Flight Performance and Planning (Mass and Balance, Performance, Flight Planning)
Flight Performance and Planning tests your ability to predict whether the aircraft can safely complete the flight: mass and balance, take-off and landing performance, density altitude, fuel planning and the practical flight plan.
Mass and balance
- Mass limits include maximum take-off mass, maximum landing mass and maximum zero-fuel mass.
- Balance is expressed as centre of gravity (CG) position; it must remain within the forward and aft limits for take-off, in flight and landing.
- Moment = mass × arm. Total moment divided by total mass gives CG.
- Fuel volume must be converted to mass using the correct density before calculating moments.
Performance and planning
- Take-off and landing distances increase with mass, altitude, temperature and tailwind; density altitude captures the combined effect of pressure altitude and temperature.
- VFR fuel planning normally includes trip fuel, contingency, reserve and taxi fuel; the exact regulatory reserve comes from CAA regulations and the flight plan.
- Use current winds, temperatures and pressures; do not plan with forecast values that are outside the flight window.
Worked example
Empty mass 700 kg at arm 1.20 m; pilot 80 kg at 0.95 m; fuel 100 kg at 1.50 m; baggage 20 kg at 2.10 m. Moments: 840 + 76 + 150 + 42 = 1,108 kg·m. Total mass = 900 kg. CG = 1,108 ÷ 900 = 1.231 m. If the envelope is 1.15-1.35 m, the loading is within limits.
Traps that cost marks
- Using litres as kilograms.
- Forgetting that fuel burn moves the CG during flight.
- Using pressure altitude instead of density altitude for performance.
- Omitting contingency or taxi fuel from the fuel plan.