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Old Aug 22, 2012, 01:21 AM
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Originally Posted by Toysrme View Post
i think the entire premis of this post is newbie and boarderline moronic.

it was put to death june 26. why is there still discussion on it?
You find weevils in your cheerios this morning or something?
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Old Aug 22, 2012, 05:27 AM
An itch?. Scratch build.
eflightray's Avatar
South Wales U.K.
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Originally Posted by Toysrme View Post
i think the entire premis of this post is newbie and boarderline moronic.

it was put to death june 26. why is there still discussion on it?
Yet you still had to have a look to see what was posted, and even posted yourself.

Welcome to the club for the 'boarderline moronic'. We need a President, fancy the job ?.
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Old Aug 23, 2012, 11:14 PM
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Toowoomba, QLD, AUSTRALIA
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Originally Posted by CNY_Dave View Post
What's funny is I've been having this discussion with fairly senior people and experienced pilots, context is aircraft separation assurance maneuvers and collision avoidance maneuvers.

"If 2 planes are approaching at right angles and one is downwind and the other turns away from the downwind plane because of the wind the downwind plane is approaching faster until the turning plane can speed up'.

Shoot me, shoot me, shoot me.
This is the best part about education and training. As you move up each level you realise that what you were taught wasn't exactly true but it was close enough to the truth to keep you out of trouble.

Sticking a metal tool into either or both of the correct 2 of the 3 holes in an electrical outlet is perfectly safe even if it's switched on but you'd certainly never try to teach that to a child, just as the level of aerodynamic principles taught to pilots is enough to allow them to operate their craft safely even if some of the info is a bit dodgey and not always 100% correct.

As an Electrical Engineer I apply the simpliest level of electrical principles I can that adequately describe the systems I'm working on, even though I know full well that that's not what's REALLY going on.
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Old Aug 24, 2012, 11:21 AM
Tossing planes into the snow
Canada, BC, Smithers
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Originally Posted by bjr_93tz View Post
As an Electrical Engineer I apply the simpliest level of electrical principles I can that adequately describe the systems I'm working on, even though I know full well that that's not what's REALLY going on.
That is a very interesting perspective, and it does apply to the downwind turn phenomenon. There have been a few times in my life when people have asked me how a transistor works. I usually explain how a triode tube works instead, because the concepts of particles moving through space and valves are easier for laymen to understand. Then I tell them that the transistor uses a very different method to achieve a similar effect.

The title of this thread should really be called "How to land a plane in windy and gusty conditions", but it's all working out anyway. There have been several people who have submitted some well thought-out strategies complete with do's and don'ts. Couldn't have hoped for more.
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Old Aug 24, 2012, 12:32 PM
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Originally Posted by Jovanx View Post
Well, it sorta makes sense as long as "faster" and "slower" are referring to ground speed and not air speed. The statement as quoted is a little confusing because of the grammar, but I think I know what you mean.

Nobody ever has a problem with a downwind turn at 9000 feet. It's when we are close to the ground and thinking about landing that the phenomenon occurs. I am assuming that the word "approaching" means they are working on their landing strategy.
What many people think of as 'the dreaded down wind turn' is in fact a quite different phenomenon, 'ground affect'.
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Old Aug 24, 2012, 01:40 PM
Tossing planes into the snow
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Originally Posted by sablatnic View Post
What many people think of as 'the dreaded down wind turn' is in fact a quite different phenomenon, 'ground affect'.
Ground effect is a completely different phenomenon and it occurs whether the wind is blowing or not. When a plane is only a few feet off the ground, the air being pushed down by the underside of the wing creates a "cushion" of air that pushes back up against the wing, increasing the lift. That is why birds like to cruise along so close to the surface of the water. It's a free ride.

The downwind turn is a phenomenon that occurs at an altitude that is too high for the ground effect. It is usually when the pilot is making his second-last turn before landing, and he is planning on the last turn bringing him back around into the wind for the landing.

