BFF CL Software - Short User Guide


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8. Auto-Pilot Position Following

When the FS9/X or X-Plane NATIVE auto pilot is engaged the system will drive the elevator and aileron axes to follow the movement of the AP control actions. When the AP is disengaged force feedback and flight control will be returned to the controls.

Unless specific special arrangements are made the CL software will not be able to recognise 3rd party A/P systems and so will not be able to activate the A/P following behaviours.

To disable AP following mode manually set Tab 4 Item 1 - APF_Enable parameter to zero. The scaling of the AP following movement can also be adjusted using Tab 4 Items 2, 3 & 4.

NOTE - when this AP following is active the CL software fully disengages the control axis inputs from the flight sim via FSUIPC. So control movements applied to the controls have no effect on the flight sim whilst AP following is active. When AP is disengaged the CL software re-engages the controls.

V9.7+ adds the capability to disengage AP by moving the controls when they are in AP-following mode. The sensitivity of the disengage movement threshold is set in Tab 4 Items 13, 14 & 15.

(For systems NOT using pot-less mode the “Zero” button can be used to run the automatic zero-finding procedure by which the system can determine the accurate zero position of the controls (as seen by the brushless driver cards). This more accurate zero position allows a more accurate assessment of the actual positions of the controls and so allows more sensitive movement dis-engage thresholds to be set.)

AP position following uses a closed loop position control PID algorithm implemented within the BLDRV-12/24 drives. The PID settings are specified in Tab 4 Items 16 to 24. The BFF_Driver_Test program can be used to tune for suitable PID settings. CARE is required when adjusting the PID settings as incorrect settings can cause unstable movement of the controls.

The maximum force levels in position following mode are capped internally by the BLDRV-12/24 card programming. The cap levels can be raised if your controls are heavy and require larger forces to move than the default levels. This will require re-programming of the BLDRV-12/24 cards - please contact me for information and instructions should you wish to do this.

NOTE – the internal AP operation of FSX/9 does not use full elevator/aileron actions to control the aircraft. Because of the this it is difficult to determine where the “real” elevator position should actually be when the AP is disengaged. A sudden pitch movement may therefore occur when control is retuned to the yoke.

Update - In version 1.07 of the CL software automatic adjustment of the elevator trim during AP following can be enabled for systems in which buttons are used for trim input. It  automatically adjusts elevator trim during A/P following so keep the elevator force in balance so minimising snatch on A/P disengage.

The feature also provides a similar function for potentiometer trim input systems - however this requires additional external hardware.

Update - In V1.210 Heavy Jet Mode 1 is introduced - this changes the way in which A/P following is implemented for the elevator axis when the mode is active. See the above link for details.... elevator trim is used as the A/P control action for pitch control, and the elevator position is left stationary.


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