Using the Aviator Performance Model Wizard and Ephemeris Files

STK Premium (Air) or STK Enterprise
You can obtain the necessary licenses for this tutorial by contacting AGI Support at support@agi.com or 1-800-924-7244.

This lesson requires an internet connection and version 12.9 of the STK software or newer to complete in its entirety.

The results of the tutorial may vary depending on the user settings and data enabled (online operations, terrain server, dynamic Earth data, etc.). It is acceptable to have different results.

Capabilities and tools covered

This lesson covers the following capabilities and tools of the Ansys Systems Tool Kit® (STK®) digital mission engineering software:

  • STK Pro
  • Aviator
  • Aviator Performance Model Wizard
  • Export Ephemeris/Attitude tool

Problem statement

Aircrew mission planners require analytical tools that allow them to quickly create an aircraft mission profile that can be used anywhere around the world without recreating the flight profile over and over again. They need tools that can quickly create a model of a specific aircraft type using a subset of performance models as well as a standard flight profile, which users who are familiar with the STK application’s Aviator capability can use and reuse.

Solution

Use the STK application's core capabilities and the Aviator Performance Model Wizard to create an aircraft model that can be used in multiple scenarios where the aircraft type and specifications are unchanged. Create a flight profile using the custom model for an Aircraft object, then export the aircraft's mission profile as an external ephemeris file. Import the external ephemeris file into a different Aircraft object and make minor changes, placing the new aircraft in a selected location while employing the same mission profile. Finally, load the aircraft model you created earlier into another Aircraft object through the Aviator Catalog Interface to plan a new mission for the same type of aircraft.

What you will learn

Upon completion of this tutorial, you will understand the following:

  • How to use the Aviator Performance Model Wizard to create an aircraft model
  • How to create an external ephemeris file of an Aviator-built Aircraft mission
  • How to import an external ephemeris file into an Aviator-built Aircraft mission
  • How to use an aircraft model with other Aircraft objects and in other scenarios

Video guidance

Watch the following video. Then follow the steps below, which incorporate the systems and missions you work on (sample inputs provided).

Creating a new scenario

First, you must create a new scenario and then build from there.

  1. Launch the STK application ().
  2. Click Create a Scenario in the Welcome to STK dialog box.
  3. Enter the following in the STK: New Scenario Wizard:
    4. Option Value
    Name Aviator_Tools
    Location Default
    Start Default (recommend changing the time to 18:00:00.000 UTCG for daylight)
    Stop + 4 hr
  4. Click OK when you finish.
  5. Click Save () when the scenario loads. The STK application creates a folder with the same name as your scenario for you.
  6. Verify the scenario name and location in the Save As dialog box.
  7. Click Save.

Save () often during this scenario!

Using the Aviator Catalog Manager

Aviator provides a catalog structure for the loading and saving of aircraft, airports, NAVAIDs, runways, VTOL points, and waypoints. Each of these mission elements has an associated catalog in the STK application. The Aviator Catalog Manager is a utility that allows you to view the contents of catalogs, create new items, copy or edit existing items, and search for specific items.

Opening the Aviator Catalog Manager

Open the Aviator Catalog Manager from the Utilities menu.

  1. Select the Utilities menu.
  2. Select Aviator Catalog Manager... ().

Loading navigation data using the Aviator Catalog Manager

Load an ARINC424 data file containing navigation information. ARINC424 data files are the only valid data sources for NAVAID and airport sites.

  1. Resize the Aviator Catalog Manager window by extending it out to the right so that you can see more space in the large blank area.
  2. Expand () Runway ().
  3. Select ARINC424 runways ().
  4. Click the Use Master Data File ellipsis ().
  5. Navigate to <STK install folder>\Data\Resources\stktraining\samples when the Open dialog box appears.
  6. Select the FAANFD18 data file.
  7. Click Open to select the file and to close the Open dialog box.
  8. Click Save when you return to the Aviator Catalog Manager.
  9. Close () the Aviator Catalog Manager.

Inserting an Aircraft object

Insert an Aircraft object, for which you will create a flight profile.

