ABNORMAL GEAR WARNING HORN ACTIVATION WHEN GEAR HANDLE PLACED IN UP POS. NORMAL DOWN. RETURN LAND.

Narrative

AFTER LIFT OFF FROM RWY 28 AT BWI; AND A POSITIVE RATE OF CLB WAS ESTABLISHED; I DEPRESSED THE BRAKE PEDALS AND CALLED FOR THE GEAR TO BE RETRACTED. AS SOON AS THE CAPT SELECTED 'GEAR UP'; THE GEAR UNSAFE HORN SOUNDED (NOT NORMAL). THE LNDG GEAR LIGHTS CYCLED PROPERLY THROUGH THE 'TRANSITION' PHASE OF RETRACTION AND EXTINGUISHED. THE GEAR UNSAFE HORN HOWEVER WAS STILL ON. CYCLING THE GEAR SEVERAL TIMES DID NOT RECTIFY THE PROBLEM WHEN THE GEAR WAS DOWN; ALL INDICATIONS WERE OFF; WHEN UP; THE HORN WAS BLARING; THE GEAR WAS SELECTED DOWN AND LEFT THERE. (THERE IS NO EMER PROC IN OUR MANUALS FOR THIS PARTICULAR PROBLEM). ATC WAS NOTIFIED; AND CLRED US FOR VISUAL APCH TO 28 AND CLRED US TO LAND. WE DID NOT DECLARE THIS AN EMER SINCE ALL INDICATIONS WERE GOOD WITH GEAR DOWN. (FLT ATTENDANT WAS ALSO NOTIFIED). WE LANDED WITHOUT INCIDENT OR ACCIDENT ON RWY 28. DURING TAXI BACK TO THE GATE; COMPANY WAS NOTIFIED AND PAX DISEMBARKED AT THE GATE. THIS RPT WAS FILED AT THE SUGGESTION OF OUR APA SAFETY REPRESENTATIVE ALONG WITH A MECH IRREGULARITY RPT AND AN APA SAFETY DEBRIEF. CAUSE OF PROBLEM: UNKNOWN AT THIS TIME.