DHC-8 FLT CREW TAXIES AND DEPARTS WITH A GEAR DOOR WARNING LIGHT. AFTER RETRACTION OF GEAR; 'GEAR INOP' LIGHT ILLUMINATES. EMER DECLARED; ACFT RETURNED FOR LNDG; UNEVENTFUL LNDG.

Narrative

DURING TAXI FOR TKOF; DISCOVERED L MAIN GEAR DOOR REMAINED OPENED. HOLDING SHORT OF RWY; WE DISCUSSED OPTIONS. NORMALLY; THE FLT CREWS ARE CONSTANTLY OPENING/CLOSING THE GEAR DOORS FOR PREFLT INSPECTIONS. WE FELT THAT THERE WAS NO DANGER OR PROB DIRECTLY RELATED WITH LNDG GEAR ITSELF AND WE HONESTLY THOUGHT THE DOOR WOULD CLOSE NORMALLY AFTER GEAR CYCLE. WX NOT AN ISSUE AS IT WAS CLR SKIES AND CALM WINDS. AFTER TKOF CLBED AT 130 KTS; RETRACTED GEAR AND STOWED NORMALLY. L DOOR REMAINED OPEN. MAINTAINED DSCNT 140 KTS AIRSPD. SINCE THE DOOR REMAINED OPEN; CAUSED THE 'LNDG GEAR INOP' CAUTION SINCE IT WAS NOT COMPLETE CYCLE. FOLLOWED COMPANY PROC RELATED TO THIS MALFUNCTION. COMPLETED APPROPRIATE CHKLISTS AND PROCS. EXTENDED GEAR MANUAL PER FLT MANUAL. DECLARED EMER LNDG AS A PRECAUTION. LANDED UNEVENTFUL AND STOPPED ON RWY. MAINT STAFF AWAITING AND PINNED GEAR/TOWED ACFT SHORT DISTANCE TO PARKING. DEPLANED AT GATE NORMALLY. ACFT REPAIRED BY MAINT CREW SHORT TIME LATER. WAS TOLD A STUCK VALVE. IN RETROSPECT; WE SHOULD HAVE JUST RETURNED TO GATE UPON DISCOVERY OF DISCREPANCY. WE HONESTLY DID NOT FORESEE THE PROB AFTER RETRACTION 'CAUTION' LIGHTS RELATED.