In weight and balance calculations, the amount of fuel used for computing the empty weight and the corresponding CG is:

• A. Usable Fuel
• B. Unusable Fuel
• C. Both Usable and Unusable
• D. Neither Usable Nor Unusable

Answer: (B)

The concept being tested is how fixed, non-consumable mass affects the aircraft’s baseline weight and balance. When you determine the empty weight and its center of gravity, you include the fuel that cannot be drained from the tanks—unusable fuel. This fuel is always aboard and acts as a constant mass at a fixed position, so its weight contributes to the empty weight and its moment. If you were to use usable fuel (which can be burned off) to compute the empty weight, you’d be counting fuel that won’t be onboard for the entire flight, which would skew the baseline weight and CG.

Usable fuel, by contrast, is treated separately because its mass changes with fuel burn and is part of operating weight planning rather than the fixed empty weight. Including unusable fuel in the empty weight ensures the CG calculations reflect the aircraft’s true, constant mass distribution while flying.