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Re: [The111] Fatality - Tampa Bay, FL - 20 Jan 2010

 

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in2jumping  (C License)

Jan 20, 2010, 3:40 PM
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Re: [The111] Fatality - Tampa Bay, FL - 20 Jan 2010 Can't Post

In reply to:
In reply to:
Even if decedent turned at appropriate altitude in low winds, you need to turn higher in high winds because as soon as you turn back to the wind line, the nose of your canopy is down so the wind hits the top of the canopy and drives it downward even faster.

I have not seen this myth repeated in a while and thought perhaps it had been dispelled.

The airspeed of your canopy does not change, no matter what the ground winds are doing. The wind doesn't "hit the top of your canopy" because your canopy is not attached to the ground. It's attached to you, and the whole system (you + canopy) are moving with the air, relative to the ground.

Imagine a normal, no wind day, and you are coming it to land. At 500 ft the ground turns into a massive conveyor belt moving at 20mph. Everybody standing on the ground is now moving in the direction of the conveyor belt and feeling 20mph wind in their face. None of that will have any effect on how fast your canopy flies, but it will affect how fast you have to run when you land. Same with high (steady) winds. The ground and air can be moving relative to each other at any speed possible... but your canopy still moves through the air exactly the same.

So why does your ground speed increase when you turn downwind?

Could it be that the canopy is being pushed from the behind from a faster flowing air flow then your normal canopy airspeed? Could this not possibly push the azz end of your canopy putting it more in of a downward angle?

You are making it sound like high winds have no affect what so ever on your canopy.


humanflite  (D 99999)

Jan 20, 2010, 3:45 PM
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Re: [in2jumping] Fatality - Tampa Bay, FL - 20 Jan 2010 [In reply to] Can't Post

This is getting confusing. and is not really on topic of this incident.... maybe better discussed in the general forum...

But as far as I understand it, your ground speed increases when going downwind in higher winds, because relative to the ground, you have increased your rate of speed across it.

however your air speed, has not increased, you are still flying at the same speed thorought the airflow.
I think Wink

In reply to:
In reply to:
In reply to:
Even if decedent turned at appropriate altitude in low winds, you need to turn higher in high winds because as soon as you turn back to the wind line, the nose of your canopy is down so the wind hits the top of the canopy and drives it downward even faster.

I have not seen this myth repeated in a while and thought perhaps it had been dispelled.

The airspeed of your canopy does not change, no matter what the ground winds are doing. The wind doesn't "hit the top of your canopy" because your canopy is not attached to the ground. It's attached to you, and the whole system (you + canopy) are moving with the air, relative to the ground.

Imagine a normal, no wind day, and you are coming it to land. At 500 ft the ground turns into a massive conveyor belt moving at 20mph. Everybody standing on the ground is now moving in the direction of the conveyor belt and feeling 20mph wind in their face. None of that will have any effect on how fast your canopy flies, but it will affect how fast you have to run when you land. Same with high (steady) winds. The ground and air can be moving relative to each other at any speed possible... but your canopy still moves through the air exactly the same.

So why does your ground speed increase when you turn downwind?

Could it be that the canopy is being pushed from the behind from a faster flowing air flow then your normal canopy airspeed? Could this not possibly push the azz end of your canopy putting it more in of a downward angle?

You are making it sound like high winds have no affect what so ever on your canopy.


The111  (D 29246)

Jan 20, 2010, 3:47 PM
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Re: [in2jumping] Fatality - Tampa Bay, FL - 20 Jan 2010 [In reply to] Can't Post

In reply to:
So why does your ground speed increase when you turn downwind?

Your ground speed doesn't increase when you "turn downwind"... it increases when you fly downwind, period. Winds have everything to do with your groundspeed and nothing to do with your airspeed. They also don't affect your descent rate during a turn unless they are blowing vertically up or down.


Premier billvon  (D 16479)
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Jan 20, 2010, 3:50 PM
Post #4 of 134 (2933 views)
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Re: [in2jumping] Fatality - Tampa Bay, FL - 20 Jan 2010 [In reply to] Can't Post

>So why does your ground speed increase when you turn downwind?

