PDC Question

[Nicholas Lim]

Why do I always get PDC clearance PM from ATC but some other pilots get read back from ATC ? Once I was in a non crowded airport but I got PDC PM but the other pilot got read back. 

Edited June 12, 2021 at 10:22 AM by Nicholas Lim

[Koen Meier]

5 hours ago, Nicholas Lim said:

Why do I always get PDC clearance PM from ATC but some other pilots get read back from ATC ? Once I was in a non crowded airport but I got PDC PM but the other pilot got read back. 

Some controllers have an alias set up and immediately sent you a pdc via text when you login. I personally do not like that and rather ask for clearance myself via voice or through hoppie acars pdc.

 

[Trevor Hannant]

4 hours ago, Koen Meier said:

Some controllers have an alias set up and immediately sent you a pdc via text when you login. I personally do not like that and rather ask for clearance myself via voice or through hoppie acars pdc.

 

👆 This...   If I want PDC, I'll request it. it should not be mandatory

[Ross Carlson]

It's a very subjective thing ... I love getting a PDC without having to ask for it.

Edited June 12, 2021 at 11:27 PM by Ross Carlson

[Alistair Thomson]

Yep. There is a kind of duet sung between ATC and pilot normally, regarding the procedures and clearances in preparation for flight, and that duet is sung continually  during the flight, with the lyrics of both singers (ATC and pilot), changing as the flight progresses.

Pre-departure clearance is one of the verses on the way. It's been customary for a pilot to get set up with the flight plan loaded in the FMS, and while the pax are loading, to ask for clearance when the pilot needs it, in good enough time so that any variations from the filed plan required by ATC can be accommodated. Having that comfortable duet interrupted by an asynchronous text clearance seems to break the natural order of things, maybe even spoiling the moment for some.

Text PDC can be like that, but if it is realised that all that is happening is that your clearance is arriving before you request it, you should be comfortable knowing that you'll be able to get to it when you're ready, to respond to it when you are ready, and that you won't have to ask for it.

Of course, that is different from the song you have rehearsed, but it's like listening to a recording of the song: you can still being responsive to that recording.

However, I don't think the replies to the OP's post actually answers his central question, which is why it seems to be happening to him but not to everyone else. It's as if ATC is selecting him, but no one else, for text PDC. I have no clue about why that might be, but someone might.

My comments above are simply to say that an "unwanted" text PDC is only unwanted if the pilot decides that it has to be responded to immediately. It doesn't, until the pilot is ready to respond, in which case it simply saves the airtime of both pilot and ATC.

[Andre Almeida]

7 hours ago, Alistair Thomson said:

My comments above are simply to say that an "unwanted" text PDC is only unwanted if the pilot decides that it has to be responded to immediately. It doesn't, until the pilot is ready to respond, in which case it simply saves the airtime of both pilot and ATC.

But same could be said for much else. We might as well send pilots still 500 miles from their top of descent a private message telling them their STAR, and whenever they're ready they'll read it back. They're still so far away from where it's needed that they don't necessarily have to read it back immediately.

I don't fly much in the US, but the few times I did and received "PDC" I did not like it. If I want to receive instructions via text message I'll file /t. If I'm /v I expect things to happen via voice, unless I request otherwise.

[Ben Lindsey]

33 minutes ago, Andre Almeida said:

I don't fly much in the US, but the few times I did and received "PDC" I did not like it. If I want to receive instructions via text message I'll file /t. If I'm /v I expect things to happen via voice, unless I request otherwise.

In the US, PDCs see relatively widespread usage, even in the real world. Apps like ForeFlight allow basically anyone to get a PDC at eligible airports. 

In my experience as a VATSIM controller, a lot of the US PDC culture has to do with the pure amount of time a clearance can take in the US. Working a busy center frequency top-down, it’s so much easier to type an alias and send a PDC when it’s an option for that airport. If you want a voice clearance, you can always ask, or put something like “no PDC” in your remarks. 
 

To answer the original question, there’s a few reasons why the method of clearance could be different from airplane to airplane. Some people may request a voice clearance. If you’re on a center frequency, you may be hearing people at different airports that are not eligible for PDCs. For example, only the larger/busier airports are eligible (in the US). If an amendment needs to be made, sometimes a PDC won’t be issued, and a voice clearance will be used.  These certainly aren’t the only reasons, but they’re some of the most likely. 

[Andre Almeida]

1 hour ago, Ben Lindsey said:

In the US, PDCs see relatively widespread usage, even in the real world. Apps like ForeFlight allow basically anyone to get a PDC at eligible airports. 

We also do PDC over here, just not via PM. We use Hoppie CPDLC, either through TopSky or the vSMR plugin. That way pilots get their PDC in the cockpit instead of vPilot. And only if they request it.

