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in2jumping

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

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Quote from a pilot: "An aircraft that can be rotated to face downwind faster than it can accelerate with the wind, will experience an airspeed loss and performance loss."
Why don't you answer my questions and address the facts instead of the typical fallacy of appealling to authority?

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Lets put it this way: What would happen if an aircraft turned down wind on takeoff?


On the runway? It would take more ground speed to take off, although the air speed meter would show the very same value.

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Why does an aircraft climb quicker into the wind than when downwind?

How come? E.g. 300ft/min would be in any direction.

Remember. Your wing flies relative to the air, not to the ground.

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Quote from a pilot: "An aircraft that can be rotated to face downwind faster than it can accelerate with the wind, will experience an airspeed loss and performance loss."
Why don't you answer my questions and address the facts instead of the typical fallacy of appealling to authority?



All of your questions have been answered, and the facts have been addressed, multiple times in this thread by billvon, kallend, myself, and others. Please read the whole thing if you haven't yet. I know it's long. :| You are mistaken in your ideas. A plane does not climb faster into the wind. A plane takes OFF faster in a shorter distance into the wind, because planes take off from the ground. Once you are in the air the ground ceases to exist for all intents and purposes.

And I've always hated the "appeal to authority" approach too, so I'll give you a point for calling that out. But I'm also taking a point away, for the fact that in the very same post, you made your own appeal to authority (quote from a pilot).
www.WingsuitPhotos.com

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I am really surprised that people don't understand this concept. Flying in the wind is different than flying without wind due to inertia and airflow issues. [...]
Lets put it this way: What would happen if an aircraft turned down wind on takeoff?
Why does an aircraft climb quicker into the wind than when downwind?
The same factors effecting the aircraft effect the us in parachutes.




Oh my god, we're back to square one...sigh.

No it doesn't climb quicker into the wind.

Nothing changes turning downwind (excepting visual illusions and the special case of wind shear).

No the stall doesn't change with or without wind.

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Are you trying to clame an aircraft has the same climb rate downwind as upwind?

Maybe at some point when I have the time I can produce a video of an aircraft turning downwind with no wind and high wind with the same inputs in both cases. You will see the no wind aircraft fly like normal.....the one dealing with a downwind turn will stall. This is due to inertia. And remember the aircraft has a means of propulsion and parachutes do not.

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And I've always hated the "appeal to authority" approach too, so I'll give you a point for calling that out. But I'm also taking a point away, for the fact that in the very same post, you made your own appeal to authority (quote from a pilot).


I did quote the pilot as since you appealed to authority I figured you would listen to someone with authority.

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>Are you trying to clame an aircraft has the same climb rate downwind as
>upwind?

Yes, it is exactly the same.

>Maybe at some point when I have the time I can produce a video of an
>aircraft turning downwind with no wind and high wind with the same inputs
>in both cases. You will see the no wind aircraft fly like normal.....the one
>dealing with a downwind turn will stall.

You're not a pilot, are you.

>Lets also remember that according to current physics a bumble bee cant fly . . .

Urban legend. Bumblebees have no problems flying, and areodynamics explains that quite well.

>and humans aren't capable of lift as much as we do.

Where'd you get that one?

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Are you trying to clame an aircraft has the same climb rate downwind as upwind?



Yes.

Because it does.

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Maybe at some point when I have the time I can produce a video of an aircraft turning downwind with no wind and high wind with the same inputs in both cases.



How do you know the inputs are the same? How have you measured the precise application of control deflection?
Do you want to have an ideagasm?

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I did quote the pilot as since you appealed to authority I figured you would listen to someone with authority.



You're confusing me with somebody else, just as you are confusing the air with the ground.
www.WingsuitPhotos.com

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I am really surprised that people don't understand this concept. Flying in the wind is different than flying without wind due to inertia and airflow issues. [...]
Lets put it this way: What would happen if an aircraft turned down wind on takeoff?
Why does an aircraft climb quicker into the wind than when downwind?
The same factors effecting the aircraft effect the us in parachutes.




Oh my god, we're back to square one...sigh.

No it doesn't climb quicker into the wind.

Nothing changes turning downwind (excepting visual illusions and the special case of wind shear).

No the stall doesn't change with or without wind.


