Flight Performance and Planning
What the exam tests
This domain tests take-off and landing performance, density altitude, mass and balance, centre of gravity, fuel planning, alternates and the practical use of performance charts and a navigation log.
Core rules
- Take-off and landing distances increase with mass, altitude, temperature and tailwind; they decrease with headwind and lower temperature.
- Pressure altitude is indicated altitude corrected for QNH: approximately elevation + 30 ft per hPa below 1013.
- Density altitude is pressure altitude corrected for temperature; it is the altitude the aircraft “feels” for performance.
- Centre of gravity must remain within limits; a forward CG increases stability but can increase take-off distance and reduce elevator authority.
- Fuel planning must include taxi, trip, contingency, alternate and final reserve as required by the operator and regulations.
Worked example
Aerodrome elevation 2,000 ft, QNH 1003 hPa, OAT 30°C. Pressure altitude = 2,000 + 30 × (1013 − 1003) = 2,300 ft. ISA temperature at 2,300 ft is about 15 − 2 × 2.3 = 10.4°C. Using the common approximation, density altitude ≈ 2,300 + 120 × (30 − 10.4) ≈ 4,650 ft. Reasoning: the aircraft performs as if at about 4,650 ft, so take-off distance and climb time are greater than the elevation suggests.
Traps
Using QNH instead of pressure altitude; ignoring temperature correction; applying wind without direction; checking mass but not CG; omitting alternate or final reserve fuel.