Interesting Questions

[pembquist]

Do you stop rolling when you center your stick?

I would have to say that depends. There is so much more happening in an airplane than just the abstraction of the rolling wings. So I'm asking about the abstract model of the rolling wings without things like dihedral or the empennage or gravity.  My intuition says it stops rolling, my logic says that with one wing at a higher aoa than the other and no modifications in wing camber/aoa in the aileron area than one wing will be generating more lift than the other and now and now....I look at the wikipedia adverse yaw diagram again and it says the ascending wing has a lower effective AOA which is what I thought till you said I had it backwards and then I thought it was the ascending wing which had a higher AOA and now I see streamlines and a wing moving down and it looks like  a higher AOA to me again.  So my logic right now says that: ailerons in trail, the descending wing is at a higher AOA than the ascending wing so a moment opposite the direction of rotation is created thus stopping rotation.  One post back my intuition would have been the same but my logic would have said that the spinning would get faster.

To be young again.

[GScholz]

The wing rotating down will obviously have a higher AoA than the wing rotating up (from the point of view of the pilot). The ailerons have to fight this effect and that is why an aircraft will not just roll faster and faster, but stabilize after a short time to its maximum roll rate where these forces are in balance. Center the stick and the plane will stop rolling, but not instantly; the difference in AoA between the wings gradually equalize as the rotation slows.

[pembquist]

the difference in AoA between the wings gradually equalize as the rotation slows.

Thank you.  That is what I thought originally.

[colmbo]

And it is that added lift that creates more induced drag, not "sticking out in the slip stream"... I could even ask what "slip stream" WTF are you talking about? A slipstream is the wake of an object moving through a fluid.

If you really think a deflected aileron doesn't cause drag how do you think a speed brake works? It sure as heck isn't due to lift.

[GScholz]

How can you possibly come to that conclusion? You even quoted me stating it creates drag! Induced drag! A "speed brake", and I assume you mean an air brake, doesn't create lift and thus no induced drag, it creates form drag.

[earl1937]

Do you stop rolling when you center your stick?

No, the aircraft will stop banking or rolling when you apply opposite aileron and rudder. If you induce a 30 degree banked turn and turn the aileron back to neutral, the inherent instability of the aircraft will want to continue banking the aircraft until some outside force acts on it. i.e., flight controls. The larger the aircraft, the more stable in bank maintenance when making a turn, but that is due to a number of factors, non of which are mentioned here. Most hi speed aircraft must have a small amount of opposite aileron to maintain a certain bank angle. The only way an aircraft stops rolling when you center the ailerons is, and there is dihedral in the wing, which helps it stay in stable level flight, it will eventually return to level flight.
The Piper series of a/c, the PA's are and were successful to the flying public and inexperienced pilots because they were easier to maintain level flight because of the dihedral of the wing. The P-39 we have here in Aces High has a very pronounced wing dihedral and why it is not a popular "dog fighter" against other aircraft.

[earl1937]

So you don't think flaps increase lift... Right... Carry on then.  

 I don't think that is what he means. Flaps will increase lift from the fuseledge outward to the point where the flaps end, provided you do not extend the flaps to the point of producing more drag than lift. Flaps change the "camber" of the wing next to the fuseledge, because wings which are designed correctly, are designed to stall from the wing root outward, so that the pilot can maintain aileron control though out the low speed ranges. Factory test pilots and wind tunnel test show the aircraft manufacturer the maximum extension of flaps before drag overcomes the benefit of added lift.
The B-29 we have here in Aces High is a good example of incorrect flap setting for takeoff. At a takeoff weight of 124,500 lbs in the real B-29, we used 18 degrees of flap because Boeing says anything over that produces more drag than lift.
I see people in here crash because the aircraft, the 29, when it spawns out on the runway, it automatically lowers 50% of flaps! That is all well and good, as ground effect will allow the 29 to get off the ground quicker, but when you have to "milk" the flaps up to accelerate to climb speed, you have to raise flaps 25% at a time, which allows the aircraft to settle back into the ground unless the pilot is very skilled in the slow flight realm of the 29. When I post a 29 mission in the game, I advise the guys to raise flaps all the way up, engage auto takeoff, full power, engage wep and leave it alone, it will climb out just fine, even from a medium size field. If they want to use 25% flaps, OK, but don't raise them until you get at least 1,000 feet AGL.

