Wind and Atmosphere Models

Use the Wind and Atmosphere Model tool to simulate wind and atmospheric conditions for the scenario, a mission, a specific procedure, or a group of selected procedures.

  • To edit the scenario's default wind and atmosphere models, select the Wind/Atmosphere page in the Properties Browser for the scenario.
  • To edit the mission's default wind and atmosphere models, click the button in the Initial Aircraft toolbar.
  • To edit the wind and atmosphere models of the selected procedure or procedures, right-click and select Wind/Atmosphere ... from the drop-down menu.

Wind Model

Using Wind Models in STK's Aviator capability, you can change the ground speed, flight path angle, and altitude rate of an aircraft and produce a difference between the heading The direction that the aircraft is pointing. and course of an aircraft (also known as a crab angle).

Wind Influence on ProceduresClosed

Each procedure in an aircraft's mission appropriately controls the way that the aircraft behaves in the presence of wind. In general:

  • Enroute procedures model the wind effect with higher or lower climb and descent angles and faster or slower ground speeds. These procedures will not change climb or descent altitude rates.
  • Basic Point to Point procedures model the wind effect with higher or lower altitude rates and faster or slower ground speeds. These procedures will not change flight path angles.
  • Terrain Following, Takeoff, and Landing procedures model the wind effect with higher or lower altitude rates. These procedures will not change flight path angles.
  • Translation motion is defined relative to the ground and is unaffected by the wind model.

All procedures in Aviator, except the Basic Maneuver procedure, are defined relative to fixed ground tracks. When the wind speed exceeds the aircraft airspeed, a specified ground track may not be maintained, resulting in a calculation error that will be displayed in the Message Viewer. Most configurations of the Basic Maneuver procedure are not defined relative to a ground track and therefore allow the wind model to blow the aircraft around freely.

Selecting and Defining a Wind ModelClosed

Select a Model Source from the drop-down menu to select a wind model to view or edit.

  • Scenario Model - the scenario's wind model.
  • Mission Model - the mission's default wind model.
  • Procedure Model - the wind model specific to the procedure. This option is only available if you accessed wind model tool through the right-click context menu.

You can view the properties of the models that are at or above the current level (e.g., if you have opened the tool from the Initial Aircraft Toolbar, you can see the scenario and mission wind models, but not any procedure models). You can only edit the properties of the model at the current level.

If you are defining a model in the tool, select the desired Model Type - Constant Bearing / Speed and then define any associated properties for it.

Click Copy to save the currently defined wind model to the clipboard; click Paste to define the wind model in this window with properties currently saved to the clipboard.

Constant Bearing / Speed

The Constant Bearing / Speed wind model creates a constant wind effect using the Wind Bearing and Wind Speed that you define. The Previous Model Blend Time property defines the duration that the model will spend transitioning from the model before this one (if one has been defined). A value of 0 means that the wind bearing and speed will change instantly from the previous model to this one.

Disabled

The Disabled wind option does not apply a wind effect. Select this option if you do not want to model wind effects for the currently selected Model Source.

If you disable wind effects for some, but not all, procedures in a mission, you may see abrupt changes in the aircraft's attitude when the mission transitions from procedures that do or do not apply a wind effect. This is because the wind models blend the difference from the end of one model to the beginning of the next, but the disabled option does not perform blending.

Atmosphere Model

Atmosphere models in Aviator define air density, which affects the behavior of all performance models.

Selecting and Defining an Atmosphere ModelClosed

Select a Model Source from the drop-down menu to select an atmosphere model to view or edit.

  • Scenario Model - the scenario's atmosphere model
  • Mission Model - the mission's default atmosphere model
  • Procedure Model - the atmosphere model specific to the procedure. This option is only available if you accessed atmosphere model tool through the right-click context menu.

You can view the properties of the models that are at or above the current level (e.g., if you have opened the tool from the Initial Aircraft Toolbar, you can see the scenario and mission atmosphere models, but not any procedure models). You can only edit the properties of the model at the current level.

Define a Model

To define a model, select the desired Model Type, and then select a specific model to employ from the subsequent drop-down menu. You can provide a Name for the model to help you distinguish it from others or as a reminder of why you configured the model the way that you did.

The Sea Level Temperature, Sea Level Pressure, and Sea Level Density Altitude values for the selected model are displayed alongside it. Select the Non Standard Surface Conditions check box to make the Sea Level Temperature and Sea Level Pressure fields available for edit so that you can assign different values. As long as the Non Standard Surface Conditions option is selected, changing the model in the drop-down menu will have no effect on the available fields; they will remain set to whatever value you have defined for them.

Click Copy to save the currently defined atmosphere model to the clipboard; click Paste to define the atmosphere model in this window with properties currently saved to the clipboard.