Real world ops question: CDU ATC button

[Will]

Hello, here's a question for the real-world 744 flyers or anyone else with first-hand knowledge.

When do you use the ATC button on the CDU and the ATC/LOGON feature?

On the one hand, I could see people logging on to Center before pushback and then continuing to update the logon with the correct Center as the flight progresses. But on the other hand, I could see it perhaps as something done inflight only when VHF or HF radio coverage is expected to be spotty.

So when do you use the CDU to log on to ATC... preflight? Or only under certain conditions? (And if so, what are those conditions?)

Thanks.

[Jeroen Hoppenbrouwers]

I am not a pilot but I do build this ATC stuff for a living.

For 744s, the ATC button is associated with FANS-1/A, the text communication system between pilots and air traffic controllers. This is a fairly old system that originated in the 1980s. It has been in extensive use over the major oceans and is currently mandatory to get the preferred routes. However it is typically not being used over land masses. Exceptions do exist, such as Northern Canada.

Typically you log onto FANS when approaching coast-out. Of course if you depart from Sydney or Melbourne on an oceanic track, this may be pretty much directly, and you may actually log on before takeoff. But all tower and approach control is always done by voice.

FANS (and the European mainland LINK2000+) is designed for relatively quiet route segments, where there is no immediate (seconds) response required. It takes a lot of the communication overhead away from often overloaded and bad quality HF connections.


Hoppie

[evaamo]

Sorry to revive an old thread guys, but I have a few questions myself (I'm new to PSX!):

I understand PSX doesn't model SATCOM, only VHF for ACARS/CPDLC. How does the simulated communication take place then, between ATC/Company and the aircraft when VHF isn't available? Specially in remote areas or oceanic crossings. I'm curious since I thought FANS-1/A defaulted to SATCOM on oceanic routes due to the lack of VHF coverage.

I haven't performed long flights yet, so I'm curious.

Thanks in advance!
-Enrique

  haven't performed the first long flight yet

[IefCooreman]

Actually there has been a lot of development in the CPDLC area. There are the areas where it is mandatory or the general standard (L888, Atlantic,...). It is also used frequently in other remote areas (ie I have used it over the Arabian Sea where you lose contact VHF with Mumbai, in Myanmar,...).

Even Maastricht uses it nowadays (I have even used it coming in from the Middle East and landing in Amsterdam). Coming in east- or westbound from the Atlantic you get CPDLC coverage as well with Gander/Moncton domestic or Shannon in the other direction, although it kinda depends on the controllers preference. In these regions it's more like a backup although I've made it once to Boston where the last voice (selcal checks excempted) contact was with Shanwick radio (you do monitor VHF overland though).

We prefer to try the CPDLC if we can because it is easy and safer, especially during quite nights. It's been a while since I've been to Amsterdam, but at the time it was very unknown to foreigners the service was available. We were happy to show-off we did know about it :-)

[Hardy Heinlin]

Hi Enrique,

regarding CPDLC controller areas, their borders, names and availabilities: PSX's CPDLC model doesn't check these. For training, on the LOGON page, you can enter any 4-letter ICAO code. It will always work, even over the ocean (as long as the VHF C transceiver is operative). This simplification is necessary because there is no database of area controllers and SATCOM stations in PSX.


Cheers,

|-|ardy

[torrence]

Hi Enrique,

regarding CPDLC controller areas, their borders, names and availabilities: PSX's CPDLC model doesn't check these. For training, on the LOGON page, you can enter any 4-letter ICAO code. It will always work, even over the ocean (as long as the VHF C transceiver is operative). This simplification is necessary because there is no database of area controllers and SATCOM stations in PSX.


Cheers,

|-|ardy

Note however, if you are using PFPX for your flight plan, this information is included for the waypoints at the relevant boundaries (and on PFPX maps).  So if you want you can use these to simulate contacting the appropriate centers - it's just not required, as Hardy says.  I recently flew a North Atlantic crossing with PSX, switched to CPDLC after Shanwick and contacted EGGX and then CZQX approaching Canada, while monitoring the VHF and HF freq.  PSX gives you a 'Resume own navigation' call when you log into CPDLC to let you know that's primary for coms.  Found that the robot CPDLC also gave me some things to do while en route (tune-able with the CPDLC setting)  - 'report crossing', 'cross XXXX at or before HHMM Zulu' etc.  And I found I could request step climbs successfully per my flight plan.  It does give you the illusion that there's at least 'somebody out there'  .

Cheers,
Torrence

[evaamo]

Thanks Hardy and Torrence for your replies! I will perform my first Atlantic crossing in PSX this afternoon, so it's good to know how things work in advance. I'm also a PFPX user, so thanks for the tip Torrence.

Cheers!
-E