Narrative:

Took over aircraft in phx. Aircraft was on an MEL relief for inoperative #4 leading edge slat indicator, according to the release. We did not realize that the actual malfunction was an inoperative #4 leading edge flap indicator, which is right next to the #4 leading edge slat indicator, until we were en route to our second destination of mdw. At mdw we had maintenance repair the problem. This chain started the previous day when hou maintenance improperly MEL'ed the aircraft. 3 other crews had flown the aircraft before us, which lulled us into a false sense of security that the aircraft was ok to fly. The MEL is somewhat poorly written on this topic and easily confused. The fact that the #4 leading edge slat and #4 leading edge flap indicators are right next to each other adds to the confusion. The corrective actions could be: number each B737 leading edge device separately, so they can't be confused. Re-write the MEL to specifically state that it applies to the leading edge slats only, and not to the leading edge flaps.

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Original NASA ASRS Text

Title: THE ACR FLC OF A B737-300 DISCOVERS, BELATEDLY, THAT AN MEL ITEM WAS IMPROPERLY ENTERED INTO THE LOGBOOK. THE #4 LEADING EDGE SLAT WAS SHOWN AS INOP WHEN IT WAS ACTUALLY THE #4 LEADING EDGE FLAP THAT WAS INOP.

Narrative: TOOK OVER ACFT IN PHX. ACFT WAS ON AN MEL RELIEF FOR INOP #4 LEADING EDGE SLAT INDICATOR, ACCORDING TO THE RELEASE. WE DID NOT REALIZE THAT THE ACTUAL MALFUNCTION WAS AN INOP #4 LEADING EDGE FLAP INDICATOR, WHICH IS RIGHT NEXT TO THE #4 LEADING EDGE SLAT INDICATOR, UNTIL WE WERE ENRTE TO OUR SECOND DEST OF MDW. AT MDW WE HAD MAINT REPAIR THE PROB. THIS CHAIN STARTED THE PREVIOUS DAY WHEN HOU MAINT IMPROPERLY MEL'ED THE ACFT. 3 OTHER CREWS HAD FLOWN THE ACFT BEFORE US, WHICH LULLED US INTO A FALSE SENSE OF SECURITY THAT THE ACFT WAS OK TO FLY. THE MEL IS SOMEWHAT POORLY WRITTEN ON THIS TOPIC AND EASILY CONFUSED. THE FACT THAT THE #4 LEADING EDGE SLAT AND #4 LEADING EDGE FLAP INDICATORS ARE RIGHT NEXT TO EACH OTHER ADDS TO THE CONFUSION. THE CORRECTIVE ACTIONS COULD BE: NUMBER EACH B737 LEADING EDGE DEVICE SEPARATELY, SO THEY CAN'T BE CONFUSED. RE-WRITE THE MEL TO SPECIFICALLY STATE THAT IT APPLIES TO THE LEADING EDGE SLATS ONLY, AND NOT TO THE LEADING EDGE FLAPS.

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.