The Aerodynamics properties group describes the aircraft's aerodynamic performance using one of several broad strategies.
External Aero File
The External Aero File strategy uses aerodynamic data supplied by an .aero file.
.aero files used by the Advanced Fixed Wing Tool require additional information compared to the standard .aero files. Click here to view a sample .aero file for use with the Advanced Fixed Wing Tool.
| Field | Description |
|---|---|
| File Path | Click  to browse to the file that you want to use. |
| Create Copy... | Click this button to save a copy of the file to your catalog file area, which is the default location that STK's Aviator capability opens when you select an .aero file to use. You can also specify a different location, if desired. |
| Data plots selector | You can review the data in the file by selecting from a variety of data plots available. |
| Altitude | If the file has an altitude dependency, this slider is available allowing the user to set a desired altitude. |
| Single Mach The ratio of the aircraft's speed and the speed of sound at the aircraft's altitude, with local atmospheric conditions. | If selected, the slider is available allowing the user to specify the Mach number of interest. The selected Mach is displayed in the Min Mach and Max Mach fields. |
| Range | If selected, the slider is not available and you can specify the step size. The Min Mach and Max Mach numbers display. |
| Show Legend | Select this check box to display a legend for the plot lines. |
Subsonic Aerodynamics
The Subsonic Aerodynamics strategy models an aircraft that generally travels at subsonic speeds and therefore does not often experience air compression.
| Field | Description |
|---|---|
| Wing Geometry | The wingspan and aspect ratio of the aircraft's wings. Select Basic Geometry to define the static properties of an immovable wing, or Variable Geometry to define the minimum and maximum properties of an adjustable wing. |
| Max Angle of Attack The angle between the body X axis and the projection of the velocity vector onto the body XZ plane. The velocity vector is the velocity of the object as observed in the object's central body fixed coordinate system. | The maximum angle of attack possible. |
| CL0 | Enables you to specify the lift generated at zero angle of attack (AoA) as would be produced by a cambered wing. |
| CLAlpha Factor | Adjusts the slope of the lift vs. the angle of attack (AoA) line. |
| Low Speed Parasite Drag Coefficient (Cd0) | The parasitic drag coefficient of the aircraft when flying at a speed less than the Mach Divergence. Click Drag... to open a drag calculation tool that can be used to define this property. |
| Mach Divergence (Mdd) | The speed at which the aircraft begins to experience air compression, at which point the Transonic Mach Drag Factor is applied to the parasitic drag coefficient. |
| Transonic Mach Drag Factor | A scalar value applied to the aircraft's parasitic drag coefficient when it is flying faster than the Mach Divergence. |
Supersonic Aerodynamics
The Supersonic Aerodynamics strategy models an aircraft that generally travels at supersonic speeds and therefore frequently experiences air compression.
| Field | Description |
|---|---|
| Wing Geometry | The wingspan and aspect ratio of the aircraft's wings. Select Basic Geometry and click the button to define the static properties of an immovable wing, or Variable Geometry and click the button to define the minimum and maximum properties of an adjustable wing. |
| Show Template Drag Profile | STK's Aviator capability provides a selection of example drag profiles that you can use to compare to the current property settings. Select a template from the drop-down menu to display its drag profile alongside the currently defined profile. Click Apply Template to use the values in the displayed template to define the drag properties. |
| Max Angle of Attack | The maximum angle of attack possible. |
| CL0 | Enables you to specify the lift generated at zero angle of attack (AoA) as would be produced by a cambered wing. |
| CLAlpha Factor | Adjusts the slope of the lift vs. the angle of attack (AoA) line. |
| Subsonic Parasite Drag Coefficient (Cd0) | The parasitic drag coefficient of the aircraft when flying at a speed less than the Mach Divergence. Click Drag... to open a drag calculation tool that can be used to define this property. |
| Transonic Min Mach | The minimum speed at which the aircraft begins to experience air compression. |
| Transonic Max Mach | The maximum speed, below supersonic, at which the aircraft experiences transonic air compression. |
| Transonic Mach Drag Factor | A scalar value applied to the aircraft's parasitic drag coefficient when it is flying between the Transonic Min Mach and Transonic Mach Drag Factor speeds. |
| Supersonic Max Mach | The speed at which the Supersonic Mach Drag Factor is applied. |
| Supersonic Mach Drag Factor | A scalar value applied to the aircraft's parasitic drag coefficient when it is flying faster than the Supersonic Max Mach. |
| Leading Edge Suction Efficiency | The ability of the wing's leading edge to ingest turbulent airflow and thereby reduce induced drag. A high suction efficiency will lower induced drag for the aircraft. |
| Lift Efficiency |
Enables you to adjust the wing lift to drag ratio. A low efficiency reduces the wing to lift drag ratio, increases the angle of attack (AOA), and increases the drag for a given maneuver. To independently define drag, adjust the Subsonic Parasite Drag Coefficient (Cd0) parameter as detailed above in this table. Note: Use small adjustments to the Lift Efficiency and Cd0 parameters to improve the degree of calibration with other aerodynamics models and known data points. |
Sub/Super/Hypersonic Aerodynamics
The Sub/Super/Hypersonic Aerodynamics model is designed to provide a "full speed range" option for modeling high speed aircraft; for hypersonics, this represents a "first principles" model that can provide significant insight. The model makes use of a thin airfoil theory at all three speed realms and allows you to independently control the frontal area ratio and the transonic and wave drag factors to give you fine control over drag. You can review contours of Angle of Attack, Drag Coefficient, Thrust Required, Leading Edge Temperature, and Wing Bottom Temperature as functions of Weight, Mach, and Altitude.
| Field | Description |
|---|---|
| Transonic Min Mach | The minimum speed at which the aircraft begins to experience air compression. |
| Transonic Max Mach | The maximum speed, below supersonic, at which the aircraft experiences transonic air compression. |
| Super - Hypersonic Transition Mach | The minimum speed at which the air flow will be treated as hypersonic. |
| Max Angle of Attack | The maximum angle of attack possible. |
| Leading Edge Frontal Area Ratio | The frontal face thickness of the aircraft's wings at their leading edge. |
| Subsonic Aspect Ratio | Wingspan2 / wing area; used for lift / drag calculations. |
| Transonic Mach Drag Factor | A scalar value applied to the aircraft's parasitic drag coefficient when it is flying between the Transonic Min Mach and Transonic Mach Drag Factor speeds. |
| Wave Drag Factor | A scalar value that models drag produced by shock waves at or near the aircraft's critical Mach number. |