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Calculating Takeoff Performance

This is an advanced guide on how to calculate takeoff performance in the A32NX. This is to supplement information provided in our flyPadOS 3 documentation and usage guide.

flyPad Performance Calculator Page

Clicking on the calculate button after all the input fields are filled properly will either result in takeoff speeds and Flex temperature (if Flex was selected and can be used) being displayed in the replica of the MCDU Takeoff Perf Pages provided on the right side of the calculator unless the takeoff weight exceeds the maximum takeoff weight for the input conditions or if any of the input conditions exceed any airplane limitations. If any of these conditions occur, a suitable error message will pop up.

Examples

Information that can be obtained from Airport 10-9 (or 10-9A) charts

EGLL

egll-to.png

  • Item 1 is the elevation for a takeoff from Runway 09L.
  • Item 2 shows an example of a relatively rare zero degree turn on angle from the taxiway to the runway. This is denoted by the gray taxiway extending far enough after the turn to align the airplane with the runway direction before it gets the runway beginning (indicated by the beginning of the black runway diagram).
  • Item 3 is the elevation for a takeoff from Runway 27R.
  • Item 4 shows a common 90-degree entry from the taxiway to the runway, which requires a portion of the runway to align the airplane in the direction of the runway for takeoff.

Since the elevation of both end of the runway are the same, the slope for takeoffs from both Runway 09L and 27R is zero.

Unmarked In Above Example

The magnetic varation for this airport is show by the arrow on the lower right side of the chart.

The magnetic variation at EGLL is 0 degrees, so there is no difference between a true heading and a magnetic heading. No conversion is needed for the METAR wind direction when the wind is input manually for this airport.

eggl-10-9a.png

For a large airport like EGLL, there is not enough room to put the additional runway information on the 10-9 chart. For EGLL, the TORA distance for each runway and for intersection takeoffs is provided on the 10-9A chart. For a Runway 09L full length takeoff, the TORA is 12,001 feet or 3901 meters.

SBRF

Be aware that some runways for which the airport 10-9 chart shows a zero degree runway entry angle, MSFS 2020 has the taxiway aligned such that a 90 degree entry angle is required. One example of this is SBRF/Recife, Brazil. The circled area in the airport 10-9 chart below shows that the airplane can be aligned in the direction of takeoff before entering the black runway area. In MSFS 2020, however, the taxiway meets the runway end at a 90-degree angle.

sbrf-to.png

The magnetic variation for SBRF is 21 degrees West. For a magnetic variation in the West direction, add the magnetic variation to the true wind direction number to get the magnetic wind direction. For example, if the winds are 240/10 from the METAR, then input 261/10 into the takeoff calculator (240+21).

Rounding

You can also round this off to the nearest ten degrees 260/10, which will probably be what ATIS would give you.

LOWI

lowi.png

This airport’s 10-9 chart has all the information on one chart. This is an example where both runways have a 180-degree entry angle, that is, the airplane must use the runway to taxi to the runway end and then turn around in order to use the full runway length for takeoff. TORA values for the full runway length as well as from the taxiway intersections (where a 90-degree entry angle would apply) are listed in the Additional Runway Information section.

Calculating Runway Slope

The runway elevation for each runway is different, so each runway will have a slope value. Use the following equation to calculate the slope value:

Slope Equation

\[\frac{Elevation\,at\,end\,of\,TORA - Elevation\,at\,beginning\,of\,TORA}{TORA} * 100\]
\[ with\,all\,units\,being\,the\,same.\]

Runway 08 Example

To calculate the runway slop for Runway 08 the equation with units included would look like the following:

\[\frac{1894 - 1907}{6562} * 100 = -0.20\%\]

For LOWI, the magnetic variation is 4 degrees East. When the magnetic variation is to the East, subtract the variation from the true wind value to determine winds referenced to magnetic North. If the winds are 240/10 true from the METAR, adjust it to 236/10 when entering it into the takeoff performance calculator.

Since the magnetic variation is only 4 degrees, and winds are normally rounded to the nearest ten degrees, you can also just skip converting the wind reference from true North to magnetic North for LOWI.