Bailing out low?

[hackish 8]

With no main open the RSL will not and must not interfere with your ability to deploy the main. If it did then that would be a major design flaw. Forget the RSL get nylon over your head!

-Michael

[hackish 8]

Oh yes, forgot something relevant to the AAD discussion. 2 weeks ago we had a jumper who chopped out from linetwists at 1000'. Reserve opened normally. When I repacked his rig I noted that the AAD had not fired. I would need to check my logbook but I think it was a cypres.

-Michael

[KathleenL 0]

I"m with you lauralicious. If I had to bail I would have bailed on my reserve because that is what I would have been comfortable doing at that altitude.

However, I would most likely have landed with the plane. But only because it was my home DZ and the pilot is a long time family friend and I have complete faith that he would not have given the option to land with the plane if he thought it was a really bad situation. That being said another DZ and pilot I don't know that well I would have been out of there fast.

I think everyone should have an idea of what they would do at various altitudes if they had to bail out. AND you should have that in mind before you get in the plane.

I have said this before and I will say it again. Altitude awareness begins as soon as you take off. I know that I frequently check my altimeter during flight and keep in mind what I would do if I had to bail out. At 6000' (anyone that jumps with me knows that at 6000' I have to apply sparkle lip gloss) I then know that no matter what I can bail on my main.

This is so weird because I jumped a four way with a student the week before and had this exact discussion on the plane ride up. When we were about 1500' I asked him what he would do if the pilot told us to get out right now. He gave me the deer in the headlight look so I explained my philosophy on altitude awareness going up and coming down. JMO

[mirage62 0]

I don't think this has been mention.

During the debrief we had a video of one jumper spun up under a stelito. She had time to exit, open and kick out of line twist above , I believe, 1,500 feet-of course the pucker factor was in place and she was very ready to move to plan B.

I was quite pleased at how well this was handled by everyone, and IMO NOBODY made a wrong decision.

This has been one of the better threads in a long time.

Kevin Keenan is my hero, a double FUP, he does so much with so little

[mdrejhon 8]

Quote

No, it arms once you ascend above 1500 feet. It is always ready to fire the cutter after that point.

It may be semantics but as a computer programmer, it's not quite that simple.

Like any embedded computer (electronic altimeters, digital wristwatch, pocket calculator, even musical greeting cards too! etc), the Cypres has silicon that also comes with some firmware (ultra-tiny software), which is essentially a computer program, usually written in machine language (assembly language).

It may be algorithmic, roughly corresponding to this pseudocode:

while (powered_up)
{
. . . if ( we have ascended above flying altitude) AND
. . . . . . ( we are now descending rapidly ) AND
. . . . . . ( we are beyond 78 mph vertical speed ) AND
. . . . . . ( the acceleration looks correct, doesn't look like a depressurization or anything else ) AND
. . . . . . ( other parameters, etc )
. . . . . . {
. . . . . . . . . fire_cutter_immediately()
. . . . . . }
. . . }
}

Obviously over-simplified, and this is high level compiled language rather than assembly/machine language. The program could be several hundred or thousands of lines instead of 10 lines above, to take into account of all nuances, including intelligent burble-fluctuation-compensation to things like ground level auto-calibrate algorithms.

SSK/Cypres has confirmed it is silicon driven, and SSK claims "The Cypres processing unit, or brain, has the calculating power of a personal computer and is programmed to take account of all eventualities" (bingo!)

The terminology of "armed" may actually be correct and incorrect here; "arming" may mean a variable flag that is set to true (exceeded_78mph == true), this may actually be the 'arming flag', which doesn't execute the cutter unless (78mph_for_at_least_250milliseconds == true) AND (doesnt_look_weird == true) and not a transient spike caused by rapid aircraft pressurization, like the C130 incident at the 400-way world record. The cutter only fires when all defined conditions are true -- and the conditions in the Cypres are actually more complex and intelligent than most people think -- just witness the computer bugs discovered in Vigil's on the C130 flight.

