A320 Transponder Auto Mode
 

While operating Xponder in AUTO, ATC has complained that some of our MSNs are squawking Mode A while on ground, when it should only be replying Mode S,
forcing us to switch it to SBY while taxying, what if SMGS requires only MODE S.
is this a miss wiring of the system? or am i missing something,
Thanks.

Did you switch TCAS to standby? Otherwise Mode A will be active...

Looking at the FCOM, it says that transponder on auto on ground will only transmit on mode S. However, a recent modification to our SOPs now has us switching transponder to stby just as we park. "To avoid interference with ground radar" it says. I can't think of another possibility other than safelife's

we have been switching Xpdr to Stby with engine shutdown on 320s for years, and operating more than 150 320-Family A/C

if that helps

That's our SOP as well, when we get our squawk code we set it and turn the Xpdr back to auto. Some airports want it left on after landing until we're parked.

It is in the "older" FCOMs : In AUTO position on ground, the Transponder does not transmit anything. It starts transmitting in AUTO as soon as one engine is started. When the selector is set to ON, on ground, even with both engines stopped, the transponder is transmitting assigned squawk code and callsign as inserted on the INIT page of the MCDU. Verified it the other day with a cooperative Ground Controller.
Thus, on many big airports, as per notams or Jeppesen Airport plates, pilots are required to make themselves "visible" to the GMC radar, by switching the transponder to on, as they might be pushed back for a while before they'd be allowed to start the engines, hence, just before push back set the transponder to ON and as soon as you have an engine above the oil pressure red line ( information from the maintenance guys which I could not verify ) you can select the transponder back to AUTO. Now, I stand corrected whether the newer A320s in AUTO transponding mode transmit either the squawk or the callsign only, on ground with engines shut down, when the selector is ON it transmits both : the callsign and the squawk code. Hope this helps, Cheers and safe flying, SA.

stick 1000 in,
Job done