Any ATC Expert here to clarify CPDLC Process?
Thread Starter
Joined: Nov 2007
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From: Mars
Any ATC Expert here to clarify CPDLC Process?
Few questions regarding CPDLC. MS Sim experts captains I know everything and alike please don't comment.
Looking for a legit info from experts only.
1. logging into a centre sometimes doesn't work. why? is there any way to make it happen? unconfirmed information I got is that sometimes registration doesn't match what ATC has on their side (scheduled ops)
2. how the process of communication via CPDLC look like? if I send a request say level change request where is that message going to?
is the ATC guy on the radio (say area control or oceanic) same that gets the CPDLC message? what is the exact process of issuing clearance and sending it via CPDLC to the plane?
3. any clarification on FANs please? planes while logging let tick FANs box but not always. Does it depend on the centre I am trying to log into?
Please comment.
Looking for a legit info from experts only.
1. logging into a centre sometimes doesn't work. why? is there any way to make it happen? unconfirmed information I got is that sometimes registration doesn't match what ATC has on their side (scheduled ops)
2. how the process of communication via CPDLC look like? if I send a request say level change request where is that message going to?
is the ATC guy on the radio (say area control or oceanic) same that gets the CPDLC message? what is the exact process of issuing clearance and sending it via CPDLC to the plane?
3. any clarification on FANs please? planes while logging let tick FANs box but not always. Does it depend on the centre I am trying to log into?
Please comment.
Joined: Mar 2011
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From: Earth
To answer that question we probably need to know what type of airplane you fly and where you're trying to logon (which FIR/UIRs).
Explanations that I'm sure will be blasted for over simplification and inaccuracy:
3 main types of CPDLC "schemes"
FANS CPDLC (Oceanic) - Can use SATCOM, VHF, or HF datalink, mostly used in oceanic FIR's but used in some continental airspace such as Alaska and Canada (India/Myanmar?). Logon generally also establishes an ADS-C contract.
KUSA CPDLC - United States VHF only with more limited messaging options, not used in conjunction with ADS-C. Uses a FANS 1/A type scheme.
ATN CPDLC - VHF only European scheme which requires a multi-mode reciever capable of ATN logon. If your airplane isn't equipped to use ATN, and in some FIR's (Maastricht/Switzerland/Germany/Poland) if your tail number isn't on the approved list of aircraft (whitelist), you won't be able to logon. Used with ADS-C. CPDLC logon is required in many European FIRs if your airplane is capable of using their system.
Hybrid - some UIR's such as London, Scottish, Shannon use a dual system in which FANS or ATN systems can be used.
So, if you aren't properly equipped for the specific CPDLC scheme or you aren't on an approved list of users (by tail number), then you might not be able to logon depending on the airspace.
.
Explanations that I'm sure will be blasted for over simplification and inaccuracy:
3 main types of CPDLC "schemes"
FANS CPDLC (Oceanic) - Can use SATCOM, VHF, or HF datalink, mostly used in oceanic FIR's but used in some continental airspace such as Alaska and Canada (India/Myanmar?). Logon generally also establishes an ADS-C contract.
KUSA CPDLC - United States VHF only with more limited messaging options, not used in conjunction with ADS-C. Uses a FANS 1/A type scheme.
ATN CPDLC - VHF only European scheme which requires a multi-mode reciever capable of ATN logon. If your airplane isn't equipped to use ATN, and in some FIR's (Maastricht/Switzerland/Germany/Poland) if your tail number isn't on the approved list of aircraft (whitelist), you won't be able to logon. Used with ADS-C. CPDLC logon is required in many European FIRs if your airplane is capable of using their system.
Hybrid - some UIR's such as London, Scottish, Shannon use a dual system in which FANS or ATN systems can be used.
So, if you aren't properly equipped for the specific CPDLC scheme or you aren't on an approved list of users (by tail number), then you might not be able to logon depending on the airspace.
.
Joined: Jun 2013
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From: Róisín Dubh
"Sometimes can't log on to CPDLC"....there are a myriad of reasons why this can happen but honestly sometimes it's a mystery. I see it in ATC all the time, aircraft having issues when switching between SATCOM/VHF and FANS & ATN. The reliability of the service had degraded since COVID for whatever reason. Voice comms (VHF/HF) won't be going anywhere for decades.
Add in RFI/GNSS jamming messing with all kinds of on board systems in Eastern Europe/Middle East/Africa/Asia preventing log on for the remainder of the flight too.
