# Airborne Weather Radar: Operation and Limitations

> Understand airborne weather radar operation, limitations, and tactical use.

- **Subject:** 062 — Radio Navigation
- **Section:** 062-03 — Radar
- **Topic code:** 062-03-03
- **Last reviewed:** 2026-04-01
- **Author:** Pablo Asensio Martínez
- **HTML version:** https://pilotsyllabus.com/en/radio-navigation/radar/airborne-weather-radar/

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The **Airborne Weather Radar (AWR)** is a primary radar system designed to detect precipitation and allow the crew to avoid adverse weather conditions.

## Operating Principles

*   **Frequency:** Operates in the **SHF** band (Super High Frequency), typically at **9.375 GHz** (X-Band).
*   **Wavelength:** Approximately **3.2 cm**. This wavelength is ideal for reflecting off large water droplets and wet hail, while ignoring very small particles like fog or drizzle.
*   **Reflectivity:**
    *   **Wet hail and large drops:** High reflectivity (Strong echoes).
    *   **Dry snow and ice crystals:** Low reflectivity (Weak or no echoes).
    *   **Display Colors:**
        *   **Green:** Light precipitation.
        *   **Yellow/Amber:** Moderate precipitation.
        *   **Red:** Heavy precipitation.
        *   **Magenta:** Extreme precipitation or severe turbulence.

## Functions and Modes

### Weather Mode
Uses a narrow conical beam (**Pencil Beam**, approx 3-5° wide) to scan ahead of the aircraft.
*   **Turbulence:** Modern radars (Doppler) can detect turbulence by measuring the frequency shift (Doppler shift) of moving raindrops. **Only works if there is precipitation** (wet turbulence); it does not detect Clear Air Turbulence (CAT).
*   **Windshear:** Uses the Doppler effect to detect wind shear (microbursts) ahead of the aircraft, generally at low altitudes.

### Mapping Mode
Uses a fan-shaped beam (**Cosecant Squared Beam**) or tilts the conical beam downwards to obtain terrain echoes.
*   Useful for basic navigation (coastlines, islands, mountains) when other systems fail.
*   Distinguishes land (echoes) from water (no echoes).

## Tilt Management

The pilot must manually adjust the **Tilt** to scan different levels of the atmosphere, although modern systems have automatic functions (*Auto-tilt*).

*   **Takeoff/Climb:** **High** tilt (+4° to +15°) to see weather in the climb path and avoid nearby ground echoes.
*   **Cruise:** **Low** tilt (0° to -1°) to scan the most reflective part of storms (middle/lower levels where liquid water exists).
    *   *Danger:* At high altitude, if the tilt is too high, the radar may scan only the storm top (ice crystals) and show nothing, hiding severe activity below (**Over-scanning**).
*   **Descent:** Tilt slightly **up** (+4° to +5°) to avoid ground clutter as the aircraft descends.

## Limitations and Hazards

### Attenuation (Shadowing)
Very intense precipitation can absorb or reflect all radar energy, preventing detection of what lies behind.
*   Appears as a black "shadow" behind an intense red echo.
*   **Rule:** Never fly into a radar shadow behind a storm; it is unknown what is there (possibly another severe storm).

### Radiation Hazard
The radar emits high-energy microwave radiation. It should not be operated on the ground when personnel are near the radome or during refueling.

### Storm Avoidance
*   Deviate at least **20 NM** laterally from intense echoes.
*   Preferably deviate to the **upwind** side to avoid hail and turbulence that the wind may carry outside the cloud.
*   Do not attempt to fly under a storm (danger of microbursts and hail).

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