ATC Flight Plan — Page 238, Lesson 238

I want to walk you through the route field of the ATC flight plan — this is where we tell air traffic control exactly where we intend to go, at what levels, and under what flight rules. Let's start with how we express altitude in this field. Altitude is written in one of three ways. First, in hundreds of feet, expressed as the letter A followed by three figures — so A045 means 4,500 feet, A100 means 10,000 feet. Second, in tens of metres, expressed as the letter M followed by four figures — M0840 means 8,400 metres. Third, for uncontrolled VFR flights — that is, Visual Flight Rules flights not under air traffic control — you simply insert the letters VFR. Now let's look at how we build the route itself. The book splits this into two main cases: flights along designated ATS routes, and flights outside designated ATS routes. ATS stands for Air Traffic Service — these are the published airways and routes that ATC manages. For flights along designated ATS routes, you start by inserting the designator of the first ATS route — but only if the departure aerodrome is located on, or connected to, that route. If the departure aerodrome is not on or connected to the ATS route, you instead insert the letters DCT — meaning direct — followed by the point where you will join the first ATS route, and then the designator of that route. So for example, if you take off from a small airfield not on an airway, you'd write DCT followed by, say, a VOR or a waypoint, then the airway designator. After that, you insert each point at which you plan a change of speed, a change of level, a change of ATS route, or a change of flight rules. There's an important note here: when you plan a transition between a lower and an upper ATS route, and both routes are oriented in the same direction, you do not need to insert the point of transition — ATC can handle that without an explicit waypoint. Then, after each of those points, you follow with the designator of the next ATS route segment — even if it's the same route as the previous one. If the flight to the next point will be outside a designated route, you insert DCT instead, unless both points are defined by geographical coordinates. So DCT tells ATC you're going direct, off the airway. Now for flights outside designated ATS routes — this is when you're not following airways at all. You insert points normally not more than 30 minutes flying time or 370 kilometres — that's 200 nautical miles — apart. You must include each point where you plan a change of speed, a change of level, a change of track, or a change of flight rules. You also insert additional points when required by the appropriate ATS authority. The book gives specific rules for defining the track of flights operating predominantly in an east-west direction between 70 degrees north and 70 degrees south. In that band, you define the track by significant points formed by the intersections of half or whole degrees of latitude with meridians spaced at intervals of 10 degrees of longitude. So you'd pick points where, say, latitude 45 degrees north crosses longitude 10 degrees west, then 20 degrees west, and so on. For flights operating outside those latitudes — north of 70°N or south of 70°S — the tracks are defined by significant points formed by the intersection of parallels of latitude with meridians normally spaced at 20 degrees of longitude. The distance between significant points should, as far as possible, not exceed one hour's flight time. You add additional significant points as deemed necessary. For flights operating predominantly in a north-south direction, you define tracks by significant points formed by the intersection of whole degrees of longitude with specified parallels of latitude spaced at 5 degrees. So you'd pick points where, say, longitude 10 degrees west crosses latitude 45 degrees north, then 50 degrees north, then 55 degrees north. Finally, between successive points in this off-route case, you insert DCT — unless both points are defined by geographical coordinates or by bearing and distance. So if you have two waypoints that are both given as latitude/longitude pairs, you don't need DCT; the coordinates themselves define the direct path. That figure shows you a specimen ATC flight plan so you can see how all these elements come together on the actual form. The route field is where we pack all this information in a very precise, standardised format so that ATC knows exactly what we intend to do from departure to destination.