Arc Enroute
An Arc Enroute procedure is a maneuver along the perimeter of a circle of a user-specified radius, in which the velocity vector of the aircraft is maintained perpendicular to the vector from the current position to the procedure site. The center point of the circle is the procedure's site.
If the aircraft cannot achieve the defined altitude (either by using the default cruise altitude or by specifying an altitude), the aircraft will finish the maneuver at the highest or lowest altitude it could achieve, depending on whether it was ascending or descending; no warning will be given.
The procedure contains three control points - the procedure site, the Join Arc point, and the Exit Arc point - as indicated in the diagram below. The Join Arc point is placed relative to the procedure site, along the Start Bearing and at a distance equal to the Radius. The Exit Arc point is placed at the end of the arc as defined by the Turn Angle.
Click the image to view a detailed diagram.
Altitude
| Parameter | Description
|
|---|
| Use Aircraft Default Cruise Altitude
| Select this check box to define the altitude of the procedure using the default cruise altitude specified in the currently selected cruise performance model.
|
| Delay Arc Climbs and Descents
| Select this check box to have the aircraft begin climbing or descending at a point in time during the procedure such that it will achieve the new altitude by the end of the procedure. If this option is not selected, then the aircraft will begin climbing or descending to the specified altitude immediately.
|
| Start Arc Alt
| The altitude of the aircraft at the beginning and end of the arc, if you are not using the default cruise altitude of the aircraft. The altitude is constrained by the lowest ceiling value of the active performance models in the current mission phase. |
| Stop Arc Alt
|
Arc Options
| Parameter | Description |
|---|
| Turn Direction
| Select the turn direction of the arc from the start bearing.
|
| Start Bearing
| The bearing, from the site, where you want the aircraft to begin flying the arc. Specify a True or Magnetic north reference using the drop-down menu. For example, if you specify a Start Bearing of 180 degrees, the aircraft will begin the arc at a point that is due south of the site (and at a distance from the site that is equal to the Radius parameter). |
| Radius
| The radius of the circle.
This will be the distance that the aircraft maintains from the site as it flies the arc. |
| Turn Angle
| The length of the arc that the aircraft will fly, measured from the start bearing. For example, if you specify a Turn Angle of 90 degrees from a Start Bearing of 0 degrees, the aircraft will fly an arc that transits the northeast quarter of the circle around the site, ending at a point that is due east of the site. |
| Join Arc
| Select from the following options: - Outbound - The aircraft begins the procedure on a course away from the site, on the start bearing, and then turns to join the arc.
- On - The aircraft begins the procedure on the arc at the start bearing. This option may be required (and the field grayed out) depending on a number of factors in the procedure's definition and the aircraft's performance models.
- Inbound - The aircraft begins the procedure on a course towards the site, on the start bearing, and then turns to join the arc.
This field is inactive if the airspeed of the aircraft is too high to provide enough room to make a turn with the specified radius and arc angle. |
| Exit Arc
| Select from the following options: - Outbound - The aircraft leaves the arc on a course away from the site, on the stop bearing.
- On - The aircraft arrives at the stop bearing on a in the direction of the arc. This option may be required (and the field grayed out) depending on a number of factors in the procedure's definition and the aircraft's performance models.
- Inbound - The aircraft leaves the arc on a course towards the site, on the stop bearing.
This field is inactive if the airspeed of the aircraft is too high to provide enough room to make a turn with the specified radius and arc angle. |
Arc Cruise Airspeed
Arc Cruise Airspeed parameters define the airspeed performance characteristics of the aircraft during the arc segment of the procedure.
Table - Arc Cruise Airspeed Parameters
| Parameter | Description |
|---|
| Airspeed Type | Select the method for determining the airspeed from the following options: - Minimum Airspeed - constant airspeed at the minimum cruising airspeed for the aircraft.
- Max Endurance Airspeed - variable airspeed that maximizes the length of time that the aircraft can remain in flight.
- Max Range Airspeed - variable airspeed that maximizes the distance that the aircraft can fly.
