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Transition Altitude and Transition Level

OpenRadar is a standalone radar screen which connects to the FlightGear multiplayer servers. It is currently being developed.

Re: Transition Altitude and Transition Level

Postby Johan G » Tue Feb 24, 2015 2:27 pm

Interesting and educational topic. Thanks guys. :D
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Re: Transition Altitude and Transition Level

Postby Omega » Tue Feb 24, 2015 9:14 pm

  • There is only one type of TL and that is the one published on the ATIS and by ATC
  • TL is not determined using a global table, it depends on the facility
  • A good TL ensures minimum separation from the TA

The TA/TL indication on the top right of OR has only one purpose: it serves as a reminder to the controller and this is what the OP was referring to.
If the indicated TL results to an unsafe transition layer, this could risk loss of separation.

Bottom line is, the system can calculate the altitude using any type of algorithm in the background.
On the controller's end, either display a reminder of a manually entered TL or don't have a reminder at all.

That's my opinion.
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Re: Transition Altitude and Transition Level

Postby wagnerw » Wed Feb 25, 2015 9:26 pm

I wonder about us.
We are discussing this topic, as if it is the most important feature in our simulation world.

It was good to bring up all the details about it, as many will learn about it. Very often, when I told somebody to raise to 4000 ft, I got the confirmation for FL040. These details may be known to all professional pilots and semiprofessional sim flyers, but in our world, it is more important to help pilots on their way to the runway separated far enough from each other.

I think, everybody knows now, that only TA is fix for the airport and FL depends very much on many things. Some countries have a defined distance between them, less a fix TL no matter what, and most of them calculate the FL.
How do you want you this matter implemented in OR?

The current implementation calculates the next FL (really) above TA. As rule of thumb, do not assign the TA nor the TL to your contacts, and separation will be no issue. If the TL is fix for your country, you may ignore the calculated value. This would be pragmatically.

Otherwise, I would have to ask you for your desired minimum separation between the real altitudes of TA and TL, alternatively for a fix TL definition of the current airpressure at start, and for the third case additional a checkbox "fix value". Do you want to be warned if airpressure changes and TL needs to be corrected, after a thunderstorm crossed your airport?

Personally, this seems to be a bit too much detail for a small side issue.
We have a solution that follows the official definitions, by calculating the TL as next available flightlevel above TA. The issue is, that this TL is a little bit higher in some countries and in less countries even fixed to one value.
It is more important, that we all start to assign altitudes below TA in feet and all above in FL.
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Re: Transition Altitude and Transition Level

Postby Turbo » Mon Mar 02, 2015 5:54 pm

Hello

When I try to ATC, I try and be as realistic as possible. When OR gives me inaccurate information like the TL/TA it frustrates me. The information is there to remind me of the trasisson zone and not to place pilots in that zone, what the point of having the information if its false? What I propose you do is make a checkbox if you want the TL to be caudated by formula or not and add value boxes like the ones you have for the squawk boxes.

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Re: Transition Altitude and Transition Level

Postby wagnerw » Mon Mar 02, 2015 8:56 pm

So be it... this is no major change...

I know of three cases:
(1) Main case: TA fixed per Airport, TL = Next flightlevel above TA => implemented
(2) As (1) additional fix minimum distance between TA and TL (= minimum transtion layer) (e.g. Germany 1000ft)
(3) Less places with a fixed TL (I know only of TNCA Aruba, Lesser Antilles, Caribbean) TA=3000ft, TL= FL045

Q1: (2) I have read single documents saying the 1000ft transition layer is valid for the US and Germany. Case (1) takes the next available Flightlevel. I implemented a minimum distance of 500ft. This might be incorrect, as the examples for Germany and USA show 1000ft. The tables that I have checked show my current implementation to be correct.
Q2: Are there more cases you know of and which you really need?

And once this this implemented: I will check how often TNCA will have an ATC! :)
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Re: Transition Altitude and Transition Level

Postby wagnerw » Sat Mar 14, 2015 8:35 am

This feature is available in todays update.

You can choose how you want to define transition.

As we explained, for 99% of all airports and all users who don't want to care about that topic, you should use the Calculation Mode:

You define the Transition Altitude (real altitude basing on current airport pressure, take the real value out of your charts an altitude higher than the highest terrain around) and the width / thickness of the transition layer above.
OR will use the next Flighlevel above TA+Transition Layer Width as Transition Layer and update this value every time the air pressure changes.

For the protocol: As the transition layer is defined in relation to standard pressure, it might appear to be lower than expected (in high pressure regions). This does not mean that the real altitude is lower, it means that the flightlevel number is lower. When you switch at TL from standard pressure to ATIS defined airport pressure, your displayed altitude will be larger than TA + Transition layer width.

Fix TL Mode: For the single known airport that uses it, or if you prefer to do the math on your own, you can define a fix Transition Level (TL). This will not change with the airpressure. You are responsible to care about separation. This is especially important in low pressure situations, as the TL will be much lower than the number tells.

Most important for me is, that we tell assignments below transition layer in feet and above it in flight levels.

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