Aerodynamics Discuss the concepts of aerodynamics here

Downwind Turns

Old 03-02-2009, 03:18 PM
  #101  
Sabrehawk
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One more little tidbit, the only thing we as pilots need to compensate for in a wind, is "Drift". And all that requires is to turn(normally of course) into the wind slightly so as to follow the desired ground track. IE: In a landing pattern, so we dont "drift" out too far.

And to ignore the optical illusion that the plane is sliding sideways. For it is not, but rather is still flying straight through the air.

It only looks that way.
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Old 03-02-2009, 03:34 PM
  #102  
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Originally Posted by cbatters View Post
Comment from Nephewewas that upwind/downwind turns are different having nothing to do with ground speed or reference.


Clint
I defer to your nephew.

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Old 03-02-2009, 04:06 PM
  #103  
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It's an ill wind that....
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Old 03-02-2009, 05:37 PM
  #104  
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Originally Posted by AEAJR View Post
]

I agree. Fortunately there is a lot of it. and it is hot air. There should be enough to thermal my Ford Taurus.
.
Yeah, for hilarity and things you don't learn, the downwind turn brings out the..................... uh ............ best?
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Old 03-02-2009, 06:14 PM
  #105  
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No issue or confusion that wind is irrelevant when flying in any particular direction. The only thing that matters is airspeed. (grooud speed is irrelevant.)

However, I maintain that the laws of aerodynamics and various books written about aviation do not trump physics and the laws regarding Conservation of Energy. The energy state of a plane flying with the wind is higher than a plane flying into the wind and the stored energy has an impact on how much altitude is gained or lost when turning.

It has been insightful to see the lack of common coutesy demonstrated by a number of people on this board.


Regards,

Clint
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Old 03-02-2009, 06:43 PM
  #106  
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Originally Posted by cbatters View Post
However, I maintain that the laws of aerodynamics and various books written about aviation do not trump physics and the laws regarding Conservation of Energy.
I quite agree. None of us can ever beat physics. However it's certainly possible that at least some of us have a faulty understanding of the physics of this situation while the understanding of others is more in accord with reality.

Probably best if we just decide for ourselves which of us is which .

Steve
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Old 03-02-2009, 06:46 PM
  #107  
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Airspeed is referenced to the air.
When the plane is flying in the airmass, its energy state using -airspeed- is solely relatable to the airmass.
When considering the energy state of the airplane and the airmass -relative to the ground-, then the reference point is changed, so the total energy in the system.. plane AND airmass is different, but the plane has no "cognition" of this altered point of reference.
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Old 03-02-2009, 06:48 PM
  #108  
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I'm inclined to think that the most 'dangerous' part of any turn has little to do with which direction it is, but is precisely at the point of the lowest airspeed (due to AoA, etc.), whether it is turning upwind or down.
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Old 03-02-2009, 06:49 PM
  #109  
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Originally Posted by slipstick View Post
I quite agree. None of us can ever beat physics. However it's certainly possible that at least some of us have a faulty understanding of the physics of this situation while the understanding of others is more in accord with reality.

Probably best if we just decide for ourselves which of us is which .

Steve
Well said from the gentleman in the Uk.

I would offer to set this up on a simulator but then people would argue that the simulator is also wrong.


Peace.
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Old 03-02-2009, 06:51 PM
  #110  
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I've been follow'in all this and the truth is just keep your foot in it and keep you nose down!!!
After land'in it's a good idea to let let your hands stop shake'in and let your thumbs return to their former color, ya'll's bub, steve
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Old 03-03-2009, 12:49 AM
  #111  
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Originally Posted by cbatters View Post
No issue or confusion that wind is irrelevant when flying in any particular direction. The only thing that matters is airspeed. (grooud speed is irrelevant.)

However, I maintain that the laws of aerodynamics and various books written about aviation do not trump physics and the laws regarding Conservation of Energy. The energy state of a plane flying with the wind is higher than a plane flying into the wind and the stored energy has an impact on how much altitude is gained or lost when turning.

It has been insightful to see the lack of common coutesy demonstrated by a number of people on this board.


Regards,

Clint
You crack me up there

Describe energy.

Describe why the energy state is different and or how.

Point us in the direction of any good reading that may be able to do this better than your efforts to date.

PS. We are only Debating a topic. If you feel my attitude towards you is offensive or Rude or what have you . Please feel free to PM me and I will do my best to calm it down (If it is possible )

Bryce.

PS. Thanks for being brave enough to speak you mind and not just bend to our word just because we say something is right. It take courage guts and Determination to do this. And I commend you on having done so.

Bryce. (Again)
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Old 03-05-2009, 02:07 PM
  #112  
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I spoke to a friend today. What he told me I knew before and has nothing to do with a turn, but interesting to share.

He is paraplegic with some 5% use of his hands and mostly in his thumbs. He lives on a smallholding. When he is flying his small electric plane, he sits in his wheelchair in front of his garage. He always try to come in low and very slowly for the landing and try to land as close as possible to his feet so he does not struggle to retrieve the plane.

