Adverse Yaw

troopernflight

Well-Known Member
I was trying to wrap my brain around something and couldn't quite get it. Given that adverse yaw is caused by the rising wing's lowered aileron which causes more drag on that wing, as opposed to the lowered wing having less drag, what exactly is the explanation as to why the rising wing has more drag? Maybe I'm not understanding the aerodynamics of the issue, but is the air moving over the top of the wing not moving quicker than the air on the bottom of the wing? I see this causing more drag when the quicker moving air hits the raised aileron on the lowered wing, since the quicker moving air would impact at a greater velocity.
 

Cessnaflyer

Wooooooooooooooooooooooooooooooo
I think you are over complicating the impact forces. The aileron deflects very little and at full deflection depending on aircraft is only around 20 degrees which wouldn't act like putting a board perpendicular to the wind.

The main reason, like said before, is you are creating more lift on the rising wing which creates more drag relative to the descending wing.
 

shdw

Well-Known Member
Something to consider to help you remember: How much adverse yaw do you experience when in a stable (15-20 degree) bank?

The answer is none. The why was already covered here.
 

SteveCostello

My member is well-known.

I'm not posting this facetiously, either. That was never directly explained to me, so I always assumed it was aileron deflection, too. But yeah... not really enough deflection there, huh?
 

drunkenbeagle

Gang Member

I'm not posting this facetiously, either. That was never directly explained to me, so I always assumed it was aileron deflection, too. But yeah... not really enough deflection there, huh?
The outside wing is also moving faster, so there is also more form and parasite drag. FAR more pronounced with high aspect ratio, long wingspan. Gliders have nasty adverse yaw.
 

Cessnaflyer

Wooooooooooooooooooooooooooooooo
Something to consider to help you remember: How much adverse yaw do you experience when in a stable (15-20 degree) bank?

The answer is none. The why was already covered here.
How much overbanking tendency do you have though?
 

Springer

Well-Known Member
You would think adverse yaw would not be a factor in fighter a/c but in the hard wing (no auto slats or slots) F-4 it was so bad at high angles of attack we used the rudder only for roll control. We would practice confidence maneuver "rudder rolls" at 200kts. Aileron imput could lead to the a/c going out of control.
 

JLF

Well-Known Member
You would think adverse yaw would not be a factor in fighter a/c but in the hard wing (no auto slats or slots) F-4 it was so bad at high angles of attack we used the rudder only for roll control. We would practice confidence maneuver "rudder rolls" at 200kts. Aileron imput could lead to the a/c going out of control.
Damn!
 

shdw

Well-Known Member
How much overbanking tendency do you have though?
Though I have no data to quote, I'd say very little between ~15 and ~50 degree banks in coordinated flight. I can say, however, that this range will vary from aircraft to aircraft.

Roll stability in a coordinated turn is a spectrum. Lower bank angles are stable, you'll note the need to apply a very light stick force to hold a shallow bank turn. This will progress through neutral in the approximate range mentioned above, to unstable beyond some steeper bank angle.

An easy way to understand this from a pilots perspective is to realize stability is relayed to you through stick force. In this case, when you need to counter steer, you are now laterally unstable. No input required = Neutrally stable. Input force required to maintain = Positively stable.
 

TwoTwoLeft

o- - - - - - -l
The AOB has nothing to do with adverse yaw if no aileron deflection is being used to maintain the bank angle... It's how much deflection you use, (how fast) you want to get there that will tell you how much rudder you need.

Want to see this in action? Go practice some dutch rolls (the coordination exercise, not the stability issue)

Often the turn is treated as one blended action. There are actually three separate parts of the turn where coordination needs to be maintained. The roll into the turn (entry), the established turn, and the roll out of the turn (recovery).
 

TwoTwoLeft

o- - - - - - -l
Go fly tailwheel. It'll all be very clear.
That depends... Last time I was in a Pitts or an Extra I barely had to think about the rudder during a slow roll....

But in something from a Stearman to a Decathlon adverse yaw is how you get the slow roll going....
 

shdw

Well-Known Member
The AOB has nothing to do with adverse yaw if no aileron deflection is being used to maintain the bank angle...
No, but it does have to do with the over banking tendency in question. Although it might be worth noting that, in steeper banks, adverse yaw can be noticeable without any aileron input. This is due to the high side wing moving at a faster speed, having more parasitic (no lift) drag than the low side wing.

That said, the tradition definition for adverse yaw only refers to differences in induced (lift drag) experienced only when the aircraft is changing bank angle (rolling).
 

Cessnaflyer

Wooooooooooooooooooooooooooooooo
The AOB has nothing to do with adverse yaw if no aileron deflection is being used to maintain the bank angle... It's how much deflection you use, (how fast) you want to get there that will tell you how much rudder you need.

Want to see this in action? Go practice some dutch rolls (the coordination exercise, not the stability issue)

Often the turn is treated as one blended action. There are actually three separate parts of the turn where coordination needs to be maintained. The roll into the turn (entry), the established turn, and the roll out of the turn (recovery).
I was just throwing it out there for extra credit. :) I know AOB has nothing to do with adverse yaw.
 

A150K

Well-Known Member
The outside wing is also moving faster, so there is also more form and parasite drag. FAR more pronounced with high aspect ratio, long wingspan. Gliders have nasty adverse yaw.
Tell me about it. The nose of the Grob 103 I took my first glider flight in was swaying all over the place for the first 5 mintes or so.
 

USMCmech

Well-Known Member
Go fly tailwheel. It'll all be very clear.
Just to be clear, the fact that the little wheel is in the back has nothing to do at all with how much adverse yaw an airplane experiences. Now, tailwheel airplanes tend to be very simple and do typically demonstrate lots of adverse yaw, but the configuration of the wheels is not the cause.

A tailwheel airplane can have differential ailerons that reduce adverse yaw, just like a 172. A trike can have etreamly bad adverse yaw if the ailerons are designed poorly.
 

Fly_Unity

Well-Known Member
As a tailwheel instructor, I have done quite a few biannual's in the last few years for tailwheel pilots. One thing they all like to brag about is how good they are with rudder, when in fact they are not all that great.

Takeoffs and landings? yes, a tad better but thats about it. But man, they know how to brag how good they are.
 
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