Unless you are N-reg and squitting ADS-B then it is also required.
For any aircraft weight? That would surprise a lot of people who bought some new kit. Fairly obviously ATC aren’t bothered.
JasonC wrote:
Unless you are N-reg and squitting ADS-B then it is also required.
How would you know that?
I bet almost nobody in the USA follows it, either. They have only just started to move to ICAO flight plans 
Peter wrote:
I bet almost nobody in the USA follows it, either. They have only just started to move to ICAO flight plans
I wouldn’t be so sure. ADS-B is extensively used by ATC in the US.
@achima
“Well, filing thousands of IFR flight plans every month throughout Europe and beyond does give me a certain level of insight.”
Ok so what would happen if say there was a * or some other caracter in the CODE field ?
That would cause an error in the Eurocontrol system and be rejected. There is very strict input validation and consistency checking before flight plans get accepted.
Fine, so how would YOU explain that on at least 4 occasions ATC complained that they were not receiving mode S code when the AC was squawking 1000 but when squawking a discreet Id ATC recv’d the proper codes from the xponder ?
NB this occurred in both Germany & France
Probably something wrong with the transponder. Not radiating Mode S or no flight ID / incorrect flight ID set.
Borrow an Aeroflex IFR 6000 and check what’s coming. Also Flightradar 24 could be useful.
There is a good chance that some ATC units use the optionally present CODE/ as a fallback for a non working Mode S flight ID. It would be smart to do so because not being able to identify an aircraft in the normal way increases controller workload, i.e. reduces sector capacity. If a discreet code is assigned, identification is also possible without Mode S flight ID which explains why the complaints are limited to squawk 1000.
How can something be wrong with the xponder if all is ok with a discreet squawk ?
