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How a rear riser stall differs from a braked stall? Rear riser stall seems to happen because of too big angle of attack which separates the airflow from the upper side of the wing so it cannot be diverted down at the end [reference „Understanding Flight” by Anderson & Eberhardt]. And it looks that way, as at first an airfoil still is pressurized, but want to „break” chord wise.

So how the braked stall (by pulling toggles) works and how both differs, because from experience I can tell that they look differently (braked stall looks more like a butterfly where an airfoil breaks span wise and end cells want to touch themselves), so it seems for me that they work differently as well?

It seems that when I pull toggles I increase drag in the tail section of a canopy, which in result pulls nose portion up increasing AoA. Also pulled toggles create drag via pulled fabric in the tail section which slows canopy's forward speed.

So does the braked stall happen because:

a) Airflow over the top skin separates from the wing and is not creating downwash at the end

b) The AoA is so big that the nose inlets are too high angled to let the air in (the bottom skin blocks it) to keep cells pressurized

c) Drag created by braked fabric in the tail and increased AoA (if increased AoA increase also drag which I don't know but it seems so) reduce canopy's airspeed so much, so there is less and less air coming into the cells to keep them pressurized. But why the center cell/cells seem to be better pressurized than the outer cells that are breaking to the inside?

d) All of them together in some proportions

e) Something else like the fact that brake lines are not placed in the center of the tail.

For me it seems like the reason is that the pressure in the cells drops by either option B), option C) or both of them, and then when pressure drops, brake lines have enough power to pull end cells inward as they are connected only at the outer cells end. But at that time, canopy still has forward speed, just not enough pressure. So this stall which we see in a shape of a „butterfly” is just the begining of a stall as there is still air coming into cells, but once the airflow will be blocked to the inside of cells by increased AoA (by the bottom skin) or by zero airspeed created by increased drag/AoA, then a canopy will totally collapse. But which one is it? Would a headwind let a canopy to be pressurized longer, as it could inject itself into the cells even when a canopy brakes to zero airspeed, like when you kite a canopy on the ground in high wind?

This is totally messed up for me at this point – and maybe the explanation is really simple? Your turn.

That's how it is for airplanes and other aircraft which have wings of perfect enough shape that the airflow stays more or less attached in some range of AoA. At some AoA and higher, the flow abruptly detaches from the upper surface, lift suddenly drops, and things go chaotic - that's what they call "stall" in traditional aerodynamics. Typical stall AoA is 16-20 degrees.

Not what we have with parachutes. We have a type of airflow more resembling that of a brick than a wing: at AoA of 16-20 degrees, nothing bad happens, we can sink our inflatable air carpets at 45, 60, and almost 90 degrees AoA. At these angles, there's little to no lift, it's almost all drag. It's at about 90 degree AoA that things change dramatically: the air has no longer any reason to fow from nose to tail and it switches direction, and that's what we call a stall - a sudden reverse of airflow which makes the carpet surge backwards.

So, both rear riser and brake stalls (in parachutist's meaning, not aerodynamics textbook meaning) happen at close to 90 degree AoA, and the difference between them is due to different strings you pull on the barely inflated air mattress which distorts its shape differently.

That's all there's there.

A stall by definition is a loss of lift which occurs because the airflow over the top portion of the airfoil is distorted due to AoA. A stall can occur in any attitude at any airspeed.

Now, in regard to parachutes, I believe a "Stall" is not a stall in the traditional sense. A stall in parachutes is in relation to pressurization. You can fly a BASE canopy straight down & even backwards & still maintain pressurization. The airflow over the top skin of the canopy is not creating lift in these attitudes. Is the canopy considered "stalled" in these attitudes? I guess technically yes, but I tend to notice most people relate a stall to depressurization & subsequent collapse of the canopy.

My 2 cents.

rear risers attach to every cell. brakes do not.
thus they distort differing numbers of cell. the rear riser stall will more likely affect the whole parachute. braked stalls start at the outboard cells.

they also attach at different locations, so they disort the canopy differently.

the distortion changes both the shape of the parachute and the AoA. both affect the lift generated.

there is a ton of limited use theory. practical knowledge from experience tends to be far more useful.

Fun way to figure this out without relying on the internet....... Go to a local DZ and ask to try CRW (The 7-cell Lightening kind)!!!!! SERIOUSLY!

~TAylor

+1

I don't care in the least about the theoretical aspects of how the stalls differ. The important thing is that they *do* differ and both are fun and both are useful under different scenarios.

Rear riser stalls are far more gentle and controlled--to the point of being a bit boring--but that controllability makes them a very good trick to know. For example, when building CRW big ways, we often have canopies on both sides of us while we are waiting for our slots. That makes it hard, and sometimes downright dangerous to use our usual "sashay" trick to kill altitude. A great alternative in that situation is the rear-riser stall. You can kill altitude while maintaining heading. Coming out of the stall we do a little double-front risers to regain any forward distance we lost during the stall.

For BASE, let's say you are coming in on a narrow landing area with really shitty, tall obstacles on all sides of the landing area and it looks like you are going to overshoot. A rear riser stall can be a great option under those circumstances.

By comparison, a toggle stall is less predictable on most canopies. It is a more sudden and violent stall (making it more fun!), but there is a *very* cool trick you can do called a stall turn. As soon as you enter the stall, if you slightly raise one toggle, that side of your canopy reinflates and starts flying forward, while the other side remains stalled and flying backwards. You are pretty much turning in place.

With practice, you can cleanly do a 180 stall turn on the right canopy. I think most BASE canopies would do well.

The stall turn is a great trick for turning into the wind at low altitudes, but you had better have the skills, equipment, and knowledge to do it.

I had an attitude one day at the DZ, did a 180 stall turn at treetop altitude and nailed the peas. Don't try that unless you are *very* current and know what the hell you're doing, though. I had done hundreds of stall turns on that canopy, including a dozen or so on that same jump so I knew the air was clean.

Anyway, both stalls are good things to be familiar with and should be practiced often.

Just my two cents--YMMV.

Walt

>... " This is totally messed up for me at this point – and maybe the explanation is really simple? Your turn ."
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You are Not messed-up totally by over thinking it like your doing rather than just doing it and learning what the feels & flies like in Both rear-Riser & Break stall . & it does Not take an Aerospace engineering degree to be a tops in accuracy & Canopy flight .

You got no profile filled-out. So I am just 'assuming' you have no BASE jumps & that you are doing some skydives & Canopy work on the DZ ?
It sounds like in your Post you are doing some work with your Canopy & asking questions . The Post Q & A sounds more like it belongs in the Beginners Thread/forum rather than the BASE Tech. forum .

Both these stalls rear-Riser & Toggle you are going to have to be well versed in . With also knowing the recovery of. & how negotiation of Canopy turns in Both stalls also .
Plus the Toggle stall point with incorporating flat-turns also in your Canopy learning .
All this is pretty beginner stuff & not advance Tech. for the BASE jumper .

Not to say that your step by step Q's & by the book technical dissection & Canopy learning can not be done together with hands-on learning of the difference of Canopy stalls . But most canopy pilots never get into the real minut Tech. details, they just fly the Canopy, & learn to do it pretty well with out over thinking it to much .
You just need to get with someone where you live that knows exactly what the answers to what you are asking & how it translates & applies over to you 'Really' doing it under a Canopy . That's much better than learning it on the Internet & people flipping you shit & you hoping for correct answers .
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