I understand the issues with visual references but I beleive that what is happening here is certain effects are so small in most cases that it is left out in all cases where as they can become large enough in some to have an effect.
Lets look at a plane flying in a moving car. At this point visual references have no effect as in the car the plane appears to fly in a circle in relation to the car but in a large spiral in relation to the ground the car is moving over. The air in the car is the "wind" as it is moving in relation to the ground. This is where most people stop and is good enough for most all applications such as general aviation and parachuting but not enough for all. In this example inertia is left out. The airplane appears to remain at the same speed and does in relation to the car but not the earth, therefore, when the plane turns down towards the front of the car (downwind) it is accelerating. This is better understood if you remove the earth and replace it with a flat theoretical plane that is not moving at all. Once again, inertia doesn't seem to play any part as the car is only going 60 miles per hour and the plane it probably paper and doesn't have much inertia. Scale all that up and now inertia begins to play a part!
Lets also make the turn more extreme. Lets say the control surfaces such as the elevator deflect at say 60 degrees so the turn is extremely sharp. That means it must accelerate even faster. Lets make the plane heavier and the car much faster. Now inertia and its effects start to show.
Once again they may not show very much in gerenal aviation or parachuting or hardly at all but lets forget about airspeed versus ground speed and look at real speed in relation to no motion. Now things are different.
If I made a turn, and I do, with an aircraft with 45 degree defection on the elevator down wind and even with a thrust to weight ratio of 2:1 I must give myself more altitude on a windy day to give the aircraft enough time to fight inertia and accelerate to the speed of the air mass (wind) for it to start flying again.

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Urban legend. Bumblebees have no problems flying, and areodynamics explains that quite well.


Current aerodynamics does when such things like the reynald numbers are used but this was not always the case. Physics did not always have the math and ability to explain it.

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I did quote the pilot as since you appealed to authority I figured you would listen to someone with authority.



You're confusing me with somebody else, just as you are confusing the air with the ground.


My bad, I should have type "he" instead of "you".

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>Current aerodynamics does when such things like the reynald numbers
>are used but this was not always the case.

That's Reynolds number. And you are correct, we have not always known about it. But at no point did anyone publish anything that said "bumblebees can't fly."

>Physics did not always have the math and ability to explane it.

Correct. Now we do.

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Quote from a pilot: "An aircraft that can be rotated to face downwind faster than it can accelerate with the wind, will experience an airspeed loss and performance loss."
Why don't you answer my questions and address the facts instead of the typical fallacy of appealling to authority?



All of your questions have been answered, and the facts have been addressed, multiple times in this thread by billvon, kallend, myself, and others. Please read the whole thing if you haven't yet. I know it's long. :| You are mistaken in your ideas. A plane does not climb faster into the wind. A plane takes OFF faster in a shorter distance into the wind, because planes take off from the ground. Once you are in the air the ground ceases to exist for all intents and purposes.
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I will concede that you are correct, a plane will climb just as fast into the wind and downwind. I did confuse visual references in that particular case.

PS. Please see post #89 for everything else.

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>Lets look at a plane flying in a moving car. At this point visual references
>have no effect as in the car the plane appears to fly in a circle in relation
>to the car but in a large spiral in relation to the ground the car is moving
>over.

Exactly.

>In this example inertia is left out.

No, it isn't.

>The airplane appears to remain at the same speed and does in relation
>to the car but not the earth, therefore, when the plane turns down towards
>the front of the car (downwind) it is accelerating.

Yes, it is accelerating towards the front. When it turns towards the rear of the car, it is accelerating towards the rear.

>Lets also make the turn more extreme. Lets say the control surfaces
>such as the elevator deflect at say 60 degrees so the turn is extremely
>sharp. That means it must accelerate even faster. Lets make the plane
>heavier and the car much faster. Now inertia and its effects start to show.

No, they don't.

Every pilot has had to do turns in place. Typically there are three steps to this:

1) Find a landmark and circle over it in no wind. Set a bank angle, keep the nose on the horizon and circle away. Easy.

2) Find a landmark and circle over it in high winds. At first this seems just as easy. There's no bizarre "stall when you turn downwind" or anything, and there's no acceleration when you turn into the wind. The plane works exactly the same. You can't even tell the winds are 40 knots.

But then you notice something - you're not over the same landmark any more! While you have been doing your perfect circles in the air, you've been drifting with the wind. Looking down on your ground track, you'd see a spiral, not a circle.

So then you try again. This time, you try to compensate for the wind. During the downwind part of the circle you increase bank angle to keep the same ground track at the higher groundspeed. During the upwind part of the circle you decrease bank angle to keep the same ground track at the lower groundspeed. Now your perfect easy circle gets all difficult because you have to constantly compensate for your drift over the ground.

That is why people confuse airspeed and groundspeed - because they often confuse what you have to do to stay over the same point on the ground with how the plane behaves in the air.

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>The airplane appears to remain at the same speed and does in relation
>to the car but not the earth, therefore, when the plane turns down towards
>the front of the car (downwind) it is accelerating.

Yes, it is accelerating towards the front. When it turns towards the rear of the car, it is accelerating towards the rear.


No, if the plane is making a circle in the car there is no acceleration in relation to the car. The plane is making a circle at a constant speed in relation to the car but not in relation to a stationary object. In relation to the stationary object the plane in the car flies slower when facing the back of the car and faster when going toward the front meaning it accelerates when turning toward the front and decelerates when turning towards the back. Therefore, when looking at inertia you cannot use the car as the reference point but the stationary object for true speed.

