Definition
The keypad and screen used by the pilot to interact with the Flight Management System (FMS). It is the primary interface for entering the flight plan, selecting navigation sources, loading procedures, and viewing FMS data such as waypoints, fuel, and performance information.
Plain English
It is the small keyboard and screen the pilot uses to talk to the airplane's flight computer. The pilot types in the route, picks approaches, and reads back what the computer is doing.
Context Anchor
Seen in aircraft equipped with a flight management system, especially when pilots enter or review route and altitude information during instrument flight planning or in flight.
Derivation
FMS stands for Flight Management System. 'Control display unit' is descriptive: a unit that both controls (through its keys) and displays (through its screen). The phrase comes from cockpit equipment naming conventions where 'CDU' is a standard term for any keypad-and-screen interface.
Why Pilots Care
It is the primary way pilots input precise routes and procedures, directly affecting navigation accuracy and workload during instrument flight.
Intuition Check
Do not read this as the whole flight management system. The FMS control display unit is the pilot’s screen-and-control interface to that system.
Example Sentence 1
Before pushback, the captain entered the departure, route, and arrival into the FMS control display unit and asked the first officer to verify each waypoint.
Example Sentence 2
During the approach, the crew cross-checked the arrival waypoints on the FMS control display unit.