Aircraft Performance
The Aircraft Performance domain tests how to extract and apply POH/AFM data for takeoff, landing, climb and wind. The exam expects correct chart technique and an understanding of why density altitude and wind change the numbers.
Core rules
- Density altitude is pressure altitude corrected for non-standard temperature. High density altitude reduces lift and thrust, increases true airspeed for a given IAS, and lengthens takeoff, landing and climb distances.
- Use the actual pressure altitude, temperature, weight, wind, runway slope and surface condition. Interpolate within chart limits; never extrapolate.
- Wind components: headwind = V cos θ; crosswind = V sin θ, where θ is the angle between wind and runway.
- Climb gradient (%) = ROC / (GS × 101.3), with ROC in ft/min and GS in kt. Use ground speed for obstacle gradient.
Worked example
Wind 15 kt at 30° off runway: crosswind = 15 sin30° = 7.5 kt; headwind = 15 cos30° = 13.0 kt. If the aircraft climbs at 500 ft/min with a 90 kt ground speed, gradient = 500/(90 × 101.3) = 5.5%. A 3° glidepath needs about 5.2%, so this climb margin is small.
Traps
- Using IAS instead of GS in the gradient formula.
- Reading a chart at a weight above MTOW or at a temperature outside the printed range.
- Applying a headwind component to the still-air POH takeoff distance without reading the chart's wind correction.
- Forgetting runway slope, contaminated runway, or anti-skid/configuration assumptions.