Narrative:

On approach to mdw; we were cleared to 'maintain 4000 ft until gleam; cleared for the ILS 31C circle 22L.' I continued in navigation mode and initiated a profile descent to 2300 ft; which was the altitude at which I was going to circle; rather than arming approach -- land; from which I would have to manually stop the descent while on the GS. The aircraft began to descend; and the captain noted that; over gleam; we were approximately 3600 ft. We re-intercepted the correct profile over runts and completed the approach. ATC never mentioned the deviation. The mdw ATIS is extremely weak; so we were unable to obtain the approach in use until only around 75 mi from the field. The approach in use was advertised as 'visual 22L;' even though from past experience; in this confign we could have expected ILS runway 31C circle runway 22L. I briefed the RNAV runway 22L as a backup for the visual. Once on frequency with chicago approach; we were told to proceed direct gleam and to expect the ILS runway 31L circle runway 22L. The captain quickly entered direct gleam in the FMS; and then strung the approach. We then xferred controls and I quickly briefed the approach. While stringing the approach; we did not enter any transition because we were directly intercepting final. In this scenario; gleam does not show up on the approach. We therefore manually removed the discontinuity between gleam (where we were proceeding) and runts. This showed the correct waypoints for the approach; but the minimum altitude at gleam (4000 ft) was not entered. I didn't notice that this altitude wasn't strung. I didn't listen fully to the approach clearance because of task saturation. When I didn't hear the approach clearance; I didn't ask to review it with the captain. He didn't notice the profile descent took us below 4000 ft until we were 400 ft low. Both of our mistakes; and lack of communication led to this deviation. We both knew the airport; and that the approach we heard on the ATIS was atypical for the conditions. We should have prepared for what we really expected. When building an approach from scratch; extra care should be taken to make sure it agrees with what is on the plate. Finally; rushing an approach briefing; especially when executing an unusual approach like this; should always raise a red flag.

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Original NASA ASRS Text

Title: UNEXPECTED LATE CHANGE FROM ATIS ADVERTISED VISUAL APCH RWY 22 TO AN ILS RWY 31C; CIRCLE TO LAND RWY 22 RESULTS IN BREAKDOWN IN CRM; SITUATIONAL AWARENESS AND; ULTIMATELY; BUSTING AN ALT RESTRICTION ON THE ARRIVAL.

Narrative: ON APCH TO MDW; WE WERE CLRED TO 'MAINTAIN 4000 FT UNTIL GLEAM; CLRED FOR THE ILS 31C CIRCLE 22L.' I CONTINUED IN NAV MODE AND INITIATED A PROFILE DSCNT TO 2300 FT; WHICH WAS THE ALT AT WHICH I WAS GOING TO CIRCLE; RATHER THAN ARMING APCH -- LAND; FROM WHICH I WOULD HAVE TO MANUALLY STOP THE DSCNT WHILE ON THE GS. THE ACFT BEGAN TO DSND; AND THE CAPT NOTED THAT; OVER GLEAM; WE WERE APPROX 3600 FT. WE RE-INTERCEPTED THE CORRECT PROFILE OVER RUNTS AND COMPLETED THE APCH. ATC NEVER MENTIONED THE DEV. THE MDW ATIS IS EXTREMELY WEAK; SO WE WERE UNABLE TO OBTAIN THE APCH IN USE UNTIL ONLY AROUND 75 MI FROM THE FIELD. THE APCH IN USE WAS ADVERTISED AS 'VISUAL 22L;' EVEN THOUGH FROM PAST EXPERIENCE; IN THIS CONFIGN WE COULD HAVE EXPECTED ILS RWY 31C CIRCLE RWY 22L. I BRIEFED THE RNAV RWY 22L AS A BACKUP FOR THE VISUAL. ONCE ON FREQ WITH CHICAGO APCH; WE WERE TOLD TO PROCEED DIRECT GLEAM AND TO EXPECT THE ILS RWY 31L CIRCLE RWY 22L. THE CAPT QUICKLY ENTERED DIRECT GLEAM IN THE FMS; AND THEN STRUNG THE APCH. WE THEN XFERRED CTLS AND I QUICKLY BRIEFED THE APCH. WHILE STRINGING THE APCH; WE DID NOT ENTER ANY TRANSITION BECAUSE WE WERE DIRECTLY INTERCEPTING FINAL. IN THIS SCENARIO; GLEAM DOES NOT SHOW UP ON THE APCH. WE THEREFORE MANUALLY REMOVED THE DISCONTINUITY BTWN GLEAM (WHERE WE WERE PROCEEDING) AND RUNTS. THIS SHOWED THE CORRECT WAYPOINTS FOR THE APCH; BUT THE MINIMUM ALT AT GLEAM (4000 FT) WAS NOT ENTERED. I DIDN'T NOTICE THAT THIS ALT WASN'T STRUNG. I DIDN'T LISTEN FULLY TO THE APCH CLRNC BECAUSE OF TASK SATURATION. WHEN I DIDN'T HEAR THE APCH CLRNC; I DIDN'T ASK TO REVIEW IT WITH THE CAPT. HE DIDN'T NOTICE THE PROFILE DSCNT TOOK US BELOW 4000 FT UNTIL WE WERE 400 FT LOW. BOTH OF OUR MISTAKES; AND LACK OF COM LED TO THIS DEV. WE BOTH KNEW THE ARPT; AND THAT THE APCH WE HEARD ON THE ATIS WAS ATYPICAL FOR THE CONDITIONS. WE SHOULD HAVE PREPARED FOR WHAT WE REALLY EXPECTED. WHEN BUILDING AN APCH FROM SCRATCH; EXTRA CARE SHOULD BE TAKEN TO MAKE SURE IT AGREES WITH WHAT IS ON THE PLATE. FINALLY; RUSHING AN APCH BRIEFING; ESPECIALLY WHEN EXECUTING AN UNUSUAL APCH LIKE THIS; SHOULD ALWAYS RAISE A RED FLAG.

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.