Transponder codes have numbers not limited to the 0-7 range (which obviously is rather unrealistic as well as not supported by FlightGear). Moreover, IDENT is not available and that might be quite a hassle when it comes to integrations with addons/multiplayer etc. Also, the transponder seems to be permanently in STBY mode (or at least that's what is displayed).
Transponder codes have numbers not limited to the 0-7 range (which obviously is rather unrealistic as well as not supported by FlightGear). Moreover, IDENT is not available and that might be quite a hassle when it comes to integrations with addons/multiplayer etc. Also, the transponder seems to be permanently in STBY mode (or at least that's what is displayed).