EASA 031 Mass & Balance flashcards

32 cards. Read the term and the definition here. The deck at the top of this page is optional.

Mass versus weight

Mass is the quantity of matter in kilograms and is constant; weight is the force of gravity on that mass, W = m × g, measured in newtons. EASA load sheets use mass in kg.

Dry operating mass

Basic empty mass plus crew, crew baggage, catering, potable water and removable service equipment. It excludes usable fuel, passengers, baggage and cargo, and is the starting point of the load sheet.

Zero-fuel mass

The mass of the aircraft with traffic load and no usable fuel: ZFM = DOM + traffic load, which also equals take-off mass minus total fuel on board. It must not exceed MZFM.

Useful load

The difference between maximum take-off mass and basic empty mass; it comprises the traffic load plus usable fuel, i.e. everything the aircraft can carry beyond its empty mass.

Moment formula

Moment equals mass multiplied by arm, where the arm is the distance from the datum to the item's centre of gravity. Total moment divided by total mass gives the CG position.

Maximum zero-fuel mass

A structural limit equal to MTOM minus the maximum usable fuel; it protects the wing root and fuselage structure when the wings contain fuel, and is checked as DOM plus traffic load.

Performance-limited take-off mass

The maximum mass permitted by runway length, obstacle clearance, climb gradient, tyre speed and brake energy for the actual conditions; it may be well below MTOM and must be used instead.

Maximum landing mass

A structural limit for the landing gear and airframe at touchdown. If the planned landing mass exceeds it, fuel must be offloaded or traffic load reduced before departure.

Regulated versus operational mass

Regulated (certificated) masses come from the type certificate and are fixed; operational or performance masses vary with conditions and may be more restrictive, and the lower value governs.

Forward CG limit reason

Set by elevator authority to rotate, flare and hold the nose up, and by the ability to recover from a nose-down attitude; too far forward the aircraft may be unable to flare.

Aft CG limit reason

Set by longitudinal static and dynamic stability; beyond the aft limit the aircraft becomes unstable in pitch, stick forces lighten and a deep stall or pitch-up may occur.

CG effect on cruise

An aft CG reduces the tail downforce and trim drag, slightly improving cruise speed and reducing fuel consumption; a forward CG increases drag and fuel burn.

CG effect on stall speed

Stall speed rises with mass and with forward CG, because more tail downforce is needed; an aft CG gives the lowest stall speed but the smallest stability margin.

CG envelope check

The loaded CG must lie inside the envelope at take-off, after fuel burn in flight and at landing; the envelope is plotted as CG position against mass with forward and aft boundaries.

Three-point weighing

Record each wheel scale reading, sum them for the mass, multiply each by its arm to get moments, then divide total moment by total mass to obtain the empty CG.

Weighing preparation

Aircraft empty and clean, defuelled to unusable fuel, oil at the stated level, loose equipment removed, tyre pressures correct, and the aircraft levelled to the specified attitude before readings.

Weighing reading errors

Parallax on analogue scales, uncalibrated or drifting load cells, tare not zeroed, hysteresis, and an aircraft not correctly levelled all cause errors that propagate into every later load sheet.

Empty mass record

The weighing report states empty mass, empty CG, datum, arms and configuration, and is amended after any modification affecting mass; it is the basis for all load calculations.

Shifting a load formula

Delta CG equals mass moved multiplied by distance moved, divided by total mass. Moving a load aft shifts the CG aft by that amount while the total mass stays unchanged.

Adding mass formula

New CG equals old total moment plus or minus the added mass times its arm, divided by the old total mass plus or minus the added mass.

Fuel burn CG effect

Fuel burned is a mass removed at the tank arm; the CG shift equals fuel mass times the difference between CG and tank arm, divided by the remaining mass.

Index method

A tabulated conversion of moment into index units using a constant and offset; load sheets sum indices and convert back to CG, so the sign convention and constant must be applied consistently.

Landing mass calculation

Landing mass equals take-off mass minus trip fuel; the landing CG is found from the take-off moment minus the trip-fuel moment taken at the trip-fuel tank arm.

Load sheet content

The signed document stating DOM, traffic load, fuel, TOM, LM, ZFM and CG position, confirming the aircraft is within mass and CG limits for the flight.

Loading supervisor duty

Responsible for correct loading, accurate mass and balance calculation and signature of the load sheet; the flight crew must check and accept it before departure.

Last-minute change

A late load change within a defined maximum, often a small percentage of MTOM, that may be loaded without a full recalculation provided the CG remains within limits.

Floor load limit

The maximum mass per unit area the cargo floor can carry; concentrated loads with small contact areas may need spreader boards to stay within area load limits.

Cargo restraint

Cargo must be secured against forward, aft, lateral and vertical loads with approved straps, nets or locks rated for the load; unsecured cargo is a hazard in turbulence.

Dangerous goods loading

Check compatibility and segregation, load and secure as required, record on the NOTOC, and include the DG mass in the traffic load and CG calculation.

Fuel mass calculation

Fuel mass equals volume multiplied by density; density varies with temperature and fuel type, so convert gallons or litres consistently and use the density for the actual fuel.

Unusable fuel

Fuel that cannot be used in flight; it is included in the basic empty mass and must not be counted as usable fuel when computing take-off fuel or trip fuel.

Fuel distribution and CG

Wing-tank fuel has an arm near the CG and changes it little; fuselage or tail-tank fuel has a large arm, so burning it moves the CG significantly.