do you pop your reserve for repacks??

[dterrick 0]

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even if you average 1 mal per 500 jumps, and your main and reserve are equally reliable, you'd need to make something like 120,000 jumps to have a 50/50 chance of having a reserve mal.

Interesting numbers, Bill, but I disagree about the 50/50 part as EACH JUMP is discrete making the true probability 1/500 x 1/500 = 1/250,000. In all but entanglements, main and reserve activations are also discrete events validating the multiplication principle.

There. I feel TWICE as safe now.

Let's not get into the rocket science level descussion about improper procedures - that's up to US to avoid in the first place through ...what else... "safety and training" like this forum.

Dave

Life is very short and there's no time for fussing and fighting my friend (Lennon/McCartney)

[DutchSkyCam 0]

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I think the primary reason you don't see more double mals is simple statistics - even if you average 1 mal per 500 jumps, and your main and reserve are equally reliable, you'd need to make something like 120,000 jumps to have a 50/50 chance of having a reserve mal.

Whoo, that's a bold statement...

if one in 120.000 jumps ends in a dubble-mal... Statistics would look a lot different than thay do now.

Maybe packing (folding the parachute) can be the same, although everyone knows that pro-packing gives you a higher chance of line-over malfunctions.

which part of the malfunctions are to blame on packing error?
Twist because of bad body position,
Totals because of uncocked pilot,
Broken lines, damaged parachute,

On a 7 cell, square parachute that is rarely used and properly packed jou simply have a better chance of a good opening than on a 800 jump, no-reline, X-braced canopy loaded at 2.5.

[Mad47 0]

Wow! My teammates are onl-line
I saw the sweet opening of your reserve last weekend

[billvon 2,991]

>Whoo, that's a bold statement...

>if one in 120.000 jumps ends in a dubble-mal... Statistics would look a
>lot different than thay do now.

I agree, it was not intended as an attempt to explain actual incident numbers, just an example to show that you don't need a perfect reserve to get good reliability numbers. In many cases, the main and reserve parachutes are not designed to the same level of reliability - a Stiletto 120 is a lot more likely than a PD113 to spin up on opening, so my claim that the main and reserve are similar often isn't true. Also, in the case of a good packer/good gear/reliable design of main, I'd be willing to bet that the odds of a mal were well above 1 in 500.

>Maybe packing (folding the parachute) can be the same, although everyone
>knows that pro-packing gives you a higher chance of line-over malfunctions.

Interesting, since I propack my reserve. It's a quite different procedure than propacking my main, but it starts and ends the same way. Pure flatpacking has its pros and cons - it's easy to not notice a canopy hooked up backwards when flatpacking, for example.

>On a 7 cell, square parachute that is rarely used and properly packed you
> simply have a better chance of a good opening than on a 800 jump, no-reline,
> X-braced canopy loaded at 2.5.

Other than the rarely-used part I'd agree. New parachutes are not notably more reliable than well-maintained used parachutes; indeed, there is value in jumping a parachute that has been used before (it's been tested.) Note that, for a good part of my skydiving career, your description of a reserve applied to my main. In the hands of someone experienced, I would suggest that a properly maintained rig with a square reserve and a Triathalon main will have similar levels of reliability whether the main or reserve is used to stop your freefall.

[chutingstar 1]

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My current rigger usually complains about it but I do it anyway. Everyone should....especially if you haven't had a reserve ride on THAT rig. You need to know what it's like to pull your handles. Time before last it kinda scared me when I just tried to yank on the Cut away without peeling it first. Slipped right out of my hand. I definately practice peeling FIRST now.

I've written several articles on this subject on my web site www.chutingstar.com on the Rigger "Rant and Rave." I'll post the most recent one that deals with some of these issues...

21-Oct-02 — Actually pulling your cutaway and reserve handles on the ground just before a reserve inspection and repack is a great idea and highly encouraged by Chuting Star Rigging Loft. A jumper should put the rig on, snugging down the leg and chest straps as if they were about to jump. You can then go through a malfunction scenario in your mind as you throw out your main, followed by an arch, cutaway and reserve deployment. I have seen jumpers who struggled with a cutaway on the ground as they forgot the need to peel the velcro first. I have also witnessed jumpers who tried to push upwards on the handles (increasing the pull force) instead of pulling downwards. Recent comments and postings on the newsgroup rec.skydiving encouraged jumpers to pop their reserve when leaving a rig for a repack to ensure the rigger actually repacks the reserve and doesn’t just sign the packing data card. If that makes you feel better, that’s fine, but most riggers do inspect and repack every reserve. If you have doubts, then maybe you should find a rigger you trust a little more. Most riggers will let you watch, which is also an option for those that doubt a rigger is actually inspecting and repacking a reserve. But please don’t drag your open main up to the loft to cutaway, pop your reserve and leave the whole tangled mess for your rigger to sort through. Let your rigger inspect the closed container before you practice. An inspection/repack at the 120-day required FAA cycle (without a reserve ride) allows a rigger to inspect the loop length with the reserve closed to see how the pack job settled and make adjustments for the repack. When you pop the reserve before letting your rigger inspect the closed container, you take away that valuable advantage. Also, if you deploy your reserve in a loft, riggers generally like to remove the lead seal before you pop the reserve so it doesn’t accidentally end up in your reserve container or canopy.

