AN A320 IS PUSHED BACK BY GND CREW WITHOUT A CLRNC FROM ATC OR THE FLT CREW DUE TO A MISUNDERSTANDING.

Narrative

5 MINS PRIOR TO SCHEDULED DEP; THE MECH ON THE GND SIGNALED THE CAPT FOR BRAKE RELEASE (DOORS WERE CLOSED AND WE WERE READY TO GO). ASSUMING MECH WAS TRYING TO HELP WITH AN ON-TIME DEP AND WITH THE DOORS CLOSED AND THE JETWAY PULLED; THE CAPT RELEASED THE BRAKES. EXPECTING COM WITH PUSH CREW VIA HEADSET MOMENTARILY; FO REQUESTED PUSH CLRNC VIA ACARS AND IT WAS RECEIVED AND ROTATING BEACON WAS TURNED ON. AFTER A FEW MINS WITH NO COM FROM GND CREW; FO CALLED RAMP TO CANCEL PUSH CLRNC AND THEN OPS TO REQUEST PUSH CREW. SEVERAL MINS LATER; CAPT OPENED HIS COCKPIT WINDOW AND ASKED THE MECH (SAME ONE WHO GAVE BRAKE RELEASE SIGNAL -- HE WAS JUST STANDING AROUND) IF HE KNEW WHERE OUR PUSH CREW WAS. HE SAID HE WAS GOING TO PUSH US AND ASKED IF WE WERE CLRED TO PUSH. CAPT REPLIED YES; EXPECTING HIM TO CONTACT HIM ON HEADSET. MECH SAID CLRED TO START 1 AND 2 AND IMMEDIATELY GOT IN THE TUG AND COMMENCED PUSHING THE ACFT BACK WITHOUT ANY ADDITIONAL COM. CAPT SOUNDED THE CALL HORN SEVERAL TIMES TO TRY TO STOP HIM BUT HE DID NOT RESPOND. MECH PUSHED ACFT BACK AND THEN GOT OUT OF TUG AND GAVE SIGNAL TO SET BRAKES. CAPT SET BRAKES. DUE TO CHATTER ON RAMP FREQ; FO AND CAPT WERE UNABLE TO INFORM RAMP OF PUSHBACK UNTIL AFTER THE FACT. ATC REPLIED EXPECT W TAXI AND CALL WHEN READY. FO ADVISED COMPANY MECH HAD PUSHED US BACK WITHOUT CLRNC. WE STARTED ENGS; MECH GAVE SALUTE AND RELEASE FROM GUIDANCE; WE RECEIVED TAXI CLRNC AND TAXIED TO RWY. PRIOR TO CLOSING THE DOOR; THE MECH NEVER COMMUNICATED TO US THAT WE WOULD PUSH USING HAND SIGNALS. DURING THE PUSHBACK THERE WERE NO OTHER ACFT MOVING ON THE RAMP. FO ALSO TOLD OPS THAT WE WOULD FILE A RPT.