Arc Point to Point

An Arc Point to Point 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 to view a detailed diagram...

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.
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 heading The direction that the aircraft is pointing. 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 ParametersClosed

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 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.

Enroute Options

Enroute Options define the turning performance characteristics of the aircraft during enroute segments of the procedure.

Table - Enroute Options ParametersClosed

Option Description
Use Max Speed When Computing Turn Radii Select this check box to force the aircraft to 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 ParametersClosed

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 ParametersClosed

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.

Airspeed Profile

Select a method for attaining the procedure's cruise airspeed from the following options:

  • Fly cruise airspeed profile (immediate change) - the aircraft adopts the selected cruise airspeed at the beginning of the procedure
  • Arrive on cruise airspeed (gradual change) - the aircraft begins accelerating or decelerating in the previous procedure so that it arrives at the beginning of the procedure at the selected cruise airspeed.

Vertical Plane Options

Vertical Plane Options parameters define the flight path angle of the aircraft during enroute and arc segments of the procedure.

Parameter Description
Start Arc FPA The pitch angle of the flight path at the beginning of the arc.
Stop Arc FPA The pitch angle of the flight path at the end of the arc.
Radius Factor The Radius Factor is the maximum amount - expressed as a multiplier - that the radius of a vertical curve will be increased to minimize the flight path angle required to complete it. The full circles that correspond (or are tangent) to the start/stop curves at the extended radius may not intersect if the Radius Factor is set high enough. This parameter is a limit and may not actually be achieved due to the requirement to generate an appropriate curve 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.
Min Enroute FPA The minimum pitch angle of the flight path during enroute segments of the procedure.
Max Enroute FPA The maximum pitch angle of the flight path during enroute segments of the procedure.