Because your groundspeed is airspeed + speed of the airmass you are in.

>Could it be that the canopy is being pushed from the behind from a
>faster flowing air flow then your normal canopy airspeed?

No. It is still being pushed on from the front by drag, being pulled up by lift, and being pulled down by gravity, as always.

>You are making it sound like high winds have no affect what so ever on
>your canopy.

They don't. You could be in a 600mph jet stream and your canopy wouldn't know the difference - PROVIDED that the air you were flying in is always moving at the same speed. When it changes rapidly, we call that turbulence.


chuckakers  (D 10855)

Jan 20, 2010, 4:03 PM
Post #5 of 134 (2914 views)
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Re: [in2jumping] Fatality - Tampa Bay, FL - 20 Jan 2010 [In reply to] Can't Post

In reply to:
In reply to:
In reply to:
Even if decedent turned at appropriate altitude in low winds, you need to turn higher in high winds because as soon as you turn back to the wind line, the nose of your canopy is down so the wind hits the top of the canopy and drives it downward even faster.

I have not seen this myth repeated in a while and thought perhaps it had been dispelled.

The airspeed of your canopy does not change, no matter what the ground winds are doing. The wind doesn't "hit the top of your canopy" because your canopy is not attached to the ground. It's attached to you, and the whole system (you + canopy) are moving with the air, relative to the ground.

Imagine a normal, no wind day, and you are coming it to land. At 500 ft the ground turns into a massive conveyor belt moving at 20mph. Everybody standing on the ground is now moving in the direction of the conveyor belt and feeling 20mph wind in their face. None of that will have any effect on how fast your canopy flies, but it will affect how fast you have to run when you land. Same with high (steady) winds. The ground and air can be moving relative to each other at any speed possible... but your canopy still moves through the air exactly the same.

So why does your ground speed increase when you turn downwind?

Could it be that the canopy is being pushed from the behind from a faster flowing air flow then your normal canopy airspeed? Could this not possibly push the azz end of your canopy putting it more in of a downward angle?

You are making it sound like high winds have no affect what so ever on your canopy.

Smooth, straight-line winds don't have an effect on your canopy's flight "through the air", although they do have an affect on your canopy control.Wink

A canopy is an object moving through a mass of air. Whether that air mass is moving or not is of no consequence to the canopy. If you fly past a cloud (also drifting in the same wind you are flying through), you will notice that your speed relative to it is the same whether you go "upwind" or "downwind" relative to the ground.

The only time a wing is affected by wind is when there is a change in windspeed or direction. Once that change stops, so does any affect.


(This post was edited by chuckakers on Jan 20, 2010, 4:06 PM)


in2jumping  (C License)

Jan 20, 2010, 4:05 PM
Post #6 of 134 (2907 views)
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Re: [The111] Fatality - Tampa Bay, FL - 20 Jan 2010 [In reply to] Can't Post

In reply to:
Your ground speed doesn't increase when you "turn downwind"... it increases when you fly downwind, period.

Which is what I meant to say.

In reply to:
Winds have everything to do with your groundspeed and nothing to do with your airspeed. They also don't affect your descent rate during a turn unless they are blowing vertically up or down.

So lets say you are jumping in 30mph winds and your canopy has a 20mph forward airspeed. What happens when when you complete your turn downwind? Will your canopy still have 20mph airspeed or will it now have 30mph airspeed? What affect will the 10mph airspeed difference between the tail wind airspeed and your canopies airspeed have?


Premier billvon  (D 16479)
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Jan 20, 2010, 4:09 PM
Post #7 of 134 (2898 views)
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Re: [in2jumping] Fatality - Tampa Bay, FL - 20 Jan 2010 [In reply to] Can't Post

>So lets say you are jumping in 30mph winds and your canopy has a
>20mph forward airspeed.

Your airspeed will be 20; your groundspeed will be -10 while flying into the wind.

