Adverse yaw is the tendency of an airplane's nose to yaw opposite the direction of a roll. It matters because a pilot who uses ailerons alone may start a left bank while the nose initially points right. This makes turns less coordinated, increases drag, and can make the airplane feel sloppy or unstable.
Understanding adverse yaw helps students see why roll control and yaw control must work together.
Key Facts
- Adverse yaw is yaw opposite the intended roll direction.
- In a left roll, the left aileron goes up and the right aileron goes down.
- The down aileron increases camber, lift, and drag on that wing.
- Yawing moment can be described by τ = rF, where a drag force acting far from the centerline creates torque.
- Lift and drag depend on dynamic pressure: L = qSCL and D = qSCD.
- Coordinated turns use aileron to bank and rudder to counter adverse yaw.
Vocabulary
- Adverse yaw
- Adverse yaw is the yawing motion of an airplane's nose opposite the direction of an aileron commanded roll.
- Aileron
- An aileron is a hinged control surface on the wing that changes lift to roll the airplane.
- Rudder
- The rudder is a hinged control surface on the vertical tail that controls yaw.
- Yaw
- Yaw is rotation of an aircraft's nose left or right about its vertical axis.
- Coordinated turn
- A coordinated turn is a turn in which aileron, rudder, and elevator are balanced so the airplane does not skid or slip sideways.
Common Mistakes to Avoid
- Thinking the raised aileron causes the most drag is wrong because the lowered aileron usually increases lift and induced drag more strongly.
- Using ailerons alone to start a turn is wrong because the airplane may roll one way while the nose yaws the other way.
- Confusing roll with yaw is wrong because roll tilts the wings around the longitudinal axis, while yaw swings the nose around the vertical axis.
- Adding too much rudder is wrong because overcorrection can create a skid, increase drag, and reduce control smoothness.
Practice Questions
- 1 A pilot commands a left roll. Which aileron goes up, which aileron goes down, and which direction does adverse yaw initially point the nose?
- 2 A right wing produces an extra 120 N of drag during a left roll, and the wing is 4.0 m from the aircraft centerline. What yawing torque does this drag create about the centerline using τ = rF?
- 3 Explain why differential ailerons, which make the up aileron move farther than the down aileron, can reduce adverse yaw.