Aerodynamic Degradation
Ice and Frost
Accretion of ice alters the shape and roughness of the aerofoil.
- Leading Edge Ice: Most critical. Changes the effective camber shape.
- Frost: Roughness turns laminar flow into turbulent flow prematurely, thickening boundary layer.
Effects
- Lift Reduced: $C_{L_{max}}$ can decrease by 30% or more.
- Drag Increased: Parasite drag increases significantly (40%+).
- Stall Speed Increased: Since $V_{stall} \propto \frac{1}{\sqrt{C_{L_{max}}}}$.
- If $C_{L_{max}}$ drops, $V_{stall}$ goes UP.
- Stalling Angle Reduced: The wing stalls at a lower angle of attack.
Conclusion
"Clean Aircraft Concept": Never take off with contamination. Even a thin layer of frost ("sandpaper" texture) can impose a heavy performance penalty.