Narrative:

En route to subic bay airport from narita airport, we were cleared direct to subic bay. The clearance came at a point between sarsi and cabin attendant VOR. Although we were in radar contact and radar idented, this descent would be during night IMC conditions into mountainous terrain. Additionally, subic bay is notamed for possible map shifts, therefore, the captain took special care in his brief for the descent and approach. After checking our direct course on the VOR, the captain 'hardwired' the outbound course on my VOR and the inbound course on his VOR. Both of us then selected map for the arrival and monitored the VOR course inbound on the numeric readout at the bottom of the display. At 40 DME we were cleared to descend to 8000 ft and asked to report sba 10 DME. The autoplt was flying the descent on schedule and we arrived at 10 DME at 245 KTS and at about 8500 ft the controller (subic approach) then cleared us to 6000 ft and for the VOR runway 7 approach. He also requested we report procedure turn outbound. The autoplt then continued down at approximately 2000 FPM through 8000 ft. At about 7800 ft or 7900 ft the CAWS announced '1000 ft.' both the captain and I immediately checked altitude and I actually started to execute the GPWS escape maneuver. The captain said there was no radar altimeter indication and that the call was false. Shortly, the CAWS then announced, '500 ft.' feeling ground impact was imminent, I pushed the throttles to the firewall through the fadec bar and rotated to greater than 15 degrees at pitch. The captain yelled that 'spoilers are up' and assumed the controls. I am sketchy on what happened next, but after the initial climb, the airspeed had apparently decayed into the red 'foot' and we were in 45 degrees of bank (right) and in a descent. The captain had full left aileron in and the plane was not responding. It is important to note we never reached stick shaker. At the second '500 ft' call I looked at the altitude and we had somehow now descended to around 6000 ft (things were shaking and the mfd was difficult to read). The high pitch angle, the degraded airspeed, the bank angle, and the '500 ft' call convinced me we were in immense danger of ground impact. I then reached up and extended the slats and brought the flaps to 15 degrees or so. Simultaneously, I pushed the yoke forward. Immediately, after the slats extended and the flaps came out, our outboard ailerons became unlocked. The aircraft rolled level and began a solid climb. We leveled at 9500 ft and found ourselves directly over the sba VOR. We executed the procedure turn and landed uneventfully. On the ground we called subic approach and they confirmed we were on the direct track to the VOR. The next leg to singapore we discovered that the GPWS sensor readout at FL390 indicated 32767 ft. This is just about the difference in altitude between the ground and the erroneous '1000 ft' and '500 ft' CAWS calls. We believe that the inertial altitudes gave us false CAWS warnings and that the stick shaker did not work as we rotated and it allowed us to approach a stall. Further, we did not receive automatic slat extend or outboard ailerons because of this failure (should happen because of low speed protection). Callback conversation with reporter revealed the following information: the reporter stated that there was no map shift although there existed a NOTAM warning of possible map shifts and he was worried about the volcano terrain near clark AFB being nearby. The bank angle of 30-40 degrees occurred because of loss of lateral control without outboard ailerons and a clean wing at about 120 KIAS and the pitch up attitude 30-40 degrees. The first phase of the GPWS procedure is to pitch to 15 degrees, but if ground contact is imminent then pull on up to the stick shaker. It was a rainy dark night and instruments were indicating that ground contact was imminent. There was no indication that any of the computers had malfunctioned. The computers are supposed to do a self test and that is how the industry knows the low speed protection and stick shaker are working. There is also a test switch for the stick shaker in many airplanes that is tested regularly by crew checklist. There was no indicationthat these protections were not functioning. Maintenance said the IRU was not the problem. The faulty radar altimeter caused the GPWS false warning. The reporter said lowering the flaps to recover from the stall was not a trained stall recovery procedure but was what saved them by giving them outboard ailerons to help level the bank and a wing shape that flew at that slow of an airspeed and perhaps prevented a deep stall.

