AN A320 COULD NOT PRESSURIZE AFTER TKOF BECAUSE THE SKIN VENT VALVE DOOR WAS NOT PROPERLY MEL'ED IN THE LOCKOUT POSITION. THE ACFT RETURNED TO LAND.

Narrative

AT APPROX 110 KTS DURING TKOF ROLL; AN ECAM FAILURE WARNING FOR VENT SKIN VALVE FAULT OCCURRED. THE TKOF WAS CONTINUED AND AFTER THE AFTER TKOF CHKLIST WAS COMPLETED IT WAS DETERMINED THAT THE ACFT WAS NOT PRESSURIZING PROPERLY. AFTER NOTIFYING MAINT CTL AND DISPATCH; THE DECISION WAS MADE TO RETURN AND LAND AT ZZZ. AFTER BURNING FUEL TO ACHIEVE LNDG WT; A NORMAL LNDG AND PARKING WERE ACCOMPLISHED. THE ECAM PRESSURIZATION PAGE SHOWED THE AVIATION EXTRACTION VENT VALVE WAS AMBER AND IN THE OPEN POS. THIS WAS THE SAME INDICATION WE HAD SEEN AT THE GATE PRIOR TO DEP. BUT BECAUSE OF MEL THAT WAS INSTALLED ON THE ACFT AND THE APPROPRIATE MAINT PREFLT SIGNOFF WAS COMPLETE; WE ASSUMED THAT WAS THE NORMAL INDICATION WITH THAT MEL. AFTER POSTFLT INSPECTION AND DISCUSSION WITH MAINT; IT WAS DETERMINED THAT THE EXTRACTION VALVE WAS SET IN AN IMPROPER POS FOR FLT BY THE MECH THAT SIGNED OFF THE MEL. SUPPLEMENTAL INFO FROM ACN 791040: ACFT X WAS SCHEDULED TO RON IN ZZZ FOR AN OVERNIGHT CHK AND MEL'S TO BE WORKED. MECH PERFORMED A SKIN AIR VALVE CHANGE FOR MEL. AT THE END OF HIS SHIFT HE GAVE A VERBAL TURNOVER TO THE LEAD ABOUT THE WORK REMAINING ON THE JOB. DURING THIS TIME WE HAD A LATE ARRIVING ACFT WITH AN INBOUND WRITE-UP; PLUS ANOTHER MEL THAT WAS IN WORK ON ACFT X. AS THE MORNING PUSH STARTED; WE RECEIVED A GATE CALL AND HAD OTHER ACFT ARRIVING. THE GATE CALL WAS ON ACFT Y FOR A SKIN AIR VALVE FAULT. MAINT CTL WAS NOTIFIED AND MEL WAS APPLIED. WE THEN HAD TO RELOCATE ACFT X FROM THE GATE WHERE IT WAS PARKED; TO ANOTHER GATE FOR ITS DEP. AFTER THE ACFT HAD BEEN MOVED A TECH WAS SENT TO PERFORM THE MEL RECHK FOR THE MORNING FLT. THE MEL WAS SIGNED OFF AS RECHK COMPLIED WITH; AND ACFT X LEFT ZZZ FOR ZZZ1. DURING CLBOUT THE FLT CREW NOTIFIED MAINT CTL THAT THEY COULD NOT PRESSURIZE THE ACFT. THE ACFT WAS TURNED AROUND AND SENT BACK TO ZZZ. AFTER THE ACFT ARRIVED BACK AT THE GATE IT WAS DISCOVERED THAT THE SKIN AIR VALVE DOOR HAD NOT BEEN MANUALLY LOCKED OUT IN ACCORDANCE WITH THE MEL PROCS. THE MEL PROCS WERE REAPPLIED; AND THE DOOR WAS LOCKED OUT AND ALL THE TASKS WERE REVIEWED.