The flight crew responded to an APU fire warning on takeoff by completing the APU fire procedures, d...

Attributes
ACN	329755
Time
Date	199603
Day	Tue
Local Time Of Day	0601 To 1200
Place
Locale Reference	airport : aus
State Reference	TX
Altitude	msl bound lower : 2000 msl bound upper : 2000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : aus tower : aus
Operator	common carrier : air carrier
Make Model Name	B737-300
Operating Under FAR Part	Part 121
Navigation In Use	Other Other
Flight Phase	climbout : takeoff
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Experience	flight time last 90 days : 220 flight time total : 19000 flight time type : 14000
ASRS Report	329755
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : commercial pilot : instrument
Events
Anomaly	aircraft equipment problem : critical
Independent Detector	aircraft equipment other aircraft equipment : unspecified
Resolutory Action	flight crew : declared emergency other
Consequence	other
Supplementary
Primary Problem	Aircraft

Narrative:

After takeoff from aus in B737-300 the APU fire warning light came on with warning bell. Accomplished all emergency procedures and declared an emergency for return for landing at aus runway 31L. All checklists were properly accomplished and notifications were made and crew was prepared for an emergency evacuate/evacuation after landing. Landing was uneventful. Aircraft was not overweight and rapid stop on runway was accomplished. The APU fire warning light was still on and the bell had come on again during base leg to final. I ordered an evacuate/evacuation through all exits except aft doors because of fire indication. The evacuate/evacuation of 103 passenger was done with only a couple of minor injuries. I had quickly received information from fire department personnel that there was no fire visible so I stopped evacuate/evacuation at overwing exits to prevent unnecessary injuries as the wind was blowing at about 25-30 mph. All passenger exited safely out forward door slides. The fire warning system had apparently malfunctioned (still unknown for sure), but the light went out once shortly after fire extinguisher was discharged consistent with a real fire. Maintenance personnel could see no indication of fire in APU area and when APU fire warning system was tested the light and bell came on again. The B737-300 is supposed to have a system that will virtually eliminate false warnings, but the maintenance technician on the scene said he has seen other instances where the problem turned out to be in the control head in the cockpit. I realize that this panel is sealed from dirt, drink spillage, etc, but the area is invariably filthy and contamination of the circuits in there could be a possibility. I have no proof or reason to suspect it, but it couldn't hurt for us all to find a way to keep these areas clean just in case it could happen, and possibly prevent an unnecessary evacuate/evacuation and possible injuries.

Original NASA ASRS Text

Title: THE FLC RESPONDED TO AN APU FIRE WARNING ON TKOF BY COMPLETING THE APU FIRE PROCS, DECLARING AN EMER, RETURNING AND LNDG, ROLLING THE ARPT EMER FIRE EQUIP, AND EVACING THE PAX. THE APU FIRE WARNING WAS FALSE.

Narrative: AFTER TKOF FROM AUS IN B737-300 THE APU FIRE WARNING LIGHT CAME ON WITH WARNING BELL. ACCOMPLISHED ALL EMER PROCS AND DECLARED AN EMER FOR RETURN FOR LNDG AT AUS RWY 31L. ALL CHKLISTS WERE PROPERLY ACCOMPLISHED AND NOTIFICATIONS WERE MADE AND CREW WAS PREPARED FOR AN EMER EVAC AFTER LNDG. LNDG WAS UNEVENTFUL. ACFT WAS NOT OVERWT AND RAPID STOP ON RWY WAS ACCOMPLISHED. THE APU FIRE WARNING LIGHT WAS STILL ON AND THE BELL HAD COME ON AGAIN DURING BASE LEG TO FINAL. I ORDERED AN EVAC THROUGH ALL EXITS EXCEPT AFT DOORS BECAUSE OF FIRE INDICATION. THE EVAC OF 103 PAX WAS DONE WITH ONLY A COUPLE OF MINOR INJURIES. I HAD QUICKLY RECEIVED INFO FROM FIRE DEPT PERSONNEL THAT THERE WAS NO FIRE VISIBLE SO I STOPPED EVAC AT OVERWING EXITS TO PREVENT UNNECESSARY INJURIES AS THE WIND WAS BLOWING AT ABOUT 25-30 MPH. ALL PAX EXITED SAFELY OUT FORWARD DOOR SLIDES. THE FIRE WARNING SYS HAD APPARENTLY MALFUNCTIONED (STILL UNKNOWN FOR SURE), BUT THE LIGHT WENT OUT ONCE SHORTLY AFTER FIRE EXTINGUISHER WAS DISCHARGED CONSISTENT WITH A REAL FIRE. MAINT PERSONNEL COULD SEE NO INDICATION OF FIRE IN APU AREA AND WHEN APU FIRE WARNING SYS WAS TESTED THE LIGHT AND BELL CAME ON AGAIN. THE B737-300 IS SUPPOSED TO HAVE A SYS THAT WILL VIRTUALLY ELIMINATE FALSE WARNINGS, BUT THE MAINT TECHNICIAN ON THE SCENE SAID HE HAS SEEN OTHER INSTANCES WHERE THE PROB TURNED OUT TO BE IN THE CTL HEAD IN THE COCKPIT. I REALIZE THAT THIS PANEL IS SEALED FROM DIRT, DRINK SPILLAGE, ETC, BUT THE AREA IS INVARIABLY FILTHY AND CONTAMINATION OF THE CIRCUITS IN THERE COULD BE A POSSIBILITY. I HAVE NO PROOF OR REASON TO SUSPECT IT, BUT IT COULDN'T HURT FOR US ALL TO FIND A WAY TO KEEP THESE AREAS CLEAN JUST IN CASE IT COULD HAPPEN, AND POSSIBLY PREVENT AN UNNECESSARY EVAC AND POSSIBLE INJURIES.

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.

The flight crew responded to an APU fire warning on takeoff by completing the APU fire procedures, declaring an emergency, returning and landing, rolling the airport emergency fire equipment, and evacing the passenger. The APU fire warning was false.