Performance
Performance questions ask you to apply defined corrections to a chart or table and to understand the physics behind them. Separate the four cases: take-off distance (ground roll and to 50 ft), landing distance (from 50 ft and ground roll), climb performance (gradient and rate), and cruise/en-route performance.
Key concepts: density altitude and its effect on all performance; the difference between pressure altitude and density altitude; effect of mass, wind, slope, runway surface, temperature and pressure on distances; V speeds (V1, VR, V2, Vmcg, Vmca, Vref) and what each protects; climb gradient versus climb rate and the conversion between them; obstacle clearance and net versus gross gradients; and the effect of contamination (wet, snow, ice) on braking and on the accelerate-stop distance.
Traps: applying a wind correction in the wrong direction (headwind reduces ground roll, tailwind increases it); forgetting that a tailwind correction is often given as a percentage per knot; mixing pressure altitude with density altitude when the chart asks for one; and assuming a climb gradient in percent equals feet per nautical mile - it does not directly.
Worked example: a 3.3% climb gradient at 120 kt ground speed. Rate of climb = gradient × ground speed = 0.033 × 120 = 3.96 nm/min ≈ 4 nm/min; in feet per minute, 3.3% is about 200 ft/nm, so 200 × 4 ≈ 800 ft/min. Rule of thumb: 1% ≈ 60 ft/nm, so multiply the percentage by 60 to get feet per nautical mile.