I have been suffering CTD's for a long while and can't find the cause.However, it does seem fairly definitely to be a problem which bites me when I get within a certain radius of London from any direction. Being UK based, this is a real problem!If I repeatedly fly the same route with all other conditions the same, the CTD will come at almost the same place, precisely.Firstly, things I don't have:1) Add-on scenery in the area2) Add-on airportsI have done a complete re-install (or 3) since I have messed with any of that stuff.What I do have is:1) Lots of AFCADS2) Lots of AI (mostly Aardvark/FSP/Evolve/PAI and MRAI flightplans, but a mixture really).I have tried running without the AFCADS and have selectively removed the flightplans I installed around the CTD's started. I have also selectively removed AI repaints I installed at about the time the CTD's started. However, I have so many of the things that it's impossible to say that this has been totally comprehensive.I'm wondering if in the absence of scenery etc around London, it's something to do with the mass of air traffic I have built up around there.My latest theory is that it's something to do with ATC handling the mass (and I mean mass) of traffic I have buzzing around London.I'm using EditVoicepack and it seems to me that if I update Voicepack (using acceleration and the ICAO standards) I do NOT get a crash the first time after I have updated, but I do on subsequent attempts to fly the same route with the conditions otherwise unchanged.I'm not making any accusations towards EditVoicepack, maybe it's cleaning up a problem FS9 leaves behind.Does anyone know whether FS9 ATC uses some sort of cache or file which could become overloaded? Maybe it doesn't clear out properly at the end of a flight?I am probably clutching at straws but it's one more avenue to rule out.

Hi,<>Have you used ScanAFD to check for duplicate AFCADs? This is known issue that can cause CTDs. Did you get a Windows error message giving details of which DLL might have caused it? ATC.DLL or NTDLL.DLL?Search for ScanAFD in the library and install and run it. Make a note of all the duplicates it finds and report back. It does rather sound as though you have been installing Ai and AFCADs to your heart's content and that may be responsible for the problem.Cheers,

Have done that - doesn't show any problems

Update to the latest FSUIPC 3.70. FSUIPC works around a communications bug in FS where if going in comms from one airport to another that shared a comm frequency it would crash atc.dll, I believe. This might include AI chatter.Ray can explain it better :) .It is possible there is an AFCAD causing this conflict with its frequency assignments.I recall even with default installs errors reported around London. Make sure you have the 9.1 patch installed. I think there might have been a Heathrow fix in it.

Hi again,<>As Ron mentioned I was able to reproduce the atc.dll crash on one of my flights - LIRF-EGLL. I'm prety sure it happened because one of the frequencies at LIRF was the same as one at EGLL. I had the CTD as soon as I contacted TWR I think. Try it yourself with two airports that have the same ATIS frequency. LIRF and EGLL had 118.00 on my install.It would help if you could post details of the error message.