FO OF AN LTT FORGOT TO CLOSE THE LNDG GEAR DOORS AFTER PREFLT RESULTING IN RETURN TO LAND WHEN THE GEAR FAILED TO RETRACT.

Narrative

'GEAR UNSAFE' LIGHT REMAINED ON AFTER GEAR WAS SELECTED UP BY CAPT/PNF. RECYCLED AND ATTEMPTED TO RETRACT GEAR; AGAIN UNSUCCESSFULLY. LOWERED GEAR AND GOT 3 GREEN DOWN AND LOCKED INDICATION. ADVISED ATC NEEDED TO RETURN FOR LNDG. PERFORMED ACFT 'GEAR NOT UP AND LOCKED' CHKLIST; PLUS NORMAL DSCNT AND LNDG CHKLIST. LNDG WAS NORMAL. TAXIED TO GATE; DEPLANED PAX AND CONTACTED MAINT. THE GEAR WOULD NOT RETRACT BECAUSE THE FO LEFT THE GEAR DOORS OPEN AFTER PREFLTING THE ACFT. THE AIR LOAD ON THE DOOR MOVED IT ENOUGH TO PREVENT GEAR RETRACTION. NO DAMAGE WAS DETECTED BY MAINT TO EITHER THE DOOR; TIRES; OR GEAR. AS CAPT I WAS RESPONSIBLE FOR CATCHING THE FO'S MISTAKE. CONTRIBUTING FACTORS WERE THE FO'S INEXPERIENCE; THE DARKNESS AT THAT HR OF THE MORNING AND CAPT'S FAILURE TO NOTICE OPEN GEAR DOORS. ALL SUBSEQUENT ACTION AFTER GEAR WOULDN'T RETRACT WERE IN ACCORDANCE WITH COMPANY POLICY AND ACFT CHKLISTS; AND NO DAMAGE OR INJURY OCCURRED. NO VIOLATION OF FARS OCCURRED. NO EMER WAS DECLARED; AS ALL ACFT INDICATIONS WITH THE GEAR SELECTED DOWN WERE NORMAL. NO PRIORITY HANDLING WAS REQUESTED OR REQUIRED. IN THE FUTURE; I WILL BE MUCH MORE CAUTIOUS ABOUT TRUSTING LOW- TIME FO'S WITH PREFLT DUTIES; AS THE RESPONSIBILITY FOR PREPARING THE ACFT CORRECTLY IS ULTIMATELY MINE.