Performance
Performance tests take-off and landing distance, V speeds, density altitude, wind and slope, contamination and obstacle clearance. Norwegian winter operations make contaminated-runway and low-temperature corrections examinable.
Take-off and landing
TORA is runway length available for take-off; TODA adds clearway; ASDA adds stopway. V1 is decision speed, VR rotation, V2 take-off safety speed. Density altitude raises true airspeed and distance; headwind reduces distance, tailwind increases it sharply. Contamination reduces braking and may limit crosswind.
Worked example
Pressure altitude 2000 ft, OAT +20 °C. ISA temperature at 2000 ft is about 11 °C, so the day is 9 °C warmer than ISA. Using roughly 120 ft per °C, density altitude ≈ 2000 + 1080 = 3080 ft. The aircraft performs as if at about 3100 ft, so take-off distance increases.
Traps
Using pressure altitude as density altitude; forgetting wind component; applying a headwind correction to landing ground roll as well as air distance; ignoring contaminated-runway penalties; mixing TORA, TODA and ASDA.