Aircraft Weight & Balance Revision

This set of vocabulary flashcards covers essential weight and balance terminology, stability concepts, calculation formulas, and regulatory documentation based on the Part 66 Revision Guide.

Centre of Gravity (CG)

The point where the aircraft's total weight is assumed to be concentrated; it must lie within a specific range for flight safety.

Datum

A reference point chosen by the manufacturer from which all arm measurements are taken.

Arm

The horizontal distance from the datum to the item's CG, where a positive value indicates aft and a negative value indicates forward.

Moment

The product of weight multiplied by the arm ($\text{Weight} \times \text{Arm}$), representing the torque effect or rotational force.

Maximum Take-off Weight (MTOW)

The maximum weight approved for the aircraft at the start of the take-off run.

Maximum Landing Weight (MLW)

The maximum weight approved for the aircraft during the landing touchdown.

Maximum Zero Fuel Weight (MZFW)

The maximum approved weight of the aircraft excluding all usable fuel.

Basic Empty Weight (BEW)

The weight of the aircraft including unusable fuel and full operating fluids; when added to the payload, it equals the Zero Fuel Weight.

Zero Fuel Weight (ZFW)

The sum of the Basic Empty Weight (BEW) and the payload ($\text{BEW} + \text{Payload}$).

Ramp/Taxi Weight

The weight of the aircraft including start and taxi fuel, calculated as the Zero Fuel Weight plus total usable fuel.

Mean Aerodynamic Chord (MAC)

An imaginary chord representing the wing's average aerodynamic properties, often used to express the CG as a percentage.

LEMAC / TEMAC

Leading Edge of the Mean Aerodynamic Chord and Trailing Edge of the Mean Aerodynamic Chord, measured as positions from the datum.

%MAC Formula

$$\frac{\text{CG} - \text{LEMAC}}{\text{MAC}} \times 100$$

Longitudinal Stability

Achieved when the aircraft CG is slightly ahead of the centre of lift, allowing the nose-down force to be balanced by the tailplane.

Aft CG Effects

Reduces stability and makes stall or spin recovery difficult, potentially resulting in an unrecoverable flight condition.

Forward CG Effects

Increases tail downforce and drag, and may lead to insufficient elevator authority during take-off or landing.

Type Certificate Data Sheet (TCDS)

A document containing the CG range, empty weight CG range, maximum weight, datum position, and levelling means.

Fuel Scheduling

Critical for swept-wing aircraft where the sequence of using outboard vs inboard tanks significantly shifts the CG.

Ballast

Weight added to the aircraft either permanently or temporarily to correct the CG position.

On-board Weight & Balance Systems (OBWBS)

Systems found on large aircraft (e.g., Boeing or Airbus) that use load cells in the landing gear to provide weight and balance data to the FMC.

AMM Chapter 8

The section of the Aircraft Maintenance Manual (AMM) that serves as a reference for weight and balance procedures.

Negative Tail-wheel Load

A condition in tail-wheel aircraft measured using a spring balance anchored to the ground; the negative reaction is deducted while the rope/balance weight is added.

1 inch (conversion)

$$0.0254\,m$$

1 pound (conversion)

$$0.4536\,kg$$