Depending on interpretation, as a computer programmer, all of you may actually all be correct (both 980 and billyvon), it depends on how the computer program on the Cypres is interpreted in Plain English Language. It is extremely hard to convert engineerspeak into Plain English speak sometimes, and sometimes you have to invent similiar terminology such as "arming" or "raised level of alert" or "scared mode"

When people say Cypres "was scared", it's probably a case where all conditions in my above became true except for one or two. It could even be a scoring logic, or a fuzzy logic formula, or voting logic, or some other more complex formula than the if statement. Due to proprietary trade secrets, we will never know unless someone cracks the Cypres code and analyzes it.

Because there are multiple conditions to calculate, and there are invariably multiple conditions or modes in a computer program (which could be English-labelled by Marketing or Support department as a "scared mode" or "heightened alert").

It is a closely guarded SSK secret, what kind of algorithms run in the Cypres. Who knows, it is possible that a magic number of "1150" might actually exist somewhere in the computer program, maybe to compensate for a lag (by the time the sensor measures 1150, it's actually 1000 real-world feet, due to the burble above) or as a "begin paying close attention" trigger (i.e. execute algorithms differently beginning at 1150 feet) or for another reason, and simply called an "arming". And then somehow someone at SSK at one time or another, mentioned this value, and it got misinterpreted. This much can be said, SSK is probably not happy about the competition and they want to keep rein in on any hints of how their Cypres operates. It's possible the word "arming" is now depreciated (and it's just a "internal mode state change" now), and that the "arming" terminology is now re-interpreted as (ascended_high_enough == true) instead of (zooming_past_1150feet == true) even though both flags still exist. It's very easy to re-write the English interpretation of a computer program, without modifying the computer program at all (especially in this case because there's multiple flags that represent a "heightened state" of being closer to cutting the loop, any one of these states could be called an 'arming' stage, since 'arming' here is just a human psychological term because everything is being done electronically instead of mechnically the Cypres with the sole exception of the pushbutton and the cutter)

Therefore, both billyvon and 980 is perhaps correct, despite the apparent disagreement.

[Heatmiser 0]

Holy crap dude! You don't ever say anything short and sweet, do ya?

What you say is reflective of your knowledge...HOW ya say it is reflective of your experience. Airtwardo

Someone's going to be spanked! Hopefully, it will be me. Skymama

[Sletzer 3]

I wish someone had videoed it from the ground. That would have been cool to watch.

I will be kissing hands and shaking babies all afternoon. Thanks for all your support! *bows*

SCS #8251

[Andy9o8 0]

Nice write-up, especially for those of us who are algorithmically challenged. Thanks.

[pchapman 261]

Further to mdrejhon's post, some trivia for the day:

The Cypres 1 and 2 manuals do not contain the word "arm" anywhere.

They do say that the Cypres "will not work" if one exits below 1500'.

[Rstanley0312 0]

Quote

Further to mdrejhon's post, some trivia for the day:

The Cypres 1 and 2 manuals do not contain the word "arm" anywhere.

They do say that the Cypres "will not work" if one exits below 1500'.

Still supporting what Bill and I have said ...... arm, activate, etc. the point is it gets to that point above "x" altitude and does nothing more unless a certain pressure is met that activates the cutter.

Life is all about ass....either you're kicking it, kissing it, working it off, or trying to get a piece of it.
Muff Brother #4382 Dudeist Skydiver #000
www.fundraiseadventure.com

[billvon 2,400]

>"arming" may mean a variable flag that is set to true . . .

Agreed. There are several parameters that must be met for the cypres to fire, and you could easily claim that once one or two of the parameters are met it is "armed."

However, many people interpret that statement the wrong way, and think:

1) Once it arms, it MUST fire
2) It needs a few seconds to arm
or
3) it arms in freefall, not when ascending past 1500 feet.

All those conclusions are incorrect, and hence I don't use them in that way. To me, the term "arm" means "the device is now enabled and will fire when its parameters are met" - and that happens at 1500 feet during the ascent. (It disarms at 130 feet.)

[tbrown 26]

Quote

Quote

(I've heard they arm at 1200', fire around 750??? - not sure if this is true).

Read the owner's manual. It's important to know how your specific AAD operates.

The thing about AADs is that they can pop as high as 1200 ft, if you're at line stretch and your main is sniveling and shaking itself out. It has to do with air pressure in the upright position at 1200 ft being very close to the low pressure area over someone's back in freefall at 750 ft. It's why people who accidently pull low end up with so many reserves out at or just above a grand.

