# Performance Class B (CS-23): Use of Aeroplane Performance Data

> How to interpret and use performance graphs and tables for flight planning.

- **Subject:** 032 — Performance
- **Section:** 032-03 — CS-23-Applicable Operational Requirements Performance Class B – Use of Aeroplane Performance Data for Single- and Multi-engine Aeroplanes
- **Topic code:** 032-03-03
- **Last reviewed:** 2026-04-01
- **Author:** Pablo Asensio Martínez
- **HTML version:** https://pilotsyllabus.com/en/performance/cs-23-applicable-operational-requirements-performance-class-b-use-of-aeroplane-performance-data-for/use-of-aeroplane-performance-data/

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## Interpreting Performance Graphs

Manuals provide performance data in tabular or graphical formats. It is essential to enter the graph correctly and follow the lines accurately.

### Common Variables
*   **Pressure Altitude (PA)**: Altitude above the standard datum plane (1013.25 hPa).
*   **Temperature (OAT)**: Outside Air Temperature. Often converted to **ISA Deviation** (e.g., ISA +10°C).
*   **Weight**: Aircraft mass at the start of the phase.
*   **Wind Component**: Headwind or Tailwind.

### Example: Take-Off Distance Graph
1.  **Enter with OAT**: Find the temperature on the first axis.
2.  **Move to Pressure Altitude**: Follow the line to the PA reference line and parallel the graph lines to the specific PA.
3.  **Move to Weight**: Move horizontally to the reference line, then parallel the relevant weight lines.
4.  **Move to Wind**: Move horizontally to the reference line, then parallel the wind component lines.
5.  **Read Result**: Move horizontally to read the Take-Off Distance Required (TODR).

## Corrections
Always apply corrections in the order specified by the graph (usually Temp $\rightarrow$ Alt $\rightarrow$ Weight $\rightarrow$ Wind $\rightarrow$ Slope $\rightarrow$ Surface).

### Slope Correction
*   **Upslope**: Increases Take-off Distance (aircraft works against gravity). Decreases Landing Distance (gravity aids braking).
*   **Downslope**: Decreases Take-off Distance (gravity aids acceleration). Increases Landing Distance.

### Surface Correction
*   **Grass/Gravel**: Increases rolling friction, increasing Take-off Distance.
*   **Wet**: Reduces braking effectiveness, increasing Landing Distance.

## Interpolation and Extrapolation
*   **Interpolation**: Estimating a value between two known values (e.g., weight 2500 kg between 2000 and 3000 kg). Allowed and necessary.
*   **Extrapolation**: Estimating a value outside the range of the graph. **Dangerous and usually prohibited** as performance relationships may not be linear.

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Free study notes from pilotsyllabus.com. Not a substitute for training at an approved ATO.