Narrative:

We were cleared to 2000 ft by ord approach. As we went through about 8000, the engineer called out traffic ahead. I started looking for some, the engineer also gave us the altimeter settings at the same time. The copilot began setting his altimeter to QFE. Suddenly approach called and told us to level at 6000 for traffic. We had sailed right through 7000. The altitude alert did not warn us. I don't know for sure if we failed to arm it or it disarmed itself. Contributing factors here are many. Both pilots were tdy from a west coast base and unfamiliar (at least recently) with ord procedures. We were nearing the end of a duty day of 10 hours which started early on our body clock. The copilot was having trouble setting his altimeter. All these things combined so that no one was watching the store. I really don't know how to avoid these situations entirely. I just have to remind myself to be more aware and always make sure at least 1 pilot is paying attention to what the airplane is doing at all times. Supplemental information from acn 183405: I feel altimeter system is junk. At the time when all eyes are to be outside the cockpit they are in resetting the altimeters both on takeoff and landing. Another factor is that both the pilots are tdy. I speak for myself coming from sea level airports to chicago (667 ft) is very confusing with 3 altimeters. Also I'm another airline and have never used qnh QFE.

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Original NASA ASRS Text

Title: ALT DEV ON DSCNT.

Narrative: WE WERE CLRED TO 2000 FT BY ORD APCH. AS WE WENT THROUGH ABOUT 8000, THE ENGINEER CALLED OUT TFC AHEAD. I STARTED LOOKING FOR SOME, THE ENGINEER ALSO GAVE US THE ALTIMETER SETTINGS AT THE SAME TIME. THE COPLT BEGAN SETTING HIS ALTIMETER TO QFE. SUDDENLY APCH CALLED AND TOLD US TO LEVEL AT 6000 FOR TFC. WE HAD SAILED RIGHT THROUGH 7000. THE ALT ALERT DID NOT WARN US. I DON'T KNOW FOR SURE IF WE FAILED TO ARM IT OR IT DISARMED ITSELF. CONTRIBUTING FACTORS HERE ARE MANY. BOTH PLTS WERE TDY FROM A WEST COAST BASE AND UNFAMILIAR (AT LEAST RECENTLY) WITH ORD PROCS. WE WERE NEARING THE END OF A DUTY DAY OF 10 HRS WHICH STARTED EARLY ON OUR BODY CLOCK. THE COPLT WAS HAVING TROUBLE SETTING HIS ALTIMETER. ALL THESE THINGS COMBINED SO THAT NO ONE WAS WATCHING THE STORE. I REALLY DON'T KNOW HOW TO AVOID THESE SITUATIONS ENTIRELY. I JUST HAVE TO REMIND MYSELF TO BE MORE AWARE AND ALWAYS MAKE SURE AT LEAST 1 PLT IS PAYING ATTN TO WHAT THE AIRPLANE IS DOING AT ALL TIMES. SUPPLEMENTAL INFO FROM ACN 183405: I FEEL ALTIMETER SYSTEM IS JUNK. AT THE TIME WHEN ALL EYES ARE TO BE OUTSIDE THE COCKPIT THEY ARE IN RESETTING THE ALTIMETERS BOTH ON TKOF AND LNDG. ANOTHER FACTOR IS THAT BOTH THE PLTS ARE TDY. I SPEAK FOR MYSELF COMING FROM SEA LEVEL ARPTS TO CHICAGO (667 FT) IS VERY CONFUSING WITH 3 ALTIMETERS. ALSO I'M ANOTHER AIRLINE AND HAVE NEVER USED QNH QFE.

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.