Charts, Tables, and Performance Data Interpretation
This domain tests chart literacy: entering the right axes, interpolating honestly, and applying the corrections the notes demand.
Reading a performance chart
- Identify the axes, units and assumptions first: flap setting, bleed air, anti-ice, surface condition, pressure altitude, temperature and mass.
- Interpolate linearly between lines, and note whether each correction is additive, a percentage of the base value, or a multiplier.
- Check secondary limits: WAT, brake energy, tyre speed and climb gradient.
- Read the notes; they frequently override the graph or add a correction.
Worked example
A chart gives 990 m at sea level ISA for 1,000 kg. At 3,000 ft and ISA+20 the factor is 1.22, giving 1,208 m. A 2% upslope adds 8% of the corrected figure, so 1,305 m. A 5 kt headwind reduces 5%, so 1,240 m. A wet runway applies 1.15, giving 1,426 m.
Traps
- Applying percentages to the base value when the chart intends successive corrections.
- Using °F where the chart is in °C.
- Missing a footnote that adds distance for anti-ice or a contaminated surface.
- Reading the weight line above the intersection instead of below it.
- Forgetting that a chart valid for one flap setting is invalid for another.