Flying in turbulence, brake, no brake?

[jeanneretjerome 24]

I started jumping in 84, and I was always told to add a bit of brake while flying in turbulence. Now, with the new wings design/shape, i am asking myself if this practice is still valid with the Valkyrie, Velocity and others loaded wings. 

 

I am asking this question because in paragliding, we were also told to add a bit of brake, but today experts and manufacturers, are advising hands up in case of turbulence. I am flying acro PG and for sure adding even a slight amount of brake will immediately create a collapse.

Physics/research tends to support the brake, but these studies are old / based on very old designs.

 

Let me know your thoughts and fly safe.

[billvon 2,400]

A few thoughts:

The faster you go, the more pressure you have in the canopy, and the more resistant it is to collapse.  At the same time, the faster you go, the worse the turbulence you experience.  (Which is why aircraft slow down in severe turbulence.)

In general I think letting it fly is the best option in all but the worst turbulence.  In bad turbulence (i.e. the canopy is seeing minor collapses and it's hard to keep it flying straight) partial brakes puts you in the best position to reinflate if you do get a major collapse.  This is especially important near the ground, where you have very little time to reinflate if needed.

[wmw999 2,122]

I was trying to think of what I do; I think this is it. At least it makes instant sense to me

Wendy P. 

[lyosha 46]

This is a complicated question that you won't find an answer to in a skydiving forum because the paraglider equivalent of an A license obtained in the mountains had spent more time in "turbulence" than almost all skydivers.

The reality is as skydivers we jump in ideal conditions with virtually no turbulence. And as such do not understand it, do not measure our wing response to it, and have no basis for knowledge on how to react.

To get a real answer you need to understand the technique.

Google "active flying". There is a black magic to maintaining the half pound of brake pressure and why it helps manage your wing. 

But that is for a paraglider. Compared to paragliders, skydiving wings are poorly designed and twitchy.

Active piloting takes hours of flying in turbulence to get the muscle memory to not over control the wing and do more harm than good on a paraglider. Having kited a sky wing before I was left pretty dejected at the prospects.

I think stick to plan A: don't fly in turbulence.

Edited August 1, 2023 by lyosha

[jeanneretjerome 24]

Thanks lyosha.

You are right, but today in Europe, PG experts and manufacturers are not anymore promoting our well known half pound rule in turbulence.

The new school in turbulence (for PG) is hands up, dont touch the brake. The reason is the new wing design. All new wings are more stable hands up (no accelerator). A slight amount of accelerator or brake increase the risk of collapse. This is noticeable when flying our new toys like Enzo, Omega or acro wings.

So for PG, I now agree with this new school, but that was after many discussions/tests with SIV experts, professional pilots, and most important manufacturers/engineers and their computer simulations.

For skydiving, I am not convinced. Our wings are still basics (even my top swooping machine), and for these, the simple Newton equations demonstrate that brake add stability. 

So, are you still using the brakes in turbulence? Do we have facts/study supporting the hands up ? 

[pchapman 261]

Good question; this is a messy topic where we just don't have well validated procedures to use or teach. More so in skydiving than paragliding.

These are just my impressions, not necessarily better than others' thoughts. 

My method - brakes down enough to remove the slack only: As a sort of compromise, for skydiving I try the idea of pulling brakes down only to remove the slack in the brake lines, not to actually significantly brake the canopy. Just to have a tiny bit of pressure that one feels on the brakes, so one will notice if the pressure goes up or down all of a sudden.   (Even though it sounds like the latest in paragliding, according to jeanneretjerome, is that they don't even want that little bit of brake pressure -- at least with the latest designs. I'm not familiar with the latest in that field.)

Active flying: That allows for easier "active flying" in that one has a better feel for what is happening to the wing (PG terminology) or canopy (skydive terminology).  In keeping with the active flying concept, don't worry about the canopy bouncing around a little, long as the canopy stays within some box closely above your head (or where ever it should be based on whatever turning and banking one is doing). One doesn't need to control the canopy in that case, and yanking brakes here and there will likely just make things worse. Have seen that with people being too quick to use toggles on final approach to keep the canopy as stable as possible -- and lose airspeed which can result in a crappy flare especially when one might need extra when trying to land in turbulence, eg a last moment downdraft or loss of headwind.

