AN A319'S L MAIN LNDG GEAR DID NOT RETRACT AFTER TKOF BECAUSE AN UNFLAGGED GEAR PIN WAS NOT REMOVED BEFORE FLT.

Narrative

ECAM 'L MAIN LNDG GEAR FAILED TO RETRACT' ALERT. FO CONTINUED FLYING RESPONSIBILITIES. CAPT RAN ECAM; QRH AND FOLLOW UP ACTIONS. RETURNED TO FIELD NORMAL APCH AND LNDG. FO LEG. NORMAL PRE-DEP AND TAXI. AFTER TKOF L LNDG GEAR WOULD NOT RETRACT. ACCOMPLISHED ECAM; QRH AND FOLLOW UP PROCS (RECYCLE GEAR). AFTER RECYCLE GEAR WAS DOWN 3 GREEN NORMAL. ADVISED ZZZ A RETURN TO FIELD; NORMAL OPS. REQUESTED BOX PATTERN TO BURN BELOW MAX LNDG WT. APCH AND LNDG NORMAL. MET MAINT AT GATE. MAINT INFORMED US GEAR LOCK WITHOUT FLAP STREAMER WAS LEFT IN ACFT AFTER OVERNIGHT MAINT. APOLOGIZED FOR MISCUE ATTACHED STREAMER FLAG TO GEAR LOCK CLRED LOGBOOK AND PROCEEDED TO ZZZ1. EVEN THOUGH THIS WAS A FIRST FLT OF DAY IT MIRRORS THE MANY HARRIED AND UNNECESSARY ACFT CHANGES IN 1 DAY. COME IN LATE CHANGE ACFT DO IT QUICK BE NOT ON TIME BUT 10 MINS PRIOR TO DEP. ONLY TO GET THE SAME ACFT BACK THE NEXT TIME THROUGH. NOT MAKING EXCUSES BUT POINTING OUT THAT IN TRYING TO KEEP THIS AIRLINE ON TIME WE RUSH OURSELVES INTO MISSTEPS AND A PATTERN OF MISSTEPS. IF ONLY WE HAD THE TIME ON THE LINE TO OPERATE LIKE WE DO IN THE SIMULATOR.