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Westerly

Best way to fly through turbulence?

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I hit some nasty turbulence today at around 2k'. My initial reaction was that it's my understanding that higher wing loaded canopies are less effected by turbulence and so if you're getting shacked around hard you want to increase your wingloading. Thus, I spiraled down and tried to keep my airspeed and wing loading high until it was getting close to landing time. By contrast, my understanding has been that flying in brakes is the worst thing you can do as it depressurizes your canopy and increases the risk of a collapse.

So what's the real story in flying in turbulence? Do you want to spiral around and keep the speed up or not? If it matters my WL is 1.06 on a Lotus 170 air locked canopy.

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Last time I was in Florida, we hit the turbulence on hot days at altitudes up to 5.5kft. For me, flying through it with increased airspeed is impossible, since I won't have arms left if I have to frontriser for 5000ft. So I took the paraglider approach, to fly through it with a little brakes to keep a good feel for what my canopy was doing. The turbulence was never so bad though that I feared for a canopy collapse, flying on a Lightning 160 at 1.35 wingloaded. Then again, Lightnings tend to recover quickly from partial or full collapses, so ymmv.

Another disadvantage of spiraling around is that you are more likely to lose sight of the other canopies in the air. An unplanned canopy collision is bad news with or without turbulence.

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Canopy collisions below decision altitude are a significant cause of fatalities in this sport. I'd strongly recommend against spiraling below 2000 feet. Turbulence is generally just an inconvenient bumpy ride, not a danger*. We've all been lightly loaded and bounced around under canopy at some point. Just keep your hands up and fly predictably.

*If it's so bumpy it's dangerous, stay on the ground until conditions are safer. Discuss any questions about this with local instructors.

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Keep your hands up and allow the canopy to fly - your canopy deals with turbulence better when it is in its flight cycle ( where it is flying without inputs) plus you will move quicker though the turbulent area.

Spirals (apart from endangering yourself and other under canopy) cause you to stay in the area of turbulence.

Imagine a lavalamp on the ground and the turbulence are the bubbles - when one hits you - if you spiral you are simply working your way down lots of the "tube" of turbulence....

By allowing your canopy to fully fly you will move way.


I learnt to deal with it by doing a PD canopy course./ Learnt basics on turbulence - why and when it occurs. You can then spot it before you hit it !

:)

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Thus, I spiraled down and tried to keep my airspeed and wing loading high until it was getting close to landing time.



Was this a typo? My understanding is that wing loading is based on mass, not weight, and so manoeuvres such as spiralling increase your suspended weight but not technically your wing loading.

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>Thus, I spiraled down . . .

Probably the worst thing you could do.

1) Spiraling greatly increases your chance of collision.
2) Your canopy is most stable in level flight, or with very slight brakes. A spiral depressurizes one side of the canopy and distorts the tail.
3) If your canopy does collapse, now it has to try to reinflate with you spinning under it going an unexpected direction. Line twist is probably the least bad thing that will happen.

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Turbulence is pretty short lived, so just keep flying as normal is what I do.

I am lightly loaded and hot weather thermals (not what I call turbulence) have both bounded me around and kept my decent rate very low. When jumping at a DZ that you are familiar with, it is not hard to learn where the thermals tend to be. It is also useful to know that if you need to get back from a long spot. I fly with a Flysight and also listen to my vertical speed under canopy. It is interesting to see how the type of ground you are flying over often changes your decent rate. Plus or minus 5 MPH in the vertical is not uncommon. My average vertical is about 12-13 MPH.
Instructor quote, “What's weird is that you're older than my dad!”

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Westerly

Lotus 170 air locked canopy.



In turbulence, when I fly my Lotus or Samurai, I fly with my hands all the way up and trust in the benefits of the airlocks. Closer to the ground I prepare to flare quickly if it gets bumpy on my final approach.

You bought an airlocked canopy - believe in it! You don't want to deliberately jump in sketchy conditions, but use the canopy's advantages when they come into play.
My Dad used to ask me if someone jumped off a bridge would I do that too? No, but if they jumped out of an airplane, that's a different question...

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benlangfeld

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Thus, I spiraled down and tried to keep my airspeed and wing loading high until it was getting close to landing time.



Was this a typo? My understanding is that wing loading is based on mass, not weight, and so manoeuvres such as spiralling increase your suspended weight but not technically your wing loading.



The assumption is correct, spiraling, by increasing the G-Number, will in fact increase the wing loading experienced by the canopy for the duration of the maneuver.

That said, yes, "spiraling down" because of turbulence is probably the worst decision you can take, not only because you increase the chance of a collision (let's assume you cleared your airspace alright) but because by perturbing the canopy and changing its flight modes you actually make it a lot more susceptible to turbulence and possibly collapses.
The best course of action is to let the canopy fly in whatever state you enter the turbulence (ideally, full flight), and personally I like to keep just enough pressure on the toggles that I feel the lines being in tension (think basically removing the slack, but no more): having had a few collapses due to turbulence during high performance approaches, I like to "feel" the canopy when going through turbulence and hopefully I won't affect it too much by doing that, although, I'll add, that's debatable to whether it's the right thing to do or not.
I'm standing on the edge
With a vision in my head
My body screams release me
My dreams they must be fed... You're in flight.