>What happens when when you complete your turn downwind?

You'll speed up momentarily (as you always do when you turn a canopy) then stabilize at 20mph airspeed again. At that point your airspeed will be 20mph and your groundspeed will be 50mph, and your canopy will handle the same as it did before.


chuckakers  (D 10855)

Jan 20, 2010, 4:13 PM
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Re: [in2jumping] Fatality - Tampa Bay, FL - 20 Jan 2010 [In reply to] Can't Post

In reply to:
In reply to:
Your ground speed doesn't increase when you "turn downwind"... it increases when you fly downwind, period.

Which is what I meant to say.

In reply to:
Winds have everything to do with your groundspeed and nothing to do with your airspeed. They also don't affect your descent rate during a turn unless they are blowing vertically up or down.

So lets say you are jumping in 30mph winds and your canopy has a 20mph forward airspeed. What happens when when you complete your turn downwind? Will your canopy still have 20mph airspeed or will it now have 30mph airspeed? What affect will the 10mph airspeed difference between the tail wind airspeed and your canopies airspeed have?

You will still have a 20mph airspeed after turning downwind, because the canopy is still moving at 20mph through the air. Notice the sound of the wind doesn't change just because you chagre direction? You will, however, now have a 50mph ground speed becuase you are traveling 20mph through and in the same direction as a mass of air moving at 30mph.

What I and others are trying to get across is that there is indeed an affect on your positioning relative to the grond in winds, but your flight relative to the mass of air remains constant in all directions so long as the speed and direction of the air mass doesn't change.


SwampGod  (D 27345)

Jan 20, 2010, 4:37 PM
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Re: [billvon] Fatality - Tampa Bay, FL - 20 Jan 2010 [In reply to] Can't Post

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>You are making it sound like high winds have no affect what so ever on your canopy.

They don't. You could be in a 600mph jet stream and your canopy wouldn't know the difference - PROVIDED that the air you were flying in is always moving at the same speed. When it changes rapidly, we call that turbulence.

Is there a reason we don't consider momentum in these conversations? A 200 pound human traveling at 600 mph would have considerable momentum.

I'm thinking specifically of how an individual would swing out from under the canopy when starting a sharp turn from a 0 mph ground speed versus a 45 mph ground speed.

My brain is struggling with visualizing, let alone calculating whether or not there would be a difference, not to mention a noticeable one. When the winds are that high where I jump, turbulence would crush any other more subtle factors.

-eli


Premier billvon  (D 16479)
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Jan 20, 2010, 4:45 PM
Post #10 of 134 (2849 views)
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Re: [SwampGod] Fatality - Tampa Bay, FL - 20 Jan 2010 [In reply to] Can't Post

>Is there a reason we don't consider momentum in these conversations? A
>200 pound human traveling at 600 mph would have considerable
>momentum.

You do have considerable momentum - but again, it just doesn't matter.

Let's say you land to the east on a no-wind day in Florida. You are traveling at around 810mph with respect to the earth, since Florida is spinning eastward (with the earth's surface) at about 800mph. Is it very hard to stop since you have so much momentum?

Now compare that to landing to the west; you are now going backwards at about 790mph. Do you stop instantly since you have negative momentum? Or shoot backwards due to that negative momentum?

In both cases, no. You're slowing yourself down from (say) 810mph to 800mph in one case, and speeding up from 790mph to 800mph in the other. And in both cases it feels the same to you, because everything near you is going the same speed.


(This post was edited by billvon on Jan 20, 2010, 4:47 PM)


in2jumping  (C License)

Jan 20, 2010, 4:45 PM
Post #11 of 134 (2850 views)
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Re: [chuckakers] Fatality - Tampa Bay, FL - 20 Jan 2010 [In reply to] Can't Post

In reply to:
In reply to:
In reply to:
Your ground speed doesn't increase when you "turn downwind"... it increases when you fly downwind, period.

Which is what I meant to say.

