Narrative:

Arrival into dtw and planning to fly visual approach to runway 21L (backed up by ILS); established at 5000 ft MSL; base leg. Captain flying and monitoring dtw (positional awareness) prior to selecting localizer frequency; first officer -- in an effort to provide DME -- selects dtw. Problem occurs because approach DME is based on crl VOR. I should have confirmed proper NAVAID selection with first officer. Rollout on extended final approximately 20 mi dtw/32 mi crl. Operations normal until I depart 5000 ft approximately 2 mi early (believing we've reached robbi/25.2 crl) for next restr. Decision based on dtw DME. At the same time; first officer notes that I've descended early. I see that first officer is monitoring dtw and xchk FMC and determine I have descended early. I break our descent rate and would have called approach but we were in midst of frequency change to tower. At this point; we cross robbi (don't recall exact altitude) and then continue descent to 4000 ft. Continue approach to uneventful landing. On taxi-in; ground notifies us of a problem on final approach and instructs us to contact TRACON. Speak with TRACON supervisor. Explained my error and he concurred. He stated that he would research problem to see if there was a conflict with other traffic. He returned a call approximately 45 mins later that there was a conflict and that he would be filing paperwork. On final; we did not perceive (visually/TCAS) any traffic in our immediate area. First; I should have highlighted DME reference when briefing the visual approach and confirmed what NAVAID setup would be. My normal habit is to monitor VOR at the field to remain positionally aware. I should have emphasized that in approach briefing and that the field VOR is not the DME reference for the approach. Secondly; better xchk of FMC legs page on my part would have helped my situational awareness. I was referencing DME more than legs page. Thirdly; verbalizing when I planned to depart 5000 ft would have alerted first officer that something was in error. One item for ATC -- we were switched to tower pretty early (approximately 18 mi). Maybe that's a function of controller workload; but if there is a traffic conflict; believe approach would be better equipped to provide a warning call. Overall; this was an incident that could have been prevented by a better briefing; more disciplined monitoring and coordination on my part.

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Original NASA ASRS Text

Title: B737-300 FLT CREW VIOLATED THE CROSSING RESTRICTION ON A VISUAL APCH; FAILING TO REFERENCE THE VOR AS A DME REFERENCE FOR IDENTIFYING THE FIX.

Narrative: ARR INTO DTW AND PLANNING TO FLY VISUAL APCH TO RWY 21L (BACKED UP BY ILS); ESTABLISHED AT 5000 FT MSL; BASE LEG. CAPT FLYING AND MONITORING DTW (POSITIONAL AWARENESS) PRIOR TO SELECTING LOC FREQ; FO -- IN AN EFFORT TO PROVIDE DME -- SELECTS DTW. PROB OCCURS BECAUSE APCH DME IS BASED ON CRL VOR. I SHOULD HAVE CONFIRMED PROPER NAVAID SELECTION WITH FO. ROLLOUT ON EXTENDED FINAL APPROX 20 MI DTW/32 MI CRL. OPS NORMAL UNTIL I DEPART 5000 FT APPROX 2 MI EARLY (BELIEVING WE'VE REACHED ROBBI/25.2 CRL) FOR NEXT RESTR. DECISION BASED ON DTW DME. AT THE SAME TIME; FO NOTES THAT I'VE DSNDED EARLY. I SEE THAT FO IS MONITORING DTW AND XCHK FMC AND DETERMINE I HAVE DSNDED EARLY. I BREAK OUR DSCNT RATE AND WOULD HAVE CALLED APCH BUT WE WERE IN MIDST OF FREQ CHANGE TO TWR. AT THIS POINT; WE CROSS ROBBI (DON'T RECALL EXACT ALT) AND THEN CONTINUE DSCNT TO 4000 FT. CONTINUE APCH TO UNEVENTFUL LNDG. ON TAXI-IN; GND NOTIFIES US OF A PROB ON FINAL APCH AND INSTRUCTS US TO CONTACT TRACON. SPEAK WITH TRACON SUPVR. EXPLAINED MY ERROR AND HE CONCURRED. HE STATED THAT HE WOULD RESEARCH PROB TO SEE IF THERE WAS A CONFLICT WITH OTHER TFC. HE RETURNED A CALL APPROX 45 MINS LATER THAT THERE WAS A CONFLICT AND THAT HE WOULD BE FILING PAPERWORK. ON FINAL; WE DID NOT PERCEIVE (VISUALLY/TCAS) ANY TFC IN OUR IMMEDIATE AREA. FIRST; I SHOULD HAVE HIGHLIGHTED DME REF WHEN BRIEFING THE VISUAL APCH AND CONFIRMED WHAT NAVAID SETUP WOULD BE. MY NORMAL HABIT IS TO MONITOR VOR AT THE FIELD TO REMAIN POSITIONALLY AWARE. I SHOULD HAVE EMPHASIZED THAT IN APCH BRIEFING AND THAT THE FIELD VOR IS NOT THE DME REF FOR THE APCH. SECONDLY; BETTER XCHK OF FMC LEGS PAGE ON MY PART WOULD HAVE HELPED MY SITUATIONAL AWARENESS. I WAS REFING DME MORE THAN LEGS PAGE. THIRDLY; VERBALIZING WHEN I PLANNED TO DEPART 5000 FT WOULD HAVE ALERTED FO THAT SOMETHING WAS IN ERROR. ONE ITEM FOR ATC -- WE WERE SWITCHED TO TWR PRETTY EARLY (APPROX 18 MI). MAYBE THAT'S A FUNCTION OF CTLR WORKLOAD; BUT IF THERE IS A TFC CONFLICT; BELIEVE APCH WOULD BE BETTER EQUIPPED TO PROVIDE A WARNING CALL. OVERALL; THIS WAS AN INCIDENT THAT COULD HAVE BEEN PREVENTED BY A BETTER BRIEFING; MORE DISCIPLINED MONITORING AND COORD ON MY PART.

Data retrieved from NASA's ASRS site as of May 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.