747 FMC Failure
With the failure of the operating FMC LNAV and VNAV both drop out (struck through FMAs).
If the autopilot is in at the time of failure it remains engaged but in what modes? Is just an ATT mode? With LNAV and VNAV gone there will be no modes annunciated on the MCP. Obviously, selecting HDG and ALT HOLD puts one back "in charge" but I'm just curious to know what the autopilot is working on prior to reselecting modes.