# Visual Obstacle Marking Aids: Mobile Objects, Fixed Obstacles, and Marker Balls

> Review visual aids used to mark obstacles, including color requirements for mobile and fixed objects and marker-ball standards for overhead wires.

- **Subject:** 010 — Air Law
- **Section:** 010-09 — Aerodromes
- **Topic code:** 010-09-05
- **Last reviewed:** 2026-03-27
- **Author:** Pablo Asensio Martínez
- **HTML version:** https://pilotsyllabus.com/en/air-law/aerodromes/visual-aids-for-denoting-obstacles/

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## Mobile Objects
*   **Emergency vehicles:** Preferably **Red** or **Yellowish Green**.
*   **Service vehicles:** Preferably **Yellow**.
*   All mobile objects must be marked with colors or flags.

## Fixed Objects
*   **Lighting:**
    *   Low, medium, or high intensity obstacle lights.
    *   Must be visible from all angles in azimuth.
*   **Marking (Flags):**
    *   Flags to mark fixed objects must be **Orange** or a combination of **Orange and White** (or Red and White).

## Overhead Wires
*   **Marker Balls:**
    *   Must be displayed alternately in **White and Red** or **White and Orange**.
    *   Minimum diameter: 60 cm.
    *   Purpose: To make visible wires (high tension lines, river crossings) that pose a hazard to navigation.

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