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Downwind Turns "The Real Dangers"

Old 12-10-2009, 11:00 PM
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HX3D014
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Default Downwind Turns "The Real Dangers"

Speaking from experience. Give your account of what is a real danger.

If you are vague as to what the exact cause was. then pose it as a question.

I would like us to attempt to set out a clear explanation of different events and follow with cause and effect per event.

The down wind turn in steady wind has been discussed with relation to energy involved at either end of the turn, but that was generally a discussion on the energy involved relative to the air mass.

lets face it. these conditions do not exist. there is always a gradient with altitude (given you fly RC close to the ground , 100ft close) and there will always be some vertical movement of the air, not to mention gusts.

So Lets hear it.

What happened and why.

PS the other thread is available for Education. IE if you wish to dispute the statement; "there is no more energy or less energy require to produce a 180deg turn over 8seconds up wind compared to 8 seconds down wind within a steady wind" then Please do so at that thread, more details on that in that thread.
This thread "The Real Dangers" is supposed to describe "Real Dangers" to the inexperienced. (me included )

consequently, there may be discussion on "Upwind Turns" the "Real Dangers"
and also cross wind to up wind or down wind. and Down wind or up wind to Cross wind "Real Dangers"
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Old 12-10-2009, 11:43 PM
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aramid
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One of my friends stalled and half-spun his E-Flite Apprentice while practicing slow flight in a strong wind. He made his downwind turns look roughly the same as his upwind turns, so from the airplane's perspective the downwind turns were much tighter and more aggressive. On one pass, he just got a bit too slow in the middle of his turn, and the airplane dropped a wingtip and pretty much fell. He ended up making basically an inverted landing and the only damage was a cracked cowl, broken prop, and a few scratches on the motor.
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Old 12-11-2009, 12:25 AM
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capn chaos
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Originally Posted by aramid View Post
One of my friends stalled and half-spun his E-Flite Apprentice while practicing slow flight in a strong wind. He made his downwind turns look roughly the same as his upwind turns, so from the airplane's perspective the downwind turns were much tighter and more aggressive. On one pass, he just got a bit too slow in the middle of his turn, and the airplane dropped a wingtip and pretty much fell. He ended up making basically an inverted landing and the only damage was a cracked cowl, broken prop, and a few scratches on the motor.
Aramid,
Just want to make sure we are on the same page (not the hyper technical, go nowhere page.
You mentioned downwind turns were more aggressive which I interpret as being tighter and with more authority. This does sound like a turn across wind that ends up on the start of a down wind leg.
At the risk of adding confusion in a practical sense, My Katy II unpowered slope soarer would turn in in its on length when doing a turn at the end of an upwind leg. The turns started at the end of a down wind leg were mushier.The difference being air velocity under the wing vs air velocity on top of wind This was a two channel bird and turns used banking (ailerons) and up elevator Rudder/elevator turns would be different no doubt

This is the same phenomenum we see in sailboats in current (water)...essentially the same as air current (wind). The danger is quite simple. You must allow more room for your turn when commencing a turn after a down wind leg (drift). The slower the flight characteristics the more room you have to allow.
Lost my bow rail (while I was in my slip) to a guy who failed to understand this "margin of drift". (sailboat- a wing in the water- a wing in the wind).

Just speaking in practical (real life) terms- no theory expressed or implied, thats for the other thread.
And thats all I'm gonna say bout that
Forest Gump
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Old 12-11-2009, 05:11 AM
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aramid
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Yes, I think we're on the same page. If you very carefully move the sticks in the same position when you're turning both into and out of the wind, the turn into the wind will seem much faster and crisper, because the plane will move less relative to the pilot.

My friend's problem was that he tried to make both turns appear equally tight. This meant that when turning out of the wind, he was actually using far more control deflection and letting his speed get too low. The result was a stall - in his case, rather close to the ground.
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Old 12-11-2009, 09:52 AM
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have to be careful comparing a sailboat to a plane. A boat has it's hull in one medium (the water) and it's sail in another (the moving air). the water and air are both moving independantly and both effect the sailboat.

A plane is quite different. A plane is in one medium only (the air). The ground moving below it has no physical effect on the plane because the plane has no physical connection to the ground.



