A B737-300 was dispatched after extensive troubleshooting, repair and replacement of units for a chr...

Attributes
ACN	464750
Time
Date	200003
Day	Wed
Local Time Of Day	0601 To 1200
Place
Locale Reference	airport : zzz.airport
State Reference	US
Altitude	agl single value : 0
Environment
Light	Daylight
Aircraft 1
Operator	common carrier : air carrier
Make Model Name	B737-300
Operating Under FAR Part	Part 121
Flight Phase	ground : maintenance ground : parked
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	maintenance : technician
Qualification	technician : powerplant technician : airframe
Experience	maintenance technician : 35
ASRS Report	464750
Person 2
Affiliation	company : air carrier
Function	maintenance : lead technician
Qualification	technician : airframe technician : powerplant
ASRS Report	464751
Events
Anomaly	aircraft equipment problem : critical other anomaly other
Independent Detector	aircraft equipment other aircraft equipment : #2 engine fire/ovht test
Resolutory Action	flight crew : diverted to another airport none taken : detected after the fact
Consequence	other other
Supplementary
Problem Areas	Aircraft Maintenance Human Performance
Primary Problem	Maintenance Human Performance

Narrative:

Mar/xa/00, aircraft xyz returned to ZZZ with an overheat light on 'a' loop #2 engine. 'B' loop was deferred. We troubleshot 'B' loop isolating to connector #2906 per wire diagram manual. Isolated short that disappeared when connector removed. Replaced connector and lower fire 'B' loop precautionary. 'B' system tested normal per maintenance manual. Replaced fire detector accessory unit and tested per maintenance manual to correct 'a' system overheat light. Both system normal, no deferrals. Callback conversation with reporter acn 464751 revealed the following information: the reporter stated the aircraft was worked for a chronic #2 fire warning 'a' and 'B' loop. The reporter said the 'a' loop was corrected with a detector unit replacement and tested per the maintenance manual. The reporter said 'B' loop was found to have a shorted connected and was replaced and also replaced the lower fire sensing loop on the 'B' system. The reporter stated the engine was run at high power (90%) for 15 mins and both system operated ok. The reporter said the airplane was returned to service and dispatched and after 1 hour of flight diverted due to #2 engine fire warning. The reporter said the reported fix was all fire sensing loops were replaced on #2 engine.

Original NASA ASRS Text

Title: A B737-300 WAS DISPATCHED AFTER EXTENSIVE TROUBLESHOOTING, REPAIR AND REPLACEMENT OF UNITS FOR A CHRONIC #2 ENG FIRE WARNING. APPROX 1 HR INTO FLT, ACFT DIVERTED DUE TO #2 ENG FALSE FIRE WARNING.

Narrative: MAR/XA/00, ACFT XYZ RETURNED TO ZZZ WITH AN OVERHEAT LIGHT ON 'A' LOOP #2 ENG. 'B' LOOP WAS DEFERRED. WE TROUBLESHOT 'B' LOOP ISOLATING TO CONNECTOR #2906 PER WIRE DIAGRAM MANUAL. ISOLATED SHORT THAT DISAPPEARED WHEN CONNECTOR REMOVED. REPLACED CONNECTOR AND LOWER FIRE 'B' LOOP PRECAUTIONARY. 'B' SYS TESTED NORMAL PER MAINT MANUAL. REPLACED FIRE DETECTOR ACCESSORY UNIT AND TESTED PER MAINT MANUAL TO CORRECT 'A' SYS OVERHEAT LIGHT. BOTH SYS NORMAL, NO DEFERRALS. CALLBACK CONVERSATION WITH RPTR ACN 464751 REVEALED THE FOLLOWING INFO: THE RPTR STATED THE ACFT WAS WORKED FOR A CHRONIC #2 FIRE WARNING 'A' AND 'B' LOOP. THE RPTR SAID THE 'A' LOOP WAS CORRECTED WITH A DETECTOR UNIT REPLACEMENT AND TESTED PER THE MAINT MANUAL. THE RPTR SAID 'B' LOOP WAS FOUND TO HAVE A SHORTED CONNECTED AND WAS REPLACED AND ALSO REPLACED THE LOWER FIRE SENSING LOOP ON THE 'B' SYS. THE RPTR STATED THE ENG WAS RUN AT HIGH PWR (90%) FOR 15 MINS AND BOTH SYS OPERATED OK. THE RPTR SAID THE AIRPLANE WAS RETURNED TO SVC AND DISPATCHED AND AFTER 1 HR OF FLT DIVERTED DUE TO #2 ENG FIRE WARNING. THE RPTR SAID THE RPTED FIX WAS ALL FIRE SENSING LOOPS WERE REPLACED ON #2 ENG.

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.

A B737-300 was dispatched after extensive troubleshooting, repair and replacement of units for a chronic #2 engine fire warning. Approximately 1 hour into flight, aircraft diverted due to #2 engine false fire warning.