Narrative:

Departing field altimeter was 29.43. I was the PNF. On climb out, company procedure is to make an announcement leaving 10000 ft to let the flight attendants know it's safe to get up and start their duties. I usually add our ETA to this announcement for the passenger. This flight I forgot to do this, and remembered it about 16000 ft. Since we were only climbing to FL230 I decided to do the 'out of 10' announcement and the 'cruise announcement' at the same time. So I started gathering information for the passenger speech by requesting destination WX on the ACARS. During this time, we climbed through 18000 ft and the captain said '29.92,' at the same time I saw him reach for his altimeter out of my peripheral vision and reset his altimeter. I looked up from what I was doing and said '29.92' and reset my own altimeter as well. I then went back to my speech preparation and did not monitor the level off, as I should have done! It was light chop in the climb and shortly after reaching cruise, the light chop turned to moderate turbulence. At this time, the captain initiated a call to center and asked for a lower altitude to find smoother air. We had been at cruise about 3 or 4 mins or so. ATC came back and said, 'I show you at FL240.' we looked and the captain's altimeter said 23000 ft, but he had inadvertently set it to 28.92. My altimeter said 24000 ft, set on 29.92. The mode control panel (MCP) altitude window was correctly set for 23000 ft. The #1 autoplt, which gets its altitude information from the captain's altimeter, took the aircraft to 23000 ft as determined by his altimeter, which was really 24000 ft on a setting of 29.92. The captain replied something to the effect of 'yes, requesting lower,' while he dialed in the correct altimeter setting. ATC immediately cleared us to a lower altitude, and nothing more was said. In retrospect, I think the controller did not catch our error until we called him for a descent. Lots of things contributed to this incident: the unusually low altimeter setting that day. My not double-checking the captain's altimeter setting as we passed 18000 ft. My not monitoring the leveloff at cruise altitude. The controller's error for whatever reason in not catching our error. Luckily, this chain of a series of small mistakes was broken by an unrelated event (turbulence) before something catastrophic happened. I learned an inexpensive lesson about my complacency, without even realizing I had it until this event rattled my cage. Obviously, I vowed to: check all 3 altimeters for the correct altimeter setting climbing and descending through 18000 ft. Monitor all level offs, (as I usually did, I thought). Forego all busy work until level off at cruise altitude. One afterthought: when I first looked at my altimeter after being alerted by the controller, it actually read something like 23950 ft. The numbers 23 were in view, but the 950 were sort of floating halfway between 950 and 000. An instant of confusion ensued in my mind as to whether we were at 23000 ft or 24000 ft.

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Original NASA ASRS Text

Title: FLT CREW OF AIR CARRIER ACFT EXPERIENCE ALT OVERSHOOT IN CLB DUE TO FAILURE TO RESET ALTIMETERS CORRECTLY PASSING FL180.

