Definition
A cathode-ray tube (CRT) or similar electronic screen used in avionics equipment to present information visually to the pilot, such as radar returns, navigation data, engine parameters, or flight instrument indications.
Plain English
The screen part of a cockpit instrument that shows information to the pilot, similar to a small television screen built into the panel.
Context Anchor
Seen in descriptions of older aircraft instruments, radar displays, and electronic test equipment.
Derivation
From 'display' (to show) and 'tube,' referring originally to the vacuum tube technology (cathode-ray tube) used to produce the image. The term persists even though many modern displays use flat-panel technology rather than actual tubes.
Why Pilots Care
The display tube is the visible part of an instrument the pilot reads in flight. If the tube fails or dims, the information behind it is unusable even though the underlying system may still be working.
Analogy
A display tube is like the picture tube in an older television: the electronics may be working behind it, but the tube is the part that creates the visible picture.
Intuition Check
Do not read “tube” as a hose or pipe here. In this context, it means an older electronic screen built inside a sealed tube.
Example Sentence 1
The weather radar display tube went dark, so the crew had no picture of the storm cells ahead.
Example Sentence 2
During preflight the technician confirmed the display tube showed a clear, bright image with no burn spots.