Airplane turning loads and aerodynamics

dtuuri said:
Actually, that's probably what confuses people. It doesn't 'explain' why an airplane changes heading. It might be intuitive for some, but there's a better way. As Wolfgang Langwiesche states on page 198 in his book Stick and Rudder,
"An airplane is turned by laying it over on its side and lifting it around through back pressure on the elevator."
​
The key, as he illustrates with a drawing, is the continual action of the horizontal tail surfaces, much like the feathers of an arrow or as a weather vane, to maintain the selected angle of attack, resulting in curving flight.

dtuuri
Click to expand...

Everskyward said:
So we can blame Stick and Rudder for confusing things because it doesn't mention how the airplane gets layed over on its side, or the fact that the airplane would still turn without additional elevator input.
Click to expand...


and from "STICK and RUDDER" page 202:

"But why back pressure on the stick? The back pressure on the stick is not necessary in order to get a turn; it is necessary only in order to get a good turn and to avoid a loss of altitude during the turn"



HAPPY NEW YEARS Y'ALL:D
 
Last edited:
register@teamandras.com said:
Along the same lines...

My flight school taught me that a plane turns in an arc as it moves forward, rather than just flies off at an angle, because the angled flight path associated with the thrust vector and the horizontal component of lift (top view) creates a relative wind - and the airplane constantly tries to face into the relative wind (bottom view, weathervaning).
Click to expand...

Nice graphic, Joe. Thanks for sharing this.
 
redtail said:
and from "STICK and RUDDER" page 202:

"But why back pressure on the stick? The back pressure on the stick is not necessary in order to get a turn; it is necessary only in order to get a good turn and to avoid a loss of altitude during the turn"



HAPPY NEW YEARS Y'ALL:D
Click to expand...


Ok I was beginning to wonder... Now it would be nice if "good turn" was defined other than avoiding a loss of altitude. And how did the airplane get into the bank to begin with?

Happy New Year to you too!
 
Seriously, you guys are freaking me out. I'm so confused now, I'm not going to be able to fly anything! :rofl:
 
register@teamandras.com said:
Along the same lines...

My flight school taught me that a plane turns in an arc as it moves forward, rather than just flies off at an angle, because the angled flight path associated with the thrust vector and the horizontal component of lift (top view) creates a relative wind - and the airplane constantly tries to face into the relative wind (bottom view, weathervaning).

Bearing in mind that this is just a student's interpretation and all (please correct if wrong), here's a diagram I drew a while back to illustrate the concept to myself.

Joe

turns.jpg
Click to expand...

yupp.
 
redtail said:
and from "STICK and RUDDER" page 202:

"But why back pressure on the stick? The back pressure on the stick is not necessary in order to get a turn; it is necessary only in order to get a good turn and to avoid a loss of altitude during the turn"
Click to expand...
There's no inconsistency there. The elevator is only one part of the horizontal surface. Together with the fixed part they provide a down force to control the angle of attack with the help of a trim tab. Just because no elevator is being used in a particular turn doesn't mean there's no down force, hence no angle of attack. There is one, and it causes the turn when banked--even if no elevator is used at all. Also, a stabilator (no fixed surface) is trimmed with the anti-sero tab to maintain a selected angle of attack.

As to how a plane gets banked in the first place, rudder can be used quite effectively when your hands are too busy to hold the yoke, like when fingering an E6b during a cross country. An undesired wind gust can bank without ailerons too, but of course the wing doesn't care how it got banked--it's going to keep the same angle of attack called for by the horizontal tail. Without the full component of gravity canceling the looping tendancy, a 'loop' in a horizontal plane results, as in Joe's bottom drawing (except he drew a slipping turn which makes the fuselage look like a player in this, which it isn't).

dtuuri
 
Last edited:
Why does everyone rave about "Stick and Rudder"? It is a terrible book. Yes, I read it. What a piece of crap. Emperor's New Clothing, people. Open your eyes.

:redface:

For the OP... Please turn in your certificate. Good God man!
 
I guess we should design airplanes without ailerons since the elevator purists don't even want to mention they might possibly have some factor in initiating and controlling a turn. :D

Happy New Year!
 
