentinel uses a "thingy that goes POP" (never use words like explosive or gun powder near airport security personnel) to pull the ripcord pin. Along the way, Sentinel built 2 or 3 different types of pin pullers, but they all work basically the same way.

Cypres and Astra use a "thingy that goes POP" to cut the loop that holds the reserve container closed. Loop-cutter type AADs have nothing to do with ripcord pins. Heck! You could glue or even weld the ripcord pin in place and a Cypres would still save your sorry buttocks!

A wimpy, limp-wristed, half-assed pull on a ripcord handle will not interfer with any of these AADS saving your silly buttocks.

Most AADs are compatible with most RSLs, though I am suspicious about Sentinel mini-pin-pullers and RSLs.

[BodyFlier 0]

As you can see Michele there are a lot of different ways to explain AADs the prefered for me is cypress and does cut the loop and lets the reserve pilot chute out of the container. Thank You riggers!!!

[drenaline 0]

If am not mistaken (probably am) swoopers like the FXC AAD cause it can be turned off once they are under canopy.

HISPA 21
www.panamafreefall.com

[PhreeZone 15]

They would like the Astra... the FXC 12000 has'nt been popular since the 80's.

Most still stick with the tried and true Cypres if they use one at all.

Yesterday is history
And tomorrow is a mystery

Parachutemanuals.com

[ChileRelleno 0]

Quote

And if you're going through airport security don't EVER describe a Cypres loop cutter in this manner:
--------------------------------------------------------------------------- Quote
---------------------------------------------------------------------------
The cylinder is a lil bit longer than the size of a 9mm bullet and thin like a 22mm bullet,
---------------------------------------------------------------------------
Just call it a "loop cutter". Don't call it a .22 caliber anything. Don't call it a cartridge.

Remember: "Loop cutter".

Hmm loop cutter... Box cutter hmm.... Loop cutter, box cutter... Airport security being what they are... Hmmm

ChileRelleno-Rodriguez Bro#414
Hellfish#511,MuffBro#3532,AnvilBro#9, D24868

[riggerrob 561]

AADs are just fancy altimeters and that is how I describe them to security personnel.
Keep life simple for the simple people.

[tombuch 0]

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If am not mistaken (probably am) swoopers like the FXC AAD cause it can be turned off once they are under canopy.

The real advantages of the FXC as explained by many users are less maintenance, no batteries, handle rough treatment better.
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>

This is from my new book called "Jump! Make Your First Skydive Fun and Easy" to be published by McGraw-Hill in February:

FXC 12000
Mechanical AADs have been in use since the late 1960’s. A mechanical design uses a pressure sensor coupled with a powerful spring to extract the pin that holds your container closed. These devices are not dependent on batteries or electronic components, and frequently handle rough treatment better than electronic AADs. The disadvantage of a mechanical AAD is that the sensor can sometimes be fooled into deploying your reserve at too high of an altitude if the air pressure around the device is changing extremely rapidly, or if the unit has not been properly maintained. The only brand of mechanical AAD distributed to the civilian market in the United States is made by FXC Corporation, and is called the FXC 12000. This device is designed to open the parachute at an altitude between 1,000 and 4,000 feet. The specific opening altitude will be selected by your instructor on the ground before each jump. A few schools have selected this AAD for their student gear. Some schools like the FXC 12000 because it is less expensive than an electronic AAD, has been on the market for so long, requires no batteries, and is easy to operate.

Maintenance
It is critical that the AAD you are using has been properly maintained. A poorly maintained AAD might not work when needed, or might deploy your reserve when it shouldn’t. The Cypres AAD requires new batteries every two years or after 500 jumps, and must be inspected by the manufacturer every four years. The Astra has no manufacturer required maintenance or battery replacement cycle, but a chamber test is recommended each time the reserve parachute is repacked. The FXC 12000 requires a manufacturer inspection every two years, and a chamber test each time the reserve is repacked. Since the FXC 12000 is a mechanical device it does not have a computer controlled self test function, so the scheduled chamber and manufacturer tests are the only way to be sure it is functioning properly.


-tom buchanan

Tom Buchanan
Instructor Emeritus
Comm Pilot MSEL,G
Author: JUMP! Skydiving Made Fun and Easy