Transition altitude

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Transition altitude is a term used in aviation. It is the highest altitude at which an aircraft in normal operation should use an altimeter pressure setting indicating height above mean sea level (QNH). Above the transition altitude (TA) the aircraft altimeter pressure setting should be adjusted to the standard pressure setting of 1013.2 hectopascals(Milibars) or 29.92 inches of mercury and aircraft altitude will be specified as a flight level.

This is distinct from the Transition Level, the flight level at which, on descending, the pilot starts to refer to altitude of the aircraft by setting the altimeter to the QNH for the region or airfield. Note that the Transition Level is the lowest flight level for the atmospheric conditions, but aircraft do not use the first 500 feet above the current Transition Level. Therefore the lowest usable flight level is the Transition Level plus 500 feet.

Transition levels are dependant upon which country's airspace the aircraft is in, here are the transition levels: -Austria 5000 -Belgium 4500 -Denmark 5000 -France 4000 -Germany 5000 -United Kingdom 6000 -Hungary 7000 -Ireland 5000 -Italy 6000 -Luxembourg 4500 -Netherlands 3000 -Norway 4000 -Spain 6000 -Sweden 5000 -Switzerland 5000 -USA and Canada 18,000

N.B all altitudes herein are in feet

Above these altitudes Air Traffic Control will make reference to higher altitudes as Flight Levels, which is written as the altitude in feet divided by 100, for example, 32,000 feet, in any country would be referred to as FL320.