Flight Performance and Planning
Performance
Take-off and landing performance depends on mass, density altitude, wind, runway slope, surface condition and configuration. Distinguish pressure altitude (elevation corrected for QNH) from density altitude (pressure altitude corrected for temperature). Use the manufacturer's graphs with the correct units and interpolation; never mix dry and contaminated runway data. Know V1, VR, V2, VREF and the effect of mass on each.
Planning and mass and balance
Fuel planning includes taxi, trip, contingency, alternate and final reserve; know the difference between minimum fuel and emergency fuel. Mass and balance requires converting mass to moment using the arm, summing moments, and checking the centre of gravity stays within the forward and aft limits for take-off, in flight and landing. Traps include using zero-fuel mass instead of take-off mass, forgetting the taxi fuel, and reading a graph from the wrong axis.
Worked example
Aerodrome elevation 2,000 ft, QNH 1003 hPa. Pressure altitude = 2,000 + (1013 − 1003) × 30 = 2,300 ft. ISA temperature at 2,300 ft ≈ 15 − 2 × 2.3 = 10.4 °C. With OAT 30 °C, density altitude ≈ 2,300 + 120 × (30 − 10.4) = 4,652 ft. The take-off run must be read at about 4,650 ft, not 2,000 ft.
Rule of thumb
About 30 ft per hPa below 1013, and about 120 ft of density altitude per °C above ISA.