Operating empty weight (OEW) or Basic Operating Weight or Empty Operating Weight is the standard basic weight for any particular series or any particular configuration. The aircraft is periodically weighed and its weight is listed with each structural modification order, or any configuration order which may alter the Empty Operating Weight (EOW). The EOW includes all fluids necessary for operation such as engine oil, engine coolant, water, hydraulic fluid and the unusable fuel. Extra fixed operator items and optional equipment required for flight are added to EOW to determine OEW. From there, any weight added to the aircraft is the Total Payload, above the OEW, which consists of (a) cargo (b) luggage (c) passengers and crew (d) stores (e) service load such as meals and beverages (f) fuel load.
The operating empty weight (OEW) is the sum of the manufacturer's empty weight (MEW), standard items (SI), and operator items (OI). All additional weight added is computed for weight, arm and moment calculations to determine the center of gravity.
OEW = MEW + SI + OI