I’m not happy to hear that the FAA will be phasing (no pun intended!) out VORs. I’m no Luddite, but VORs have been a most reliable navigation aid for quite a long time. I believe, just as with NDBs, they provide a solid backup that shouldn’t be so easily relegated to the trash heap. GPS is great, really great. I just think throwing our lots in with what’s admittedly an outstanding piece of technology to the exclusion of all the other navigational systems is shortsighted.
I think it comes down to pilots’ aversion to math. Yes, math. The modern aviator doesn’t like angles and “figurin’” preferring the cozy comfort of a magenta line stretching out into the electric distance whispering “follow me.” And so we forget how we got here and how “here” can be passing and perishable. If you think that isn’t true, ask those who have gotten lost because the power to the electrics on the aircraft died or because the batteries ran out. What saddens me is reading stories of pilots declaring emergencies because their GPS receivers had decided to take a well-earned digital holiday.
And so we abandon the tried and true simply because “math is hard.” When figuring out where you are in relation to a beacon becomes too difficult, what hope? However, in the middle of my admittedly hyperbolic, “get off my lawn, you young rascals” rant, I have to recognize something which has bothered me for a long time.
The problem, and it is a very common one, is that the authors of the explanatory texts are unclear. Using sixty words when four will do; tortured sentences; convoluted, flamboyant, overdecorated verbiage (yes, I know …); atrocious grammar. The list of grievances is endless and it makes it so that your average student trying to understand the ideas ends up confused by the words. He cannot see the idea forest for the literary words, if you will bear with the shaky metaphor.
It wasn’t until I branched out and started reading some older navigational material from WWII (check out Google’s library of digitized books) and also some British authors that I started to understand this idea. The older boys used direct sentences that explained in a way sure to provide information while getting out of the idea’s way.
I’ll give an example of this using the explanation of the VOR. I’ll start with the FAA’s description of what a VOR is and how it works, from the Pilot’s Handbook of Aeronautical Knowledge (PHAK):
Very High Frequency (VHF) Omnidirectional Range (VOR)
The VOR system is present in three slightly different navigation aids (NAVAIDs): VOR, VOR/DME, and VORTAC. By itself it is known as a VOR, and it provides magnetic bearing information to and from the station. When DME is also installed with a VOR, the NAVAID is referred to as a VOR/DME. When military tactical air navigation (TACAN) equipment is installed with a VOR, the NAVAID is known as a VORTAC. DME is always an integral part of a VORTAC. Regardless of the type of NAVAID utilized (VOR,
VOR/DME or VORTAC), the VOR indicator behaves the same. Unless otherwise noted, in this section, VOR, VOR/DME and VORTAC NAVAIDs are all referred to hereafter
The prefix “omni-” means all, and an omnidirectional range is a VHF radio transmitting ground station that projects straight line courses (radials) from the station in all directions. From a top view, it can be visualized as being similar to the spokes from the hub of a wheel. The distance VOR radials are projected depends upon the power output of the transmitter.
The course or radials projected from the station are referenced to magnetic north. Therefore, a radial is defined as a line of magnetic bearing extending outward from the VOR station. Radials are identified by numbers beginning with 001, which is 1° east of magnetic north, and progress in sequence through all the degrees of a circle until reaching 360. To aid in orientation, a compass rose reference to magnetic north is
superimposed on aeronautical charts at the station location.
H’m. This doesn’t really tell me much about how the VOR works per se and I don’t know how much of that information will be of help to a new student who’s never heard of a VOR before!
The information you get from the FAA’s Flight Navigation Handbook and the Instrument Flying Handbook have close to the same information, a radio transmitting courses from the station in all directions, like the spokes from the hub of a wheel.
But what are its principles of operations without resorting to simplistic explanations like hubs from a wheel? Here’s how brits Bramson and Birch describe it in their 1984 book, Radio Navigation for Pilots:
PURPOSE OF THE EQUIPMENT
To facilitate en-route navigation along selected radials and to provide references for holding and let-down procedures.
PRINCIPLE OF THE AID
VOR is a relatively short range radio navigational aid operating between 108 and 118MHz in the VHF band. It is a pilot interpreted aid comprising an airborne Navigation Receiver capable of being tuned to 100 or more frequencies and a Converter/Indicator which accepts signals from the navigation receiver translating them into simple indications on an instrument face. The airborne equipment is used in conjunction with a system of VOR beacons, most of them situated within the airways network.
To understand the principles of VOR it is necessary to have a superficial knowledge of the radio wave itself.
In the section on electro-magnetic energy the basic wave cycle was described (page 50). In essence the state of the electric current within a cycle (i.e. positive or negative strength) is constantly varying with time. Indeed at any particular time the development of the wave may be identified e.g. half maximum positive rising: maximum negative: zero raising to positive etc. As already explained such a state of development is known as a Phase.
Imagine a radio beacon designed to radiate two beams, one running north and the other running south. And suppose each beam consists of two waves, the north beam emitting its phases in unison and the south beam with its waves at opposite phases (Fig. 41). An electronic device capable of measuring the difference in phase between two radio waves would, in this case be able to tell the operator when he was within the north beam or south beam. In other words the equipment is able to compare the differences between the phases of two simultaneously transmitted waves and since it uses this principle VOR is known as a Phase Comparison aid.
THE VOR TRANSMITTER
Using the principle of phase comparison the VOR radiates a Reference Signal in all directions, its phase remaining constant throughout the reception area. A second signal, transmitted as a narrow beam, is arranged to sweep like a lighthouse through 360°. As it sweeps, the phase of the beacon is constantly altering so that its phase comparison with the fixed reference signal will change according to its position relative to the beacon (Fig. 42). In effect a VOR beacon emits an infinite number of beams or Radials through 360°, each possessed of unique differences in phase between the two signals. It therefore follows that with the air of equipment designed to measure or compare the two phases and translate these into headings from the beacons (radials), a pilot would be able to locate his aircraft in relation to the known position of that beacon. The VOR Beacon is adjusted to transmit radials related to Magnetic North.
Please tell me which one of the two explanations of the VOR’s principles of operation you found easier to understand?
Now I don’t know if this is a good example in particular of what I’m talking about in general, but if you’re not convinced I’ve got more examples*¹.
*¹ Even though for example is not proof.