Flight Performance and Planning
Domain: Flight Performance and Planning. The examiner tests whether you know which inputs move the numbers, by how much, and whether your loading and fuel plan leave a legal margin.
Density altitude is the master variable
Pressure altitude is indicated altitude with 1013 hPa set; density altitude adds temperature, rising roughly 120 ft per °C the OAT is above ISA. Thinner air means less engine power, a less effective propeller and a higher IAS for the same lift, so ground roll grows and climb gradient falls. Two fields at the same elevation can differ by hundreds of feet on one afternoon.
Correct in the published order
Read the POH value for pressure altitude and temperature, then apply wind, slope and surface corrections in the published sequence. Headwind credit is normally capped at 50% of the reported component; tailwind is added in full. Allow about 5% per 1% of upslope and +15% for dry grass; contaminated runways may be unusable. Charted landing distances are short-field figures multiplied by 1.15 on a dry paved runway - a margin, not a bonus.
Weight, balance and fuel
Maximum structural masses and CG limits are hard limits. An aft CG shortens the ground roll but degrades static stability and can make stall and spin recovery violent; a forward CG raises rotation and approach speeds. Fuel planning is taxi + trip + contingency + final reserve + alternate, and the reserve never appears in the trip leg.
Worked example
Field elevation 1,200 ft, QNH 1003: pressure altitude ≈ 1,200 + 10 × 30 = 1,500 ft. ISA there is 15 − 3 = 12 °C; OAT 25 °C is ISA +13, so density altitude ≈ 1,500 + 13 × 120 ≈ 3,060 ft. Enter the chart at that row, then correct for wind and slope.
Traps
Quoting chart distance with no surface or slope factor; using IAS where groundspeed is needed; applying full headwind credit when the POH caps it at 50%.