BobThePilot said:
Why does everyone rave about "Stick and Rudder"? It is a terrible book. Yes, I read it. What a piece of crap. Emperor's New Clothing, people. Open your eyes.
Click to expand...
Let me guess, you thumbed through it and upon finding that there was no discussion of having sex while flying, you came to the conclusion it was junk.
 
dtuuri said:
There's no inconsistency there. The elevator is only one part of the horizontal surface. Together with the fixed part they provide a down force to control the angle of attack with the help of a trim tab. Just because no elevator is being used in a particular turn doesn't mean there's no down force, hence no angle of attack. There is one, and it causes the turn when banked--even if no elevator is used at all. Also, a stabilator (no fixed surface) is trimmed with the anti-sero tab to maintain a selected angle of attack.

As to how a plane gets banked in the first place, rudder can be used quite effectively when your hands are too busy to hold the yoke, like when fingering an E6b during a cross country. An undesired wind gust can bank without ailerons too, but of course the wing doesn't care how it got banked--it's going to keep the same angle of attack called for by the horizontal tail. Without the full component of gravity canceling the looping tendancy, a 'loop' in a horizontal plane results, as in Joe's bottom drawing (except he drew a slipping turn which makes the fuselage look like a player in this, which it isn't).

dtuuri
Click to expand...

Yep, I think we're saying the same thing.
 
Rick Stowell is very big on "the elevator turns the airplane".

That said, banking the wings would not turn the airplane were it not for the weathervaning tendency to turn into the relative wind. Disregarding lift for a moment, you have thrust providing a forward vector and if you added a lateral vector such as that generated by banking, you would not get a turn but would get motion in the direction of the resultant vector in the x-y plane. You could never turn the airplane unless something causes the thrust vector to turn,. Weathervaning is what turns the nose, the thrust vector. If you are in a 45d bank, the horizontal stabilizer/elevator will be turning the nose as much as the tail/rudder turns the nose.
 
alfadog said:
Did I miss the part where someone said ailerons don't work?
Click to expand...

dtuuri said:
As to how a plane gets banked in the first place, rudder can be used quite effectively when your hands are too busy to hold the yoke, like when fingering an E6b during a cross country. An undesired wind gust can bank without ailerons too,
Click to expand...

While this is true, it is not the normal way of initiating a turn. I feel like I am in an alternate universe where people don't want to admit that the normal way to initiate a turn is to put the airplane in a bank with... ailerons.
 
Fearless Tower said:
Let me guess, you thumbed through it and upon finding that there was no discussion of having sex while flying, you came to the conclusion it was junk.
Click to expand...


It's all about sex with you, isn't it?

:lol:

Is that why you chose a phallic screen name? "Tower"? Fearless no less. Please.

:nono:

But, yes, a brief discussion on sex positions would have made a welcome addition to that book.
 
Everskyward said:
While this is true, it is not the normal way of initiating a turn. I feel like I am in an alternate universe where people don't want to admit that the normal way to initiate a turn is to put the airplane in a bank with... ailerons.
Click to expand...

Yes, you put the airplane in the bank with ailerons and then you neutralize the ailerons. Were it not for the weathervaning caused by the tailfeathers, you would then continue, banked and slipping, at a constant heading determined by the resultant vector. No turning would take place.
 
Everskyward said:
While this is true, it is not the normal way of initiating a turn. I feel like I am in an alternate universe where people don't want to admit that the normal way to initiate a turn is to put the airplane in a bank with... ailerons.
Click to expand...

I didn't get that impression from what he wrote.
 
alfadog said:
Yes, you put the airplane in the bank with ailerons and then you neutralize the ailerons.
Click to expand...
True.

alfadog said:
Were it not for the weathervaning caused by the tailfeathers, you would then continue, banked and slipping, at a constant heading determined by the resultant vector. No turning would take place.
Click to expand...
That's also true.

But here we are flying along straight and level. I want to turn so I do... what?

Now here we are in a banked turn and I want to stop the turn so I use what control?
 
Everskyward said:
True.

That's also true.

But here we are flying along straight and level. I want to turn so I do... what?

Now here we are in a banked turn and I want to stop the turn so I use what control?
Click to expand...

Right. What actually turns the airplane is somewhat transparent (if that is the right word) to the pilot. You might as well say that what turns the airplane is the little dial on the autopilot. We set up a bank with the ailerons and the weathervaning tendencies of the airplane cause it to turn. The steeper the turn, the more the elevator plays a part in the turn both is increasing lift and dragging the nose around.
 
alfadog said:
Right. What actually turns the airplane is somewhat transparent (if that is the right word) to the pilot. You might as well say that what turns the airplane is the little dial on the autopilot. We set up a bank with the ailerons and the weathervaning tendencies of the airplane cause it to turn. The steeper the turn, the more the elevator plays a part in the turn both is increasing lift and dragging the nose around.
Click to expand...
It's true that as you get into a steep turn the elevator plays more of a part. But if you want to roll out of a steep turn you're not going to do it solely with elevator. :D
 
Everskyward said:
It's true that as you get into a steep turn the elevator plays more of a part. But if you want to roll out of a steep turn you're not going to do it solely with elevator. :D
Click to expand...

