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Climb / Descent | Cruise | Sequenced Climb / Descent | Terrain Follow | VTOL
There are seven advanced performance models in Aircraft Mission Modeler - Climb, Descent, Cruise, Sequenced Climb, Sequenced Descent, Terrain Follow, and VTOL. Some aircraft models include advanced performance models by default, but they are not integral to all aircraft. Each of these models and their parameters are defined below.
A Climb or Descent performance model is comprised of two or more points that define the characteristics of the performance model. These points are displayed in a chart at the top of the display and defined in a table below. You can add new points by left-clicking in the profile to add a point at that specific location. You can also add a new point before the currently selected point by clicking Insert Item and defining the point in the window that appears. You can edit existing points by double-clicking any of their fields in the table or by clicking Edit Item ... to edit the currently selected point in a separate window; in addition, you can edit the altitude of a point by double-clicking it in the chart.
Click Remove Item to remove the currently selected point. A point that is displayed in red is an invalid entry - one which is not a monotonic increase of fuel consumption, time elapsed, and downrange distance over the previous entry. Click Remove Invalid Items to remove all points that are currently indicated as being invalid.
You can also interact with the chart using a right-click menu available within the actual chart display; this menu is defined in the following table:
| Command | Description |
|---|---|
| Insert Row | Adds a new point at the cursor's location in the chart. |
| Select Row | Enables a left-click in the chart to select the point in the table that corresponds to the selected point. |
| Zoom Box | Transforms the cursor within the chart to a magnifying glass and allows you to left-click and drag over an area of the chart to zoom in upon. Using the scrollbars, you can move around the chart while zoomed. |
| Zoom In | Zooms in the chart display upon the selected point. Using the scrollbars, you can move around the chart while zoomed. |
| Zoom Out | Zooms out the chart display by one step. |
| Zoom Out All The Way | Zooms out the chart display to its default view. |
| Profile Data | Opens the Profile Item window for the selected point. |
| 2nd Y Axis... | Allows you to define the secondary Y axes of the chart. |
| Airspeed Display | Allows you to set the airspeed reference of the performance model - true airspeed (TAS), calibrated airspeed (CAS), equivalent airspeed (EAS), or Mach number. |
Select Use Aero/Propulsion Fuel Flow to use the fuel flow calculated by the aerodynamics and propulsion strategies defined in the active acceleration performance model; if the acceleration performance model is not set to calculate fuel flow, then fuel flow will not be calculated for this performance model, either.
Enable Initial Level Off for Acceleration if you want the aircraft to level off and accelerate or decelerate until its airspeed is within the defined Relative airspeed tolerance, and only then begin its climb or descent. This models common pilot practice of achieving the aircraft's optimal climb or descent airspeed at level flight before beginning a climb or descent.
The fields that define each point in the model are described in the following table:
| Field | Description |
|---|---|
| Altitude | Defines the aircraft's altitude in feet. You cannot specify an altitude below sea level (0). If a procedure is specified that requires the aircraft to fly below sea level, the performance models in effect at sea level will be applied to that procedure. |
| Downrange | Defines the ground distance in nautical miles from the first point in the model to the aircraft's position at this point. |
| Elapsed Time | Defines the amount of time that has elapsed since the first point of the model. |
| Segment Time | Defines the amount of time that has elapsed since the previous point of the model. |
| Airspeed | Displays the calculated airspeed during this segment of the model; select a reference from the Airspeed Display drop-down menu above the table - true airspeed (TAS), calibrated airspeed (CAS), equivalent airspeed (EAS), or Mach number. |
| Fuel | Defines the amount of fuel required to climb from or descend to sea level for the associated altitude; this number must be a monotonic increase or decrease, respectively, from the previous entry. |
| Fuel Flow | Defines the amount of fuel used in pounds per hour. |
The Profile Item window displays mission data at the point in the performance model profile at which it is invoked from the right-click command menu. Click Copy to Clipboard to copy the data in this window to the clipboard.
A Cruise performance model is the same as the Basic Cruise performance model except that it allows you to specify airspeeds at multiple altitudes - rather than simply defining a ceiling altitude - using the Altitude table. Right-click an entry in the table and select Insert Before or Insert After to add rows; you cannot insert a row after the last row or before the first row. Select Delete to remove the currently selected row or Delete All Invalids to remove all invalid rows; you cannot remove the first or last rows.
A Sequenced Climb or Descent performance model is comprised of one or more segments that define the characteristics of the performance model. These segments are displayed in a chart at the top of the display and defined in a list below and to the left. The sequence begins with an initial state segment, which cannot be removed.
