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A few issues with ATC Robot

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Member
Registered: Sep 2014
Posts: 165
Location: Near Paris
Hi Hardy,
I have a few issues with the ATC robot, especially TOD detection, and arrival runway selection.
I frequently make short haul flights, because I don't have time for much more, so with a rather short cruise phase. The last examples I have in mind are from LFPG to LFMN or LFBD.

Today, I just made a flight LFPG LFBD and made a few trials.
Runway in use at LFPG was 26R according to ATIS. I selected 27L for departure in the FMC before contacting ATC, and was assigned 27L, so it was working nice.
In all the flights I make, everything goes as expected until TOD.
In my last example, runway in use at LFBD was 29. I set up my FMC for an RNAV 23 just to see what happens.
First problem (and I have this in almost every flight I make, and I only make short haul, so there might be a relation), just before reaching the FMC TOD, I am correctly handed over to approach control. I contact approach, which gives me a new squawk, which I input correcly. Then nothing. I waited until I was 10000ft high then desended wihtout clearance. During descent, approach announced RADAR CONTACT and resumed clearances, which seemed consistent.
I have this issue on almost every flight. I have the feeling that center is handing me over quite close to TOD, and I mostly fly over the TOD while contacting appraoch. I don't know if that could explain it.
Then, I went on with my approach, and I was eventually cleared for runway 29 approach although I had selected runway 23. I remember having read somewhere that ATC robot should have assigned me the FMC entered runway, but I am not 100% sure.
One last item, this one is a very short request: would it be posible to include ATIS letter in the D-ATIS ? Clearly not very important, just to make it clear that it is an ATIS and not a METAR (by the way, thanks again for including transition level !).

No hurry with any of those items of course !

Take care and enjoy your well deserved break.

Charles
Member
Registered: Sep 2014
Posts: 165
Location: Near Paris
And I forgot to mention I flew with all LNAV boxes ticked.
Moderator
Registered: May 2009
Posts: 5140
Hi Charles,

when Approach has given you a new squawk and you confirmed it, Approach will (usually about half a minute later) give you a descent clearance to the next altitude constraint or to a random altitude.

Does that not work for you?

Also, it should use the FMC runway ineed. I don't know what's wrong in your setup. Do you have a situ?


Cheers,

|-|ardy
Member
Registered: Sep 2014
Posts: 165
Location: Near Paris
Thanks for answering so fast as usual !
I don't know how long it took before I received the first clearance, but even after I initiated descent on my own the first clearance came several minutes later (2-3 I'd say).
And clearly for arrival runway there was something wrong. I changed it from rwy 29 to rwy 23 during cruise but before center handed me over to approach (perhaps I should have done it earlier ?). I don't have a situ file at the moment but I will try to get one ASAP (don't know when, perhaps tonight, probably later, I don't know if I'll have enough time).
Just to be sure what do you need exactly ? A situ recorded just before center transfers me to approach ?
Moderator
Registered: May 2009
Posts: 5140
A situ before TOD to try reproducing the missing descent clearance.

As for the wrong runway: I guess you changed it to late. Once ATC has started its vector plan for the given runway, you can't change the given runway anymore.
Member
Registered: Sep 2014
Posts: 165
Location: Near Paris
Good evening Hardy !

I did a bit of homework on my ATC issues. I'll start with the easy part (the approach runway selection), then talk about the TOD issue.

For this discussion, I'm using the same LFPG LFBD flight I mentioned in the post above (except that PFPX gave me a cruise FL of 410 the first time, which resulted in a very hort cruise. In the discussion below, I used FL390 for cruise, which gave me around 100Nm of cruise phase). I attached a link to the situ file at the end of the post. In this file you start just after the top of climb, and you have to contact center (frequency is already tuned), in order for things to be stable. ( I tried with later saves but did not get the same results all the time).

1)Approach runway selection: I think you were basically right, I probably entered it too late the first time (although I'm pretty sure I did it before contacting approach).
During this flight I preselected RNAV23 before departure, and made sure it was not runway in use on arrival and I was properly cleared for approach 23.
But my issue the first time was not really being expected on a wrong runway, the biggest problem was I was not aware of it as I ticked LNAV.
I don't know if this would be doable, but it would be nice if approach could on first contact mention the runway. Something like:

"BAW315 radar contact, descend FL230, expect runway 23", or even without the "expect". The first time the problem I had is that I had everything set up for runway 23, and just reaching 3000ft, "cleared aproach runway 29"! Whereas if I had known it before, I could have just said, "bloody controller !" and set up for an ILS29 (I'm flying a speedbird so I'm allowed to say bloody, Peter's fault...).
I tried to keep this suggestion simple enough, but I have no idea if this would be doable of course, so just suggesting.

2)Now the TOD issue. This one is actually tricky to replicate.
I don't get it every time to the same extent, but there seem to be a problem. Let me try to explain.
I have the feeling my problems come from the sequence of events. Every time, I have to go through all the steps of the robot, including a frequency change to an HF frequency, even for a very short cruise. In the example of my situ, with a cruise length of 100Nm, the robot asks for a frequency change to an HF frequency around 40/35 NM to TOD. You have to immediately do it, and then, just afterwards, he asks to change to approach.
In the trials I made I was really paying attention to this because I was trying to diagnose this issue. But when making my full flights, I was sometimes doing a checklist, or something else, and probably, I was just before TOD when contacting approach, and it was "too late "for the robot to catch up because I had overflown the TOD before having the correct squawk. If I recall correctly, cycling the robot on/off could solve the issue, but not 100% certain.
In the last trial I made(so paying real attention and doing the frequency changes as fast as I could), I was able to contact approach just a few miles before TOD (and I was VERY fast to read back). So just a few miles before TOD, I had read back initial message and entered the proper squawk. I started a timer at the TOD and it took 1minute 45 seconds after TOD for approach to give me the first clearance "RADAR CONTACT desend FLxxx" and I was already quite high on the approach.