  1. Bring the Insert STK Objects tool () to the front.
  2. Select Aircraft () in the Select An Object To Be Inserted list.
  3. Select Insert Default () in the Select A Method list.
  4. Click Insert....
  5. Right-click on Aircraft1 () in the Object Browser.
  6. Select Rename in the shortcut menu.
  7. Rename Aircraft1 () Tanker1.

Using the Aviator capability

The Aviator capability provides an enhanced method for modeling aircraft. It is more accurate and more flexible than the standard Great Arc propagator. With Aviator, the aircraft's route is modeled by a sequence of curves parametrized by well-known performance characteristics of aircraft, including cruise airspeed, climb rate, roll rate, and bank angle. The precise state of an aircraft at any given time can be computed analytically—swiftly, and without excessive data storage needs.

Selecting Aviator as the propagator

To utilize the Aviator capability, you must first set your aircraft to use Aviator as its propagator.

  1. Right-click on Tanker1 () in the Object Browser.
  2. Select Properties () in the shortcut menu.
  3. Select the Basic - Route page when the Properties Browser opens.
  4. Open the Propagator drop-down list.
  5. Select Aviator.
  6. Click Apply to accept the change and to keep the Properties Browser open.
  7. Read the information in the Flight Path Warning dialog box.
  8. Click Optimize STK for Aviator to set the scenario globe reference to Mean Sea Level (MSL) and the Animation mode to X Real Time.

    9. Aviator performs best in the 3D Graphics window when the surface reference of the globe is set to MSL instead of the default reference of WGS84. Likewise, setting the animation mode to X Real Time allows for smoother animation and better data display performance.

  9. Click OK to close the Fight Path Warning dialog box.

Using the Performance Model Wizard

In Aviator, an aircraft model defines the physical characteristics of the aircraft, the aircraft configuration, and the modes of flight that determine how it will fly in a given situation. These modes of flight are known as performance models. By specifying the performance model used with each phase of the aircraft's mission, you can vary the manner in which the aircraft performs based on the mission's priorities.

The Performance Model Wizard walks you through the creation of new aircraft performance models for each phase of flight that can be used when setting up an Aviator aircraft model. Each panel of the wizard allows you to select a performance model and edit the parameters for that performance model.

You will use basic performance models for your aircraft. Basic models are used to quickly design an aircraft. You will modify them with some basic performance characteristics of a real-world tanker aircraft model. While you could enter propulsion, aerodynamics, and other performance data to more accurately model your tanker aircraft using the Performance Model Wizard, you will forgo adding many of these finer details in this exercise to better focus on the tutorial's learning goals.

Creating a new performance model

Open the Performance Model Wizard to create a new aircraft model and its associated performance models.

  1. Click Performance Model Wizard () in the Initial Aircraft Setup toolbar.
  2. Enter Tanker in the Aircraft Model Name field in the Performance Model Wizard.
  3. Enter Tanker in the Performance Model Name field.
  4. Click Create.

Setting the Acceleration performance model

The Simple Acceleration strategy defines the basic turning, climb and descent transition, and attitude characteristics of the aircraft.

  1. Select Acceleration () in the Performance Models list of the Tanker dialog box.
  2. Select Simple in the Select an acceleration strategy list.
  3. Click Next two times.

Setting the fixed-wing reference surface area

You know from publicly available data that your tanker aircraft has an approximate wing surface area of 226 square meters. You can include this parameter in your Acceleration performance model.

  1. Enter 226 m^2 in the Reference Surface Area field.
  2. Click Next two times.

Setting the Climb performance model

The AGI Basic Climb Model is comprised of a simple set of parameters that define the flight characteristics of the aircraft while climbing.

  1. Ensure Climb () is selected in the Performance Models list.
  2. Select AGI Basic Climb Model in the Select a climb performance model list.
  3. Click Next.
  4. Enter 4900 ft/min in the Altitude Rate field.
  5. Click Next.

Setting the Cruise performance model

The AGI Basic Cruise Model is comprised of a simple set of parameters that define the flight characteristics of the aircraft during level flight.

  1. Ensure Cruise () is selected in the Performance Models list.
  2. Select AGI Basic Cruise Model in the Select a cruise performance model list.
  3. Click Next.
  4. Enter 24000 ft in the Default Cruise Altitude field.
  5. Click Next.

