Definition
A maintenance data terminal (MDT) is a ground-based or panel-mounted device used by maintenance personnel to access, display, and download diagnostic and performance data recorded by an aircraft's onboard systems. It serves as the interface between the aircraft's data-recording computers and the technicians servicing the aircraft.
Plain English
A computer device that maintenance crews plug into the aircraft to read out what its systems have been doing, so they can troubleshoot problems and keep records.
Context Anchor
You may see MDT in aircraft manuals, maintenance write-ups, equipment lists, or acronym sections when aircraft maintenance information systems are being discussed.
Derivation
‘Maintenance’ comes from Latin manu tenere, ‘to hold in the hand’ — meaning to keep something in working order. ‘Data terminal’ is a computing term for a device at the end of a data link where information is read or entered. Together: the endpoint where maintenance information is accessed.
Why Pilots Care
Pilots don't operate the MDT, but the data it pulls — fault codes, exceedances, system trends — often determines whether an aircraft is released for the next flight. Anything a pilot logs as a squawk eventually meets the MDT on the ground.
Intuition Check
Do not read “terminal” here as an airport building. In this term, a terminal is a computer point where a person can access and work with information.
Example Sentence 1
After the flight, the technician connected the MDT to download the engine performance data from the previous leg.
Example Sentence 2
Before signing off the aircraft, the pilot checked the latest entries from the MDT.