CLRNC LNDG MAY NOT HAVE BEEN RECEIVED BY COMMUTER FO. MULTIPLE RWY OP PARALLEL RWYS. SIMULTANEOUS PARALLEL APCHS IN PROGRESS.

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WE WERE ON R DOWNWIND FOR RWY 28R. WE WERE TOLD THAT WE WERE #5 FOR THE ILS. A LITTLE LATER WE WERE TURNED TOWARDS THE RWY AND CLRED FROM 6000 FT TO 3000 FT. IT SEEMED THE SEQUENCE FOR LNDG HAD CHANGED AND; THOUGH I AM NOT SURE; SOME OF THE ACFT IN FRONT OF US WERE SWITCHED TO RWY 28L. AS WE DSNDED IN THE TURN I NOTICED THE VERT SPD INDICATOR ON THE PRESSURIZATION SYS CHANGE ABNORMALLY HIGH -- RATE OF 1500 FPM. I MENTIONED IT TO THE CAPT; WE DETERMINED IT NOT TO BE CRITICAL AND I CONTINUED TO MONITOR IT. OUR SPD HAD BEEN REDUCED BY ATC FROM AN INITIAL RESTR OF 160 KTS TO 150 KTS; A VISUAL CLRNC TO RWY 28R WAS ISSUED AND ACCEPTED; AND A CHANGE TO TWR FREQ. I CHKED IN WITH TWR. MEANWHILE; I WAS CONTINUING TO MONITOR THE PRESSURIZATION. I COMPLETED THE BEFORE LNDG CHKS; MADE THE STANDARD CALLOUTS AND WE LANDED. AS WE TOUCHED DOWN I HAD DOUBTS ABOUT US HAVING RECEIVED A LNDG CLRNC. THE RWY HAD BEEN CLR AND I DON'T RECOLLECT SEEING ANYBODY HOLD SHORT. ON CLRING THE RWY I ASKED THE TWR FOR FREQ CHANGE WHICH HE GAVE WITHOUT FURTHER COMMENT. THE CAPT FELT WE HAD RECEIVED LNDG CLRNC BUT COULDN'T REMEMBER WHEN. I AM NEVER AMBIGUOUS ABOUT LNDG CLRNCS THUS MY FILING THIS RPT. I DID ALLOW MYSELF TO GET TOO ABSORBED WITH THE PRESSURIZATION. IF WE WEREN'T CLRED TO LAND THEN THE TWR (WHO WAS NO LONGER BUSY) SEEMED AS OBLIVIOUS TO IT AS THE CAPT WAS. BECAUSE I'M UNSURE OF ANYTHING HAVING GONE WRONG IT'S DIFFICULT TO SAY WHETHER THERE WAS ANY PROB TO HAVE DISCOVERED. IF THERE WAS ONE THEN THE CONTRIBUTING FACTORS WERE: ATC'S SUDDEN CHANGE OF OUR SEQUENCE. MY DISTR WITH THE PRESSURIZATION. WE HAD COME OFF A REDUCED REST OVERNIGHT AND THE CAPT IN PARTICULAR HAD REMARKED HOW TIRED HE WAS. USUALLY THE TWR FREQ IS VERY BUSY AND IT SEEMS TO HEIGHTEN ONE'S AWARENESS. WHEN WE WERE HANDED OVER TO TWR IT WASN'T BUSY AT ALL. AS MENTIONED EARLIER; I AM NORMALLY VERY THOROUGH ABOUT CLRNCS. I ALWAYS DOUBLE-CHK IF I'M NOT SURE. THIS TIME IT CROSSED MY MIND WHEN WE TOUCHED THE GND. IN FUTURE; A RED FLAG WILL FLY ANY TIME DISTRS OCCUR DURING NORMAL OR OTHER PROCS.