Which term describes a control surface rigged so that the up aileron moves more than the down aileron?

• A. Differential ailerons
• B. Direction stability
• C. Differential pressure
• D. DUATS

Answer: (A)

Differential ailerons describe a arrangement where the upward-deflecting aileron travels farther than the downward-deflecting one. This asymmetry reduces adverse yaw during a roll. When you roll, the wing with the downward-deflected aileron would normally produce more drag and yaw the nose opposite to the turn. By making the upgoing aileron move farther, the drag and lift changes on the rising wing are limited more than on the falling wing, so the nose tends to follow the direction of the roll instead of opposing it. This gives quicker, smoother rolls with coordinated flight. The other terms refer to stability concepts, not to how the ailerons are rigged; directional stability is about yaw behavior of the whole aircraft, differential pressure isn’t the standard term here, and DUATS is just a planning tool.