Is it possible to handle naming duplictates for teminal points in ARINC-424?

Question

In ARINC-424 17 specification, under 7.2.6 Terminal Waypoints subsection A the "Airport/Heliport or Runway/Helipad related Terminal Waypoints" naming conventions are described. It describes the steps to be taken in order to avoid duplicates.

For example: a final approach fix (FAF in short) on runway 36 for example, will be named FF36 which works either for "Single Approach Procedure" or approaches that share a "common waypoint". If the common waypoint idea can't be applied, then the second letter becomes the route type described in section 5.7. So the FAF for a VOR approach on 36 will be FV36, for an ILS on 36 FI36 and so on and so forth.

But here lies the problem (which unfortunately I am currently facing): what if there are more than one approaches of the same type on the same runway that can't share the same points? I have 2 VOR approaches where all points IAF, IF, FAF etc. do not coincide. According to the spec:

waypoint identifiers will be unique only for the airport specified; a waypoint identifier used in a terminal area cannot be repeated in that terminal area

I could get away with it as there are is no parallel runway and I can start adding numbers (eg FV361, FV362 etc.) and it won't make any significant difference as these points will be used for simulation purposes and I have a couple of ways to "cheat". Though knowing what happens in reality will add to the simulation realism.

Answer 1

Based on your example of LGEL, I found 3 VOR approaches in my navigation database with the following points:

Approach	Cx Name	Fx Name	Mx Name
D36LY	CD3LY	FD3LY	MD3LY
D36RW	CD36	FD36	MD36
VORA	CD36	FD36	MD36

As you can see, the VOR W RWY 36 R approach (where you also linked the chart) uses the normal naming convention for a runway 36. The VOR A is the circle to land approach using the same waypoints. The interesting one is the VOR Y RWY 36 L approach, which uses different waypoints. The naming now uses only the first digit of the runway number (3 instead of 36), followed by L for 36L and then the letter of the approach (here Y).

This allowed me to search my navigation database for similarly named waypoints and sure enough I found a good example, where there are 2 approaches to the same runway using a different waypoint at LIRP (Pisa San Giusto):

Approach	Cx Name	Fx Name	Mx Name
D04LZ	CD0LZ	FD04L	MD04L
S04LY	CD0LY	FD04L	MD04L

As you can see, both approaches use the same final approach fix (Fx) and missed approach fix (Mx), but a different final approach course fix (Cx) using the naming convention described above.

The same convention can also be applied when there is no left/right/center. E.g. EBBR (Brussels) uses Cx waypoints CD25Y and CD25Z for runway 25.

My copy of the ARINC 424 standard does not describe this convention, but apparently this is what Jeppesen uses.