Narrative:

I was assigned the evening shift on the B-200/B-500 maintenance control desk. I received a call from a line mechanic requesting MEL xx (APU inoperative). Further discussion revealed that whenever the APU was operating (bleed on or bleed off); that the left wing body overheat light illuminated. He stated that there were no leaks in the system. Since it only happened when the APU was running we applied MEL xx; and aircraft departed on flight. The team lead (auditing the MEL run) and another controller questioned me about the MEL. I had applied the wrong MEL. At this time I contacted maintenance to reclassify the MEL to yy (wing body overheat system-left). This was accomplished in the logbook once the aircraft arrived. The aircraft had flown 2 flight legs with the wrong MEL applied. Aircraft was repaired that night; found loose connector D1390 and secured. This event was an error on my part. Thinking back I should have slowed down; carefully reviewed all applicable MEL's; and asked for assistance from the other controllers. Supplemental information from acn 744674: we took the airplane from the previous crew and everything was normal until the after engine start flow. During the after start flow; we noticed the left wing-body overheat light was illuminated. We ran the left wing-body overheat checklist through turning the APU switch off. After a few seconds; the light remained illuminated; so we informed maintenance and returned to the gate. I did not notice when the light went out. However; the mechanic entered the cockpit right after engine shutdown and noted the light was extinguished at that time. The mechanic told us he knew exactly what the problem was. Next; the captain contacted maintenance control and dispatch with the mechanic; and an MEL was issued for the APU. It seemed that all the proper people were in the loop and the MEL appeared routine to me. We flew the next 2 legs without using the APU; and all other operations were normal. The next day; the operations coordinator called the captain to inform him that there was a problem with the MEL and associated write-up. A second call to the operations coordinator confirmed that the MEL should have been issued for a wing-body overheat and not the APU. This was a learning experience for me. Besides learning which MEL should have applied in this particular case; I will double my efforts in the future to ensure an MEL properly matches the problem and caution lights in the cockpit. I will be especially vigilant to ensure an MEL closely matches the cockpit problem and indications. Additionally; I will continue to apply a healthy dose of skepticism to the write-ups in order to catch errors and omissions.

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Original NASA ASRS Text

Title: A B737-500 ACFT WAS DISPATCHED WITH IMPROPER MEL REFERENCE FOR A 'LEFT WING BODY OVERHEAT' LIGHT DURING 'AFTER ENGINE START FLOW' SEQUENCE.

Narrative: I WAS ASSIGNED THE EVENING SHIFT ON THE B-200/B-500 MAINT CTL DESK. I RECEIVED A CALL FROM A LINE MECH REQUESTING MEL XX (APU INOP). FURTHER DISCUSSION REVEALED THAT WHENEVER THE APU WAS OPERATING (BLEED ON OR BLEED OFF); THAT THE L WING BODY OVERHEAT LIGHT ILLUMINATED. HE STATED THAT THERE WERE NO LEAKS IN THE SYS. SINCE IT ONLY HAPPENED WHEN THE APU WAS RUNNING WE APPLIED MEL XX; AND ACFT DEPARTED ON FLT. THE TEAM LEAD (AUDITING THE MEL RUN) AND ANOTHER CTLR QUESTIONED ME ABOUT THE MEL. I HAD APPLIED THE WRONG MEL. AT THIS TIME I CONTACTED MAINT TO RECLASSIFY THE MEL TO YY (WING BODY OVERHEAT SYS-L). THIS WAS ACCOMPLISHED IN THE LOGBOOK ONCE THE ACFT ARRIVED. THE ACFT HAD FLOWN 2 FLT LEGS WITH THE WRONG MEL APPLIED. ACFT WAS REPAIRED THAT NIGHT; FOUND LOOSE CONNECTOR D1390 AND SECURED. THIS EVENT WAS AN ERROR ON MY PART. THINKING BACK I SHOULD HAVE SLOWED DOWN; CAREFULLY REVIEWED ALL APPLICABLE MEL'S; AND ASKED FOR ASSISTANCE FROM THE OTHER CTLRS. SUPPLEMENTAL INFO FROM ACN 744674: WE TOOK THE AIRPLANE FROM THE PREVIOUS CREW AND EVERYTHING WAS NORMAL UNTIL THE AFTER ENG START FLOW. DURING THE AFTER START FLOW; WE NOTICED THE L WING-BODY OVERHEAT LIGHT WAS ILLUMINATED. WE RAN THE L WING-BODY OVERHEAT CHKLIST THROUGH TURNING THE APU SWITCH OFF. AFTER A FEW SECONDS; THE LIGHT REMAINED ILLUMINATED; SO WE INFORMED MAINT AND RETURNED TO THE GATE. I DID NOT NOTICE WHEN THE LIGHT WENT OUT. HOWEVER; THE MECH ENTERED THE COCKPIT RIGHT AFTER ENG SHUTDOWN AND NOTED THE LIGHT WAS EXTINGUISHED AT THAT TIME. THE MECH TOLD US HE KNEW EXACTLY WHAT THE PROB WAS. NEXT; THE CAPT CONTACTED MAINT CTL AND DISPATCH WITH THE MECH; AND AN MEL WAS ISSUED FOR THE APU. IT SEEMED THAT ALL THE PROPER PEOPLE WERE IN THE LOOP AND THE MEL APPEARED ROUTINE TO ME. WE FLEW THE NEXT 2 LEGS WITHOUT USING THE APU; AND ALL OTHER OPS WERE NORMAL. THE NEXT DAY; THE OPS COORDINATOR CALLED THE CAPT TO INFORM HIM THAT THERE WAS A PROB WITH THE MEL AND ASSOCIATED WRITE-UP. A SECOND CALL TO THE OPS COORDINATOR CONFIRMED THAT THE MEL SHOULD HAVE BEEN ISSUED FOR A WING-BODY OVERHEAT AND NOT THE APU. THIS WAS A LEARNING EXPERIENCE FOR ME. BESIDES LEARNING WHICH MEL SHOULD HAVE APPLIED IN THIS PARTICULAR CASE; I WILL DOUBLE MY EFFORTS IN THE FUTURE TO ENSURE AN MEL PROPERLY MATCHES THE PROB AND CAUTION LIGHTS IN THE COCKPIT. I WILL BE ESPECIALLY VIGILANT TO ENSURE AN MEL CLOSELY MATCHES THE COCKPIT PROB AND INDICATIONS. ADDITIONALLY; I WILL CONTINUE TO APPLY A HEALTHY DOSE OF SKEPTICISM TO THE WRITE-UPS IN ORDER TO CATCH ERRORS AND OMISSIONS.

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.