Definition
A device connected to the aircraft's static pressure system that converts the airplane's pressure altitude into a digital code, which the transponder then transmits to ground radar and other equipment so the aircraft's altitude can be displayed to air traffic control.
Plain English
A small box that reads the airplane's altitude and turns it into a signal the transponder can send out, so controllers on the ground can see how high the aircraft is flying.
Context Anchor
Seen in transponder, traffic display, and Traffic Information System discussions, especially when the aircraft must report altitude to support traffic awareness.
Derivation
"Encoder" comes from the idea of converting information into code. Here, the device takes a continuous altitude reading and codes it into discrete digital signals the transponder can broadcast.
Why Pilots Care
Gives controllers accurate altitude data without voice calls, supporting traffic separation and reducing collision risk.
Intuition Check
Do not assume an altitude encoder is just an altitude display. It does not show height to the pilot; it converts the aircraft’s pressure-based altitude into a coded signal for other systems.
Example Sentence 1
During the preflight check, the pilot confirmed the altitude encoder was reporting the correct field elevation to the transponder.
Example Sentence 2
With the altitude encoder connected, the transponder automatically reported the aircraft's height to ATC.