0
airdvr

Questioning Stats in Parachutist Article

Recommended Posts

January Issue, Article on RSL's

There are some stats that I question in this article;

Average jumper takes 6 to 8 seconds from the time they decide to initiate cutaway and the time they actually release the main.

6 to 8 seconds to regain a stable belly to earth body position after release of the main.

Huh? That's 12 to 16 seconds to go from recognizing a mal to pulling your reserve ripcord. Maybe another couple for reserve inflation. Something doesn't add up.
Please don't dent the planet.

Destinations by Roxanne

Share this post


Link to post
Share on other sites
I fully believe the time to get stable time. There are a lot of people that only want to pull their reserve when they are flat and stable and not spinning again and that all takes time to enter into freefall, build up enough speed to gain control and then orient yourself to your belly and stop a spin. Look at how long it takes people jumping from a balloon to get perfectly stable after an unstable exit and that usually involves a ton of arm windmilling when they knew what was about to happen.
Yesterday is history
And tomorrow is a mystery

Parachutemanuals.com

Share this post


Link to post
Share on other sites
airdvr

January Issue, Article on RSL's

There are some stats that I question in this article;

Average jumper takes 6 to 8 seconds from the time they decide to initiate cutaway and the time they actually release the main.

6 to 8 seconds to regain a stable belly to earth body position after release of the main.

Huh? That's 12 to 16 seconds to go from recognizing a mal to pulling your reserve ripcord. Maybe another couple for reserve inflation. Something doesn't add up.



I questioned that as well. I have several of my chops on video (no RSL) and averaged about 1 second to roll over and punch my reserve after whacking spinning mals.

As for the time between the decision to chop and actually doing it, I'm not sure how they arrived at any particular number beyond what jumpers might have told the author.

Other than a noob, if a jumper without an RSL takes 6 to 8 seconds to regain stability after cutting away he/she should rethink their hobby of choice.
Chuck Akers
D-10855
Houston, TX

Share this post


Link to post
Share on other sites
But you, like the children of Lake woebegone, ARE above average.
This is the paradox of skydiving. We do something very dangerous, expose ourselves to a totally unnecesary risk, and then spend our time trying to make it safer.

Share this post


Link to post
Share on other sites
PhreeZone

There are a lot of people that only want to pull their reserve when they are flat and stable and not spinning again and that all takes time to enter into freefall, build up enough speed to gain control and then orient yourself to your belly and stop a spin.
Look at how long it takes people jumping from a balloon to get perfectly stable after an unstable exit and that usually involves a ton of arm windmilling when they knew what was about to happen.


All of skydivers started their jumps with horizontal speed (I think).
If we didn't have airplanes, those abilities (staedy poise quick) would arouse sooner... and wouldn't have special base name to it.
What goes around, comes later.

Share this post


Link to post
Share on other sites

What the heck, although I've been on DZ.com way too much the last couple days, I'll offer my limited experience with chops:

Without going into the messy analysis of different scenarios and of different imprecise data (video and Protrack for example), I've come to a few preliminary conclusions, at least for myself, for typical situations:

This is based on 3 actual mals (on an 88 or 75 sq. ft canopy for someone 145-155lbs without gear) and 2 intentional cutaways (on a 37 or 200) going to an F-111 main not unlike a reserve.

-- From chop to having a fully open, flying reserve is going to be about 700' -- for a diving spinning mal from which one flips to belly to earth and then pulls the reserve.
(No RSL ;)) Maybe it'll be 600' to initial full inflation, but being conservative or allowing for the canopy to really be flying pretty steady a little after snapping open, it'll be 700'

-- The time from chop to reserve pull in that sort of situation will be 3-4 seconds.
Mentally that sort of works out: In the first second, one falls away. To flip to belly to wind might take 2 seconds, where the first second of the chop might be a productive part of getting flipped over, or just a second wasted as one just tumbles away while getting a feel for the wind and going to a better body position. Then one more second to reach in and pull. So there's the total of 3 or 4 seconds. One isn't trying to get perfectly stable, exactly level with zero yaw rate, but just to be generally belly to the wind.

Of course if one wants to save altitude, the chop and pull can follow each other within a second, just enough to make sure one doesn't have a hard pull on the cutaway.

-- My Protrack records suggest the vertical speed during a spinning mal with a fairly small canopy might be something around 50 or 60 mph (when not waiting around forever with it), so about 80 or 90 fps. To be conservative, not wanting to underestimate altitude loss, lets call it 100 ft lost per second during a fairly high performance spinning mal.