In reply to:
Winds have everything to do with your groundspeed and nothing to do with your airspeed. They also don't affect your descent rate during a turn unless they are blowing vertically up or down.

So lets say you are jumping in 30mph winds and your canopy has a 20mph forward airspeed. What happens when when you complete your turn downwind? Will your canopy still have 20mph airspeed or will it now have 30mph airspeed? What affect will the 10mph airspeed difference between the tail wind airspeed and your canopies airspeed have?

You will still have a 20mph airspeed after turning downwind, because the canopy is still moving at 20mph through the air. Notice the sound of the wind doesn't change just because you chagre direction? You will, however, now have a 50mph ground speed becuase you are traveling 20mph through and in the same direction as a mass of air moving at 30mph.

What I and others are trying to get across is that there is indeed an affect on your positioning relative to the grond in winds, but your flight relative to the mass of air remains constant in all directions so long as the speed and direction of the air mass doesn't change.

Understand now.

I was thinking more of the initial turn downwind at a low alt having an affect of pushing on the back of the canopy diving it forward momentarily. But thinking about more it would not have that much more of an affect then a normal turn.


The111  (D 29246)

Jan 20, 2010, 4:47 PM
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Re: [SwampGod] Fatality - Tampa Bay, FL - 20 Jan 2010 [In reply to] Can't Post

In reply to:
In reply to:
>You are making it sound like high winds have no affect what so ever on your canopy.

They don't. You could be in a 600mph jet stream and your canopy wouldn't know the difference - PROVIDED that the air you were flying in is always moving at the same speed. When it changes rapidly, we call that turbulence.

Is there a reason we don't consider momentum in these conversations? A 200 pound human traveling at 600 mph would have considerable momentum.

I'm thinking specifically of how an individual would swing out from under the canopy when starting a sharp turn from a 0 mph ground speed versus a 45 mph ground speed.

My brain is struggling with visualizing, let alone calculating whether or not there would be a difference, not to mention a noticeable one. When the winds are that high where I jump, turbulence would crush any other more subtle factors.

-eli

It's all about reference frames, Eli. The whole universe is in motion, has momentum and velocity. Our galaxy and our planet both have motion. To consider any physics problem, you have to pick a reference point and say that it's not moving (which is a lie, since everything is moving, always).

If your reference point is the body of air you are in, your momentum is unchanged whether you are flying your canopy through still air or fast air. The only thing different about fast air is that the ground is moving rapidly underneath it. That's what the air thinks at least.... the ground thinks the air is moving rapidly right above it.

In the end, the physics of you flying your parachute, diving, turning, flaring, does not change in your "body of air" reference frame. It only changes to somebody standing on the ground, on Earth. Or on Mars, or anywhere else in the universe.


robinheid  (D 5533)

Jan 20, 2010, 5:18 PM
Post #13 of 134 (2806 views)
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Re: [The111] Fatality - Tampa Bay, FL - 20 Jan 2010 [In reply to] Can't Post

In reply to:
In reply to:
In reply to:
>You are making it sound like high winds have no affect what so ever on your canopy.

They don't. You could be in a 600mph jet stream and your canopy wouldn't know the difference - PROVIDED that the air you were flying in is always moving at the same speed. When it changes rapidly, we call that turbulence.

Is there a reason we don't consider momentum in these conversations? A 200 pound human traveling at 600 mph would have considerable momentum.

I'm thinking specifically of how an individual would swing out from under the canopy when starting a sharp turn from a 0 mph ground speed versus a 45 mph ground speed.

My brain is struggling with visualizing, let alone calculating whether or not there would be a difference, not to mention a noticeable one. When the winds are that high where I jump, turbulence would crush any other more subtle factors.

-eli

It's all about reference frames, Eli. The whole universe is in motion, has momentum and velocity. Our galaxy and our planet both have motion. To consider any physics problem, you have to pick a reference point and say that it's not moving (which is a lie, since everything is moving, always).