Now if the canopy surges too far forward or tries to turn & dive suddenly, then one can brake as appropriate, as part of the active flying, to keep the canopy roughly in the right area. (But if the canopy surges back, one just has to wait it out as one doesn't actually have 'a little brake on', which one could let go to help accelerate the canopy forward.)

But still all that is just a subjective feel for what seems to be decent; it sure is hard to get well validated ideas on flying skydiving canopies.

Slight acceleration to pressurize the canopy, by using a gradual turn:  I also like that idea of being slightly accelerated in a gentle turn, if one is under a modern canopy, to keep the speed up to 'cut through' turbulence as one might get close to landing time.  I seem to recall Brian Germain first pushing the concept. A given size gust will make a smaller change in the angle of attack of a canopy, the faster the canopy is going. Although the 'continuous gradual turn' can conflict with all the strict "90 degree turn only" rules at many DZs, but a little fudging may be allowed as long as one isn't just whipping into a steep swoop turn.

(Without going into detail, a 5 mph gust won't change the vectors for speed and angle of attack as much for a 50 mph canopy than a 25 mph canopy. Although it gets messy looking at different situations. Gust downwards? Or horizontally from the front? With the canopy descending at an angle in a glide, how each affects the canopy depends on canopy dive angle, angle of attack, and speed. Lots of vector math to figure out different scenarios!)

General aerodynamics & risks of high vs. low angles of attack:  Our skydiving canopies are often trimmed fairly nose low for extra speed that translates into more flare power. So they might be at a bit lower angle of attack than paragliding canopies naturally are, I surmise. (Although even the PG canopies aren't expected just to be super floaty at a minimum sink speed -- they want some speed too, to get places and not go backwards in high winds. They can still use speed bar (think front risers) for extra speed, or brakes for slower floaty flying.)  So skydiving canopies with a lower angle of attack would take a lot of extra angle of attack before stalling at whatever their upper limit for angle of attack is.

With a lower angle of attack, one would then think that skydiving canopies are more susceptible to collapse from a too low angle of attack. Typically it might happen easier just on one side of the canopy than the over the whole front (a full frontal collapse in PG parlance).  I think that a low angle of attack collapse (rather than high angle of attack collapse = stall) is the one most likely happen to a jumper, and thus be the greater risk near the ground.

Still, our canopies seem more resilient than otherwise expected to frontal collapses, because the airfoils are pretty heavily forward weighted, with a lot of lift near the front of the airfoil. (To some degree that's the case with all airfoils, but with skydiving airfoils more front loaded than some other  airfoils).  After all, on most skydiving canopies one can front riser on one side pretty suddenly without collapsing the front of the airfoil. (I remember a couple scary old ZP skydiving canopies that were extra light on the front risers and one had to be careful with front risering; plus that made me uncomfortable with them in turbulence.) (PG pilots will I guess  note that when PG pilots fly, they can induce leading edge collapses more easily as they don't have combined A & B lines, but can pull down just what are effectively A lines alone.)

Slowing down in turbulence for airplanes:  They may do it, but that's because of structural limitations. In skydiving, we don't have canopies break from flying too fast. Although certainly the canopy fails by collapsing if it goes to 0g or below in effect, by going to a negative aerodynamic angle of attack and having the nose of the canopy collapse downward.

Slow vs. fast in general:  In general I'd rather be under a faster canopy that will be less affected by turbulence, 'cutting through it'. But if there is an actual collapse, one would rather be under something big and slow!   I'd rather be under  half of a Manta than half of a typical Valkyrie. In extreme conditions, even if the big slow canopy is more likely to collapse, it may still be safer under that canopy, with the slower speed and slower accelerations when not flying straight.

Dealing with turbulence vs. avoiding it:  Sometimes we get hit by turbulence and it would be good to know how best to deal with it. Still, the best strategy is to avoid getting into the situation in the first place.

