In a modern glass cockpit the Multifunction Control and Display Unit (MCDU) is the device that acts as the main interface between the flight crew and the Flight Management and Guidance Computer (FMGC). Each panel pairs a liquid-crystal display with a keypad through which a pilot can enter and modify flight plans directly into the Flight Management System (FMS), as well as insert engine thrust ratings and any other data the mission demands. Instant read-outs of time elapsed, time to go, extensive fuel-consumption figures, plus fuel information enable crews to eliminate unnecessary fuel stops as they monitor the progression of the flight. Besides navigation management, the identical left and right units found in the A320 serve as the control head for the radios and host communications via ACARS, seamlessly linking the flight deck with Satcom NextGen CNS/ATM or traditional voice networks. This consolidation of functions reduces pilot workload, saves time and money, and ultimately provides increased safety in all phases of operation.
What is MCDU in aviation?
A Multipurpose Control and Display Unit serves as the heart of an aircraft's Flight Management System (FMS). MCDU includes a liquid-crystal display which allows a pilot to enter and modify flight plans, and it presents flight information like fuel consumption, time elapsed, and time to go. MCDU is the user interface through which pilots interrogate and command the Flight Management Guidance Computer (FMGC). In Airbus cockpits the same hardware is often called the Multipurpose Control & Display Unit, yet its function remains identical.
Through the MCDU the flight crew enters the company route or an ICAO city pair, builds the lateral flight plan by inserting waypoints, and builds the vertical plan by defining target altitudes and speeds. The unit collects the performance data the FMGC needs for automatic airplane guidance: Zero Fuel Weight, Zero-Fuel Center of Gravity, wind speeds for climb, cruise, descent and approach, plus QNH and temperature at the destination. The FMGC in turn uses these inputs to generate the climb and descent profiles and to provide continuous lateral and vertical guidance, with the MCDU acting as the two-way gateway between pilot and computer.
What is the difference between MCDU and FMS in aviation?
The difference between MCDU and FMS is that FMS is the broader system concept consisting of two Flight Management Computers supplied with electrical power and hosting navigation databases, sensors, receivers, and computers. The FMS supplies all generated data, command line entries, and performance data, compares the current location with the desired flight path, and calculates flight-path predictions using origin-to-destination course, cost index, predicted cruise winds, constraints at waypoints, and gross weight. It provides LNAV and VNAV guidance, commands steering to autopilot and flight director, and offers a flight management function to the crew for flight planning, navigation, performance management, and progress of the current flight.
The MCDU is only the Multifunction Control and Display Unit driven through two units installed in the left and right side of the forward pedestal. It displays the data the FMS supplies and allows pilots to enter command line inputs. Independent Control & Displays let pilots compare both FMS/FMC independently and manually select which to use if one fails, while the FMS functionality is calculated by pilot input within the MCDU. Thus, the MCDU is the interface, the FMS is the system that does the calculating and guiding.
What is the difference between MCDU and CDU in aviation?
The difference between MCDU and CDU lies mainly in terminology and hardware evolution. CDU, Control Display Unit, is the pilot interface to the FMC on many Boeing aircraft. It incorporates a small screen and keyboard, employs left and right line-select keys, includes dedicated function keys, and incorporates alphanumeric keys for data entry. The baseline CDU uses a 14-line by 24-character display, whereas the actual CDU uses a 14-line by 24-character display. CDU provides redundancy: operators will have two CDU units installed for redundancy, so if one CDU fails the other can handle all FMC tasks.
MCDU, Multifunction Control and Display Unit, is the Airbus term for the same device, but the label hints at added capability like ACARS or ATSU access. Both CDUs used the same underlying functionality, so the distinction is largely brand-specific: on Boeing it is called CDU, while on Airbus it is MCDU. Either way, the unit enables the flight crew to interact with the FMC and gives the pilot up-to-date information, and the presence of two units ensures continuous operation even after single-unit failure.
Expert behind this article
Jim Goodrich
Jim Goodrich is a pilot, aviation expert and founder of Tsunami Air.
