Stick free the A320 series aircraft will essentially maintain 1G. However the auto-trimming may not be able to totally compensate for all pitching moments.
Since the FBW system is maintaining a 1G load rather than holding a specific pitch attitude, the Airbus has a number of interesting handling traits. If you happen to be hand flying in turbulent conditions, you will see the aircraft pitch up and down slightly as the FBW system attempts to maintain 1G in the vertical gusts. Some pilots, new to the Airbus, have mistaken this characteristic as an uncommanded pitch changes and made an unnecessary entry on the aircraft maintenance logbook.
When in a turn up to 33 degrees of bank, the FBW system will maintain the appropriate G load for the bank angle (i.e. 1.14G for a 30 degree bank). This minimizes the need for any pitch inputs during normal turns.
Another fascinating characteristic of the A320 series is due to the high resolution of the vertical accelerometers. When cruising at higher altitudes, the local force of gravity is slightly less than 1G. Since the FBW system is sensitive enough to discern this difference, the aircraft will slowly pitch up, in order to maintain 1G. The greater the altitude, the more pronounced the pitch rate. Even at FL390, this characteristic, while slightly annoying is easily controlled.
While I don’t have any experience on the A330/340, I have been told its FBW system is more sophisticated. On the A330/340, the system takes the aircraft altitude into account, and will reduce the stick free G load so the aircraft will not exhibit the minor pitch up tendency of the A320 series. Unfortunately, I don’t have any documentation regarding the A330. Possibly some of the pilots who fly the A330/340 could comment.
Best regards,
The Kid