A student pilot rolls into a bank without applying rudder, and the airplane's wings return toward level flight on their own. A CFI explains this results from dihedral effect. What is the underlying aerodynamic cause?
- AThe vertical stabilizer directly generates a rolling moment that levels the wings
- BThe higher wing produces more lift because it is exposed to a greater relative wind velocity in the slip
- CRudder deflection is automatically commanded by the flight control system to correct the bank
- DThe resulting sideslip causes the lower wing to meet the relative wind at a greater angle of attack, producing more lift and rolling the airplane back toward wings-level
Show answer & explanationAnswer & explanation
Correct answer: D. The resulting sideslip causes the lower wing to meet the relative wind at a greater angle of attack, producing more lift and rolling the airplane back toward wings-level
When the airplane banks, it begins to sideslip toward the low wing. With dihedral, the low (leading) wing meets the sideslip's relative wind at a higher effective angle of attack than the high wing, generating more lift on the low wing and rolling the airplane back toward wings-level without any pilot or rudder input.
Why the other options are wrong
- A. The vertical stabilizer contributes to directional, not lateral (rolling), stability.
- B. Reverses which wing experiences the increased angle of attack.
- C. There is no automatic rudder input; this is a passive aerodynamic effect.
Dihedral Effect
The tendency of an airplane to roll back toward wings-level after a sideslip develops, caused by an increased angle of attack (and lift) on the lower wing due to wing dihedral.
- Triggered by sideslip following a bank
- Low wing gets higher effective AOA and more lift
- Provides positive lateral (roll) stability
Memory trick: A 'V' shaped wing scoops more air with its low side, pushing it back up.