Valid for fixed leg flyby transitions. I.e. normal turns with no overfly:
Terminal Area (below FL200):
- Philosophy is a short turn sticking to the path
- Turn-anticipation not more than 10NM
- Roll-angle (phi) is equivalent to the Course Change required
- Minimum 10 deg bank
- Max 25 for pre-computation, Max 30 once in the turn.
Enroute (FL200 and above):
- Philosophy is pax comfort
- Turn-anticipation not more than 20NM
- Roll-angle (phi) is the one required for a turn tangent to the 5NM nominal airway limit.
- Minimum 5 deg bank
- Max 25 for pre-computation, Max 30 once in the turn.
The enroute vs terminal logic is based on the predicted altitude at the turn bi-sector: i.e. predicted altitude at the waypoint. That's why you could see a very shallow bank angle at much lower altitude when the predicted altitude at the to-waypoint is above FL200. Normally this would be more noticeable with larger course changes, i.e. more acute angles. This is undesirable when still in the Terminal area.
When operating in this condition, you could avoid this phenomenon by inserting a Place-Distance waypoint before the TO-waypoint. e.g. 'ZZZ/-5'.
The FMGS does not start turn-anticipation construction till the previous waypoint is sequenced. i.e. can only think 1 waypoint ahead.
Hope this helps.