kite
When both engines are operational on a CAT III B (dual) approach they remain split even following an electrical failure on one side.
er.. I don't think so. The Bus Ties have to be open for CAT 3 DUAL capability. If a GEN fails the Bus Ties close and the a/c downgrades to CAT 3 SNGL. (If the electrical system were to remain split half the ship would be electrically dead).
If the failure happens below Alert Height (100' RA) the FMA's continue to display CAT 3 DUAL and there are no operational consequences.
One cautionary note: following an engine failure and an APU running, the System Display (SD) ELEC page appears to show the two sides split. This is just for representational purposes and if a failure occurred on one side the tie would connect the failed side to the remaining generator.
It's not just representational, it's true! If you have any two GEN available AC BUS 1 and 2 are electrically split, with either one or two Bus Ties open. With only one GEN available both Bus Ties close, linking AC BUS 1 and 2.
TP