Narrative: DEPARTING FIELD ALTIMETER WAS 29.43. I WAS THE PNF. ON CLBOUT, COMPANY PROC IS TO MAKE AN ANNOUNCEMENT LEAVING 10000 FT TO LET THE FLT ATTENDANTS KNOW IT'S SAFE TO GET UP AND START THEIR DUTIES. I USUALLY ADD OUR ETA TO THIS ANNOUNCEMENT FOR THE PAX. THIS FLT I FORGOT TO DO THIS, AND REMEMBERED IT ABOUT 16000 FT. SINCE WE WERE ONLY CLBING TO FL230 I DECIDED TO DO THE 'OUT OF 10' ANNOUNCEMENT AND THE 'CRUISE ANNOUNCEMENT' AT THE SAME TIME. SO I STARTED GATHERING INFO FOR THE PAX SPEECH BY REQUESTING DEST WX ON THE ACARS. DURING THIS TIME, WE CLBED THROUGH 18000 FT AND THE CAPT SAID '29.92,' AT THE SAME TIME I SAW HIM REACH FOR HIS ALTIMETER OUT OF MY PERIPHERAL VISION AND RESET HIS ALTIMETER. I LOOKED UP FROM WHAT I WAS DOING AND SAID '29.92' AND RESET MY OWN ALTIMETER AS WELL. I THEN WENT BACK TO MY SPEECH PREPARATION AND DID NOT MONITOR THE LEVEL OFF, AS I SHOULD HAVE DONE! IT WAS LIGHT CHOP IN THE CLB AND SHORTLY AFTER REACHING CRUISE, THE LIGHT CHOP TURNED TO MODERATE TURB. AT THIS TIME, THE CAPT INITIATED A CALL TO CTR AND ASKED FOR A LOWER ALT TO FIND SMOOTHER AIR. WE HAD BEEN AT CRUISE ABOUT 3 OR 4 MINS OR SO. ATC CAME BACK AND SAID, 'I SHOW YOU AT FL240.' WE LOOKED AND THE CAPT'S ALTIMETER SAID 23000 FT, BUT HE HAD INADVERTENTLY SET IT TO 28.92. MY ALTIMETER SAID 24000 FT, SET ON 29.92. THE MODE CTL PANEL (MCP) ALT WINDOW WAS CORRECTLY SET FOR 23000 FT. THE #1 AUTOPLT, WHICH GETS ITS ALT INFO FROM THE CAPT'S ALTIMETER, TOOK THE ACFT TO 23000 FT AS DETERMINED BY HIS ALTIMETER, WHICH WAS REALLY 24000 FT ON A SETTING OF 29.92. THE CAPT REPLIED SOMETHING TO THE EFFECT OF 'YES, REQUESTING LOWER,' WHILE HE DIALED IN THE CORRECT ALTIMETER SETTING. ATC IMMEDIATELY CLRED US TO A LOWER ALT, AND NOTHING MORE WAS SAID. IN RETROSPECT, I THINK THE CTLR DID NOT CATCH OUR ERROR UNTIL WE CALLED HIM FOR A DSCNT. LOTS OF THINGS CONTRIBUTED TO THIS INCIDENT: THE UNUSUALLY LOW ALTIMETER SETTING THAT DAY. MY NOT DOUBLE-CHKING THE CAPT'S ALTIMETER SETTING AS WE PASSED 18000 FT. MY NOT MONITORING THE LEVELOFF AT CRUISE ALT. THE CTLR'S ERROR FOR WHATEVER REASON IN NOT CATCHING OUR ERROR. LUCKILY, THIS CHAIN OF A SERIES OF SMALL MISTAKES WAS BROKEN BY AN UNRELATED EVENT (TURB) BEFORE SOMETHING CATASTROPHIC HAPPENED. I LEARNED AN INEXPENSIVE LESSON ABOUT MY COMPLACENCY, WITHOUT EVEN REALIZING I HAD IT UNTIL THIS EVENT RATTLED MY CAGE. OBVIOUSLY, I VOWED TO: CHK ALL 3 ALTIMETERS FOR THE CORRECT ALTIMETER SETTING CLBING AND DSNDING THROUGH 18000 FT. MONITOR ALL LEVEL OFFS, (AS I USUALLY DID, I THOUGHT). FOREGO ALL BUSY WORK UNTIL LEVEL OFF AT CRUISE ALT. ONE AFTERTHOUGHT: WHEN I FIRST LOOKED AT MY ALTIMETER AFTER BEING ALERTED BY THE CTLR, IT ACTUALLY READ SOMETHING LIKE 23950 FT. THE NUMBERS 23 WERE IN VIEW, BUT THE 950 WERE SORT OF FLOATING HALFWAY BTWN 950 AND 000. AN INSTANT OF CONFUSION ENSUED IN MY MIND AS TO WHETHER WE WERE AT 23000 FT OR 24000 FT.

Data retrieved from NASA's ASRS site as of July 2007 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.