Back to the past – vor-to-vor navigation in Boeing 777. What to do if you want (or need) to use classic enroute or approach procedures?
Why do I write about radionavigation in 777?
When I fly to exotic places I often struggle finding current charts and procedures. The ones that I find date back to 2010 or even 2003! Since then the procedures changed and I have a choice of flying by the chart that I downloaded or using my FMC database as the only source of data about my approach. I usually choose my charts and the complete description – even if it’s outdated. That is when I need to be able to fly along published radials. It’s also helpful in places where routes changed and for some reason – I want to fly along old ones. Radio navigation also comes helpful when I fly custom routes (although I rarely do this in 777).
#1 LNAV mode – enter your route in FMC
Flying along radials is no different than flying any other great circle route. With 777’s FMC I do not need to actually follow navaid’s radial – I can enter two points of this radial as waypoints and fly this route using LNAV mode.
Look at this example. I want to fly radial 60 from BLH VOR. I will use BLH as the first waypoint and BLH03, BLH04 and BLH05 as my waypoints.
For those who have no idea what I just did. The first picture shows the moment when I have finished entering my new waypoints. To do this – I entered each point in scratchpad, then I clicked the button on the left – to place the new waypoint. I finished by pressing EXEC button. After I entered the new waypoints there was a discontinuity in my route – so I copied the next point into this blank field (five small rectangles) and EXECuted the new route.
What exactly did I enter in the scratchpad?
- for BLH03: BLH060/010
- for BLH04: BLH060/040
- for BLH05: BLH060/086
What it means?
BLH060/086 – VOR id
BLH060/086 – radial
BLH060/086 – distance (in nautical miles)
BLH03, 04 and 05 numbers are the consecutive numbers of waypoints based on BLH navaid (earlier I created BLH01 and 02 – these were deleted).
I could also use radials intersection to define a waypoint – for example: BLH060/PKE130.
BLH060/PKE130 – first VOR id
BLH060/PKE130 – first VOR radial
BLH060/PKE130 – second VOR id
BLH060/PKE130 – second VOR radial
After creating a route like this – autopilot in LNAV mode will follow it without any additional actions from your side.
#2 show VOR radial on your nav display
Lets say that you do not want to enter waypoints and you just need to fly a given radial for a moment. In a simpler plane you would dial the radial using OBS knob and then follow it using VOR indicator or HSI.
To do this in PMDG 777 you need to go to NAV RAD page of your FMC and set VOR frequency (or ID) and the course you need to follow (CRS).
Actually you will enter the VOR and the course together – like this BLH/090.
There is a dashed green line on the Navigation Display now. In VOR mode Nav Display will show a familiar CDI needle and deviation dots.
Boeing 777’s autopilot (and APs of other boeings with the exception of 737) will not follow selected course (there is no VOR or NAV mode in you autopilot). To fly the selected course you need to use TRK SEL mode. In the TRK SEL mode you will need to adjust your track from time to time when flying along radial on a longer distance.
TRK SEL is sufficient to follow the assigned course line in approach and arrival procedures. In case you need to fly 50 or 100 miles – use the LNAV solution that I described above.
What do they do in real world?
When I looked at the real world aviation related forums I saw a surprise reaction when someone (clearly a sim pilot) asked about classic (obsolete) radionavigation techniques in 777. Usually planes like 777 do not operate from airports that do not have procedures programmed in FMC’s database and they do not use navaid radials in en route navigation.
On the other hand – I found a few examples of such flights! These were usually cargo flights in Africa or Pacific region and some cargo or charter flights in conflict zones when 777 were landing on airports that had no procedures distributed by civilian database providers.
Bu these situations are extremely rare. In sim – it’s just a good idea to learn these techniques to be proficient with your plane – and to avoid any surprises like a modified procedure.