The altitudes and times work out: [Edited to correct a mistake in what I was trying to say] Starting with a somewhat under 100 fps descent rate before starting freefall again, then increasing speed while taking 3-4 seconds from chop to reserve pull, one could blow through 400'. Then add on 300' or so for reserve deployment, so it all matches up with the previously mentioned 700' total.

-- The only time I had a messy fall away from a mal that maybe took a little more time, was from a slower speed mal, where I was still in a sitting position when I chopped (= massive dearch). When I dropped and twisted to face the ground I still had some momentum and poor aerodynamic control, so ended up going around once more (total 1 1/2 rotations) to get belly to earth for the pull. For the lower speed mal, the total distance from chop to open canopy was still no more than 700', as for higher speed spinning mals. The lower speed compensated for the worse body control at lower speed.

(On the other hand, I've had a chop during a low speed mal, going straight to reserve with a good body position, where probably only 300-350' were lost. As with the numbers earlier, knock off up to 100' if one wants 'first full inflation'. It is hard to get exact timings and numbers, but in any case it looked fast enough that someone on the ground later asked if I had a Skyhook.)

-- As for for how long it takes to decide to cutaway, I don't know, but I'd guess it could easily take 3-4 seconds when one adds up realistic times to perceive the opening, decide it really isn't fixable, go in for one's handles, and then in a coordinated manner, start pulling stuff. If you are are more primed to chop because you are low, who knows, I'd guess 2.5 to 3 sec. To actually go through the whole cycle of observing, deciding, and reacting, I wouldn't claim anything lower than that for most situations.

Share this post


Link to post
Share on other sites
" ... and then orient yourself to your belly and stop a spin. ...

..............................................................................

Many people's inner-ears get so badly "spun up" that they need 30 or more seconds before their eyeball orientation matches their inner-ear's orientation.

Share this post


Link to post
Share on other sites

I hear what you're saying Rob but the numbers don't make sense. We were supposed to be "in the saddle" at 2 grand. Most people I knew were dumping at 2 grand, myself included. If you use those numbers every malfunction would have resulted in a fatality. [:/]

Please don't dent the planet.

Destinations by Roxanne

Share this post


Link to post
Share on other sites
airdvr

I hear what you're saying Rob but the numbers don't make sense. We were supposed to be "in the saddle" at 2 grand. Most people I knew were dumping at 2 grand, myself included. If you use those numbers every malfunction would have resulted in a fatality. [:/]



Perhaps the convention back when dinosaurs roamed the earth was to chop and pull pretty much simultaneously. Maybe with higher deployment altitudes, people have gotten used to the thought of delaying the reserve pull for whatever reason, even if it is not to regain stability.

Maybe using both hands on each handle is more common now than decades ago, resulting in a delay. Recalling when I've had to chop, there was really no delay between the first and second punch out of the fists, and I can't imagine being in the mindset of delaying intentionally. If I really knew I was very high a delay might be natural.
People are sick and tired of being told that ordinary and decent people are fed up in this country with being sick and tired. I’m certainly not, and I’m sick and tired of being told that I am

Share this post


Link to post
Share on other sites
lyosha

... are you questioning stats in that article or their opinion of cutaway times?

Because I think the title of this thread is very misleading...



It's not presented as opinion in the article.
Please don't dent the planet.

Destinations by Roxanne

Share this post


Link to post
Share on other sites
I agree - I have 3 chops and the hesitation from chopping to pulling my reserve was maybe 1.5 seconds (probably closer to 1). One for spinning line twists, one for a broken steering line and one spinning on my back with multiple broken lines....

As for me and my house, we will serve the LORD...

Share this post


Link to post
Share on other sites
airdvr

I hear what you're saying Rob but the numbers don't make sense. We were supposed to be "in the saddle" at 2 grand. Most people I knew were dumping at 2 grand, myself included. If you use those numbers every malfunction would have resulted in a fatality. [:/]



....................................................................................

There is a lot of overlap with these statistics.
As for "being in the saddle at 2,000 ..."
Hee!
Hee!
There are multiple regional interpretations of that number.
Back in the good-old-days (1980s), you merely had to "show a pilot chute" above 2,000 to keep the Safety Officer/DZO off your back.
Also remember that old-style parachutes descended much slower, even when they malfunctioned.
We have also seen a dramatic reduction in fatalities since the introduction of electronic AADs ... 20 years ago ... because electronics are a better judge of altitude than the human eyeball.
Nowadays, I kick myself if I am not "sitting in the saddle" by 2500 feet.

