Pulling Reserve!!!!

[Jimbo 0]

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I realize your reserve can malfunction i was only saying your main is more likely to malfunction than your reserve.

I don't know if that's exactly true or not. If we assume that your main malfunctions once every 500 jumps, could we also assume the same for your reserve? I think I read somewhere (and who knows how true it is) that the reserve parachute malfunctions at approximately the same rate as the main parachute. The difference here is that you're much more likely to be jumping your main than your reserve.

Anyone with hard data who can validate or refute that statistic?

-
Jim

"Like" - The modern day comma
Good bye, my friends. You are missed.

[dreamsville 0]

You're gyping yourself out of an extra chance at life.

Harry

I don't drink during the day, so I don't know what it is about this airline. I keep falling out the door of the plane.

Harry, FB #4143

[crazy 0]

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Second yes,I accept the 1/500 chance of having the "wild" unplanned ride, and I wouldn't accept the 1/1 chance of having a planned reserve ride with no backup.

Well, but you are going to accept this 1/500 chance of having the "wild" unplanned ride each time you will jump. If you do 1000 jumps, you take the 1/500 chance 1000 times. Alltogether, deciding to skydive is a much bigger risk than deciding to do one intentional cutaway. I'll do the (bad) math for you:

• chances to have a malfunctioning main = 1/500
  
• chance to die on a wild unplanned main malfunction = 1/1000 (approximately, from the fatalities stat)
  
• chances to die from a planned cutaway = 1/10000 (roughly, because it's planned, so you get rid of lots of shit, like cross checking the rigger's job, reducing the risk of blown cells and broken lines, more altitude, less stress, clear handles, no disorientation, no injuries...)
  

Assume 500 jumps/year and 1 intentional cutaway/year. Statistically, the risk is:

• 1/1000 to die because of a main malfunction during your 500 jumps
  
• 1/10000 to die because of the intentional cutaway
  
• 1.1/1000 total risk for main/reserve malfunction
  

Apparently, you have increased the risk by 10%, it's not really significant, given the error level of the assesment. You would easily change the figure with small details on a sloppy pack job for instance. The "if you don't trust your reserve, why do you jump in the first place" partially translate into: "if you don't accept the small (insignificant) risk increment of 1 intentional cutaway, why would you accept the huge risk of 500 jumps?".

Now, imagine that the intentional cutaway has a real training value, and that it will train to better reactions to emergencies. For instance, you might have a more realistic feeling of the risks, anticipate more, pull a bit higher, get used to the idea to actually pull the reserve... In that case, your intentional cutaway could reduce significantly the risk associated to malfunctions, maybe 20% less, reducing it to 8/10000. Then the overall risk, including the risk of the training, is a bit less. You can't deny the training value of an intentional cutaway, the only thing is that it's quite difficult to quantify the effect on the overall safety.

I'm not telling you that intentional cutaways should be part of your normal training, I'm just highlighting the fact that the evaluation of the risk is definitely nothing close to the blunt "an intentional cutaway is 500 times more dangerous than pulling the main".

bb

--
Come
Skydive Asia

[franck102 0]

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Well, but you are going to accept this 1/500 chance of having the "wild" unplanned ride each time you will jump. If you do 1000 jumps, you take the 1/500 chance 1000 times. Alltogether, deciding to skydive is a much bigger risk than deciding to do one intentional cutaway.

I fully agree - but I get much more fun out of my 500 jumps than I would from the intentional cutaway. It's just a risk / reward thing.

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(roughly, because it's planned, so you get rid of lots of shit, like cross checking the rigger's job, reducing the risk of blown cells and broken lines, more altitude, less stress, clear handles, no disorientation, no injuries...)

I hadn't considered that - I guess you can lower the risk with good preparation. Not by a factor of 500 though I hope, or I am going to have my handles replaced and hire a team of riggers to do my repacks -)

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Now, imagine that the intentional cutaway has a real training value, and that it will train to better reactions to emergencies. For instance, you might have a more realistic feeling of the risks, anticipate more, pull a bit higher, get used to the idea to actually pull the reserve...

Good points, I don't have the experience to judge that, which is why I didn't directly reply to the original question.

Franck

[superflie 0]

OK, I can't stand it any longer. This is conditional probability - the math works out like this:

First the assumptions:
1) Odds of a main malfunction 1:1000
2) Odds of a reserve malfunction 1:1000
3) Each is an independent event

Therefore, odds of having both occur on the same jump is 1:1000000. This statistical result roughly corresponds with the data that we see on the skydiving fatalities query page. If we have 3,000,000 skydives in a year, you would expect to see 3 double malfunctions in that year. We see an average 1.7 since 1996 (but with only partial data from 02).

The odds for the main malfunction are, I think, generally accepted to be around 1:1000. To be conservative, I set the same odds for the reserve.

However, there are two additional points to be made. First, the odds of having a malfunction if you only deployed your reserve would be 1:1000. Second, this sport should be about understanding and controlling risk. Know the risks and make decisions based on your comfort-level with them and your ability to mitigate them. Personally, I have done an intentional cutaway on my normal rig. It was fun.

[Jessica 0]

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I think I read somewhere (and who knows how true it is) that the reserve parachute malfunctions at approximately the same rate as the main parachute.

I couldn't find any statistics, but I really really doubt this. The main is packed quickly and often by inexperienced people; the reserve is packed slowly and carefully by a rigger after a meticulous inspection. That alone would influence the malfunction rates.

Add a deployment system designed for speed and to compensate for instability, and I'll bet the reserve malfunction rate is much lower than that of mains.

Of course, my logic may be flawed, and I'm not taking into account main-reserve entanglement issues.

Skydiving is for cool people only

[Iflyme 0]

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The odds for the main malfunction are, I think, generally accepted to be around 1:1000

Not trying to be difficult here, but I kinda thought it was closer to 1:700 ... Personally, I don't think I'd cutaway my main just for the rush...