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Weight & Balance Terms/Definitions

Terms in this set (21)

Arm (moment arm)
the horizontal distance in inches from the reference datum line to the CG of an item. The algebraic sign is plus (+) if measured aft of the datum and minus (-) if measured forward of the datum.
Basic empty weight (GAMA)
Basic empty weight includes the standard empty weight plus optional and special equipment that has been installed.
Center of Gravity (CG)
The point about which an aircraft would balance if it were possible to suspend it at that point. It is the mass center of aircraft or theoretical point at which the entire weight of the aircraft is assumed to be concentrated. It may be expressed in inches from the reference datum or in percent of MAC. The CG is a three-dimensional point with longitudinal, lateral, and vertical positioning in the aircraft.
CG Limits
The specified forward and aft points within which the CG must be located during flight. These limits are indicated on pertinent aircraft specifications.
CG Range
The distance between the forward and aft CG limits indicated on pertinent aircraft specifications
Datum (reference datum)
An imaginary vertical plane or line from which all measurements of arm are taken. The datum is established by the manufacturer. Once the datum has been selected, all moment arms and the location of CG range are measured from this point.
Delta
A Greek letter expressed by the symbol (triangle) to indicate a change of values. As an example, (triangle)CG indicates a change (or movement) of the CG.
Floor Load Limit
The maximum weight the floor can sustain per square inch/foot as provided by the manufacturer.
Fuel Load
The expendable part of the load of the aircraft. It includes only usable fuel, not fuel required to fill the lines or that which remains trapped in the tank sumps.
Licensed Empty Weight
The empty weight that consists of the airframe, engine(s), unusable fuel, and undrainable oil plus standard and optional equipment as specified in the equipment list. Some manufacturers used this term prior to GAMA standardization.
Maximum Landing Weight
The greatest weight that an aircraft normally is allowed to have at landing.
Maximum Weight
The maximum authorized weight of the aircraft and all of its equipment as specified in the Type Certificate Data Sheets (TCDS) for the aircraft.
Maximum Zero Fuel Weight (GAMA)
The maximum weight, exclusive of usable fuel.
Mean Aerodynamic Chord (MAC)
The average distance from the leading edge to the trailing edge of the wing.
Moment
The product of the weight of an item multiplied by its arm. Moments are expressed in pound-inches (in-Ib). Total moment is the weight of the airplane multiplied by the distance between the datum and the CG.
Moment Index (or Index)
A moment divided by a constant such as 100, 1,000, or 10,000. The purpose of using a moment index is to simplify weight and balance computations of airplanes where heavy items and long arms result in large, unmanageable numbers.
Payload (GAMA)
The weight of occupants, cargo, and baggage. (Bags & Butts)
Standard Empty Weight (GAMA)
aircraft weight that consists of the airframe, engines, and all items of operating equipment that have fixed locations and are permanently installed in the aircraft, including fixed ballast, hydraulic fluid, unusable fuel, and full engine oil.
Standard Weights
Established weights for numerous items involved in weight and balance computations. These weights should not be used if actual weights are available. (Ex. Gasoline - 6 Ibs/US Gal, Jet A, Jet A-1 6.8 Ibs/US Gal, etc.)
Station
A location in the aircraft that is identified by a number designated its distance in inches from the datum. The datum is, therefore, identified as station zero. An item located at station +50 would have an arm of 50 inches.
Useful Load
The weight of the pilot, copilot, passengers, baggage, usable fuel, and drainable oil. It is the basic empty weight subtracted from the maximum allowable gross weight. This term applies to GENERAL AVIATION (GA) aircraft ONLY.
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