When is the "reference datum" established?

The reference datum is established during the design phase of the aircraft. This is crucial because it serves as a fixed point from which all measurements of the aircraft’s center of gravity and weight distribution are taken. The location of the reference datum is selected based on design considerations and is specifically calculated to ensure that the aircraft can achieve optimal performance, stability, and safety.

Having a fixed reference datum allows for consistent weight and balance calculations throughout the aircraft's operational life. By defining this point during the design phase, engineers can create clear and precise weight and balance documentation that is essential for maintaining proper operational parameters. Once established, this reference is used consistently in subsequent weight and balance calculations, as well as maintenance and inspections, ensuring that the aircraft remains safe and within the designed operational limits.