Advanced Acceleration

The Advanced Acceleration performance model is comprised of a set of parameters that define the flight characteristics of the aircraft when accelerating and is mapped to the physical properties of the aircraft that are currently defined in the Advanced Fixed Wing Tool.

Parameters

There are four parameter groups for the Advanced Acceleration performance model apart from the properties that it derives from the Advanced Fixed Wing Tool - Level Turns, Climb and Descent Transitions, Attitude Transitions, and Acceleration.

Level Turns

The values specified for these parameters are the level turn values for the aircraft. STK's Aviator capability adheres to these values when possible, but in procedures where the turn is non-level the values may be adjusted to maintain the correct relationship between these interrelated parameters. Select one parameter to manually define; the other parameters are calculated relative to the parameter that you specified.

Table - Level Turns ParametersClosed

Field Description
Turn G The standard G force of the aircraft in a turn.
Bank Angle The standard bank angle of the aircraft in a turn.
Turn Acceleration The standard acceleration of the aircraft in a turn.
Turn Radius A fixed turn radius that is independent of the aircraft's speed.
Turn Rate The standard turn rate.

Accel Maneuver Mode Field

You can toggle if the aircraft turn or push/pull calculations use atmosphere density scaling. Alternatively, you can define specific parameters used in the turn calculation for more realistic results.

Table -Accel Maneuver Mode OptionsClosed

Select the Constant Value option to have turns or push/pull calculations use a constant value for G, Radius, Rate, BankAngle, HorizAccel.

Select the Scale by atmosphere density option to have turns or push/pull calculations use a density-scaled value for G, Radius, Rate, BankAngle, HorizAccel. Altitude is the only parameter that drives the scaling.

Select the Aero/Prop maneuver mode option to:

  • Have turn calculations use a fraction of max performance, limited by the value specified for Turn G, Radius, Rate, BankAngle, HorizAccel.
  • Have basic push/pull calculations use the fraction of max performance, limited by the load factors specified at the top level.
  • Have advanced push/pull calculations use what is left over after the horizontal accel is accounted for, limited by the load factors specified at the top level.

    Click the ellipsis ( ... ) button to open the Aero/Prop maneuver mode window (see below) to enter specific parameter details for the turn calculations.

Aero/Prop Maneuver Mode Window
Parameter Description
Mode

Specify if the Thrust and Lift Coefficient mode should be used in calculations or if only the Lift Coefficient mode should be used.

  • Use Lift Coefficient Only: A reference Lift Coefficient value is calculated based on the provided reference values. This lift coefficient is used at other points in the envelope to compute the maximum load factor to fly.
  • Use Thrust and Lift Coefficient: A reference Lift Coefficient, Specific Excess Power, and Drag Coefficient is calculated based on the provided reference values. STK's Aviator capability will attempt to maintain the same relative excess power when deviating from reference conditions.

If you select the Use Thrust and Lift Coefficient option, but the AeroProp capabilities are not configured, a message box appears. The message explains that to use this function, you need select the aero/prop models capable of computing:

  • lift
  • drag
  • thrust

Otherwise, only the lift coefficient will be used.
Flight Mode The Flight Mode to use for the maneuver. This determines the reference area when calculating the reference lift coefficient.
Use Afterburner A jet engine component that provides an increase in thrust by injecting additional fuel into the jet pipe, downstream of the turbine. An afterburner is usually employed in supersonic flight, certain takeoff scenarios, and in combat situations. if possible

Select the check box if you want to enable the aircraft to use an afterburner if it has one.
Reference Weight The weight used to calculate the reference value of the lift coefficient.
Reference Altitude The altitude used to calculate the reference values for dynamic pressure and lift coefficient.
Reference Airspeed The airspeed value and type used to calculate the reference values for dynamic pressure and lift coefficient.
Sustained Load Factor G The load factor to maintain during maneuver.
Control Authority

Use the slider to adjust the fraction of the maximum performance allowed between turn and push/pull.

Climb and Descent Transitions

The values specified for these parameters define the G force of transitions between climbing or descending and level flight.

Table - Climb and Descent Transitions ParametersClosed

Parameter Description
Max Pull Up G The force normal to the velocity vector used to transition into a climb or to transition out of a dive into the next flight segment. The minimum value is 1.05 G. Low values increase the likelihood of terrain impact when a procedure is defined with a high rate of descent close to the ground.
Max Push Over G The force normal to the velocity vector used to transition into a descent or to transition from a climb to the next flight segment. The maximum value is 0.95 G. High values increase the likelihood of exceeding the ceiling when a procedure is defined with a high climb rate at an altitude close to the ceiling.