Share this post


Link to post
Share on other sites
chuckakers

***January Issue, Article on RSL's

There are some stats that I question in this article;

Average jumper takes 6 to 8 seconds from the time they decide to initiate cutaway and the time they actually release the main.

6 to 8 seconds to regain a stable belly to earth body position after release of the main.

Huh? That's 12 to 16 seconds to go from recognizing a mal to pulling your reserve ripcord. Maybe another couple for reserve inflation. Something doesn't add up.



I questioned that as well. I have several of my chops on video (no RSL) and averaged about 1 second to roll over and punch my reserve after whacking spinning mals.

As for the time between the decision to chop and actually doing it, I'm not sure how they arrived at any particular number beyond what jumpers might have told the author.

Other than a noob, if a jumper without an RSL takes 6 to 8 seconds to regain stability after cutting away he/she should rethink their hobby of choice.

I have three high speed mals, none took over 3 seconds to assess - chop - pull reserve, the last one I had was on my FX and I was filming a freefly dive and we were able to study the mal and see just how stable I was and to actually time my reactions.

my slow speed mals - also three - I probably took about as long to assess the situation as the author has in his article since I did have time and altitude to do so
- however only on one did I not follow the cutaway with an immediate reserve pull.

I cant imagine taking 12 seconds from recognizing a high speed mal - chop - activating my reserve, that's crazy slow - at that rate I would be in the ground.

Roy
They say I suffer from insanity.... But I actually enjoy it.

Share this post


Link to post
Share on other sites
Reaction time varies widely, depending upon how recently you have reviewed emergency procedures.

As a rigger, I encourage skydivers to pull all their own handles whenever their reserves are due for inspection. I also use this as a opportunity to review emergency procedures.
You would be amazed at how many forget to toss their main pilot-chute!
You would be amazed at how many forget to look at their cutaway handle!
You would be amazed at how many forget to look at their reserve ripcord!

We usually "talk through" one type of malfunction in slow-time, then the second time, we rehearse in real-time. I tell them to pull all their handles during the second rehearsal.

You would be amazed at how many skydivers hesitate for 20 or 30 seconds when I start yelling about "holes big enough to drive a bus through, broken lines, you are on your back and spinning, you cannot untwist the risers, you cannot untwist the risers, you cannot untwist the risers, etc."
The fiend in me also has a habit of grabbing their leg strap and spinning them around.
Har!
Har!
Har!

Share this post


Link to post
Share on other sites
heh, that's awesome!

I did similar when I was running first jump courses, standing behind the first student I would have him visualize the exit as it wasn't quite doable to do the real motions in the hanging harness and after giving the go command while he was arching and counting I would choke the pilot chute behind the hackey and make it an impossible pull - many students made too many attempts and a few even managed to extract it even with me trying to hold it.

but the best was the 2nd student up into the harness, without fail they would have a smirk or smile on their face as they just knew what was coming...

same as before on the visualizing etc... but instead I stuffed the hackey and pretended to hold it... many of them also made too many attempts to find a missing handle - one exceptionally dexterous individual actually managed to dig it out in about 4 seconds and toss...

3rd student was never as cocky as the 2nd as they realized by now that they did not have a preview of what was to come and I usually gave them a clean shot at the handle but would toss in broken lines, lineover, blown up canopy or canopy freaking out when the brakes were pulled or whatever struck my fancy at that moment.

I have had students get pissed because "I was messing with them" <--- in their words but they usually calmed down when informed quite seriously that locking onto going for an impossible pull, missing handles, or broken lines, canopy collapsing for no apparent reason has resulted in someones death and is something that can happen.

one of my last students I trained *(ratings now lapsed, no interest in regaining them) had a spinning mal, his body postion and opening were good but the canopy immediately started spinning clockwise - not a real aggressive spin but it had me anticipating a lineover or tension knot, as we flew around him I watched him pull the brakes all the way down twice just like he was trained but when he let them up it began spinning again, he corrected the spin with one toggle then I watched his head go down as he dropped that toggle and grabbed his cutaway - the only thing he didn't do as trained was to arch hard prior to releasing the main.

I was extremely excited to watch a first jump student I had trained do almost everything textbook perfect in an actual malfunction on his very first jump.

time from assessing the mal, try to fix, go to his cutaway/ reserve activation (RSL beat him to the handle) was about 15 - 20 seconds so that puts his reaction time around the range of the article

Roy
They say I suffer from insanity.... But I actually enjoy it.

Share this post


Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

0