Performance
Performance tests takeoff, landing, climb, obstacle clearance and V-speed determination under mass, altitude, temperature, wind, slope and runway surface. Norwegian operations often involve short runways, contaminated winter surfaces and terrain, so apply AFM/POH data conservatively.
Core rules
- Pressure altitude equals elevation plus (1013 minus QNH) times 30 ft, approximately.
- Density altitude is pressure altitude corrected for temperature above ISA.
- Takeoff distance increases with mass, altitude, temperature, tailwind, upslope and contamination; headwind decreases ground roll.
- V1, VR and V2 are mass and configuration dependent; never use a V-speed outside the AFM/POH schedule.
- Landing distance must fit the available runway with the required factor and stopping configuration.
Worked example
Aerodrome elevation 1,000 ft, QNH 1003 hPa. Pressure altitude is about 1,000 + (1013 minus 1003) times 30 = 1,300 ft. ISA at 1,300 ft is about 12.6 C. If OAT is 15 C, the air is warmer than ISA, so density altitude is slightly higher than 1,300 ft. Use the POH chart with actual mass and wind to obtain the takeoff distance.
Traps
- Using QFE elevation as pressure altitude.
- Ignoring contaminated runway and reverse-thrust credit limits.
- Applying headwind credit beyond the chart limit.
- Confusing V1 decision speed with rotation speed.