Like I said, did I miss the part where someone said that ailerons don't work to bank and unbank the airplane, i.e. initiate, control, and stop a turn? I am just saying that most private pilot level reference materials say the aerodynamics of the turn (as opposed to how the pilot controls the turn) are that the bank turns the airplane and that just ain't so.
 
alfadog said:
Like I said, did I miss the part where someone said that ailerons don't work to bank and unbank the airplane, i.e. initiate, control, and stop a turn? I am just saying that most reference materials say the aerodynamics of the turn (as opposed to how the pilot controls the turn) are that the bank turns the airplane and that just ain't so.
Click to expand...
I assumed we were also talking about how the pilot controls the turn but maybe that was the other thread (the no flaps when turning thread) where some people kept insisting that the turn was controlled with elevator.

Also, am I reading the bolded statement correctly? That you think most of the reference material is wrong?
 
Everskyward said:
I assumed we were also talking about how the pilot controls the turn but maybe that was the other thread (the no flaps when turning thread) where some people kept insisting that the turn was controlled with elevator.
Click to expand...

This thread is "Airplane turning loads and aerodynamics"

Also, am I reading the bolded statement correctly? That you think most of the reference material is wrong?
Click to expand...

Yes, I do. I have looked at a lot of PPL materials and have quite a collection myself and almost uniformly it is "the banking of the wings turns the airplane" in the aerodynamics discussion. Banking the wing would not turn the airplane at all were it not for the tailfeathers and weathervaning, which is never mentioned in the context of the turn.
 
Last edited:
alfadog said:
Yes, I do. I have looked at a lot of PPL materials and have quite a collection myself and almost uniformly it is "the banking of the wings turns the airplane". Banking the wing would not turn the airplane at all were it not for the tailfeathers and weathervaning, which is never mentioned in the context of the turn.
Click to expand...
I agree with that. But they are probably trying to simplify it which may or may not be a good idea.
 
alfadog said:
This thread is "Airplane turning loads and aerodynamics"



Yes, I do. I have looked at a lot of PPL materials and have quite a collection myself and almost uniformly it is "the banking of the wings turns the airplane" in the aerodynamics discussion. Banking the wing would not turn the airplane at all were it not for the tailfeathers and weathervaning, which is never mentioned in the context of the turn.
Click to expand...

So saying the bank turns the plane, is just as flawed as saying the elevator turns it. It's a combination of lift produced by the wings when banked and the weathervaning of the tail.
 
Last edited:
Everskyward said:
I feel like I am in an alternate universe where people don't want to admit that the normal way to initiate a turn is to put the airplane in a bank with... ailerons.
Click to expand...

Just to further complicate the thread.....no one mentioned using the rudder yet. In some airplanes with significant adverse yaw, you will not be very effective trying to roll into a bank with ailerons alone.
 
Fearless Tower said:
Just to further complicate the thread.....no one mentioned using the rudder yet. In some airplanes with significant adverse yaw, you will not be very effective trying to roll into a bank with ailerons alone.
Click to expand...
I was trying to stay away from that. :rofl:
 
Everskyward said:
I agree with that. But they are probably trying to simplify it which may or may not be a good idea.
Click to expand...

redtail said:
So saying the bank turns the plane, is just as flawed as saying the elevator turns it. It's a combination of lift on the wings when banked and the weathervaning of the tail.
Click to expand...

Yes and yes. Just checked the FAA Pilot Handbook which is quite comprehensive otherwise and they go with the over-simplified "The horizontal component of lift is the force that pulls the aircraft from a straight flightpath to make it turn."

http://www.faa.gov/regulations_poli...on/pilot_handbook/media/PHAK - Chapter 04.pdf

Again, a turn involves rotation. Simply banking the wings would not induce rotation in the x - y plane (of course there is rotation around the longitudinal axis) but would cause the airplane to translate, not rotate. Rotation is caused by force couples, i.e. torque. The horizontal component of lift is only one force. Single forces cause linear motion, i.e. translation. A second coplanar force in the opposite direction is required for rotation. This second force is provided by the tailfeathers.
 
You must log in or register to reply here.
Back
Top