What is defined as the 'gross weight' of an aircraft?

The 'gross weight' of an aircraft is defined as the total weight of the aircraft when it is fully loaded, which includes the empty weight of the aircraft plus the useful load. The empty weight refers to the weight of the aircraft structure and systems without any payload or fuel, while the useful load consists of passengers, cargo, and usable fuel.

This definition is important for flight operations, as understanding the gross weight is essential for ensuring that the aircraft does not exceed its maximum allowable takeoff and landing weights, which are critical for safe operation. Properly accounting for gross weight helps in calculations related to aircraft performance, such as takeoff distance, climb rate, and fuel consumption.

The other options do not encapsulate the correct definition of gross weight. Maximum allowable weight refers to the maximum limit set by the manufacturer for safe operation, the weight without passengers only describes part of the empty weight, and the weight of the aircraft fully fueled does not account for any payload. Thus, the comprehensive view that gross weight provides is best captured by the sum of empty weight and useful load.