[earl1937]

21 feet  sin(45)=.707

The effective lifting area is 30 feet when in a 45 degree bank, as measure vertically from the wing up! The point being that the wing doesn't produce lift in a 45 degree bank, as it does in level flight. The point is to make the student pilot understand that to overcome the loss of lift, by the banked wing, is to either add elevator back pressure in order to maintain altitude, at which point the aircraft will slow and more back pressure on the elevator is required or you must add power to compensate for the loss of airspeed and effective lift in order to maintain a constant altitude during the turn.

[earl1937]

I would have to say that depends. There is so much more happening in an airplane than just the abstraction of the rolling wings. So I'm asking about the abstract model of the rolling wings without things like dihedral or the empennage or gravity.  My intuition says it stops rolling, my logic says that with one wing at a higher aoa than the other and no modifications in wing camber/aoa in the aileron area than one wing will be generating more lift than the other and now and now....I look at the wikipedia adverse yaw diagram again and it says the ascending wing has a lower effective AOA which is what I thought till you said I had it backwards and then I thought it was the ascending wing which had a higher AOA and now I see streamlines and a wing moving down and it looks like  a higher AOA to me again.  So my logic right now says that: ailerons in trail, the descending wing is at a higher AOA than the ascending wing so a moment opposite the direction of rotation is created thus stopping rotation.  One post back my intuition would have been the same but my logic would have said that the spinning would get faster.

To be young again.

Consider this! If you are in a Hurricane, the real aircraft, which has zero dihedral, and you induce a 30 degree bank to the left and then take your hands and feet off the flight controls, two things will happen: #1- the bank angle will continue to increase, #2- your nose in relation to the horizon will decrease, therefore inducing additional speed. Less assume for a minute that before you started the left turn, you had the aircraft trimmed to straight and level flight, hands off. Because of the lack of dihedral, the wings will not level by themselves. Because you had the aircraft trimmed for level flight, at a certain airspeed, the nose of the aircraft will try to maintain an angle which will give you that IAS you had it trimmed for, but because of the increasing bank angle and the resulting increase in speed, the trim loses its effectiveness and you wind up with what is called a "grave yard" spiral. Take the same set of situations in a Spitfire, because of the dihedral of the wing, it will, if left alone and not exceeding the VNE, it will eventually return to the congf which you had it in before you induce the left turn! If will wander all over the sky, but eventually will return to straight and level flight.
I know this thread is not about dihedral in wings, but the dihedral does play an important part in the discussion about adverse yaw and etc in this discussion.
Again, as I have said, when in level flight, induce left aileron with no rudder, and watch what your aircrafts nose will do. It will move RIGHT first and then will begin to bank to the left, hence the explanation of "the rudders primary function is to overcome the adverse yaw, created by the down aileron".

[FLS]

I would have to say that depends. There is so much more happening in an airplane than just the abstraction of the rolling wings. So I'm asking about the abstract model of the rolling wings without things like dihedral or the empennage or gravity.  My intuition says it stops rolling, my logic says that with one wing at a higher aoa than the other and no modifications in wing camber/aoa in the aileron area than one wing will be generating more lift than the other and now and now....I look at the wikipedia adverse yaw diagram again and it says the ascending wing has a lower effective AOA which is what I thought till you said I had it backwards and then I thought it was the ascending wing which had a higher AOA and now I see streamlines and a wing moving down and it looks like  a higher AOA to me again.  So my logic right now says that: ailerons in trail, the descending wing is at a higher AOA than the ascending wing so a moment opposite the direction of rotation is created thus stopping rotation.  One post back my intuition would have been the same but my logic would have said that the spinning would get faster.

