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. Remember the takeoff weight components contributions:

${\displaystyle OEW+PL+FOB=TOW}$

Where OEW is the Operating Empty Weight (that is a characteristic of the plane), PL is the Payload actually embarked, and FOB the Fuel actually embarked and TOW the actual take-off weight. ZFW is also defined as OEW + PL. The previous formula becomes:

${\displaystyle ZFW+FOB=TOW}$.

For many types of airplane, the airworthiness limitations include a maximum zero-fuel weight. This limitation is specified to ensure bending moments on the wing roots are not excessive during flight. When the aircraft is loaded before flight, the zero-fuel weight must not exceed the maximum zero-fuel weight.