Narrative:

To start with 2 capts were assigned duty for flight number (hot-hro-bpk-stl). Even though a captain is qualified to fly from both seats, neither I nor the other captain has very much experience in the right seat. The decision was made that since it had been such a long time since we had sat and operated the aircraft from the right seat we would switch seats in stl. I took first turn in the left and was the PF on all 3 legs while the other captain did the first officer duties and acted as PNF which meant he would operate the radios for all 3 legs. Upon switching to stl approach we were carrying over an altitude of 10000 ft MSL from center. Stl gave us some airspeed reductions and then had given us a slow to 170 KTS then descend to 8000 ft MSL. This clearance both of us still agree upon. Somehow we accepted (or) expected a clearance to 7000 ft MSL. Neither of us remember accepting a 7000 ft clearance but our altitude alerter was dialed in to 7000 ft. Neither of us remember accepting a 7000 ft clearance, but our altitude alerter was dialed to 7000 ft. Neither of us remember dialing it in. As I have a habit of doing I set the reminders for airspeed, heading, and altitude and then fly by the reminders. Therefore, as I was descending from 10000 ft, I ended up descending through 8000 ft. As we were descending through 7100 ft we were asked our altitude. PNF stated 'leveling at 7000 ft.' we were then advised we were cleared only to 8000 ft and we had conflicting traffic 2 mi away at 7000 ft. We immediately went to full power and climbed to 8000 ft.

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Original NASA ASRS Text

Title: FLC OF ACR LTT ACFT OVERSHOT DSCNT ALT CLRNC LIMIT DUE TO THE WRONG SETTING OF THE ALT ALERTER.

Narrative: TO START WITH 2 CAPTS WERE ASSIGNED DUTY FOR FLT NUMBER (HOT-HRO-BPK-STL). EVEN THOUGH A CAPT IS QUALIFIED TO FLY FROM BOTH SEATS, NEITHER I NOR THE OTHER CAPT HAS VERY MUCH EXPERIENCE IN THE R SEAT. THE DECISION WAS MADE THAT SINCE IT HAD BEEN SUCH A LONG TIME SINCE WE HAD SAT AND OPERATED THE ACFT FROM THE R SEAT WE WOULD SWITCH SEATS IN STL. I TOOK FIRST TURN IN THE L AND WAS THE PF ON ALL 3 LEGS WHILE THE OTHER CAPT DID THE FO DUTIES AND ACTED AS PNF WHICH MEANT HE WOULD OPERATE THE RADIOS FOR ALL 3 LEGS. UPON SWITCHING TO STL APCH WE WERE CARRYING OVER AN ALT OF 10000 FT MSL FROM CTR. STL GAVE US SOME AIRSPD REDUCTIONS AND THEN HAD GIVEN US A SLOW TO 170 KTS THEN DSND TO 8000 FT MSL. THIS CLRNC BOTH OF US STILL AGREE UPON. SOMEHOW WE ACCEPTED (OR) EXPECTED A CLRNC TO 7000 FT MSL. NEITHER OF US REMEMBER ACCEPTING A 7000 FT CLRNC BUT OUR ALT ALERTER WAS DIALED IN TO 7000 FT. NEITHER OF US REMEMBER ACCEPTING A 7000 FT CLRNC, BUT OUR ALT ALERTER WAS DIALED TO 7000 FT. NEITHER OF US REMEMBER DIALING IT IN. AS I HAVE A HABIT OF DOING I SET THE REMINDERS FOR AIRSPD, HDG, AND ALT AND THEN FLY BY THE REMINDERS. THEREFORE, AS I WAS DSNDING FROM 10000 FT, I ENDED UP DSNDING THROUGH 8000 FT. AS WE WERE DSNDING THROUGH 7100 FT WE WERE ASKED OUR ALT. PNF STATED 'LEVELING AT 7000 FT.' WE WERE THEN ADVISED WE WERE CLRED ONLY TO 8000 FT AND WE HAD CONFLICTING TFC 2 MI AWAY AT 7000 FT. WE IMMEDIATELY WENT TO FULL PWR AND CLBED TO 8000 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.