FAA Airline Transport Pilot (ATM)Transport Aerodynamics and High-Altitude OperationsMedium
During an approach with visible ice accumulation on the leading edge of the main wing (wing anti-ice system inoperative), what is the primary aerodynamic effect on the wing's stall characteristics?
- AIce accumulation improves boundary layer energy on the wing, delaying flow separation
- BClmax decreases and the stall angle of attack decreases, increasing stall speed and reducing stall margin
- CStall angle of attack and Clmax both increase, decreasing the stall speed
- DOnly drag increases; stall speed is essentially unaffected since ice does not significantly change wing shape
Show answer & explanationAnswer & explanation
Correct answer: B. Clmax decreases and the stall angle of attack decreases, increasing stall speed and reducing stall margin
Leading-edge ice disrupts the smooth airflow and effectively degrades the airfoil shape, causing earlier boundary layer separation. This reduces the maximum lift coefficient (Clmax) and the angle of attack at which stall occurs, which raises the stall speed and reduces the margin between approach speed and stall speed.
Why the other options are wrong
- A. Ice roughens/disrupts the boundary layer, promoting earlier separation, not delaying it.
- C. Ice degrades, rather than improves, lift characteristics, so this is the opposite effect.
- D. Ice significantly disrupts airflow and does affect stall speed, not just drag.
Wing Leading-Edge Icing Effect
Ice contamination on the wing leading edge disrupts smooth airflow, reducing Clmax and stall angle of attack, which increases stall speed and reduces stall margin.
- Ice roughens the leading edge, promoting early boundary layer separation
- Clmax decreases with ice contamination
- Stall speed increases and buffet/stall warning margins are reduced
Memory trick: Ice roughs up the wing's 'race track,' so it trips and stalls sooner.