# HUD, EVS, and SVS: Vision Technologies, Minima, and Limitations

> Compare HUD, EVS, and SVS capabilities in modern cockpits, including visibility benefits, operational minima effects, and data-source limitations.

- **Subject:** 022 — Instrumentation
- **Section:** 022-13 — Integrated Instruments – Electronic Displays
- **Topic code:** 022-13-07
- **Last reviewed:** 2026-03-27
- **Author:** Pablo Asensio Martínez
- **HTML version:** https://pilotsyllabus.com/en/instrumentation/integrated-instruments-electronic-displays/head-up-display-hud-synthetic-vision-system-svs-and-enhanced-visual-system-evs/

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Advanced display technologies are used to enhance pilot situational awareness and lower operational minimums.

## Head-Up Display (HUD)
A transparent screen (Combiner) that projects critical flight data into the pilot's forward field of view.
*   **Content**: Replicates **PFD** data (Attitude, Speed, Altitude, FMA, Flight Path Vector). It does **not** typically show Engine data or System synoptics.
*   **Benefits**:
    *   **Situational Awareness**: Pilot keeps "eyes out" while monitoring instruments.
    *   **Lower Minima**: Allows for lower Take-off and Landing visibility minimums (e.g., manual CAT III approaches).
    *   **Smoother Control**: Improves flight path tracking.
*   **Crosswind Declutter**: A mode that removes outer tapes (Speed/Alt) to prevent them from obscuring the runway view during high drift-angle landings.

## Enhanced Vision System (EVS)
Uses **real-time external sensors** (Infrared/IR Cameras, Millimeter Wave Radar) to "see" through darkness or weather.
*   **Principle**: Detects thermal differences (e.g., hot runway lights vs cold ground).
*   **Display**: Projected on the PFD or Video-capable HUD.
*   **Benefit**: Can **lower landing minima** because it provides a real visual reference of the runway environment when the naked eye cannot see it yet.

## Synthetic Vision System (SVS)
Generates a **Virtual 3D image** of the outside world using an onboard **Database** (Terrain, Obstacles, Airports) and GPS position.
*   **Principle**: "Flight Simulator" style view on the PFD background.
*   **Limitation**: It is a **Synthetic** (Computer Generated) image, **not** a real-time sensor view. It depends entirely on the accuracy of the Navigation System and Database.
*   **Minima**: Does **NOT** lower landing minima (unlike EVS) because it does not confirm the actual external visibility or runway blockage.
*   **Benefit**: Excellent Terrain Awareness and Situational Awareness in IMC.

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