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).
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 Model
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 or NOAA ADDS Service - 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.
NOAA ADDS Service
The NOAA ADDS Service wind model allows you to use forecasts from the Aviation Digital Data Service (ADDS), provided by the National Oceanic and Atmospheric Administration (NOAA), to define the wind effect.
To use the NOAA ADDS Service model, you need to have data to process. ADDS forecasts are distributed in ASCII formatted message files, which cover specific regions for intervals of six, 12, or 24 hours. The wind model will use the shortest interval forecasts available for the region in which the procedure(s) occur. To obtain the most recently posted messages, click Add Current Forecast.
The following table describes the properties that you can set to manage how the forecast data is used to create the wind effect.
| Property | Description |
|---|---|
| Previous Model Blend Time | 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. |
| Message Interpolation | The method by which the wind conditions defined in a message will be applied to create the wind effect. Select One Point to apply the wind conditions in the current message constantly throughout the applicable period, or Two Point to interpolate the wind effect between the wind conditions of the current message and those of the next message. |
| Message Extrapolation | The wind effect to apply if the period of the procedure(s) extends beyond the intervals of any available messages. Select Zero Wind to stop applying a wind effect, or Hold End Point Wind to apply the wind conditions at the end of the last message at a constant rate from then on. |
| Missing Messages | The wind effect to apply if there is an interval gap in the available messages. Select Zero Wind to stop applying a wind effect until the next message interval begins, or Interpolate End Points to interpolate the wind effect using the wind conditions of the messages before and after the gap. |
| Interpolation Blend Time | The duration, when interpolating a wind effect, that the model will transition from the first point to the interpolated point and from the interpolated point to the second point. A value of 0 means that the wind bearing and speed will change instantly from one point to the next. |
To define which messages that you want to use, click Manage Data to open the ADDS Messages window, which displays a list of the messages currently available to the wind model. If you do not have any messages available for the time and region of the procedure(s), then no wind effect will be applied.
Manage Data
Click Add Current Forecast to update the list with the most recently posted messages. Click Import Message to load a message file that you have stored in another location. Click Export Message to save the message that is currently selected in the list to an .xml file. Click Remove to delete the message that is currently selected in the list.
Each message is obtained from a specific URL, and you can manage connections to those URLs by clicking Server Options.
Server Options
The ADDS Server Properties window is used to configure the message sources to obtain for the wind model. The default message sources include high and low altitude forecasts for all of the time interval types for all United States regions - Alaska, Continental United States (CONUS), Hawaii, and Western Pacific (WestPac). Click Add or Remove to modify the list of message sources, or click Restore Built-In to rebuild the list of message sources to the default composition. Click Test for any message source to verify that you have a connection to it.
If you encounter error messages that end with "Incorrect format of message header", it's possible that the URLs for the Source IDs are out of date. To correct this, you can revise the Address field for any Source ID, then click Save All Settings As Default to ensure that all future usage of the ADDS Servers uses the updated URL.
The ADDS message sources for the WestPac region are unreliably available. NOAA is aware of the problem with these message sources but does not have a solution for it and does not have an estimate for when a solution will be determined and implemented. Therefore, AGI recommends that you remove the WestPac message sources unless you have a particular need for wind data for that region.
Custom ADDS Servers
You can edit the Server URL if you want to obtain messages from a location other than the default server. You can, for example, create your own server to distribute data from other sources, as long as that data is formatted as ADDS message files. The HTML Tag field defines the HTML code element that will wrap the data in the message; the default element is the PRE tag, which is used to preserve spacing and line breaks in a block of text.
A Station File contains a list of message sources. The built-in station file is comprised of the default selection of message sources from the NOAA ADDS service. Click 
to load a different station file than the one currently selected. If you are running your own, custom server for ADDS formatted messages, for example, you will probably need to create a station file that corresponds to the sources that you have defined on your specific server. To refresh or update the message source list, click Built-In to reload the built-in station file or Reload Stations to use the currently selected station file.
Atmosphere Model
Atmosphere models in Aviator define air density, which affects the behavior of all performance models.
Selecting and Defining an Atmosphere Model
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.