# Aerodynamic Degradation

> Effects of ice, frost, and contamination on aerodynamic performance.

- **Subject:** 081 — Principles of Flight
- **Section:** 081-01 — Subsonic Aerodynamics
- **Topic code:** 081-01-12
- **Last reviewed:** 2026-04-01
- **Author:** Pablo Asensio Martínez
- **HTML version:** https://pilotsyllabus.com/en/principles-of-flight/subsonic-aerodynamics/aerodynamic-degradation/

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## 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.

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Free study notes from pilotsyllabus.com. Not a substitute for training at an approved ATO.