The waypoint identifiers all come from the navigation database, if they have been charted with a 5 letter or 5 alphanumeric identifier then that is what should be displayed. If they are conventional fixes with no charted identifier then they should be identified according to the ARINC 424 rules, some of which are shown below:
Single Approach
FF = Final Approach Fix
AF = Initial Approach Fix
IF = Intermediate Approach Fix
CF = Final Approach Course Fix
MA = Missed Approach Point Fix
SD = Stepdown Fix
RW= Runway Fix
OM= Outer Marker Fix
IM = Inner Marker Fix
BM = Backcourse Marker Fix
TD = Touchdown Fix inboard of runway threshold
HC = Helipad Fix
EP = Final End Point
If the fix is defined by a bearing and distance:the first character of the fix identifier should be “D”, characters 2 through 4 should be the bearing/radial and the last character should be the distance defining the fix, expressed as the equivalent letter of the alphabet, i.e., A = 1nm, G = 7nm, o = 15nm.
There are a whole heap more rules for fixes on an arc, DME based SDFs, and fixes used for multiple approaches.
