Forums: Skydiving: Safety and Training:
Why I don't hook up my RSL

 

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Southern_Man  (C License)

May 21, 2013, 7:46 AM
Post #51 of 63 (1304 views)
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Re: [Sky_doggy] Why I don't hook up my RSL [In reply to] Can't Post

Sky_doggy wrote:
billvon wrote:


Your AAD will NOT FIRE in most cases like this even if you cut away fairly high (1500 feet or so.) Several fatalities have occurred when people cut away and did not pull their reserves. They had AAD's but no RSL's - and the AAD's did not fire in time.

Thanks for posting this. I assume that a AAD will not fire under this scenario because the skydiver has not re accelerated, however rather than me assume could you point me towards a source of information that would help be get more educated on this.

Thanks.

You have it right, the AAD will not fire until you reach the fire speed. Then it may not fire if you are under the shut--off height. You should read the manual for your AAD brand because the firing parameters are different. Know your gear, knowledge is power.


Premier billvon  (D 16479)
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May 21, 2013, 1:57 PM
Post #52 of 63 (1250 views)
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Re: [Sky_doggy] Why I don't hook up my RSL [In reply to] Can't Post

> I assume that a AAD will not fire under this scenario because the skydiver has not re accelerated

Several reasons.

1) You have to accelerate to activation speed which can take 4-5 seconds.

2) This has to happen above disarming altitude (~130 feet for a cypres)

3) As you rotate to belly-down (which most people do after a cutaway) the sensor sees a drop in pressure, which it translates into a rise in altitude (or in this case a slower descent)

All this means you can cut away at 1500 feet and still not get an activation before impact (or an activation that is too late to save your life.)


browncow  (D License)

May 22, 2013, 12:27 AM
Post #53 of 63 (1175 views)
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Re: [billvon] Why I don't hook up my RSL [In reply to] Can't Post

Here is a vid i found on youtube of a guy spending 10 secs getting stable after cutting away from a spinning malfunction.

He opens pretty bloody low.

http://www.youtube.com/watch?v=xCZPuc-c_6g


Deimian

May 22, 2013, 1:36 AM
Post #54 of 63 (1161 views)
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Re: [billvon] Why I don't hook up my RSL [In reply to] Can't Post

One, probably stupid, question. Why does a disarming altitude exist? I can't think in any scenario where it is necessary. Without it in the worse case the AAD fires too low to be useful. In the best case there is an offset (I mean ground offset, not offset in the configuration of the AAD) between the real altitude and the altitude the AAD thinks you are, and in that case it fires high enough to be useful, even though it might think you are too low.


airtwardo  (D License)

May 22, 2013, 7:13 AM
Post #55 of 63 (1107 views)
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Re: [Deimian] Why I don't hook up my RSL [In reply to] Can't Post

Deimian wrote:
One, probably stupid, question. Why does a disarming altitude exist? I can't think in any scenario where it is necessary. Without it in the worse case the AAD fires too low to be useful. In the best case there is an offset (I mean ground offset, not offset in the configuration of the AAD) between the real altitude and the altitude the AAD thinks you are, and in that case it fires high enough to be useful, even though it might think you are too low.

How about a radical dive on a tiny canopy?


Deimian

May 22, 2013, 7:51 AM
Post #56 of 63 (1096 views)
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Re: [airtwardo] Why I don't hook up my RSL [In reply to] Can't Post

airtwardo wrote:
How about a radical dive on a tiny canopy?

What about that? Radical dives with speeds exceeding 78 mph (96/102 mph in Cypres Speed) might also happen at an altitude higher than 130ft (330ft). Even if this didn't happen, if I'm not swooping why would I want a disarming altitude?

I understand that the lower you are in your dive, the faster you might be falling. Therefore it is more likely that your speed can exceed the firing speed at the lower point, and a disarming altitude can help to prevent such scenario. But for me I see two problems here: (1) if you initiate your dive higher, just to practice, you can still exceed that speed and "force" an undesired firing; (2) if you are not swooping you won't be in a controlled dive that you can pull out, and therefore you'll be in a fucked up situation that most probably will be slightly better with more nylon.

For (1), you should know your gear and if you are doing such practice you should shutdown your AAD before the jump, like many swoopers do with "non-swooping" AADs. But for (2) I still can't see the point of the disarming altitude.


Zlew  (D 21616)

May 22, 2013, 12:27 PM
Post #57 of 63 (1026 views)
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Re: [chuckakers] Why I don't hook up my RSL [In reply to] Can't Post

It's a sellers market for sure.

My team just went to all one AAD manufacture. The "other" AAD's we replaced all sold very quickly. Didn't matter if they were really new, or heavily used. High demand, low supply.


evan85  (C 41367)

May 22, 2013, 2:27 PM
Post #58 of 63 (976 views)
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Re: [Deimian] Why I don't hook up my RSL [In reply to] Can't Post

Deimian wrote:
airtwardo wrote:
How about a radical dive on a tiny canopy?

What about that? Radical dives with speeds exceeding 78 mph (96/102 mph in Cypres Speed) might also happen at an altitude higher than 130ft (330ft). Even if this didn't happen, if I'm not swooping why would I want a disarming altitude?

I understand that the lower you are in your dive, the faster you might be falling. Therefore it is more likely that your speed can exceed the firing speed at the lower point, and a disarming altitude can help to prevent such scenario. But for me I see two problems here: (1) if you initiate your dive higher, just to practice, you can still exceed that speed and "force" an undesired firing; (2) if you are not swooping you won't be in a controlled dive that you can pull out, and therefore you'll be in a fucked up situation that most probably will be slightly better with more nylon.

