F111 and ZP's in Turbulence

[hemphog 0]

Ok, so I'm about to get into jumping zero-p canopies. I was reading up on the differences and found they each have their own way to deal with turbulence, but I can't understand why this is.

CSPA Reccomendations in Turbulence:
F111 - Go to 1/4 brakes
ZP - Go to full speed

It makes sense to go to full speed under a ZP so to fill the canopy with as much air as possible to maintain lift, but why slow down an F111? What would be happening there?

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"Ya we'll rape the local objects, and maybe do some jumps too!"

[billvon 2,435]

>but why slow down an F111?

There are reasons to go to 1/4 brakes under both sorts of canopies, and reasons to go to full flight in both sorts of canopies. Since "1/4 brakes" is often considered 'old' advice people tend to associate it with 'old' canopies. In reality what works on one canopy will work on another canopy of the same size/design whether it's F-111 or ZP.

[nate_1979 9]

Quote

>but why slow down an F111?

There are reasons to go to 1/4 brakes under both sorts of canopies, and reasons to go to full flight in both sorts of canopies. Since "1/4 brakes" is often considered 'old' advice people tend to associate it with 'old' canopies. In reality what works on one canopy will work on another canopy of the same size/design whether it's F-111 or ZP.

Care to go into more detail on why you would ever go into 1/4 brakes on any canopy in turbulence? Or is that "old" advice because it's not the best way to handle it?

FGF #???
I miss the sky...
There are 10 types of people in the world... those who understand binary and those who don't.

[billvon 2,435]

>Care to go into more detail on why you would ever go into 1/4 brakes on
> any canopy in turbulence?

If the canopy has collapsed and needs to be reinflated, 1/4 to 1/2 brakes (i.e. deployment settings) is generally going to be the best way to get the parachute reinflated (IMO.) After all, that's how the manufacturer designed it to inflate in the first place.

[nael 0]

There's a lot of good info (and some bad) in this link. I know it looks like a mess but I'm not computer literate enough to make it neater. Just click it (hopefully I got that much right!).

http://www.dropzone.com/cgi-bin/forum/gforum.cgi?post=454920;search_string=turbulance;#454920

www.TerminalSports.com.auAustralia's largest skydive gear store

[nael 0]

Quote

If the canopy has collapsed and needs to be reinflated, 1/4 to 1/2 brakes (i.e. deployment settings) is generally going to be the best way to get the parachute reinflated (IMO.) After all, that's how the manufacturer designed it to inflate in the first place.

*Slight hijack*
Bill, can you clarify this a bit more for me? I was told canopies are designed to deploy in brakes so that if you have a collision on opening neither canopy is flying in full drive, and therefore it will not cause as much pain/problems/destruction to the other. No one ever mentioned that it was actually better for the aerodynamics of the canopy until now (or maybe I should have asked more questions).

You can reply via PM if you don't want to change the direction of this thread too much!
*end hijack*

www.TerminalSports.com.auAustralia's largest skydive gear store

[billvon 2,435]

> I was told canopies are designed to deploy in brakes so that if you
>have a collision on opening neither canopy is flying in full drive, and
>therefore it will not cause as much pain/problems/destruction to the other.

I think that's more of a side effect. Stowing the brakes (i.e. shortening the brake lines via the stow loop) radically affects how a canopy opens. On many canopies it speeds up the opening and makes it more predictable. By shortening the brake lines it also reduces the odds of a lineover. The lower forward speed is a nice effect though.

[Hooknswoop 19]

Quote

If the canopy has collapsed and needs to be reinflated, 1/4 to 1/2 brakes (i.e. deployment settings) is generally going to be the best way to get the parachute reinflated (IMO.) After all, that's how the manufacturer designed it to inflate in the first place.

I agree that brakes will speed up re-inflation, but disagree that you should go to 1/4-1/2 brakes before it collaspes. I think full flight in turbulence will help prevent it from collapsing, but if it does, then quickly go to 1/4-1/2 brakes. Flying in brakes increases the possibility of the canopy collapsing.

Derek

[TomAiello 25]

In his PIA presentation on turbulence, Scott Miller said that it's going to depend on the canopy. When I discussed it with him further, afterward, he said that he thought most big F-111 7 cells (obviously, that's my area of greatest concern) would handle turbulence better in part brakes, but most "modern" canopies would handle turbulence better in full flight.

