Colapsible Pilot Chute vs. Non

[txhoss 0]

Just a new jumper wondering what the difference between the colapsible pilot chute and the non is. This may sound like a stupid question but if you forget to "cock" it, it will not catch air and you will end up with a mal so why put yourself in that place? What is the benifit to having a colapsible one then?

Have Rig will travel ...

[larsrulz 0]

The following is from an email to a follow jumper from John LeBlanc, the chief designer at PD. It covers the performance loss from a non-collapsible pilot chute and benefits from a collapsible:

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It is quite common to not understand the problems associated with an inflated pilot chute on big canopies. What people don't understand is that it is not just the amount of drag produced by the pilot chute. The bigger issue is where that drag is applied: to the top of the canopy in a backwards direction. Having the drag applied here causes several things:

First, it attempts to rotate the canopy back into a flare, thus reducing the amount of flare power remaining.

Second, this "dragging through the air" flight regime makes the canopy bounce around more in light turbulence, making it more difficult to get the canopy to fly a smooth stable approach at a constant airspeed. (A smooth steady state approach is a big help in getting consistent landings.

Third, this extra drag tends to make the canopy flare a bit when making quick heading corrections on final approach. Eventually, that canopy noses over slightly and gains speed again, only to repeat this oscillation a bit more mellow. This makes timing the flare a big challenge, as the best flare from each stage of this oscillation is a bit different! This problem is much more pronounced on bigger canopies, especially those that have a larger section of tail pulled down by each control line, such as PD bigger than 190, Sabres bigger than 190, and all tandem canopies.

Fourth the pilot chute can distort the canopy as the end cells try to out fly the center cell. You can sometimes see this as a bend in the canopy at the center cell, when looking up at it in flight. This causes a change in angle of attack in specific areas of the canopy. It results in more lift being generated in the center cells, but less lift being generated by the end cells. This causes the end cells to be loaded too lightly, making them more prone to folding under from a side gust or downdraft in turbulence. This situation is aggravated by using quick toggle movements to make small heading changes, especially when there is a left, right left sort of thing going on with the toggles. (I know this sounds sounds silly, but watch people on final approach and you'll see this a lot.)

The Collapsible pilot chute will be of benefit to this jumper in a few ways:

First, the canopy will be less susceptible to turbulence.

Second, the canopy will have a more effective flare, particularly when making less than optimum approaches when small corrections are made during the last 10 to 15 seconds. (Its best to plan approaches so that these corrections aren't necessary.)

Third, in the event that the jumper wants to learn about using front risers, the canopy will respond better in this mode, with less riser movement being required, and more potential gained. This is because the adverse affects listed above become more pronounced with added airspeed, so vicious cycle starts to occur: The jumper doesn't get much out of a bit of front risers, so he pulls more riser, which causes more drag on the pilot chute which rotates the canopy back more which gives less effect which causes the jumper to pull more front riser and so on.

Collapsing the pilot chute will produce little extra airspeed at normal full glide, but it will change the handling and effectiveness of the flare. Making sure the brake lines aren't pulling down the tail too much is another. On the Sabre 230, a slight amount of tail pulled down is ok. (Check our web site for trim specs.)

Collapsible pilot chutes are not only for the small high performance canopies, but also help conservative jumpers using conservative canopies to get more out of them. They are particularly important on older F-111 nine cell canopies, such as the PD series. There isn't much excess energy brought to the flare on these old canopies. My recommendation to get rid of the pilot chute has helped many people get better landings on these canopies. The difference in flare power is a bit less noticeable on the Sabres, but it is there.

[...]

I would like to point out that these effects are real, and removing the pilot chute will produce more consistent canopy piloting performance. Experienced test jumpers on our staff get far better and more accurate results with a collapsible installed. And if you don't have your equipment set up properly, how will you get the experience needed?

Once you've worked out the steps to create a state of continuing improvements in technique, there is probably no other thing that has a bigger effect than collapsing the pilot chute, other than making sure the brake lines are set with too much tail pulled down at full glide.

Please let me know if this helps.


Regards,

John LeBlanc
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This explains both the benefits of the collapsible pilot chute and the detrimental effect of a non-collapsible!

Edited to remove some information specifically directed to the recipient of the email at the [...].

I got a strong urge to fly, but I got no where to fly to. -PF

[txhoss 0]

Thanks, that is a great amount of info

Have Rig will travel ...

[phoenixlpr 0]

Khm. I`m going to be quite angry if I forget to cock, because that case I can not close my coontainer due to the hidden pin. So I have to start over the packing.

Just my your routine like:
-set the brakes
-unstow slider
-cock PC

[skymedic 0]

It's amazing how many times you use my Email....

Marc
otherwise known as Mr.Fallinwoman....

[D22369 0]

Larsrulz posted a great piece about it....

use a set procedure, stick to it......

what I do is... cock the pilot chute...stow the brakes, arrange the lines, cocoon it, S-fold it, put it in the bag, Double check the pilot chute is cocked...... I know I have added a second "unnecessary" step in cocking it twice.... but I know its done.

makes for more peace of mind for myself.

Roy

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

[ScottMcC 0]

I cock my pilot chute as soon as I lay the canopy down and a second time as soon as I'm ready to close the container, and I check the window when I'm placing the pin. Why? Not just to be redundant and make sure I did it, but because a friend of mine had a kill line that would constantly slip back to uncocked during the packing procedure. Mine doesn't have that problem, luckily, but adding 10 seconds to my sub-8 min packjobs isn't a big deal to me, especially to prevent a potentially very bad situation.

[riggerrob 562]

Since kill-lines shrink and fade, markings become meaningless after a while.
I do not trust markings on kill-lines.
I prefer to compare the relationship between the apex and skirt of a cocked pilot chute.
Others just give their pilot chutes a quick snap as they move them towards the BOC corner.
Same criterian, different test.

[skymedic 0]

Quote

since kill-lines shrink and fade, markings become meaningless after a while.

I don't think this is the case with the wings PC's...as the kill lines are made from kevlar and are sandwhiched with kevlar tape and then don't have the shrinking issue from what I can understand.
or am I horribly misconstrued about kevlar's properties. what do you think?

Marc

[riggerrob 562]

Icarus recommends simple pilot chutes when wing-loading is less than 1 pound per square foot.
Up to 1.35, they recommend bungee collapsible pilot chutes - to remove the "idiot packer" factor.
When wing-loadings exceed 1.35, Icarus recommends using kill-line pilot chutes, because as canopies get smaller, pilot chutes do not scale down as quickly and they become a larger - and more annoying part - of the total drag.

[riggerrob 562]

Quote

Quote

since kill-lines shrink and fade, markings become meaningless after a while.

>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>

I don't think this is the case with the wings PC's...as the kill lines are made from kevlar and are sandwiched with kevlar tape and then don't have the shrinking issue from what I can understand.
or am I horribly misconstrued about kevlar's properties. what do you think?

Marc

>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>

You are correct about Kevlar not shrinking, however, most other manufacturers use Spectra which shrinks dramatically.

[BlindBrick 0]

Quote

Icarus recommends simple pilot chutes when wing-loading is less than 1 pound per square foot.
Up to 1.35, they recommend bungee collapsible pilot chutes - to remove the "idiot packer" factor.
When wing-loadings exceed 1.35, Icarus recommends using kill-line pilot chutes, because as canopies get smaller, pilot chutes do not scale down as quickly and they become a larger - and more annoying part - of the total drag.

They must have change policies. My Safire manual recommends a collapsible with no mention of exceptions granted for wingloadings.


-Blind

"If you end up in an alligator's jaws, naked, you probably did something to deserve it."