The ground does have an effect on wind, creating turbulence that can be a problem for pilots, but that is not what is meant by the term "ground effect".
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Old Aug 24, 2012, 10:52 PM
Thailand
Joined Aug 2010
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Flying upwind or downwind is the same for the model but the pilot perceives the speed differently. It looks like it's flying faster on the downwind leg but it's only the ground speed that is higher.
As model pilots we force the aircraft into a circuit that is relative to the ground and there seems to be a difference between up and downwind flight.
If you have ever watched a free flight model doing circuits and flying off downwind then you will notice the non circular flight pattern but yet the model thinks it just flying in circles.
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Old Aug 24, 2012, 11:34 PM
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Originally Posted by Fox-composites View Post
Flying upwind or downwind is the same for the model but the pilot perceives the speed differently. It looks like it's flying faster on the downwind leg but it's only the ground speed that is higher.
As model pilots we force the aircraft into a circuit that is relative to the ground and there seems to be a difference between up and downwind flight.
If you have ever watched a free flight model doing circuits and flying off downwind then you will notice the non circular flight pattern but yet the model thinks it just flying in circles.
The model does experience different aerodynamic effects depending on whether or not its flying in a tail wind or head wind, just like a real plane. A tail wind can both make a plane move faster relative to the ground, and reduce lift. A full scale pilot can also tell he/she is moving slower relative to the ground facing a head wind than in a tail wind, both by looking outside, and watching ground speed on the GPS.

"downwind turn" is usually with a tail wind, because runways designated for landing (full scale) are always into the wind because it is much easier to land into a head wind than a tail wind. That said, even if there is 0 wind it is still called a downwind turn as long as you are headed parallel to the runway in the opposite direction as you are intending to land.
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Old Aug 25, 2012, 10:35 AM
3D? I only got two thumbs!
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Originally Posted by seeingeyegod View Post
A tail wind can both make a plane move faster relative to the ground, and reduce lift.
Assuming the same airspeed (which presumably you are based on the "faster relative to the ground" part) there is no difference in lift regardless of the planes orientation relative to the wind. See previous posts in this thread.
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Old Aug 25, 2012, 03:38 PM
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Originally Posted by AeroKen View Post
Assuming the same airspeed (which presumably you are based on the "faster relative to the ground" part) there is no difference in lift regardless of the planes orientation relative to the wind. See previous posts in this thread.
Exactly, the air speed is NOT the same if you get a sudden tailwind. The air flow relative to the wings can suddenly slow down, reducing lift.
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Old Aug 25, 2012, 08:15 PM
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United States, IA, Hampton
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First base!
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Old Aug 25, 2012, 08:35 PM
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Pleasant Valley Modelport
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So turning downwind is making some pilots feel like they are stepping out on a glass bottom catwalk that is up 100 stories. It ain't that bad if you just carry a bit of extra airspeed for that one turn and if low, keep the power up. It's a mainly worthless worry.
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Old Aug 25, 2012, 09:52 PM
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Why do you need extra airspeed and power?
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Old Aug 26, 2012, 05:35 AM
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To have enough inertia to carry ther airplane through abnormal atmospheric deviations.
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Old Aug 26, 2012, 08:28 AM
An itch?. Scratch build.
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South Wales U.K.
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Originally Posted by seeingeyegod View Post
Exactly, the air speed is NOT the same if you get a sudden tailwind. The air flow relative to the wings can suddenly slow down, reducing lift.
Where does the 'sudden tail wind' come from ?, or do you mean turbulence and gusting.

If a model is flying at say 30mph air speed, (actually that's quite slow), and the air 'suddenly increases' from any direction, it will not greater affect that 30mph air speed. Not unless you are talking about a hurricane.
People here keep relating everything to 'downwind'. There is basically no such thing as 'downwind' to the plane, only to the person standing still who perceives a difference by relating it to ground speed.

Remember that the plane is in a block of air and is moving forwards through it at its flying speed, exactly the same as on a calm day. The only thing that can affect it is turbulence and gusting, which can happen in any situation, even during the in to wind landing.

Now if there was a sudden outbreak of FPV fliers who keep crashing during the turns on the landing leg, now that would make an interesting thread.
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