Hi Michael,"It may be so that these calculations are not implemented at all in the sim or that country specific transition levels are not recognized."You may well be right and a short post to that effect - or explaining whatever the actual case may be - from PMDG is all I ask.BestPete

As my fellow countryman Jan Roar has shown in his post, there is something called the Transition Layer. This is always at least 1000 feet, so that needs to be taken into account as well when determining the transition level.In my old job as an AFISO we used tables, using the QNH as basis, and then read the corresponding T/L off that. For instance, QNH from 978 to 995 would give a T/L of 90 when Transition altitude is 7000 feet. 996 to 1013 would give 85, 1014 - 1031 = 80 and so on.As previously stated by others, Transition Altitude is a fixed value for each airport, or a group of airports if they are in close viciniyt, and this is the altitude where you change from QNH to 1013 when climbing. If there are two or more airports in close vicinity they would use a common T/L as well, using the lowest QNH as a basis.Oh, and I never had to pick myself off the floor when asked for the T/L, even though it is there plain as your nose on the ATIS :D Dunno about U.K centres, but ours do have information systems displaying this in each sector. APPs have a printout of the ATIS right next to the progress strips.Just my 2 cents.Cheers,Kjell.

Departures use Transition Altitude ... at or below (local pressure).Arrivals use Transition Level ... at or above (standard pressure).The reason it is "at or above" or "at or below" is to give the separation between the two.The TL will always be greater then the TA because the first useable flight level will always be above the TA.There is absolutely no math required because the guys on the ground set the TL, you just key it in.The TA is generally a fixed number.The relationship between the TA and the TL is also fixed, it must always have enough altitude between the two to allow for the change over difference when resetting the baro.(thats my understanding of the world)Ray

Wow!!! They say you learn something new every day, I must be living the lives of ten people with the amount I've learned today!Thanks Pete and everybody else in this discussion. I knew there was a minimum stack level but had no idea how it was determined. I often wondered why some days on the BNN2a arrival into heathrow I was being given "level at FL80 by Bovingdon" and other days it would be "level at FL70 by Bovingdon". Now I know!!So thanks guys, even though this wasn't the original point of the post and apologies for thread hijacking. We need more, informative discussions such as this one.

Hi,>So thanks guys, even though this wasn't the original point of>the post and apologies for thread hijacking. We need more,>informative discussions such as this one. I fully agree with you this is good food for the neurones and it adds tremendous value to this forum.Let's hope the PMDG developers will comment soon on the original question from Pete.DISCLAIMER:The above reflects only a personal opinion and was written without any intend to offend, harm or criticize in any way or manner any individual, institution, association or company including PMDG.Michael

"Let's hope the PMDG developers will comment soon on the original question from Pete." I hope so too, Michael, but I'm beginning to doubt that they ever will. A pity really because PMDG has such a well-deserved reputation for user support through this form. Still, you can't win 'em all and it's hardly of earth-shattering importance. Pete

You're welcome, Ross - I enjoyed it too. Well, most of it because, as usual, one or two posters completely missed the point (or didn't read the thread properly) and seemed to think I was asking for an explanation of TA and TL! x( All I really wanted was an explanation from PMDG of the input value required at L1 on the Descent Predictions page but that doesn't seem to be forthcoming for some reason.Anyway, thanks for "hijacking" the thread - it made the waiting for PMDG's reponse most enjoyable.Pete

Don't know if you noticed it but I posted a new thread yesterday http://forums.avsim.net/dcboard.php?az=sho...id=43385&page=2 which has been viewed 203 times since then but apparantly not by the PMDG team. Maybe they are too busy testing the 800/900 or are they gone on a retreat before Easter?Agrred the issue may not be of the greatest importance but it would be interesting to know their point of view.DISCLAIMER:The above reflects only a personal opinion and was written without any intend to offend, harm or criticize in any way or manner any individual, institution, association or company including PMDG.Michael

No, I hadn't noticed it, Michael, but thanks for doing that - maybe it'll bring a result.Pete