Sequenced Descent

A Sequenced 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. The Descent performance model defines instantaneous points for the aircraft to hit on its descent. The Sequenced Descent allows you to define longer duration paths to fly during the descent as segments. This is similar to how pilots would fly an instrument approach, though it can be used for many other situations, such as roller coaster descents. Use this model if you have specific types of paths you need the aircraft to fly during descent. To access the sequenced descent model,

  1. Open aircraft properties.
  2. Right click on "Descent.”
  3. Select new model type. This sequenced descent model is “AGI Sequenced Descent Model”.

Chart Commands

You can interact with the chart using a right-click menu available within the actual chart display; this menu is defined in the table below.

Table - Right-Click CommandsClosed

Command Description
Select Mode Enables a left-click in the chart to select the segment that corresponds to the selected point.
Zoom Mode 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 scroll-bars, you can move around the chart while zoomed.
Undo Zoom Zooms out the chart display to its default view.
Profile Data Opens the Profile Data window for the selected point. The Profile Data 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.
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 True Airspeed: the speed that the aircraft is moving relative to the airmass that it is flying in.), calibrated airspeed (CAS Calibrated Airspeed: the speed reported by the airspeed indicator, corrected for position and instrument error.), equivalent airspeed (EAS Equivalent Airspeed: the airspeed at sea level (International Standard Atmosphere) at which the dynamic pressure is equal to the dynamic pressure at the aircraft's current true airspeed and altitude.), or Mach The ratio of the aircraft's speed and the speed of sound at the aircraft's altitude, with local atmospheric conditions. number.
Font Size Provides a sub-menu that allows you to select the font size of profile labels - small, medium, or large.
Grid Options Provides a sub-menu that allows you to define the display of grid lines within the profile.
Mark Data Points Displays individual data points along the profile line.

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.

There are five segment types that can be used to define a Sequenced 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.

Table - Initial State Segment ParametersClosed

Parameter Description
Altitude The aircraft's altitude in feet. You cannot specify an altitude below sea level (0).
Paste Profile Data Click to paste initial state data from the copy currently in Aviator's buffer to the initial state segment's parameter fields.
Airspeed The aircraft's speed; select a reference from the drop-down menu - true airspeed (TAS), calibrated airspeed (CAS), equivalent airspeed (EAS), or Mach number.
Altitude Rate The constant rate at which the aircraft will climb and descend once established in a steady climb or descent.
Flight Path Angle The initial pitch angle of the flight path.
Use Aero/Propulsion Fuel Flow Select this check box 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.
Scale Fuel Flow by Non Std Density Select this check box to scale the fuel flow based on the aircraft's actual altitude. If this option is disabled, the fuel flow will be calculated at the Default Cruise Altitude (if available), or at sea level.
Fuel Flow The amount of fuel used per unit of time selected, at sea level.
Initial Level Off for Acceleration If enabled, the aircraft will 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 the common pilot practice of achieving the aircraft's optimal climb or descent airspeed at level flight before beginning a climb or descent.

Fly To

The Fly To segment linearly interpolates airspeed and altitude rate to define an integrated curve shape that is followed until the Fly To goals are met.

Table - Fly To Segment ParametersClosed

Parameter Description
Name The segment name.
Altitude The aircraft's altitude in feet. You cannot specify an altitude below sea level (0).
Airspeed The aircraft's speed; select a reference from the drop-down menu - true airspeed (TAS), calibrated airspeed (CAS), equivalent airspeed (EAS), or Mach number.
Altitude Rate The constant rate at which the aircraft will climb and descend once established in a steady climb or descent.
Flight Path Angle The initial pitch angle of the flight path.
Fuel Flow

For fuel flow, you can choose from the following options:

  • Fly To Fuel Flow - the fuel flow rate at the end of the segment will be interpolated based on the altitude of the aircraft using a linear interpolation of fuel flow as a function of altitude.
  • Constant Fuel Flow - the specified fuel flow rate will be applied throughout the segment.
  • Fly To Fuel Consumed - the fuel flow rate will be calculated based on the specified amount of fuel consumed over the length of the entire segment.
  • Stop Fuel Consumed - the fuel flow rate will be calculated based on the specified amount of fuel consumed over the length of the segment that is flown; if an additional constraint stops the segment early, that truncated segment length will be used for the calculation.
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:

  • Altitude is
  • Or Airspeed is
  • Or Altitude Rate is
  • Or Down Range is

Select the check box for the desired constraints and enter a value for the stopping condition.
Initial Level Off for Acceleration If enabled, the aircraft will 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 the common pilot practice of achieving the aircraft's optimal climb or descent airspeed at level flight before beginning a climb or descent.

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.

Table - Linear Segment ParametersClosed

Parameter Description
Name The segment name.
Maintain Determines 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 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:

  • Altitude is
  • Or Down Range is
  • Or Airspeed is
  • Or Altitude Rate is

Select the check box for the desired constraints and enter a value for the stopping condition.
Initial Level Off for Acceleration If enabled, the aircraft will 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 the common pilot practice of achieving the aircraft's optimal climb or descent airspeed at level flight before beginning a climb or descent.

Bezier

The Bezier segment is a curve that is followed until a specific goal is met.

Table - Bezier Segment ParametersClosed

Parameter Description
Name The segment name.
Altitude The aircraft's altitude in feet. You cannot specify an altitude below sea level (0).
Altitude Rate The constant rate at which the aircraft will climb and descend once established in a steady climb or descent.
Flight Path Angle The initial pitch angle of the flight path.
Down Range The ground distance from the first point in the model.
Fuel Flow

For fuel flow, you can choose from the following options:

  • Fly To Fuel Flow - the fuel flow rate at the end of the segment will be interpolated based on the altitude of the aircraft using a linear interpolation of fuel flow as a function of altitude.
  • Constant Fuel Flow - the specified fuel flow rate will be applied throughout the segment.
  • Fly To Fuel Consumed - the fuel flow rate will be calculated based on the specified amount of fuel consumed over the length of the entire segment.
  • Stop Fuel Consumed - the fuel flow rate will be calculated based on the specified amount of fuel consumed over the length of the segment that is flown; if an additional constraint stops the segment early, that truncated segment length will be used for the calculation.
Airspeed The aircraft's speed; select a reference from the drop-down menu - true airspeed (TAS), calibrated airspeed (CAS), equivalent airspeed (EAS), or Mach number.
Stop When

The following parameters are used to define conditions that will cause the aircraft to stop the segment.

  • Airspeed is
  • Or Altitude Rate is

Select the check box for the desired conditions and enter a value for the stopping condition.
Initial Level Off for Acceleration If enabled, the aircraft will 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 the common pilot practice of achieving the aircraft's optimal climb or descent airspeed at level flight before beginning a climb or descent.

Push/Pull

The Push/Pull segment defines a push over or pull up maneuver that is followed until a specific goal is met.

Table - Push/Pull Segment ParametersClosed

Parameter Description
Name The segment name.
Pull Up/Push Over Determines whether the maneuver is a Pull Up or Push Over.
G The G force of the maneuver.
Maintain Determines 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 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.

  • Flight Path Angle is
  • Or Airspeed is
  • Or Altitude is
  • Or Altitude Rate is

Select the check box of the desired conditions and enter a value for the stopping condition.
Initial Level Off for Acceleration If enabled, the aircraft will 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 the common pilot practice of achieving the aircraft's optimal climb or descent airspeed at level flight before beginning a climb or descent.