FMC and CDU software, 747
Could any kind soul tell me what the story is with FMC and CDU interchangeability on a 747-400? The centre CDU doesn't fill any of the FMC functions, only ACARS. Does it have a different software load as a result, rendering it unusable as a hot spare down-route? Can it be reconfigured? Is the hardware different?
Many thanks.
B