Setting the Descent performance model

The AGI Basic Descent Model is comprised of a simple set of parameters that define the flight characteristics of the aircraft while descending.

  1. Ensure Descent () is selected in the Performance Models list.
  2. Select AGI Basic Descent Model in the Select a descent performance model list.
  3. Click Next two times.

Setting the Landing performance model

The AGI Basic Landing Model is comprised of a simple set of parameters that define the flight characteristics of the aircraft during a landing.

  1. Ensure Landing () is selected in the Performance Models list.
  2. Select AGI Basic Landing Model in the Select a landing performance model list.
  3. Click Next.
  4. Enter 7.5 kft in the Sea Level Ground Roll field.

    5. This is equivalent to 7,500 feet.

  5. Click Next.

Setting the Takeoff performance model

The AGI Basic Takeoff Model is comprised of a simple set of parameters that define the flight characteristics of the aircraft during a takeoff.

  1. Ensure Takeoff () is selected in the Performance Models list.
  2. Select AGI Basic Takeoff Model in the Select a takeoff performance model list.
  3. Click Next.
  4. Enter 178 nm/hr in the Takeoff Speed field.
  5. Enter 9 kft in the Sea Level Ground Roll field.
  6. Click Finish.
  7. Click Apply to accept your changes and to keep the Properties Browser open.

Building Tanker1's flight route

Now that you have designed your tanker aircraft model, you can begin designing its flight profile. Tanker1 will fly its mission in the vicinity of the Pittsburgh International Airport.

Adding an STK Static Object Waypoint site

An STK Static Object Waypoint is used to define a waypoint at the position of another, stationary, object within the scenario over time.

  1. Click Insert Procedure After () in the Procedures and Sites toolbar.
  2. Select Waypoint from Catalog () in the Select Site Type list in the Site Properties dialog box.
  3. Type Pittsburgh in the Filter field.
  4. Select the Enter key.
  5. Select PITTSBURGH INTL () in the inside ARINC424 airports ().

    6. Note that PITTSBURGH INTL() is marked read only () and cannot be modified.

  6. Click Next >.

Selecting a Basic Point to Point procedure

A Basic Point to Point procedure travels a straight line through 3D space from the end of the previous procedure to the site of the current procedure.

  1. Select Basic Point to Point () in the Select Procedure Type list of the Procedure Properties dialog box.
  2. Note that the Use Aircraft Default Cruise Altitude option is selected by default, and that the Altitude is set to 24000 ft MSL. This matches the value you set for your Cruise performance model.
  3. Click Finish.
  4. Click Apply to accept your changes and to keep the Properties Browser open.

Selecting an End of Previous Procedure site

An End of the Previous Procedure site can be used as a waypoint to define the site of the next procedure.

  1. Click Insert Procedure After () in the Procedures and Sites toolbar.
  2. Select End of Previous Procedure () in the Select Site Type list of the Site Properties dialog box.
  3. Click Next >.

Selecting a Basic Maneuver procedure

A Basic Maneuver procedure is a single action undertaken by the aircraft. It is unlike most procedures in Aviator, which represent sets of actions that together comprise a common flying procedure.

  1. Select Basic Maneuver () in the Select Procedure Type list in the Procedure Properties dialog box.
  2. Select the Horizontal / Navigation tab.
  3. Note that the Strategy is set to Straight Ahead.
  4. Set the following in the Basic Stop Conditions panel:
    5. Option Value
    Time of Flight Cleared
    Downrange 25 nm

    This procedure will end if your aircraft reaches zero pounds of fuel or flies straight ahead for 25 nautical miles, whichever comes first.

  5. Click Finish three times.
  6. Click Apply to accept your changes and to keep the Properties Browser open.

Selecting another End of Previous Procedure site

The end of the previous procedure is used as the waypoint for the next procedure in the flight route.

  1. Click Insert Procedure After () in the Procedures and Sites toolbar.
  2. Select End of Previous Procedure () in the Select Site Type list of the Site Properties dialog box.
  3. Click Next >.

