# Contaminated Runways

> Operations on runways contaminated by water, slush, snow, or ice.

- **Subject:** 070 — Operational Procedures
- **Section:** 071-02 — Special Operational Procedures and Hazards (General Aspects)
- **Topic code:** 071-02-13
- **Last reviewed:** 2026-04-01
- **Author:** Pablo Asensio Martínez
- **HTML version:** https://pilotsyllabus.com/en/operational-procedures/special-operational-procedures-and-hazards-general-aspects/contaminated-runways/

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## Definition

![Snow covered runway](https://upload.wikimedia.org/wikipedia/commons/6/64/Snow_covered_Schipol_airport_runway_1.JPG)

A runway is considered contaminated when more than **25%** of the surface area is covered by:
*   Surface water > 3mm deep.
*   Slush, loose snow.
*   Compacted snow or ice.

## Hazards
*   **Braking Action**: Reduces friction, increasing Stopping Distance (ASDA/LDA).
*   **Aquaplaning**: Loss of continuous contact between tire and ground.
    *   **Dynamic**: At high speed on standing water (Formula: $9 \times \sqrt{P_{psi}}$).
    *   **Viscous**: On ice/rubber deposits (low speed).
    *   **Reverted Rubber**: Locked wheel melts tire rubber creating steam seal.
*   **Drag**: Slush/water spray creates impingement drag on landing gear/airframe, retarding acceleration during take-off.
*   **Directional Control**: Reduced effectiveness of nosewheel steering.

## Reporting
*   **GRF (Global Reporting Format)**: New ICAO standard. Uses Runway Condition Code (RWYCC) from 0 (Nil) to 6 (Dry).
*   **SNOWTAM**: Special NOTAM notifying presence of hazardous conditions on movement area.

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