Mass and balance - calculations and load sheets
Mass and balance - calculations and load sheets tests the arithmetic and document discipline behind a legal load sheet: basic empty mass, dry operating mass, index, moment, %MAC, standard passenger masses, fuel density and last-minute changes.
Load sheet method
- Convert every load to a mass and a moment or index using the approved arm and datum.
- DOW is basic empty mass plus crew and operational items; DOI is its index.
- %MAC = (CG arm − leading-edge arm) ÷ MAC × 100; compare with the forward and aft MAC limits.
- Last-minute changes must remain within limits and be correctly reflected on the load sheet.
Worked example
DOM is 42,000 kg at 16.0 m; payload is 10,000 kg at 20.0 m; fuel is 8,000 kg at 17.0 m. Moments: 672,000 + 200,000 + 136,000 = 1,008,000 kg·m. Total mass is 60,000 kg, so CG = 16.8 m. If the leading edge is 15.0 m and MAC is 4.0 m, %MAC = (16.8 − 15.0) ÷ 4.0 × 100 = 45%. If the envelope is 20–60% MAC, the load is legal.
Traps
Do not use DOW where DOM is required. Do not add fuel when checking MZFM. Rounding passenger masses incorrectly can push a marginal load outside limits. Confirm index units and recompute after any last-minute change.