747-400 dual FMC fail.

[kuobin]

Just wondering If dual FMC fail. Is L-NAV function still available ?

[Telekon]

LNAV is not available in the case of dual FMC failure. (Most) active RTE legs are retained by the CDU alternate navigation function at the time of failure and will display on the respective ND. However no steering commands are generated so you'd have to fly it in HDG SEL or similar.

[kuobin]

If we can only use HDG mode to track the route displayed on ND, are we still meet the RNP10 requirement?
personally, I think if we lost both FMC. we lost RNAV capability and eventually, we are not able to meet the requirement.

[Intruder]

At least 1 FMC is required for RNP 10.

[eckhard]

You do however retain Cat3 No DH Autoland capability.