Narrative:

One of our deferred maintenance items was the 'B' loop for the #2 engine. Upon review of the MEL and a fire test; we found the fire detection system to be in compliance under the requirements of the MEL. While on climb out of ZZZ through approximately FL230; we received a fire warning for engine #2. We complied with the recall items and then to fly the aircraft and talk to ATC. While the captain dealt with checklist; flight attendants; passenger; and sent an ACARS message to flight control; we declared an emergency and felt the safest course of action was to return to ZZZ. We requested runway 9L in ZZZ for our runway and also for crash fire rescue equipment to be present. We also informed ATC that although we had discharged both fire bottles; we still had a fire warning present. We determined this through the illumination of the 'a' loop and the fire handle for engine #2. Upon landing; crash fire rescue equipment and adjacent aircraft reported no fire or smoke. After an inspection by crash fire rescue equipment we returned to the gate. The captain spoke in person with maintenance; filled out the aircraft logbook and an in-flight shutdown form as required by our company. Even after shutdown and until we left the aircraft with maintenance personnel; the #2 engine was still illuminated even though there was not a fire present currently or at any time. This in retrospect was nothing more than a false indication.

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Original NASA ASRS Text

Title: AN MD88 CREW DEPARTING ZZZ WITH #2 ENG 'B' FIRE LOOP ON MEL EXPERIENCED A FIRE WARNING ON THAT ENG. THE CREW SHUT DOWN THE ENG AND RETURNED TO ZZZ WHERE THE FIRE WARNING WAS FOUND TO BE FALSE.

Narrative: ONE OF OUR DEFERRED MAINT ITEMS WAS THE 'B' LOOP FOR THE #2 ENG. UPON REVIEW OF THE MEL AND A FIRE TEST; WE FOUND THE FIRE DETECTION SYS TO BE IN COMPLIANCE UNDER THE REQUIREMENTS OF THE MEL. WHILE ON CLBOUT OF ZZZ THROUGH APPROX FL230; WE RECEIVED A FIRE WARNING FOR ENG #2. WE COMPLIED WITH THE RECALL ITEMS AND THEN TO FLY THE ACFT AND TALK TO ATC. WHILE THE CAPT DEALT WITH CHKLIST; FLT ATTENDANTS; PAX; AND SENT AN ACARS MESSAGE TO FLT CTL; WE DECLARED AN EMER AND FELT THE SAFEST COURSE OF ACTION WAS TO RETURN TO ZZZ. WE REQUESTED RWY 9L IN ZZZ FOR OUR RWY AND ALSO FOR CFR TO BE PRESENT. WE ALSO INFORMED ATC THAT ALTHOUGH WE HAD DISCHARGED BOTH FIRE BOTTLES; WE STILL HAD A FIRE WARNING PRESENT. WE DETERMINED THIS THROUGH THE ILLUMINATION OF THE 'A' LOOP AND THE FIRE HANDLE FOR ENG #2. UPON LNDG; CFR AND ADJACENT ACFT RPTED NO FIRE OR SMOKE. AFTER AN INSPECTION BY CFR WE RETURNED TO THE GATE. THE CAPT SPOKE IN PERSON WITH MAINT; FILLED OUT THE ACFT LOGBOOK AND AN INFLT SHUTDOWN FORM AS REQUIRED BY OUR COMPANY. EVEN AFTER SHUTDOWN AND UNTIL WE LEFT THE ACFT WITH MAINT PERSONNEL; THE #2 ENG WAS STILL ILLUMINATED EVEN THOUGH THERE WAS NOT A FIRE PRESENT CURRENTLY OR AT ANY TIME. THIS IN RETROSPECT WAS NOTHING MORE THAN A FALSE INDICATION.

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.