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Original NASA ASRS Text

Title: AFTER MIDNIGHT IN IMC WITH RAIN A GPWS 1000 FT WARNING OCCURRED. THE FO REALIZING HIGH TERRAIN IN THE AREA COMMENCED AN ESCAPE MANEUVER, MAX PWR AND PITCH TO THE STICK SHAKER. AT 30-40 DEG NOSE UP AND 120 KTS, THE R WING DROPPED TO A 30-40 DEG BANK. THERE NEVER WAS A STICK SHAKER, OR LOW SPD SLAT EXTENSION AND OUTBOARD AILERON UNLOCK. GPWS STILL SOUNDING HE LOWERED THE FLAPS, WHICH ACTIVATED THE OUTBOARD AILERONS AND RECOVERED FROM THE BANK AND STALL.

Narrative: ENRTE TO SUBIC BAY ARPT FROM NARITA ARPT, WE WERE CLRED DIRECT TO SUBIC BAY. THE CLRNC CAME AT A POINT BTWN SARSI AND CAB VOR. ALTHOUGH WE WERE IN RADAR CONTACT AND RADAR IDENTED, THIS DSCNT WOULD BE DURING NIGHT IMC CONDITIONS INTO MOUNTAINOUS TERRAIN. ADDITIONALLY, SUBIC BAY IS NOTAMED FOR POSSIBLE MAP SHIFTS, THEREFORE, THE CAPT TOOK SPECIAL CARE IN HIS BRIEF FOR THE DSCNT AND APCH. AFTER CHKING OUR DIRECT COURSE ON THE VOR, THE CAPT 'HARDWIRED' THE OUTBOUND COURSE ON MY VOR AND THE INBOUND COURSE ON HIS VOR. BOTH OF US THEN SELECTED MAP FOR THE ARR AND MONITORED THE VOR COURSE INBOUND ON THE NUMERIC READOUT AT THE BOTTOM OF THE DISPLAY. AT 40 DME WE WERE CLRED TO DSND TO 8000 FT AND ASKED TO RPT SBA 10 DME. THE AUTOPLT WAS FLYING THE DSCNT ON SCHEDULE AND WE ARRIVED AT 10 DME AT 245 KTS AND AT ABOUT 8500 FT THE CTLR (SUBIC APCH) THEN CLRED US TO 6000 FT AND FOR THE VOR RWY 7 APCH. HE ALSO REQUESTED WE RPT PROC TURN OUTBOUND. THE AUTOPLT THEN CONTINUED DOWN AT APPROX 2000 FPM THROUGH 8000 FT. AT ABOUT 7800 FT OR 7900 FT THE CAWS ANNOUNCED '1000 FT.' BOTH THE CAPT AND I IMMEDIATELY CHKED ALT AND I ACTUALLY STARTED TO EXECUTE THE GPWS ESCAPE MANEUVER. THE CAPT SAID THERE WAS NO RADAR ALTIMETER INDICATION AND THAT THE CALL WAS FALSE. SHORTLY, THE CAWS THEN ANNOUNCED, '500 FT.' FEELING GND IMPACT WAS IMMINENT, I PUSHED THE THROTTLES TO THE FIREWALL THROUGH THE FADEC BAR AND ROTATED TO GREATER THAN 15 DEGS AT PITCH. THE CAPT YELLED THAT 'SPOILERS ARE UP' AND ASSUMED THE CTLS. I AM SKETCHY ON WHAT HAPPENED NEXT, BUT AFTER THE INITIAL CLB, THE AIRSPD HAD APPARENTLY DECAYED INTO THE RED 'FOOT' AND WE WERE IN 45 DEGS OF BANK (R) AND IN A DSCNT. THE CAPT HAD FULL L AILERON IN AND THE PLANE WAS NOT RESPONDING. IT IS IMPORTANT TO NOTE WE NEVER REACHED STICK SHAKER. AT THE SECOND '500 FT' CALL I LOOKED AT THE ALT AND WE HAD SOMEHOW NOW DSNDED TO AROUND 6000 FT (THINGS WERE SHAKING AND THE MFD WAS DIFFICULT TO READ). THE HIGH