Which items are included in the empty weight of an aircraft?

The empty weight of an aircraft includes the airframe, unusable fuel, and undrainable oil, as well as any fixed equipment that is not necessary for flight, but does not account for crew, passengers, or payload.

Unusable fuel is the fuel that cannot be used during flight due to design limitations, while undrainable oil refers to the oil that remains in the engine and other systems and cannot be removed during normal operations. Including these items in the empty weight provides a more accurate representation of the aircraft's weight that the pilot must account for before determining the usable fuel and payload limits.

Other options, such as the crew and standard equipment, do not contribute to the empty weight since they vary depending on the mission and operation of the aircraft. Similarly, payload and cargo are not included in the empty weight as they represent additional weight that contributes to the aircraft's total weight when it is loaded.