Flight Performance and Planning
Flight Performance and Planning tests whether you can predict takeoff, climb, cruise and landing performance, and keep the aircraft within mass, balance and runway limits. Questions often use density altitude and mass changes.
Takeoff and landing performance
- Takeoff distance increases with mass, altitude, temperature, tailwind and runway slope; it decreases with headwind.
- Density altitude is pressure altitude corrected for temperature. A useful approximation is 120 ft per °C of ISA deviation.
- Landing distance increases with mass, altitude, temperature and tailwind; contaminated runways add large factors.
Mass and balance
Centre of gravity must remain within limits for all phases. Forward CG increases stall speed and pitch authority demands; aft CG reduces static stability. Load sheets must include crew, passengers, baggage, fuel and cargo.
Worked example
Pressure altitude 5,000 ft, OAT 25°C. ISA temperature at 5,000 ft is 15 − (1.98 × 5) ≈ 5°C. The ISA deviation is +20°C. Using 120 ft/°C, density altitude ≈ 5,000 + (120 × 20) = 7,400 ft. Performance should be read at 7,400 ft, not 5,000 ft.
Traps that cost marks
- Using QNH altitude instead of pressure altitude in performance charts.
- Forgetting that a forward CG can increase takeoff distance and stall speed.
- Applying a headwind component after reading a zero-wind chart instead of before.