PMDG FMC + oceanic waypoints

[EHM-1001 Robert]

Hi folks,

after the funny Lisbon flyin, I made a short discovery, why the bloody FMC will not let me enter oceanic waypoints.

First of all, you can enter these kinda waypoints only on the LEGS page, not on the RTE page ! I browsed through the AIRAC WPT database, and the required waypoints for the flyin are there ! If you enter say N38W017, it found a close one, but not the exact one, like N37W016. The funny thing if I enter correctly the complete code: N3800.0W01700.0 it still found another waypoint ! At the moment I do not know the reason.

But I made a discovery. As I have FSNAV, I just realized that FSNAV identifies and shows on its map the oceanic waypoints with a different coding...the same way as the AIRAC database ! There, N38W17 = 3817N, also N3820W = 3820N. Guess what happened ... I entered 3817N into the FMC (the same code format as it is stored in the AIRAC file) and the bloody computer found it precisely !!! It seems, if it does not need to "decode" then it can identify easily the waypoints.

I found several versions of the available code, like 0000N or 00W00 or 0000S etc... always only 1 letter, and 4 digits. I think after the position of the letter (middle or end) it gives a clear longitude and latitude location for the waypoint. So 3817N means N38W17 ... it is the perfect time for somebody to found out the system behind the scenes

The AIRAC file can be found under FS2004\FMCWP\NAVDATA\wpNavFIX.txt ...have a nice time analizing it

[EHM-1617 Iain]

I just entered then as custom waypoints (in the 737NG). They showed up as WPT01 and WPT02. Then I checked the PLAN view to see they were in the right place.

I had to dig out the manual, as it wanted N00000W000000 form, so it was N38000W017000 etc.

Didn't realise that waypoint like that would be in the AIRAC, thanks for the tip.

[EHM-1001 Robert]

I think I discovered the logic behind the coding system. Here is a pic of the system:



You can see, that for Longitudes smaller than 100, there are 2 digits. When Longitude coord goes beyond 100 degrees, the cardinal letter drops between the two numbers, making a 100 sign, and the 2 digits shows the rest above 100.

More simply, if you fly on a NAT track, because you are on the Northern hemisphere, and below 100 degrees West, you can always enter xxxxN waypoint format into the FMC. An example: 38N/17W = 3817N programmed.

[EHM-1365 Benjamin]

Originally posted by SirRoberto
If you enter say N38W017, it found a close one, but not the exact one, like N37W016. ... At the moment I do not know the reason.

Hi Robert,

This is a known bug on the 747, however, if I recall correctly, it is only a problem in displaying the correct label - you WILL still end up at the position that you entered.

[EHM-1001 Robert]

Oh, really ? Thx for the info, I will try it next time then