All About VOR Checks

| August 9, 2020 | By: Severe VFR
Copilot wing view over grass lands

A VOR receiver check is performed by the pilot or ground crew to verify a VOR receiver's accuracy.

Over time a VOR receiver's accuracy will decrease due to the deterioration of the receivers' Automatic Gain Control and Modulation circuit.

A pilot can determine if a VOR receiver can still be used for navigation by performing a VOR receiver check.

When Is A VOR Check Required

Only aircraft that intend to use the VOR receiver while operating under IFR must receive a VOR check. 

Operating IFR requires the VOR system to be:

  • Maintained, check, and inspected under an approved procedure; or
  • Operationally checked within the preceding 30 days, and was found to be within the permissible error limits.

Types Of VOR Checks

Multiple methods of performing a VOR check exist. Each method allows a different degree of inaccuracy in the receiver. Each method, except for the repair station method, can be performed by the pilot. These methods are:

  • Repair Station
  • VOT
  • Ground Checkpoint
  • Airborne Checkpoint
  • Dual VOR

Repair Station

The repair station method is a VOR check performed by an FAA-operated or appropriately rated radio repair station. The repair station method is the only VOR check not performed by the pilot.

Because a repair station completes this test, the pilot does not play any role in performing this type of VOR check.

This method has a maximum error of 4 degrees.

VOT

A VOT is an FAA VOR test facility (VOT). A VOT transmits a test signal, which provides users a convenient means to determine the operational status and accuracy of a VOR receiver while on the ground at VOT locations. Unlike standard VOR's that transmit all 360 radials, a VOT only transmits the 360-degree radial in all directions. Its morse code identifier is either a series of dots or a continuous tone. 

While the VOT method is a ground-based VOR check, airborne use of VOT is permitted. However, its use is strictly limited to the areas/altitudes authorized explicitly in the chart supplement.

To perform a VOT test:

  1. Tune in the VOT frequency on your VOR receiver.
  2. Identify the VOT
  3. Center the Course Deviation Indicator (CDI)
  4. Read the degree setting under the Omni-Bearing Selector (OBS).

The CDI should center on the 0-degree radial with a "from" flag or the 180 degree radial with a "to" flag.

The CDI must center within 4 degrees of the selected radial, I.E., between 356-004 or 176-184 degrees, with the correct flag to pass this test.

Suppose your receiver also has a Radio Magnetic Indicator (RMI). In that case, the RMI will read 180 degrees regardless of the radial setting on the OBS.

This method has a maximum error of 4 degrees.

Ground Checkpoint

The ground checkpoint method consists of certified radials received at specific locations on an airport's surface marked with the symbol shown above. 

The only difference between a VOT and a ground checkpoint is that ground checkpoints use VORs instead of VOTs. Ground checkpoints also require the pilot to tune the OBS to a specific VOR radial rather than the 180 or 0 degree radial with a VOT. 

To use a ground checkpoint:

  1. Position the aircraft on the ground checkpoint symbol on the airport surface. Make sure to come to a complete stop.
  2. Identify the VOR
  3. Center your VOR's CDI.
  4. Reference the OBS setting to the published OBS setting.

For your VOR to pass, it must have a centered CDI within 4 degrees of the published OBS setting.

This method has a maximum error of 4 degrees.

Airborne Checkpoint

VOR airborne checkpoints consist of certified radials received at specific locations and altitudes. 

Typically airborne checkpoints are found over prominent landmarks at low altitudes. 

To use an airborne checkpoint:

  1. Identify the VOR
  2. Position the aircraft at the correct altitude and over the landmark listed in the chart supplement.
  3. Center your VOR's CDI
  4. Reference the OBS setting to the published OBS setting.

If a pilot is not near a published Airborne Checkpoint while in flight:

  1. Select a VOR radial that lies along the centerline of an established VOR airway
  2. Identify the VOR
  3. Select a prominent ground point along the selected radial, preferably more than 20 nautical miles from the VOR ground facility, and maneuver the aircraft directly over the point at a reasonably low altitude
  4. Center the CDI
  5. Note the VOR bearing indicated by the receiver when over the ground point.

The maximum error for both tests is 6 degrees.

Dual VOR

The Dual VOR method requires your aircraft to have two VOR systems that operate independently of each other with a shared antenna.

This test is completed by tuning both VOR receivers to the same VOR and comparing the OBS setting to the other with the CDI centered. 

To perform a dual VOR test:

  1. Tune both VOR receivers to the same VOR.
  2. Identify the VOR
  3. Center the first receiver's CDI and note the OBS setting.
  4. Center the second receiver's CDI and note the OBS setting.
  5. Compare both OBS settings to each other.

For your VOR system to pass, it must have both CDI's center within 4 degrees of each other.

This method has a maximum error of 4 degrees

Locating VOR Checkpoints

To locate a VOR checkpoint, look in the back of your areas chart supplement.

The VOR Reciever Checkpoints and VOR Test Facilities page includes all VOR receiver airborne and ground checkpoints plus VOT facilities for the state listed.

These pages identify the checkpoints airport name, frequency, and identifier. These pages also state whether the test is a ground or airborne checkpoint with the corresponding altitude, radial, distance from the VOR or VOT, and remarks regarding the checkpoints description.

Logging A VOR Check

The final step in performing a VOR check is making a note in the aircraft logs or other record-keeping devices. To log a VOR check record the following information:

  • The date the test took place
  • The VOR or VOT used to perform the check
  • The amount of error
  • The pilots signature
Newest
Cockpit View Over Southern Wisconsin
Domains Of Learning
The domains of learning provide a framework for instructors to teach within the cognitive, affective, and psychomotor domain.
September 7, 2021
Copyright © Severe VFR LLC 2021.  All Rights Reserved.
linkedin facebook pinterest youtube rss twitter instagram facebook-blank rss-blank linkedin-blank pinterest youtube twitter instagram