ACR LTT ACFT LANDED WITHOUT CLRNC OUT OF AN ILS APCH IN IMC DUE TO THE FAILURE OF THE PLT TO CONTACT THE TWR.

Narrative

WE WERE FLYING AN LTT ACFT INTO RAPID CITY REGIONAL ARPT. I WAS THE FO FLYING THE ACFT AND THE CAPT WAS WORKING THE RADIOS. WE WERE CLRED FOR AN ILS APCH FOR RWY 32 BY ELLSWORTH APCH AND THE WX WAS 400 OVCST WITH RAIN AND FOG. APCH NEVER TOLD US TO SWITCH TO TWR FREQ. THE CAPT NEVER CALLED THE TWR AND WE LANDED WITHOUT CONTACTING THE TWR. AFTER LNDG; A DIFFERENT VOICE FROM ELLSWORTH APCH TOLD US TO CONTACT TWR. I WAS NEW TO THE ACFT AND THE OP. THE CAPT MAY HAVE BEEN MONITORING ME MORE CAREFULLY THAN USUAL AND WITHOUT DIRECTION FROM APCH CTL; DIDN'T CALL THE TWR. LATER; THE TWR OPERATOR TOLD THE CAPT THAT A SAND TRUCK WAS ON THE RWY AND THAT HE HAD TO ORDER THE TRUCK OFF THE RWY BEFORE WE LANDED. BUT I DON'T KNOW WHY WE WOULD HAVE BEEN CLRED FOR AN APCH WITH A TRUCK WORKING ON THE RWY. BOTH PLTS SHOULD BE AWARE OF THE NEED TO CALL TWR BY THE OM. FROM THE APCH CTL SIDE; DIRECTIONS TO CALL THE TWR SHOULD BE ISSUED WITH THE APCH CLRNC. THE TWR NEEDS TO COORDINATE BETTER WITH APCH; ESPECIALLY WHEN HAZARDOUS CONDITIONS EXIST SUCH AS A SAND TRUCK ON THE RWY.