You can interact with the chart using a right-click menu available within the actual chart display; this menu is defined in the following table:
| Command | Description |
|---|---|
| Select Profile Segment | Enables a left-click in the chart to select the point in the table that corresponds to the selected point. |
| Zoom Box | Transforms the cursor within the chart to a magnifying glass and allows you to left-click and drag over an area of the chart to zoom in upon. Using the scrollbars, you can move around the chart while zoomed. |
| Zoom In | Zooms in the chart display upon the selected point. Using the scrollbars, you can move around the chart while zoomed. |
| Zoom Out | Zooms out the chart display by one step. |
| Zoom Out All The Way | Zooms out the chart display to its default view. |
| Profile Data | Opens the Profile Item window for the selected point. |
| 2nd Y Axis... | Allows you to define the secondary Y axes of the chart. |
| Airspeed Display | Allows you to set the airspeed reference of the performance model - true airspeed (TAS), calibrated airspeed (CAS), equivalent airspeed (EAS), or Mach number. |
You can add a new segment by right-clicking a segment in the list and selecting Insert Before or Insert After; you can remove a segment by selecting Delete. Select Final State to view the final state of the segment. The properties of each segment are displayed to the right when that segment is selected in the list. Click Apply Now to apply changes that you have made to any of the segments and recalculate the performance model.
Enable Initial Level Off for Acceleration if you want the aircraft to level off and accelerate or decelerate until its airspeed is within the defined Relative airspeed tolerance, and only then begin its climb or descent. This models common pilot practice of achieving the aircraft's optimal climb or descent airspeed at level flight before beginning a climb or descent.
There are five segment types that can be used to define a Sequenced Climb or Descent performance model - Initial State, Fly To, Linear, Bezier, and Push/Pull; each is described in a table below.
Initial State
The Initial State segment defines the state of the aircraft at the beginning of the performance model.
| Parameter | Description |
|---|---|
| Paste Profile Data | Click to paste initial state data from the copy currently in Aircraft Mission Modeler's buffer to the initial state segment's parameter fields. |
| Altitude | Defines the aircraft's initial altitude in feet. You cannot specify an altitude below sea level (0). |
| Airspeed | Defines the aircraft's initial speed; select a reference from the drop-down menu - true airspeed (TAS), calibrated airspeed (CAS), equivalent airspeed (EAS), or Mach number. |
| Altitude Rate | Defines the rate of change of altitude at the initial state of the climb or descent. |
| Flight Path Angle | Defines the initial pitch angle of the flight path. |
| Fuel Flow | Defines the amount of fuel used per unit of time selected; enter a value or enable Use Aero/Propulsion Fuel Flow to use the fuel flow calculated by the aerodynamics and propulsion strategies defined in the active acceleration performance model; selecting this option will disable the Fuel Flow field for all segments in the model. If the acceleration performance model is not set to calculate fuel flow, then fuel flow will not be calculated for this performance model, either. |
Fly To
The Fly To segment linearly interpolates airspeed and altitude rate to define an integrated curve shape that is followed until a specific goal is met.
| Parameter | Description |
|---|---|
| Name | The segment name. |
| Fly To |
These parameters are used to define the final state of the segment. Altitude and Airspeed are used in every instance, and drop-down menus allow you to select between other options. You can define the aircraft's altitude rate or flight path angle. For fuel flow, you can choose from the following options:
|
| Additional Constraints |
The following parameters are used to define conditions that will cause the aircraft to stop the segment immediately, regardless of its progress toward the final state conditions defined in the Fly To section:
Enable the desired constraints and enter a value for the stopping condition. |
Linear
The Linear segment is a straight line that is followed until a specific goal is met. The altitude rate is held constant from the end of the previous segment.
| Parameter | Description |
|---|---|
| Name | The segment name. |
| Maintain | Defines whether the aircraft will Maintain its current airspeed during the segment or whether it will Accelerate or Decelerate at a specific G force rate. |
| Fuel Flow | Defines the fuel flow rate during the segment. |
| Stop When |
The following parameters are used to define conditions that will cause the aircraft to stop the segment:
Enable the desired constraints and enter a value for the stopping condition. |
Bezier
The Bezier segment is a curve that is followed until a specific goal is met.
| Parameter | Description |
|---|---|
| Name | The segment name. |
| Fly To |
These parameters are used to define the final state of the segment. Altitude, Downrange, and Airspeed are used in every instance, and drop-down menus allow you to select between other options. You can define the aircraft's altitude rate or a fixed flight path angle. For fuel flow, you can choose from the following options:
|
| Stop When |
The following parameters are used to define conditions that will cause the aircraft to stop the segment.
