Airways — Page 153, Lesson 154

I want to walk you through the symbols, abbreviations, and altitude definitions you need to know for airways and airspace on aeronautical charts. This is foundational for flight planning and monitoring, so let's take it step by step. First, restricted airspace. You need to know the symbols and abbreviations for the various types of restricted airspace — that's essential. These are areas where flight is limited for reasons like military activity, security, or hazard. The chart will mark them with specific symbols and letter codes, and you must be able to recognize them at a glance. Next, airports. Memorize the symbols for civil and military airfields. Civil airports and military airfields are depicted differently on charts, and confusing them could lead to serious navigation errors, especially in an emergency or when planning an alternate. Now, airway and route centrelines. You need to know the meaning of these symbols too. In particular, note the depiction of airways themselves, the types of reporting points, LF bearings and radials, and holding patterns. Let me unpack those. An LF bearing is a Low Frequency bearing — that's a direction to the navaid, measured from the aircraft's position toward the station. A radial, by contrast, is a direction from the navaid, measured outward. So if you're tracking a radial, you're flying away from the station; if you're following a bearing, you're flying toward it. Holding patterns are the racetrack-shaped paths you fly while waiting for clearance, and their depiction on the chart includes the inbound leg, the outbound leg, and the direction of turn. Now, airway information. Pay particular attention to the different designations of airways and routes, and the minimum clearance limits associated with each. Here are the key examples. V168. The "V" stands for Victor airway — that's a VOR airway. Victor routes are found on US and Canadian Low Level charts. They are effective up to, but not including, 18,000 feet MSL — Mean Sea Level. So below 18,000 feet, you're on Victor airways. J71. The "J" stands for Jet route. These are for high performance aircraft. In the US, Jet routes are effective at and above 18,000 feet MSL up to Flight Level 450 — that's FL450, or 45,000 feet. In Canada, they are effective at and above 18,000 feet MSL to unlimited — no upper limit. A1. European countries use the phonetic alphabet for airway designations. So "A1" is an airway in Europe, and you'd read it as "Alpha One." Now let's move to the altitude definitions, because these are critical for safe flight planning. Minimum En route IFR Altitude (MEA). This is the lowest published altitude between radio fixes that meets obstacle clearance requirements between those fixes. In many countries, it also assures acceptable navigational signal coverage. The MEA applies to the entire width of the airway, segment, or route between the radio fixes that define that airway, segment, or route. So if you're flying on an airway, you must not go below the MEA for that segment. Minimum Obstruction Clearance Altitude (MOCA). This is the lowest published altitude in effect between radio fixes on VOR airways — that means below 18,000 feet MSL — and also on off-airway routes or route segments. The MOCA meets obstacle clearance requirements for the entire route segment. However, in the USA, it assures acceptable navigational signal coverage only within 22 nautical miles of a VOR. So outside that 22 NM radius, you may lose reliable VOR signal, even though you still have obstacle clearance. Minimum Off-route Altitude (MORA). This is an altitude derived by Jeppesen — the charting company. The MORA provides known obstacle clearance within 10 nautical miles of the route centre line. So if you're flying off an airway, the MORA gives you a safe altitude that clears all known obstacles within 10 NM either side of your planned track. Let me show you how these appear on a typical chart. That figure illustrates the airway layout, the restricted airspace symbols, and how these altitudes are annotated along the route. You'll see the MEA and MOCA values posted at fixes, and the MORA in areas off the airway structure. So to summarise: you have three key altitudes — MEA for on-airway IFR with signal coverage, MOCA for VOR airways below 18,000 feet with signal only within 22 NM of the VOR, and MORA for off-route obstacle clearance within 10 NM of your centre line. Know the airway designations: Victor for low-level, Jet for high-level, and phonetic for Europe. And memorise the symbols for restricted airspace and airfields — that's non-negotiable for professional flight planning.