# Engine Vibration Monitoring (EVM): Accelerometers, Filtering, and Alerts

> Understand gas-turbine vibration monitoring using accelerometers, signal filtering, and cockpit indication to detect imbalance and bearing-related faults early.

- **Subject:** 022 — Instrumentation
- **Section:** 022-01 — Sensors and Instruments
- **Topic code:** 022-01-09
- **Last reviewed:** 2026-04-01
- **Author:** Pablo Asensio Martínez
- **HTML version:** https://pilotsyllabus.com/en/instrumentation/sensors-and-instruments/engine-vibration-monitoring/

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Gas turbine (jet) engines operate very smoothly. Therefore, any detectable vibration is a critical warning sign of potential mechanical failure, such as rotor imbalance or bearing wear.

## Monitoring System
An **Engine Vibration Monitoring (EVM)** system is installed to detect and quantify these vibrations before damage occurs.
*   **Sensors:** Uses **accelerometers** (often piezo-electric) to measure radial and transverse vibrations.
*   **Signal Processing:** The raw signal is **filtered** to remove normal engine operational frequencies/noise, isolating only those frequencies indicative of malfunction.
*   **Indication:** The filtered signal is amplified and displayed in the cockpit. The display typically shows a **unit-less value** (relative scale) rather than a specific physical unit.

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