LR31 LANDS AT IAD WITHOUT CALLING TWR AND HEARING LNDG CLRNC.

Narrative

AFTER LNDG ON RWY 19R; FOLLOWING A VISUAL APCH AT IAD; THE CTL TWR ADVISED US THAT WE HAD BEEN 'CLRED TO LAND IN THE BLIND.' WE WERE ADVISED THIS ON TWR FREQ 120.1. AFTER TAXIING INTO THE RAMP; I CALLED THE TWR; CONFUSED ABOUT WHAT HE HAD SAID. HE INFORMED ME THAT TWR FREQ FOR RWY 19R WAS 128.42 (APCH CTL HAD GIVEN US 120.1 WHICH WAS THE FREQ FOR RWY 19L). THE CTLR ON 128.42 HAD BEEN LISTENING FOR US TO CALL; AND WHEN WE NEVER DID; HE CLRED US TO LAND ON RWY 19R; BUT WE HAD NEVER REPLIED TO HIS XMISSION. AFTER WE LANDED; HE TRIED US ON 120.1 AND GOT A HOLD OF US. NOW THINKING BACK; I REMEMBER APCH CTL HANDING US OVER TO TWR ON 120.1 (THE WRONG FREQ FOR RWY 19R) AT THE TIME I WAS RUNNING THE 'BEFORE LNDG CHKLIST.' I MADE THE DECISION TO CALL TWR AFTER I WAS DONE WITH THE CHKLIST. APPARENTLY; I NEVER CALLED TWR ON 120.1; AND IF I HAD; THE CTLR ON THAT FREQ WOULD HAVE TOLD ME TO CALL 128.42. SEVERAL THINGS LED TO THIS EVENT. ONE WAS THAT IT HAD BEEN A LONG DAY FOR THE FLT CREW AND WE WERE TIRED AS WE CAME IN FOR OUR FINAL APCH AND LNDG. NEXT; I NEVER CALLED TWR TO GET A LNDG CLRNC; AND LANDED WITHOUT EVEN REALIZING IT! ADDITIONALLY; APCH CTL GAVE US THE WRONG TWR FREQ; SO WE NEVER HEARD THE CTLR ON THE CORRECT FREQ CLRING US TO LAND. FINALLY; I WAS BUSY; IN THE MIDDLE OF RUNNING A CHKLIST AT THE TIME OF THE HDOF TO TWR; WHICH CONTRIBUTED TO ME FORGETTING TO CALL THE TWR. HAD I CALLED THE TWR; THE CTLR WOULD HAVE GIVEN US THE CORRECT FREQ. FORTUNATELY; WE WERE CLRED TO LAND BY ATC (ALTHOUGH IN THE BLIND) EVEN THOUGH WE NEVER HEARD IT.