FAA Flight Instructor Airplane (FIA)Aerodynamics and Principles of FlightMedium
A student asks why some light airplanes use Frise-type ailerons instead of conventional plain ailerons. Which explanation correctly describes how Frise ailerons help counteract adverse yaw?
- AThe up-deflected aileron's leading edge protrudes below the wing into the airflow, adding drag on that wing to help offset the extra induced drag from the down-deflected aileron
- BThe down-deflected aileron retracts flush with the wing to eliminate all induced drag on that side
- CFrise ailerons increase lift on the down-going wing without adding any drag on the up-going wing
- DBoth ailerons deflect upward simultaneously to spoil lift equally on each wing
Show answer & explanationAnswer & explanation
Correct answer: A. The up-deflected aileron's leading edge protrudes below the wing into the airflow, adding drag on that wing to help offset the extra induced drag from the down-deflected aileron
In a Frise aileron, the up-going aileron's leading edge projects into the airstream below the wing, creating additional parasite drag on the rising wing that helps balance the increased induced drag produced by the down-going aileron on the opposite wing, reducing adverse yaw.
Why the other options are wrong
- B. Wrong — the down aileron still increases induced drag on its wing; that drag is not eliminated
- C. Wrong — the whole design purpose is to intentionally add drag on the rising wing
- D. Wrong — the ailerons still move opposite each other (one up, one down) as in conventional ailerons
Frise Aileron
An aileron design where the up-going aileron's leading edge extends below the wing's lower surface into the airflow, creating extra drag to help offset adverse yaw.
- Differs from differential ailerons, which use unequal deflection angles
- Reduces, but does not fully eliminate, the need for rudder input
- Common on many light training and general aviation aircraft
Memory trick: Frise = 'Friction-adding' aileron that pokes into the wind to fight adverse yaw