Forums: Skydiving: Safety and Training:
"Clustering" of cutaways

 


Deimian

Sep 9, 2013, 12:54 PM
Post #1 of 14 (3202 views)
Shortcut
"Clustering" of cutaways Can't Post

Just out of curiosity, for the experienced people out there. Did you realize of a "clustering" of cutaways in your DZs? I've been frequently on my home DZ on the weekends this season, and a very few days I've seen cutaways. However, on two different days, I've seen 4 cutaways each. Seeing 4 cutaways on the same day was shocking for me the first time. Seeing 4 on the second day was like WTF? BTW: one of the cutaways on the second day was quite intense, including main entanglement, reserve on the bag for way too long, and finally a reserve opened like 100-50 meters from the ground and a hard landing without flaring with a main still attached by one riser, make sure that you pull completely your cutaway handle before pulling the reserve guys! Bricks were shat.

So, the question is, did you observe a tendency of not having cutaways in weeks, and then all of a sudden having lots of them on the same day? It is just coincidence? I think so. But I would like to hear from other people.

PS: We were joking about those days, saying that we should play "reserve bingo".


-ftp-

Sep 9, 2013, 1:07 PM
Post #2 of 14 (3111 views)
Shortcut
Re: [Deimian] "Clustering" of cutaways [In reply to] Can't Post

what were the reason for the cutaways? As in similar mals? Who was packing them?


Deisel  (D 31661)

Sep 9, 2013, 1:11 PM
Post #3 of 14 (3095 views)
Shortcut
Re: [Deimian] "Clustering" of cutaways [In reply to] Can't Post

Yep. Went all summer with nothing, then bam - bam - bam. Had about 6 in a two week period. All from multiple reasons from severe line twists (mine) to a cell exploding and the canopy coming apart (not mine).

D


Premier Remster  (C License)

Sep 9, 2013, 1:19 PM
Post #4 of 14 (3052 views)
Shortcut
Re: [Deisel] "Clustering" of cutaways [In reply to] Can't Post

Deisel wrote:
Yep. Went all summer with nothing, then bam - bam - bam. Had about 6 in a two week period. All from multiple reasons from severe line twists (mine) to a cell exploding and the canopy coming apart (not mine).

D

Or... You (general you, not directed at anyone in particular) notice the clusters and don't notice the one offs.


pchapman  (D 1014)

Sep 9, 2013, 1:43 PM
Post #5 of 14 (2981 views)
Shortcut
Re: [Deimian] "Clustering" of cutaways [In reply to] Can't Post

Quote:
did you observe a tendency of not having cutaways in weeks, and then all of a sudden having lots of them on the same day? It is just coincidence? I think so.

Random stuff does certainly look non-random, with clusters naturally occurring.

A good example is what is seen in this link, http://blogs.discovermagazine.com/...-poser/#.Ui4xMn_3Prg -- the rectangle with the random dots looks less random (to the uninitiated) than the rectangle with dots spaced more evenly.


Bertt  (D 99999)

Sep 9, 2013, 2:25 PM
Post #6 of 14 (2858 views)
Shortcut
Re: [Deimian] "Clustering" of cutaways [In reply to] Can't Post

Cutaways are not random. That is, they are not evenly distributed among all skydivers. Some people pack more carefully, some less carefully. Small, elliptical canopies that turn faster also spin up faster than big, square canopies. When someone pulls lower, they have less time to fight a line twist or stuck slider than someone who pulls higher. Makes sense that you might see clusters of cutaways at a DZ depending who comes out on a particular day.


GLIDEANGLE  (D 30292)

Sep 9, 2013, 5:55 PM
Post #7 of 14 (2654 views)
Shortcut
Re: [Deimian] "Clustering" of cutaways [In reply to] Can't Post

Jump volume plays a role too. Assume that the rate of malfunctions per 10,000 jumps remains steady. If the rate of jumps being made at a DZ can affect the "apparent rate" of malfunctions. I see this frequently when the DZ gets busy on a summer holiday boogie. The number of malfunctions / weekend goes up as the jump volume goes up. It appears that there is an increased rate (per 10,000 jumps) but there really isn't.

The rate of malfunctions is also affected by the canopy mix of the jumpers. If we have an influx of folks with fickle high performance canopies, the rate of malfunctions goes UP, if however the canopy mix is more docile... the rate of malfunctions goes down.

