Which components are included in the useful load of an aircraft?

The useful load of an aircraft is a crucial concept in weight and balance calculations, representing the total weight that an aircraft can safely carry beyond its empty weight. This includes all the payload that contributes to the aircraft's operation and functionality.

The correct answer highlights that the useful load is comprised of usable fuel, passengers, and crew. Usable fuel accounts for the weight of the fuel that can be burned during flight, which directly affects how much cargo and how many passengers the aircraft can safely transport. Passengers contribute to the overall load, as every person's weight adds to the total weight the aircraft must lift. Crew members are also included in this calculation since they are essential for flying and operating the aircraft.

In contrast, other options focus on elements that do not accurately represent the useful load. For example, empty weight and balance calculations signify the total weight of the aircraft when it's not loaded, which is not included in the useful load itself. Maximum takeoff weight and operational limits refer to the maximum weight an aircraft is allowed to take off with, encompassing both useful load and empty weight, further confirming why the selected response accurately characterizes the components of useful load.