Inserting a Holding – Racetrack procedure

A racetrack holding procedure is a patrol in a rectangular oval. The holding point for the procedure is the point at which the aircraft enters and exits the holding circle and is the reference point for procedures that are set to end on a course to the next procedure. This holding point is defined by a bearing and range from the procedure site; the racetrack is oriented parallel to the line of bearing. The site of a holding procedure is only a reference point for the holding pattern, and may not be encompassed by the aircraft's flight path.

  1. Select Holding - Racetrack () in the Select Procedure Type list in the Procedure Properties dialog box.
  2. Enter the following in the Hold Options panel:
    3. Option Value
    Bearing 90 deg
    Range 40 nm
    Width 15 nm
    Length 50 nm
    Entry Maneuver Use Alternate Entry Points
    Turn direction Inbound Right Turn
    Number of Full Turns 5
  3. Enter 2.00 in the Turn Factor field in the Enroute Options panel.
  4. Click Finish.
  5. Click OK to accept your changes and to close the Properties Browser.

Viewing Tanker1's flight route in the 2D Graphics window

Use the 2D Graphics window to get a good view of the flight route.

  1. Bring the 2D Graphics window to the front.
  2. Zoom in until you can see the flight route

    3. 2D View of TANKER1's FLIGHT ROUTE

Exporting ephemeris and attitude data

You can create vehicle attitude or ephemeris data for all types of vehicles by using the Export Ephemeris/Attitude tool to save external ephemeris files. An ephemeris file is an ASCII text file formatted for compatibility with the STK software that ends in a .e extension.

Once you have the ephemeris data, organized in a properly formatted table, in any ephemeris file, you can then import it into the STK application and use it anywhere else in the world, making minor changes to the location, altitude, etc. This can be used for any Aircraft object propagated with Aviator. It keeps you from having to rebuild the Aircraft object’s properties each time you want to use the same aircraft in another mission.

  1. Right-click on Tanker1 () in the Object Browser.
  2. Select Ephemeris/Attitude... in the shortcut menu.
  3. Review the default values in the Create Data File dialog box.
  4. Click Export. . ..
  5. Save the file in your scenario folder.
  6. Click Close to close the Create Data File dialog box.

Using ephemeris and attitude data with another aircraft

Now that you have created a flight profile for your tanker aircraft and exported it as an external ephemeris file, you can import its ephemeris data to use with another Aircraft object in a new, selected location, employing the same flight profile.

Inserting a second Aircraft object

Insert an Aircraft object that will use the external ephemeris file you created.

  1. Insert an Aircraft () object using the Insert Default () method.
  2. Rename Aircraft2 () Tanker2.

Changing the propagator to Aviator

To use the external ephemeris file, you must select Aviator as the aircraft's propagator.

  1. Open Tanker2’s () Properties ().
  2. Select the Basic – Route page when the Property Browser opens.
  3. Open the Propagator drop-down list.
  4. Select Aviator.
  5. Click Apply to accept your change and to keep the Properties Browser open.

Inserting a Reference State procedure

To load an external ephemeris file into Aviator, add a Reference State procedure at the beginning of the mission to define existing flight conditions. A Reference State procedure defines the full position, velocity, acceleration, and attitude of an aircraft. In this way, a Reference State can replace the need to build a full profile to get to a specific point.

  1. Click Insert Procedure After () in the Procedures and Sites toolbar.
  2. Select Reference State () in the Select Site Type list of the Site Properties dialog box.
  3. Click Next >.

Importing the external ephemeris file

The External Ephemeris procedure enables you to load an external ephemeris file and create a trajectory based on it. You can apply attitude, aerodynamics, propulsion, and thermal models to the external ephemeris trajectories.

  1. Select ExtEphem () in the Select Procedure Type list of the Procedure Properties dialog box.
  2. Click the ellipsis () in the External Ephemeris File panel.
  3. Go to your scenario folder.
  4. Select Tanker1.e.
  5. Click Open.

Setting up Tanker2’s flight mode

Choose a flight type that describes the current attitude of the aircraft across the designated time period. In this instance, your flight route is level flight.

