B 737- 300 FMC

First introduced on the 200Adv, the Flight Management Computer (FMC) was a huge technological step forward. Smiths Industries from the UK has supplied all FMC's installed on the 737. Most aircraft have just one FMC, but there is an option for two which is usually for operators into MNPS airspace eg Oceanic areas. The photograph left is of the Control Display Unit (CDU), which is the pilot interface to the FMC. There are 2 CDU's. The collective name for the FMC, autopilot & flight director, autothrottle and IRS's when used as one integrated system, is the Flight Management System (FMS). The FMS can be defined as being capable of four dimensional area navigation (latitude, longitude, altitude & time) while optimising performance to achieve the most economical flight possible. The heart of the FMS is the FMC which performs navigational and performance computations and control and guidance commands. The FMC eliminates many routine tasks and manual computations previously performed by pilots. In its most basic form, the FMC has a 96kb database, this was increased to 192kb on newer 737-3/4/500's and is now at 3.5 Mega-words for the 737-NG with Update 10.4. The database is used to store route information which the autopilot will fly when in LNAV mode. When given a ZFW & MACTOW, it takes inputs from the fuel summation unit to give a gross weight and best speeds for climb , cruise, descent, holding, approach, driftdown etc. These speeds can all be flown directly by the autopilot & autothrottle in VNAV mode. It will also compute the aircrafts position based upon inputs from the IRS's and radio position updating.