How do I use aircraft performance charts for flight planning?

Use aircraft performance charts by selecting the chart for the exact aircraft, configuration and flight phase; entering weight, pressure altitude, temperature, wind and runway condition; interpolating between published values; applying every stated correction in order; then adding an operational safety margin and checking the result against runway, climb, fuel and landing limits.

In our Aviation & Real-World Flying coverage, we treat the approved Pilot's Operating Handbook (POH), Aircraft Flight Manual (AFM), supplements and operator data as the authority. A chart from a similar variant is not interchangeable: engine, propeller, wing, brakes, software standard or an aircraft modification can change the figures.

What information do I need before using a performance chart?

You need the aircraft's configuration, phase-of-flight weight, atmospheric conditions and relevant runway data before entering a chart.

• Aircraft and configuration: exact model, engine or thrust rating, flap setting, landing gear position, anti-ice use and any applicable modification.
• Weight: take-off weight for departure calculations, expected weight at each climb level, and forecast landing weight for arrival performance.
• Atmosphere: pressure altitude and outside-air temperature. Use density altitude only when the chart specifically requests it; many charts account for density effects by taking pressure altitude and temperature separately.
• Wind: the headwind or tailwind component along the selected runway, not simply the reported wind speed.
• Runway: available length, elevation, slope, surface type, condition and known obstacles.
• Operating technique: the specified power, speed, flap setting and braking method. Published results depend on following the stated technique.

Calculate pressure altitude from aerodrome elevation and atmospheric pressure, or read it from an altimeter set to 1013.25 hPa or 29.92 inHg when appropriate. Do not enter indicated altitude from the normal local-pressure setting unless the chart explicitly calls for it.

Establish the loading before doing the calculations. In a simulator, our workflow for loading payload and fuel and checking take-off and landing weights covers the figures needed here.

Which performance charts are used for flight planning?

A complete flight plan may require separate charts for take-off, climb, cruise, descent and landing because each phase uses different inputs and produces different outputs.

Climb data can be especially awkward when a chart is based on ISA conditions; our explanation of working through standard-temperature climb corrections covers that case. At cruise, use the tables to match speed with weight, altitude, power and fuel burn rather than selecting an arbitrary indicated airspeed.

How do I read and interpolate a performance chart?

Work from verified inputs to the chart output in the sequence printed by the aircraft manufacturer, including every limitation and correction in the chart notes.

1. Confirm the chart applies. Check the aircraft variant, configuration, units, weight range and stated runway or atmospheric assumptions. A dry, paved-runway chart does not automatically provide valid wet-grass or contaminated-runway performance.
2. Calculate the phase weight. Take-off weight is normally ramp weight minus expected taxi fuel. Landing weight is the forecast take-off weight minus trip fuel, subject to the aircraft's definitions and operating procedures.
3. Standardise the inputs. Convert temperature, distance, pressure and weight into the chart's units. Keep the conversions visible so pounds are not entered as kilograms or feet as metres.
4. Bracket each value. Find the published values immediately above and below the actual input. Do not extrapolate beyond the chart boundary; outside the approved range, the chart does not provide a valid answer.
5. Interpolate where permitted. Estimate proportionally between adjacent values or curves. Follow the printed scale because graph axes are not always linear.
6. Apply corrections in the stated order. Wind, slope, surface, temperature, anti-ice and configuration corrections may be additive, multiplicative or already included. Never apply a density-altitude correction on top of a pressure-altitude-and-temperature chart unless instructed.
7. Check the limiting result. Compare ground roll, obstacle-clearance distance, climb gradient, fuel use and landing distance with the appropriate available distances and operational limits.
8. Repeat after changes. A payload reduction, extra fuel, runway change or revised weather forecast changes the input weight or conditions and requires a fresh calculation.

Interpolation example

If a chart gives 1,100 m at 2,000 ft pressure altitude and 1,400 m at 4,000 ft, a 3,000 ft input lies halfway between them and gives 1,250 m, provided linear interpolation is allowed. Temperature and weight may then require further interpolation before applying the chart's corrections. These numbers only demonstrate the method; they are not aircraft performance data.

Flight planning is iterative. Start with estimated fuel and weight, calculate climb time and fuel, determine cruise consumption, update the expected landing weight, and then check landing performance. If the route or reserve fuel changes, repeat the affected calculations.

Operational margins and no-go decisions

A published chart value is a calculated minimum under the precise conditions and technique stated, not a sensible runway target with spare capacity already included.

For real-world operations, use the regulatory, operator or training-organisation factors that apply to the flight. There is no universal percentage suitable for every aircraft, runway and operating category. If the AFM provides no data for contamination, extreme temperature or another actual condition, an invented correction is not an acceptable substitute.

If the required performance exceeds a limit, the practical options are to:

• reduce payload or fuel while retaining required reserves;
• depart at a cooler time;
• use a longer or more favourable runway;
• select another approved flap or power configuration;
• choose an aerodrome with better performance margins; or
• do not operate until conditions improve.

Keep ground roll separate from total distance over an obstacle. For landing, compare the correct required distance with landing distance available; for transport operations, use the applicable declared distances and operator method rather than treating the physical runway length as the only limit.

Why does the chart result differ from the simulator?

Most disagreements come from mismatched inputs, the wrong aircraft data or limitations in the simulator's flight and ground-handling model.

• Wrong variant: the chart belongs to a different engine, propeller, wing or weight category.
• Wrong altitude: field elevation or indicated altitude was used instead of pressure altitude.
• Wrong distance: ground roll was compared with total distance over an obstacle, or vice versa.
• Incorrect wind treatment: total wind speed was entered instead of the runway component, or headwind credit was applied differently from the chart instructions.
• Double correction: temperature, runway condition or another factor was already included and then applied again.
• Technique mismatch: rotation speed, power setting, braking, flap or climb speed did not match the chart assumptions.
• Simulation mismatch: tyre friction, engine output, propeller efficiency, braking and weather modelling may not reproduce the real aircraft precisely.

For simulator-only planning, prefer performance documentation supplied for the specific simulated aircraft. A controlled test can reveal how closely the model follows its published data, but simulator results must never replace approved aircraft information for a real flight.