Obviously, taking your rig off to disable your AAD, then putting the rig back on is not a good or practical idea in a bailout situation. So the question would be more like "Can my main open by about 1200 ft above the level of the dropzone ?" (as there may be hills across the street). Then, if the terrain is sketchy, you might also want to consider that a ZP canopy, especially a 9 cell, probably has more glide than your 7 cell F-111 reserve. Plus, you've still got the option of using your reserve if your main decides it's "not in the mood".

Finally, and it happens over and over again - and is another main cause of having both canopies out - no matter what people think or say, they will often reflexively reach back for Mr. Hackeysack, no matter how low they are. You can train to go for silver all you want, but silver is a handle you have to DECIDE to use. The main is something you do so many times, it's just automatic, whether or not it's the best idea. Anyway, above 1500 ft I'd probably go with my Pilot main. Below, I'd be deciding in the door to go reserve and bail out looking for my ripcord handle.

Glad to hear everyone was okay on this bailout.

Your humble servant.....Professor Gravity !

[warpedskydiver 0]

I am a very low timer but upon completion of my A and given no problems with my training, I would GTFO on my main (Sabre 2)

They are not asking you get out for some silly reason, there is a serious chance of something else happening in a sequence of events when an engine goes out or other problems arise.

Scenario;

You stay in the plane and something else happens, now you are even lower, say around 1200' AGL.

I don't know as much as any of you, not even close, but I know your first rule is to save your life.

A long time ago I hit from 35 feet and I do not want to endure that again.

*Not a skydiving incident

[thrillstalker 0]

Quote

I am a very low timer but upon completion of my A and given no problems with my training, I would GTFO on my main (Sabre 2)

They are not asking you get out for some silly reason, there is a serious chance of something else happening in a sequence of events when an engine goes out or other problems arise.

Scenario;

You stay in the plane and something else happens, now you are even lower, say around 1200' AGL.

I don't know as much as any of you, not even close, but I know your first rule is to save your life.

A long time ago I hit from 35 feet and I do not want to endure that again.

*Not a skydiving incident

you also have to take into consideration the other jumpers. are you experienced enough to jump and avoid any collisions from opening in close proximity to so many other jumpers. at a low jump number it is just as dangerous if not more to bail with the rest. if it is a mandatory bail it might be a little different, but in the situation that prompted this thread it was not mandatory but a "you can if you want to."

"Never grow a wishbone, where your backbone ought to be."

[warpedskydiver 0]

Agreed

If the pilot was to say GTFO all other arguments go out the door

[thrillstalker 0]

went ahead and did a hop n pop yesterday so i would have at least one in case shit hits the fan.

"Never grow a wishbone, where your backbone ought to be."

[rhaig 0]

I started this thread on rec.skydiving about 10 years ago. But that thread was citing 1000'

at 1800, main every time (sabre 170 loaded at 1.2:1).

Why? Because I know it would open fine for me and I'd be saddled in by 1200'. And if it was going wrong, I'd know immediately as many times as I've jumped that canopy.

--
Rob

[BenediktDE 2]

My EPs for aircraft emergencies:
sub 1000: check seat belt, check helmet, promise drink to pilot after landing
1000 - 1500: check seat belt is off, check legwing (wingsuit) is closed, check arm wings are still open, exit with hand on reserve handle and land the reserve
1500 - 2000: check legwing is closed, close arm wings if time allows, exit with hand on PC and wings closed, pull main
over 2000: Standard flying exit, short 45° turn and pull main after 2 seconds flight

add a few hundred feet for exits above water or woods. Do the same for unstable plane.

For every complex problem there is an answer that is clear, simple, and wrong.

[erdnarob 1]

You are forgetting the differential pressure between the chest and the back. If you pull your main at 1300 ft for instance since you will be straight up during the main deployment with no differential pressure (equivalent to 260 ft) your AAD will fire at 700 + 260 which is 960 feet. If your parachute takes more than 340 ft to open, your AAD will fire and you will have hopefully a nice biplane or something less interesting. Now what kind of AAD do you have which fires at 700 ft? Cypres Expert fires at 750 ft, Argus expert fires at 800 ft and Vigil PRO fires at 840 ft. The Astra fires at a 1000 ft. But as I said all of them (but the Astra which has the pressure sensor in the front) will fire 260 ft higher when in a stand up position which happens during the main deployment.
Therefore, if you don't want to take the chance of a double deployment which is always so so, I recommend not using the main under 2000 ft. If people are reluctant to use their reseve, well they should maybe stop jumping. A reserve is TSOed, packed by a qualified rigger according the manufacturer's specifications. If you trust your rigger then your reserve is your best insurance.This is why I am a rigger.

