Anatomy of a "spinner".

[bob.dino 0]

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Stilettos are a good canopy for this type of testing.[Wink]

I have my shiney new Samurai loaded at 1.2 to play with. It's plenty for now; I've no desire to scare myself witless under something smaller just yet
Thanks for all the info.

[davelepka 4]

Just wanted to say thanks to Hooknswoop for making my points for me while I was away from the computer. I agree with what he has said.

If the brakes are properly stowed, they should have no effect on the roll axis if they are left stowed, or unstowed in a symetrical fashion.

Any turn can be nuetralized with a counter-input provided that the canopy is not suffering from a malfunction of any kind.

Rear riser input generally will provide the most immediate response, and having the brakes stowed will only increase the response.

[johnny1488 1]

I will hopefully in a few days post some video that everyone here should find very interesting.

Johnny
--"This ain't no book club, we're all gonna die!"
Mike Rome

[davelepka 4]

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will hopefully in a few days post some video that everyone here should find very interesting.

It's going to be hard to tell what is happening from a video.

I'd be much more interested in an explanation of how making your canopy fly faster, with no input toward the roll axis, will stop a rotation.

[Dolph 0]

Thanks everyone! You've been more than helpful. It's nice to see different thngs being debated and learning some new stuff.

It's been very enlightening, so thanks again.

[johnny1488 1]

I think you can tell lots from video.

You can see the rotation of the horizon (turning)

You can see the inputs being given harness from the levels of the 3 rings.

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I'd be much more interested in an explanation of how making your canopy fly faster, with no input toward the roll axis, will stop a rotation.

It's not why being in full flight stops the turn that is in dispute. A canopy in trim will fly in straight and level flight with no inputs. It's why a canopy in brakes will have tremendous oversteer to the point of continuing a turn which has been neutralized.( not necessarily counteracted)

Like I said, I cant tell you why it does, but try it on your next jump and tell me what it feels like to you.

Johnny
--"This ain't no book club, we're all gonna die!"
Mike Rome

[Hooknswoop 19]

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I think you can tell lots from video.

You can't see how much weight is on each riser set though. Again, the risers can be exactly even, but still have more weight one one side than the other, which is magnified in a spin.

Derek

[johnny1488 1]

Isnt the weight on the riser related to the level of the three rings?

If the 3 rings are even is there any influence on the canopy shape?

The way I understood it (or thought I did) was putting weight on one or the other legstrap made the harness (and in turn the front and rear riser on one side) lower than the other. Am I mistaken?

Johnny
--"This ain't no book club, we're all gonna die!"
Mike Rome

[bob.dino 0]

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I think you can tell lots from video.

You can't see how much weight is on each riser set though. Again, the risers can be exactly even, but still have more weight one one side than the other, which is magnified in a spin.

If the risers are even but there's a different load on the two riser sets, the parachute must be exerting a differing force on each riser set.

Assume the parachute is turning left. This implies that you're exerting a greater force on the left riser set. If the risers are level with respect to the parachute, then the left side of the parachute is exerting a greater upward force - lift - than the right side. If the lhs of the parachute is producing more lift than the rhs, the parachute will recover to level flight.

This implies that harness turns don't work.

What am I missing?

[Hooknswoop 19]

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Isnt the weight on the riser related to the level of the three rings?

Not necessarily. You can have more weight on one side of the harness with the 3-rings even.

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The way I understood it (or thought I did) was putting weight on one or the other legstrap made the harness (and in turn the front and rear riser on one side) lower than the other. Am I mistaken?

That is correct also.

You can get slack in the lines with the 3-rings being even. You can also load up one side more than the other with the 3-rings even.

Derek

[johnny1488 1]

how (in real word scenarios) can you have more weight on one than the other and still have them be level.

Am I correct in assuming that making the 3 rings uneven would provide a greater change in heading than weight difference with them equal?

I can imagine a weight difference in theory but cant put it into real world practice.

Johnny
--"This ain't no book club, we're all gonna die!"
Mike Rome

[Hooknswoop 19]

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how (in real word scenarios) can you have more weight on one than the other and still have them be level.

They are connected to the same harness, so you can have more weight on one side than the other with them even.

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Am I correct in assuming that making the 3 rings uneven would provide a greater change in heading than weight difference with them equal?

With the canopy in a 2 "G" producing spin, your WL is doubled, so it doesn't take a lot to keep the canopy in a spin. From normal, steady state flight, it takes a lot more harness input to get the canopy to start the turn.

