LATE RECOGNITION BY CL65 FLT CREW TO CORRECT ALTIMETER SETTING DSNDING THROUGH FL180 CAUSES INTXN UNDERSHOOT WHEN ON APCH TO CVG.

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AFTER BEING LEVELED AT FL180; WE WERE GIVEN A CLRNC TO CROSS TIGRR INTXN AT 11000 FT ON THE CINCE 4 ARR TO CVG. WE LEVELED AT 11000 FT; PASSED TIGRR; AND WERE HANDED OFF TO CINCINNATI APCH. AFTER CHKING IN; I REALIZED WE HAD NOT SET OUR ALTIMETERS TO THE LCL SETTING. WE WERE STILL USING 29.92. WHEN SET CORRECTLY; OUR ALTIMETERS SHOWED US TO BE AT 11300 FT. I CORRECTED THE ERROR IMMEDIATELY. NOTHING WAS EVER SAID BY ANY CTLR. NO TFC CONFLICTS AROSE. THE CL65 INSTRUMENTATION SYS FLASHES THE ALTIMETER SETTING ON THE EFIS WHENEVER YOU GO THROUGH FL180. THIS IS USUALLY HELPFUL AS A REMINDER; BUT A BIT ANNOYING WHEN YOU CRUISE AT FL180. USUALLY; I LEAVE IT FLASHING WHEN WE DO AN INTERMEDIATE LEVELOFF AT FL180 DURING A DSCNT. THIS HELPS PREVENT MISTAKES LIKE WHAT I AM DESCRIBING. ON THIS NIGHT; HOWEVER; I EVIDENTLY PUSHED THE CTR OF THE BAROMETER KNOB TO CANCEL THE FLASHING. I DON'T REMEMBER DOING IT. IT WOULD HAVE BEEN HELPFUL IF WE WOULD HAVE RUN THE 'DSCNT' CHKLIST WHEN WE LEFT FL180; LIKE WE ARE SUPPOSED TO DO. THERE MAY HAVE BEEN SOME MINOR DISTR. I'M SURE ANOTHER FACTOR WAS THAT WE WERE BOTH TIRED. THIS WAS THE LAST LEG OF A 13+ HR DUTY DAY THAT HAD BEEN FULL OF WX AND DEICING DELAYS.