Performance
Performance questions ask you to prove the aeroplane can do what you plan: clear obstacles, stop on the runway, and climb after an engine failure. Expect definitions, the take-off climb segments, and one numeric calculation.
Declared distances
- TORA: take-off run available. TODA = TORA + clearway. ASDA = TORA + stopway. LDA: landing distance available.
- The balanced field length is where accelerate-stop distance equals the one-engine-inoperative take-off distance; it gives the minimum field length and the associated V1.
Speeds and climb
- V1 is the decision speed; Vr rotation; V2 is at least 1.13 Vs1g or 1.1 Vmca.
- Screen height is 35 ft at the end of TODA; net gradient = gross gradient minus 0.9% (twin), 0.8% (three-engine) or 0.6% (four-engine).
- Second segment (gear up, V2, take-off flap): gross 2.4% twin, 2.7% three-engine, 3.0% four-engine. Final take-off segment 1.25% twin. Approach climb 2.1% twin; landing climb 3.2%.
Practical limits
- WAT (weight-altitude-temperature) charts give maximum mass for the conditions; density altitude, not pressure altitude alone, is the real driver.
- Landing distance required must not exceed LDA: the demonstrated distance is factored (about 1.67 dry, 1.92 for a wet turbine runway) and adjusted for slope, wind, temperature and reversers.
Worked example
Runway 280°, wind 240°/20 kt. The angle is 40°. Crosswind = 20 × sin 40° = 20 × 0.643 = 12.9 kt; headwind = 20 × cos 40° = 15.3 kt. If the aircraft limit is 15 kt crosswind, the take-off is legal. If the wind gusts to 30 kt, crosswind becomes 19.3 kt and the take-off is not permitted.
Traps
Using pressure altitude instead of density altitude; applying the gross gradient when the question asks for net; applying headwind credit on a contaminated runway without the manufacturer's factor; and mixing TORA with TODA when a clearway exists. Remember V1 cannot exceed Vr or Vmbe.