Aircraft Weight and Balance; Aircraft Handling and Storage
Mass, moment and the safe aircraft on the ground
Weight and balance: understand datum, arm, moment (weight × arm), empty weight and empty-weight CG, maximum take-off, landing and zero-fuel weights, and the CG envelope expressed in units of length or as a percentage of MAC between LEMAC and TEMAC. Weighing requires calibrated scales, level attitude, the correct configuration and correct fluid states. Forward CG makes rotation hard, lengthens the take-off run and increases cruise drag; aft CG lightens control forces and reduces static stability.
Handling and storage: towing with the correct tow bar and shear pin, marshalling signals, jacking only at the marked points with the aircraft within CG limits, tie-downs and control locks, pitot and static covers, engine and APU blanks, and protection from wind, humidity and salt. Long-term storage adds preservation: fuel-system treatment, desiccant or dehumidification, periodic engine turning, seal and tyre protection, and documented inspections before return to service.
Traps: using the wrong datum, forgetting that fuel burn moves the CG, adding ballast without recalculating, and forgetting that a load added aft of the aft limit may still be within maximum weight.
Worked example: a 2 000 kg aircraft with CG 2.00 m aft of datum. Moving 50 kg aft by 3.00 m gives a CG shift of (50 × 3.00) / 2 000 = 0.075 m, so the new CG is 2.075 m. If the aft limit is 2.05 m, the load must be reduced or redistributed.
Rule of thumb: any change of mass is a change of moment - recalculate the CG every time, and check the envelope, not just the total weight.