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"If you get a big enough canopy, you'll actually gain altitude."




Umm..if there are thermals, YOU DO! B|


325 'Mighty Mac' on a hot day over a blacktop runway...I watched my altimeter go UP several times in the 15 minutes I was playing around below 1500'










~ If you choke a Smurf, what color does it turn? ~

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>No, if the plane is making a circle in the car there is no acceleration
>in relation to the car.

Then it will always either remain stationary or travel in a straight line. You cannot change direction without acceleration.

>In relation to the stationary object the plane in the car flies slower
>when facing the back of the car and faster when going toward the front
>meaning it accelerates when turning toward the front and decelerates
>when turning towards the back. Therefore, when looking at inertia you
>cannot use the car as the reference point but the stationary object for
>true speed.

If you believe that then ask yourself this:

That car is driving on a road. If the car is traveling east in the USA, it's also moving about 800mph above and beyond its speed. Why should we use that "stationary object" by the side of the road when the planet is spinning at 800mph? Why not use the center of the earth, which is much more 'stationary' than the road?

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Wow.

So in your world it is harder for someone in the backseat to hand the driver a beer (beer's inertia is increasing) than for the driver to hand a beer to the back seat (beer's inertia is decreasing)?

In our world (the real world) the work needed to hand a beer back and forth is the same regardless of which way it is being handed. The work required doesn't care if the momentum (not inertia) is increasing or decreasing, it is the change that matters. If I need to change the momentum of a body by one unit, I need to apply one unit of force to do it (for the nerds: for each unit of mass over one unit of time). I need to apply that same unit of force regardless of which way I'm pushing the object.

This is really basic stuff. Newton figured this shit out centuries ago. It hasn't changed (except for really high energies, and then Einstein had some improvements).

- Dan G

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Are you trying to clame an aircraft has the same climb rate downwind as upwind?



Don't confuse angle of climb and rate of climb. Climbing into the wind will have a greater angle of climb relative to the ground than climbing downwind, but the rate of climb, which is altitude gain per unit time, is the same. Climbing into the wind will cover less ground distance than climbing downwind for the same altitude gain, but the time to gain that altitude will be the same.

Now, to the question of the downwind turn. You said,

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Maybe at some point when I have the time I can produce a video of an aircraft turning downwind with no wind and high wind with the same inputs in both cases. You will see the no wind aircraft fly like normal.....the one dealing with a downwind turn will stall. This is due to inertia. And remember the aircraft has a means of propulsion and parachutes do not.



At one point, you wrote the following:

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Quote from a pilot: "An aircraft that can be rotated to face downwind faster than it can accelerate with the wind, will experience an airspeed loss and performance loss."



That pilot you quoted put a very big stipulation on his statement. He said that the aircraft must be capable of changing heading from upwind to downwind more quickly that the acceleration necessary to maintain airspeed. That is not a common capability.

Maybe your model aircraft can accomplish such a thing, but aircraft built on a human scale cannot generally get that sort of performance. (I couch my statement with "generally" because I can say with great assurance that there is not some sort of drone aircraft now that might be able to do this at the scale we are talking about. Or maybe one of those military aircraft that have negative stability and must be flown by wire by a computer can do it.)

pchapman mentioned that wind shear can cause this sort of effect, and that is one of the few ways that we actually see this with "full scale" aircraft.

In a microburst situation, the aircraft is first in a strong headwind, then in a strong downdraft, and finally in a strong tailwind. All this happens without the aircraft actually changing heading. When a "full scale" aircraft transitions from the downdraft to the tailwind, it indeed has an inertial problem to overcome. It is absolutely true that aircraft have crashed when they lost their airspeed in this way. But this depends on a very particular sort of wind situation. It does not happen in a situation of constant wind. It happens in the extreme wind shear conditions of a microburst.

Most aircraft cannot accomplish such a change from upwind flight to downwind flight quickly enough to beat the acceleration that will be occurring during the turn. As I said, maybe your model aircraft can. The flight performance in terms of roll rate and turn rate of model aircraft far far exceed the capabilities of any "full scale" aircraft.

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That car is driving on a road. If the car is traveling east in the USA, it's also moving about 800mph above and beyond its speed. Why should we use that "stationary object" by the side of the road when the planet is spinning at 800mph? Why not use the center of the earth, which is much more 'stationary' than the road?


This is the reason in my original example that I replaced the earth with a theoretical plane that does not move. Therefore, when I was refering to a stationary object I was refering to a truely stationary object not a object on the earth that is moving.
So if the plane in the car is making circles at a constant speed of 20mph and the car is going 60 and is on a theoretical plane that is not moving at all then when the plane flies towards the back of the car it is going 40 and when flying towards the front it is going 80 so when it transitions and makes the turn from back to front it accelerates 40mph and inertia must be applied in this way with an acceleration of 40mph not 0 in relation to the car.

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