ACR MLG CREW FAILS TO HEAR TWR ISSUE GAR COMMAND ON SHORT FINAL WHEN THEY EXPERIENCE LOSS OF COM ON TWR FREQ.

Narrative

EARLY IN THE FLT; WE DISCOVERED THAT OUR ACFT; AN LGT; HAD CAUSED A 'STUCK MIKE' CONDITION ON A VHF COM FREQ WHEN WE SWITCHED OVER TO THAT ATC FREQ. WE ISOLATED THE PROB TO A SWITCH ON THE CAPT'S VHF COM PANEL (OR SO WE THOUGHT) AND DID NOT MOVE THAT SWITCH AGAIN. ON OUR ARR IN THE ORD AREA; WE WERE HANDLED BY APCH CTL; VECTORED ONTO THE ILS 27L LOC; AND TOLD TO CONTACT ORD TWR AT WILLIT. THIS WAS ACCOMPLISHED; AND WE WERE CLRED TO LAND 27L. FO WAS FLYING HIS FIRST APCH AND LNDG IN LGT ON THE FIRST DAY OF HIS INITIAL OPERATING EXPERIENCE. AFTER RECEIVING LNDG CLRNC; AND WELL INSIDE OM (WILLIT); AND WHILE KEEPING A WATCH OUTSIDE; AND SUPERVISING MY BRAND NEW FO; I DID NOTICE A COMMUTER ACFT THAT WAS; OR APPEARED TO BE; HOLDING SHORT OF EITHER 27L; OR 22L. HE WAS CLR OF OUR APCH PATH; AND RWY 27L; TO OUR R. AFTER TOUCHDOWN; DURING ROLLOUT; I REALIZED THAT THE FREQ WAS VERY QUIET. SUSPECTED A 'STUCK MIKE' CONDITION AGAIN; CLRED THE RWY; AND RE-ESTABLISHED CONTACT WITH ORD GND CTL. WE WERE THEN CLRED TO THE GATE. UPON ARR; I WAS ASKED TO CALL ORD TWR; WHICH I DID. THEY ACKNOWLEDGED THAT WE HAD RECEIVED LNDG CLRNC; AND THEN LOST COM WITH THEM. EVIDENTLY; THEY WERE CONCERNED THAT THE COMMUTER PLANE WAS ENCROACHING ON OUR RWY; AND THEY; (THE TWR) HAD ISSUED US A CLRNC TO 'GAR;' WHICH WE NEVER RECEIVED. I VERIFIED FOR THE TWR SUPVR THAT THE OTHER ACFT HAD BEEN TO OUR R AND CLR OF OUR PATH AND RWY.