What constitutes the variable load in an aircraft?

The variable load in an aircraft refers to the weight that can change with each flight. This includes items that are not permanently fixed to the aircraft structure. In this context, the option stating that all removable equipment needed for the flight constitutes the variable load is correct because it encompasses a range of components, including passengers, cargo, and their baggage, as well as fuel. Each of these elements can fluctuate between flights, affecting the total weight and balance of the aircraft, which is crucial for safe operation.

Fuel is an essential part of the variable load as it can significantly vary based on the length of the flight and fuel requirements. The removal of equipment for a specific flight also impacts the overall mass. Thus, the emphasis on removable equipment highlights its direct importance in calculating mass and balance since it is not fixed and varies with each flight configuration.

The other options, while related to various loads, either describe fixed components or specific parts of the load that do not adequately capture the variability inherent in operational situations for each flight.