Before the magenta line

The venerable VOR--in the abbreviation-soaked lexicon of aviation, that's short for VHF Omni-directional Range--long the backbone of aeronautical navigation in the United States, has been marked for extinction. While any report of the VOR's demise remains exaggerated (1,119 currently are in service across the nation), the FAA says that beginning in 2010, it will start to "reduce the network of VORs across the country," as reported on AOPA Online in August 2008. The reason: the ascendancy of GPS. (Meanwhile, AOPA has urged that the FAA not scale back VORs until it has managed to ensure that no flights--under visual flight rules [VFR] or instrument flight rules [IFR]-- will be compromised by their absence.) To appreciate what VOR has given pilots is to understand why its absence will be felt. New glass cockpits offer a clear dividing line between generations of pilots, as well as obvious economic differentiation. But in sparsely equipped trainers of the past few decades, there was a good chance that the only navigational equipment on board was a VOR receiver. That one humble unit was enough to vastly expand the horizons of a student pilot.

VOR has the odd distinction of being an abbreviation that contains within it another abbreviation: The V for VHF is short for very high frequency. VOR forms the root of other navaid terminology: VORTAC, a condensation of the combined VOR and TACAN (the military's tactical air navigation) installations, and VOR-DME: VOR stations paired with distance measuring equipment. VOR, VORTAC, and VOR-DME units have their own distinct symbols on aeronautical charts. Those symbols, and the compass roses that surround them, give navigation charts their distinctive look. Many VORs are linked by the profusion of Victor airway centerlines, each one identifying the magnetic bearing of the radial from the VOR where it emanates.

Radials are a perpetual head-scratcher for many new pilots learning to use VORs. Radials won't be missed when the last one ceases to radiate. That observation is partly for the historical record and partly in appreciation of the mental muscle pilots acquired from the effort expended on becoming skillful users of VOR.

Once you get the hang of it, a pilot can use VORs in different ways. You can use it to fly to a station, or from it, on a specific inbound or outbound course. If you have a second VOR receiver in your cockpit, you can locate your position by finding the intersection of the radial you are located on from Station A and the radial you are on from Station B. (Actually, you can triangulate your position using only one VOR receiver by changing frequencies; it's just more cumbersome.) Knowing your radial and distance from a VOR makes for an excellent means of reporting your position to ATC on initial call-ups. Indeed, you might be asked to "say radial and DME from" a particular VOR if radar identification is proving difficult.

The difficult, or counterintuitive, notion new pilots encounter when learning VORs is the idea that radials should be envisioned as two-way streets in the sky. Radials radiate outward all 360 degrees from the VOR. But you can fly either outbound or inbound on any given radial. An airplane flying outbound on the 180-degree radial is flying what heading? Correct, 180 degrees. An airplane flying inbound to the station on the 180-degree radial is flying 360 degrees, known as flying the reciprocal heading--but the airplane is still on the 180-degree radial. That aircraft would report that it is "inbound on the 180-degree radial," which would tell the controller where to look (south of the station) and what to look for (an aircraft heading north). This takes a lot of getting used to.

And that brings us to VOR's other data presentation: the To/From indicator. The northbound aircraft described above is flying with 360 degrees selected on the omni-bearing selector (OBS) and To showing on the To/From indicator. With the course deviation indicator (CDI) perfectly centered, the aircraft is nicely positioned on the inbound course.

Those 10 little dots beneath the CDI--five on either side--have something to say as well. Each represents two degrees of course deviation. Get too far off course and you will encounter another bit of proprietary VOR terminology: full deflection. Whether tracking or intercepting a course to or from a VOR, a glance at a fully deflected CDI tells you that you have some work to do. And fast, if the station is nearby. (Remember that a dot equals 200 feet of "linear deviation" when you are one nautical mile from the VOR, 200 feet at two miles, and so forth.) If the CDI is deflected to your left, it means the course was to your left. Needle to the right, course to the right. This is true whether you are flying inbound or outbound, provided that you are tracking the desired radial to or from the station. An exception to the work-fast imperative responding to needle deflections is when approaching station passage. When flying over a VOR, erratic behavior of all the moving parts is common; best to ignore the pandemonium until things settle down. Recognizing this short but hectic phase of VOR navigation is part experience, part expectation.

Every nav system is capable of delivering a punitive payback for misuse. VOR can dish it out with the best of them. Attempting to track inbound with a From indication, or outbound with a To indication, is the setup for headaches, or worse. This invokes the plague of reverse sensing, which as a penalty for lack of vigilance, delivers an incomparably cruel set of conflicting, ever-amplifying indications. Becoming entangled in reverse sensing's perplexing web delivers a lasting lesson: Tracking requires that your desired course match the bearing selected for tracking on the VOR receiver's OBS. A key lesson for the VOR-challenged is that just because a VOR indicates To or From, that doesn't mean that you are flying to or from the VOR. The indication only makes sense if you intercept and fly the course set on the OBS.

That's navigation. Other components co-located with VORs, such as those available for voice communication, require pilots to be sharp on their knowledge of omniranges. But they sure come in handy sometimes. Many VORs bear the notation 122.1R above the VOR's information box on navigation charts. This means that a pilot can communicate with Flight Service in an unusual manner, using two frequencies. First you turn up the volume on the VOR's nav channel (117.8 MHz on the Anton Chico VOR in New Mexico, for example), then call Flight Service on 122.1 MHz. You then tell them that you are monitoring Anton Chico VOR. FSS then responds on 117.8 MHz. For those pilots ever confused about who receives on 122.1 MHz and who transmits on it, just remember that a pilot can't transmit on the VOR frequency, 117.8 MHz. At some VORs, various frequencies in the 122.X series are noted as available for two-way calls. (You could use 122.2 at Concord, New Hampshire). Knowledge test questions and designated examiners have long zeroed in on such details.

VORs are also the source of transcribed weather broadcasts (TWEBs) and hazardous in-flight weather advisory service (HIWAS) broadcasts, useful regardless of whether you are navigating by that VOR. Some even broadcast automated terminal information service (ATIS) information for nearby airports. Hard, isn't it, to visualize VFR and IFR nav charts with all the details associated with VORs--airways, compass roses, communications boxes--deleted.

So if this all goes away someday, what else will VOR leave behind as its aeronautical legacy? VOR's exit won't be greeted with the cheers and sighs of relief that continue to accompany the slow death of nondirectional beacons (NDBs). It will be remembered gratefully by many a pilot as the system that challenged new airmen to get their heads around tricky concepts of navigation. It will be remembered more than fondly by many pilots who followed its distant signals home on days when visibility or the ceiling was headed downhill. VOR will always have the praises of those who avoided becoming lost by pinpointing their position on a chart by identifying the intersection of two radials from separate VORs. And non-GPS-equipped instrument students have long been eased into their tasks by employing their basic familiarity with VOR as an introduction to navigating without visual reference to the surface. Then, later in the instrument program they often encountered VOR in one of its most esoteric applications: using VOR with distance measuring equipment (DME) in combination to fly a radial-to-radial circumnavigation of the VOR, known as a DME arc.

And not everyone will stop using VORs once VORs become unusable. Old-timers still in command of the no-electrical-system fleet point out that a VOR station that's no longer transmitting still makes a great visual reporting point, with its cone-shaped edifice prominently positioned on high or open ground. Reporting in to ATC over a shutdown VOR may bring a perplexed response, but that's technology for you.

Dan Namowitz is an aviation writer and flight instructor. A pilot since 1985 and an instructor since 1990, he resides in Maine.