However, I understand why the US on VATSIM does it via PM, it does save time to just write .clr or similar and hit enter instead of having to say it all on frequency. And during busy times I'm sure it can be a life-saver. I personally don't like it too much though. But anyway, that's off-topic. 😛 

[Trevor Hannant]

12 hours ago, Ben Lindsey said:

In my experience as a VATSIM controller, a lot of the US PDC culture has to do with the pure amount of time a clearance can take in the US. Working a busy center frequency top-down, it’s so much easier to type an alias and send a PDC when it’s an option for that airport. If you want a voice clearance, you can always ask, or put something like “no PDC” in your remarks. 

My last vPilot PDC came from a GND controller with three aircraft on the ground.   it came within 30 seconds of me logging onto the network so was still powering the aircraft up which means that by the time I was ready, it had expired.

I get the reasoning for busy CTR controllers, I don't get the reasoning for people who're quiet.

[Dhruv Kalra]

42 minutes ago, Trevor Hannant said:

My last vPilot PDC came from a GND controller with three aircraft on the ground.   it came within 30 seconds of me logging onto the network so was still powering the aircraft up which means that by the time I was ready, it had expired.

I get the reasoning for busy CTR controllers, I don't get the reasoning for people who're quiet.

A clearance in the USA, PDC or not, is implied to be valid for two hours. By what definition do you claim it “expired”?

[Andreas Fuchs]

Hi all,

maybe we could all accept that there simply are differences in the systems on both sides of the Atlantic? It's like in the real world: when we cross the Pond from Europe to North America, we actively have to request our oceanic clearance through our AFIS (ACARS) interface. Coming back to Europe, they will automatically send it to us when we get closer to our oceanic entry point. Conclusion: flying westbound, we have to request our datalink clearance, going east we need to monitor the system and do something if we do NOT automatically receive it. The same goes for PDC/DCL at VATSIM, it's just different.

Not a big deal, me thinks.

[Robert Shearman Jr]

It is surprising to me how many people seem really put off by this.  It's a private message.  If you don't want it, ignore it and call for your clearance verbally anyway.

My own logic for a PDC is generally that if it's (a) an aircraft with an FMC and (b) there's nothing major I need to amend with the route, I'll send it as soon as I've had a chance to look it over and validate it.  Whether I'm busy or not is often not a factor.  Like Dhruv mentioned, you can call me for push/start or taxi five minutes later or an hour later, I don't care.

If I sent a PDC and you still call by voice asking for IFR clearance, I might ask you if you received the PDC, but if you say you didn't, I'll generally ask whether you want a re-send or want it by voice.

And yes, I realize many aircraft without FMCs can also receive PDCs nowadays but since I can't tell whether a GA pilot is simulating the use of ForeFlight or not, I generally assume non-FMC-equipped aircraft are expecting clearance by voice.

If that annoys you somehow, please feel free to put something in your remarks like "NO PDC" or "VOICE CLEARANCE PRRFERRED" and I'll be happy to honor that as long as I see it and don't forget.

Edited June 14, 2021 at 07:34 AM by Robert Shearman Jr

[Kirk Christie]

1 hour ago, Robert Shearman Jr said:

If I sent a PDC and you still call by voice asking for IFR clearance, I might ask you if you received the PDC, but if you say you didn't, I'll generally ask whether you want a re-send or want it by voice.

Seems like an excessive waste of time asking questions when you can just give the clearance and move on.

 

[Alex Ying]

6 hours ago, Kirk Christie said:

Seems like an excessive waste of time asking questions when you can just give the clearance and move on.

 

As mentioned above, sending a PDC is a huge timesaver in the US where it can take a 2+ minutes to give a clearance over voice if the departure procedure requires vectors or climb restrictions. I'm not particularly familiar with other parts of the world, but I know in a lot of Europe, clearances are a lot shorter than in the US. If I can send a PDC that you can asynchronously read, it saves me tons of time when I'm vectoring 10 planes in the air.

[Robert Shearman Jr]

7 hours ago, Kirk Christie said:

Seems like an excessive waste of time asking questions when you can just give the clearance and move on.

 

Giving the clearance verbally when one could read it from their message is actually the bigger waste of time in my opinion.

[Ross Carlson]

Plus, having the PDC sitting there in a private message tab makes it easy to reference later rather than having to write down the verbal clearance, which is also subject to transcription error.

Edited June 14, 2021 at 06:24 PM by Ross Carlson

[Raaj Patel]

Like some of y'all, I too don't like to receive my clearances over PDC. I have something in my remarks stating that I don't like PDC's and would prefer a voice clearance and I haven't had any issues with it so far. Most controllers are easy going and unless they are absolutely slammed they will try to accommodate your requests.

Personally I don't like PDC's cause I like to fly in VR and I have to lift my headset up to read the PDC and sometimes the VR gets unplugged. Its just annoying, but every controller has accommodated my request without complaining.

