It’s quite simple, really. Although there is no place in the Air Traffic Procedures manual (FAAH 7110.65), which specifically states that “join airways—intercept radials/localizers/courses/bearings” is the approved application, you will see many examples of phraseology which include the words “join” and “intercept”. In every case, “join” is only used in conjunction with the word “airway” and “intercept” is only used with the words “radial”, “course”, “localizer”, or “bearing”. In no case is there any cross contamination of those examples.
If you understand what is meant by that plethora of words, you will understand why there is no ambiguity. First, the latter group of words (radial, course, localizer, bearing) describe a “line” in space. As you may remember from high school geometry, a line is a series of points, and points are infinitely small—they have no dimension. They can be represented by a needle on the instrument panel, but it’s that representation which has dimension, not the line.
Airways, on the other hand, whether Victor (low altitude) or Jet (high altitude) are made up of, by definition, the radial (of a VOR) plus four miles either side of the defining radial which is called protected airspace. If you are given a clearance to “join” an airway, you are to fly to the defining radial and intercept it, but you are afforded separation as soon as you cross the four mile boundary. In other words, the airway has dimension (width), and you are established within its confines as soon as you are within it, even if you haven’t quite reached the radial which defines it. I don’t want to quibble about the various RNAV types of navigation—the bulk of the air navigation system is still made up of airways defined by VORs and their radials. The definition of an airway as including protected airspace still applies, regardless of how the pilot navigates it.
In simple terms, therefore, “join” means to be gathered within an airway. Since none of the other route definitions imply any dimension, they cannot be joined—one can only “intercept” them.
Addendum: When posting this page as a proof in some internet discussion boards, there were some (ignorant) detractors, no doubt abusers of the principals above, who tried to make the claim that, “those are just examples. They aren’t the direction for application”. Sigh. Okay, lets put this another way, there is no place in the ATP where proper phraseology is specified anywhere but in the examples. It’s mind numbingly tiresome trying to keep up with gadflies. It’s like Whack-a-Mole.
Last updated: 13 November 2016