Pilot Chute Wear

wzettler

In reply to: Another disadvantage of F-111 is that it will wear out faster than ZP. Tom,
In skydiving, a (ZP) PC that is wearing out tends to hesitate a bit on throw out. Obviously this hesitation isn't something that would translate well to the BASE environment it being so less forgiving due to lack of altitude. (I doubt people want to wait for a hesitation.) How do you tell when the PCs in BASE are wearing out? Is it just visual inspection of the F1-11/ZP and the mesh of the PC and what each jumper is comfortable with? Do you only jump a PC X number of jumps? What are the "rules" here?

TomAiello

Re: [wzettler] non-Zero Porosity Pilot

In reply to: How do you tell when the PCs in BASE are wearing out?
I don't think there is a hard and fast rule.

I generally discard a PC the moment I start to have doubts about it. If the PC fails, the rest of that stuff on your back isn't going to do you any good, after all.

Thinking about when I've thrown out old PC's, it seems like I'm getting about 100 jumps from an F-111 PC and maybe 250 from ZP. But I'm pretty conservative on that (as I mentioned before).

Let me see if I can get some manufacturers to comment on this one.

base311

Re: [TomAiello] non-Zero Porosity Pilot

well... I've seen some pretty ragged-out looking PC's *cough* mike *cough*

More than anything I would make certain that the PDA line and apex are within tolerances relative to the skirt: that's your biggest concern with inflation of the PC. I've seen some damn-scary PC's where the apex came down below the skirt. See paragraph 4 of Bill Booth's reply in this thread.

To quote:

In reply to: "OK, now the easy part. If you want your pilot chute to always function properly, simply make sure, in the inflated state, that no part of the skirt is above the apex. In other words, make sure neither your centerline nor your kill line is too short. I pulled the apex on my hand deployed pilot chute for two reasons. 1. It makes them open faster. 2. It yields 11% more drag. However, IF THE APEX IS PULLED DOWN BELOW ANY PART OF THE SKIRT, THE PILOT CHUTE WILL NOT FUNCTION PROPERLY.

How do I check that? First cock you pilot chute like you would during packing. Now hold your pilot chute UPSIDE DOWN by the bridle at the base. Simultaneously pull downward on the apex (handle) and each support tape where it touches the skirt. The apex should be equal to, preferable slightly "below", but never "above" the skirt. (Please remember, the terms "above" and "below", in quotes, refer only to the "upside down" pilot chute you are holding in your hands for this test.) Now look how your support tapes are sewn to the mesh. If they are sewn "on the bias" your pilot chute is properly constructed. If they are not sewn on the bias it means that the mesh halfway between each support tape IS on the bias and will stretch more than enough to allow the skirt to get way "below" the apex. Try it. It's like a round parachute with several different line lengths. It simply doesn't work very well. This extremely common construction error might not let your pilot chute fully inflate, or in extreme cases, inflate at all. If your pilot chute is "borderline" when it is new, then things will get worse and worse as it ages.
These things may seem obvious to the experienced, but I'm posting it here for the newbies. Obviously there's no kill line to deal with on a base PC, but the centerline (what I call the PDA line) length is critical (if exists). If your hook doesn't work on a BASE jump, it'll ruin your day.

Gardner

TomAiello

Re: [TomAiello] non-Zero Porosity Pilot

In reply to: In reply to: How do you tell when the PCs in BASE are wearing out? Let me see if I can get some manufacturers to comment on this one.
Here are some responses from manufacturers:

Jimmy Pouchert, Vertigo:
In reply to: There are no "set" retirement numbers for PC's. Like a canopy, when you notice decreased performance, it is time to retire them. Trying to blow air through the fabric is the best test to determine the porosity of both a canopy and a pilot chute. The advantage to ZP, is that the fabric maintains the same "lack" of porosity for a much longer time than F-111. The problem with an F-111 pilot chute, is that you really don't notice the lack of pull force until you have a hesitation. Hopefully this is on a jump which will allow you this hesitation, obviously. The vented pilot chutes are great because you get the longer life span of the ZP with the benefit of a consistent airflow through the apex, jump after jump.
Adam Filipino, Consolidated Rigging:
In reply to: Gardner made the point about PC trim. This is probably the most relevant. Fabric porosity and strength will degrade through time. In part because of use cycles but largely due to handling, UV and dirt exposure.

There is a threshold when your PC is more likely, or even prone, to structural failure due to these factors. However, much sooner than that will come the issue of trim. Through use and or other factors (water for example) pilot chute materials, load tapes and the centerline can change dimensionally. When this happens the PC has potential to lose performance or begin to behave erratically.

So.... when to retire? Some people do it on a schedule. This makes a lot of sense. Think of it as routine, preventative maintenance. We all do it on our vehicles. We change the oil on regular intervals rather than wait for failure. 75-100 jumps would be about right.

The degradation will occur gradually so regular inspections won't reveal a little red flag that says "replace me now" . There are some markers that can be observed that will let you know things are degrading. When the symmetry of the pilot chute load tapes begin to decline is a good time. About 2% (or .50" on a 42"PC) is when things will get weird. Also keep an eye out for stitch holes in the fabric fatiguing, especially near the apex cap. Pay attention to the centerline attachments and the main (circumferential) seam.

Retirement for ZP vs F-111? ZP will last significantly longer but when it goes it's likely to go big.

It should be noted that most contemporary PCs are so over built that structural failure is not so likely. Through time, degradation of performance and reliability become the factors.
I love being involved in a sport that's small enough that you can get responses from gear manufacturers in less than a day.

Thanks Jimmy and Adam!

TomAiello

Re: [wzettler] Pilot Chute Wear

I've split this off the "Non ZP PC" discussion, because it looks like useful information, that many people probably don't know (I've often seen PC's with many hundreds of jumps).

TomAiello

Re: [TomAiello] non-Zero Porosity Pilot

A short summary (in my words) of the manufacturers responses:

Approximately 100 jumps is a good time to start thinking of trading out a PC. This is especially true on F-111 PC's. ZP PC's can last much longer (sometimes as much as twice as long).

PC wear, like canopy wear, will depend on usage, and conditions. Getting a PC wet will contribute to wear, as well as degrading trim.

Check for worn stitch holes, shrunk lines, or porous material.