YAW/SAS
Provided,
*turn co-ordination
*yaw damping
*runway alignment
*runway rollout control, thru rudder actuation/rudder pedal steering.
The last two during automatic approach/land operations, using one or two dual channel autopilots
In twenty five years (and still counting) on the Lockheed tri-motor, no problems experienced whatsoever with roll/speed brake, MDLC, YAW/SAS, DLC or indeed any other control function.
A very reliable aeroplane, IF maintained properly.
Oh yes, hydraulic fusing, built in at the factory, to eliminate total hydraulic system loss due to system leaks.
So, no JAL (747) or UAL (DC10) total system loss nonsense.
And, but certainly not least, the only first generation wide-body jet aeroplane not lost due to a system failure/malfunction.
In addition, the first wide body certificated to CATIIIB right out of the box, thanks to a very few ex- HS Trident/Smiths folks...
Gosh, almost forgot, thanks to Rollers, stage three from the beginning, unrestricted.
One more, full authority FMS (if ordered) which provided RNAV/VNAV and thrust management, all in one very neat package, direct from Palmdale.