Narrative:

We were cleared for the localizer back course runway to clt. The approach specifies 4000 ft until atell intersection then down to 2700 ft until lecar. We were using the LNAV portion of the FMC, I was flying when back course was intercepted. I was looking at FMC. It said approximately 6.0 DME to clear, (the FMC did not show atell in prior to lecar) so I started my descent to 2700 ft. The captain then decided to put the clt VOR/DME on his side which showed we were still approximately 1 mi outside of atell. At this point I was approximately descending through 3700 ft and stopped my descent once I realized that we had in fact not passed atell. Upon reaching atell I then proceeded down to 2700 ft MSL which is the minimum altitude specified until passing lecar. No evasive action was taken. We did not get any GPWS, no low altitude alert nor was any comment made by clt approach control. The only other peculiarity was the captain had tried 2-3 times to contact clt tower, and it wasn't until about the 3RD transmission that clt tower answered. Clt tower then cleared us to land on runway 23. To prevent an occurrence of this nature from happening in the future, when utilizing the LNAV portion of the FMC, 1 pilot (PNF) should be on 'raw data,' clt VOR as a xchk. The captain was 'late' in putting in the clt VOR/DME had it been put in prior to executing the approach, we would have had a viable backup DME to xchk with.

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Original NASA ASRS Text

Title: ACR DSNDS BEFORE REACHING PROPER INTXN ON BC APCH.

Narrative: WE WERE CLRED FOR THE LOC BACK COURSE RWY TO CLT. THE APCH SPECIFIES 4000 FT UNTIL ATELL INTXN THEN DOWN TO 2700 FT UNTIL LECAR. WE WERE USING THE LNAV PORTION OF THE FMC, I WAS FLYING WHEN BACK COURSE WAS INTERCEPTED. I WAS LOOKING AT FMC. IT SAID APPROX 6.0 DME TO CLR, (THE FMC DID NOT SHOW ATELL IN PRIOR TO LECAR) SO I STARTED MY DSCNT TO 2700 FT. THE CAPT THEN DECIDED TO PUT THE CLT VOR/DME ON HIS SIDE WHICH SHOWED WE WERE STILL APPROX 1 MI OUTSIDE OF ATELL. AT THIS POINT I WAS APPROX DSNDING THROUGH 3700 FT AND STOPPED MY DSCNT ONCE I REALIZED THAT WE HAD IN FACT NOT PASSED ATELL. UPON REACHING ATELL I THEN PROCEEDED DOWN TO 2700 FT MSL WHICH IS THE MINIMUM ALT SPECIFIED UNTIL PASSING LECAR. NO EVASIVE ACTION WAS TAKEN. WE DID NOT GET ANY GPWS, NO LOW ALT ALERT NOR WAS ANY COMMENT MADE BY CLT APCH CTL. THE ONLY OTHER PECULIARITY WAS THE CAPT HAD TRIED 2-3 TIMES TO CONTACT CLT TWR, AND IT WASN'T UNTIL ABOUT THE 3RD XMISSION THAT CLT TWR ANSWERED. CLT TWR THEN CLRED US TO LAND ON RWY 23. TO PREVENT AN OCCURRENCE OF THIS NATURE FROM HAPPENING IN THE FUTURE, WHEN UTILIZING THE LNAV PORTION OF THE FMC, 1 PLT (PNF) SHOULD BE ON 'RAW DATA,' CLT VOR AS A XCHK. THE CAPT WAS 'LATE' IN PUTTING IN THE CLT VOR/DME HAD IT BEEN PUT IN PRIOR TO EXECUTING THE APCH, WE WOULD HAVE HAD A VIABLE BACKUP DME TO XCHK WITH.

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.