  1. Open the Flight Mode drop-down list in the Flight Config panel.
  2. Select Forward Flight – Cruise.

Moving Tanker2 to a different location

Tanker2 will fly its mission in the vicinity of Travis AFB.

  1. Select the Use Shift/Rotate check box in the Shift/Rotate panel.

    2. The Shift/Rotate option allows you to move a given external ephemeris file to any point on the earth.

  2. Click Waypoint....
  3. Select ARINC424 airports () in the Waypoint Lat/Lon dialog box.
  4. Enter Travis in the Filter field.
  5. Select the Enter key.
  6. Select TRAVIS AFB ().
  7. Click OK to close the Waypoint Lat/Lon dialog box.
  8. Click Finish to close the Procedure Properties dialog box.
  9. Click OK to accept your changes and to close the Properties Browser.

Viewing Tanker2's flight route in the 3D Graphics window

Tanker2 is above and centered over Travis AFB.

  1. Bring the 3D Graphics window to the front.
  2. Right-click on Tanker2 () in the Object Browser.
  3. Select Zoom To in the shortcut menu.
  4. Use your mouse to view Tanker2 () over Travis AFB and its flight route.

3D VIEW OF Tanker2's flight route

You can see that Tanker2 is utilizing the same flight profile as Tanker1.

Using an aircraft model with another Aircraft object

When creating the Tanker aircraft model, you created custom performance models to define its takeoff, climb, cruise, descent, and landing characteristics. You saved your custom aircraft model to the aircraft catalog in Aviator. Both aircraft models and individual performance models are stored in Aviator catalogs; they can be accessed through the Aviator Catalog Interface for use and reuse with other Aircraft objects and across scenarios.

You can use your saved aircraft model when creating a flight profile that doesn’t use an external ephemeris file. Use the Tanker aircraft model you created earlier to fly a tanker from Altus Air Force Base (AFB) to Fairchild AFB via two VORTAC NAVAID sites.

Inserting a third Aircraft object

Insert an Aircraft object which will use the external ephemeris file.

  1. Insert an Aircraft () object using the Insert Default () method.
  2. Rename Aircraft3 () Tanker3.

Changing the propagator to Aviator

Select Aviator as the aircraft's propagator.

  1. Open Tanker3’s () Properties ().
  2. Select the Basic – Route page when the Property Browser opens.
  3. Open the Propagator drop-down list.
  4. Select Aviator.
  5. Click Apply to accept your change and to keep the Properties Browser open.

Selecting an aircraft model

Apply the Tanker aircraft model to Tanker 3 by loading it from the Aviator Catalog Interface.

  1. Click Select Aircraft () In the Initial Aircraft Setup toolbar.
  2. Select Tanker () in the Select Aircraft dialog box.

    3. Note that the Tanker () is noted as being in use () in the current scenario. It is being used by the Tanker1 aircraft.

  3. Click OK to close the Select Aircraft dialog box.
  4. Click Apply to accept your changes and to keep the Properties Browser open.

Selecting the takeoff runway site at Altus AFB

Since you have ARINC424 airport data available in the Aviator Catalog Manager, you can define a site using an airport in that data with a Runway from Catalog site type. Tanker3 is taking off from Altus AFB.

  1. Click Insert Procedure After () in the Procedures and Sites toolbar.
  2. Select Runway from Catalog () in the Select Site Type list of the Site Properties dialog box.
  3. Enter Altus in the Filter field.
  4. Select the Enter key.
  5. Select Altus AFB 17R 35L () under ARINC424 runways ().

    6. Using the runway data available in the Aviator Catalog Manager, you know that runway 17R 35L is long enough for your tanker's 9,000-foot takeoff roll.

  6. Click Next >.

Selecting the Takeoff procedure

A Takeoff procedure launches an aircraft from a runway site into the air.

  1. Select Takeoff () in the Select Procedure Type list of the Procedure Properties dialog box.
  2. Set the following options:
    3. Option Value
    Name Altus AFB
    Runway Heading The direction that the aircraft is pointing. - Use headwind runway Selected
    Runway Altitude Offset 15 ft
    Use Terrain for Runway Altitude Selected
  3. Click Finish.
  4. Click Apply to apply the changes and to keep the Properties Browser open.

