Originally Posted by
turbidus
The Autopilot is flying the aircraft. The FMC provides mach trim and speed trim, hence the comment about performing CAT III autoland W/O FMC is valid. (as long as the AP is fully functional)
The pilot will have to manually trim the ac if the FMC's are inop. and can still perform a CAT III autoland procedure.
Is the question how to manually trim the ac below 400' on final???
Ah you got some bogus info in there. Yes, you can do an auto land with no FMCs. That part is correct. However, the FMC has nothing to do with trimming for an auto land, so the trim will work just fine without the FMCs. Not sure where you are getting this info. The proof of the pudding is in the “auto land limitation summary” in the QRH. It lists all the equipment requirements, nowhere does it mention an FMC.