Weight and Balance, and Planning
Weight and balance
You must compute empty weight, basic operating weight, payload, fuel, and maximum takeoff/landing weights, and verify CG position within limits. Know the difference between arm (moment arm), moment (weight × arm), and CG (total moment ÷ total weight).
Concepts
- Maximum takeoff weight (MTOW), maximum landing weight (MLW), maximum zero-fuel weight (MZFW).
- CG limits forward and aft; forward CG → higher stall speed, heavier stick forces; aft CG → lighter forces, reduced stability.
- Loading envelope and how fuel burn shifts CG.
- Flight planning: fuel = taxi + trip + reserve + alternate + contingency; know the standard reserve (typically 30 min day VFR, 45 min night/IFR - verify current RBAC).
Traps
- Forgetting to include fuel in the weight for takeoff but not landing (fuel burn changes both weight and CG).
- Mixing lb and kg or inches and metres units.
- Using the empty weight CG as the operating CG without adding crew/payload.
- Ignoring MZFW on long flights with heavy payload.
Worked example / rule of thumb
Empty weight 700 kg at arm 1.0 m (moment 700). Pilot 80 kg at 1.2 m (96). Fuel 100 kg at 1.5 m (150). Total weight = 880 kg; total moment = 946; CG = 946 ÷ 880 ≈ 1.075 m. Check against envelope.
Rule of thumb: aft CG increases cruise speed slightly but reduces stability - always verify within limits.