Enable the desired conditions and enter a value for the stopping condition. |
Push/Pull
The Push/Pull segment defines a push over or pull up maneuver that is followed until a specific goal is met.
| Parameter | Description |
|---|---|
| Name | The segment name. |
| Pull Up/Push Over | Defines whether the maneuver is a Pull Up or Push Over. |
| G | Defines the G force of the maneuver. |
| Maintain | Defines whether the aircraft will Maintain its current airspeed during the segment or whether it will Accelerate or Decelerate at a specific G force rate. The airspeed or G force rate is displayed next to the selection. |
| Fuel Flow | Defines the fuel flow rate during the segment. |
| Stop When |
The following parameters are used to define conditions that will cause the aircraft to stop the segment.
Enable the desired conditions and enter a value for the stopping condition. |
The Profile Item window displays mission data at the point in the performance model profile at which it is invoked from the right-click command menu. Click Copy to Clipboard to copy the data in this window to Aircraft Mission Modeler's buffer; the copy can be pasted to define an Initial State segment or procedure.
A Terrain Follow performance model defines the flight characteristics of the aircraft while performing a Terrain Following procedure. The following table describes the parameters that comprise a Terrain Follow performance model.
| Parameter | Description |
|---|---|
| Max Pitch Angle | Define the maximum pitch angle (both positive and negative) the aircraft will be allowed to use; higher values result in a rougher ride. |
| Airspeed | Define the aircraft's cruising airspeed while following terrain; select a reference from the drop-down menu - true airspeed (TAS), calibrated airspeed (CAS), equivalent airspeed (EAS), or Mach number. |
| Terrain Window | Define the time interval over which terrain points are sampled; smaller values result in a rougher ride and are more resource-intensive with respect to computation. |
| Use Aero/Propulsion Fuel Flow | Select to use the fuel flow calculated by the aerodynamics and propulsion strategies defined in the active acceleration performance model; if the acceleration performance model is not set to calculate fuel flow, then fuel flow will not be calculated for this performance model, either. |
| Fuel Flow | Defines the aircraft's fuel flow rate. |
When defining a Terrain Follow model, it is important to understand the relationship between the Max Pitch Angle and the Terrain Window. If you specify a large value for the pitch angle and a small value for the terrain window, the airplane will not fly realistically (especially over rough terrain). Human pilots have an aversion to flying with high pitch angles close to the ground. They also mentally integrate or smooth the visual cues they get to smooth out their control inputs. This smoothing can be modeled via a time constant. The default time window of 3 seconds and pitch angle of 20 degrees is a good place to start. When using very high resolution terrain, avoid the use of small Terrain Window values, as this will increase computer resource consumption and lead to very unrealistic - perhaps even fatal to the pilot - flight.
The following table describes the fields that define a VTOL performance model.
| Field | Description |
|---|---|
| Use Aero/Propulsion Fuel Flow | Select to use the fuel flow calculated by the aerodynamics and propulsion strategies defined in the active acceleration performance model; if the acceleration performance model is not set to calculate fuel flow, then fuel flow will not be calculated for this performance model, either. |
| Max Hover Altitude | Defines the maximum altitude at which the aircraft is capable of hovering. |
| Hover Fuel Flow | Defines the aircraft's fuel flow rate while hovering. |
| Heading Change Maneuvers | Defines the aircraft's performance when changing heading while hovering; enter the Rate at which the aircraft can perform the maneuver and the Transition Time - the amount of time required to transition from another maneuvering mode to this one. |
| Vertical Maneuvers | Defines the aircraft's performance when performing vertical maneuvers; enter the Rate at which the aircraft can perform the maneuver and the Transition Time - the amount of time required to transition from another maneuvering mode to this one. |
| Translation Maneuvers | Defines the aircraft's performance when translating while hovering; enter the Rate at which the aircraft can perform the maneuver and the Transition Time - the amount of time required to transition from another maneuvering mode to this one. |
| Forward Flight Mode | Defines the aircraft's performance when transitioning to forward flight. Enter the Minimum Horizontal Plane Airspeed - the speed at which the aircraft can begin forward flight; select a reference from the drop-down menu - true airspeed (TAS), calibrated airspeed (CAS), equivalent airspeed (EAS), or Mach number. In addition, enter the Sea Level Transition Time - the amount of time required to transition from another maneuvering mode to this one when the aircraft is at sea level. |