FLC TOOK OFF WITH MAINT BLOCKING DEVICE IN LNDG GEAR STRUT WHICH IMPEDED RETRACTING THE GEAR.

Narrative

ARRIVED AT XA00 FOR AN XA45 DEP FROM TYS TO CLT. WE CHKED IN WITH FLT CTL VIA TELEPHONE AND WERE ADVISED THAT THE AIRPLANE HAD A LUGNUT MISSING THAT WAS NOTICED ON PREFLT BY PREVIOUS CREW. FLT CTL TOLD ME THERE WOULD BE 2 MECHS ON A XA25 ARR COMING FROM PITTSBURGH; AND THAT WE COULD ANTICIPATE A 20 MIN DELAY. THE 2 MECHS ARRIVED ON TIME; FIXED THE LUGNUT AND IN 20 MINS WERE ON THE RETURN FLT TO PITTSBURGH. UNFORTUNATELY; THEY LEFT A GEAR STRUT EXTENSION BAR ON THE R GEAR. I HAD THE FO CHK THE GEAR BEFORE TKOF AND HE MISSED SEEING THE BAR. NORMAL TKOF; BUT GEAR WOULD NOT RETRACT. GEAR WAS DEACTIVATED BY JACK; CAUSING GEAR OVERRIDE TO NOT ALLOW GEAR RETRACTION. ASKED FOR EXTENDED DOWNWIND AND DID ALL APPROPRIATE CHKLISTS. LANDED NORMALLY. AFTER SHUTDOWN; I WENT TO R GEAR AND DISCOVERED PROB. NO DAMAGE. THIS SHOULD NOT HAPPEN. WHAT CAUSED THIS PROB IN MY OPINION: 1) 2 MECHS DOING 1 JOB. 2) MECHS BEING RUSHED. 3) MY COPLT DID NOT DO WHAT I ASKED HIM TO DO. DIDN'T WANT TO GET HIS HANDS DIRTY. 4) ON TAXI OUT; THERE COULD HAVE BEEN A CAUTION MESSAGE 'WOW PROXY' BUT I DON'T RECALL SEEING IT; BUT SINCE I'M NEW IN THE AIRPLANE AND I DON'T KNOW WHAT IS NORMAL; I COULD HAVE MISSED IT. I NOTICED IT IN THE AIR AFTER GEAR WOULDN'T COME UP.