FAA Sport Pilot Airplane (SPA)Aircraft Performance and SystemsMedium
An airplane's wings are mounted with a slight upward angle from the fuselage to the wingtips, known as dihedral. If the airplane rolls into a sideslip to the left due to a wind gust, the dihedral effect will tend to
- Acause the nose to pitch down sharply
- Bproduce a rolling moment back to the right, toward wings-level
- Cincrease the sideslip and roll further left
- Dhave no effect on roll, only on yaw
Show answer & explanationAnswer & explanation
Correct answer: B. produce a rolling moment back to the right, toward wings-level
When an airplane sideslips to the left, the relative wind strikes the left (lower) wing at a greater angle of attack because of the dihedral, generating more lift on that wing. This produces a restoring rolling moment back toward wings-level flight, which is the basis of lateral static stability provided by dihedral.
Why the other options are wrong
- A. Dihedral affects roll (lateral) stability, not pitch.
- C. This would describe negative stability, the opposite of what dihedral provides.
- D. Dihedral directly affects roll, not just yaw; it is a key lateral stability design feature.
Dihedral Effect
An upward angle of the wings from root to tip that provides lateral (roll) stability by generating a restoring rolling moment during a sideslip.
- Lower wing in a sideslip gets a higher effective angle of attack
- Produces more lift on the lower wing, rolling airplane level
- Excessive dihedral can cause undesirable 'Dutch roll' tendencies
- Works together with wing sweep to provide lateral stability
Memory trick: Dihedral = wings shaped like a shallow V, always self-leveling