Definition
A ground-based component of the Microwave Landing System (MLS) that radiates the signals used by an aircraft's airborne receiver to determine its vertical angle (glide path) on approach. It is typically located near the runway threshold and provides precision elevation guidance during the final approach segment.
Plain English
A piece of equipment on the ground beside the runway that beams up a signal telling the aircraft how high or low it is on its descent path toward landing.
Context Anchor
Seen in discussions of Microwave Landing System instrument approaches and the ground equipment that provides approach guidance.
Derivation
‘Elevation’ comes from the Latin elevare, meaning ‘to lift up,’ and in aviation refers to a vertical angle above the horizontal. ‘Transmitter’ comes from the Latin transmittere, ‘to send across.’ Together: the device that sends out the vertical-angle guidance signal.
Why Pilots Care
On an MLS approach, the elevation transmitter is what gives you your glide path information. If it's out of service, you lose vertical guidance and the approach minimums change or the approach may be unusable.
Intuition Check
Do not read “elevation” here as airport height above sea level. In this term, it means vertical approach guidance: the aircraft’s up-or-down position relative to the desired path to the runway.
Example Sentence 1
The MLS elevation transmitter was reported out of service, so the crew briefed an alternate approach.
Example Sentence 2
During the approach briefing the crew confirmed the elevation transmitter was operating normally.