Having said that.. yes i and just about everyone has had trouble with turns when turning from downwind to crosswind. the reason for this is not 'wind blowing on top of the wing' its simply that the planes ground speed is higher due to the wind, so to make a turn in the same radius (relative to the flyer stood on the ground) when heading downwind means you have to apply much greater control input, bank the plane harder, and pull more 'G'. If you're not careful this can result in a stall. The reason for the stall is simply that the pilot tried to turn the plane too tight. It's pilot error brought on by trying to fly the plane from a ground based reference.

Strangely enough free flight models dont have any trouble turning in the wind

Steve

Last edited by JetPlaneFlyer; 12-11-2009 at 10:55 AM.
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Old 12-11-2009, 07:39 PM
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Well boy howdy Steve here has hit the nail on the head, and I mean right dead on too.
Truth is there is no "real danger" with either turn, downwind or upwind. Ok, there is one real danger and that is the ground based pilot's perception of whats going on up there. That there is a perception that there is a difference between them at all. If one can simply ignore it, and fly the turn normally like any other he'll get through it like any other.

No need for more throttle, no need for more up elevator.
Once in the air, the airplane cannot feel the wind for the wind no longer blows against it like it did while on the ground. The plane is traveling both through, and with the moving air. And it's path is a compound of the two.
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Old 12-12-2009, 10:57 AM
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Originally Posted by Sabrehawk View Post


Once in the air, the airplane cannot feel the wind for the wind no longer blows against it like it did while on the ground. The plane is traveling both through, and with the moving air. And it's path is a compound of the two.
A lot of people say this but it is not entirely true. This rule only applies to steady state wind speed. In reality the wind can gust to many times is usual speed and a plane in the air will certainly feel it. Todays reedings in my area are 4mph wind with gusts to 14 mph. If a gust like that hits you in a turn you're going to know about it.
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Old 12-12-2009, 12:59 PM
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Originally Posted by Buck Rogers View Post
A lot of people say this but it is not entirely true. This rule only applies to steady state wind speed. In reality the wind can gust to many times is usual speed and a plane in the air will certainly feel it. Todays reedings in my area are 4mph wind with gusts to 14 mph. If a gust like that hits you in a turn you're going to know about it.
Buck,
Gusts, wind sheer, turbulence and any other unsteady wind condition can and does effect a plane, in a turn or when flying straight, no one is debating that.
The issue being discussed is the effect of a steady wind.

Steve
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Old 12-12-2009, 04:22 PM
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Originally Posted by JetPlaneFlyer View Post
Buck,
Gusts, wind sheer, turbulence and any other unsteady wind condition can and does effect a plane, in a turn or when flying straight, no one is debating that.
The issue being discussed is the effect of a steady wind.

Steve
I see what you're saying but the old downwind turn subject has been done to death in previous threads. I think most of us know the plane will not feel the effects of a steady wind but it is very rare that such a condition exists in reality. If people are having trouble with downwind (or up wind) turns I think we should consider everything.

For example my Ripmax Spitfire has a tendency to roll sometimes on the crosswind leg of an upwind turn - you have to be ready to correct it. Clearly, given what has already been said, this must be due to a gust of wind and not some hypothetical steady wind.
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Old 12-12-2009, 04:26 PM
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Oh yes yes, in those unsteady ever changing conditions it certainly can feel it, at least mommentarily. But I usually wont be found out flying in that.
But we can certainly find ourselves caught in it, and then theres just one thing that can save you and I'd refer to the teachings of another of my favorite masters, Bruce lee.
That is to not be tense, but ready. To be like water, ever flowing to conform to whatever it encounters. And if the opponent expands, I contract. If it contracts, I expand.
To have no technique, as technique. No style, as style.

Be like water.

And at the first lull in the wind, land that thing.
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Old 12-12-2009, 04:45 PM
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I thought I'd share a great website I frequent, it's an Australian one and very informative and edifying. And one particular section of it deals with what I think we speak of here, the dangers of low level turns. For even full scale aircraft deal with the kind of atmospheric conditions we RC guys do down here below 1000ft AGL. And whats taught there, applies I think.
Note that it points out the misperceptions that ground referencing can induce. The same way we can be fooled from our ground based point of view.

http://www.auf.asn.au/groundschool/turn_speed.html
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