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FSX AI Not Communicating With ATC After Takeoff

I just converted another a/c to FSX and AI. I plugged it into my standard simple AI test flight plan (takeoff, do a circuit and return), which if flies beautifully and correctly. However, although the pilot requests (and receives) taxi clearance from Ground and takeoff clearance from Tower, that's the last communication there is with ATC. If I plug in any of my other AI a/c to the same flight plan, after takeoff they get handoff from ATC, request and receive pattern entry and landing clearance, and then after landing are handed over to Ground where they request taxi instructions.

Any idea what could be causing this ?

Thanks !


Resource contributor
Assuming you mean by same flightplan, it is also the same airport? If not, does it have a tower? and an ATC Frequency assigned?


Resource contributor
The problem likely lies with the aircraft conversion. There's nothing in the traffic file that would cause it.

Incidentally, if you are using FSX, FS9 aircraft don't need conversion.
Thanks guys. Don - yes I know I don't need to convert to FSX to fly FS9 AI in FSX. I did the conversion for another reason and then decided to do an AI version using the FSX model.

Anyhow, it looks like I misdiagnosed the problem. It's not just one a/c that has the problem. I've tried 2 or 3 of my regular AI a/c which have behaved correctly previously and they now present the same problem, so clearly something has changed. My log tells me I updated the airport recently, though I didn't (deliberately) change anything about the frequencies.

I need to take some more time to get a better handle on this. I may be back :)


Resource contributor
Check that there is a valid taxipath from the aircraft to the active runway having a hold-short within the requisite distance from the runway
Thanks guys - good thoughts.

Today I ran some more controlled tests, using the simple test flight plan, three of my AI a/c (not including the newest one) and two of my airfields, including the one where I first identified the problem. The results were interesting.

All three a/c taxied, took off, flew the pattern, landed and taxied back to the parking spot at both airfields as expected.

One a/c communicated with ATC correctly throughout all phases of flight in the air and on the ground at both airfields.

The other two a/c exhibited the problem described above at both airfields i.e. they requested/received taxi clearance from Ground, requested/received takeoff clearance from Tower and took off. Thereafter all ATC communication ceased.

So although there may be an airport factor, this would seem to be an aircraft problem. So I started comparing the 'good' a/c and one of the failing a/c, which are fortunately quite similar. Following Guenther's tip above, I checked the Radios section in the aircraft.cfg files, and they were different, so I replaced that section in the failing a/c cfg file with the same section from the 'good' a/c. This did not fix the problem.

So I got a bit more heavy handed. Since the two a/c are similar, I was able to swap the .air files and the aircraft.cfg files. And I found that if I swapped BOTH, then the problem was fixed. However, if I swapped only the .air file or only the .cfg file, the problem was still there.

So I'm guessing there's something in the failing a/c .cfg file that is overriding something else in the .air file and somehow causing this problem. Now to go through the two .cfg files to see what I can spot.
Can we assume that the airports at which you have ATC problems only have one contact frequency, e.g. Tower, and not different frequencies for Tower, Ground and Approach? I know that some aircraft seem to 'behave' properly at your airports but I would check this out first (if you haven't already done so).
All my airfields have three frequencies - ATIS, Ground and Tower. I can easily change one of them to single frequency and see if that makes a difference. But don't forget the failing a/c have already switched from Ground to Tower and received Take Off clearance. What should happen next is Tower should hand off the a/c as leaving its airspace, but that never happens.

Out of interest - does anyone know what the trigger is for Tower to give the "Leaving Airspace" handoff ? I'm speculating that the a/c that is working OK is somehow behaving differently to the ones that are failing. This could explain why when I swap the CFG and AIR files with a failing a/c, everything works.

Yep - I'm flailing right now :)
I've spent a couple days on this, and I've found the answer (for me). It wasn't what I expected.

It turns out that the magic parameter is electric_always_available =1 in the [electrical] section of the aircraft.cfg file.

With this parameter set to 0, all my AI a/c (about a dozen of them) have a very unreliable relationship with ATC. They nearly always request and receive taxi clearance. Sometimes they request/receive take-off clearance. But after that, they usually never communicate with ATC again, even though they fly their flightplan correctly. Better still, if they fly exactly the same flight plan again, they may lose ATC comms at a different point. I think this is what confused me earlier, when I thought things had previously worked.

But the same AI, on the same flightplan, but with electric_always_available =1 always (always) communicate correctly with ATC at all stages of the flight.

I have no idea why this works, but it does. I suspect there are other settings in the CFG/AIR files that achieve the same result, but I haven't found them.
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I should say so far I have only noticed this problem on the very simple take off, fly a circuit, and land at the same airport flight plan. Regular point to point flights seem (seem) to behave normally even without the above parameter set.

Happy for this thread to be moved into the general AI section as it's not an AIFP issue. I think I only posted it here because I was answering another post at the time !