Lois Larson
VOR approaches are one of the most widely used non-precision approaches in the US. They are based on VHF Omni-Directional Range Radio (VOR) technology, which operates within a specific frequency range. While VOR approaches continue to be used in the US, the country has been decommissioning many VORs in favour of GPS-enabled RNAV approaches. This transition has resulted in some airports retaining VOR approaches while others have shifted entirely to GPS or RNAV approaches. As a result, pilots must remain skilled in both VOR and RNAV/GPS approaches to navigate effectively.
| Characteristics | Values |
|---|---|
| VOR approach availability | Varies across airports; some airports are decommissioning VOR approaches in favor of GPS-based approaches |
| Use cases | VOR approaches are widely used non-precision approaches; they are recommended for non-precision flights by the FAA |
| Frequency range | 108.0 MHz to 117.95 MHz |
| Signal type | Sends one stationary master signal and one rotating variable signal |
| Antenna location | Usually on the tail of the aircraft |
| Bearing determination | By comparing the difference between the VOR's variable and reference phases |
| Descent and altitude management | Must be managed manually during a VOR approach |
| Final approach course | Charted based on a radial from or to a nearby VOR |
| Minimum Descent Altitude (MDA) | Varies depending on terrain and obstacles; can be as low as 250 feet above the runway in flat terrain |
| Distance Measuring Equipment (DME) | Often coupled with VOR approaches to provide reliable distances during the final approach |
| MON (Minimum Operating Network) airports | Airports that provide non-GPS-based approaches for aircraft encountering GPS outages; ensure pilots are within 100 NM of an airport |
| RNAV approaches | Becoming more common due to the wide use of GPS; require aircraft to be equipped with a Wide Area Augmentation System (WAAS) GPS receiver |
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What You'll Learn
- VOR approaches are one of the most widely used non-precision approaches in the US
- The FAA recommends using the Continuous Descent On Final Approach (CDFA) method
- VORs are being decommissioned or not repaired
- RNAV approaches are becoming more common due to the wide use of GPS
- The VOR MON is a reversionary service provided by the FAA for use by aircraft that are unable to continue RNAV during a GPS disruption
VOR approaches are one of the most widely used non-precision approaches in the US
Every VOR approach is non-precision, meaning there is no vertical guidance signal from the VOR. As a result, pilots must manually manage their descent and altitude during the approach. The final approach course is charted based on radials from or towards a nearby VOR. After completing a procedure turn or receiving vectors to the final, pilots will typically step down along a series of fixes to minimum published altitudes on an approach chart. As pilots approach the VOR, the signal becomes more sensitive. This is true for both VOR approaches based on VOR NAVAIDs located at the airport and off-field VOR approaches, where the VOR is located several miles away.
VOR approaches are often coupled with Distance Measuring Equipment (DME) to provide reliable distances during the final approach. This combination of VOR and DME allows pilots to navigate accurately and safely towards their intended destination. The FAA recommends using the Continuous Descent on Final Approach (CDFA) method for non-precision approaches, ensuring a smooth and efficient descent profile.
While VOR approaches are commonly used, they are being decommissioned or replaced by GPS-based approaches at some airports. This transition is part of the Minimum Operating Network (MON) initiative, which aims to streamline navigation systems and reduce the maintenance burden. However, the FAA recognizes the importance of retaining VOR approaches, especially for aircraft without GPS capabilities. The VOR MON ensures that aircraft are always within 100 nautical miles of an airport, providing a backup option during GPS outages or navigation to a suitable airport for landing.
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The FAA recommends using the Continuous Descent On Final Approach (CDFA) method
The CDFA technique is safer and easier to fly than the "dive and drive" approach, and it does not require any special equipment. However, technology can help with this method. The CDFA is a continuous descent without levelling off, from an altitude/height at or above the final approach fix altitude/height to a point approximately 15 meters (50 feet) above the landing runway threshold.
When flying a non-precision approach with stepdown fixes, pilots are required to perform multiple power, pitch, and altitude adjustments while flying in the clouds. These adjustments increase the pilot's workload in a critical phase of flight and increase the chance for error. The CDFA method helps to mitigate these risks.
Additionally, the FAA and Jeppesen are publishing a CDFA for most non-precision approaches, making it safer and easier for pilots. The CDFA is characterized by maintaining a stable approach speed, descent rate, vertical flight path, and configuration to the landing touchdown point.
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VORs are being decommissioned or not repaired
VORs, or VHF Omni-Directional Range Radios, are widely used non-precision approaches in the US. They are an aircraft navigation system that uses radio signals to help pilots determine their position and stay on course.
However, in recent years, the FAA has been actively decommissioning VORs or leaving them unmaintained and unrepaired. This is due to the high cost of maintaining the VORs, with the FAA citing the expense of contractors and labour as a reason for their decision. The original plan was to decommission 470 VORs by 2020, but as of April 2019, only 23 had been decommissioned. Now, the FAA is targeting a reduction of 308 VORs by 2025.
