DW
There's no "TURB" switch on the Airbus FBW series autopilot as far as I'm aware, but the established procedure seems to be to engage the "Mach/Speed" mode when encountering turbulence, as it monitors airspeed much more strictly - discussed here:
At least for the A330 / 340 series, which we are discussing here, you are dead wrong.
LHTTM TURBULENCE DAMPING FUNCTION (bolding by me)
General
The purpose of the Turbulence Damping Function implemented in the Electrical
Flight Control System is to damp the structural modes induced by atmospheric
turbulence.
Architecture
The Turbulence Damping Function consists of two lanes:
Longitudinal lane
The longitudinal Turbulence Damping command is computed by the FCPC1
(FCPC2 as a redundancy) as a function of the Nz accelerometer information.
It is added to the normal law command and transmitted to the
associated elevator servo-controls.
Rear lateral lane
The rear lateral Turbulence Damping command is computed by the FCPC1
(FCPC3 as a redundancy) as a function of the informationof a specific Ny
accelerometer located at the rear bulkhead level.
It is added to the normal law command and transmitted to the
associated yaw damper.
Specific equipment
The equipment specific to the Turbulence Damping Function are:
- the TURB. DAMP pushbutton switch
- the Ny front accelerometer
- the Ny rear accelerometer.
If not convinced, search for it in this doc
Airbus overhead panel description (you have to download the doc) on page 14
system knowledge........?
franzl