If your reference point is the body of air you are in, your momentum is unchanged whether you are flying your canopy through still air or fast air. The only thing different about fast air is that the ground is moving rapidly underneath it. That's what the air thinks at least.... the ground thinks the air is moving rapidly right above it.

In the end, the physics of you flying your parachute, diving, turning, flaring, does not change in your "body of air" reference frame. It only changes to somebody standing on the ground, on Earth. Or on Mars, or anywhere else in the universe.

sure is interesting how much so much quality commentary was generated by my not-so-quality D'OH! Moment comment. Good stuff everybody! Glad I could help...

Wink


happythoughts  (D License)

Jan 20, 2010, 5:23 PM
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Re: [The111] Fatality - Tampa Bay, FL - 20 Jan 2010 [In reply to] Can't Post

Quote:
If your reference point is the body of air you are in, your momentum is unchanged whether you are flying your canopy through still air or fast air.

If a canopy has line tension that is consistent, I think that
is true.

On a high wind day, I have seen people do turns that
changed their line tension. The canopy collapses a little.

Example - running downwind. Quick 90 to the left.
A little right toggle to continue crosswind. The lines on
the left will get a little slack momentarily.
Wind coming from the left, and left lines a little slack.
What would be the effect?

Another - On a 15mph day, do a 180. Stall it a little.
Lines go slack. Does it collapse in the middle for a moment?

A canopy is not uniformly solid always.
You can create turbulence by canopy control.


vanair  (D 8360)

Jan 20, 2010, 5:29 PM
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Re: [SwampGod] Fatality - Tampa Bay, FL - 20 Jan 2010 [In reply to] Can't Post

yes and no, in aviation they call it moving the fish bowl. the fish in the water doesn't change. so turning up wind, down wind doesn't change the plane or canopy in relation to the air mass it's in. hence moving the fish bowl doesn't change what the fish is doing in the bowl. however it does change your movement across the ground. and if it is gusting it's going to effect performance because the air mass is not uniform. Like an airplane on final having a head wind shift to a tailwind is going to have a large increase in rate of decent. many planes have crashed because of this. So more is involved than just "Turbulence" . But there are are many old pilots that swear turning from a head wind to a tail wind produces some loss of lift.


dorbie

Jan 20, 2010, 5:42 PM
Post #16 of 134 (2774 views)
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Re: [in2jumping] Fatality - Tampa Bay, FL - 20 Jan 2010 [In reply to] Can't Post

High winds have no effect on your canopy vs. no wind once you're flying in them, except that they may tend to be more turbulent, but for the purposes of this discussion that's moot.

The only thing that changes in high laminar wind vs. no wind is the ground speed, but that's a big change and can cause humans to make mistakes about their rate of turn with varying ground speed, e.g. turning faster when heading downwind causing a sudden loss of altitude due to the canopy diving (or even inducing a stall in some aircraft).

This is directly related to Newton's first law of motion, read it and take it to heart:

Quote:
Every object in a state of uniform motion tends to remain in that state of motion unless an external force is applied to it.

It says "uniform motion", not stationary or moving, there is no difference between the two states. Your canopy in equivalent flight has the same airspeed in all laminar air, windy or not. The aerodynamic & gravitational forces applied have the same effect. Momentum is the same in the pilot's frame of reference.

This is not up for debate if you disagree you're wrong and may kill yourself if you think you need to or can turn differently downwind vs. upwind. And don't feel bad about not knowing this, it's an infamous and insipid debate in aerosports. It will not go away with this thread.

Believe Newton's first.


(This post was edited by dorbie on Jan 20, 2010, 5:48 PM)


captain1976  (D 7183)

Jan 20, 2010, 5:51 PM
Post #17 of 134 (2762 views)
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Re: [in2jumping] Fatality - Tampa Bay, FL - 20 Jan 2010 [In reply to] Can't Post

2 weeks ago at DeLand on Saturday the winds aloft were at least 40 at 4K and about 70 at altitude. They died to about 15 or so at 100ft so I decided to jump.

