<< >> NASA ASRS Report 734633, April 2007

A B737-300 aircraft flight crew discharged APU fire bottle due to APU fire 'T' handle red light came on after circuit breaker activated. MEL did not reference red light always 'on.'

Attributes
ACN	734633
Time
Date	200704
Local Time Of Day	1201 To 1800
Place
Locale Reference	airport : zzz.airport
State Reference	US
Altitude	agl single value : 0
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Operator	common carrier : air carrier
Make Model Name	B737-300
Operating Under FAR Part	Part 121
Flight Phase	ground : preflight
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	oversight : supervisor
ASRS Report	734633
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Experience	flight time last 90 days : 216 flight time type : 15000
ASRS Report	734626
Events
Anomaly	aircraft equipment problem : critical maintenance problem : improper documentation non adherence : published procedure non adherence : far maintenance problem : improper documentation
Independent Detector	aircraft equipment other aircraft equipment : fire detection-apu other flight crewa
Resolutory Action	none taken : detected after the fact
Consequence	other
Factors
Maintenance	contributing factor : briefing performance deficiency : non compliance with legal requirements performance deficiency : logbook entry
Supplementary
Problem Areas	Maintenance Human Performance Aircraft Flight Crew Human Performance
Primary Problem	Maintenance Human Performance

Narrative:

Flight crew reported on fire detection test the 'det inoperative' light was inoperative; and APU fire t-handle light remained on after test switch released. After conference with flight crew we decided to MEL APU fire detection inoperative. APU is not used and APU fire detection circuit breaker is opened and collared. My entry into maintenance records computer did not mention the t-handle light remaining on. Apparently several flight legs later; approval was given to reset the circuit breaker and use the APU. This resulted in a false APU fire warning and blown bottle. The misunderstanding was probably the next item of MEL: 'APU det inoperative' light which allows APU operation if the fire detection operates normal. In this case; apparently the APU detection system was intermittent and tested normal for a while. I feel that adding more detail to the discrepancy; in this case; that the APU t-handle light remained on; could have prevented this error from happening.

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Original NASA ASRS Text

Title: A B737-300 ACFT FLT CREW DISCHARGED APU FIRE BOTTLE DUE TO APU FIRE 'T' HANDLE RED LIGHT CAME ON AFTER CIRCUIT BREAKER ACTIVATED. MEL DID NOT REFERENCE RED LIGHT ALWAYS 'ON.'

Narrative: FLT CREW RPTED ON FIRE DETECTION TEST THE 'DET INOP' LIGHT WAS INOP; AND APU FIRE T-HANDLE LIGHT REMAINED ON AFTER TEST SWITCH RELEASED. AFTER CONFERENCE WITH FLT CREW WE DECIDED TO MEL APU FIRE DETECTION INOP. APU IS NOT USED AND APU FIRE DETECTION CIRCUIT BREAKER IS OPENED AND COLLARED. MY ENTRY INTO MAINT RECORDS COMPUTER DID NOT MENTION THE T-HANDLE LIGHT REMAINING ON. APPARENTLY SEVERAL FLT LEGS LATER; APPROVAL WAS GIVEN TO RESET THE CIRCUIT BREAKER AND USE THE APU. THIS RESULTED IN A FALSE APU FIRE WARNING AND BLOWN BOTTLE. THE MISUNDERSTANDING WAS PROBABLY THE NEXT ITEM OF MEL: 'APU DET INOP' LIGHT WHICH ALLOWS APU OP IF THE FIRE DETECTION OPERATES NORMAL. IN THIS CASE; APPARENTLY THE APU DETECTION SYS WAS INTERMITTENT AND TESTED NORMAL FOR A WHILE. I FEEL THAT ADDING MORE DETAIL TO THE DISCREPANCY; IN THIS CASE; THAT THE APU T-HANDLE LIGHT REMAINED ON; COULD HAVE PREVENTED THIS ERROR FROM HAPPENING.

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.