FAILURE TO RESET ALTIMETER PASSING FL180.

Narrative

BOTH INCIDENTS INVOLVED ASSIGNED ALT DEVS OF GREATER THAN 300 FT WHILE BEING VECTORED FOR AN ILS APCH. THE FIRST DEV OCCURRED WHILE THE CAPT (A COMPANY CHK AIRMAN) WAS HAND FLYING THE AIRPLANE (WDB). WE WERE CLRED TO DSND AND MAINTAIN 6000 FT. AFTER I VERIFIED LEVEL AT 6000 FT; I LOOKED DOWN AT MY APCH PLATE TO IDENT THE LOC FREQ. WHEN I HEARD THE ALT ALERTER CHIME I SAW WE WERE DSNDING THROUGH 5700 FT. I RECHKED ALT DISPLAYED IN THE WINDOW TO VERIFY 6000 FT AND THEN SAID '...ALT; WHERE ARE YOU GOING?' THE CAPT CLBED BACK TO ALT. SEVERAL DAYS LATER ON THE SAME TRIP; THE CAPT WAS HAND FLYING THE AIRPLANE AND TRYING TO BRIEF THE APCH INTO ANC ARPT. AS WE HAD PASSED FL180 AND HAD NOT RESET THE ALTIMETERS; THE ALTIMETER SETTING OF 29.42 PUT US SEVERAL HUNDRED FT BELOW THE ASSIGNED ALT FO 13000 FT. I CALLED FOR THE CHKLIST AT 14000-15000 FT AS THE CAPT DID NOT AT FL180. BY THE TIME WE GOT TO THE ALTIMETER SETTING ITEM WE WERE ALREADY BELOW THE ALT. I DISCUSSED THIS WITH THE FE TO STRESS THE IMPORTANCE OF PROCEEDING WITH A CHKLIST AT THE APPROPRIATE TIME; EVEN IF ONE HAS NOT BEEN CALLED FOR. I PERSONALLY BELIEVE THAT BOTH INCIDENTS WERE DIRECTLY RELATED TO THE NORMAL AGE DETERIORATION OF THE CAPT AS HE WAS NEARING AGE 60. HE NEEDED ATC INSTRUCTIONS REPEATED TO HIM EVEN THOUGH HE WAS WEARING A HEADSET AND MISSED MANY THINGS SAID IN THE COCKPIT.