Airways — Page 153, Lesson 152

I want to walk you through the legend for an en-route chart — this is the key to reading the airway maps you'll use for instrument navigation. The legend is designed to work with charts that mostly use the Lambert Conformal Conic projection, and those charts are built specifically for airway instrument navigation using cockpit instruments, radio communications, and ground-based radio navigation aids. Let me be clear about one thing right away: not every symbol on the legend applies in every geographic area. On two-colour charts, symbols printed in green stay green; on single-colour charts, every symbol is blue. Keep that in mind as we go through the classifications. We start with Navaid Symbols — the symbols that represent ground-based navigation aids. Here's what you need to know: - VOR stands for Very High Frequency Omni-directional Range. That's your primary en-route navaid for bearing information. - Terminal VOR is a VOR used specifically for approach and departure phases, not typically for en-route navigation. - TACAN stands for Tactical Air Navigation, and DME stands for Distance Measuring Equipment. These give you slant-range distance from the station. - VORTAC or VORDME — these are collocated facilities. VORTAC combines a VOR and a TACAN; VORDME combines a VOR with DME. Both give you bearing from the VOR and distance from the TACAN or DME element. - NDB stands for Low and Medium Frequency Non-directional Beacon. It gives you a bearing to or from the station, but without the precision of a VOR. - ILS stands for Instrument Landing System. The legend also notes that KRM course is a Russian localizer equivalent — so if you see that on a chart, it's the same function as an ILS localizer but from a different system. - MLS stands for Micro-wave Landing System — a precision approach system using microwave frequencies. - Fan Markers — these are marker beacons that give you a vertical fan-shaped pattern to indicate position along an approach or airway. - Broadcast Stations — these are radio stations that may be used for navigation or for obtaining weather information. Now let's talk about Navaid Identification — how you tell whether a navaid is on an airway or not. The shadow box is used when the navaid is associated with an airway or route. That means if you see a navaid inside a shadow box, it's part of the airway structure. Off-airway navaids are un-boxed — no shadow box. There's one exception: off-airway VORs are boxed on charts other than US and Canadian charts. So on a European or Asian chart, even a VOR that isn't on an airway will still have a box around it. Moving to Communications — radio frequencies for voice communication are printed above the navaid name. That tells you voice communication is available through that navaid. There's a shorthand you need to know: radio frequencies in the 120 MHz range are shown with the numbers "12" omitted. For example, 122.2 MHz is shown as just 2.2, and 122.35 MHz is shown as 2.35. So when you see a frequency like 2.2 above a navaid, you mentally add the "12" back to get 122.2. Finally, Navaid/Communications Data — this section shows how a navaid's operational status is depicted. Let me break down the specific items mentioned: - TWEB stands for continuous weather broadcast — if a navaid has TWEB available, you can get continuous weather information from it. - SABH radio beacons — their primary function is to transmit continuous automatic weather information. So an SABH beacon is essentially a weather broadcast station. - R means en-route radar is available at that location. - H + 04 & 15 (1) — this is a specific notation for a Marine NDB. It means the NDB begins transmission at four minutes past the hour and at 15-minute intervals thereafter, and each transmission lasts for 1 minute. So you'd hear the beacon at 4 minutes past, 19 minutes past, 34 minutes past, and 49 minutes past the hour, each time for one minute. That figure shows you exactly how these symbols look on the chart. Take a moment to study it — you'll see the VOR symbol, the NDB symbol, the shadow box, the frequency notation above the navaid name, and the operational status codes. This legend is your reference for every en-route chart you'll use in instrument flight.