Mike

ChutingStar.com

[deeblek 0]

My rigger insists that i pull my handles before i give it over. I like that and him. Period.

[skydiverbob 0]

Mine does this also, he makes a point of bringing all of the students around so they can see how it works, see the opening sequence and how it leaves the container. I think this is a good idea, probably is reassuring for them.

Who Dares Wins

[kallend 2,027]

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even if you average 1 mal per 500 jumps, and your main and reserve are equally reliable, you'd need to make something like 120,000 jumps to have a 50/50 chance of having a reserve mal.

Interesting numbers, Bill, but I disagree about the 50/50 part as EACH JUMP is discrete making the true probability 1/500 x 1/500 = 1/250,000. In all but entanglements, main and reserve activations are also discrete events validating the multiplication principle.

There. I feel TWICE as safe now.


Dave

I don't think you read carefully enough what he wrote.

...

The only sure way to survive a canopy collision is not to have one.

[billvon 2,991]

>Interesting numbers, Bill, but I disagree about the 50/50 part as
> EACH JUMP is discrete making the true probability 1/500 x 1/500 =
> 1/250,000.

I agree, but if your odds on each jump of having a mal are 1 in 250,000, at the 120,000 jump mark the likelihood of it happening to you approach 50%.

Or I could just be remembering my probability and statistics class all wrong. That was a long time ago.

[dterrick 0]

John,

Fair enough comment but I DID read Bill's post ... perhaps too carefully. Not to nit pick (damn I can be analytical sometimes) but I DID crack my college texts and do some research because I personally thought that what Bill wrote might lead some people to form invalid conclusions.

Since this is the Safety and Training Forum I thought my clarification might be relevant to the thread. We certainly don't need pepole thinking their chances of a double mal actually INCREASE with jump numbers. Conversely, we don't need people thinking it can't happen to them because they only have 50 jumps and "a main mal comes along only every 500 so a double mal will never happen to me".

My initial point, perhaps equally unclear in the interest of brevity, was that the probability of a double mal on jump #121 is (and should be) completely and exactly the same as on jump #122 or on jump # 1,022 provided no user-controllable variables change. (The fact, however, is that they do)

The scenario Bill presented ...
***you'd need to make something like 120,000 jumps to have a 50/50 chance of having a reserve mal.***

would have been accurately written as " by the time you and a friend have each done 120,000 jumps, one of you has a 100% chance of having experienced a double mal. That double mal has an equal chance of having been on jump #1 as on jump # 120,000.

I think the whole issue could and should be looked at from another angle: We have some control over our primary equipment's functionality in packing AND on deployment. Anything we do to make them more reliable reduces the odds of needing to go to backup equipment - equipment over which we have little or no control.

[is my reserve more or less likely to open if I've had a main mal? Answer: there should be no change unless you've not left your reserve enough time to open.]

Pull. Pull Stable. Pull stable at the apropriate altitude. Tip your rigger.

Dave

Life is very short and there's no time for fussing and fighting my friend (Lennon/McCartney)

[billvon 2,991]

>We certainly don't need pepole thinking their chances of a double
> mal actually INCREASE with jump numbers.

Uh, they do. The odds of seeing a double mal increase with jump numbers. Heck, same with injuries - if you talk to someone with 5000 jumps they have probably had a serious injury; odds are someone with 50 has not. That doesn't mean one is more injury prone than the other, it's just that one has had more opportunities to hurt him/herself.

However, if someone absolutely doesn't want to be injured, jumping less often (but often enough to stay current) will reduce the chances of his being injured - especially if he takes care to jump only in good conditions.

> . . .would have been accurately written as " by the time you and a
> friend have each done 120,000 jumps, one of you has a 100%
> chance of having experienced a double mal.

Well, not really. You never get to 100%. (Another way to look at it - how many times do you have to roll the dice before you can _guarantee_ you get a 12?)

>That double mal has an equal chance of having been on jump #1 as
> on jump # 120,000.

Quite true. The jumper at jump #120,000 is simply more likely to have experienced one than the jumper who has 100 jumps, based purely on statistics. You can, of course, modify these to reflect realities of those numbers (i.e. someome with 100 jumps may not be as good a packer as someone with 120,000, so on jump 101 and 120,001 the less experienced jumper is more likely to have a mal.)


> Anything we do to make them more reliable reduces the odds of
> needing to go to backup equipment - equipment over which we have
> little or no control.

I would argue that you have as much control over your reserve as you want. It is quite possible to pack and seal your own reserve; you just have to pass a test. Even if you don't want a rigger's ticket you have a lot of control over who packs your reserve, the type of reserve and container you buy, how the gear is handled and stored, and how often it's replaced.

I agree though that it pays to have a very reliable main parachute system. That's one reason I wouldn't buy a small stiletto - to me, the performance increase is not worth the increase in the chances of having to cut away an otherwise good main.