New VOR Service Volumes Published

The October 7, 2021 edition of the Aeronautical Chart Users’ Guide notes that IFR en route charts now show expanded VOR standard service volumes that are being implemented to support the minimum operational network (MON). That network is a key part of the FAA plan to reduce the number of ground-based navigation aids (for more information see Latest on VOR Decommissioning and related posts here at BruceAir).

The new ACUG includes the following note:

IFR ENROUTE CHARTS

Two new VHF Omnidirectional Radio Range (VOR) standard service volumes (SSV) have been implemented in order to achieve VOR service within 70 nautical miles above 5,000 feet above ground level (AGL). The new NAVAID codes are VOR Low (VL) and VOR High (VH). Along with that effort, two new distance measuring equipment (DME) SSVs of DME Low (DL) and DME High (DH) have been implemented to support DME-DME RNAV service. Legacy SSVs of Terminal (T), Low (L), and High (H) will continue to be maintained.

In the past, NAVAIDs at one location typically all had the same SSV. For example, a VORTAC typically had a High (H) SSV for the VOR, the TACAN azimuth, and the TACAN DME, or a Low (L) or Terminal (T) SSV for all three. A VOR/DME typically had a High (H), Low (L), or Terminal (T) for both the VOR and the DME. A common SSV may no longer be the case at all locations. A VOR/DME, for example, could have an SSV of VL for the VOR and DH for the DME, or other combinations.

See Charting Notice ENR_21-01_CN_SSV_Codes for more information.

Sample VOR/DME NAVAID box with two SSVs:

Latest on VOR Decommissioning

Here’s the latest information about the FAA program to decommission about 34 percent (307) of the VOR navaids in the U.S. by fiscal year 2030, leaving 589 VORs in the system. That plan includes establishing a minimum operational network (MON) of navaids and airports. The details are in an update (PDF) delivered at the April 26-29, 2021 session of the Aeronautical Charting Meeting.

You can find more information about the FAA plan in previous updates here at BruceAir:

• VOR Decommissioning: October 2020 Update
• Next Round of VOR Shutdowns
• Update on VOR Decommissioning
• FAA Releases List of VORs to be Shut Down
• VOR Status–Another Update

You can also watch video of an FAA webinar about the MON program on YouTube:

Here’s a summary of the next sets of VORs to be shut down. To see the VOR locations on aeronautical charts at SkyVector.com, click the navaid ID links.

Discontinue six (6) VORs – June 17, 2021:

1. (HNN) Henderson, WV
2. (LEB) Lebanon, NH
3. (LWM) Lawrence, MA
4. (MSS) Massena, NY
5. (MWA) Marion, IL
6. (SLK) Saranac Lake, NY

Discontinue six (6) VORs – August 12, 2021:

1. (DCU) Decatur, AL
2. (GBG) Galesburg, IL
3. (MAP) Maples, MO
4. (STS) Santa Rosa, CA
5. (UCA) Utica, NY
6. (VQQ) Jacksonville, FL

Discontinue five (5) VORs – October 7, 2021:

1. (EEN) Keene, NH
2. (HUL) Houlton, ME
3. (MCM) Macon, MO
4. (PSM) Portsmouth, NH
5. (RFD) Rockford, IL

FAA also plans to expand the service volumes of the remaining VORs and DMEs to support the MON.

AIM Updates Navaid Service Volumes

The December 31, 2020 edition of the AIM is out. This edition includes only a few updates, but section 1−1−8 NAVAID Service Volumes, provides a detailed explanation of new navaid standard service volumes (SSV) for VORs and DME, largely to support the change to performance based navigation (PBN).

Paragraph (a) of the section explains that:

The FAA publishes Standard Service Volumes (SSVs) for most NAVAIDs. The SSV is a three−dimensional volume within which the FAA ensures that a signal can be received with adequate signal strength and course quality, and is free from interference from other NAVAIDs on similar frequencies (e.g., co−channel or adjacent−channel interference). However, the SSV signal protection does not include potential blockage from terrain or obstructions. The SSV is principally intended for off−route navigation, such as proceeding direct to or from a VOR when not on a published instrument procedure or route. Navigation on published instrument procedures (e.g., approaches or departures) or routes (e.g., Victor routes) may use NAVAIDs outside of the SSV, when Extended Service Volume (ESV) is approved, since adequate signal strength, course quality, and freedom from interference are verified by the FAA prior to the publishing of the instrument procedure or route.