Of course, not all cutaways are due to malfunctions! I remember a 4 day CReW boogie which had ~10 reserve rides among the ~40 CReW dogs. All of those were due to wraps, not malfunctions.


hcsvader  (E 2952)

Sep 10, 2013, 9:49 PM
Post #8 of 14 (2187 views)
Shortcut
Re: [Deimian] "Clustering" of cutaways [In reply to] Can't Post

Sometimes there are just more air gremlins in the area.


skybill  (D 6009)

Sep 10, 2013, 10:01 PM
Post #9 of 14 (2166 views)
Shortcut
Re: [Deimian] "Clustering" of cutaways [In reply to] Can't Post

Hi Demi,
'Just the "Reaper" takin' a couple of "Practice swings!"Sly


Deimian

Sep 11, 2013, 12:50 AM
Post #10 of 14 (2102 views)
Shortcut
Re: [GLIDEANGLE] "Clustering" of cutaways [In reply to] Can't Post

Just to clarify, in these two days the mix of jumpers was not at all more aggressive than usual. It included tandems, students, weekend warriors and staff on fun jumps, neither of them particularly aggressive. The number of jumps per day was also not larger than usual. In fact last Sunday it was just half of the day, in the morning it was cloudy and rainy, so no jumping before 1 or 2 PM.

Also a significant number of those cutaways were tandems (3 or 4 in the two days), and packers have packed the mains in 4-5 of the cutaways. But at peaks of more than 100 tandems per day I am not surprised of that, I think last Sunday there were more tandem jumps than any other kind, so statically makes sense, even though tandems tend to have less cutaways than other kind of jumps.


potatoman  (Student)

Sep 11, 2013, 1:57 AM
Post #11 of 14 (2082 views)
Shortcut
Re: [Deimian] "Clustering" of cutaways [In reply to] Can't Post

On my very first skydive in '94 from C210. I was out last.
The first SL student went for reserve drills. So, the second followed suit, the 3rd, and then the 4th.Crazy

Only myself and the JumpMaster landed on mains.

Ii have also seen when a mal has gone at the club, that people tend to act a little bit "pre-mature" on EP, resulting in a couple for the day. BUT, not always.


GLIDEANGLE  (D 30292)

Sep 11, 2013, 6:06 PM
Post #12 of 14 (1838 views)
Shortcut
Re: [Deimian] "Clustering" of cutaways [In reply to] Can't Post

Deimian wrote:
Also a significant number of those cutaways were tandems (3 or 4 in the two days),

Ah... suspect tandem gear maintenance is the issue. A careful inspection of those rigs may reveal that there are some parts in need of replacement. I have seen this situation in the past.


riggerrob  (D 14840)

Sep 11, 2013, 8:36 PM
Post #13 of 14 (1698 views)
Shortcut
Re: [Deimian] "Clustering" of cutaways [In reply to] Can't Post

I see seasonal "peaks" with fatalities.

There are usually one or two fatalities during Christmas and New Years boogies.

The second peak occurs around Easter, when rusty jumpers do their first few jumps of the year.

Then there is a third peak late in the summer when everyone is "too current," "too cocky" and have neglected gear maintenance all summer.

In the autumn, we also see a peak in fatalities when people jump with thick gloves, bulky sweaters, etc. for the first time.


Deimian

Sep 11, 2013, 11:22 PM
Post #14 of 14 (1609 views)
Shortcut
Re: [potatoman] "Clustering" of cutaways [In reply to] Can't Post

potatoman wrote:
On my very first skydive in '94 from C210. I was out last.
The first SL student went for reserve drills. So, the second followed suit, the 3rd, and then the 4th.Crazy

Only myself and the JumpMaster landed on mains.

Ii have also seen when a mal has gone at the club, that people tend to act a little bit "pre-mature" on EP, resulting in a couple for the day. BUT, not always.

That was my guess. Even though I can't say that any of the cutaways were not necessary.

GLIDEANGLE wrote:
Ah... suspect tandem gear maintenance is the issue. A careful inspection of those rigs may reveal that there are some parts in need of replacement. I have seen this situation in the past.

I don't think so. Particularly on the tandems I think the reason for the cutaway was always twists (except one that was a drogue in tow, I am not sure about the reason behind), mixed with relatively long spots and the wind blowing them away from the DZ.



Forums : Skydiving : Safety and Training

 


Search for (options)