Definition
A ground-based radio transmitter that broadcasts a single, fixed omnidirectional signal used to check the accuracy of a VOR receiver in the aircraft. When tuned to the published VOT frequency, a properly functioning VOR receiver will indicate the 360° radial FROM the station, or the 180° radial TO the station, regardless of the aircraft's actual position on the airport. The receiver is considered acceptable for IFR use if the indicated bearing is within ±4° of these values.
Plain English
A test signal at certain airports that lets a pilot confirm the aircraft's VOR navigation receiver is reading correctly before flying on instruments. Tune it in, and the instrument should show a specific known reading. If it does, the receiver is good to use.
Context Anchor
Seen during required VOR accuracy checks before instrument flight, especially in the Instrument Procedures Handbook and airport facility listings.
Derivation
VOT stands for VOR Test. The 'T' simply marks it as a test source rather than a navigation station. VOR itself comes from 'VHF Omnidirectional Range' — a navaid that transmits signals in every direction.
Why Pilots Care
Confirms the VOR receiver is within allowable error limits before relying on it for instrument navigation.
Analogy
A VOT is like using a known weight to check a scale. If the scale does not show the known value, you should not trust it for important measurements.
Intuition Check
Do not treat a VOT like a normal VOR station for navigation. It is a fixed test signal used to check the receiver’s accuracy.
Example Sentence 1
Before the IFR departure, the pilot tuned the VOT frequency, centered the CDI, and confirmed the receiver indicated 180° TO within tolerance.
Example Sentence 2
After an avionics shop visit, the crew performed a VOT check before the next instrument flight.