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

1. Lift Reduced: $C_{L_{max}}$ can decrease by 30% or more.
2. Drag Increased: Parasite drag increases significantly (40%+).
3. Stall Speed Increased: Since $V_{stall} \propto \frac{1}{\sqrt{C_{L_{max}}}}$.
   • If $C_{L_{max}}$ drops, $V_{stall}$ goes UP.
4. 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.