# Flight Data Recorder (FDR): Mandatory Parameters, Event Marks, and Use

> Study FDR recording requirements, mandatory flight-parameter capture, automatic start/stop logic, and event-mark usage for investigation workflows.

- **Subject:** 022 — Instrumentation
- **Section:** 022-14 — Maintenance, Monitoring and Recording Systems
- **Topic code:** 022-14-02
- **Last reviewed:** 2026-03-27
- **Author:** Pablo Asensio Martínez
- **HTML version:** https://pilotsyllabus.com/en/instrumentation/maintenance-monitoring-and-recording-systems/flight-data-recorder-fdr/

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The **FDR** records technical flight parameters to assist in accident analysis and troubleshooting. It is typically housed in a crash-survivable container (shockproof, fireproof, orange colored) fitted with an **Underwater Locating Device (ULD)**.

## Recording Requirement
The type and number of parameters recorded are determined by:
1.  **Recording Capacity** of the system.
2.  **Applicable Operational Requirements** (Regulations).

## Mandatory Parameters
Common parameters include (but are not limited to):
*   Time / Relative Time Count.
*   Pressure Altitude and Airspeed.
*   Attitude (Pitch and Roll).
*   Heading.
*   Normal Acceleration (Vertical G).
*   Thrust/Power on each engine and Lever positions.
*   Configuration (Flaps, Slats, Spoilers, Gear).
*   Autopilot/Flight Director modes.

## Operation
*   **Automatic Activation**:
    *   **Start**: Prior to the airplane being capable of moving under its own power (often on engine start or power-up).
    *   **Stop**: After the airplane is incapable of moving under its own power (engine shutdown).
*   **Event Button**: A button in the cockpit that allows the crew to place a **Time Mark** in the data stream. This highlights a specific event (e.g., a temporary system failure or turbulence) to aid investigators in locating the relevant data later.

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