For (1), you should know your gear and if you are doing such practice you should shutdown your AAD before the jump, like many swoopers do with "non-swooping" AADs. But for (2) I still can't see the point of the disarming altitude.

Someone more knowledgeable please correct me if I'm wrong.

I believe the answer is that if your reserve fires while under a functional (though diving/swooping) main with significant altitude, you may have a survivable two-out scenario. If your reserve fires at 80 ft under a functional main, however, you are potentially in a lot more trouble.


Deimian

May 23, 2013, 1:31 AM
Post #59 of 63 (889 views)
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Re: [evan85] Why I don't hook up my RSL [In reply to] Can't Post

evan85 wrote:
Someone more knowledgeable please correct me if I'm wrong.

I believe the answer is that if your reserve fires while under a functional (though diving/swooping) main with significant altitude, you may have a survivable two-out scenario. If your reserve fires at 80 ft under a functional main, however, you are potentially in a lot more trouble.

Correct, but if you are not swooping there is no way your AAD will fire if you are under a functional main at that altitude. You simply won't have enough speed to trigger it. If you have enough speed you don't have a functional main. Right?


Premier billvon  (D 16479)
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May 23, 2013, 11:42 AM
Post #60 of 63 (822 views)
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Re: [Deimian] Why I don't hook up my RSL [In reply to] Can't Post

>One, probably stupid, question. Why does a disarming altitude exist?

1) So front riser landings will not cause the device to fire. Nowadays, of course, people can hit such speeds well above 130 feet - thus "swoop" versions of AAD's.

2) It's just not helpful to open your reserve at 100 feet at 80mph. You are less than a second from impact. It's not going to do anything.

3) It helps prevent "sudden pressurization" events from causing AAD firings. These can come from an aircraft or even a well-sealed car door being slammed.


Deimian

May 23, 2013, 1:43 PM
Post #61 of 63 (797 views)
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Re: [billvon] Why I don't hook up my RSL [In reply to] Can't Post

billvon wrote:
>One, probably stupid, question. Why does a disarming altitude exist?

1) So front riser landings will not cause the device to fire. Nowadays, of course, people can hit such speeds well above 130 feet - thus "swoop" versions of AAD's.

2) It's just not helpful to open your reserve at 100 feet at 80mph. You are less than a second from impact. It's not going to do anything.

3) It helps prevent "sudden pressurization" events from causing AAD firings. These can come from an aircraft or even a well-sealed car door being slammed.

1) In "non-swoop" scenarios, can you really be falling at 78mph, at 130ft from the ground, and still land properly? I don't think so. If you are under those circumstances you'll hit the ground quite hard, and an AAD firing won't create a bigger problem.

2) Sure, I absolutely agree, it is not helpful to open it so low. But my whole point is that in some circumstances you might be landing slightly below what the AAD thinks. In those cases, a few more feet can be the difference between pounding hard, with as much nylon above your head as possible, and pounding for the last time. Again, for no swoop scenarios.

3) Ok, that makes sense.


-ftp-

May 23, 2013, 2:21 PM
Post #62 of 63 (786 views)
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Re: [airtwardo] Why I don't hook up my RSL [In reply to] Can't Post

airtwardo wrote:
normiss wrote:
Agreed.

I'll take an increase in odds in my favor any day.

...I adjust my opening altitude & hard-deck accordingly.

well what if that is blown because of some unforseen circumstance? Do you think you would take an RSL at that point? Besides CRW, Camera etc. To not wear an RSL becuase of the super remote chance that it causes more problems is crazy in my humble internet opinion.

Let's ask this question: Do you think it is more likely that you would have an RSL induced mal/problem or find yourself somehow/someway lower than your "adjusted" pull alt.? I think the answer is fairly obvious...


airtwardo  (D License)

May 23, 2013, 8:06 PM
Post #63 of 63 (747 views)
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Re: [-ftp-] Why I don't hook up my RSL [In reply to] Can't Post

-ftp- wrote:
airtwardo wrote:
normiss wrote:
Agreed.

I'll take an increase in odds in my favor any day.

...I adjust my opening altitude & hard-deck accordingly.

well what if that is blown because of some unforseen circumstance? Do you think you would take an RSL at that point? Besides CRW, Camera etc. To not wear an RSL becuase of the super remote chance that it causes more problems is crazy in my humble internet opinion.

Let's ask this question: Do you think it is more likely that you would have an RSL induced mal/problem or find yourself somehow/someway lower than your "adjusted" pull alt.? I think the answer is fairly obvious...



It might be so in your case, in mine...not so much.


I'm jumping out of an airplane with no AAD & no RSL...my altitude awareness is the single most important thing on my mind.

I haven't busted my hard deck in probably 30 years, before that we use to unpack at a grand for shits & giggles...until I got smart that is.

I've been LOW at terminal a bunch, now that I'm older & wiser is definitely not someplace I'll go again.

So...yes it's significantly more likely I'll have a situation where an RSL would cause me problems than it is I'll find myself low & out of time - needing one. YMMV


- Again, MOST of my jumps are with cameras, demo gear or CReW.

Don't need it, don't want it - that's why they're removable...however I understand the additional safety factor it 'can' offer 'most' people, so I would never recommend someone else do as I do.


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