What are the advantages, disadvantages and current state of affairs for text-based ATC?

This answer has a rather interesting (and quite lengthy) discussion, on a concept of using text-based rather than voice-based communication between ATC and the cockpit. As it turns out, the FAA has some plans for that already as mentioned by @reirab. Being a simmer rather than a pilot, I've always found text-based ATC quite convenient (it provides a direct reference to your own instructions as well as instructions to others on your frequency), but the discussion in the linked answer showed some pilots opposed to such a system. My question is twofold:

• What is the current state of affairs of this concept? Are there specific methods of implementation across various instances - e.g., FAA, EASA, ICAO or other regulatory bodies - and do aircraft (systems) manufacturers anticipate such systems, or would perhaps a software update suffice on modern aircraft?

Edit: Perhaps it's better to concentrate mainly on IFR traffic, since their procedures are more formal (spacing, landing sequence etc. are decided by ATC) and things like voice call-outs (e.g., the nice voice that calls you a retard in an Airbus also calls for a go-around) are available at no extra cost.

• This may be better to split into two questions. – fooot Nov 11 '15 at 15:56
• @fooot I considered that, but I thought the answers would probably be very similar (people adding regulations to their advantage/disadvantage list, people adding advantages/disadvantages to their regulation overview) and the advantages/disadvantages might get too opinion-based without cross-checking with the current state of affairs. – Sanchises Nov 11 '15 at 16:20
• The answers so far seem to address the advantages/disadvantages, so the state of affairs in implementation/regulation will probably be a separate answer. – fooot Nov 11 '15 at 16:25
• Regarding your edit - the voice callouts are the plane speaking to the pilot. They are still for the pilot to choose what to do, and to communicate that as required to ATC. I don't see the relevance here? I also disagree that IFR is "more formal" - VFR communications are also prescribed and formal. – Dan Nov 11 '15 at 16:51
• @Dan Urgent (or perhaps all) ATC messages addressed at the plane itself could be called out by the plane itself (and acknowledged by a nice button labelled "Acknowledge" or similar) to reduce radio clutter since obviously, something went wrong for ATC to order a go-around. I'm not talking about pilot-initiated go-arounds, although that could easily be linked to the TO/GA button, again reducing workload. (Note that I'm advocating this technique strongly to spark a debate, not because I'm too naive to see the downsides) – Sanchises Nov 11 '15 at 17:01

I'm a newbie pilot, but I wanted to give the obvious example that crossed my mind when I read your question. In the UK GA world we have to, for example, call up to say we're on final approach. Finals can be a pretty busy time for the pilot, and at any kind of busy GA airport you're likely to have something along the lines of the following discussion:

(Note in my example, my airport has an "Information Service" rather than full blown ATC, but nonetheless - the example stands)

Me: "G-AB Finals, Runway 16"

Tower: "G-AB, Runway Occupied"

Me: "Continuing, G-AB"

This is me telling the controller that I'm aware I can't actually land, but I'll continue flying my approach path down towards some kind of decision height - somewhere around 300'. If I hear nothing again, I'll go around.

Tower: "G-AB, Land At Your Discretion"

Me: "Landing, G-AB"

I now continue my landing, except I'm not happy with my approach so I now declare a go around

Me: "G-AB, Going Around"

Tower: "G-AB, Roger"

Remember that all of the above is going on while I'm setting flaps, keeping on the glideslope, watching the runway and maintaining my airspeed.

Now also, imagine the alternative:

Tower: "G-AB, Land At Your Discretion"

Me: "Landing, G-AB"

So I now have clearance to land. I carry on, there's a bit of a crosswind and I'm working hard. I cross the airport boundary and I'm concentrating on the runway.. Unbeknown to me, a small dog/child/whatever has broken loose and is charging across the grass to the runway:

Tower: "G-AB, Go Around, I say again, Go Around"

Me: "Going Around, G-AB"

In less than 2 seconds the danger is gone, and the tower know now that I've understood and acknowledged. Now in no world am I ever going to be looking down at a screen during that moment - even if a message came through and beeped/bonged or whatever - my concentration will be on landing. Now you might argue for a specific "Go Around" call/button or whatever - but how many of those different things will we end up with. I simply can't imagine a situation where I won't need my headset on and radio tuned.

I'm not saying any of this stuff will never come in, but pressing a button to talk and listen is much more favourable to typing or reading something during critical phases of flight. At best, I can imagine it complementing some of the more mundane messages and perhaps Ground Controllers.

An ATIS text system might be nice, and I imagine routing and similar will be useful - but I can't imagine it taking over voice completely. Sometimes you just can't beat talking - there's a reason people still e-mail the line "I'll call you".

Beyond that - during those radio comms every aircraft in the vicinity now knows that G-AB is on Finals. This is incredibly important to GA traffic operating in VFR because pilots work hard to keep a mental picture of whose where - not to the degree the tower does, but if someone is following me but doesn't have visual (Very common - planes are surprisingly hard to spot), or loses visual, they know exactly where I am and what I'm doing.

