Narrative:

Local altimeter setting was 30.42. My altimeter and standby were set to 30.42. The captain inadvertently set 29.42. He was the PF; and the fcp/FD was selected to his side. We were cleared to 4000 ft; and the aircraft on autoplt continued to descend to 3000 ft (4000 ft on the captain's display). Before we realized this error; we had descended 1000 ft below our clearance. His display showed us at 4000 ft; and mine indicated 3000 ft. As soon as I recognized this incongruence; I queried ATC's local altimeter setting. They said '30.42 and you can remain at 3000.' I apologized; and ATC responded that it wasn't a problem. The captain was noticeably worn out from many days and months of heavy reserve duty. I flew with him a yr ago; and he was a much different captain then. He used to be very alert and responsible. A yr later; he is still on reserve with maximum flying; minimum rest; and minimum days off. He is almost to the point of disaffection when it comes to his job. This is a common problem at my airline. We are stretched to the maximum flying allowed by the far's on a daily; weekly; and monthly basis; then we are regularly reduced to absolute minimum rest and days off (frequently reduced to 8 hours rest; and regularly flying 6 days on and 1 off). We are too short staffed and our schedules are too demanding to allow for adequate rest and maximum performance. I believe fatigue; in general; was a main factor contributing to the aforementioned incident. Also; I should have been more aware and fastidious of the situation before we descended as far as we did. I scan frequently as the PNF; but I did not expect the captain to make such an easy; yet possibly deadly; mistake.

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Original NASA ASRS Text

Title: FLT CREW SCHEDULING PRACTICES AND FATIGUE CONTRIBUTE TO MISSET ALTIMETER AND ALTDEV FOR CARJ.

Narrative: LCL ALTIMETER SETTING WAS 30.42. MY ALTIMETER AND STANDBY WERE SET TO 30.42. THE CAPT INADVERTENTLY SET 29.42. HE WAS THE PF; AND THE FCP/FD WAS SELECTED TO HIS SIDE. WE WERE CLRED TO 4000 FT; AND THE ACFT ON AUTOPLT CONTINUED TO DSND TO 3000 FT (4000 FT ON THE CAPT'S DISPLAY). BEFORE WE REALIZED THIS ERROR; WE HAD DSNDED 1000 FT BELOW OUR CLRNC. HIS DISPLAY SHOWED US AT 4000 FT; AND MINE INDICATED 3000 FT. AS SOON AS I RECOGNIZED THIS INCONGRUENCE; I QUERIED ATC'S LCL ALTIMETER SETTING. THEY SAID '30.42 AND YOU CAN REMAIN AT 3000.' I APOLOGIZED; AND ATC RESPONDED THAT IT WASN'T A PROB. THE CAPT WAS NOTICEABLY WORN OUT FROM MANY DAYS AND MONTHS OF HVY RESERVE DUTY. I FLEW WITH HIM A YR AGO; AND HE WAS A MUCH DIFFERENT CAPT THEN. HE USED TO BE VERY ALERT AND RESPONSIBLE. A YR LATER; HE IS STILL ON RESERVE WITH MAX FLYING; MINIMUM REST; AND MINIMUM DAYS OFF. HE IS ALMOST TO THE POINT OF DISAFFECTION WHEN IT COMES TO HIS JOB. THIS IS A COMMON PROB AT MY AIRLINE. WE ARE STRETCHED TO THE MAX FLYING ALLOWED BY THE FAR'S ON A DAILY; WEEKLY; AND MONTHLY BASIS; THEN WE ARE REGULARLY REDUCED TO ABSOLUTE MINIMUM REST AND DAYS OFF (FREQUENTLY REDUCED TO 8 HRS REST; AND REGULARLY FLYING 6 DAYS ON AND 1 OFF). WE ARE TOO SHORT STAFFED AND OUR SCHEDULES ARE TOO DEMANDING TO ALLOW FOR ADEQUATE REST AND MAX PERFORMANCE. I BELIEVE FATIGUE; IN GENERAL; WAS A MAIN FACTOR CONTRIBUTING TO THE AFOREMENTIONED INCIDENT. ALSO; I SHOULD HAVE BEEN MORE AWARE AND FASTIDIOUS OF THE SITUATION BEFORE WE DSNDED AS FAR AS WE DID. I SCAN FREQUENTLY AS THE PNF; BUT I DID NOT EXPECT THE CAPT TO MAKE SUCH AN EASY; YET POSSIBLY DEADLY; MISTAKE.

Data retrieved from NASA's ASRS site as of January 2009 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.