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Bruce
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Ailerons & Banking

Tue Jul 30, 2002 3:49 pm


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I'm still trying to understand how planes fly and I think, and someone correct me here, that this photo explains something. let me see if I've got this right.

Plane is banking left. Left wing ailerons are "up" slightly (both inboard & outboard). This sort of counteracts the lift created by the wings w/flaps extended, so the reduction in lift will make the left wing go "down" while the ailerons are in the opposite position on the right side (so that the whole plane won't descend), and the plane banks in the direction of the wing thats "down"....... is that close to correct? If you were sitting in that seat with someone next to you who knew nothing about flying, would that be the easiest way to explain to them how the ailerons help the bank? It's really a combination of that plus the rudder which they can't see out the window, right?

I have also seen a few pics that show the plane in a bank but the ailerons appear to be neutral....is that possible?

bruce
Bruce Leibowitz - Jackson, MS (KJAN) - Canon 50D/100-400L IS lens
 
saintsman
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RE: Ailerons & Banking

Tue Jul 30, 2002 6:21 pm

Bruce,

What you say is correct. If you want to explain banking to a layman, that can be difficult without going into how lift is produced. One of the easiest ways to give someone an idea is to tell them that one aileron goes up and the oposite one goes down. This forces one wing up and the other down and subsequently banks the airplane. (Tell them about sticking their hand out of the window and what happens when you change the angle of your hand). Now because the aircraft is now on it's side, the lift that was originally pulling the aircraft up is now pulling it sideways which is why the aircraft turns.

As for your pics that show the aileron neutral, if you think about it, once you are in a bank you would want the controls to be neutral otherwise you would carry on rolling.



For the rest of you, I know the explanation is not entirely correct but it is only intended for the man who knows nothing and has a passing interest.
 
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Bruce
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RE: Ailerons & Banking

Wed Jul 31, 2002 2:05 am

Is there more to the explanation?

Also, and pardon the dumb question, but what's the difference between executing a turn by banking versus simply deflecting rudder position? If you turn the rudder right, you'll go left(?) so why bank?


bruce
Bruce Leibowitz - Jackson, MS (KJAN) - Canon 50D/100-400L IS lens
 
Mr Spaceman
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RE: Ailerons & Banking

Wed Jul 31, 2002 3:41 am

Hi guys.

>Bruce, When ever I get involved in a thread that's about aerodynamics...I always get torn a new butt-hole. But here it goes anyway.

Another way to add more to the explanation is this....

The down going aileron increases lift because it's increasing that wing's camber shape, (which creates lift) thus that wing rises. As mentioned by Saintsman, a planeing effect also raises the wing (like a hand out a car window).

The up going aileron interferes with the wings camber and smooth airflow over the wing, thus killing some lift, so that wing drops. The planeing effect also plays a roll here.

As mentioned by Saintsman, once the desired bank angle is reached, the pilot must return the ailerons to neutral and even apply a few degrees of aileron input in the opposite dirrection of the bank/turn in order to keep the bank from becoming tighter & tighter.

In a left turn, a bit of left rudder input will help keep the turn coordinated. (meaning the aircraft is following it's nose instead of slipping ore sliding).

If you turn the rudder left, you will turn left, not right. The ailerons "bank" an aircraft around it's Lateral Axis (imagine a poll running through an aircraft from nose to tail)and the rudder "yaws" an aircraft around it's Vertical Axis (imagine a poll running vertically through the aircraft's center of gravity).

You can bank an aircraft into a turn by using only the rudders. This involves momentarily increasing airspeed over one wing (thus lift) and that wing will rise and the aircraft will bank. However, I'll let someone else explain this part of aerodynamics...if you want them to.

I hope this info helps a bit, and it is explained to help a new learner, NOT a scientist of aerodydamics!

Chris  Smile
"Just a minute while I re-invent myself"
 
FredT
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RE: Ailerons & Banking

Wed Jul 31, 2002 3:46 am

Bruce,
if you merely use rudder to turn, you'll be executing something called a flat turn.

Rudder will make the aircraft yaw, that is, make it slide sideways through the air. It will not make it turn. However, having the aircraft going sideways through the air will create a lot of drag. Some of this drag will likely be pointed in the direction of the yaw, slowly changing the aircrafts direction of travel.

This is very ineffective, compared to a normal turn. It is also rather unpleasant to everyone in the aircraft as you'll get pushed to the side.

Cheers,
Fred
I thought I was doing good trying to avoid those airport hotels... and look at me now.
 
Mr Spaceman
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RE: Ailerons & Banking

Wed Jul 31, 2002 4:46 am

Hi guys.

>Bruce, one thing that I learned from this forum about airliner's ailerons is that some airliner's outboard (slow speed) ailerons are adventually "Locked Out" into the neutral position as the airliner's airspeed increases. Above a certain airspeed only the inboard (high speed) ailerons move to control bank angle. Apparently this feature is meant to stop the twisting and torsion strains that are put on the airliner's wingtips when the outboard ailerons are deflected into highspeed airflow.

You can see this system at work in the photo below.


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Just some neat info.

Chris  Smile
"Just a minute while I re-invent myself"
 
Rick767
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RE: Ailerons & Banking

Wed Jul 31, 2002 8:46 am

FredT,

"Rudder will make the aircraft yaw, that is, make it slide sideways through the air. It will not make it turn."

That is not strictly true. The primary effect of the rudder is yaw, but the secondary effect is roll. If the rudder is displaced to the left, the aircraft will at first yaw to the left, and then it will roll to the left. Without a doubt a left turn will result.

Similarly turning to the left with the ailerons will at first cause a left bank, then a left yaw will also result. Primary effect here is roll, secondary is yaw.

I agree however that use of the rudder is a very inefficient way to turn an aircraft, but do not be fooled that rudders cause yaw and ailerons cause bank. They actually both cause both!

Rick.
I used to love the smell of Jet-A in the morning...
 
FredT
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RE: Ailerons & Banking

Wed Jul 31, 2002 8:55 am

Rick767,
you're right of course, but explaining the secondary effects of rudder would also mean explaining basic stability and dihedral/swept wings. If you can do that at this stage and level without causing confusion, you're very welcome.  Big grin

On an interesting side note, I recall hearing about German WWI pilots quite successfully flat turn in their Fokker Dr.I Triplanes. The large rudder apparently made this quite feasible. Can't remember why they sometimes chose to do this though.

Cheers,
Fred
I thought I was doing good trying to avoid those airport hotels... and look at me now.

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