# Mass and Balance Documentation: Required Content and Compliance Use

> Learn required aircraft mass-and-balance documentation, including datum definition, CG envelope interpretation, weighing reports, and equipment-list control.

- **Subject:** 031 — Mass and Balance
- **Section:** 031-04 — Mass and Balance Details of Aircraft
- **Topic code:** 031-04-01
- **Last reviewed:** 2026-04-01
- **Author:** Pablo Asensio Martínez
- **HTML version:** https://pilotsyllabus.com/en/mass-and-balance/mass-and-balance-details-of-aircraft/contents-of-mass-and-balance-documentation/

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## Required Documentation

Every aircraft must have a **Mass and Balance Manual** (or section in the Flight Manual/POH) approved by the authority. This document contains:

1.  **Datum Definition**: The reference line from which all longitudinal distances (arms) are measured.
2.  **CG Envelope**: A graph or table showing the allowable range of CG positions for various masses.
3.  **Maximum Mass Limits**: MTOM, MLM, MZFM.
4.  **Weighing Report**: The most recent weighing data, establishing the aircraft's Basic Empty Mass (BEM) and its CG position.
5.  **Equipment List**: A list of installed equipment included in the BEM.

## CG Envelope

The allowable CG range typically changes with mass. The documentation provides a **CG Envelope** diagram with:
*   **X-axis**: Centre of Gravity location (inches, meters, or % MAC).
*   **Y-axis**: Aircraft Mass (kg or lbs).

The pilot must verify that the calculated mass and CG for the flight fall *within* the boundaries of this envelope.

## Weighing Schedule

Commercial aircraft must be re-weighed periodically:
*   **Individual Aircraft**: Every 4 years.
*   **Fleet Mass**: If using fleet values, sampling weighing is required.
*   **Modifications**: After major modifications or repairs that significantly affect mass or CG.

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