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Hey,

I just replace the delay by the speed (in km/h) in this image.
Take a Flysight or whatever, check your speed when pitching like you are used too and choose your PC with that data. Also use your camera smartly and get it to have some vids of your openings, if the bridle is bowing the PC is not enough big.
You may have to consider the weight of your canopy, I would say that this image is good for a 260(245 Atair) canopy.

I'm just getting this out because I see too much people who are buying 36" because it is the PC for terminal, but most of the wingsuiter are now flaring and have less than 110km/h when pitching, which is like a 4 seconds delay.
Would you put a 36" for a 4 seconds delay ?

Have good jumps !

I use a 36 and my pins pop before the pc inflates after that my lightweight 226 get pulls out to line stretch fine with the pc

Line stretch

Pins are almost always out before inflation whatever the PC size thanks to the bridle.
What is "fine" for you ?
What is your speed when pitching ?
How is your bridle during extraction ?
Is your canopy going straight up or is it falling a bit when it's getting out of the container ?

I don't pitch at the apex of the flare I pitch before it so I have more speed than waiting till you have nothing left. The canopy does not fall

This is what I'm talking about, not enough speed for that size of PC so the PC is not able to keep the canopy inline and the canopy "falls" a bit during extraction.

36" for tracking
38" for wingsuiting

It seems like (as with most things) technique may be more important than gear selection. Or at least having the right technique for your gear selection.

The power of the PC depends only on the air speed and its size, not matter the technique.
You do not choose you PC for slider down on your technique but on the delay. I do the same for slider up.

36" for tracking
38" for wingsuiting
This does not make any sense for me.
36" is my slick terminal speed (over 10 seconds) PC only.
If I'm tracking with a 2 pieces suit I will probably pitch at 160km/h, with my one piece it's more like 120km/h after flare.
30% air speed less and same PC ?
A big wingsuit after flare is at less than 100km/h air speed after flare, which is the same as a 3-4 second delay, I would not use a 38 for that air speed.

What's the technique changes for me is the way the opening feels, with the same PC you can have harder or softer openings.

The power of a PC is not a multiple of the speed, it's exponential.
I recommend a good reading of the graphs here:
http://base-book.com/.../graphs.html#graph38
You can see that at 120KPH a 38 has a 60lbs extraction power, at 160KPH it has a 110lbs power. That means that the same PC has half of its power when you pitch at 120 than at 160KPH. But you still want to use the same PC for these 2 air speed ?

I’ve used a 38 for a 2-3 second delay slider up many hundreds of times without an issue I guess a good question might be what is the required minimum force for extraction, and is it met be the gear configuration. I track 2 piece 32, one piece 36, large wingsuit 38. I switched from 36 to 38 around the time the Apache came out and suits got silly big.

I’m not saying you’re wrong, I’m just saying I’m not dead ;)

I'm not saying I have the exact right numbers, I just think I'm right about the logic.
If 38 is good for you for a 2-3 second delay it makes totally sense to use it for a large wingsuit.

Air Density, Air Speed, and Canopy Weight are the
variables one should use to choose Pilot Chute Size.

Also, it should be noted, that the amount of Drag
produced by different sizes varies by manufacturer.

Meaning, a 9 mm socket will fit every 9 mm bolt but
every PC of X size will vary a little, which honestly
does not really matter since the air molecules do
not know nor care what we call things.

If you can vary your air speed through technique, won't that change the power of the PC? Flare before pitch, pitch during flare, no flare, curl up in a ball and stop flying--different techniques would give different airspeed at deployment, and therefore each would have a different ideal PC, wouldn't they?

Your technique is changing your air speed, agree.

If you are flying at 140KPH and not flaring, or if you are flying at 180KPH and flaring until you are at 140KPH you will use the same PC, and 2 different techniques.

The only factor to choose the PC is air speed whatever the technique.

Curious, if a small girl with a 180 lightweight canopy and a large guy with a 300 sq ft standard canopy are both jumping a wingsuit and deploy at the same airspeed, should they use the same pilot chute?

No he stands corrected. Part of my point that he is not getting. I have a light weight 226 canopy so others jumping a bigger canopy with a 38 would be a good choice, while people jumping slider down with a 42 and a 1 to 3 second delay I would be fine with a 38

You can also read me totally.


Whatever other parameters (weight, size of the canopy) the CHOICE OF THE SIZE is only depending on the air speed.
Again the above tab is not the truth, it was not before I modified it, it is still not.

A small girl with a 180 lightweight canopywill not choose the same PC if she is pitching at 120KPH or at 160KPH, whatever the suit, whatever the technique, whatever the canopy (as soon as she is using the same canopy in this 2 cases).

Yes I think I got your point

Here is an other picture updated with some help.
If you think I should add or change things just let me know, It's still a work in progress.

One thing that could be added is a “time of delay” for low speeds as a lot of people jumping slider down probably don’t use fly sites. I like that your chart shows overlap and it’s not just “one size pilot chute or you’re dead”. It is an interesting concept as tracking use to just mean tracking, and now there’s a huge range of large suits and speeds when pitching. How consistent are you finding your speed at deployment is after the flare? Have you taken any data for others or with other gear? Nothing wrong with trying to understand things better to improve safety in the sport.

I'm regulary going on skyderby and look to others data.
There is the suit, the speed, I find it very interesting.
I prefer to have this chart just for slider up jumps, it is no written so I might be able to add some data like delay for slick jumps close to the speed. I don't want to put slider down in the chart I made because after looking to the first I post I find it a bit confusing.
My speed at deployment with my actual tracksuit is from 125 to 145KPH on most of my jumps after flare. With my big wingsuit it was more 90KPH.

Perhaps what we need is a different table for each canopy weight.

this is an interesting topic.
yuri guy would be probably better at this but just a couple of thoughts.
the graphs by matt are very nice, but they are basically "pinlocks" at various speeds. so what the pilot chute is doing, it's accelerating the canopy which has some mass. product of those two things should be force, if I remember correctly. once it starts accelerating the mass (in this case decelerating the canopy) it actually starts to lag behind as it's relative airspeed is changing and thus it's drag force, which depends on the square of the speed i think, should decrease (possibly substantially) gradually as the canopy is pulled up. i guess couple of differential equations which I'm too lazy/dumb to think about right now could show the way the pull force changes over time. it would be nice to see if it is smooth or oscillates for different setups. but basically what it influences is the time deployments take. and what is the proper time? since it usually "just works" and is quite robust in respect to the choice I'm not sure it's worth the time, but I would certainly read something more elaborate if yuri or whoever chimes in.

There you go. Just fill that up

Do you actually have a different table for each canopy weight ?
I'm talking about the table you (and others) are using for FJC.

Short answer? Yes.

During the Fundamentals course I draw up a "sample" PC size chart on the white board, and then give a discussion of varying canopy weights and PC size adjustments for those weights. I do not hand out a simple table, because I think it oversimplifies too much. I always discuss the idea that PC size should be related to canopy weight, and follow on with a discussion of how much difference there can be in weight between two radically different canopies, and how that results in different PC needs for different jumpers.

I also discuss how every jumper is basically walking around with their own personal "PC size chart" in their head, and how they are all slightly different, emphasizing that each student will eventually develop their own internal "version" of a PC chart, for themselves.

Nice !

I'm not doing a FJC but I'm trying to do the same with this table (and the text under).
The most answers I got about the PC choice are: "For the wingsuit it is the 36 that should be used" or even worst "it's a terminal jump so I'm using a 36"
So even if my table is not precise I think it's better than that, and if people are reading what is written under they start do make their own based on their canopy and the air-speed.