|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 : 1000|
|Controlling Facilities||tracon : zzz.tracon|
|Operator||common carrier : air carrier|
|Make Model Name||B737-300|
|Operating Under FAR Part||Part 121|
|Navigation In Use||other|
|Flight Phase||climbout : initial|
descent : approach
|Affiliation||company : air carrier|
|Function||flight crew : captain|
oversight : pic
|Experience||flight time last 90 days : 120|
flight time total : 18000
flight time type : 800
|Affiliation||company : air carrier|
|Function||flight crew : first officer|
|Experience||flight time last 90 days : 200|
flight time total : 14000
flight time type : 3400
|Anomaly||aircraft equipment problem : critical|
|Independent Detector||aircraft equipment : gpws|
aircraft equipment other aircraft equipment : fmc
other flight crewa
|Resolutory Action||flight crew : overcame equipment problem|
On climb out of ZZZ at approximately 1000 ft AGL; the GPWS began to alert terrain pull up. We were VFR and continued climb as the alert continued to sound repeatedly. I noticed the captain's radio altimeter cycling. I advised the first officer to inhibit the GPWS switches using captain's emergency authority/authorized to silence the GPWS. After conferring with dispatch and maintenance; we elected to pull the circuit breaker for the captain's radio altimeter and continue on to ZZZ1 where the WX was overcast but basically VFR. Dispatch sent us the MEL information for the #1 radio altimeter being inoperative. After review; we felt that we should leave the breaker out so we would not encounter any more false GPWS warnings. On descent out of FL200 both FMC's failed and all waypoints and programmed routing information disappeared. We advised ATC that we had lost some of our navigation capabilities and that we were using raw data. We were vectored to a non eventful visual approach to ZZZ1 and executed a normal landing. If this would have been IMC conditions at ZZZ; we would have had to execute an escape maneuver. We were also not expecting to lose the FMC's which also could have proved interesting if the WX were worse. Callback conversation with reporter revealed the following information: the reporter stated that the radar altimeter failed after takeoff causing the egpws failure. There was no apparent connection between the radar altimeter failure and the FMC failure. Supplemental information from acn 809097: I asked the captain if he wanted me to place the 'flap inhibitor' switch to off. He said yes; and I did. It seemed to have no effect although we did shortly thereafter get a 'too low; gear' warning. Once above FL180 we got in the flight manual. We found no checklists -- just system information. We then went to the fom for general information. We then reasoned our problem was in the captain's radar altimeter and found guidance on all system that receive information from his RA. With this information the captain talked with dispatch listening in while I flew the airplane and handled ATC radio calls. After the captain talked with dispatch; we talked and decided the best course was to leave the P-18; B-5 circuit breakers pulled as directed and land. On descent; we lost both FMC's; proceeded via vectors and a visual approach.
Original NASA ASRS Text
Title: A B737-300 EGPWS 'TERRAIN; PULL UP' ALERTED CLBING THROUGH 1000 FT AFTER TKOF. THE CIRCUIT BREAKER WAS PULLED. LATER; ON APCH AT DEST BOTH FMC'S FAILED. FAILURES NOT RELATED.
Narrative: ON CLBOUT OF ZZZ AT APPROX 1000 FT AGL; THE GPWS BEGAN TO ALERT TERRAIN PULL UP. WE WERE VFR AND CONTINUED CLB AS THE ALERT CONTINUED TO SOUND REPEATEDLY. I NOTICED THE CAPT'S RADIO ALTIMETER CYCLING. I ADVISED THE FO TO INHIBIT THE GPWS SWITCHES USING CAPT'S EMER AUTH TO SILENCE THE GPWS. AFTER CONFERRING WITH DISPATCH AND MAINT; WE ELECTED TO PULL THE CIRCUIT BREAKER FOR THE CAPT'S RADIO ALTIMETER AND CONTINUE ON TO ZZZ1 WHERE THE WX WAS OVCST BUT BASICALLY VFR. DISPATCH SENT US THE MEL INFO FOR THE #1 RADIO ALTIMETER BEING INOP. AFTER REVIEW; WE FELT THAT WE SHOULD LEAVE THE BREAKER OUT SO WE WOULD NOT ENCOUNTER ANY MORE FALSE GPWS WARNINGS. ON DSCNT OUT OF FL200 BOTH FMC'S FAILED AND ALL WAYPOINTS AND PROGRAMMED ROUTING INFO DISAPPEARED. WE ADVISED ATC THAT WE HAD LOST SOME OF OUR NAV CAPABILITIES AND THAT WE WERE USING RAW DATA. WE WERE VECTORED TO A NON EVENTFUL VISUAL APCH TO ZZZ1 AND EXECUTED A NORMAL LNDG. IF THIS WOULD HAVE BEEN IMC CONDITIONS AT ZZZ; WE WOULD HAVE HAD TO EXECUTE AN ESCAPE MANEUVER. WE WERE ALSO NOT EXPECTING TO LOSE THE FMC'S WHICH ALSO COULD HAVE PROVED INTERESTING IF THE WX WERE WORSE. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE REPORTER STATED THAT THE RADAR ALTIMETER FAILED AFTER TKOF CAUSING THE EGPWS FAILURE. THERE WAS NO APPARENT CONNECTION BETWEEN THE RADAR ALTIMETER FAILURE AND THE FMC FAILURE. SUPPLEMENTAL INFO FROM ACN 809097: I ASKED THE CAPT IF HE WANTED ME TO PLACE THE 'FLAP INHIBITOR' SWITCH TO OFF. HE SAID YES; AND I DID. IT SEEMED TO HAVE NO EFFECT ALTHOUGH WE DID SHORTLY THEREAFTER GET A 'TOO LOW; GEAR' WARNING. ONCE ABOVE FL180 WE GOT IN THE FLT MANUAL. WE FOUND NO CHKLISTS -- JUST SYS INFO. WE THEN WENT TO THE FOM FOR GENERAL INFO. WE THEN REASONED OUR PROB WAS IN THE CAPT'S RADAR ALTIMETER AND FOUND GUIDANCE ON ALL SYS THAT RECEIVE INFO FROM HIS RA. WITH THIS INFO THE CAPT TALKED WITH DISPATCH LISTENING IN WHILE I FLEW THE AIRPLANE AND HANDLED ATC RADIO CALLS. AFTER THE CAPT TALKED WITH DISPATCH; WE TALKED AND DECIDED THE BEST COURSE WAS TO LEAVE THE P-18; B-5 CIRCUIT BREAKERS PULLED AS DIRECTED AND LAND. ON DSCNT; WE LOST BOTH FMC'S; PROCEEDED VIA VECTORS AND A VISUAL APCH.
Data retrieved from NASA's ASRS site as of May 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.