At least on the English localization, prompts to handoff to a UNICOM frequency are missing. This issue is prevalent if you are flying a filed IFR flight plan where your destination is an untowered airport. The ATC logs would hilariously result similar to the following:
ATC : Cessna 1FA, you are 12 miles west of Cable.
Pilot : , Cessna 1FA.
Sometimes, a vector may be provided—otherwise there is no mention of the frequency to contact.
I’ve dug in to this bug and found out that the handoff to advisory prompts are indeed coded into the sim according to the localization files! They’re indicated as the flags {AGNT_ADD_SWITCH_ADVISORY} and {PILOT_ADD_ADVISORY_ON}. Those flags correspond to the respective lines (here in the English localization file, en-US.locPak):
"ATCCOM.AGNT_ADD_SWITCH_ADVISORY_YES.0.text": " Switch to advisory on {frequency_new}.",
"ATCCOM.AGNT_ADD_SWITCH_ADVISORY_YES.0.tts": " Switch to advisory on {frequency_new}.",
"ATCCOM.PILOT_ADD_ADVISORY_YES.0.text": " Advisory on {frequency_new}",
"ATCCOM.PILOT_ADD_ADVISORY_YES.0.tts": " Advisory on {frequency_new}",
However, the handoff prompts apparently do not contain the event flag that would trigger the advisory handoff prompt, essentially rendering those as unused.
I isolated the affected prompts that are missing the advisory handoff flag. The following applies to when ATC contacts you for the handoff to new frequency:
"ATCCOM.AGNT_AC_CLEARED_APPROACH_FULL_PROCEDURE.0.text": "{callsign_shortened}, you are{location_destination} of {airport_destination}.{AGNT_ADD_CONTACT_TOWER}",
"ATCCOM.AGNT_AC_CLEARED_APPROACH_FULL_PROCEDURE.0.tts": "{callsign_shortened}, you are{location_destination} of {airport_destination}.{AGNT_ADD_CONTACT_TOWER}",
"ATCCOM.AGNT_AC_CLEARED_APPROACH_VECTORS_TO_FINAL.0.text": "{callsign_shortened}, you are{location_destination} of {airport_destination}. {vector}. {AGNT_ADD_CONTACT_TOWER}",
"ATCCOM.AGNT_AC_CLEARED_APPROACH_VECTORS_TO_FINAL.0.tts": "{callsign_shortened}, you are{location_destination} of {airport_destination}. {vector}. {AGNT_ADD_CONTACT_TOWER}",
And the corresponding responses by the (co)pilot:
"ATCCOM.AC_AGNT_CLEARED_APPROACH_FULL_PROCEDURE.0.text": "{PILOT_ADD_TOWER_ON}, {callsign_shortened}.",
"ATCCOM.AC_AGNT_CLEARED_APPROACH_FULL_PROCEDURE.0.tts": "{PILOT_ADD_TOWER_ON}, {callsign_shortened}.",
"ATCCOM.AC_AGNT_CLEARED_APPROACH_VECTORS_TO_FINAL.0.text": "{vector}.{PILOT_ADD_TOWER_ON} {callsign_shortened}",
"ATCCOM.AC_AGNT_CLEARED_APPROACH_VECTORS_TO_FINAL.0.tts": "{vector}.{PILOT_ADD_TOWER_ON} {callsign_shortened}",
Since all they are missing is the respective handoff to advisory flag, they simply need the flag added:
"ATCCOM.AGNT_AC_CLEARED_APPROACH_FULL_PROCEDURE.0.text": "{callsign_shortened}, you are{location_destination} of {airport_destination}.{AGNT_ADD_CONTACT_TOWER}{AGNT_ADD_SWITCH_ADVISORY}",
"ATCCOM.AGNT_AC_CLEARED_APPROACH_FULL_PROCEDURE.0.tts": "{callsign_shortened}, you are{location_destination} of {airport_destination}.{AGNT_ADD_CONTACT_TOWER}{AGNT_ADD_SWITCH_ADVISORY}",
"ATCCOM.AGNT_AC_CLEARED_APPROACH_VECTORS_TO_FINAL.0.text": "{callsign_shortened}, you are{location_destination} of {airport_destination}. {vector}. {AGNT_ADD_CONTACT_TOWER}{AGNT_ADD_SWITCH_ADVISORY}",
"ATCCOM.AGNT_AC_CLEARED_APPROACH_VECTORS_TO_FINAL.0.tts": "{callsign_shortened}, you are{location_destination} of {airport_destination}. {vector}. {AGNT_ADD_CONTACT_TOWER}{AGNT_ADD_SWITCH_ADVISORY}",
"ATCCOM.AC_AGNT_CLEARED_APPROACH_FULL_PROCEDURE.0.text": "{PILOT_ADD_TOWER_ON}{PILOT_ADD_ADVISORY_ON}, {callsign_shortened}.",
"ATCCOM.AC_AGNT_CLEARED_APPROACH_FULL_PROCEDURE.0.tts": "{PILOT_ADD_TOWER_ON}{PILOT_ADD_ADVISORY_ON}, {callsign_shortened}.",
"ATCCOM.AC_AGNT_CLEARED_APPROACH_VECTORS_TO_FINAL.0.text": "{vector}.{PILOT_ADD_TOWER_ON}{PILOT_ADD_ADVISORY_ON} {callsign_shortened}",
"ATCCOM.AC_AGNT_CLEARED_APPROACH_VECTORS_TO_FINAL.0.tts": "{vector}.{PILOT_ADD_TOWER_ON}{PILOT_ADD_ADVISORY_ON} {callsign_shortened}",
After this fix is applied to the localization file, ATC logs will now correctly show intended behaviour for the handoff to advisory!
ATC : Cessna 1FA, you are 12 miles west of Cable. Switch to advisory on 123.0.
Pilot : Advisory on 123.0, Cessna 1FA.
Hopefully when the next update rolls around soon, this issue should be easily fixed.