The wind blowing mostly from one direction, that is from behind the garage toward the front. What he found, coming in high where the plane flies in the air stream, it reaches the separation point of the air stream and the still air behind the garage profile. Every time the plane will drop like a stone as it has almost zero ground speed and enters this still air zone where its airspeed is suddenly almost zero as well. With his plane, it does not matter how much power he is giving at that stage, the plane will not pick up enough air speed to recover in time and it will hit the ground. Fortunately his plane is small and light so there is no damage so to speak.
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Old 03-05-2009, 04:43 PM
  #113  
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Originally Posted by rebell View Post
I spoke to a friend today. What he told me I knew before and has nothing to do with a turn, but interesting to share.

He is paraplegic with some 5% use of his hands and mostly in his thumbs. He lives on a smallholding. When he is flying his small electric plane, he sits in his wheelchair in front of his garage. He always try to come in low and very slowly for the landing and try to land as close as possible to his feet so he does not struggle to retrieve the plane.

The wind blowing mostly from one direction, that is from behind the garage toward the front. What he found, coming in high where the plane flies in the air stream, it reaches the separation point of the air stream and the still air behind the garage profile. Every time the plane will drop like a stone as it has almost zero ground speed and enters this still air zone where its airspeed is suddenly almost zero as well. With his plane, it does not matter how much power he is giving at that stage, the plane will not pick up enough air speed to recover in time and it will hit the ground. Fortunately his plane is small and light so there is no damage so to speak.

It's great he has found something to ease his situation. I hope he has many fun flights.
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Old 03-05-2009, 05:59 PM
  #114  
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Originally Posted by rebell View Post
I spoke to a friend today. What he told me I knew before and has nothing to do with a turn, but interesting to share.

He is paraplegic with some 5% use of his hands and mostly in his thumbs. He lives on a smallholding. When he is flying his small electric plane, he sits in his wheelchair in front of his garage. He always try to come in low and very slowly for the landing and try to land as close as possible to his feet so he does not struggle to retrieve the plane.

The wind blowing mostly from one direction, that is from behind the garage toward the front. What he found, coming in high where the plane flies in the air stream, it reaches the separation point of the air stream and the still air behind the garage profile. Every time the plane will drop like a stone as it has almost zero ground speed and enters this still air zone where its airspeed is suddenly almost zero as well. With his plane, it does not matter how much power he is giving at that stage, the plane will not pick up enough air speed to recover in time and it will hit the ground. Fortunately his plane is small and light so there is no damage so to speak.
.
I've the opposite, where getting a light model -across- the boundary between the still air at ground level and the air flowing past at some altitude causes the model to -stop-! in mid air.
Dynamic soaring with gliders uses this difference in airflows to get the models to speeds in the 300 mph range, with NO motors!
.
A downwind approach across the airflow layers in your friends case would have the model come from the moving air to the still air with some airspeed, so he could maintain control.
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Old 03-05-2009, 06:27 PM
  #115  
rebell
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A downwind approach across the airflow layers in your friends case would have the model come from the moving air to the still air with some airspeed, so he could maintain control.
I said he is paraplegic. He is actually mostly quadriplegic as he has no feeling or control from his shoulders downwards.

Since he is in a wheelchair, he cannot turn around and look in any direction at free will without using his hands, which is occupied with the Tx. He also cannot do a crosswind approach because of obstacles both sides of the garage.

His way of doing a good landing is to come in low from a distance away in order not to be influenced by the difference in airflow.
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Old 03-06-2009, 01:08 AM
  #116  
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It was merely a suggestion as to how to get around the wind-shear situation.
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Old 03-06-2009, 03:49 AM
  #117  
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Thanks for that. Sorry if I sounded defensive, I just wanted to explain his situation. After many years even myself sometimes forget the fact that he can not do things the way we do.

The other thing that is interesting is that the plane does not have energy (some of the stuff that was under discussion here, that is why I mentioned it here) to continue flying when it changes wind layers.
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Old 03-06-2009, 10:20 AM
  #118  
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Originally Posted by rebell View Post
Thanks for that. Sorry if I sounded defensive, I just wanted to explain his situation. After many years even myself sometimes forget the fact that he can not do things the way we do.

The other thing that is interesting is that the plane does not have energy (some of the stuff that was under discussion here, that is why I mentioned it here) to continue flying when it changes wind layers.
Curious
how dose the plane handle when he dose a take off ?
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Old 03-06-2009, 11:13 AM
  #119  
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With the take-off he give full power and by the time he reaches the wind, the plane already has enough speed to compensate for the sudden wind speed difference. Also, a bit further from the garage the wind speed change is more graduate as from the ground up and not with a sudden change as in the position he is landing closer to him. It does look as if the plane get a sudden kick from behind when it enters the higher speed wind after take off.

