Definition
A combined navigation receiver and indicator capable of displaying guidance from either a VOR (VHF Omnidirectional Range) station or a localizer transmitter, with the pilot selecting the appropriate frequency for the navigation aid in use. On an HSI, VOR/Localizer information is presented through the same course deviation indicator, with the instrument automatically interpreting the signal type based on the tuned frequency.
Plain English
One radio and one needle that can work with two different kinds of ground stations: VOR stations used for general navigation, and localizer transmitters used for lining up with a runway on an instrument approach. You pick which one by tuning its frequency.
Context Anchor
Seen on a Horizontal Situation Indicator, or HSI, when the pilot is using the display to follow either VOR course guidance or localizer approach guidance.
Derivation
VOR stands for VHF Omnidirectional Range — a station that sends signals in every direction so an aircraft can determine its bearing from it. Localizer comes from 'localize' (Latin locus, place) — it locates the aircraft laterally on the centerline of a specific runway. Combining them in one receiver reflects that both use overlapping VHF frequencies and similar cockpit displays.
Why Pilots Care
Most light aircraft have a single receiver and a single needle that does both jobs. Knowing whether you're tracking a VOR radial or a localizer course changes how the needle behaves — localizer needles are more sensitive and don't have a TO/FROM indication. Misreading which mode you're in can cause large tracking errors close to the ground during an approach.
Intuition Check
Do not read the slash as meaning the aircraft is using a VOR and a localizer at the same time. Here it means the display or receiver can work with either type of signal, depending on the selected navigation source.
Example Sentence 1
She tuned the VOR/Localizer receiver to 110.30 to pick up the ILS localizer for runway 27.
Example Sentence 2
With the HSI in VOR/Localizer mode, small corrections kept the aircraft on the final approach course.