B. weight
Standard Weight Empty: The weight of the airframe and engine with all standard equipment installed. It also includes the unusable fuel and oil.
Optional or Extra Equipment: Any and ail additional instruments, radio equipment, etc., installed but not included as standard equipment, the weight of which is added to the standard weight empty to get the basic empty weight. It also includes fixed ballast, full engine coolant, hydraulic and de-icing fluid.
Basic Weight Empty: The weight of the airplane with all optional equipment included. In most modern airplanes, the manufacturer includes full oil in the basic empty weight.
Useful load (or Disposable load): The difference between gross take-off weight and basic weight empty. It is, in other words, all the load which is removable, which is not permanently part of the airplane. It includes the usable fuel, the pilot, crew, passengers, baggage, freight, etc.
Payload: The load available as passengers, baggage, freight, etc., after the weight of pilot, crew, usable fuel have been deducted from the useful load.
Operational Weight Empty: The basic empty weight of the airplane plus the weight of the pilot. It excludes payload and usable fuel.
Usable Fuel: Fuel available for flight planning.
Unusable Fuel: Fuel remaining in the tanks after a runout test has been completed in accordance with government regulations.
Operational Gross Weight: The weight of the airplane loaded for take-off. It includes the basic weight empty plus the useful load.
Maximum Gross Weight: The maximum permissible weight of the airplane.
Maximum Take-Off Weight: The maximum weight approved for the start of the take-off run.
Maximum Ramp Weight: The maximum weight approved for ground manoeuvring. It includes the weight of fuel used for start, taxi and run up.
Zero Fuel Weight: The weight of the airplane exclusive of usable fuel.