It reminds me a bit about the debates about airlocked canopies, which were all the rage at one time, but for various reasons have faded away. One argument against them being the greatest thing ever, was that sure they might be a little safer in turbulence, but if you were likely to be in turbulence so strong that the canopy might collapse ...it would be better to stay on the ground in the first place, than trying to rely on your airlocked canopy to keep you safe.

 

 

 

[kmzamani 2]

On 7/31/2023 at 8:22 PM, jeanneretjerome said:

I started jumping in 84  , and I was always told to add a bit of brake while flying in turbulence. Now, with the new wings design/shape, i am asking myself if this practice is still valid with the Valkyrie, Velocity and others loaded wings. 

 

I am asking this question because in paragliding, we were also told to add a bit of brake, but today experts and manufacturers, are advising hands up in case of turbulence. I am flying acro PG and for sure adding even a slight amount of brake will immediately create a collapse.

Physics/research tends to support the brake, but these studies are old / based on very old designs.

 

Let me know your thoughts and fly safe.

 

Edited August 1, 2023 by kmzamani

[lyosha 46]

10 hours ago, jeanneretjerome said:

Thanks lyosha.

You are right, but today in Europe, PG experts and manufacturers are not anymore promoting our well known half pound rule in turbulence.

The new school in turbulence (for PG) is hands up, dont touch the brake. The reason is the new wing design. All new wings are more stable hands up (no accelerator). A slight amount of accelerator or brake increase the risk of collapse. This is noticeable when flying our new toys like Enzo, Omega or acro wings.

So for PG, I now agree with this new school, but that was after many discussions/tests with SIV experts, professional pilots, and most important manufacturers/engineers and their computer simulations.

For skydiving, I am not convinced. Our wings are still basics (even my top swooping machine), and for these, the simple Newton equations demonstrate that brake add stability. 

So, are you still using the brakes in turbulence? Do we have facts/study supporting the hands up ? 

Interesting.  I never made it to an Enzo/acro level, but hard for me to imagine flying the punchy, sharp-edged thermals of southern california without active piloting.  But I'm not a top-level PG pilot, so what do I know?

I go hands up in skydiving.  Try kiting the wing and see how easy/hard it is.  At least the wings I jump which are all the typical semi-eliptical ones most skydivers jump, they're twitchy and the inputs are unbalanced.

It was very straight forward how to fly my paraglider half-collapsed.  Literally zero effort.  I cannot imagine doing that with my sky wing.  I'm convinced it would fly like dog shit and would be extremely difficult to control.  So I stack the odds in favor of not getting a collapse - I try not to fly in conditions where I'll encounter mechanical turbulence or strong thermals, I fly hands up to maximize airspeed, and check wing surges, but that's about it.  I don't feel confident in what would happen if I tried to actively react to minor deflations.  And we all know to keep the wing flying straight and level as much as possible and flare (or try...) before you hit the ground in the case of a major event.

Kite your skydiving wing in some turbulence - see if it handles alright.  In my experience most don't because the manufacturers don't care and don't measure.  Their research $$$ is going into maximizing swoop distance, minimizing forward riser pressure, not into making a safer, more predictable and more refined (control-wise) wing.  In skydiving wings, "swoop" sells, "safer" does not.

Edited August 1, 2023 by lyosha

[timski 80]

stop over thinking it and just bury a toogle and get out of it!!! 

Seriously though, When things get bumpy I go home... As for getting to the ground in turbulence, Minimal input to the ground. Be thinking about your best PLF. Some of us have a leg up on you dirty nasty legs!!! 

[sfzombie13 307]

i usually do but got a hop and pop in from 3500 a few weeks ago to get current because that was what we could get.  i noticed some turbulence about 2k all the way up but didn't think much of it until i didn't get stable after 5 seconds, so i arched out harder and still went a little head down.  since i had to pull anyway i did and almost got knocked out.  saw stars and i think i got whiplash a little, still hurts some.  i was wondering what the hell happened that i couldn't get stable and finally figured out the turbulence was affecting me.  the other guy was current and d licensed and i haven't jumped since oct with my b.  now the landing was the best one i've had since last spring, stood up on the edge of the protangle and kited it all the way to the hangar.

[kcaero 3]

Para Flite use to include a section on turbulence in their manuals.