|37000 Feet||Browse and search NASA's
Aviation Safety Reporting System
|Local Time Of Day||1801 To 2400|
|Locale Reference||airport : zzz.airport|
|Altitude||msl single value : 39000|
|Controlling Facilities||artcc : zoa.artcc|
|Operator||common carrier : air carrier|
|Make Model Name||B737-700|
|Operating Under FAR Part||Part 121|
|Flight Phase||cruise : level|
|Affiliation||company : air carrier|
|Function||flight crew : captain|
oversight : pic
|Affiliation||company : air carrier|
|Function||flight crew : first officer|
|Experience||flight time last 90 days : 200|
flight time type : 4321
|Anomaly||aircraft equipment problem : critical|
maintenance problem : improper maintenance
non adherence : far
non adherence : published procedure
|Independent Detector||aircraft equipment other aircraft equipment : aural warnings-false|
other flight crewa
other flight crewb
|Maintenance||contributing factor : schedule pressure|
performance deficiency : repair
|Problem Areas||Maintenance Human Performance|
|Primary Problem||Maintenance Human Performance|
At FL390 and about 1 hour into the flight; the fire bell; overspd clacker and gear horn warnings sounded for about 2 seconds. About 5 seconds later they sounded for another 2 seconds and about 5 seconds later they came on and remained on until block-in at ZZZ1. The aircraft had 2 previous write-ups in as many days for an errant gear horn at altitude. The takeoff warning horn joined the fray after setting the brakes at block-in. None of the warnings silenced until ZZZ1 maintenance pulled the appropriate circuit breakers. At the first indication of the warnings; a fire test was conducted (all lights illuminated then extinguished -- no fire!); engine indications were nominal (egt observed in particular); all 3 airspeed were normal; the aircraft confign normal for cruise and all other system instruments and warning lights were normal. With 1/2 of our warning system (aural warnings) ineffective; extra vigilance on lighted warnings was established. The QRH was reviewed to no avail. All warning cutout switches were attempted and audio control panels switched to auxiliary then normal (previous experience with past warning anomalies) with no positive results. Dispatch and maintenance control were conferred with ZZZ for further information (they had the same inputs for the audio control and test switches); again with no positive results. The noise level made it extremely difficult to communicate between the pilots; let alone on the radio; and was very distracting. No emergency existed and none was declared; however; considering all of the above and the possibility of an instrument approach at ZZZ2 (fog); a non-emergency diversion to ZZZ (WX cavu) was decided. All PA's were passed via the interphone to them and made by them to avoid alarming the passenger; although the alarms could be heard through the bulkhead as far back as row 6. All be it noisy; an uneventful landing was made in ZZZ1. Callback conversation with reporter revealed the following information: the reporter stated the cause of the aural warnings sounded is unknown but the airplane had 2 previous identical reports with no positive fix.
Original NASA ASRS Text
Title: A B737-700 IN CRUISE AT FL390 HAD FIRE WARNING BELL; OVERSPD CLACKER; GEAR WARNING HORN AND TKOF WARNING HORN ALL SOUNDING. QRH HAD NO PROC FOR THIS EVENT. LANDED WITH ALL ABOVE WARNINGS ACTIVATED. 2 PREVIOUS RPTS.
Narrative: AT FL390 AND ABOUT 1 HR INTO THE FLT; THE FIRE BELL; OVERSPD CLACKER AND GEAR HORN WARNINGS SOUNDED FOR ABOUT 2 SECONDS. ABOUT 5 SECONDS LATER THEY SOUNDED FOR ANOTHER 2 SECONDS AND ABOUT 5 SECONDS LATER THEY CAME ON AND REMAINED ON UNTIL BLOCK-IN AT ZZZ1. THE ACFT HAD 2 PREVIOUS WRITE-UPS IN AS MANY DAYS FOR AN ERRANT GEAR HORN AT ALT. THE TKOF WARNING HORN JOINED THE FRAY AFTER SETTING THE BRAKES AT BLOCK-IN. NONE OF THE WARNINGS SILENCED UNTIL ZZZ1 MAINT PULLED THE APPROPRIATE CIRCUIT BREAKERS. AT THE FIRST INDICATION OF THE WARNINGS; A FIRE TEST WAS CONDUCTED (ALL LIGHTS ILLUMINATED THEN EXTINGUISHED -- NO FIRE!); ENG INDICATIONS WERE NOMINAL (EGT OBSERVED IN PARTICULAR); ALL 3 AIRSPD WERE NORMAL; THE ACFT CONFIGN NORMAL FOR CRUISE AND ALL OTHER SYS INSTS AND WARNING LIGHTS WERE NORMAL. WITH 1/2 OF OUR WARNING SYS (AURAL WARNINGS) INEFFECTIVE; EXTRA VIGILANCE ON LIGHTED WARNINGS WAS ESTABLISHED. THE QRH WAS REVIEWED TO NO AVAIL. ALL WARNING CUTOUT SWITCHES WERE ATTEMPTED AND AUDIO CTL PANELS SWITCHED TO AUX THEN NORMAL (PREVIOUS EXPERIENCE WITH PAST WARNING ANOMALIES) WITH NO POSITIVE RESULTS. DISPATCH AND MAINT CTL WERE CONFERRED WITH ZZZ FOR FURTHER INFO (THEY HAD THE SAME INPUTS FOR THE AUDIO CTL AND TEST SWITCHES); AGAIN WITH NO POSITIVE RESULTS. THE NOISE LEVEL MADE IT EXTREMELY DIFFICULT TO COMMUNICATE BTWN THE PLTS; LET ALONE ON THE RADIO; AND WAS VERY DISTRACTING. NO EMER EXISTED AND NONE WAS DECLARED; HOWEVER; CONSIDERING ALL OF THE ABOVE AND THE POSSIBILITY OF AN INST APCH AT ZZZ2 (FOG); A NON-EMER DIVERSION TO ZZZ (WX CAVU) WAS DECIDED. ALL PA'S WERE PASSED VIA THE INTERPHONE TO THEM AND MADE BY THEM TO AVOID ALARMING THE PAX; ALTHOUGH THE ALARMS COULD BE HEARD THROUGH THE BULKHEAD AS FAR BACK AS ROW 6. ALL BE IT NOISY; AN UNEVENTFUL LNDG WAS MADE IN ZZZ1. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE RPTR STATED THE CAUSE OF THE AURAL WARNINGS SOUNDED IS UNKNOWN BUT THE AIRPLANE HAD 2 PREVIOUS IDENTICAL RPTS WITH NO POSITIVE FIX.
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.