# Aerodrome General Concepts: Reference Code and Runway Surface Conditions

> Learn essential aerodrome concepts, including reference code elements and standardized runway surface condition terminology for operational safety.

- **Subject:** 010 — Air Law
- **Section:** 010-09 — Aerodromes
- **Topic code:** 010-09-01
- **Last reviewed:** 2026-03-27
- **Author:** Pablo Asensio Martínez
- **HTML version:** https://pilotsyllabus.com/en/air-law/aerodromes/general/

---

## Aerodrome Reference Code
The **Aerodrome Reference Code** is used for planning purposes and determines whether the aerodrome dimensions are adequate for a specific type of aircraft. It consists of two elements:

1.  **Element 1 (Number):** Based on the **Aeroplane Reference Field Length**.
    *   Example: **4** indicates a field length of 1800 m or more.
2.  **Element 2 (Letter):** Based on the **Wingspan** or the Outer Main Gear Wheel Span, whichever is more demanding.
    *   Example: **E** indicates a wingspan between 52 m and 64.9 m.

> **Important:** The number (Element 1) refers to the field length, and the letter (Element 2) refers primarily to the **wingspan**.

*   **Note:** The determination of the reference field length is solely for selecting the code and does not influence the actual runway length provided.

## Runway Surface Condition
Specific terms are used to describe the state of the runway surface:
*   **Dry:** Free of visible contaminants.
*   **Wet:** The surface is soaked but there is no standing water.
*   **Standing Water:** Depth exceeding 3 mm.
*   **Slush:** Water-saturated snow which with a heel-and-toe slap-down motion will be displaced with a splatter; specific gravity 0.5 to 0.8.
*   **Compacted Snow:** Solid mass which resists further compression.
*   **Wet Ice:** Ice with water on top of it or ice that is melting (very poor braking).

---

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