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I can imagine a weight difference in theory but cant put it into real world practice.

Don't worry, I've confused myself 3 times in this thread alone

Derek

[davelepka 4]

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It's not why being in full flight stops the turn that is in dispute. A canopy in trim will fly in straight and level flight with no inputs. It's why a canopy in brakes will have tremendous oversteer to the point of continuing a turn which has been neutralized.

Well, at first it was about how releasing the brakes would stop a turn. That was suggested, and I commented that it should have no effect on the turn.

As far as the other thing, my first impression would be that oversteer would be reduced with the brakes stowed, and I'll explain it this way:

With the brakes stowed, you have increased drag, and the reduction of steady state airspeed that goes with it. Now grab a riser, and toss yourself into a turn. Your swinging under the wing will cause the canopy to turn/dive and pick up speed, however the amount of speed you will pick up will be limited by the drag of the stowed brakes. Your acceleration time will be reduced, as will all factors present with an increase in speed, oversteer being one of them.

The point being is that with the brakes stowed, the flight envelope is reduced in its scope. The less speed you can pick up in a turn, the less the canopy will want to continue the turn, the less time you spend out from under the wing, etc. It all adds up to LESS oversteer, not more.

As such, with the brakes unstowed, if you enter the same turn as before, the canopy will have a longer period of acceleration (before drag overcomes it), giving the pilot more time in the turn, and more time out from under the wing. At this point, it's basic physics: an object in motion will tend to stay in motion.

My assertion is that the magnitude of that motion will dictate the degree to which it remains in motion. Push a toy car with 1 measure of force, it will roll 'x' feet. Push the same car with 2 measures of force, and it will roll a distance greater then 'x'.

Turn a canopy to achieve airspeed 'a', and it will continue in the turn for a period of time 'y'. Turn the canopy to achieve an airspeed greater than 'a', and turn will continue for a period longer than 'y'.

Does this sound right? Anyone?

[johnny1488 1]

It sounds like it could work, sure. But let me know what happens when you try it on your next jump.

Johnny
--"This ain't no book club, we're all gonna die!"
Mike Rome

[davelepka 4]

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try it on your next jump

I wish. Last night I broke my rig down for it's winter cleaning/service, and I just walked in from being hit by the first snowflakes of the season.

If you can wait unitl mid-January, I'll get back to you then.

[johnny1488 1]

Well I'll do it again this weekend and see if I can prove myself wrong.

Johnny
--"This ain't no book club, we're all gonna die!"
Mike Rome

[johnny1488 1]

Well I spoke with someone from PD's R+D department today. He said he has heard and felt the phenomenon that I was refering to, though he said PD has never done any full testing on canopy flight characteristics with the brakes stowed.

He said it is most likely due to the reduced airspeed and the increased turn rate of an elliptical canopy that will keep it in a turn when all available inputs have been returned to neutral.

He also said popping the brakes increases the air speed and allows the canopy to return to its normal flight range and recover from any previous turns that may or may not still be affecting the canopy.

But I still want to go up this weekend and do some tests with the brakes set.

Johnny
--"This ain't no book club, we're all gonna die!"
Mike Rome

[Hooknswoop 19]

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Well I spoke with someone from PD's R+D department today. He said he has heard and felt the phenomenon that I was refering to, though he said PD has never done any full testing on canopy flight characteristics with the brakes stowed.

He said it is most likely due to the reduced airspeed and the increased turn rate of an elliptical canopy that will keep it in a turn when all available inputs have been returned to neutral.

He also said popping the brakes increases the air speed and allows the canopy to return to its normal flight range and recover from any previous turns that may or may not still be affecting the canopy.

But I still want to go up this weekend and do some tests with the brakes set.

Then I stand corrected.

Derek

[johnny1488 1]

What are you saying, that PD's R+D department knows more than I do?!

I don't think I would have ever come to that conclusion if I had not had it happen to me a couple of times.

Johnny
--"This ain't no book club, we're all gonna die!"
Mike Rome

[Hooknswoop 19]

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What are you saying, that PD's R+D department knows more than I do?!

I don't think I would have ever come to that conclusion if I had not had it happen to me a couple of times.

LOL. I would really like to understand why though. It goes against what I know about canopies.

