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 A/P control actions. When the A/P 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 A/P following mode manually set Tab 4 Item 1 - APF_Enable parameter to zero. The scaling of the A/P following movement can also be adjusted using Tab 4 Items 2, 3 & 4.

NOTE - when this A/P 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 A/P following is active. When A/P is disengaged the CL software re-engages the controls.

V2+ includes the capability to disengage AP by moving the controls when they are in A/P-following mode. The sensitivity of the disengage movement threshold is set in Tab 4 Items 13, 14 & 15.

A/P position following uses a closed loop position control PID algorithm implemented within the BLDRV3 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 BLDRV3 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 adjusting the CL_SPU_USB EEPROM settings - thuis can be done using the Diver Test App.

NOTE – the internal A/P 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.

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 keeping the elevator force in balance and 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. The BFF Motorised Trim Wheel can be used to control elevator trim and provides smoother A/P disengage transitions.

Heavy Jet Mode 1 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 at mid.


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