EASA 031 Mass & Balance key terms

The quantity of matter in a body, measured in kilograms or pounds; unlike weight it does not change with gravity, and it is the basis of all aircraft mass and balance calculations.

The force with which gravity attracts a mass, equal to mass multiplied by gravitational acceleration; expressed in newtons or decanewtons and varying slightly with location and altitude.

A push or pull acting on a body, measured in newtons; in mass and balance it describes weight, lift and the loads transmitted through the structure and the undercarriage.

The total mass of the aircraft ready for a specific type of operation, including crew, crew baggage, catering, removable service equipment and unusable fuel and oil, but excluding traffic load and usable fuel.

The mass of the aircraft structure, powerplant, systems and fixed equipment with unusable fuel and oil, and typically defined by the manufacturer as basic empty mass including optional equipment actually fitted.

The mass of the aircraft at the start of the take-off run, comprising dry operating mass, traffic load and take-off fuel; it must not exceed the maximum certified take-off mass.

The mass of the aircraft on arrival at the destination, equal to take-off mass minus trip fuel burned; it must not exceed the maximum certified landing mass.

The mass of the aircraft without usable fuel, comprising dry operating mass plus traffic load; it must not exceed the maximum zero-fuel mass to protect the structure of the wing-to-fuselage junction.

The mass of revenue-earning load carried, normally passengers, baggage, cargo and mail including their associated items; it forms part of the traffic load and generates revenue for the operator.

The total mass of passengers, baggage, cargo and mail carried on a flight, including any non-revenue items; it is added to dry operating mass to give zero-fuel mass.

The difference between take-off mass and empty mass, representing everything the aircraft may carry: crew, fuel, oil, passengers, baggage and cargo. It indicates the carrying capability remaining.

The point through which the total mass of the aircraft acts, so that the whole weight may be considered concentrated there; its longitudinal position is expressed as a distance from the reference datum.

A fixed vertical plane or point defined by the manufacturer from which all longitudinal arms are measured; it may lie ahead of, within or behind the aircraft and is not necessarily the nose.

The horizontal distance measured from the reference datum to the centre of gravity of an item or of the whole aircraft; arms ahead of the datum are conventionally negative.

The turning effect of a mass about the datum, calculated as mass multiplied by its arm; the sum of all moments divided by total mass gives the aircraft centre of gravity position.

The perpendicular distance from the datum to the line of action of a weight; used interchangeably with arm when the load acts vertically and the aircraft is level.

The maximum mass at which the aircraft may commence the take-off run, limited by structure and certification; it may be further reduced by performance requirements such as climb gradient or obstacle clearance.

The maximum mass at which the aircraft may land, set by structural and certification limits; an overweight landing above this value requires an inspection and is normally avoided by fuel jettison or holding.

The maximum mass permitted with no usable fuel aboard, protecting the wing root bending moment; fuel in the wings relieves this bending, so fuel and payload cannot simply be traded.

A structural or certification mass limit that must never be exceeded, such as maximum take-off, landing, zero-fuel or taxi mass; it is independent of the runway and weather on a given day.

The maximum mass at which the aircraft can meet the applicable performance requirements for a particular runway, obstacle, gradient or brake energy case; it may lie below the structural limit.

The forward or aft boundary of the certified centre of gravity range within which the aircraft may be operated; exceeding it compromises control or stability and is not permitted.

The distance between the forward and aft centre of gravity limits, expressed in units of length or as a percentage of mean aerodynamic chord; it narrows as mass increases toward the maximum.

The most forward permissible centre of gravity, set by elevator authority for rotation, flare and landing, and by the nose-down pitching moment that must be balanced by the tailplane.

The most rearward permissible centre of gravity, set by static and dynamic longitudinal stability and by the reduced elevator authority available to recover from a stall or upset.

The chord of an equivalent rectangular wing producing the same aerodynamic characteristics; centre of gravity positions are often quoted as a percentage of this chord, especially for large aircraft.

The controlled method of determining empty mass and centre of gravity, covering aircraft preparation, calibration of scales, levelling, reading and recording of results, and correction for items removed or added.

Calibrated scales or load cells placed under the wheels or jacking points, with capacity and resolution appropriate to the aircraft; readings must be corrected for tare and for the arm of each weighing point.

Inaccuracy in a mass or balance determination caused by scale resolution, parallax, friction, unlevelled aircraft or arithmetic rounding; several small errors can combine to shift the computed centre of gravity.

The document showing the distribution of mass for a flight, from which take-off and landing mass and centre of gravity are derived and compared with the certified limits before departure.

A tabular or graphical form used to convert the mass of each load into moments and to determine the final centre of gravity, often combined with the load sheet in modern documentation.

The document issued to those loading the aircraft, specifying the mass, position and restraint of each consignment, so that the planned distribution and centre of gravity are actually achieved.

The maximum mass per unit area that a cargo compartment floor can withstand, expressed in kilograms per square metre; loads are spread using planks or spreader boards to stay within it.

The maximum load permitted on a defined area of the floor or structure, used together with floor load limits to prevent local deformation or failure of the cargo floor and its supporting structure.

Distributing a concentrated mass over a larger floor area by means of spreader boards or planks, so that neither the floor load limit nor the area load limit is exceeded at any point.

The use of straps, nets, locks or pallets to secure loads against flight, turbulence and ground handling accelerations; restraint must resist forward, aft, lateral and upward load factors.

Articles or substances capable of posing a risk to health, safety or property, which must be classified, packed, marked, labelled and loaded under specific segregation and stowage rules, with mass recorded separately.

The mass per unit volume of fuel, varying with temperature and fuel type; it is used to convert measured volume into mass, and an assumed density error directly affects the computed take-off mass.

The mass of fuel aboard, obtained by multiplying volume by density rather than assuming a fixed figure; it changes during flight through burn and is a major contributor to take-off mass and centre of gravity movement.

Fuel that cannot be safely supplied to the engines in all flight attitudes; it is included in the empty or dry operating mass and must not be counted as available fuel for flight planning.

The fuel consumed from take-off to landing at the destination, including climb, cruise, descent and approach; subtracting it from take-off mass gives the landing mass.