Datum

A datum is an imaginary vertical plane or reference line established by the aircraft manufacturer from which all horizontal distances are measured for balance purposes. All stations and arms are determined relative to this fixed reference point. The datum location varies by aircraft type and may be positioned at the nose, the firewall, or the leading edge of the wing.

Key Points

• •The datum location varies by aircraft type and may be at the nose, firewall, or leading edge of the wing.
• •The datum remains a fixed reference for a specific aircraft model and does not change.
• •All arms are defined as positive or negative based on their position relative to the datum.
• •The datum is essential for defining arms and calculating moments during weight and balance calculations.

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