AN A320 RECEIVED AN 'AVIONICS SMOKE' ECAM. AN EMER WAS DECLARED WITH A RETURN TO LAND. THE SMOKE WARNING'S SOURCE WAS NOT IDENTED.

Narrative

DEPARTING ZZZ AT ABOUT 6000 FT WE HAD AN AVIONICS SMOKE ECAM. WE NOTIFIED FLT ATTENDANTS AND ASKED THEM IF THEY COULD SMELL ANY SMOKE. THE RESPONSE WAS NEGATIVE AND WE INFORMED THEM OF AN IMMEDIATE LNDG. ATC WAS NOTIFIED OF THE EMER AND WE IMMEDIATELY TURNED DOWNWIND. WE BRIEFED THE OVERWT CONDITION AND PERFORMED A NORMAL APCH. I TOOK CTL OF THE ACFT FOR LNDG AND TOUCHDOWN WAS LESS THAN 300 FPM. UPON EXITING THE RWY THE ECAM DISAPPEARED. MAINT WAS UNABLE TO DETERMINE CAUSE OF ECAM BUT THEY REPLACED A COMPUTER IN THE AVIONICS BAY AND CLEANED SMOKE SENSORS. REST OF DAY WAS UNEVENTFUL. SUPPLEMENTAL INFO FROM ACN 710863: ON THE DEP; CLBING OVERHEAD THE ARPT; WE RECEIVED AN AVIONICS SMOKE ECAM WITH 'LAND ASAP' DISPLAYED. WE TOLD ATC AND THE FLT ATTENDANTS THAT WE WERE RETURNING FOR LNDG IMMEDIATELY. (WE ALSO ASKED THE FLT ATTENDANTS IF THERE WAS SMOKE IN THE CABIN WHICH THEY RESPONDED TO AS 'NO.') THE TURN DOWNWIND AND TIMELY APCH WAS NORMAL. THE CAPT BECAME THE PF DURING THE DOWNWIND LEG. THE OVERWT CONDITION WAS BRIEFED AND CONSIDERED NOT TO BE A FACTOR. THE TOUCHDOWN WAS SMOOTH. UPON EXITING THE RWY THE ECAM DISAPPEARED. MAINT WAS UNABLE TO DETERMINE THE CAUSE OF THE ECAM. I WAS SATISFIED WITH THE RESULTS OF OUR SHORT FLT BUT WAS QUITE SCARED BY THE NATURE OF THE ECAM.