The transition to the Minimum Operating Network means that VORs are being decommissioned or not repaired, especially if airports have one or more GPS approaches. This has caused some frustration for pilots, who may need to travel over 100 miles to find a VOR approach for training purposes. Additionally, the cost of IFR-certified GPS systems is high, and some pilots prefer VOR approaches.
The FAA has stated that the MON will retain sufficient VORs and increase VOR service volume to ensure that pilots will have a nearly continuous signal reception when flying at 5,000 feet AGL. The MON is designed to ensure that aircraft are within 100 NM of an airport in the case of a GPS outage. However, some pilots are concerned about the lack of a reliable backup system, as GPS is susceptible to jamming.
Overall, while the decommissioning of VORs may be a cost-saving measure for the FAA, it has caused some disruption for pilots and raised concerns about the reliability of GPS as a primary navigation system.
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RNAV approaches are becoming more common due to the wide use of GPS
The wide adoption of GPS has led to RNAV approaches becoming increasingly common. RNAV, or Area Navigation, is a way for pilots to navigate without needing ground-based navigation aids. RNAV approaches use GPS waypoints for direct routes, and unlike traditional systems like ILS, do not require beacons. This makes RNAV approaches especially useful at smaller or remote locations. RNAV approaches are also more efficient, as they allow for direct paths and continuous descents, saving time and fuel. Additionally, RNAV approaches are easier to fly as they provide reliable, smooth descent paths and are not affected by extreme temperatures like barometric altimeters.
RNAV approaches are designated as RNAV(GPS) in the US, indicating that they use GPS for position information. RNAV approaches can also use other satellite systems, such as GLONASS, or a combination of satellite systems, as well as DME/DME updates from ground-based navaids. The flexibility of RNAV allows pilots to choose the most suitable system for their needs.
While RNAV approaches offer many benefits, it is important to have a backup system in place in case of GPS failure. Traditional ground-based navigation systems can serve as a reliable backup option, ensuring safe landings even if GPS is unavailable due to solar storms, jamming, or satellite issues. Maintaining proficiency in traditional navigation approaches, such as VOR and ILS, is crucial for pilots flying GPS-equipped aircraft.
The Federal Aviation Administration (FAA) has introduced the concept of VOR MON to address situations where GPS may be disrupted. VOR MON ensures that aircraft can navigate through GPS outage areas or land at a MON airport or another suitable airport within 100 NM. This reversionary service provides a safety net for aircraft unable to continue RNAV during GPS disruptions.
As RNAV approaches become more prevalent, it is important for pilots to understand the benefits and limitations of this technology. With its reliance on GPS, RNAV offers improved flexibility, efficiency, and precision in navigation. However, the potential for GPS outages underscores the ongoing need for proficiency in traditional navigation methods and the availability of backup systems.
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The VOR MON is a reversionary service provided by the FAA for use by aircraft that are unable to continue RNAV during a GPS disruption
The Federal Aviation Administration (FAA) is removing selected VORs from service as flight procedures and route structures based on VORs are being replaced with Performance-Based Navigation (PBN) procedures. PBN procedures are primarily enabled by GPS and its augmentation systems, collectively referred to as the Global Navigation Satellite System (GNSS).
The VOR Minimum Operational Network (MON) is a reversionary service provided by the FAA for aircraft that are unable to continue RNAV during a GPS disruption. The VOR MON is a limited network of VORs that provides a basic conventional navigation service for operators to use if GNSS becomes unavailable. The MON will enable aircraft to navigate through the affected area or to a safe landing at a MON airport without reliance on GNSS. The VOR MON will ensure that regardless of an aircraft's position in the contiguous United States (CONUS), a MON airport (equipped with legacy ILS or VOR approaches) will be within 100 nautical miles.
The VOR MON will retain sufficient VORs and increase VOR service volume to ensure that pilots will have nearly continuous signal reception of a VOR when flying at 5,000 feet AGL. This will allow pilots to proceed via VOR-to-VOR navigation at 5,000 feet AGL through the GPS outage area or to a safe landing at a MON airport or another suitable airport.
The FAA recommends that pilots flying GPS- or WAAS-equipped aircraft that also have VOR/ILS avionics should be diligent in maintaining proficiency in VOR and ILS approaches in the event of a GPS outage.
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Frequently asked questions
VOR stands for Very High Frequency Omni Directional Range. It is a type of non-precision approach used in aviation. The VOR sends out one stationary master signal and one rotating variable signal. These are also called "reference" and "variable" phases. The aircraft's VOR antenna picks up this signal and transfers it to the receiver in the cockpit.
VOR approaches are one of the most widely used non-precision approaches in the US. In the case of a GPS outage, pilots can use VOR approaches to navigate through the outage or land at a MON airport or another airport.
A VOR-A approach is a circling-only approach. It is defined as any final approach course that is more than 30 degrees from the extended centerline at the designated missed approach point.
While I cannot find a list of US airports with VOR approaches, I can tell you that there are 5,000 public-use airports, heliports, and seaplane bases in the US. As of 2022, there were 6,956 RNAV approaches, of which 69 were GPS approaches, 6,468 were RNAV (GPS) approaches, and 419 were RNAV (RNP) approaches. Only 25 airports (1.8%) have a radio-based approach but no RNAV/RNP available.
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