Details follow in paragraph (2):

With the progression of navigation capabilities to Performance Based Navigation (PBN), additional capabilities for off−route navigation are necessary. For example, the VOR MON (See paragraph 1−1−3 f.) requires the use of VORs at 5,000 feet AGL, which is beyond the original SSV ranges. Additionally, PBN procedures using DME require extended ranges. As a result, the FAA created four additional SSVs. Two of the new SSVs are associated with VORs: VOR Low (VL) and VOR High (VH), as shown in FIG 1−1−4. The other two new SSVs are associated with DME: DME Low (DL) and DME High (DH), as shown in FIG 1−1−5. The SSV at altitudes below 1,000 feet for the VL and VH are the same as FIG 1−1−3. The SSVs at altitudes below 12,900 feet for the DL and DH SSVs correspond to a conservative estimate of the DME radio line of sight (RLOS) coverage at each altitude (not including possible terrain blockage).

TBL 1−1−1, SSV Designator Altitude and Range Boundaries, and a couple of figures provide the details. ATH=Above Transmitter Height.

SSV Designator	Altitude and Range Boundaries
T (Terminal)	From 1,000 feet ATH up to and including 12,000 feet ATH at radial distances out to 25 NM.
L (Low Altitude)	From 1,000 feet ATH up to and including 18,000 feet ATH at radial distances out to 40 NM.
H (High Altitude)	From 1,000 feet ATH up to and including 14,500 feet ATH at radial distances out to 40 NM. From 14,500 ATH up to and including 60,000 feet at radial distances out to 100 NM. From 18,000 feet ATH up to and including 45,000 feet ATH at radial distances out to 130 NM.
VL (VOR Low)	From 1,000 feet ATH up to but not including 5,000 feet ATH at radial distances out to 40 NM. From 5,000 feet ATH up to but not including 18,000 feet ATH at radial distances out to 70 NM.
VH (VOR High)	From 1,000 feet ATH up to but not including 5,000 feet ATH at radial distances out to 40 NM. From 5,000 feet ATH up to but not including 14,500 feet ATH at radial distances out to 70 NM. From 14,500 ATH up to and including 60,000 feet at radial distances out to 100 NM. From 18,000 feet ATH up to and including 45,000 feet ATH at radial distances out to 130 NM.
DL (DME Low)	For altitudes up to 12,900 feet ATH at a radial distance corresponding to the LOS to the NAVAID. From 12,900 feet ATH up to but not including 18,000 feet ATH at radial distances out to 130 NM
DH (DME High)	For altitudes up to 12,900 feet ATH at a radial distance corresponding to the LOS to the NAVAID. From 12,900 ATH up to and including 60,000 feet at radial distances out to 100 NM. From 12,900 feet ATH up to and including 45,000 feet ATH at radial distances out to 130 NM.

More on FAA Plans to Decommission VORs

Here’s a link to the latest proposal from FAA to change from a ground-based navigation network to a GPS-based system of airways and approaches. The long title of the document: Proposed Provision of Navigation Services for the Next Generation Air Transportation System (NextGen) Transition to Performance-Based Navigation (PBN).

You can read all of the details and learn how to submit comments (due March 7, 2012) at the preceding link.

Update: FAA has released a three-page summary that provides more details about which VORs would be decommissioned. Details and links available from AOPA here.

Here are some highlights from the proposal:

The FAA plans to transition from defining airways, routes and procedures using VHF Omni-directional Range (VOR) and other legacy navigation aids (NAVAIDs) towards a NAS based on Area Navigation (RNAV) everywhere and Required Navigation Performance (RNP) where beneficial. Such capabilities will be enabled largely by the Global Positioning System (GPS) and the Wide Area Augmentation System (WAAS). The FAA plans to retain an optimized network of Distance Measuring Equipment (DME) stations and a minimum operational network (MON) of VOR stations to ensure safety and continuous operations for high and low altitude en route airspace over the conterminous US (CONUS) and terminal operations at the Core 30 airports.

Currently, over 80% of the 967 VORs in the NAS inventory are past their economic service life and cost the FAA more than $110M per year to operate. Likewise, replacement parts are becoming increasingly difficult to obtain. The replacement of all of the VORs would cost over $1.0B. Therefore, the FAA is planning a gradual discontinuance (removal from service) of VOR facilities in CONUS to a minimum operational network (MON). The MON would enable aircraft anywhere in the CONUS to proceed safely to a destination with a GPS-independent approach within 100 nm. MON coverage is planned to be provided at altitudes above 5,000 feet above ground level (AGL). The FAA would also retain VORs to support international arrival airways from the Atlantic, Pacific, Caribbean, and at the Core 30 airports. The existing U.S. legacy navigation aids outside CONUS will be retained until a longer-term solution can be coordinated with users. The drawdown of VORs to a MON would be completed no later than January 1, 2020.

For more information about the FAA’s plans, see an earlier post here at BruceAir’s blog about the Federal Radionavigation Plan (PDF).