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ahammerman

pmdg 777 great circle fmc setup

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Hi, when flying the PMDG 777 when I want to fly a great circle route (ex:EGLL-KJFK) I get coordinates like 4100N and 16000W and i was wondering how you input these into the FMC? If so how because they don't seem to go into the route...

 

Thanks guys

 

Avery Hammerman

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Hi,

 

> FCOM volume 2: Chapter Lateral Navigation (LNAV) page 11.31.12 (PDF page 890).

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i was wondering how you input these into the FMC?
I use the method Romain Roux has referred to. You could also look at the POS INIT page which has coordinates show on it and see what format is used there. The FMC will also accept an entry in that format. However, it a lot faster to use the letter plus 4 digits as opposed to two letters and up to 12 digits.

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So inserting the coordinates in the FMC is just as easy as a fix except you have to compress the coordinate basically?

 

Avery Hammerman

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Hi Avery,

 

If you look at the Chapter I gave you the reference to, the different ways to enter waypoints in FMC whatever they are are very well explained.

Yes, once you know which format to use, it is pretty straight forward.

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 coordinates like 4100N and 16000W how you input these into the FMC?

 

4100N 16000W is a single co-ordinate. A place on the earth's surface.

That place can be seen on Google Maps, here.

 

To enter this into the FMC, there are 3 methods. One of these methods is available for all kinds of co-ordinates including partials (ie 4124.5N 16025.3W).

The other 2 methods are only able to deal with whole degrees.

 

The FMS is not able to take a "Space" character. So 4100N 16000W isn't possible (There's a space between 4100N and 16000W)

 

All aircraft can take the following 2 systems.

 

N4100.0W16000.0

This is the same place as:

N41W160

(Which is only available on Boeing Aircraft!)

 

There is another system available, which is the 5 letter waypoint system.

I am sure you are aware of locations with 5 letter waypoints such as:

RIVET

LIZZI

DOPID

SCUPP

SADDE

LOGAN

5050N

LAMEN

41N60

 

Each "whole digit" co-ordinate has a "5 letter waypoint" position which is able to substitute for the raw co-ordinate.

 

These follow the same format as the image below:

*PLEASE NOTE* That entering 41N60 is not the same location as 4116N or 41W60.

Also remember, all "waypoints" are 5 letters long. so 41N160 isn't a valid identifier of anything.

arinc_424_shorthand.png

 

 

Co-Ordinates have a Latitude component and a Longitude component.

 

Longitude is expressed as a degree away from Equator. The Equator is 00° and the Poles are 90°. You can obviously go either north or south of the equator. N90° is the North pole. S90° is the South pole, and 00° is a 12,756km circle around the earth.

 

Obviously a 12,756km long circle around the earth isn't a "Place".

 

Telling a plane to go to 41°N is like telling someone "Meet me on the longest road in the world at midday" and not telling them where on that road they should meet you.

 

"Hi It's midday and I'm on the road now"

"I'm here and I can't see you!"

"Oh Really? I'm in Siberia, 200km east of Novosibirsk."

"Oh? I'm in Botswana."

 

A co-ordinate needs to positions. So we have latitude. In your case 160°

 

Now you create a position on a 2 dimensional representation of the Surface.

 

N41 is 41° north of the Equator.

W160 is 160° to the west of Greenwich, the location of the British Empires' Naval Academy. Back when Navigation was developing, the British navy was the strongest military power in the world, so when the French wanted to make 0° in Paris... the big British 100 gun Dreadnoughts said no. And so Greenwich is the location of 0°. From the Greenwich Meridian, locations are either East (toward Europe) or West (toward USA). till they meet at the opposite side of the world, the International Date line.

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Alright that make a heck of a lot more sense the what the FCOM had to say... The only thing I was getting wrong was the compressions from 4100N and 16000W to 41N60 if that's correct, obviously when plotting the courses ill have the FCOM examples out until I remember them but that helped a ton thanks Trent.

 

Avery Hammerman

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Avery,

 

Sounds to me that you, as a lot of others, need to seriously study the manuals :rolleyes:

 

Best of luck,

 

Cheers, Richard

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The only thing I was getting wrong was the compressions from 4100N and 16000W to 41N60 if that's correct

 

Just remember this:

Does the latter group of numbers (4100N and 16000W) use a 1 as the first digit?

Yes: replace the 1 with the relevant N, E, S, W: 41N60

If it were no: begin with the relevant N, E, S, W.

 

This format is mostly for reference, only.  What I mean by that, is that it was created to have fewer key entries for crews when copying the flight data from a flight plan that has been printed (and interpreted via the above rule) already.  It's a lot easier to not have to remember the intricacies of that short form.  Just use two extra characters and avoid any confusion: N41W160.

 

As was already mentioned, though, use the CDU itself as a guide.  The PERF INIT page shows exactly how the long form should look.  It's not fun to enter it like that, but it'll work just the same until you consult the manuals  :wink:

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Just FYI, the short form is not encodded in the FMS but is provided by the navdata file wpNavFix.txt. If you open that file you'll find a long list of short form fix names translated into Lat/Lon such as:

 

 

90S80                   90S80-90.000000 180.000000

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