Potable water. The water carried in an aircraft for the purpose of drinking.

Ramp weight. The zero fuel weight plus all of the usable fuel on board.

Reference datum. (GAMA) An imaginary vertical plane from which all horizontal distances are measured for balance purposes.

Reduction factor. A number, usually 100 or 1,000, by which a moment is divided to produce a smaller number that is less likely to cause mathematical errors when computing the center of gravity.

Residual fuel. The fuel that remains trapped in the system after draining the fuel from the aircraft with the aircraft in level flight attitude. The weight of this residual fuel is counted as part of the empty weight of the aircraft.

Service ceiling. The highest altitude at which an aircraft can maintain a steady rate of climb of 100 feet per minute.

Small aircraft (14 CFR part 1). An aircraft weighing 12,500 pounds or less maximum certificated takeoff weight.

Standard empty weight. (GAMA) The weight of a standard airplane including unusable fuel, full operating fluids, and full oil.

Static load. The load imposed on an aircraft structure due to the weight of the aircraft and its contents.

Station. (GAMA) A location along the airplane fuselage usually given in terms of distance from the reference datum.

Strain sensor. A device that converts a physical phenomenon into an electrical signal. Strain sensors in a wheel axle sense the magnitude of the force the axle deflects and create an electrical signal that is proportional to the force that caused the deflection.

Structural station. A location in the aircraft, such as a bulkhead, that is identified by a number designating its distance in inches or percent MAC from the datum. The datum is, therefore, identified as station zero. The stations and arms are identical. An item located at station +50 would have an arm of 50 inches.

Takeoff weight. The weight of an aircraft just before beginning the takeoff roll. It is the ramp weight minus the weight of the fuel burned during start and taxi.

Tare weight. The weight of any chocks or devices that are used to hold an aircraft on the scales when it is weighed. The tare weight must be subtracted from the scale reading to get the net weight of the aircraft.

TEMAC. Trailing edge of the mean aerodynamic chord.

Type Certificate Data Sheets (TCDS). The official specifications issued by the FAA for an aircraft, engine, or propeller.

Undrainable oil. The oil that does not drain from an engine lubricating system when the aircraft is in the normal ground attitude and the drain valve is left open. The weight of the undrainable oil is part of the empty weight of the aircraft.

Unusable fuel. (GAMA) The fuel remaining after a test has been completed in accordance with governmental regulations.

Usable fuel. (GAMA) The fuel available for flight planning.

Useful load. (GAMA) The difference between takeoff weight, or ramp weight if applicable, and basic empty weight.