To be young again.

You're right it's a lower AOA on the rising wing. The details do get complicated but the point remains that there is more yaw during the roll than the turn.

[GScholz]

No, the aircraft will stop banking or rolling when you apply opposite aileron and rudder. If you induce a 30 degree banked turn and turn the aileron back to neutral, the inherent instability of the aircraft will want to continue banking the aircraft until some outside force acts on it. i.e., flight controls. The larger the aircraft, the more stable in bank maintenance when making a turn, but that is due to a number of factors, non of which are mentioned here. Most hi speed aircraft must have a small amount of opposite aileron to maintain a certain bank angle. The only way an aircraft stops rolling when you center the ailerons is, and there is dihedral in the wing, which helps it stay in stable level flight, it will eventually return to level flight.
The Piper series of a/c, the PA's are and were successful to the flying public and inexperienced pilots because they were easier to maintain level flight because of the dihedral of the wing. The P-39 we have here in Aces High has a very pronounced wing dihedral and why it is not a popular "dog fighter" against other aircraft.

Bank and dihedral effects were specifically left out of Pembquist's thought experiment. As if the aircraft was pinned in a wind tunnel only able to rotate around its roll axis. If we include bank angle and turning effects then the aircraft will weathervane into a turn resulting in faster airflow around the outside wing creating more lift, resulting in the aircraft continuing to roll into the turn (unless countered by stabilizing dihedral or low Cg) until it ends up in an inverted dive.

[earl1937]

Bank and dihedral effects were specifically left out of Pembquist's thought experiment. As if the aircraft was pinned in a wind tunnel only able to rotate around its roll axis. If we include bank angle and turning effects then the aircraft will weathervane into a turn resulting in faster airflow around the outside wing creating more lift, resulting in the aircraft continuing to roll into the turn (unless countered by stabilizing dihedral or low Cg) until it ends up in an inverted dive.

You have lost me on this explanation! Wind does not "weathervane" aircraft into a turn sir. Heat thermals, or turbulence can induce the start of a turn, or the pilot inputs some control movement. If an aircraft "weathervanes" during straight and level flight, it is a flat turn, and hardly noticeable. I think you meant to say "rear" CG instead of low CG. The only thing CG does is affect the AOA of the wing, in any maneuver. If a pilot ends up in a inverted dive, its because he did something stupid! A lot of non instrument rated pilots die each year, because they lose control of the aircraft and it winds up in a grave yard spiral or spin, usually pulling the wings off first, then becoming the famous lawn dart.

[GScholz]

Yes we definitely have a communication problem... I was (trying) to explain that a roll will produce a bank angle (uncoordinated turn) ... This will create a horizontal component to the lift vector pushing the aircraft sideways into the bank... This will make the plane weathervane into the bank due to the sideways motion acting on the horizontal stabilizer... This will increase the airflow over the outer wing while reducing the airflow over the inner wing further increasing the bank angle until the aircraft ends up in an inverted dive/spiral... This is if the pilot does nothing at all to correct it, or if stabilizing dihedral effect or low CG is able to counter the roll. Low CG... where CL is significantly above CG, like in most high-winged aircraft, is a stabilizing force in it self that acts as a pendulum effect which will tend to bring the aircraft back to a wings level attitude (manipulating this low CG is the only way to control a hang glider for example). Most heavyweight high-wing aircraft has to have some anhedral (drooping wings) to counter the low CG/high CL and make the aircraft less stable and more maneuverable.

This is getting tiresome. Time for a beer! 

[colmbo]

How can you possibly come to that conclusion? You even quoted me stating it creates drag! Induced drag! A "speed brake", and I assume you mean an air brake, doesn't create lift and thus no induced drag, it creates form drag.

Hey, all I'm saying is the aileron also produces form drag.  The adverse yaw is not caused by induced drag alone.

[GScholz]

... I'm having a beer.