Turbulence was quite strong during the canopy ride and when I made my final turn for landing I was really
tracking across the ground. When I cranked a hard right toggle to make that final turn, nothing happened.

Quite scary but it was apparent I was in some kind of wind or turbulence related effect and based on where I was I could easily have been killed.

Thankfully the thing finally decided to turn and the landing was uneventful, except for the cookies I lost.

Thats the last jump I will make in high winds!


dorbie

Jan 20, 2010, 5:55 PM
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Re: [vanair] Fatality - Tampa Bay, FL - 20 Jan 2010 [In reply to] Can't Post

I love the fishbowl analogy, brilliant, I had not heard it before.

In reply to:
But there are are many old pilots that swear turning from a head wind to a tail wind produces some loss of lift.

And they're categorically wrong. There is no known physical process known to do this to any perceptible degree. It is a psychological issue.

Edit to add, unless they turn differently or ALSO say that when turning from a downwind to upwind with the same control input they also experience the same loss of lift.


(This post was edited by dorbie on Jan 20, 2010, 6:02 PM)


happythoughts  (D License)

Jan 20, 2010, 6:04 PM
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Re: [dorbie] Fatality - Tampa Bay, FL - 20 Jan 2010 [In reply to] Can't Post

Quote:
Every object in a state of uniform motion tends to remain in that state of motion unless an external force is applied to it.

Toggle input is an external force. The wing does not
have a static shape.

Fly directly into a 20mph wind. Stall your canopy, then
release the brakes. Results may vary.

Steering lines can be used to change speed and the
shape of the canopy. The wind will have a different effect
on a canopy when its shape has changed.


dorbie

Jan 20, 2010, 6:20 PM
Post #20 of 134 (2722 views)
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Re: [happythoughts] Fatality - Tampa Bay, FL - 20 Jan 2010 [In reply to] Can't Post

In reply to:
Quote:
Every object in a state of uniform motion tends to remain in that state of motion unless an external force is applied to it.

Toggle input is an external force. The wing does not
have a static shape.

Fly directly into a 20mph wind. Stall your canopy, then
release the brakes. Results may vary.

Steering lines can be used to change speed and the
shape of the canopy. The wind will have a different effect
on a canopy when its shape has changed.

None of this affects anything that has been said. It doesn't matter where the force comes from. It is the SAME flying at any speed in any configuration whether in wind or not. The only thing that changes is ground speed.

Consider the fishbowl analogy. Imagine you're flying your canopy in a massive fishbowl full of air and making turns. Now put your massive fishbowl on the back of a truck and drive it at a steady 60 mph and fly your canopy in it If if the fishbowl is opaque and you can't see the outside world, you would not be able to tell the difference between moving or not the turns you make would look and feel the same. Now make the fishbowl transparent and you're flying in 60 MPH wind, upwind & downwind turns are the same in either frame of reference.

If you don't understand this then you have no business trying to argue the point, you need to take remedial physics 101.

Stall your canopy and release the brakes and you will fall with the moving air such that your horizontal airspeed will tend to zero as your vertical speed increases. Drop a lead weight and it will fall with the moving air if given long enough to stabilize, it will not fall vertically in wind, it will move until it's horizontal airspeed is near zero through friction. This is why you calculate wind drift during freefall due to 'uppers'.


(This post was edited by dorbie on Jan 20, 2010, 6:22 PM)


kallend  (D 23151)

Jan 20, 2010, 6:22 PM
Post #21 of 134 (2721 views)
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Re: Fatality - Tampa Bay, FL - 20 Jan 2010 [In reply to] Can't Post

To no-one in particular.

All the stuff about you canopy not knowing anything about windspeed in a uniformly moving airmass is, of course, true (an inertial reference frame in the jargon of the subject).

HOWEVER, (1) on a windy day there is almost always a wind shear within a couple hundred feet of the ground. Thus the airmass is no longer moving uniformly, and

(2) unless flying on instruments we give our control inputs by ground reference. Since what we see is different on a windy day, we give different control inputs to fly the same turning path over the ground and the outcome can be quite different. One of the things you have to do in pilot training is fly circles around a point in a wind. The difference in control input going upwind, crosswind or downwind is quite considerable.


