Mass and Balance
Definitions and limits
Know basic empty mass, dry operating mass, take-off mass, landing mass, zero-fuel mass and payload. Understand MTOM, MLM, MZFM and the regulated limits. Trap: confusing dry operating mass (includes crew and unusable fuel) with basic empty mass.
Moment and CG
Compute moments as mass × arm and divide total moment by total mass to find the CG. Know how to use the loading sheet and the CG envelope, and how moving a mass shifts the CG by (mass moved × distance moved) / total mass. Understand that the datum and station arms are given in the manual.
Operational consequences
Know how CG position affects stability, stall speed, cruise performance and take-off rotation. Forward CG → higher stall speed, longer take-off, more stable; aft CG → lower stall speed, less stability.
Worked example: Total mass 50 000 kg, CG at 20% MAC; move 500 kg aft by 10 m. Shift = (500 × 10)/50 000 = 0.1 m - check this against the envelope in metres or %MAC.
Know how to read a trim sheet and how fuel burn shifts CG in flight.