Flight Performance and Planning
The Flight Performance and Planning paper tests whether you can prepare a flight that is legal, within mass and balance limits, and capable of clearing obstacles. Expect calculations and judgement questions on takeoff and landing distance, density altitude, fuel, CG and alternates.
Mass and balance
Mass and balance uses the datum, arm and moment. Total mass is the sum of empty mass, occupants, baggage and fuel. Total moment is mass × arm. CG = total moment ÷ total mass. The result must lie inside the AFM envelope for takeoff and landing; forward CG reduces performance and aft CG reduces stability.
Performance
Density altitude is pressure altitude corrected for temperature. High elevation, low pressure and high temperature increase density altitude, lengthening takeoff and reducing climb. Use the AFM charts, apply wind, slope, surface and obstacle corrections, and never use a figure for a different aircraft.
Fuel
Plan taxi, trip, contingency, alternate and final reserve. For VFR, the final reserve is normally 30 minutes by day and 45 minutes at night; confirm the MCAR figure. Convert litres to kilograms using density (avgas about 0.72 kg/L).
Worked example
Empty mass 700 kg at arm 1.20 m = 840 kg·m. Pilot 80 kg at 0.40 m = 32; passenger 70 kg at 0.40 m = 28; fuel 100 kg at 1.00 m = 100. Total mass 950 kg; total moment 1,000 kg·m; CG = 1.053 m. If the envelope is 0.95-1.25 m, the loading is legal. A 20 kg bag in the aft hold at 2.0 m would add 40 kg·m and move the CG aft; recheck the limit.
Traps
Using takeoff mass as landing mass; forgetting fuel density; mixing QNH and QFE; ignoring wind or slope; and assuming a forward CG is always safer.