wrote in message
k.net...
Here in the US, the barometer setting used is either the local setting
when below 18,000'
MSL or 29.92 when at or above 18,000' MSL. This is according to FAR 91.81.

My question is on understanding how this works in Europe (and other
airspaces
besides the US). My current hazy knowledge is that the 18000 feet may be
different
either by country or some other boundary. Could someone familiar with this
crossover
in Europe or elsewhere advise me on how it works?

That's just about it. Different states set different thresholds (called the
"transition altitude") that are similar in effect to the 18,000 ft. At and
below that altitude a "local setting" is used and the vertical coordinate is
referred to as "altitude". Above that level 1013.25 hPa (= 29.92 inHg) is
used and the vertical coordinate is referred to as "flight level".

In some cases, different areas within states have different transition
altitudes for ATC purposes. For example in the UK, the general transition
altitude is 3000 ft, but within the horizontal extent of the London TMA it
becomes 6000 ft.

Julian Scarfe