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The assumption is correct, spiraling, by increasing the G-Number, will in fact increase the wing loading experienced by the canopy for the duration of the maneuver.



So do you suggest Wikipedia be corrected? From https://en.wikipedia.org/wiki/Wing_loading

Quote

In aerodynamics, wing loading is the total mass of an aircraft divided by the area of its wing.



I believe I’m still correct in that the wing loading is not changed, being defined as a function of mass. One’s load factor (https://en.wikipedia.org/wiki/Load_factor_(aeronautics)) changes, and the impact on fight characteristics might be the same as an increased wing loading, but going full pedant, the two are not the same.

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You can interpret wing loading both ways.

The wing loading on an airplane or parachute is normally the weight over whatever is chosen as the representative wing area.

If the parachute or airplane is pulling 2g in a turn, then it's wing loading is doubled in that maneuver. Aerodynamically the wing does have to work harder to create that lift, and could stall or break or whatever. The changes in forces on it are real.

But one still can talk about "what's the wing loading" for the vehicle in general, and that means under standard 1g conditions.

(One could do weight or mass, whatever, we're not at the level of accuracy where we care about the buoyancy effect of the air displaced by the volume of the object.)

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dthames

Turbulence is pretty short lived, so just keep flying as normal is what I do.

I am lightly loaded and hot weather thermals (not what I call turbulence) have both bounded me around and kept my decent rate very low. When jumping at a DZ that you are familiar with, it is not hard to learn where the thermals tend to be. It is also useful to know that if you need to get back from a long spot. I fly with a Flysight and also listen to my vertical speed under canopy. It is interesting to see how the type of ground you are flying over often changes your decent rate. Plus or minus 5 MPH in the vertical is not uncommon. My average vertical is about 12-13 MPH.



In hot weather, it pays to think ahead about where the turbulence will be relative to the landing area. That type of turbulence is easy to predict, as surfaces like tarmac or gravel heats up more in the sun, and the air boils off those surfaces faster than off the (relatively) cool grass, causing turbulence.

So in general for landing area, you want something smooth all around. With that I mean that it is way better to land in the middle of a large grassy field, rather than at the edges where the boiling air is likely more violent and can throw you around much more (not good when your altitude is measured in single digits...).

Also, avoid the peas for the exact same reason.

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benlangfeld

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The assumption is correct, spiraling, by increasing the G-Number, will in fact increase the wing loading experienced by the canopy for the duration of the maneuver.



So do you suggest Wikipedia be corrected? From https://en.wikipedia.org/wiki/Wing_loading

***In aerodynamics, wing loading is the total mass of an aircraft divided by the area of its wing.




I believe I’m still correct in that the wing loading is not changed, being defined as a function of mass. One’s load factor (https://en.wikipedia.org/wiki/Load_factor_(aeronautics)) changes, and the impact on fight characteristics might be the same as an increased wing loading, but going full pedant, the two are not the same.

Just a thought.. load or force can not be interpreted as a mass. For force or load we need to multiply mass with acceleration. And acceleration will be bigger or smaller - depending on maneuver preformed with canopy. So in theory wing loading is changing all the time.

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That's exactly my point. Wing loading as strictly defined (at least the definition I see, which apparently is not the common usage) doesn't change, because it's defined as a function of mass. A manoeuvre introduces a component of acceleration, which does not alter mass, but does alter weight. It therefore does not alter wing loading per the strict definition.

If your argument is that the definition on wikipedia is wrong, then I'll propose a fix to it and correct my understanding. Indeed John LeBlanc states the definition as a function of weight. Which is correct?

If it's that the existing definition is indeed correct for aerodynamics in general but not useful to parachuting, then that's cool, but maybe we should have a distinct term with a different definition to avoid confusion.

It may seem pedantic, but bad things happen when we think we're talking about the same thing but we're actually not: https://en.wikipedia.org/wiki/Mars_Climate_Orbiter#Cause_of_failure.

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benlangfeld

That's exactly my point. Wing loading as strictly defined (at least the definition I see, which apparently is not the common usage) doesn't change, because it's defined as a function of mass. A manoeuvre introduces a component of acceleration, which does not alter mass, but does alter weight. It therefore does not alter wing loading per the strict definition.

If your argument is that the definition on wikipedia is wrong, then I'll propose a fix to it and correct my understanding. Indeed John LeBlanc states the definition as a function of weight. Which is correct?

If it's that the existing definition is indeed correct for aerodynamics in general but not useful to parachuting, then that's cool, but maybe we should have a distinct term with a different definition to avoid confusion.

It may seem pedantic, but bad things happen when we think we're talking about the same thing but we're actually not: https://en.wikipedia.org/wiki/Mars_Climate_Orbiter#Cause_of_failure.



