Page 6 - Volume 15 Number 2

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should the integrity of the current GPS system be compromised for any reason for any length of time. GPS signal outages are not uncommon. The military intentionally jams (blocks) specific GPS signals regularly for a variety of reasons related to national security and military training exercises. Occasionally, GPS satellites go offline as they reach the end of their lifespan or are undergoing remote updating or maintenance. Such outages are generally limited in scope and include a heads-up to pilots in the form of Notices to Airman (NOTAMs). But, because the GPS system is satellite based (rather than ground based, like VORs) it is more susceptible to a variety of less predictable outages, such as cosmic events or malicious enemy attack. Of course, failures of onboard GPS equipment, related wiring or antennas, etc. is always a possibility, as well.
There is little doubt that Perfor- mance Based Navigation (PBN), Required Navigation Performance (RNP), and a variety of other tongue-twisters related to GPS have totally changed the landscape of long, short and terminal range navigation. That has made the chores of navigation exponentially easier and safer for pilots. Nonethe- less, GPS is not, and never will be, a failure-proof system. A ground based backup system for naviga- tion is critical to maintaining and protecting the National Airspace System (NAS). Maintaining our knowledge and skills related to the use of that backup system is no less critical.
The VOR Revolution
Like many prior navigational advances, the introduction of the VOR was truly revolutionary. It was not dependent upon visual conditions or low altitude flying, such as lighted airways and ground markings were. It was not dependent upon the pilot’s ability to constantly monitor and decipher audible signals, such as the AN Radio Range
system was. VOR navigation was not limited to only a few specific courses, such as the Four Course Range. It was not susceptible to atmospheric interference such as Non-Direction Beacons (NDBs). Nor were the pilots using it nearly as prone to misinterpreting its information and creating dangerous navigation errors. VORs provide an infinite number of precise radials, broken into 360 one-degree segments, that the pilot can track to/from the facility with a high degree of accuracy thanks to easy to interpret cockpit equipment. Its only real limit is range, as dictated by the strength of the facility’s signal and the line-of-sight between said facility and the receiving aircraft. VOR navigation might seem quite antiquated now, compared to the precision and ease of today’s various forms of GPS navigation. Nonetheless, it was a massive leap forward in technology when it was introduced nearly 75 years ago. Additionally, it has proven to be highly dependable, making it the longest-standing navigation system in the U.S. National Airspace System (NAS), with no end date to that streak in sight.
VOR Expansion
Development of the VOR began
in 1937, but it was not until 1946 (soon after World War II) that the first station became operational and well into the 1950s before their installations had become more widespread. While those early VOR stations were combination vacuum tube and mechanical devices, solid state technology began to take hold within the VOR network in the 1960s. It was after that point that VORs became common enough to be adopted as the world standard for air navigation. After the introduction
of the VOR, variations on its concept soon developed. Different types of VORs emerged to support different types of navigation. Big and powerful VORs, which could
be received 100-plus miles away were great for use as both enroute and terminal navigation facilities. ›
4 • KING AIR MAGAZINE
FEBRUARY 2021