FAA Airline Transport Pilot (ATM)Transport Aerodynamics and High-Altitude OperationsMedium
A pilot initiates a right roll using ailerons alone, without rudder input. Momentarily, the nose yaws slightly to the left before the aircraft establishes the turn to the right. What causes this initial yaw?
- AThe yaw damper automatically deflects the rudder opposite the intended turn
- BIncreased dihedral effect as the wing enters a bank produces a yawing moment
- CGyroscopic precession from the rotating engine fans causes the nose to yaw
- DThe down-going aileron on the right wing increases lift and induced drag on that wing, yawing the nose opposite the roll direction
Show answer & explanationAnswer & explanation
Correct answer: D. The down-going aileron on the right wing increases lift and induced drag on that wing, yawing the nose opposite the roll direction
Adverse yaw occurs because the down-going aileron (on the wing rising into the roll) increases both lift and induced drag on that wing compared to the up-going aileron on the opposite wing, creating a yawing moment opposite the direction of roll. Rudder coordination or differential/spoiler-aided aileron design counteracts this.
Why the other options are wrong
- A. The yaw damper primarily addresses Dutch roll oscillations, not adverse yaw from aileron deflection.
- B. Dihedral effect responds to sideslip, it does not initiate the yaw itself.
- C. Gyroscopic precession from engines is not a significant factor in adverse yaw during aileron roll.
Adverse Yaw
A yawing tendency opposite to the direction of roll, caused by the down-going aileron producing more lift and induced drag than the up-going aileron on the opposite wing.
- Caused by differential induced drag from aileron deflection
- Counteracted by rudder input or differential ailerons/spoilers
- More pronounced at low airspeed and high angle of attack
Memory trick: Down aileron drags its wing back, nose swings the wrong way