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6 Aerodynamic Facts About Ailerons Every Pilot Should Know

Ailerons do a lot more than help airplanes turn. Here are some important aerodynamic principles every pilot should know...

1) Ailerons Cause Adverse Yaw

When you roll your airplane to the right, your right aileron goes up, and your left aileron goes down. The aileron in the upward position (the right aileron in this example) creates less lift and less drag than the aileron that is lowered. The aileron angled downward (the left aileron in this example) produces more drag and more lift, initially yawing the airplane in the opposite direction of your roll.

2) How Differential Ailerons Counter Adverse Yaw

One aileron is raised a greater distance than the other aileron is lowered. The extra upward aileron movement produces more drag change than an increase in AOA on the downward aileron. This produces an increase in drag on the descending wing, which reduces adverse yaw.

3) How Frise Ailerons Counter Adverse Yaw

The aileron being raised pivots on an offset hinge. The leading edge of the aileron is now pushed into the airflow, creating drag and reducing adverse yaw. In this case, frise ailerons are using form drag to counter induced drag.

4) Using Ailerons During A Stall Can Cause The Wing To Drop

As you deflect your ailerons, you change the angle-of-attack (AOA) on each of your wingtips. Your left wing is now flying at a lower AOA, and your right wing is flying at a higher AOA. If you add enough aileron deflection, you can push the right wing over the critical AOA, abruptly stalling the entire wing, and causing your airplane to suddenly roll to the right.

5) Ailerons Create Induced Drag

Just like flaps, when you lower the aileron, you change the chord line of the wing, creating a higher angle of attack (AOA). As AOA and lift increase, induced drag also increases, because the drag created as an aileron is lowered is induced drag.

6) Neutralize Ailerons During A Spin

In a spin, each wing is stalled. But, the low wing is at a higher angle of attack (and so is more stalled) than the high wing. Bringing the ailerons to neutral helps your wings reach the same angle of attack - decreasing the pitching and rolling moments.

If you try to raise the low wing using aileron, it will stall even more, tightening the spin. Not good.

How about rolling into the spin? Won't that decrease the angle of attack on the inside wing? Bad idea. If you do that, you're increasing the angle of attack on the outside wing - which is still stalled. When the aircraft starts to recover, the increased angle of attack on the outside wing can cause the aircraft to snap into a spin in the opposite direction. That's possibly a neat airshow maneuver, but not something to try in an inadvertent spin.

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What else should pilots know about ailerons? Tell us in the comments below.

Swayne Martin

Swayne is an editor at Boldmethod, certified flight instructor, and an Embraer 145 First Officer for a regional airline. He graduated as an aviation major from the University of North Dakota in 2018, holds a PIC Type Rating for Cessna Citation Jets (CE-525), and is a former pilot for Mokulele Airlines. He's the author of articles, quizzes and lists on Boldmethod every week. You can reach Swayne at swayne@boldmethod.com, and follow his flying adventures on his YouTube Channel.

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