PITCH ANGLE, THE DEGRADED AIRSPD, THE BANK ANGLE, AND THE '500 FT' CALL CONVINCED ME WE WERE IN IMMENSE DANGER OF GND IMPACT. I THEN REACHED UP AND EXTENDED THE SLATS AND BROUGHT THE FLAPS TO 15 DEGS OR SO. SIMULTANEOUSLY, I PUSHED THE YOKE FORWARD. IMMEDIATELY, AFTER THE SLATS EXTENDED AND THE FLAPS CAME OUT, OUR OUTBOARD AILERONS BECAME UNLOCKED. THE ACFT ROLLED LEVEL AND BEGAN A SOLID CLB. WE LEVELED AT 9500 FT AND FOUND OURSELVES DIRECTLY OVER THE SBA VOR. WE EXECUTED THE PROC TURN AND LANDED UNEVENTFULLY. ON THE GND WE CALLED SUBIC APCH AND THEY CONFIRMED WE WERE ON THE DIRECT TRACK TO THE VOR. THE NEXT LEG TO SINGAPORE WE DISCOVERED THAT THE GPWS SENSOR READOUT AT FL390 INDICATED 32767 FT. THIS IS JUST ABOUT THE DIFFERENCE IN ALT BTWN THE GND AND THE ERRONEOUS '1000 FT' AND '500 FT' CAWS CALLS. WE BELIEVE THAT THE INERTIAL ALTS GAVE US FALSE CAWS WARNINGS AND THAT THE STICK SHAKER DID NOT WORK AS WE ROTATED AND IT ALLOWED US TO APCH A STALL. FURTHER, WE DID NOT RECEIVE AUTO SLAT EXTEND OR OUTBOARD AILERONS BECAUSE OF THIS FAILURE (SHOULD HAPPEN BECAUSE OF LOW SPD PROTECTION). CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE RPTR STATED THAT THERE WAS NO MAP SHIFT ALTHOUGH THERE EXISTED A NOTAM WARNING OF POSSIBLE MAP SHIFTS AND HE WAS WORRIED ABOUT THE VOLCANO TERRAIN NEAR CLARK AFB BEING NEARBY. THE BANK ANGLE OF 30-40 DEGS OCCURRED BECAUSE OF LOSS OF LATERAL CTL WITHOUT OUTBOARD AILERONS AND A CLEAN WING AT ABOUT 120 KIAS AND THE PITCH UP ATTITUDE 30-40 DEGS. THE FIRST PHASE OF THE GPWS PROC IS TO PITCH TO 15 DEGS, BUT IF GND CONTACT IS IMMINENT THEN PULL ON UP TO THE STICK SHAKER. IT WAS A RAINY DARK NIGHT AND INSTS WERE INDICATING THAT GND CONTACT WAS IMMINENT. THERE WAS NO INDICATION THAT ANY OF THE COMPUTERS HAD MALFUNCTIONED. THE COMPUTERS ARE SUPPOSED TO DO A SELF TEST AND THAT IS HOW THE INDUSTRY KNOWS THE LOW SPD PROTECTION AND STICK SHAKER ARE WORKING. THERE IS ALSO A TEST SWITCH FOR THE STICK SHAKER IN MANY AIRPLANES THAT IS TESTED REGULARLY BY CREW CHKLIST. THERE WAS NO INDICATIONTHAT THESE PROTECTIONS WERE NOT FUNCTIONING. MAINT SAID THE IRU WAS NOT THE PROB. THE FAULTY RADAR ALTIMETER CAUSED THE GPWS FALSE WARNING. THE RPTR SAID LOWERING THE FLAPS TO RECOVER FROM THE STALL WAS NOT A TRAINED STALL RECOVERY PROC BUT WAS WHAT SAVED THEM BY GIVING THEM OUTBOARD AILERONS TO HELP LEVEL THE BANK AND A WING SHAPE THAT FLEW AT THAT SLOW OF AN AIRSPD AND PERHAPS PREVENTED A DEEP STALL.

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.