What is included in useful load?

Useful load refers to the total weight that an aircraft can carry in addition to its basic empty weight. This includes the weight of passengers, cargo, usable fuel, and drainable oil. Understanding useful load is essential for ensuring that the aircraft operates within its weight limits for safety and performance.

The inclusion of usable fuel is particularly important, as it impacts the distance and duration the aircraft can travel. The weight of drainable oil is relevant as it can contribute to the overall weight management, although in practical terms, the oil weight is often less than the other components.

In contrast, the weight of the aircraft structure is part of the basic empty weight and is not included in useful load. Similarly, only counting passengers or fuel ignores significant components that contribute to the overall load capacity of the aircraft. Thus, the correct choice encompasses all relevant factors that make up useful load.