Originally Posted by
anotherthing
The TL is used primarily to ensure a minimum separation requirement exists between the TA and the Minimum (Useable) Flight Level.
I don't think you are quite correct here,
anotherthing.
ENR 1.7 says, in this connection, at 3.3 (my bold):
3 General Procedures
3.3 The vertical position of aircraft at, or below, any Transition Altitude will normally be expressed in terms of Altitude. The vertical position at, or above, any Transition Level will normally be expressed in terms of Flight Level. When descending through the Transition Layer the vertical position will be expressed in terms of Altitude, and when climbing in terms of Flight Level. It should not be assumed that separation exists between the Transition Altitude and the Transition Level.
JD
