Maximum Zero-Fuel Weight
The zero fuel weight (ZFW) of an aircraft is the total weight of the airplane and all its contents, minus the total weight of the usable fuel on board (unusable fuel is included in ZFW).
For example, if an aircraft is flying at a weight of 5,000 kg and the weight of fuel on board is 500 kg, the ZFW is 4,500 kg. Some time later, after 100 kg of fuel has been used, the total weight of the airplane is 4,900 kg, the weight of fuel is 400 kg, and the ZFW is unchanged at 4,500 kg.
As a flight progresses and fuel is consumed, the total weight of the airplane reduces, but the ZFW remains constant (unless some part of the load, such as parachutists or stores, is jettisoned in flight).
For many types of airplane, the airworthiness limitations include a maximum zero fuel weight.
The maximum zero fuel weight (MZFW) is the maximum weight allowed before usable fuel and other specified usable agents (engine injection fluid, and other consumable propulsion agents) are loaded in defined sections of the aircraft as limited by strength and airworthiness requirements. It may include usable fuel in specified tanks when carried in lieu of payload. The addition of usable and consumable items to the zero fuel weight must be in accordance with the applicable government regulations so that airplane structure and airworthiness requirements are not exceeded.
When an aircraft is being loaded with crew, passengers, baggage and freight it is most important to ensure that the ZFW does not exceed the MZFW. When an aircraft is being loaded with fuel it is most important to ensure that the takeoff weight will not exceed the maximum permissible takeoff weight.
MZFW : The maximum weight of an aircraft prior to fuel being loaded.
For any aircraft with a defined MZFW, the maximum payload () can be calculated as the MZFW minus the OEW (operational empty weight)
The maximum zero fuel weight is an important parameter in demonstrating compliance with gust design criteria for transport category airplanes.
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