The aircraft that's just touched the threshold also knows that control are aware the runway is occupied and hasn't just cleared an aircraft to land.

• Finals? How many are there? ;) – Simon Nov 11 '15 at 16:01
• @Simon With my flying, at least 3 per landing ;) – Dan Nov 11 '15 at 16:01
• @Dan Reminds me of the many, many Report final final version.pdf files on my hard drive... – Sanchises Nov 11 '15 at 16:26

The main advantages of text based ATC over voice based communication are

• Earlier messages can be recalled

• Messages can be printed

• Messages can be read by automated systems, allow clearances to be loaded into the FMS

• No inaudible messages due to radio static noise or simultaneous transmission

• Time saving and frequency congestion reduction when transmitting and confirming position reports, which otherwise can take up to 20-45 minutes on an HF frequency to wait one's turn and then transmit on a noisy frequency.

• time delay for urgent messages

• not able to bring across emotions, e.g. when giving a critical instruction to avoid disaster

• since the communication is private, other parties can't listen in and don't know what is going on: loss of situational awareness.

This makes text based ATC unsuitable for the TMA and CTA. However in busy/large enough route sectors, the disadvantages are not an issue since there are rarely time critical messages and traffic situation awareness is of less importance.

Detailed information can be found in the ICAO Global Operational Data Link document.

Text based ATC was developed as part of the Future Air Navigation System (FANS) and is known as Controller-Pilot Data Link Communications (CPDLC). It has been in limited operation since the end of the 1990s. Due to technical problems the uptake has been slow initially.

Whilst the system is far from perfect today, its use is increasing. CPDLC is in use in En-route airspace over Europe and over the North Atlantic (NAT).

From 2018, all IFR flights above FL285 in Europe have to be equipped with CPDLC.

The main concern with text ATC is the loss of situational awareness.

When a controller issues an instruction, and the pilot responds, everyone else on that frequency also hears what's going on. This is a major part of maintaining situational awareness and text based solutions, to my knowledge, have not yet come up with an alternative.

Situational awareness is most important when things are busy which also co-incides with the times when reading or writing text is more difficult.

Until these problems are solved, I can't see text replacing radio any time soon. It may well augment it, for example by passing routing clearances which in general are not useful to others in maintaining awareness.

• Unfortunately sometimes crippled by the fact that several languages are permitted for IFR instructions (besides English at least French, Spanish, Russian, not sure what else) and any language is permitted for VFR information. So in many places it is common that the controller talks to different crews in different languages and situational awareness goes down the drain (and when there is an incident, investigators always suggest to stick to English, but nobody ever mandates it). – Jan Hudec Nov 11 '15 at 17:09
• At latest since the invention of IRC we found ways to also distribute text messages to multiple participants, just like voice communication. – yankee Nov 11 '15 at 22:55
• @yankee So all pilots under the same control should be reading all of these text messages? It's easy, with practice, to listen to the radio calls that are important to you. E.g. if I'm on the ground, I'll probably ignore requests to taxi from a terminal at the other end of the field but one from the terminal I am at will definitely register. This can be done whilst still maintaining lookout, scan etc. I'd need to see convincing evidence that the same is true for text messages. – Simon Nov 13 '15 at 16:31

A very different answer to my first. While there's something of a catalogue of errors in this, the following audio recording is a clear display of why situational awareness is always a good thing to have:

In the recording, Flight 1448 accidentally finds themselves on the Active Runway. Despite realising their mistake and speaking up, the controller (for whatever reason) simply asks them to hold while giving take off clearance to another aircraft on the same runway. Sensibly, after hearing what's going on, the second aircraft opts to hold instead of taking off.

• I give you the deadliest aviation accident caused by (amongst others) radio clutter and unclear voice communication, or this almost-incident caused by misheard callsigns. Also, in your video example, the pilots can just see the takeoff clearances on their screen: just like there is a crewmember monitoring the radio, there will be a crewmember monitoring the ATC screen. I think your other answer is better. – Sanchises Nov 11 '15 at 17:51
• @sanchises You misunderstand - it was the aircraft WITH takeoff clearance who'd overheard the issue and decided to hold. It' s a fair rebuttal - but I feel you're playing devils advocate somewhat. – Dan Nov 11 '15 at 17:52
• Guilty as charged – Sanchises Nov 11 '15 at 18:00

In the US, DataComm is coming. First to Clearance Delivery in the busier airports and soon to EnRoute aircraft. The pros and cons are a lot to discuss. More than a two beer topic.

The intent of DataComm is mostly for commercial aviation with appropriate equipment, not for the private or small business user. Eventually, the plan is to have the digital clearance uploaded automatically to the onboard nav systems. The advantages are manifold; reduction in missed readbacks, speedier reroute acknowledgements, reduced frequency congestion.

I don't believe there will a time when voice comm is completely replaced just due to the huge number of variables in an operational environment. Just like the final approach example that was given. For frequent routine communications though, it can't come soon enough!