Add in RFI/GNSS jamming messing with all kinds of on board systems in Eastern Europe/Middle East/Africa/Asia preventing log on for the remainder of the flight too.
Thread Starter
Joined: Nov 2007
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From: Mars
Thank you for your informative input. The plane is B787 and mostly the issue with logging occurs over Africa and India Oceanic. Quite often in Europe as well.
I remember that I never had an issue with Anchorage but that was before Covid
I remember that I never had an issue with Anchorage but that was before Covid
Joined: Mar 2011
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From: Earth
I generally had good luck in the B744 with Dakar Oceanic but can't recollect using it much near Africa aside from that. India is hit or miss and often they only seem motivated to use it in Mumbai, Chennai, or Kolkota oceanic if HF is unusable. Over the past 5 years it did get better and I find India Oceanic CPDLC to be fairly reliable in maintaining logon; recieving a response to a pilot initiated CPDLC request is another matter and often they seem to prefer just to give you an HF SELCAL when negotiating. Over land in India they seemed to often accept the logon then terminate the connection if VHF voice was in use, I don't know why, maybe they don't like to keep it active unless there is a problem with VHF. I can't recall for certain but I believe these FIR's are using a FANS type scheme which should permit VHF, SATCOM, or HF and the B787 should have no issues. In my experience intermittent CPDLC in these regions is due to some sort of infrastructure limitation or procedural reluctance on the ATC side. Sometimes I have had success in making a voice VHF or HF call and requesting that the controlling agency accept my CPDLC logon, almost as if they didn't see it it until it was brought to their attention.
Last edited by RandomPerson8008; 9th October 2024 at 00:28.
Thread Starter
Joined: Nov 2007
Posts: 92
Likes: 15
From: Mars
To answer that question we probably need to know what type of airplane you fly and where you're trying to logon (which FIR/UIRs).
Explanations that I'm sure will be blasted for over simplification and inaccuracy:
3 main types of CPDLC "schemes"
FANS CPDLC (Oceanic) - Can use SATCOM, VHF, or HF datalink, mostly used in oceanic FIR's but used in some continental airspace such as Alaska and Canada (India/Myanmar?). Logon generally also establishes an ADS-C contract.
KUSA CPDLC - United States VHF only with more limited messaging options, not used in conjunction with ADS-C. Uses a FANS 1/A type scheme.
ATN CPDLC - VHF only European scheme which requires a multi-mode reciever capable of ATN logon. If your airplane isn't equipped to use ATN, and in some FIR's (Maastricht/Switzerland/Germany/Poland) if your tail number isn't on the approved list of aircraft (whitelist), you won't be able to logon. Used with ADS-C. CPDLC logon is required in many European FIRs if your airplane is capable of using their system.
Hybrid - some UIR's such as London, Scottish, Shannon use a dual system in which FANS or ATN systems can be used.
So, if you aren't properly equipped for the specific CPDLC scheme or you aren't on an approved list of users (by tail number), then you might not be able to logon depending on the airspace.
.
Explanations that I'm sure will be blasted for over simplification and inaccuracy:
3 main types of CPDLC "schemes"
FANS CPDLC (Oceanic) - Can use SATCOM, VHF, or HF datalink, mostly used in oceanic FIR's but used in some continental airspace such as Alaska and Canada (India/Myanmar?). Logon generally also establishes an ADS-C contract.
KUSA CPDLC - United States VHF only with more limited messaging options, not used in conjunction with ADS-C. Uses a FANS 1/A type scheme.
ATN CPDLC - VHF only European scheme which requires a multi-mode reciever capable of ATN logon. If your airplane isn't equipped to use ATN, and in some FIR's (Maastricht/Switzerland/Germany/Poland) if your tail number isn't on the approved list of aircraft (whitelist), you won't be able to logon. Used with ADS-C. CPDLC logon is required in many European FIRs if your airplane is capable of using their system.
Hybrid - some UIR's such as London, Scottish, Shannon use a dual system in which FANS or ATN systems can be used.
So, if you aren't properly equipped for the specific CPDLC scheme or you aren't on an approved list of users (by tail number), then you might not be able to logon depending on the airspace.
.
I thought it was autonomous with no control over it from the pilot side.
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From: Earth
Originally Posted by Qbix;[url=tel:11747078
11747078]To establish ADS-C contract do you need to be CPDLC connected?
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From: FNQ ... It's Permanent!
