A320 ACFT WITH DEFERRED FUEL AUTO FEED INOP; PROC CALLS FOR CTR TANK PUMPS TO REMAIN OFF UNTIL SLAT RETRACTION. FLC INADVERTENTLY TURNED ON ALL PUMPS IN ACCORDANCE WITH NORMAL PROC CHKLIST. DURING CLB FUEL XFERRED TO VENT TANK AND THEN OVERBOARD WHERE IT WAS SIGHTED BY PAX. EMER DECLARED AND FLT RETURNED TO DEP ARPT.

Narrative

WE WERE CLBING OUT OF PHX. ON OUR DEP WHEN THE FIRST FLT ATTENDANT CAME TO THE COCKPIT; SHE SAID PAX ON THE R SIDE OF THE ACFT WERE SEEING FUEL COMING FROM THE R WING. I SENT THE FO BACK TO THE CABIN TO CONFIRM THE SIGHTING. HE STATED THAT FUEL INDEED WAS COMING FROM THE R WING. WE DECLARED AN EMER AND PROCEEDED BACK TO PHX. THE FLT ATTENDANTS WERE BRIEFED; DISPATCH AND MAINT WERE NOTIFIED AND ALL APPROPRIATE CHKLISTS WERE PERFORMED. AN UNEVENTFUL OVERWT LNDG WAS ACCOMPLISHED. THE FIRE TRUCKS INSPECTED THE ACFT AND WE TAXIED TO THE GATE. BACKGROUND: WE RECEIVED THE ACFT THAT MORNING WITH 3 MEL'S ON IT. THE FIRST WAS A FLT CTL STATUS MESSAGE. THE SECOND WAS THAT THE FUEL AUTO FEED WAS INOP; AND THE THIRD WAS AN INOP APU. WE READ THE MEL BOOK FOR COMPLIANCE ON ALL THREE AND BRIEFED THE OPERATIONAL IRREGULARITIES FOR EACH AS WELL. THE FUEL MEL STATED THAT THE CTR TANK PUMPS HAD TO REMAIN OFF UNTIL AFTER SLAT RETRACTION (AFTER TKOF). THE MEL DID NOT STATE THAT THE AUTO FEED SWITCH HAD TO BE PLACARDED. SINCE THERE WAS NO APU; WE PULLED THE QRH AND BRIEFED THE PROC FOR A 'START WITH EXTERNAL PWR' AND A 'XBLEED START.' AFTER THAT; ALL FLOWS AND CHKLISTS WERE COMPLETED. ONE OF THE CAPT'S FLOWS IS 'FUEL PUMPS ON;' AND DUE TO COMPLACENCY OR HABIT; THE CTR TANK PUMPS WERE INADVERTENTLY TURNED ON. IN HINDSIGHT; THIS SCENARIO CAUSED THE FOLLOWING SIT TO OCCUR. THE CTR FUEL NOW COOLED THE IDG AND RETURNED TO THE WINGS. BUT THE WINGS WERE FULL AND THEREFORE FLOWED TO A 50 GAL VENT TANK IN THE OUTER WING. WHEN THAT FILLED UP IT VENTED OVERBOARD; AND THAT IS WHAT THE PAX SAW. IT WAS AN UNFORTUNATE SIT THAT COULD POSSIBLY HAVE BEEN AVOIDED BY THE FOLLOWING: 1) AFTER READING THE MEL I SHOULD HAVE CONFIGURED THE FUEL PANEL THEN INSTEAD OF DURING MY FLOW. 2) PLACARD THE FUEL PANEL AS A REMINDER OF AN ABNORMAL SIT. SINCE THIS INCIDENT OCCURRED; OUR COMPANY'S FORTHCOMING NEW MEL FOR THE ACFT STATES THAT THE FUEL PANEL WILL BE PLACARDED FOR AN ABNORMAL OP. SUPPLEMENTAL INFO FROM ACN 401070: AFTER GETTING SITUATED IN THE COCKPIT; THE CAPT SAID THAT WE HAD 3 MELS ON THE ACFT. ONE WAS A FLT CTL STATUS MESSAGE; REQUIRING NO ACTION. THE SECOND ONE STATED THAT THE APU WAS INOP -- WE TALKED ABOUT CALLING FOR AN AIR CART AND THE PROCS FOR AN EXTERNAL START AND A CROSSBLEED START AFTER TAXI. THE THIRD MEL SAID THAT THE AUTOMATIC FUEL SYS WAS INOP. THE CAPT SAID THAT; BECAUSE OF THIS; WE WOULD NEED THE CTR TANK FUEL PUMPS OFF FOR TKOF. WE THEN REVIEWED THE CHKLISTS FOR EXTERNAL AIR START AND CROSSBLEED START; DID OUR FLOWS; AND COMPLETED THE 'BEFORE START' CHKLIST. APPARENTLY; WITH EVERYTHING ELSE GOING ON; WHEN THE CAPT DID HIS FLOW HE LOOKED AT THE FUEL QTY AND POSITIONED ALL SIX PUMPS ON (WHICH IS THE NORMAL POSITION). ON THE 'BEFORE START' CHKLIST I CALLED; 'FUEL;' AND THE CAPT CALLED; '30.6; SIX PUMPS ON;' WHICH IS THE RESPONSE I AM USED TO HEARING. WE BOTH MISSED THAT THE CTR FUEL TANK PUMPS SHOULD HAVE BEEN OFF; AS WE HAD TALKED ABOUT BEFORE. AFTER DEP; WE WERE TOLD BY THE FLT ATTENDANTS THAT WE HAD SOMETHING LEAKING FROM THE R WING. I WENT BACK AND CONFIRMED THIS. THE CAPT DECLARED AN EMER; DUE TO THE OVERWEIGHT LNDG; WHILE I TALKED TO MAINT; OPS; AND THE FLT ATTENDANTS. MAINT HAD NO EXPLANATION OF WHAT MIGHT BE CAUSING THIS. WE REVIEWED THE OVERWEIGHT LNDG CHKLIST AND RETURNED TO PHX. AFTER CLRING THE RWY WE HAD THE FIRE TRUCKS INSPECT US FOR LEAKS AND THEY CLRED US TO THE GATE. IT WAS NOT UNTIL AFTER WE SHUT DOWN AT THE GATE THAT WE REALIZED WE HAD OVERLOOKED THE NEED FOR THE CTR TANK PUMPS TO BE OFF DURING TKOF. THIS IS WHAT CAUSED THE FUEL VENTING IN FLT AND THE RETURN TO PHX.