[Kirk Christie]

7 hours ago, Robert Shearman Jr said:

Giving the clearance verbally when one could read it from their message is actually the bigger waste of time in my opinion.

I never said sending or receiving a PDC was a waste of time, I said asking them weather they got it and/or offering to send it again and awaiting their reply via voice communications is the waste of time when you could have used that time just to verbally send their clearance again, please read and understand the specific part of your post that I quoted and referenced.

 

ABC123: DEL request clearance

DEL: did you receive clearance via PDC

ABC123: yes/no

DEL: would you like me to send it again?

ABC123: yes/no 

ABC123: with PDC readback, cleared VIA xxxx climb xxxx Squawk xxxx

DEL: correct contact ground xxx.xx for push

Waste of time.....

Vs

ABC123: Request clearance

(delivery controller... hmmm must not have got/seen my PDC)

DEL: ABC123 cleared destination via xxxxx, climb xxxxx squawk xxxx departures xxxxx

ABC123: cleared destination via xxxxx, climb xxxxx squawk xxxx departures xxxxx

DEL: correct, contact ground xxx.xxx for push

 

Just avoided thay verbal ping pong asking questions to see if they got/saw the PDC and asking again if they would like it resent, massive over complication that isn't needed when you can just provide the service and move on.

 

If they are calling your for clearance you should be smart enough to establish that they have not seen your PDC and the time saving factor of them reading the PDC and responding has already been lost.

Edited June 15, 2021 at 12:16 AM by Kirk Christie

[Robert Shearman Jr]

It's teaching them to fish, Kirk.  It's an investment in "next time I hear the PM message I'll know it might be my clearance."

And PDCs don't require readbacks in the US anyway.

[Ross Carlson]

2 hours ago, Kirk Christie said:

If they are calling your for clearance you should be smart enough to establish that they have not seen your PDC and the time saving factor of them reading the PDC and responding has already been lost.

So why make it worse by reading the clearance over voice and then listening as they read it back? Much faster to just direct them to check their private messages. If they, for some reason, refuse to read the PDC and will take it only by voice, then they can say so. Like Rob says, teach them to fish. If they really hate fishing, then you can spoon-feed them. 

[Koen Meier]

15 hours ago, Ross Carlson said:

Plus, having the PDC sitting there in a private message tab makes it easy to reference later rather than having to write down the verbal clearance, which is also subject to transcription error.

Having it in the mcdu/fmc and printed out works the same.

[Alistair Thomson]

12 hours ago, Robert Shearman Jr said:

PDCs don't require readbacks in the US anyway

That would make it more sensible to always use text PDCs. It would save a lot of airtime. Two minutes plus for a US departure clearance?? (re. Alex Ying above)

But I believe that every ATC instruction requires a read-back, so does this imply that, in the US at least, a PDC is not an instruction and therefore a pilot can depart on any route whatever?

[Ross Carlson]

4 hours ago, Koen Meier said:

Having it in the mcdu/fmc and printed out works the same.

Sure does ... and if everyone had that capability, that'd be great! I hope we'll eventually get to the point where everyone has the ability to receive not only PDCs but also full CPDLC uplink/downlink messages, including direct integration into both the pilot and controller clients, not requiring any separate software and server. There has been lots of discussion in that area, but no actual development progress yet, unfortunately.

[Alex Ying]

48 minutes ago, Alistair Thomson said:

That would make it more sensible to always use text PDCs. It would save a lot of airtime. Two minutes plus for a US departure clearance?? (re. Alex Ying above)

Here's a typical clearance out of JFK (this does not include things like route amendments, or cruise level amendments, all things that add more time)

"AAL123, cleared to Boston Logan Airport, Kennedy 5 Departure, Canarsie Climb, radar vectors MERIT, then as filed. Climb and maintain 5000, expect FL210 10 minutes after departure. Departure frequency 135.9. Squawk 1123."

That takes 20-30 seconds for an experienced controller to read on its own. Then the pilot has to process, make sure they understood the clearance, and read it back. Call it a minute or so. Tack on any corrections because there's a lot of information in there and you can easily get over 2 minutes for a single clearance.

Given that you don't know what level of proficiency the pilot has (brand new pilot who's flying out of New York for the first time vs. someone who's been flying in and out of Kennedy for years), I block out a long period of time where I know I won't have to give instructions to any airborne planes in order to account for that variability.

Edited June 15, 2021 at 02:22 PM by Alex Ying

[Andreas Fuchs]

3 hours ago, Alistair Thomson said:

But I believe that every ATC instruction requires a read-back, so does this imply that, in the US at least, a PDC is not an instruction and therefore a pilot can depart on any route whatever?

No, of course not. By setting the assigned transponder code you acknowledge the receipt of your clearance.