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At Sunday after 1 sec delay canopy slided back few meters and then started to fly. I sent video mov00046.mpg to http://www.skydivingmovies.com. Any ideas about what could cause it?

did you have a deep brakes setting? is it optimized for you?

Yep. Deep brakes for slider down. But wasn't like stall. Canopy just open with leading edge much higher then trailing edge and i swung back like pendulum. Then it was fine. Second jump that day was perfect.

 

But why it was fine on other jumps?

It could be a deployment stall. Deployment stalls will often occur sporadically if the deplyment brake setting is just a little too deep. Things like airspeed , winds etc will be the deciding factor as to whether or not the canopy actually experiences a stall or not.

However, something we experiencd in testing on the Ace and Black Jacks could also be occuring.
I didn't look at your movie. Do you have a canopy with 5 upper control lines per side?

What you are desrcibing (if it is not a stall) is a common by-product of the 5 upper control line configuration.

When controling 2.5 cells of the tail per side, the canopy's trailing edge is almost completely tensioned. It is almost like the skirt of a round parachute. What can, and has happened, is that the high-pressure mass of air under your canopy actually vents to the front at line stretch. This causes the canopy to pitch backwards.

Aerodynamically, is not stalled but geometrically it has a positive angle of attack. It will then pitch forward and fly off as if nothing happened.

Originally, we brought this under control with the Ace and Black Jack by simply using shallower brake settings.
However in recent months we have gone one step further.
These canopies still use a 5-line setup but, now only controlling 2 cells per side.
This configuration has softened openings, and improved heading performance-especially with a slider. By retaining 5-control lines, turn and flare response is largely unchanged but openings are better in every way.

If you have an older Ace or BJ, we have a free retrofit kit that you can request.

Regardless of what brand canopy you have, I would first determine if it is a true aerodynamic stall or not and then examine your options. In the short term, I would suggest using the shallowest of the available brake settings

Thanks
Adam Filippino
Consolidated Rigging

That's pretty interesting. Did you notice it more at certain delays? Silder up or down? Do you think it could be a common feature of all 5-line canopies, not just the Ace and BJ?

Gus

I have FoX 245 with two brake settings (deep and shallow), loaded at 0.67. It's old style FoX without vents and with 4 upper control lines. Vere experienced jumper watched opening from edge (behind my back) and he also saw video (camera man was 20m on my rigt side) and he does not think it's stall. It was very similar to what you described (positive angle of attack).

Gus, We found the scenario I mentioned was more likely to occur on slider jumps, which is not surprising given what a slider does to a canopy during deployment.

I believe it can happen regardless of canopy but if for example a different canopy has a steeper trim or different airfoil than the Ace, those things may mitigate it so it won't be very likely to occur.


BR's Vtec canopies had this rocking thing going on and I was told they attributed it to air coming in from the lower surface vents then out the nose. This could be.

I think they went with shallow brakes to solve the issue. Which is really the heart of the issue. If the canpoy moves forward on deployment it will not tend to rock back.




Adam Filippino
Consoidated Rigging, Inc.

I would suggest verifying line trim. For several reasons canopies tend to get "flatter" with age.

From there I would experiment with shallower settings to see if this makes the problem go away. I would expect that just a small change (3-6cm) in combination with a properly trimed canopy would stop it from happening with out generating excessive forward speed.


Have you checked w/ BR?

Adam Filippino
Consoidated Rigging, Inc.

http://www.skydivingmovies.com/...ion=file&id=1849

Dave

Where do you have your hands when the canopy opens! I know it is hard to tell if you did something different with your hands on those two jumps. But it can be possible the wind conditions, what you did with your hands during opening, and the canopy trim. I used to jump a old Pegasus base modifyed brake settings, and it worked just fine, except from those jumps I touched the rear risers, and experienced simular openings!

This has happened to me twice now also. Once on a Fox VTEC245 (which only has one setting) and once on a Troll MDV 260. I am surprised considering they are both vented.
Meeker

your vents wont prevent a stall,therefore the vents wont help you much.

too deep brake settings can give you a stall.

Thouse of you who experienced this,were it on a windy day or nil wind,i bet it were nil winds therefore theres no wind to puch you away(A as an examlpe).

Why are you surprised?
Just a few posts above yours Adam notes that:

"BR's Vtec canopies had this rocking thing going on and I was told they attributed it to air coming in from the lower surface vents then out the nose. This could be."
-Josh

My money is on the tailwind. Were you opening in a tailwind? And if so, had you opened in comparable tailwinds before?

It was completely calm. No wind at all. What could cause tailwind?

Was it a cliff?

Hmmm. Let me do some thinking. Do we have video linked somewhere here (I missed it, I think).

I had a very similar (but much more pronounced) experience jumping a prototype Blackjack several years ago. the canopy actually ended up underneath me as it recovered from the stall.

No changes at all from previous configurations, and no wind?

It was this most frequently jumped spot in our Southern France gorge (small ledge 8 m below edge of cliff). Video is in skydivingmovies.com, link is somewhere in thread. Same configuration for last three jumps (deep brakes + 48" PC).

I checked out the video. I haven't really studied very many deployments on video, but in the few I have seen, seems like the pc, canopy and jumper are all pretty much in a line. Is it common for the pc to be that far aft of the canopy during deployment? Maybe there was a gust, or some kind of pc ocillation? Or am I just seeing the pc fall down behind the canopy after it's done its job?

Hi Konass!

This is Karen from BR! We saw your post and would like to help you with your question. Could you please contact us at support@basicresearch.com with the serial number of the canopy, and how many jumps you think are on it? We'd like to look into the matter and see if we can help.

Adam made a good point that the age of the parachute can be a large factor. If the lines are stretching out of trim, all kinds of weird things begin to happen.

We look forward to hearing from you,
Karen & Todd
Apex BASE Perris
(formerly Basic Research)