Key notes — quick revision

031 Mass & BalanceQuick revision

Mass stack

Key fact

BEM = empty + unusable fuel + fluids, no crew. DOM = BEM + crew + items, no TL/fuel. ZFM = DOM + TL, no fuel. OM = DOM + fuel, no TL. TOM = DOM + TL + TOF. LM = TOM − trip. UL = TOM − DOM = TL + usable fuel.

Limits

Key fact

Regulated TOM = lowest of RTOM, RLM + trip fuel, MZFM + TOF. MZFM = wing root +2.5G, limits short-flight payload. MSLM may be exceeded in emergency. Jettison to get below regulated LM.

Formulas

Key fact

Moment = M × arm. CG = Σmoment ÷ Σmass. %MAC = (CG − LEMAC) ÷ MAC × 100. d/D = m/M. Vs₁ = Vs₀ × √(W₁/W₀). Floor load = mass ÷ area. Running load = mass ÷ longest side.

CG effects

Key fact

Forward CG: ↑ stability, ↑ stall speed, ↑ stick force, ↓ range, nose-wheel landing risk. Aft CG: ↓ stability, ↓ stall speed, ↑ range, spin recovery risk, VMCG limit. Trim ≠ CG movement.

Weighing & standards

Key fact

Weigh every 4 yr (individual) or 9 yr (fleet sample); fleet review every 48 months. 3 points, enclosed hangar. Crew: 85 kg flight, 75 kg cabin. Child 35 kg. Baggage standards: 11/13/15 kg (domestic/Europe/intercontinental), 20+ seats only. Infant on lap = 0.

Cargo

Key fact

Palletised = nets/straps. Containerised = ULD + manifest. Bulk = late bags/crew bags. Tie-downs mandatory. Recalculate if ±0.5% MAC or ±0.5% MLM. Fuel index missing → use next highest.

Exam trap

DOM includes crew. BEM excludes crew. ZFM has payload, no fuel. TOM has everything. Mixing these four is the number-one exam trap.

Exam trap

d/D = m/M — not M/m. Glide range unchanged by mass; glide speed/angle change. Regulated TOM uses take-off fuel with MZFM, trip fuel with RLM.