Two Long Range
Navigation
Systems (LRNS) consisting of 2 x IRS and 2 x FMC is required for flying in MNPS airspace
Question:
is the above requirement fulfilled on a B-777 with double FMC fault?
In case of double FMC fault the system goes into Alternate Navigation mode,
LNAV is available and the auto pilot (or the crew) will fly the magenta line all the way to destination.
You still have the LEG and the PROG page available
The airplane still has 2 GPS's and multiple IRS's.
Since total accuracy is maintained I really can't see a reason for diverting.