A CE560 CREW LANDED ON DPA RWY 15 VERSUS RWY 20R AS CLEARED; A 3400 FT RWY.

Narrative

UPON EXECUTING THE ILS 10; CIRCLE TO RWY 20R AT DPA; WE GAINED VISUAL CONTACT WITH THE ARPT AT 700 FT AGL. WE STOPPED THE DSCNT AT CIRCLING MINIMUMS; WHICH HAPPENED TO BE JUST OVER 600 FT AGL. UPON VISUAL IDENT OF THE ARPT; I TRANSITIONED MY ATTN TO INSIDE THE COCKPIT; IN ORDER TO MONITOR THE FLT INSTS WHILE THE FO (PF) TRANSITIONED TO VISUAL REFS; OUTSIDE OF THE COCKPIT. IT WAS AT NIGHT; WITH RAIN; TURB; AND A GUSTY WIND FROM THE S. THE FO ACKNOWLEDGED HAVING THE RWY IN SIGHT. I WAS FOCUSED ON MONITORING HIS AIRSPD AND VERT SPD; AS FLUCTUATIONS WERE OCCURRING. IN THE PROCESS; WE WERE IN A TURN TOWARD THE LNDG RWY; AND I NEGLECTED TO VERIFY THE CORRECT RWY ALIGNMENT. THE ENTIRE PROCESS HAPPENED VERY QUICKLY. DURING LNDG; UPON ROLLOUT; THE TWR ADVISED US 'USE CAUTION; YOU ARE ON RWY 15.' WE ACKNOWLEDGED; AND TURNED ONTO AN ADJOINING TXWY WITHOUT FURTHER INCIDENT. THE FACT THAT IT WAS NIGHT; MARGINAL CONDITIONS; TURBULENT; GUSTY WINDS; AND BEING IN A TURN TOWARDS THE RWY; ALL PLAYED A ROLE IN THE EVENT. AS AIRSPD AND VERT SPD WERE FLUCTUATING; I CONCENTRATED ON KEEPING THE FO APPRISED OF OUR INDICATIONS IN THE COCKPIT; TAKING FOR GRANTED THAT HE HAD THE CORRECT RWY IN SIGHT. THE PROPER CORRECTIVE ACTION WOULD HAVE BEEN TO DOUBLECHK RWY ALIGNMENT WITH THE HSI. THE LNDG RWY DID NOT HAVE AN INST APCH FOR RWY VERIFICATION. A LONG DUTY DAY OF OVER 12 HRS ALSO CONTRIBUTED TO THIS SITUATION. HAD WE EXECUTED THE PROPER CORRECTIVE ACTIONS FOR THIS SITUATION; AND REALIZED WE WERE LINED UP ON THE WRONG RWY; A MISSED APCH SHOULD HAVE BEEN EXECUTED.