Covering all eventualities
Here's my understanding of it assuming no FFB (I'll edit in any corrections you have):
With FD mode off
In this mode the autopilot will always use up to 20% authority to dampen any motion that isn't due to pilot input (to stop the heli swinging like a pendulum due to shifts in momentum during by manouvering, or spinning to face wind direction).
Blue pitch button:
On - Default pitch for centred joystick is calibrated according to heli attitude when trimmer is tapped or released. Up to 20% authority used to return to this attitude as well as dampen any motion not due to pilot input.
Off - Default pitch for centred joystick is calibrating according to cyclic pitch input when trimmer is tapped or released. Up to 20% authority used only to dampen any motion not due to pilot input.
Holding the trim button down effectively flicks this to off, so manouvres should relate more closely to cyclic position.
Blue roll button:
On - Default roll for centred joystick is calibrated according to heli attitude when trimmer is tapped or released. Up to 20% authority used to return to this attitude as well as dampen any motion not due to pilot input.
Off - Default roll for centred joystick is calibrating according to cyclic roll input when trimmer is tapped or released. Up to 20% authority used only to dampen any motion not due to pilot input.
Holding the trim button down effectively flicks this to off, so manouvres should relate more closely to cyclic position.
Blue heading button:
On - Default heading for centred pedals is calibrated according to heli heading when trimmer is tapped or released. Up to 20% authority used to return to this heading as well as dampen any motion not due to pilot input.
Off - Yaw for centred pedals is calibrating according to rudder input when trimmer is tapped or released. Up to 20% authority used only to dampen any motion not due to pilot input.
Holding the trim button down effectively flicks this to off, so the heli shouldn't try to return to default heading under small rudder input.
With FD mode on
In this mode the autopilot will only use up to 20% authority to dampen any motion that isn't due to pilot input when the blue buttons are switched on (to stop the heli swinging like a pendulum due to shifts in momentum during by manouvering, or spinning to face wind direction).
Blue pitch button:
On - Default pitch for centred joystick is calibrating according to cyclic pitch input when trimmer is tapped or released. Up to 20% authority used only to dampen any motion not due to pilot input.
Off - Default pitch for centred joystick is calibrating according to cyclic pitch input when trimmer is tapped or released. No dampening so you'll have to manually correct for any pendulum-like swinging.
Holding the trim button down effectively flicks this to off, so you'll have to manually correct for any pendulum-like swinging while manouvering.
Blue roll button:
On - Default roll for centred joystick is calibrating according to cyclic pitch input when trimmer is tapped or released. Up to 20% authority used only to dampen any motion not due to pilot input.
Off - Default roll for centred joystick is calibrating according to cyclic pitch input when trimmer is tapped or released. No dampening so you'll have to manually correct for any pendulum-like swinging.
Holding the trim button down effectively flicks this to off, so you'll have to manually correct for any pendulum-like swinging while manouvering.
Blue heading button:
On - Yaw for centred pedals is calibrating according to rudder input when trimmer is tapped or released. Up to 20% authority used only to dampen any motion not due to pilot input.
Off - Yaw for centred pedals is calibrating according to rudder input when trimmer is tapped or released. No dampening so you'll have to manually correct for the effects of wind direction.
Holding the trim button down effectively flicks this to off, so you'll have to manually correct for the effects of wind direction while manouvering.
