I was reading a few posts regarding the tragic accident over on the full scale forum, and the effects of the wind. I had some questions, but thought it would be better to discuss them here. Let me start by saying I only have about 20 hours in a Cherokee and 1 hour in an Extra 300, so I am by no means an expert on full scale flight. I do have several years experience flying r/c though, and have alway heard from experts that the airplane does not know the wind is blowing. This is assuming a steady wind, not gusts.
My question is this. Why does the plane "weather vane" into the wind? For instance, if you pull to a vertical upline in a cross wind, the nose will invariably start to point in the direction the wind is coming from. In fact, I usually need to hold opposite rudder in order to maintain a straight line.

If you're flying in a coordinated, level line before the pull, your airplane won't weathervane.

The wind pushes against your rudder, pushing the tail of the plane with the wind, and the nose into the wind. To Flyfalcons' point, if you are flying a coordinated level line prior to pulling up, then you are already applying rudder to compensate for the wind. if you pull the elevator to go vertical, you should leave whatever rudder control exactly as it was prior to the pull.

Because the rudder and vertical, are like a sail on a sailboat. The wind pushes the tail around. Wind at your back will turn a RC plane towards you on a flybye, and wind in your face will point the nose away from you. Full scale sees the same.
Rutnbuc

Lets assume the entry is not level or coordinated, but when you pull to vertical, you correct to a perfectly vertical attitude. Then let go. My plane (Comp arf Extra 260) will always require opposite to keep that vertical attitude. Or it will start to turn into the wind.
If the plane truly did not know the wind was blowing, I would think the attitude would remain constant once set and the track would veer off.

Originally Posted by reyn3545

The wind pushes against your rudder, pushing the tail of the plane with the wind, and the nose into the wind. To Flyfalcons' point, if you are flying a coordinated level line prior to pulling up, then you are already applying rudder to compensate for the wind. if you pull the elevator to go vertical, you should leave whatever rudder control exactly as it was prior to the pull.

This is incorrect. If you're holding rudder in level flight then it isn't coordinated level flight. Wind compensation is done through crabbing, which is coordinated level flight.

Originally Posted by kwilson

If the plane truly did not know the wind was blowing, I would think the attitude would remain constant once set and the track would veer off.

That's correct, it would. If your plane is yawing in the direction of the wind then it wasn't truly vertical in the first place.

That is precisely where I feel the theory that wind has NO effect on a flying plane might be flawed. I don't know if weight and balance are whats causing it, our extreme power to weight, or what. But I assure you I can get the plane perfectly vertical, or even go slightly past vertical with the wind, and it will weather vane back into the wind.

This will happen in both directions so I dont think spiraling slipstream is creating this issue.

Maybe I wasn't clear.... if you are crabbing a plane to keep it in a line parallel to the runway, then you pull up, you should keep roughly the same amount of rudder in the plane to keep it flying a vertical line... it will still be crabbing, just vertical now... but flying a straight vertical line.

If you adjusted the rudder to make the fuse perfectly vertical, your plane would be tracking in the direction of the wind.

You're watching your plane from the ground as it travels in an air mass. Believe me, you have no way of telling whether you made a perfect coordinated pull to upright or not.

Originally Posted by reyn3545

Maybe I wasn't clear.... if you are crabbing a plane to keep it in a line parallel to the runway, then you pull up, you should keep roughly the same amount of rudder in the plane to keep it flying a vertical line... it will still be crabbing, just vertical now... but flying a straight vertical line.

If you adjusted the rudder to make the fuse perfectly vertical, your plane would be tracking in the direction of the wind.

I don't think you understand what crabbing is. There is no rudder being applied in a proper crab.

I'm a moron when it comes to this but basically crabbing or not, the wind is effecting the plane. Isn't it?
If you have to crab on horizontal or vertical , you are compensating for the force of the wind..... no?

To give yourself a specific line over the ground, yes. But you are still flying perfectly straight through the air mass in which you are flying. When I'm flyin at work and am compensating for a 150 knot jetstream coming 90 degrees off my nose, is the plane experiencing 150 knots of force on the tail? No. It is experiencing zero force on the tail because I am flying perfectly coordinated. I have to look at my instruments to tell me that there is any wind where I'm at.

Originally Posted by Flyfalcons

You're watching your plane from the ground as it travels in an air mass. Believe me, you have no way of telling whether you made a perfect coordinated pull to upright or not.

I do agree. That is why I mentioned straightening up and setting the vertical line after the pull. And before anyone thinks so, I am not trying to start a pissing contest, just trying to suggest that a plane flying straight and level in an airmass can feel wind.

Lets say you are flying due north. The wind is blowing from the east. You have to set the plane at 10 degrees in order to maintain a flight path of 0 degrees. So you are crabbing at 10 degrees. My thought is there is more pressure on the right side of the aircraft than the left side. Since the rudder is part of the right side of the aircraft, it feels this pressure differential. Since it is much taller than the rest of the plane and further behind the CG than the nose is forward of the CG, it has more torque and will cause the plane to veer to an eventual 90 degrees, or due east, if not corrected with opposite rudder.

No, there isn't more pressure on the right side of the aircraft when crabbing into the wind.