L-1011 Flight Controls: YAW SAS in Parallel (27-31)

Parallel mode provides runway alignment, rollout guidance, and engine out go-around capability during autopilot operation. Parallel mode is different in the the rudder pedals are now connected through the servo and the pilot receives rudder movement feedback. The YAW SAS system now also has the same authority as the Pilot or 30º. Manual inputs may be applied through the rudder pedals to override the servo, but ruder pedal forces will be approximately one hounded pounds of pressure or more. 

L-1011 Flight Controls: YAW SAS in Series (27-30)

As described in the last posting, the YAW SAS has two modes of operation. The firs tis called "series" and provides full time yaw damping and turn coordination (yes, once you fly the big guys you can forget the "step on the ball" rule your flight instructor hammered into your head ... just kidding). Series means that the YAW SAS system is providing electric inputs to the rudder servo, but motion is not supplied to the rudder pedals - they remain in neutral. Manual inputs may be applied through the rudder pedals to override the servo with normal pedal forces. 

As noted in Controls and Indicators, two channels of YAW SAS are provided for redundancy. The switch lights are on the FCES panel. Series YAW SAS has 8º of rudder authority.