Transition Level

[Speedbird252]

Evening PPRuNe`rs.

Am I correct in believing that the transition level in the USA is FL180? If so why is it at such a high altitude?

What is it that determines this level in the UK? Im sure that it changes but I have no clue as to why?!!?! (Met conditions ?)

Thanks and regards.

[HEATHROW DIRECTOR]

I don't think anyone - least of all working controllers - know why the UK has such strange rules relating to transition altitudes!

[fireflybob]

It's not the transition level that is 180 in the USA but the transition altitude that is 18,000 ft - an important distinction to make.

The transition level will vary depending on the pressure (QNH) of the day.

The transition altitude is the altitude in the vicinity of an aerodrome at or below which the vertical position of an a/c will be expressed in terms of an altitude based on QNH.

The transition level is the level at or above which the vertical level of the a/c will be expressed in terms of a flight level (based on 29.92 ins Hg or 1013.25 mb).

Many years ago the TA at LHR was 3,000 ft. There was near miss between, I recall, an aircraft on departure and an aircraft holding at Epsom. The outbound a/c had not set 1013 which caused a level bust. In the aftermath of this incident the TA was revised upwards (to 6,000 ft ?) as it was deemed that the low TA was not appropriate to high performance a/c where workloads were higher after take off.

Unfortunately the situation in the UK (and much of Europe) seems to be a mish mash and it's a pity they cannot all standardise on a common transition altitude!

[Oliver James]

There is a little more to this...

Correct, the transition level is the first available level which, on a given day, is physically above the transition altitude, and that will depend on the pressure. The Minimum Stack level is the lowest level above the T/A which gives 1000' separtion from it.

The reason why the London area has a different transition altitude to the rest of the country is (was) the need for procedural separation of traffic within the London TMA, as the amount of traffic from the various airports increased.

Take Brookmans park as an example: With each of the then 4 airports routing traffic through BPK, a 3000' T/A was no good because this left no room underneath for anybody else in what was still a significantly 'procedural' environment. By using 6000', Stansted's can go through at 3000', Luton's 4000', Gatwick's 5000' and Heathrow's 6000'. Thus, they were all procedurally separated and on the same setting which made it easier to release traffic off the various airports. Of course these days everything has changed and we are now reliant on radar separation to the very largest degree but even now this is still the basis for the separation of SIDS.

Point 4 <img src="smile.gif" border="0">

[ 16 February 2002: Message edited by: 120.4 ]</p>

[Warped Factor]

I understand that a common TA for the whole of the UK is on the agenda.

Shame that it probably won't be higher than 6,000ft though.

WF.

[Squawk7777]

Speaking of the US, does anybody know what the transition altitude in Hawaii and Alaska is?

[Speedbird252]

Thanks to you all for the replies, it doesnt half make a difference if you ask people who know what they are talking about!

Regards.

[OzExpat]

In PNG, Transition Altitude is 20,000FT, with Transition Level at FL210 plus or minus the usual caveats that never seem to occur in this part of the world. The highest LSALT, MOCA or whatever you want to call it, is 16,800 feet, so TA and TL are always well above all terrain.

[englishal]

Why not have a Europe-wide transition altitude, which gives suitable clearance over the highest terrain in Europe....makes sense, rather than mess around with different levels in differnt places. BTW its 4000' at EGHH....