Flight Performance and Planning
Flight Performance and Planning tests your ability to turn POH data into safe decisions: mass and balance, take-off and landing distance, climb and cruise performance, fuel planning, and the effects of density altitude, wind and runway slope. Expect chart reading and simple arithmetic under time pressure.
Mass and balance
Mass affects stall speed, take-off distance and climb; CG affects stability and control. Forward CG gives a longer take-off run, higher stall speed and heavier stick forces. Aft CG gives lighter forces but reduced static stability. Compute moments (mass × arm), divide total moment by total mass, and keep the CG inside the envelope for every phase of flight.
Density altitude
Density altitude is pressure altitude corrected for temperature. Rule of thumb: add about 120 ft for each 1°C the OAT is above ISA. High, hot and humid means longer take-off, poorer climb and a lower service ceiling.
Worked example
Airfield elevation 3,000 ft, QNH 1013, OAT 30°C. Pressure altitude is 3,000 ft. ISA temperature at 3,000 ft is 15 − (2 × 3) = 9°C. The day is 21°C above ISA, so density altitude ≈ 3,000 + (21 × 120) = 5,520 ft. Use the 5,500 ft column, not the 3,000 ft one.
Fuel
Plan trip fuel, contingency, alternate, final reserve (30 minutes by day for VFR) and taxi. Do not plan to land with exactly the reserve.
Traps
Using QNH altitude instead of pressure altitude; forgetting that wind and slope corrections are separate from density altitude; and mixing litres with US gallons in fuel calculations.