Aerodynamics Analysis

This utility can be opened from the SimObject Debug Menu, and was developed to provide a comparison between the aerodynamic forces and moments computed by the Legacy and Modern flight models for an aircraft.

The window is split into three sections which are each explained below.

Active Flight Model#

This section simply shows which flight model is currently active, along with the values of the parameters legacy_fm_only and modern_fm_only.

Force Visualization in the 3D Scene#

This section controls the visualization of the total airframe aerodynamic force within the world, displayed as a coloured vector, originating from the center of gravity of the aircraft:

By default it will show the Legacy FM (when checked) as a grey vector, and the Modern FM (when checked) as green vector, and you can also check the Difference option to see the Difference between the two as a red vector, which extends from the endpoint of the Legacy FM vector to the endpoint of the Modern FM vector (if neither vector is enabled, the Difference vector will originate at the aircraft center of gravity.

Note that you have additional options to set the vector scale by specifying the relationship between the force magnitude and the displayed line length where:

• you can set the force scale and the units to be represented, one of: G, lbf, kgf, tf, N, or kN. When G is selected, 1G corresponds to the current total aircraft weight.

• you can then set the line length value using wingspan, ft, or m.

  NOTE

  The total weight values underneath this option can be used as a reference when setting the force-magnitude scale.

Numerical Comparison of Aerodynamic Data#

This section is used to show the hard data behind the forces and moments in play when using the selected flight model. It is split into the following four sections:

• Coordinate System Convention#

  

  Here you can select the coordinate-system convention used within the window, one of the following:

  • MSFS default

  • ISO-1151(opens in a new tab)

  • GOST 20058-80(opens in a new tab)

  These options represent the coordinate-system conventions used in different technical domains and standards, with each defining its own axis directions and positive directions of rotation. You can click on the information icon (!) to display the complete convention definitions.

• Airframe Aerodynamic Forces#

  

  This section displays the aerodynamic forces computed by the Legacy FM (FSX) and Modern FM (MSFS 2020/2024) flight model, together with the differences between them. These difference values are calculated as:

  $$\Delta = \text{Modern FM} - \text{Legacy FM}$$

  You have the following options available to modify the data:

  • Reference Frame: Select the Body, Stability, or Wind reference frame used to express the forces and coefficients. The force-component and coefficient symbols and names shown in the table headings follow the notation of the selected reference frame and coordinate-system convention.

  • Force Vector Unit: The unit to be used to display the force vector stability axis, one of: lbf, kgf, tf, N, or kN.

  The two tables available will show the force vector and corresponding force coeficients.

• Airframe Aerodynamic Moments#

  

  This section displays the aerodynamic moments computed by the Legacy FM (FSX) and Modern FM (MSFS 2020/2024) flight model, together with the differences between them. These difference values are calculated as:

  $$\Delta = \text{Modern FM} - \text{Legacy FM}$$

  You have the following options available to modify the data:

  • Reference Frame: Select the Body, Stability, or Wind reference frame used to express the moments and coefficients. The moment-component and coefficient symbols and names shown in the table headings follow the notation of the selected reference frame* and coordinate-system convention.

  • Moment Vector Unit: The unit to be used to display the moment vector, one of: lbf, kgf, tf, N, or kN.

  The two tables available will show the moment vector and corresponding moment coeficients.

• Related Data#

  

  This section displays flight-condition and aircraft-geometry data relevant to the calculation and analysis of the aerodynamic forces, moments, and coefficients. Note that the units of applicable physical quantities can be selected individually.