(This post was edited by kallend on Jan 20, 2010, 6:22 PM)


The111  (D 29246)

Jan 20, 2010, 6:28 PM
Post #22 of 134 (2705 views)
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Re: [happythoughts] Fatality - Tampa Bay, FL - 20 Jan 2010 [In reply to] Can't Post

In reply to:
Toggle input is an external force. The wing does not have a static shape.

No, your toggle is INTERNAL to the reference frame (the moving mass of air).

In reply to:
Fly directly into a 20mph wind.

Physically impossible. Wind only exists on the reference frame of the ground. You can walk into wind, but you can't fly into it. You only fly in air.


dorbie

Jan 20, 2010, 6:42 PM
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Re: [kallend] Fatality - Tampa Bay, FL - 20 Jan 2010 [In reply to] Can't Post

In reply to:
To no-one in particular.

All the stuff about you canopy not knowing anything about windspeed in a uniformly moving airmass is, of course, true (an inertial reference frame in the jargon of the subject).

HOWEVER, (1) on a windy day there is almost always a wind shear within a couple hundred feet of the ground. Thus the airmass is no longer moving uniformly, and

(2) unless flying on instruments we give our control inputs by ground reference. Since what we see is different on a windy day, we give different control inputs to fly the same turning path over the ground and the outcome can be quite different. One of the things you have to do in pilot training is fly circles around a point in a wind. The difference in control input going upwind, crosswind or downwind is quite considerable.

Yes, agreed to all of this.

To point 2, yes, and canopy pilots need to guard against the difference flying an equivalent ground track might have in different winds, especially in the pattern. They can for example be tricked into a dive although they perceive the flight maneuver is not that radical. There's a double whammy here if matching a ground track; making a 90 turn from downwind onto a base leg matching a ground track reference must become significantly more than 90 to match that ground track AND is more likely to be executed as sharp turn inducing a dive due if it is not anticipated as an extended eliptical ground track turn. So it is necessary to take the time and distance to execute the turn safely. It may have a bearing on the fatality that sparked this discussion.


happythoughts  (D License)

Jan 20, 2010, 7:17 PM
Post #24 of 134 (2659 views)
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Re: [The111] Fatality - Tampa Bay, FL - 20 Jan 2010 [In reply to] Can't Post

In reply to:
In reply to:
Toggle input is an external force. The wing does not have a static shape.

No, your toggle is INTERNAL to the reference frame (the moving mass of air).

I have seen a canopy collapse due to a pressurization
change brought on by toggle input. So, toggle/riser input
is obviously not a benign factor to how your canopy flies.

Also, I have been on a full elliptical loaded over 1.4 and
done two things. I have done a slow flat turn (slow rotational speed). Also, I have cranked it down and
my rotation speed was quick. Instead of hanging vertically under the canopy, I was nearly horizontal with it and diving fast.

If you are flying with a 30mph wind, the effect of any
toggle input is going to be greater because your additional linear speed has been translated into greater rotational speed.

The greater rotational speed will cause your angle of attack to increase and the canopy will be more at a dive angle.

Also, per the discussion of momentum, obviously the
oncoming force of the wind (in that airmass) is going to affect
the canopy a whole lot faster than your body when
the canopy turns into the 30mph wind.
That difference in momentum can be easily shown by
using toggles to induce linetwists.


The111  (D 29246)

Jan 20, 2010, 7:22 PM
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Re: [happythoughts] Fatality - Tampa Bay, FL - 20 Jan 2010 [In reply to] Can't Post

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If you are flying with a 30mph wind

Again, you don't fly in wind. Wind only exists on the ground.

In reply to:
Also, per the discussion of momentum, obviously the oncoming force of the wind (in that airmass)

Wind is not "oncoming" in the airmass. It is only oncoming to people on the ground. When you are in the airmass, you ARE the wind.


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