Definition of Terms
Arm a unit of measurement for horizontal distance between a reference datum line and the centre of gravity of an object.
Datum a reference from which measurements are made. Aircraft manufactures choose an arbitrary location as a reference from which all measurements are taken for their aircraft.
Moment a force that causes rotation about a point. The distance between a point at which force is applied to a lever and fulcrum, the point about which a leaver rotates multiplied by the amount of force is the moment, expressed in units of force. (e.g: Moment = inches × pounds)
Station fixed reference points on an aircraft.
Centre of Gravity (CG) is a geometric property of any object. The centre of gravity is the average location through which weight acts for an object. We can completely describe the motion of any object through space in terms of translation through the centre of gravity for the object.
Lateral and Longitudinal CG Range The distant between the forward and rearward allowable centre of gravity movement and the side to side allowable centre of gravity movement. For most aircraft, the centre of gravity limits is shown in the aircrafts flight manual as graphed envelopes for both Longitudinal and Lateral ranges.
Empty weight means the weight as determined in accordance with this section 100.7 of Civil Aviation Orders of an aircraft including all items of fixed equipment and other equipment which is mandatory for all operations, fixed ballast, unusable fuel and total quantities of oil, engine coolant and hydraulic fluid but excluding all other items of disposable load.
Operating weight in relation to a particular type of operation of an aircraft, means the empty weight of the aircraft plus those items of removable equipment and disposable load which remain constant for the type of operation being conducted. (Removable equipment means items of equipment which are carried on some or all operations of an aircraft but which are not included in its empty weight.)
Maximum Take-Off Weight (MTOW) The maximum permissible gross weight an aircraft is permitted at take-off as stated in the aircraft’s approved flight manual.
Load data sheet means a document prepared in respect of an individual aircraft to provide weight and centre of gravity information for use in the loading system.