A COMMUTER FLC FAILED TO CONTACT THE TWR FOR A LNDG CLRNC. DURING A VISUAL APCH TO LNDG; A COMMUTER FLC RECEIVED A CLRNC TO FOLLOW TFC ON BASE TO FINAL APCH AND THE FLC FOLLOWED THE TFC AND LANDED WITHOUT A CLRNC.

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OCCURRENCE HAPPENED WHILE APCHING LGA ARPT FROM THE NE. THE STANDARD PROC INTO LGA AT THE TIME WAS THE EXPRESSWAY VISUAL TO RWY 31 WHICH NORMALLY FLOWS FROM THE VERRAZANO BRIDGE OVER THE MASPETH TANKS; FOLLOWS THE LONG ISLAND EXPRESSWAY TO SHEA STADIUM AND THEN MAKES A L BASE TO FINAL FOR RWY 31. (TFC PERMITTING; ATC WILL SPACE ACFT FROM THE NE TO MAKE A 'R TURN' INTO LGA.) AS PF (FO) WE WERE CLRED TO FOLLOW TFC MAKING BASE TO FINAL (BELIEVE IT WAS AN ACR DC9) TO RWY 31 AT LGA BY NY APCH. AT THE TIME OF THE INCIDENT; THE AUTOPLT WAS ON MEL AS INOP; WHICH ADDED TO THE WORKLOAD OF THE CREW. NO FURTHER XMISSION OR COMMANDS WERE GIVEN BY ATC. WE FOLLOWED OUR TFC; COMPLETED OUR CHKLIST AND LANDED. AFTER WE LANDED; WE WAITED FOR TWR TO GIVE US INSTRUCTIONS TO CONTACT GND. AT THAT TIME; WE NOTICED WE WERE STILL ON APCH FREQ. WE CONTACTED GND AND THEY ASKED US IF WE HEARD ANY OF THEIR XMISSIONS. WE EXPLAINED WE HAD NEVER SWITCHED OVER TO TWR FREQ. ATC STATED THAT WE SHOULD HAVE MISSED THE APCH IF WE NEVER RECEIVED A CLRNC TO LAND. NO 'NEAR MISS' OR 'RWY INCURSIONS' OCCURRED. ON THE PRIOR DAY; SAME ARR; SAME AIRPLANE; CREW; AND LNDG ON RWY 31 FROM THE NE; WE WERE SPACED TOO CLOSELY BTWN TWO ACFT CHALLENGERS. WE WERE INSTRUCTED 5 MI OUT TO FOLLOW A CHALLENGER ON A 1 MI FINAL. WE RPTED TFC AND FOLLOWED. WE NEVER POSITIVELY IDENTED THE PREVIOUS TFC AS A 'CHALLENGER.' AT APPROX 2 MI OUT WE NOTICED ANOTHER CHALLENGER AT OUR 9 O'CLOCK. ATC ASKED THE CHALLENGER IF HE HAD US IN SIGHT; BUT HE RPTED NEGATIVE. SECONDS LATER HE SAW US AND INCREASED HIS DISTANCE TO US BUT ATC DID NOT FEEL SPACING WAS ADEQUATE. ATC MADE THAT CHALLENGER MISS THE APCH AND GAR. THE FOLLOWING DAY WE WERE VERY CAUTIOUS TO WATCH FOR TFC WHICH MAY HAVE DISTRACTED OUR ATTN TO NOT CONTACT LGA TWR OR TO ASK APCH IF WE SHOULD CONTACT LGA TWR. AFTER THE INCIDENT WE CONTACTED LGA TWR BY PHONE; WHO MENTIONED THAT IT WAS NO PROB TO THEM; BUT THEY QUERIED US IF WE HAD HEARD THEM AND WE SAID NO. THEY ADVISED THAT SOMEONE HAD RESPONDED TO THEIR CALL; THAT THEY FURTHER WANTED US TO 'HOLD SHORT OF RWY 4' WHICH WE DID; UNAWARE OF THEM; OF COURSE.