hello allcould anyone plse explain what are transition altitude and transition leveli am not sure i understand bothtnx a loteric

TRANS ALT = When climbing, the ALT at which you change the altimeter to standard (29.92 HG or 1013 MB)TRANS LVL = When descending, the flight level at which you set the altimeter to the local or aerodrome QNH

I'll give this a shot - though I stand to be corrected.I believe the Transtion Altitude is the height of the tallest geographical feature in the country being flown.For example, in New Zealand the Transition height is 14000 feet, the theory being if you're above that height then you're not going to fly into a mountain or a sheep-herder or similar.In case I'm not wrong so far, using the above example, Transition Altitude is below 14000, Transition Level is above 14000.Dont know what it's called if you're at 14000....Now we wait for the experts to come and answer correctly!CheersTimNZWN

Hi Tim,In the US, "transition level" is that altitude where you progress into Class Alpha airspace. This (in the US) is where you must set a standard altimeter setting (29.92"), and must also be IFR rated and in an IFR-capable aircraft to fly- and also current to legally be able to accept an IFR clearance.I'm not sure what TL means so much in other countries- as it's often much lower than FL 180 I don't know if that also means that Class A is above. I don't think it has much to do with obtsruction clearance- that is usually MEA (minimum enroute altitude), and some of it's variants such as MOCA, etc.Bruce (born and raised in New Zealand, but wandered far away :) ).

Hi Bruce,Yup, my comments were a stab in the dark, your answer sounds much more knowledgeable!CheersTim

Eric, as you probably are beginning to see now this subject is a dark and mysterious one. There are a few things that you need to understand in order to see the logic of TA/TL.First of all is the air pressure. There are a couple of phrases in use around the world that most likely is better described with pictures somewhere else, but here goes. Oh, you

Hi Eric,We spent a long time working with this when testing it's implementation in the latest version of Radar Contact. With much patient explanation from one of our team (Pete Pitman, a very experienced UK controller) I finally began to get my head round it.Here are some of my conclusions.1. Controllers need to maintain vertical as well as horizontal separation between aircraft (usually at least 1000 feet in Europe I believe). The TA/TL is important since it allows them to do this around the altitude/Flight Level where the pilot resets the altimeter from local (QNH) to standard pressure as explained in one or two of the previous posts.2. The actual definitions of what the terms mean seems to vary a bit from region to region.3. Transition altitude is fixed for a particular airport and can be found on the plates for that airport.4. Transition Level is calculated according to the local pressure. That minimum vertical separation I mentioned in 1? The TL is calculated so it is at least that far above the TA. ATC will change the TL as the pressure changes.5. As far as the pilot is concerned, if atc clears you to an altitude (such as 7000 feet) the altimeter will need to be set to local pressure (QNH).If atc clears you to a Flight Level (such as Flight Level 70) the altimeter should be set to the standard value of 1013.2 HPa (mb), 29.92 inches.6. It is a deep and mysterious subject which was a real pain to test thoroughly in Radar Contact. But having it implemented differently for FAA and non FAA regions adds so much to flying outside the US that it was worth the pain :) Hope that helps,All the best,John

In the UK the Transition Altitude is generally 3000ft amsl) but is be higher in some controlled areas, eg 6000ft in the London TMA.As others have explained, aircraft fly on QNH below the Transition level and on a standard altimeter setting above it. There could be a potential conflict between aircraft flying on QNH just below the Transition Level with aircraft flying on the standard setting just above the Transition Level. To avoid this there is a Transition Layer of 500 ft above the Transition Altitude to which no flights are assigned. In the UK the lowest flight level would be FL35 with a QNH of 1013mb or greater. With a QNH of 1004mb the lowest flight level would be FL40.The UK AIP (ENR 1-7) includes a table to convert altitudes to flight levels. This shows that FL35 is only 1900ft amsl at a very low pressure of 950mb!

tnx to all... thanks to all for these explanations i had an idea what it was about, but now its pretty cleareric

>One of these parameters is the air pressure at sea level. This>is 1013,25 mBar in Europe (I always forget what the>measurement is) or 29.95 inches of Mercury in the US. This is>for the standard atmosphere.Just a minor correction, I think it's not 29.95'', but 29.92'' :)Marco

Just wanted to see if anyone was still awake :-bigangel

<>I know that it is different in other countries, but in the U.S. the "Flight Levels" begin at 18,000 feet...FL 180...so there is no such thing as FL 70 in the U.S.Re TA and TL here's the deal. It is confusing only if you fly in different countries where the rules change.On SID-charts, the Transition Altitude [TA] usually is indicated. Normally, this is a fixedaltitude per country. Throughout The Netherlands it is 3000 feet1), throughout Germany 5000

Hi there,Yep, in testing radar contact I always had to fly outside the USA to get a FL of 70. Glad we got that right :-)Coming from Britain I'm glad we still have a few more idiosincracies than the rest of the world :-lolMind you Austria has some variable values as well. Just looked up some old plates. Vienna TA 5000', Innsbruck 11000'. If you've ever flow into Innsbruck (and if you haven't you should!) you'll know why ;-)All the best,John