Hi The Cav,
I don't know about the Classic, but the L1011 had an autopilot TURB mode (PFM). It worked really well and prevented large pitch excursions whilst chasing small deviations in altitude.
Pity AF447 didn't have one fitted.
"Turbulence mode provides pilot-assisted, constant attitude flight through turbulent air. The autopilot control authority is reduced in order to soften its response to attitude changes caused by the turbulence.
Turbulence is an autopilot mode only and cannot be selected unless an autopilot is engaged. The TURB mode may be selected any time either autopilot is in CWS or CMD and A/L TRACK or GO AROUND is not established. The TURB light will illuminated indicating mode selection. Verification of mode engagement is accomplished by checking for TURB legend on in both AFCS MODES annunciators. When turbulence is selected while the autopilot engage lever is in the CMD position, the solenoid held lever drops from CMD to CWS. This action essentially cancels all other modes.
No other mode can be selected while the turbulence mode is engaged. The turbulence mode can only be released by pressing the TURB switch a second time or by disengaging the autopilot. Either of these actions then, is a prerequisite to resuming normal autopilot-controlled flight after a turbulence encounter.
If a flight director is also on when turbulence is selected, its command bars will be biased out of view but no FD warning flag will appear. When TURB is canceled, the command bars will return if the FD switch was left on but it will have a new reference. The new reference is the attitude existing at the time of TURB cancellation since all previous modes were canceled when TURB was selected."
Last edited by rudderrudderrat; 7th September 2011 at 12:30.
Reason: copied text from http://l1011project.blog spot.com/2011/07/l-1011-autoflight-turbulence-mode-22-20.html