Accel Maneuver Mode Field

You can toggle if the aircraft turn or push/pull calculations use atmosphere density scaling. Alternatively, you can define specific parameters used in the turn calculation for more realistic results.

Table -Accel Maneuver Mode OptionsClosed

Select the Constant Value option to have turns or push/pull calculations use a constant value for G, Radius, Rate, BankAngle, HorizAccel.

Select the Scale by atmosphere density option to have turns or push/pull calculations use a density-scaled value for G, Radius, Rate, BankAngle, HorizAccel. Altitude is the only parameter that drives the scaling.

Select the Aero/Prop maneuver mode option to:

  • Have turn calculations use a fraction of max performance, limited by the value specified for Turn G, Radius, Rate, BankAngle, HorizAccel.
  • Have basic push/pull calculations use the fraction of max performance, limited by the load factors specified at the top level.
  • Have advanced push/pull calculations use what is left over after the horizontal accel is accounted for, limited by the load factors specified at the top level.

    Click the ellipsis ( ... ) button to open the Aero/Prop maneuver mode window (see below) to enter specific parameter details for the turn calculations.

Aero/Prop Maneuver Mode Window
Parameter Description
Mode

Specify if the Thrust and Lift Coefficient mode should be used in calculations or if only the Lift Coefficient mode should be used.

  • Use Lift Coefficient Only: A reference Lift Coefficient value is calculated based on the provided reference values. This lift coefficient is used at other points in the envelope to compute the maximum load factor to fly.
  • Use Thrust and Lift Coefficient: A reference Lift Coefficient, Specific Excess Power, and Drag Coefficient is calculated based on the provided reference values. STK's Aviator capability will attempt to maintain the same relative excess power when deviating from reference conditions.

If you select the Use Thrust and Lift Coefficient option, but the AeroProp capabilities are not configured, a message box appears. The message explains that to use this function, you need select the aero/prop models capable of computing:

  • lift
  • drag
  • thrust

Otherwise, only the lift coefficient will be used.
Flight Mode The Flight Mode to use for the maneuver. This determines the reference area when calculating the reference lift coefficient.
Use Afterburner if possible

Select the check box if you want to enable the aircraft to use an afterburner if it has one.
Reference Weight The weight used to calculate the reference value of the lift coefficient.
Reference Altitude The altitude used to calculate the reference values for dynamic pressure and lift coefficient.
Reference Airspeed The airspeed value and type used to calculate the reference values for dynamic pressure and lift coefficient.
Sustained Load Factor G The load factor to maintain during maneuver.
Control Authority

Use the slider to adjust the fraction of the maximum performance allowed between turn and push/pull.

Always Ignore Flight Path Angle Check Box

When you are working at the design limits of an aircraft model, you may commonly encounter problems with:

  • pushing over at high path angles
  • pulling up at low flight path angles

For example, an aircraft flying at high altitude and high speed may not have enough control authority to push over as a procedure requires. Or, the aircraft may need to violate another constraint such as the procedure ceiling.

In these situations, you can select the Always Ignore Flight Path Angle check box to ignore load factor limits. This option enables you to suspend these limits without needing to change to the aircraft model that you are using.

Attitude Transitions

Aircraft attitude is determined using a 123 Euler angle sequence of Bank, Angle of Attack The angle between the body X axis and the projection of the velocity vector onto the body XZ plane. The velocity vector is the velocity of the object as observed in the object's central body fixed coordinate system., and Sideslip, originating from a velocity aligned, nadir constrained set of axes. Attitude rates may be violated in the case of very short - or zero distance - procedures.

Table - Attitude Transitions ParametersClosed

Parameter Description
Roll Rate The standard roll rate - the rate at which the aircraft bank angle changes - of the aircraft in a turn. When STK's Aviator capability violates the specified Turn Roll Rate, the probable cause is an unrealistic climb or descent model, or the use of climb, descent, level turn and speed change parameters that aren't well matched to the roll rate parameters of the aircraft.
AOA/Pitch Rate The pitch rate when transitioning between attitude modes, between procedures, and between uncoordinated maneuvers when necessary.
Sideslip/Yaw Rate The yaw rate when transitioning between attitude modes, either triggered by changes in the acceleration performance model or between takeoff/landing, normal flight, weight-on-wheels, or hover mode.

Acceleration

Field Description
Mode

Select an acceleration mode:

  • Max Accel - the rate of acceleration or deceleration will be the maximum possible for the aircraft.
  • Override G - specify below - the rate of acceleration or deceleration will be specified.
Accel G If you have selected the Override G mode, specify the rate of acceleration and deceleration in Gs.