View Full Version : Why is the TA set at 18000 ft in the USA?

20th Feb 2010, 22:06
Hi guys,

I often play with a Captain a quiz game with aeronautical questions. He ask me something and I have to find an answer, there is no time limit for that and we may use all the means available to get it (my Iphone was really useful during a transit :} ); and vice versa. Now, it's my turn to answer him, and the heading of this thread is the question:

Why is the TA set at 18000 ft in the USA?

(the only tip he gave me is that it's a technical reason)

Thank you mates

PS: I've never flown in the USA, he was an instructor in a flying club there..

20th Feb 2010, 22:29
I believe it's due to the height of the mountains in the country.
For example, Holland is about as flat as an ironing board and the transition level is down around FL050 from memory.
In Papua new Guinea is about FL200 I think due to the large mountains. In Australia it's FL110 because we only have medium-sized rocks here.

20th Feb 2010, 22:33
Unlike Europe the US have things sorted and realised 18,000 feet will stop altitude busts haha.

20th Feb 2010, 22:33
I've already tried that way, but he says it's not the right one (or the one he is thinking to be right :} )

We have in Italy TA as low as 4000 ft ;)

20th Feb 2010, 22:48
guarda qua chi ne parla...

Novita' interessante (http://www.pprune.org/italian-forum/384129-novita-interessante.html)

20th Feb 2010, 23:30
Ok but, in this case, it's not just a "USA related" question.

That link shows different advantages of using a fixed TA in all over the world.

Maybe the Captain's question was not intended to be a USA only condition.

20th Feb 2010, 23:32
Its to avoid the question, "Whats that mountain goat doing up here in the clouds?" followed by a sudden stop.

21st Feb 2010, 01:19
Instesting article about a common TA in Europe


21st Feb 2010, 03:33
JetMcQuack, it's not transition altitude, it is transition level because in the
U.S. it is FL180. The TA is 17.000 ft.
I guess it is because the americans are very practical and would rather change the atlimeter setting always at the same place and when you are less busy than down low and close to the ground.

21st Feb 2010, 04:11
Because when you are below FL180, you'll always be on a local QNH, thus ensuring no altimeter error with regard to terrain, MSA etc. (Not including temp correction). :ok:

21st Feb 2010, 04:13
it's not transition altitude, it is transition level because in the
U.S. it is FL180. The TA is 17.000 ft

On all the USA Jepp charts I've ever seen it states that

Trans level: FL180 Trans alt: 18000'

with a proviso in the WWText that at certain low values of QNH some FLs won't be available as they will be below the transition altitude.

The USA and Canada adopted the 18000/FL180 transition as it is generally higher than most of the mountainous areas of each country. The notable exceptions being Mt McKinley in Alaska and Mt Logan in the Yukon.


21st Feb 2010, 04:48

21st Feb 2010, 05:20
It used to be FL240 in the western half of the US. I believe it was lowered to join the eastern level of FL180 after the Grand Canyon midair in 1956.

21st Feb 2010, 22:12
Try the US AIP, or their equivalent.

From memory, they wanted a TA that would work right across the country and 18,000 was lowest altitude that would work. I could be very wrong though...

Some explanations in the AIP, ENR 1.7; http://www.faa.gov/air_traffic/publications/atpubs/AIP/aip.pdf

22nd Feb 2010, 09:46

See also:
Comment: Europe should have a common, higher transition altitude (http://www.flightglobal.com/articles/2009/08/11/330716/comment-europe-should-have-a-common-higher-transition.html)

The CAA might get it one day :ugh:

22nd Feb 2010, 09:56
If they can sort out the issues of which QNHs to use where, and how pilots obtain them, I see no reason why we shouldn't raise it up to 10,000' or higher in Europe.

Doesn't seem to be a mad rush though. The discussions have been kicking around for over 15 years in the UK CAA alone.

22nd Feb 2010, 11:04
While we're on the subject, what's the lowest TA/TL? - 3000' for Jersey (EGJJ) as far as I can find.


22nd Feb 2010, 11:22
Hi fc101,

How about Johannesburg FAJS?

Elevation: 5558ft; Transition Altitude = 8000ft (2,442 feet aal) !!!

22nd Feb 2010, 13:16
The Netherlands;

IFR 3000 ft.
VFR 3500 ft.

22nd Feb 2010, 16:34
Those with long memories will recall that the USA at one time had three levels of airways, low...to 14,000 feet, intermediate 14,000 to 24,000 feet, and jet airways, FL240 and above.
When the change was made for jet airways to be lowered to 18,000 feet, and at the same time (or slightly later) the positive control area (class A airspace) was to be lowered to FL180, both east and west transistion levels were set at...18,000 ft/FL180.

22nd Feb 2010, 16:55
The FAA and CAA/JAA are 2 completely different organizations. The question could be why does Europe have variable and low TA's? On QNH you have an accurate terrain clearance, while on flight level, "pressure low look out below" isn't an issue when in the USA but could be if flying in Europe because you'll still be FL70 when MSA is 5500ft with a QNH of 970mb, or when climbing to level off at FL50 when QNH is 973mb. By the time you set standard (1013), you may bust that level! I think there is some merit with higher Transition Levels. It seems consistentr and safe.