Can we take this pedantic exchange elsewhere .....this is a thread on the best way to fly through turbulence not 'whose going to be the first to rewrite wiki'

Thanks.

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benlangfeld

That's exactly my point. Wing loading as strictly defined (at least the definition I see, which apparently is not the common usage) doesn't change, because it's defined as a function of mass. A manoeuvre introduces a component of acceleration, which does not alter mass, but does alter weight. It therefore does not alter wing loading per the strict definition.

If your argument is that the definition on wikipedia is wrong, then I'll propose a fix to it and correct my understanding. Indeed John LeBlanc states the definition as a function of weight. Which is correct?

If it's that the existing definition is indeed correct for aerodynamics in general but not useful to parachuting, then that's cool, but maybe we should have a distinct term with a different definition to avoid confusion.

It may seem pedantic, but bad things happen when we think we're talking about the same thing but we're actually not: https://en.wikipedia.org/wiki/Mars_Climate_Orbiter#Cause_of_failure.



Hay,
all I am saying is that you can´t just equalize mass with load and that if Wing loading is defined as wikipedia is saying, naming of it - "Wing loading" is not really most accurate.

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I can understand why you want to know what 'the true definition is'. While I haven't been working in aerospace for a while, I'm not sure there is one strict definition.

If you are engineering a satellite, maybe you'll be very particular about MASSES and their inertial effects.

If you are certifying a light aircraft and doing flight tests, you'll put the aircraft on sensitive electronic scales to get an accurate WEIGHT. But you don't need the kind of detail where you need to account for the buoyancy of the steel & aluminum, nor account for the slight changes in gravity at different points on the oblate spheroidally shaped earth.

Sometimes one needs to think through multiple levels of accuracy, at other times there are real life approximations to reality that are sufficient.

For other things one can also have a standardized reference value, vs. a temporary current value. A plane may have a stall speed listed officially as 49 kts.... but that's for maximum allowed gross weight, flaps up, slow deceleration at 1g. The actual stall speed while maneuvering will depend on its weight, G's being pulled, level of ice contamination on the wing, etc.

So, don't worrry too much about the differences for plain old skydiving.

Anyway, back to turbulence.

Brian Germain did mention the idea of putting on a little G to increase the wing loading, and that's fair enough.

You'll have a little more speed so the change in angle of attack for a given gust will be less, canopy pressurization will be higher with less distortion, and you'll have a higher angle of attack (which is OK given that collapses tend to be from the front of the canopy having too low an angle of attack, rather than too high an angle). That's all a benefit in turbulence.

(Unless you actually do have a collapse, in which case you'd rather be under a slow, low wing loading student or accuracy canopy!)

But at the same time, one has to be practical, and not overdo the "adding G load" concept, spiralling down through the pattern....

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benlangfeld

Indeed. Maybe a moderator could split the thread? Apologies for going off-topic!

For what it's worth, I'm convinced, and have edited the wikipedia definition: https://en.wikipedia.org/w/index.php?title=Wing_loading&oldid=836065606



I am pretty sure that this is wrong.

If you want to define wingloading as "weight devided by surface area", the resulting unit has to be something like N/m^2 (or the equivalent imperial units like lbf/ft^2 ??)

You cannot redefine the formula without redefining the units.

You broke wikipedia ;-)

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evh

***Indeed. Maybe a moderator could split the thread? Apologies for going off-topic!

For what it's worth, I'm convinced, and have edited the wikipedia definition: https://en.wikipedia.org/w/index.php?title=Wing_loading&oldid=836065606



I am pretty sure that this is wrong.

If you want to define wingloading as "weight devided by surface area", the resulting unit has to be something like N/m^2 (or the equivalent imperial units like lbf/ft^2 ??)

You cannot redefine the formula without redefining the units.

You broke wikipedia ;-)

Pounds are a measure of weight (the US/Imperial measure of mass being slugs - seriously). We talk about wing loading in units of lbs/ft^2. That's consistent with the edit. N/m^2 would be consistent with the apparently erroneous original definition involving mass.

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Haha! The way this topic turns out, it seems like it's been flipped over by turbulence!

Me being the physicist that I am, I'll happily join the discussion. From an aerodynamic point of view, what really matters is the force per unit area on your wing (or strut, or control surface, or line, or whatever). Mass (in kg) is irrelevant insofar that you need a (non-fixed in both direction and magnitude) vector called acceleration to get the force from the mass (Newton's famous F = m*a). As mentioned, the mass of the system stays the same no matter how hard you whip around on front risers, but the force that your lines have to hold sure does change!

So the technically correct (the best kind of correct) definition of wingloading would indeed be one of N/m^2 (because imperial schimperial), rather than kg/m^2. Which would be weight per unit area. And since weight is changed by a change in acceleration, wingloading does change when you give some sort of input under canopy.

But in most cases we can simplify things by saying the acceleration is constant and equal to the local earth gravity. In that case, definitions of wingloading in kg/m^2 are equivalent to those in N/m^2, so under that simplification this entire discussion is completely pointless.:):)

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