Flight Performance and Planning
Performance and mass balance
Performance questions require you to use published data: take-off and landing distances, climb gradients, cruise fuel flow, and mass-and-balance envelopes. Understand the factors that change performance: mass, altitude, temperature, wind, runway slope and surface, and configuration. Know the difference between pressure altitude and density altitude, and why density altitude drives performance.
Traps
Common traps include applying a correction in the wrong direction, using indicated rather than true airspeed, and forgetting to include fuel, baggage or crew in the mass. Another trap is interpolating between chart values incorrectly or ignoring a limiting factor such as obstacle clearance or brake energy. Questions may also test whether a planned flight is legal as well as achievable.
Worked example
To estimate take-off distance at a higher temperature: start from the sea-level, standard-temperature value, apply the pressure-altitude correction, then the temperature correction, then the wind and slope corrections in the order the chart specifies. If the result exceeds the available runway, the flight is not permissible regardless of other margins.
Rule of thumb
Higher, hotter, heavier and wetter all degrade performance. If a correction makes the aircraft perform better than the baseline, check that you applied it in the correct direction.