When I have talk of pioneer in fact I was thinking of fail-operational digital autopilot of L1011.
In actual fact, only the last few L1011's manufactured had digital autopilots, all the rest were dual channel fail-operational analogue design.
Sequence for automatic approach/land (autoland) with the L1011.
Only one autopilot is engaged for maneuvering, in heading mode, approaching the final approach course.
On that final intercept heading, the A/L switchlight is depressed, and at this time, the second autopilot is engaged.
The aircraft intercepts the final approach course, and continues inbound.
At 1500 feet agl or 25 seconds after glidepath interception, automatic approach land track is established.
The autopilot rudder channel reverts to parallel operation (rudder pedals move in response to autopilot inputs), and when flaps are selected to the landing flaps position, direct lift control (DLC) becomes operational.
During the final approach segment, a series of voting circuits constantly monitors all four autopilot channels, and will reject a faulty signal from one...or two.
In this case, a 'no dual' message appears, and the approach is continued to category two minima.
At 150 feet radio height, runway alignment begins.
At 50 feet radio height, the auto flare maneuver begins.
At 5 feet radio height, autothrust is disconnected.
Upon touchdown, autospoilers are actuated, and the airplane continues to track the localizer...right down the runway centerline.
In over 800 autolands with the L1011, I have only had to discontinue one...and that was due to a localizer transmitter ground failure.
L1011, a truly remarkable,
reliable airplane, for autoland operations.
in addition of engagement of autoland mode, I was also wondering how pilots were informed of selected Decision Height.
With category three operations, there is no decision height, only an alert height.
For category two autoland operations, the L1011 uses a decision height via the dual radio altimeters.