Definition
A Flight Management System is an integrated airborne computer system that automates a wide range of in-flight tasks, including navigation, flight planning, performance management, and guidance of the aircraft along a programmed route. It combines inputs from multiple navigation sources (such as GPS, inertial reference systems, and ground-based radio aids), uses an internal navigation database of waypoints, airways, airports, and procedures, and provides outputs to the autopilot, flight director, and cockpit displays so the aircraft can fly a preprogrammed route accurately and efficiently.
Plain English
It is the aircraft's main onboard computer for flying the planned route. The pilot enters the route, and the system figures out where the aircraft is, where it should go next, and how to get there, then feeds that information to the autopilot and the cockpit displays.
Context Anchor
Seen in instrument flying when entering a route, selecting procedures, checking flight progress, or using cockpit displays for navigation guidance.
Derivation
The name describes the function plainly: a system that manages the flight. 'Manage' comes from the Italian maneggiare, meaning to handle or direct. The FMS handles the routine work of running the flight so the pilots can supervise and make decisions.
Why Pilots Care
It reduces workload, improves route accuracy, and helps manage complex departures, arrivals, and fuel planning.
Analogy
An FMS is somewhat like a car navigation system, but for an aircraft and with more flight-specific planning. It can guide the route, but the pilot must still check that the route and instructions are correct.
Intuition Check
Do not assume an FMS makes decisions for the pilot. It manages and displays flight information based on what it is given; the pilot remains responsible for checking it and flying the correct plan.
Example Sentence 1
Before pushback, the crew loaded the full flight plan into the FMS, including the departure procedure, route, and expected arrival.
Example Sentence 2
After ATC changed the clearance, the pilot updated the FMS so it could provide new guidance.