Let’s walk through Figure 16.9 together — Page 276, Lesson 271

Let’s walk through Figure 16.9 together. This is the RTE — the route page — on the FMS, the Flight Management System, and it’s where you build the route you’re actually going to fly. I’ll take it line by line, because each line on this page has a specific job. Start at the top. The departure aerodrome goes into line 1L, and the destination aerodrome goes into line 1R. “L” and “R” mean the left and right sides of that line on the CDU, the Control Display Unit. The data is valid only if it’s an ICAO aerodrome designator held in the database — so a four-letter code like EGLL for London Heathrow. If you already entered the ICAO identifier on the POS INIT page, the position initialization page, then it will automatically appear at 1L. Moving down. The company route is inserted at 2L, and the flight number at 2R. The company route is the pre-defined route your airline has stored in the database. At 3L you insert the runway in use, and at 4L you insert the SID — that’s the Standard Instrument Departure — and the first route waypoint. Here’s a nice detail: if the runway, SID, and first waypoint are already defined in the company route, they will appear automatically; you don’t have to type them. Now lines 5L and 5R. The information there is inserted by the computer from the database, not by you. 5L shows the airway, and 5R shows the next reporting point on airway V2. So the computer is already building the route structure for you. If you need to check or modify the route, you press the NEXT PAGE function key on the keyboard to access the subsequent pages of the RTE. Then look at the 6R prompt — that directs you to activate the route. When you press 6R, the EXEC key on the CDU illuminates. That’s the execute key. You press EXEC for the computer to action the route after take-off. So the sequence is: press 6R, the EXEC key lights up, you press EXEC, and the route is armed for after take-off. Now here’s what happens in flight. After take-off, the RUNWAY line is cleared. The VIA/TO moves up to line 3, and the next waypoint appears at line 4. As you pass an active waypoint, line three is cleared and replaced with the next active waypoint. So the page keeps rolling forward — the active leg is always at line 3, and the next waypoint is at line 4. At this point, the pre-flight actions for the navigation profile are complete. But note — the performance initialization is not done yet. That’s handled elsewhere in the course. The computer will check the conditions against the performance data and the required cost index profile, and it will inform the pilots of the power, speed, and configuration needed to achieve the required profile. So the FMS isn’t just navigating; it’s also computing how to fly the route efficiently. If you need to input a route manually, you can do that through the scratchpad — that’s the line at the bottom of the CDU where you type entries — and you can also use it for any modifications to the standard company routes. Finally, let’s cover the valid formats for navigational inputs, because the FMS is strict about this. Latitude and longitude can be entered in two formats. The first is a 7-group alphanumeric, like N05W010. The second is a 15-group, like N0926.3W00504.7. And here’s a critical detail: leading zeros must be entered for the FMC to accept the position. So you can’t drop the zero in front of the 5 — it has to be N05, not N5. For other identifiers, you can use up to 5 alphanumerics for ICAO aerodrome designators, reporting points, navigation facilities, airways designators, and runway designators. Examples would be EGLL for an aerodrome, KODAP for a reporting point, DHD for a navigation facility, A23 for an airway, and a runway designator like 27L. So the whole picture: the RTE page is where you build and activate your route, the computer fills in the airway and reporting points, you activate it with 6R and EXEC, and after take-off the page rolls forward as you pass waypoints. And every input has to be in the exact format the FMC expects.