What is meant by Zero Fuel Mass?

Zero Fuel Mass refers to the total mass of the aircraft without usable fuel. This includes the aircraft itself, its structure, any fixed ballast, crew, passengers, and cargo, but excludes any fuel that can be used for flight.

Understanding Zero Fuel Mass is crucial in mass and balance calculations, as it forms the basis for weight distribution and helps ensure that the aircraft operates within safety limits. By knowing the Zero Fuel Mass, operators can effectively determine how much fuel can be loaded while maintaining safe center of gravity limits and overall weight restrictions.

The other choices relate to different aspects of aircraft mass. For example, the mass without passengers does not account for the weight of cargo and crew. The total weight at takeoff includes all fuel, while the mass when fully loaded would also encompass all operational fuel, which is not relevant when discussing Zero Fuel Mass specifically.