- Max Performance Airspeed – a custom performance airspeed and fuel flow that you can use to model specific flight conditions.
- Maximum Airspeed - constant airspeed at the maximum cruising airspeed for the aircraft.
- Other Airspeed - constant, manually defined airspeed.
With the exception of Other Airspeed, the actual airspeed will be defined by the currently selected cruise performance model, or possibly by the currently selected climb or descent performance model if the aircraft is climbing or descending. |
| Airspeed | Displays the airspeed. If the airspeed type is Other Airspeed, enter the desired airspeed value; otherwise, the calculated value will be displayed and cannot be edited. Select a reference from the drop-down menu - true airspeed (), calibrated airspeed (), equivalent airspeed (), or number. |
Enroute Options
Enroute Options define maneuvering performance characteristics of the aircraft during enroute segments of the procedure.
Table - Enroute Options Parameters
| Option | Description |
|---|
| Delay Enroute Climbs and Descents
| Select this check box to have the aircraft begin climbing or descending at a point in time during the procedure such that it won't achieve the new altitude until the start of the arc or pattern, or until it has reached the procedure site (whichever is applicable to the specific procedure). |
| Use Max Speed When Computing Turn Radii | Select this check box to force the aircraft maintain its cruise speed when turning, even if doing so will result in the aircraft making a turn large enough that it takes longer to complete than it would complete a slower, smaller turn. |
| Turn Factor
| The Turn Factor is the maximum amount - expressed as a multiplier - that the turn radius will be increased to minimize the bank angle required to complete the turn. The factor is applied only to turns that are performed enroute to the procedure's first control point. The full circles that correspond (or are tangent) to the start/stop turns at the extended radius may not intersect if the factor is set high enough. This parameter is a limit and may not actually be achieved due to the requirement to generate an appropriate turn sequence. You can adjust the slider or enter the value manually in the box, with the minimum value being 1 and the maximum value being 10. |
Enroute Cruise Airspeed
Enroute Cruise Airspeed parameters define the airspeed performance characteristics of the aircraft during enroute segments of the procedure.
Table - Enroute Cruise Airpseed Parameters
| Parameter | Description |
|---|
| Airspeed Type | Select the method for determining the airspeed from the following options: - Minimum Airspeed - constant airspeed at the minimum cruising airspeed for the aircraft.
- Max Endurance Airspeed - variable airspeed that maximizes the length of time that the aircraft can remain in flight.
- Max Range Airspeed - variable airspeed that maximizes the distance that the aircraft can fly.
- Max Performance Airspeed – a custom performance airspeed and fuel flow that you can use to model specific flight conditions.
- Maximum Airspeed - constant airspeed at the maximum cruising airspeed for the aircraft.
- Other Airspeed - constant, manually defined airspeed.
With the exception of Other Airspeed, the actual airspeed will be defined by the currently selected cruise performance model, or possibly by the currently selected climb or descent performance model if the aircraft is climbing or descending. |
| Airspeed | Displays the airspeed. If the airspeed type is Other Airspeed, enter the desired airspeed value; otherwise, the calculated value will be displayed and cannot be edited. Select a reference from the drop-down menu - true airspeed (TAS), calibrated airspeed (CAS), equivalent airspeed (EAS), or Mach number. |
Enroute Turn Direction
Enroute Turn Direction parameters define the direction that the aircraft will turn during enroute segments of the procedure.
Table - Enroute Turn Direction Parameters
| Parameter | Description |
|---|
| First Turn | The direction of the turn made from the end of the previous procedure as the aircraft sets its course toward the procedure site. Select from the following options: - Automatic - STK's Aviator capability will determine the direction of the turn.
- Turn Left - Specifies a left turn.
- Turn Right - Specifies a right turn.
|
| Second Turn | The direction of the turn made to achieve the outbound course at the procedure site. Select from the following options: - Automatic - Aviator will determine the direction of the turn.
- Turn Left - Specifies a left turn.
- Turn Right - Specifies a right turn.
|