Personally, my experience with BASE canopies (the only canopies I'm knowledgeable enough about to comment on) has been that almost all of them take turbulence better in part brakes. I _think_ the Ace/BJ airfoil may actually do better in full flight. I theorize that this is because it is more of a "modern" airfoil (per Scott Miller's comments at PIA).

Can anyone give me an idea of how long it takes a ZP skydiving canopy to re-inflate after a partial collapse? I realize that's a big range, but my thinking is that the longer the reinflation takes, the more important it is to avoid the deflation in the first place. Hence a canopy with snappier openings might reinflate quicker, and thus be one to fly in part brakes, where a canopy with slow openings would reinflate slower, and hence make avoiding the collapse in the first place (presumably by flying in full flight) most important. (Obviously this line of reasoning is in direct contravention of my observations of BASE canopies, where the Ace/BJ actually has the quickest openings I've seen, but also handles turbulence the best [of the BASE canopies] in full flight.)

-- Tom Aiello

[email protected]
SnakeRiverBASE.com

[billvon 2,435]

>Hence a canopy with snappier openings might reinflate quicker . . .

I would tend to disagree. Openings are mediated by a slider; there is no slider involved in reinflation after turbulence. One of the best canopies I've jumped in turbulence was a Triathalon; it sniveled a lot during opening, but reinflated very rapidly during the one or two collapses I had on it (during a Santa Ana in San Diego.)

[TomAiello 25]

Quote

>Hence a canopy with snappier openings might reinflate quicker . . .
I would tend to disagree. Openings are mediated by a slider; there is no slider involved in reinflation after turbulence.

Ooops. That's the BASE jumper not thinking about skydiving gear...

-- Tom Aiello

[email protected]
SnakeRiverBASE.com

[AggieDave 6]

Quote

Openings are mediated by a slider; there is no slider involved in reinflation after turbulence

It would come down to more of the overall canopy design, such as trim angle and cross porting, right?

--"When I die, may I be surrounded by scattered chrome and burning gasoline."

[nacmacfeegle 0]

"The lower forward speed is a nice effect though."

Another slight side track...
If the canopy is opening in half brakes, will that not also affect the canopy's propensity to spin up if there is an assymetric inflation? EG one side of the canopy going to full drive before the other is fully inflated?

Sorry to side track folks.

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He who receives an idea from me, receives instruction himself without lessening mine; as he who lights his taper at mine, receives light without darkening me. Thomas Jefferson

[Designer 0]

Good advice Bill.

[billvon 2,435]

>It would come down to more of the overall canopy design, such as
>trim angle and cross porting, right?

I don't know. Cross porting has a lot to do with full inflation but not as much to do with bottom skin inflation, and I think you'd want that to happen first; that's often what you see first when a BASE canopy packed slider-down inflates. But there are a lot of inherent differences between BASE canopies and skydiving canopies so I don't know if that's valid.

The best thing you have going for you is that the canopy really, really wants to stay open; any turbulence bad enough to cause a collapse will typically start dropping you, and that puts the relative wind back beneath the canopy where it's in a better position to reinflate.

[upndownshop 0]

I agree that brakes will speed up re-inflation, but disagree that you should go to 1/4-1/2 brakes before it collaps. I think full flight in turbulence will help prevent it from collapsing, but if it does, then quickly go to 1/4-1/2 brakes. Flying in brakes increases the possibility of the canopy collapsing.

Derek

[tbrown 26]

It would come down to more of the overall canopy design, such as trim angle and cross porting, right?

[pchapman 262]

I feel one valid reason to use a very small amount of brake is to get a better feel for the pressurization of the canopy.

If the toggles are up against the guide rings, changes in the canopy will not be felt as well as if the brakes are pulled down a little bit, putting brake line tension on the canopy. Depending on the toggle settings, the first couple inches of brake travel may only be taking the slack out of the brake lines.

So one has to be careful of whether "brakes" is being defined from the hand-position or canopy-aerodynamics point of view. A jumper could be following the recommendation to leave the canopy in full flight and unbraked, yet be "using brakes" in that they've moved their hands down a couple inches.