Selecting the Alamosa NAVAID site

If you have ARINC424 NAVAID data available in the Aviator Catalog Manager, you can define a site using a NAVAID from that data with a Navaid from Catalog site type.

  1. Click Insert Procedure After () in the Procedures and Sites toolbar.
  2. Select Navaid from Catalog () in the Select Site Type list in the Site Properties dialog box.
  3. Enter ALS in the Filter field.
  4. Select the Enter key.

    5. ALS is the Federal Aviation Administration (FAA) designator for Alamosa, Colorado, VORTAC.

  5. Select ALS () in the ARINC424 navaids() list.
  6. Click Next >.

Selecting the Basic Point to Point procedure

Use a Basic Point to Point procedure to traverse the route to the Alamosa VORTAC.

  1. Select Basic Point to Point () in the Select Procedure Type list of the Procedure Properties dialog box.
  2. Click Finish.
  3. Click Apply to apply the changes and to keep the Properties Browser open.

Selecting the Twin Falls NAVAID site

Add the next NAVAID in the flight route.

  1. Click Insert Procedure After () in the Procedures and Sites toolbar.
  2. Select Navaid from Catalog () in the Select Site Type list in the Site Properties dialog box.
  3. Enter TWF in the Filter field.
  4. Select the Enter key.

    5. TWF is the FAA designator for Twin Falls, Idaho, VORTAC.

  5. Select TWF () in the ARINC424 navaids() list.
  6. Click Next >.

Selecting the Basic Point to Point procedure

Use a Basic Point to Point procedure to traverse the route between the two waypoints.

  1. Select Basic Point to Point () in the Select Procedure Type list of the Procedure Properties dialog box.
  2. Click Finish.
  3. Click Apply to apply the changes and to keep the Properties Browser open.

Selecting the landing runway site at Fairchild AFB

Tanker3 is landing at Fairchild AFB.

  1. Select Insert Procedure After () in the Procedures and Sites toolbar.
  2. Select Runway from Catalog () in the Site Properties / Select Site Type section.
  3. Enter Fairchild in the Filter field.
  4. Select the Enter key.
  5. Select FAIRCHILD AFB 05 23 () under ARINC424 runways ().
  6. Click Next >.

Inserting a Landing procedure

A Landing procedure brings an aircraft down from the air to a runway site.

  1. Select Landing () in the Select Procedure Type list in the Procedure Properties dialog box.
  2. Set the following options:
    3. Option Value
    Name Fairchild AFB
    Approach Mode Intercept Glideslope
    Runway Heading - Use headwind runway Selected
    Landing Options - Runway Altitude Offset 15 ft
    Landing Options - Use Terrain for Runway Altitude Selected
  3. Click Finish.

Viewing Tanker3's mission profile

The mission profile can display a variety of data describing the mission. The default profile displays the aircraft's altitude relative to its downrange distance.

  1. Look at the mission profile in the Mission Window.

    2. Tanker3 Mission Profile

    Recall that you set the Tanker Cruise performance model to 24,000 feet. You can see that between the two VORTAC sites, Tanker3 maintains a cruising altitude of 24,000 feet.

  2. Click OK to accept your changes and to close the Properties Browser.

Saving your work

Clean up your workspace and close out your scenario.

  1. Close any open windows except for the 2D and 3D Graphics windows.
  2. Save () your work.
  3. Close the scenario when finished.

Summary

This scenario was designed to show you how to configure an Aircraft object using Aviator and some of its tools. You used the Aviator Performance Model Wizard to create a custom aircraft model. You then designed a generic flight orbit for an Aircraft object. This mission profile might be used every day in one location, or it could be used somewhere else around the world. Next, you exported the Aircraft object's mission profile as an external ephemeris file. Then, you imported the external ephemeris file into a different Aircraft object, making minor changes, which placed the new aircraft in the selected orbit in a different location. Finally, you reused your custom aircraft model for an aircraft that flew a long-distance flight between two airfields. If you fly the same type of aircraft from multiple locations, you can use your aircraft models and mission profiles over and over. You don’t have to recreate your aircraft each time.