Much has been written about this, but still I get a lot of questions from trainee ATCs.
This topic is about: what transition altitude does the ATC assign to an aircraft.
Mark has written a tutorial for pilots, on when, and when not to request a Transition.
What we see in Mark’s post, is that you only request a transition, when you are passing through an airport’s airspace. Above 5000 AAL (Above Aerodome Level), don’t contact Tower!
For ATC’s to know what altitude to assign to an aircraft which is transitioning through your airspace, you need the following:
- aerodome level of your airport
- pattern levels of propellor aircrafts - in IF these are set to: 1000 feet Above Aerodrome Level (AAL)
- pattern levels of airliners - in IF set to 1500 feet AAL
So this leaves room for aircrafts to transition through airspace.
The picture below assumes that the Aerodrome Level is 1000 feet ASL.
Remember: altitude assigned by an ATC is always ASL.
So for airports at sea level, transition altitide assigned to an aircraft can be between 1500 - 5000 feet.
For an airport, somewhere on the high grounds at 4500 feet, transition altitude assigned should be 6000 - 9500 feet.
Now…many pilots on IF fly their patterns a lot higher than 1000 or 1500 feet AAL.
If you as ATC have a few of these high-flyers doing patterns, I suggest you pick the top part of the transition space, to allow an aircraft to transition safely.
Note: For us in IF, it is safe to assume that AAL is the same as AGL