Depending on what country is involved and the level of English available, if your attempted logon fails, you can ask ATC to initiate logon from their end.
Thread Starter
Joined: Nov 2007
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From: Mars
ATC is able to log on a plane from their side? How is that possible without sending log on request? I mean technically and practically?
Thread Starter
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From: Mars
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From: The wrong time zone...
Qbix - thanks for your questions, I too am interested in all the answers and I use CPDLC frequently - sometimes much of it is a mystery and GOLD doesn't explain a lot of it.
Joined: Feb 2014
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From: mumbai
HI!
I know that this response is late, but then it is not the case of CPDLC.
Well in Mumbai oceanic airspace, HF is truly a hit or miss. Most pilots just dole out the estimates for the waypoints and do not bother to make position reports unless they need a level change. CPDLC comes in handy but sadly only a little more than half the airplanes are equipped. However, once connected and logged on, the contracts are honored and responses are guaranteed albeit with a lag (RCP 240). Now, no controller worth his salt would want someone else have access to coms ( CPDLC) when VHF is available, which is instantaneous ( no lag here). Now with CPDLC and Surveillance coverage, if available the separation can be reduced for suitably equipped airplanes and optimal altitudes can be assigned to more airplanes.
I know that this response is late, but then it is not the case of CPDLC.
Well in Mumbai oceanic airspace, HF is truly a hit or miss. Most pilots just dole out the estimates for the waypoints and do not bother to make position reports unless they need a level change. CPDLC comes in handy but sadly only a little more than half the airplanes are equipped. However, once connected and logged on, the contracts are honored and responses are guaranteed albeit with a lag (RCP 240). Now, no controller worth his salt would want someone else have access to coms ( CPDLC) when VHF is available, which is instantaneous ( no lag here). Now with CPDLC and Surveillance coverage, if available the separation can be reduced for suitably equipped airplanes and optimal altitudes can be assigned to more airplanes.
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From: mumbai
- Yes, if your operator forgets to update the ATC centers with an updated FPL, especially the REG and CODE( Airframe ID), the CPDLC connection is never successful. This happens when there is a change of airplane prior to departure.
- A level change message goes directly to the controller as a CR ( clearance request)
- Well, when the controller gets the CR, he evaluates the request and the feasibility of acceptance. If traffic permits, he triggers a response containing clear instructions , else UAB ( Unable).
Gender Faculty Specialist
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From: In your head.
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This was pre CPDLC.OTOH, flying across Africa has been made much easier thanks to CPDLC in my experience.
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Qbix : I do not considerer myself an "expert" on CPDLC and refrained from commenting until now especially after "Randomperson 8008" immediately and correctly answered you .
Yes it is like VHS and Betamax but you could add the best system of all , V2000 made by Phillips for those old enough to remember. Nobody won the video's recordings battle ` in the end, as DVDs and now internet streaming came on , as I guess the same will occur with current CPDLCs, a new system will come up and replace everything . Hopefully a global one , but with the current Orange resolution in the US I guess there will be a US system and a European system ...and maybe now there will be a Chinese one as well, and possibly better like the v2000 was ...
Finally , one last possibility you can't log on , especially on a 787 , is you have been jammed or spoofed along the way , your timing might be off ( typically 4 minutes ) and although your message looks like it went off , will be rejected by ATC as out of timing ,and if you're using old FANS-1 , since there is no feedback message with them , you will never know,
That is why we keep voice HF. an expensive 19th century invention , while the Pax are enjoying voice over IP calls free on What's app in the cabin ..
We live in a formidable era...
Yes it is like VHS and Betamax but you could add the best system of all , V2000 made by Phillips for those old enough to remember. Nobody won the video's recordings battle ` in the end, as DVDs and now internet streaming came on , as I guess the same will occur with current CPDLCs, a new system will come up and replace everything . Hopefully a global one , but with the current Orange resolution in the US I guess there will be a US system and a European system ...and maybe now there will be a Chinese one as well, and possibly better like the v2000 was ...
Finally , one last possibility you can't log on , especially on a 787 , is you have been jammed or spoofed along the way , your timing might be off ( typically 4 minutes ) and although your message looks like it went off , will be rejected by ATC as out of timing ,and if you're using old FANS-1 , since there is no feedback message with them , you will never know,
That is why we keep voice HF. an expensive 19th century invention , while the Pax are enjoying voice over IP calls free on What's app in the cabin ..
We live in a formidable era...