Transition Altitude

28.10.2004

Submission:

How is the Transition Altitude value chosen? This altitude is part of the approach chart. if an aircraft is at or above it then Z coordinate is expressed by Flight Levels FL (QNH Ref.). If it is below, Z is expressed by Height above the A/D elevation (QFE). I used to take the maximum of the Minimum Sectors Altitudes (MSA) but I m not sure if it is the standard practice.


Said Chibane Canada

Answer or Commentary:

(I.W.

I don't think there are hard and fast rules on determination of the transition altitude. However altitudes below the transition altitude should encompass aircraft in the approach and departure phases of flight. As far as I understand it flight levels are an altitude above an average pressure value (1013.25) corresponding to mean sea level. While altitudes below the transitional altitude are still altitudes above a pressure value corresponding to mean sea level but corrected by the given QNH to local variations of temperature etc..)