Derek

[scdrnr 0]

I have experienced this phenomenon as well, and while I generally agree with Hooknswoops theory that a canopy with symetrical control inputs will fly straight and level, I think something else is going on here.

I know for a fact that it is possible to make an airplane remain in a spin with the controls neutralized. Stick forward breaks this condition.

Essentially, I suspect that what happens is that the spin is initiated by line-twists, uneven harness, etc., but under a high performance canopy the rotational speed develops to a point where inertia overcomes the canopies now neutralized control imputs. Going to full flight allows the canopy to increase its aerodynamic authority.

[davelepka 4]

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the rotational speed develops to a point where inertia overcomes the canopies now neutralized control imputs. Going to full flight allows the canopy to increase its aerodynamic authority.

What does full flight have to do with the rotational speed? I can see how a canopy could achieve equalibrium in a turn, and remain in the turn until a countering input is applied. I cannot understand how a symetrical release of the brakes will stop the turn.

It is possible that eventually the turn may stop, as releasing the brakes will change the balance of the system, maybe to a state where the turn cannot 'power' istelf but I cannot see this as being anything close to immediate, and not a solution to a 'problem' situation.

If you were in an AC in a spin, with flaps deployed, would your course of action include retracing them? I would apply rudder against the spin, to bring the stalled wing forward, and level the AC. The flaps would not enter the equation.

Substitute the words 'brakes' for flaps, and 'toggle' or 'rear riser' for rudder, and you have the canopy version of the solution.

[scdrnr 0]

I think in this situation I would call the toggles your "elevator" - they are being used for pitch/airspeed control.

We need to throw away the concept of "a canopy cannot turn without an aerodynamic control imput". Now that may be true most of the time, but in some instances inertia can be more powerful than aerodynamics. With the brakes stowed you have a limited range of aerodynamic control. Releasing brakes increases your airspeed giving you more aerodynamic control. Can you stop a high speed turn with risers brakes stowed? Eventually, yes, because no matter how much inertia there is, an turn sustained by inertia will eventually correct itself, unless you are in a vacuum, and any counter-turn control imput will only help it.. The question is can you stop it before you reach your hard deck, or the ground?

Take a cessna 172 in straight and level flight, now give sudden full aieleron deflection to one side, then neutralize the controls. The airplane quickly comes back to straight and level.

Now take an Extra 300 and do the same thing. It will keep rolling. Eventually, it will stop but the only way to stop it quickly is with full opposite stick. Even 1/2 opposite stick won't stop it promptly.

The higher performance the canopy, the more inertia you can create. Normally, opposite control imput will stop that. But lets say during deployement you have a severe tension knot or line over that creates a larger control imput than brakes stowed risers can counter. Even if it clears itself you may have more inertia than risers can control in any useful amount of time/altituded.

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If you were in an AC in a spin, with flaps deployed, would your course of action include retracing them? I would apply rudder against the spin, to bring the stalled wing forward, and level the AC. The flaps would not enter the equation.

I have used flaps by themselves to recover an aircraft from a spin. I have also used just elevator, just rudder, and just power changes to recover from spins (not all in the same plane). It depends on the plane. Universal stall recovery is power off, aielerons neutral, stick forward, opposite rudder, almost simultaneously. Most planes will recover if you simply return to neutral, or even let go of the controls all together.

I once spun a Cessna 310 with full fuel in the tip tanks, 300 lbs a side. The inertia was so great after a 3/4 turn that full stall/spin recovery imputs did not stop the rotation until I had alot more airspeed than normal. I went way past redline on the recovery (lesson learned).

The point is you can easily create a situation where inertia will, at least temporarily, overcome aerodynamics. And, in general, more airspeed means more aerodynamic control. So if you are spinning and risers aren't having the desired effect, I can see how going to full flight may help.

[scdrnr 0]

Just to simplify my long winded answer:

During deployment you may enter a turn more severe than you could induce with risers brakes stowed.

Even if the condition that caused it clears, leaving you with neutral controls, there may be more inertia than you can control with risers in any useful amount of time/altitude.

Increasing airspeed by releasing toggles will give your wing more aerodynamic control to counter the inertia.

[vdavid2 0]

If it is spinning with the brakes set, it will spin with the brakes released, all other things being equal. Think about it. Something is causing the canopy to turn, an unequal input, otherwise it would fly straight. The only way releasing the brakes will stop a spin is if one brake line is shorter than the other between the brake setting and the tail.