Why don’t datalink change of level clearances include a leaving report, only the maintaining new level report.

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Why don’t datalink change of level clearances include a leaving report, only the maintaining new level report.

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Because the fellow on 135.7 wouldn't have a clue what CPDLC is let alone how to use it?

First up folks, I am not complaining but explaining.
In fact the only thing I now have to do with aviation is looking up to watch you guys go over my cows.

Renurpp your reply demonstrates why we don’t have a perfect system and never will.
Different crews on identical aircraft have different solutions to flying star profiles.
Add different aircraft and FMS to the mix and you get closing/opening situations.

You aint doin’ anything wrong nor is the crew ahead of you or behind you but ATC has to stick their nose in and adjust someone's speed, usually just when you have achieved the profile you want. :(

Sequences are flowed for maximum runway usage at the start of sequence even to the point of adding “pressure” to the mix where there there may be one too many aircraft in there to theoretically fit.
After a while(an hour) gaps start to be added into the mix to help the tower get departures away and will leav you scratching your head about why you were slowed down when there is no-one else around.

Hope this helps.

Ok. My FMS doesn’t work that way (it also wouldn’t fly a level segment for an at or below restriction). If well below the path it will fly a shallow descent with thrust on to maintain the speed.

Approach is not my domain so that's one I'll have to leave for others, any answer from me on that would only be speculation and not likely very accurate. There have been some answers since so hopefully that'll put some light on it.
I'll get to that, but first some background and tangential information...

Generally speaking, when you're operating via CPDLC you'll be out of surveillance and VHF coverage and track and level monitoring is achieved with ADS-C so this response is aimed at that. The Contract part of the ADS-C does several useful things for us. It will specify the reporting rate, with 12 minutes intervals default in OCA from 2014 after MAS370 (it still operates in the background while in surveillance coverage but the reporting rate drops to 40 minutes). It also incorporates 'Waypoint Change Events', Lateral Deviation Events' and 'Level Deviation Range Events'.

WCEs will alert on our screen with an alert called 'ADS Route Conformance Warning' (ARCW) which monitors and compares the FMS Next and Next+1 waypoints to the system flight plan and highlights if a discrepancy exists. This is a very useful alert as it is one of the few predictive alert alerts that we get, which is to say that we can know something is not right before the expected trajectory diverges. This allows time to determine what is wrong and rectify it before it becomes an actual issue (unfortunately these alerts are suppressed within surveillance coverage). We'll see these alerts during weather deviations, if the FMS route is offset by 20 miles, we'll see it (but not if the deviations are flown on headings). We'll also see it when dummy waypoints are added to the FMS (PNRs, full checks, count down to crew change over...). Other times it can pop up if there had been a route change that was filed after the original plan was submitted but the change didn't get incorporated into our system for what ever reason.
If you get a message that says "Confirm Assigned Route", this is probably why. From that point, if the discrepancy continues, we'll either re-clear you by the route that we have filed, or re-clear by your reported route. As long as what we are expecting to happen and what you are expecting to happen match up, everything is awesome. All we want is predictability, we're not focused on where you are now, we are looking at where you'll be in 5 to 300 minutes time (depending on the area of responsibility)...

Next, Lateral Deviation Events. If you go 4.5NM off track, your FMS will tell us and we'll get a warning message on screen. If you go 7nm off track, the system generates a RAM (Route Adherence Monitor) alert and highlights yellow and beeps and carries on. RAM alerts will generate with ADS-C reports or surveillance reports (ADS-B and Radar).

Finally, and getting to the point of the question, Level Deviation Range Events. These work similar to the CLAM alert discussed earlier, but are specified in the ADS Contract that if the aircraft leaves a level, the FMS tells us about it automatically. So why don't you get told to report leaving a level? The FMS does it for you. As for the 'Report Maintaining' report request, there are a few reasons in tandem for this. First is that unlike leaving a specified level range, the FMS will not by default tell us entering a specified range, so it can take until the next periodic contract report for our system to be updated (up to 12 mins, formerly 14/22/30 minutes depending on contract rate specified). Second, some message options in certain FMS units are context dependent and without an opening message (UM129 "report maintaining") the contextual response (DM37 "maintaining FL[level]") is not accessible. Third, some FMS units will automatically respond to the opening context message (report maintaining) with the context response message when the correct parameters are met (within 150ft and vertical rate less than 2ft per second).

For CPDLC aircraft within surveillance coverage we'll generally just use VHF comms because it's quicker, easier and some ATCs do not have very much exposure to CPDLC usage. Some exceptions to this are areas of poor VHF (affected by coverage, weather, transmitter faults etc), poor understanding (accents, English as second language, lack of required read-back) or in response to a CPDLC request (A CPDLC opening message should always have a CPDLC closure message to close the dialogue).

I think there's an answer in there somewhere...

Have fun running into the back of that A330 that's seemingly trying to land at the feeder fix. Set course out of the hold? Hope you're happy to start your PRM early. Are you going to aim 30 seconds ahead of your time again particular airline? It worked well yesterday but today, not so much. Do turboprops have clocks?
Oh, 20 mile deviation? Cool, glad you're at the front and no one else is moving. Oh, company policy? Oh speed limited? Glad I was told..
It must be nice living in that world where nothing in aviation changes from the time you start your descent.

Look honestly, we're really just trying to do the best with what we've got. As is everyone, and 99.9% of the time pilots are a pleasure to deal with, even when we stick them with some garbage sequencing. Appreciated.
To be fair to your point though, the system (whole) can be a tad frustrating. Do you think we enjoy asking for an IAS? It's a bit of a shame that our system doesn't give the person responsible for sequencing (literally watching speed and distance) an indicated airspeed.
Do I like having to check that an aircraft is doing 250kts out of the hold? No, I don't. Do I like changing the speed instructions I give every 6 months, not particularly. Do I like my manager changing every 6 months? (Well that one I'm not fussed about).

Anyway, fret not. Onesky will fix everything, haha. ;)

Why did this thread change from a go at the system into ATC bashing?

For one I'm pretty happy with ATC, I doubt I have the overall view of what they're dealing with and yes, sometimes it's frustrating when you look around and wonder wtf was the cause for slow down / speed up when the airports looks empty. My usual thought is they normally know what they're doing, just like we normally know what we're doing. BUT, in general I think pilots usually think they can do everyones job, can't think of too many times I've seen that attitude from ATC.

Current HK based but Ex Sydney approach controller and ex ex NZ based procedural approach.

In NZ it’s only a required call when not identified. As a procedural approach controller it’s useful.
In Aus from what I could tell it’s required by AIP at all times. Another stupid Aussie rule - used to bug the **** out of me working Sydney when busy and some Saab pipes up with “leaving fl150” . Of course the pilot is obviously just following the rules so not his/her fault but in a practical sense it’s totally unnecessary in a radar environment. Shame logic and the Aussie atc system don’t seem to get along.

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Shame logic and the Aussie atc system don’t seem to get along.

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World's second best ATC

Geez, we haven’t heard that one... for a least 10 minutes! :}

Leaving call only in Aus and Singaz.