VOT (VOR Test Signal)
A VOT (VOR Test Signal) is a special VOR test facility that transmits a 360° (FROM) signal on a specific VOR frequency, allowing pilots to check the accuracy of their airborne VOR receiver. When the OBS is set to 0° on a VOT, the CDI should centre with a FROM indication; when set to 180°, it should centre with a TO indication.
VOT Test Procedure
- Set the NAV receiver to the VOT frequency (published in the CFS for that aerodrome)
- Wait for the Morse code identifier — VOTs transmit a continuous tone with no identifier, or a specific code
- Set OBS to 0° — CDI should centre ± 4° with a FROM indication
- Set OBS to 180° — CDI should centre ± 4° with a TO indication
- Record the error in the maintenance log
IFR Accuracy Standard
For IFR operations, the VOR receiver must be tested within the preceding 30 days using an approved ground checkpoint, airborne checkpoint, or VOT. Maximum allowable error: ± 4° for a VOT or ground checkpoint; ± 6° for an airborne checkpoint. The test must be recorded in the aircraft’s maintenance log.