Learn from others mistakes, you will never live long enough to make them all.

[mdrejhon 8]

Quote

You are forgetting the differential pressure between the chest and the back. If you pull your main at 1300 ft for instance since you will be straight up during the main deployment with no differential pressure (equivalent to 260 ft) your AAD will fire at 700 + 260 which is 960 feet. If your parachute takes more than 340 ft to open, your AAD will fire and you will have hopefully a nice biplane or something less interesting. Now what kind of AAD do you have which fires at 700 ft? Cypres Expert fires at 750 ft, Argus expert fires at 800 ft and Vigil PRO fires at 840 ft. The Astra fires at a 1000 ft. But as I said all of them (but the Astra which has the pressure sensor in the front) will fire 260 ft higher when in a stand up position which happens during the main deployment.
Therefore, if you don't want to take the chance of a double deployment which is always so so, I recommend not using the main under 2000 ft. If people are reluctant to use their reseve, well they should maybe stop jumping. A reserve is TSOed, packed by a qualified rigger according the manufacturer's specifications. If you trust your rigger then your reserve is your best insurance.This is why I am a rigger.

Aren't we talking about exiting a plane?

It's safer to pull main at 1500feet from level flight THAN 2000feet at terminal, for most mains. Different ballgame.

Also, though not recommended, the AAD won't activate even at a 1000ft exit, or 1200ft, or 800ft (even after ascending above AAD activation altitude then descending) because successful pulls after exiting level flight don't accelerate you fast enough to pop your reserve. By the time you discover anything wrong, for most mals, the cutaway handle is being pulled before you're falling fast enough for the AAD. The delay for AAD activation after a very low level-plane exit is rather long.

[billvon 2,400]

> If your parachute takes more than 340 ft to open, your AAD will fire

That is pretty unlikely.

1) AAD's like the Cypres don't even arm until 1500 feet.

2) You have to accelerate to freefall speeds before an AAD will fire, and that takes 6-7 seconds. Some people found this out the hard way a few years ago when they cut away from a malfunction at around 1000 feet and their reserve did not open in time to save their lives.

3) The whole "glitch when transitioning to a stand" is caused by the vacuum above you at freefall speeds. No freefall speed = no burble (or at least less of one) = less "transition" effect.

Thus, if you use a cypres, and you exited and pulled at 1300 feet, your AAD would not fire. If you exited at 1500 feet and pulled at 1300 feet, it would not fire unless you snivelled at freefall speeds down to about 500 feet. (At which point it probably SHOULD fire!)

[980 0]

Quote

2) You have to accelerate to freefall speeds before an AAD will fire,

wrong.

Cypres activation speed is 35m/sec = 78mph. That is approx 70% of terminal, which is what most people refer to as freefall speed.

Quote

it would not fire unless you snivelled at freefall speeds down to about 500 feet

same as above, not freefall speed, but 78 mph.

[billvon 2,400]

>Cypres activation speed is 35m/sec = 78mph. That is approx 70%
>of terminal, which is what most people refer to as freefall speed.

OK, change that to "you have to accelerate to close to freefall speeds." Sadly, 800 feet is not sufficient time to accelerate to those speeds, as the jumpers at Rantoul discovered a few years back.

[TrojanHorse 0]

Bill is right

With army low level exits in mind we once calculated the following:

Exit 1000 feet MSL
Cutter activation 700 feet MSL (It takes about 300 feet to reach 78 Mph)
Pilot chute and bag launch at 625 feet MSL (0,5 second after activation)
Canopy open 360 feet MSL

Be aware this is calculated at MSL, meaning that a bit of field elevation (flying over a small hill) makes the margin even narrower.

Don’t wait for your AAD! You are loosing valuable time and altitude.

Warm regards,
William

PS I am a firm believer in Murphy; you will see that you bail out right above that hill...