Adverse Yaw - Dont Understand
 

From youtube:
alieron deflect down:
effective increase in camber
increase in effective aoa
increase in lift

alieron deflect up:
effective decrease in camber
decrease in effective aoa
decrease in lift

Q1 Can anyone explain to me why if the alieron is deflected up, it will cause decrease in lift?
Airplane wings are curved at the top to produce more lift.
Am I right to say that?
Correct me if I wrong.

Q2 There is more drag generated by downward alieron.
Can anyone explain why there is MORE drag in a downward alieron compared to an upward alieron?

I think if you invested in a good PPL book you would get the answers you seem to need.

You have answered Q1 yourself - wings are curved at the top to get more of a lift reaction, but they won't do that with a decrease in curvature.

Read it but did not understand.

Based on the bernouli principle, the upper wing is curved which leads to more air molecules going across compared to bottom wing.This is higher velocity and lower pressure.

If the alieron is deflected up, wouldnt it lead to higher velocity and lower pressure just like a curved wingtip? --< wrong

Don’t get to hung up on the curvature.
To try and figure this out imagine a symmetrical wing.
Symmetrical wing (flat board) at zero angle of attack creates zero lift.
Now angle the back end down, you’ve created camber aka curvature > “positive lift”
Now angle the back end up, you’ve created camber aka curvature but in the other direction > “negative” lift which is simply lift in the other direction.

Another way to see this is by looking at the rudder from the top.
Deflection left creates a lift vector that pushes the tail right.
Deflection right creates a lift vector that pushes the tail left.

Not a perfect explanation but it works.

Fold some paper to make a wing shape and experiment. You’ll see the up going aileron makes the upper surface of the wing less curved.
The increase in drag from the wing with the down going aileron is due to induced drag - basically the drag caused by the lift. The downward deflected aileron has increased the lift. Drag is a by-product of lift, so more lift means more drag.
This isn’t a precise definition so anyone please correct me if required.
In a long winged, slow flying aircraft like a glider, simply moving the stick to one side will create so much drag on that side that the nose will swing in the opposite direction, (this is adverse yaw.) so rudder input is needed to prevent this.

I got it a little bit.
When the alieron deflects down, where is the chrod line and where is the relative wind?
I have a hard time visualising it.

The chord line goes from the leading edge to the trailing edge so if the aileron goes down, so does the chord line against the relative airflow. The bit of the chord line at the leading edge stays where it is, but the other end stays with the back edge of the aileron.

The big thing to get into your head is that (contrary to popular belief) you are not sucked into the air, you are pushed up from underneath due to the line of least resistance created by the lower pressure above the wing.

It is the difference in thatic pressure above and below the wing that is directly involved with flight, but we cannot affect it directly. Instead, we change the dynamic pressure over the upper surface of the wings, especially in the first quarter, where pressure is decreased the most relative to the lower surface to create the change we need. No movement (of an aircraft) would be necessary were it not for the need to reduce the static pressure on the upper surface of its wings by changing the dynamic pressure.

An ailreon deflected upwards creates a lower angle of attack and therefore less of a lift reaction, and vice versa.

Dont understand why An ailreon deflected upwards creates a lower angle of attack while an alieron deflected downwards creates a higher AOA.
Arent they supposed to be symmetrical?

Symmetry in lift generated by aileron
 

I'm not a pilot, just an enthusiast and a long-time lurker, so please call me out if I'm totally off the wall on this. This is how I handle the symmetry issue:

1. Drag is proportional to net lift, so if lift = x, then drag = px (p is some positive number)
2. In straight flight (no aileron deflection), lift = x and drag = px on both wings
3. An aileron moving generates lift of y in the opposite direction.

Then

4. An aileron moving down generates lift of y. This adds to the lift of the rest of the wing for a total lift of (x + y) and a total drag of p(x + y); therefore drag increases on that side.
5. An aileron moving up generates lift of (-y). This "adds" to the lift of the rest of the wing for a total lift of (x - y), and a total drag of p(x - y); therefore drag decreases on that side.
6. Since there is more drag on the aileron-down side than the aileron-up side, the airplane will want to yaw towards the aileron-down side, hence adverse yaw that must be compensated for with rudder movement.

Is this more or less accurate?

You are talking about the wing as a whole, not just the aileron. Although they are symmetrical, the wing itself isn't when they are deflected either way.

I guess I will stick to your explanation.

Left deflection in rudder will cause tail to be pushed right and the plane to go left. Am I correct?

I am thinking that the alieron deflection causes air molecules to be blocked leading to reduced velocity and increased lift. So a downward deflected alieron will generate positive lift

Ailerons

The picture speaks a thousand words

Yaw
 

Hi,

I hope you’re doing well.