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In the past, there were three VOR service volumes: Terminal, Low, and High. But in December of 2020, the FAA changed that. In this article, we'll explain the new VOR service volumes, and review the legacy ones.

Since 2016, the FAA has been decommissioning VORs across the US, as they move towards GPS related navigation systems.

The problem with this? The FAA still needs a network of VORs that can function in the event of a mass GPS outage. To solve the problem, the FAA came up with a concept called the Minimum Operational Network (MON).

Legacy VOR Service Volumes

1) Terminal

Terminal VORs, which have the smallest service volume, provide navigational services for the local area out to 25 NM, and from 1,000 feet up to 12,000 feet above the receiver. Terminal VORs are often co-located with airports.

2) Low

Low VORs provide navigational services out to 40 NM, and from 1,000 feet up to 18,000 feet above the transmitter.

3) High

High VORs provide greater range, but are more complex in their constraints. Starting at 1,000 feet above the station up to 14,500 feet, reception extends 40 NMs out. From 14,500 feet above the station to 18,000 feet you can expect 100 NMs of range. Then the highest range layer extends from 18,000 feet above the station to 45,000 feet. This layer can be reliably received up to 130 NM away. Finally, from 45,000 feet above the transmitter to 60,000 feet you can receive signal out to 100 NMs from the station.

New Service Volumes

Transmitter technology has improved, and these new service volumes are more capable, allowing the phasing out of select legacy VORs.

4) VOR Low (VL)

Just like legacy VORs, below 1,000 feet above the transmitter the signal is unreliable. From 1,000 feet above the station to 5,000 feet the signal reaches out 40 NMs. From 5,000 feet up to 18,000 feet the range is 70 NMs.

5) VOR High (VH)

This service volume has 5 layers, ranging from 1,000' to 60,000', with service volume distances ranging from 40 NM to 130 NM.

Identifying the type of VOR

The best way to determine the service volume of a specific station is to check the chart supplement. Find the navigation facility and check for the class in the parenthesis.

Knowing these service volumes helps you ensure that you have navigational coverage on your next flight. Also, remember that VOR stations are also limited by line of sight - something to keep in mind if you're flying near terrain.

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