At our club, when flying in strong cross wind at low level past the clubhouse, you must compensate for the change in wind in that area, even though you fly about 30 – 40 meters away form the clubhouse. It is specially important when doing take off and landing.
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Old 03-06-2009, 01:17 PM
  #120  
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That sudden apparent kick from behind is just an increase in ground speed due to losing the headwind. Otherwise all else hasnt really changed.

But that sudden increase in ground speed I can imagine may give the pilot a desire to cut the throttle, but that will only cause a loss of altitude and not airspeed. That is unless he feeds in any up elevator.

I think your friend is doing right getting it lower further out and coming in from a lower altitude, rather than having to drop it from higher up, closer in.
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Old 03-07-2009, 01:11 AM
  #121  
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If the plane is turning in to the wind(upwind) the air will be flowing faster over the airfoil producing more lift which will make the planes control faster.
If the plane turns with the wind (down wind) the air flowing over the airfoil is slower producing less lift making the control's slow and sloppy until the plane reaches a sufficent speed.
I think during this time for the beginner is the worst time because the plane does not respond well and over correction can be made
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Old 03-07-2009, 01:20 AM
  #122  
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Originally Posted by Sabrehawk View Post
That sudden apparent kick from behind is just an increase in ground speed due to losing the headwind. Otherwise all else hasnt really changed.

But that sudden increase in ground speed I can imagine may give the pilot a desire to cut the throttle, but that will only cause a loss of altitude and not airspeed. That is unless he feeds in any up elevator.

I think your friend is doing right getting it lower further out and coming in from a lower altitude, rather than having to drop it from higher up, closer in.
In sailing that initial reaction is called heeling. When you turn and get that first "gulp" of air . The boat is pushed into the water and takes off.
I'm not sure if it's used in aviation.
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Old 03-07-2009, 01:24 AM
  #123  
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Well, I know it seems that way but believe me it isnt so.
There is simply no difference in airspeed or airflow over the wings in either upwind or downwind flight. It is an optical illusion that we see from the ground and what gets us in trouble is reacting to this illusion.

It only looks that way, but in truth is not that way at all. Fly any turn as if there were no wind and all will be well. I assure you, and you can take that to the bank. (And collect interest)

Drift is what happens in wind, no airspeed change, only a flight path change/ (IE; an out of shape turn, or figure eight or whatever.)
Here is a small excerpt from "Stick and Rudder", at the beginning of chapter 6.
And then there is the wind.

"Much of the art of flying has turned out to be much simpler than you had expected: the airplane stable, the air without pockets, the hieght not all that terrifying. But then there is the wind: the air, the medium in which you move, is itself in motion. And that now brings on a whole string of quite unexpected complications. You discover that, whatever wind there is, even the slightest breeze, has it's effects on you every single minute of flight: it distorts your curves, it falsifies your climbs and glides, it pulls your figure eights out of shape, it makes your ship go one way while it's nose points another way. If the wind is across your direction of flight, it makes the airplane slide over the scenery in a crablike gait: sometimes so much so that, if you want to look where you are going, you must look out the side window of the cabin!
If the wind is at your tail, it makes the plane hurry amazingly and keeps messing you up by getting you there too soon, before you have had time to plan your next maneuver. If the wind is from ahead, you lose speed(groundspeed), and with a slow ship in a strong wind it may happen that you stand still in the air or even go backward.
It is dismaying to find that mere wind-so flimsy, so imtangible a thing-can blow a heavy powerful machine about at will; but it is even more dismaying to discover, by and by, that the effects of wind are almost exactly what your common sense would expect them not to be.

Puzzles
There are endless examples of this. Does an airplane get more lift when flying "against" the wind, than flying "with" it?
The beginning student will almost always say that of course it does; why it stands to reason! the experienced pilot says that of course it does not. Again-does a tail wind cause a loss of lift? In any batch of cadets there will be some who will argue yes: the tail wind blowing from behind tends to blow the wings down instead of up! The experienced pilot says no, the the tail wind causes no loss of lift. Another example-what happens when an airplane gets into a headwind so strong that it gets "stuck"? Some will argue that of course it will stall and drop, for an airplane cannot fly unless it has speed. But the experienced pilot knows that it will not stall.
Even if you were being blown backward, he says just simply dont look down at the ground and you wont even notice the wind.
Logic does not seem to mean a thing. Is it easier you might ask to fly with the wind than to fly against it? Does it take less horsepower,or does it take more? In any group of cadets some will argue that downwind flight requires less throttle, because the wind will help to give the airplane the necessary speed. It seems logical, but it is wrong. Some will argue that downwind flight requires more throttle because the airplane will have to fly so much faster. It also seems logical but is also wrong."
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Old 03-07-2009, 02:25 AM
  #124  
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If you take off into the wind your take off distance will be reduce!
If you take off with a tail wind your take off distance will increase!
It doesn't matter what speed the aircraft is going it's the speed of the airflow across the airfoil(wing) which produces lift
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Old 03-07-2009, 05:40 AM
  #125  
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Well now when did we start talkin bout take-off's, of course thats true and it confirms what I just posted.
No difference in airspeed with or into the wind, only ground coverage and track.
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