What are Transition Levels?

These are the levels based on varying altitudes. As the aircraft climbs or descends They are due to the required settings on the aircraft altimeter. when and aircraft is ascending thru 4,100 ft., the Q.N.H. must be changed on the altimeter from the local setting into the standard international setting f 29.92 INS Hg or 1013.25 millibars. In Trinidad and Tobago this altitude of 4,100 feet is known as the transition altitude. Aircraft descending thru 5,500 feet which is also known as FL55 within Trinidad and Tobago must change their altimeter setting from the international std. of 29.92 to the current local Q.N.H. setting. This FL55 is known as the transition level. It then stands to reason between 4,100 feet and 5,500 feet. There is a layer of airspace; this layer is known as the transition layer.