I don't know if my analysis is correct, but here are just a few suggestions (which of course apply only if I did not miss something).
*Perhaps if the flight is a short one it would be possible to skip the HF part. Some simple analysis like distance from origin to destination in the ATC menu, if this distance is less than xxx NM , then HF frequency won't be used and is greyed out
*In the example above, I was barely able to catch up with the glide path, but I've NEVER been cleared for descent from cruise FL BEFORE the TOD, only after. Sometimes a bit, sometimes a lot. It would be nice if it could be sometimes a bit before, sometimes a bit after.
Anyway, I think it is strange to get the reply from approach more than 1 and a half minute after the squawk is entered correctly, so I must have some sort of problem here.

Anyway, I hope I was clear enough with this long post.

Don't hesitate to ask if ou need more info or wish me to make some more tests.
Thanks if you read until there !

Good night !

Charles







https://www.dropbox.com/s/hvackb6bjmuasq6/LFPG%20LFBD%20Cruise%201.situ?dl=0
Moderator
Registered: May 2009
Posts: 5140
Hi Charles.

tango4 wrote
It would be nice if it could be sometimes a bit before, sometimes a bit after.

Normally, that's what the random generator does. I don't know how many T/D events you tested, but, statistically, in 50 of 100 events the clearance should occur before the T/D. If you made 10 tests, it might have been bad luck and all of them occured after the T/D :-)

This random stuff also affects the other points you mentioned. It's hard to reproduce this stuff, and the tests are very time-consuming because time acceleration cannot be applied to the talking speed.

By the way, to avoid the HF frequency, you can manually enter one and the same VHF frequency (any frequency you like) in both Center station edit fields on the Instructor. Then there will be no frequency change during cruise.


Cheers,

|-|ardy
Member
Registered: Sep 2014
Posts: 165
Location: Near Paris
I didn't know about that tip for the HF frequency. Thanks a lot, I'll definitely give it a try !
Moderator
Registered: May 2009
Posts: 5140
Hi Charles,

I just flew your situ all the way till landing and runway vacation. All went well.

Initially, in cruise, on Center 1, I got "maintain FL390".

Then I got a SELCAL on Center 1, and a handover to HF on Center 2.

Then I got a SELCAL on Center 2, and "maintain FL390".

10 nm before T/D I got a SELCAL on Center 2, a handover to Approach.

5 nm before T/D I got a new squawk from Approach.

9 nm after T/D I got a descent clearance to FL190.

Before reaching FL190, I got a descent clearance to FL160.

Then I recaptured the VNAV idle descent path.

A couple of times during the arrival I heard instructions to other aircraft "cleared for approach runway 23", so I knew I can expect runway 23.

Then I got the descent clearance to 3000, and speed 240 etc., and handover to Tower etc.

All in all, no problems on this test flight :-)


Cheers,

|-|ardy
Member
Registered: Sep 2014
Posts: 165
Location: Near Paris
Good evening and thanks again for your help.
I had not thought of listening to other traffic clearances to know the runway. I forgot that you had only one active runway in PSX, so that tip is actually a nice one in case of doubt.
The tip you gave in the previous post to skip HF frquency is indeed also quite useful.

Nevertheless, after a few other tests, I never saw an approach clearance before the TOD. But the ones I had were a bit late, but clearly doable.
I don't know what happened during my full flights where I had no clearance. I can assure you this happened several times, or else I would not have bothered you with it.

Anyway, i'll be using those two useful tips !

If I encounter the issue again, I'll contact you if I'm able to get something that is reproducible. Thanks again for your time.

Charles
Moderator
Registered: May 2009
Posts: 5140
In the next update I'll try to distribute the random events of the descent clearance more on the pre-T/D side than on the post-T/D side.


|-|ardy
Member
Registered: Sep 2014
Posts: 165
Location: Near Paris
Thanks again !
Just to make it clear, despite all my messages above I really am a fan of your ATC system. It could do with a few request functions but it is nonetheless really neat and easy to use.
A real ATC simulation would be a product of it own. What I like with an ATC simulation is the fact that it provides some disruption to your plans of actions as in real life (Interruption of a checklist, etc). And yours do this perfectly without being a pain to configure and manage ! So all in all excellent design !

Take care and enjoy your well deserved break.
Moderator
Registered: May 2009
Posts: 5140
Understood :-) You're welcome!


Glad you like it :-)

|-|ardy
Moderator
Registered: May 2009
Posts: 5140
There was indeed a special problem that was hard to reproduce and thus hard to find: Sometimes the ATC robot didn't get the initial descent altitude constraint from the FMC LEGS and therefore kept the clearance on the cruise altitude. This is repaired now in PSX 10.0.5-beta10:

http://aerowinx.com/forum/topic.php?id=2939


|-|ardy

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