Flight Performance and Planning
Flight Performance and Planning tests weight and balance, takeoff and landing performance, density altitude, fuel planning, and the arithmetic that turns a plan into safe limits. The exam expects you to use published data and show the calculation, not just quote a rule.
Core rules
- Mass and balance: total moment = weight × arm; CG = total moment ÷ total weight. Stay within MTOW, MLW, and CG limits.
- CG effects: forward CG improves stability but lengthens takeoff and increases stall speed; aft CG reduces stability and can make stall recovery harder.
- Density altitude: DA = pressure altitude + 120 × (OAT − ISA temperature). High DA reduces engine power, lift, and climb performance.
- Fuel: plan trip fuel, reserve, taxi, and contingency; check fuel at each leg and do not rely on gauges alone.
- Performance: use the aircraft flight manual for takeoff and landing distance and apply wind, slope, surface, and temperature corrections.
Worked example
A field is at 1,000 ft elevation, QNH 1013 hPa, OAT 30°C. Pressure altitude is 1,000 ft. ISA temperature at 1,000 ft is 15 − 2 = 13°C. The difference is 17°C. DA = 1,000 + 120 × 17 = 3,040 ft. The reasoning: each degree above ISA raises density altitude by about 120 ft, so the aircraft performs as if it were at 3,040 ft. Takeoff distance and climb rate must be read at that value.
Traps
Do not use indicated altitude as pressure altitude when QNH is not 1013 hPa. Do not mix pounds and kilograms, or inches and centimetres, within one moment calculation. Remember that fuel burn changes both weight and CG. A landing weight limit can be exceeded even if takeoff weight was legal.