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Flight crew of an MD80 responded to a GPWS warning by climbing in an escape maneuver. Since the aircraft was in level flight at the time, the highest terrain mountain peak was well below their altitude by 2000 ft and the radar altimeter tape showed no corresponding indication readout for this warning, the flight crew concluded that the GPWS was not working correctly.
| Attributes | |
| ACN | 380962 |
| Time | |
| Date | 199709 |
| Day | Fri |
| Local Time Of Day | 0001 To 0600 |
| Place | |
| Locale Reference | atc facility : pgy airport : san |
| State Reference | CA |
| Altitude | msl bound lower : 8000 msl bound upper : 9700 |
| Environment | |
| Flight Conditions | VMC |
| Light | Night |
| Aircraft 1 | |
| Controlling Facilities | tower : ord |
| Operator | common carrier : air carrier |
| Make Model Name | MD-80 Super 80 |
| Operating Under FAR Part | Part 121 |
| Flight Phase | cruise other descent other |
| Route In Use | arrival other arrival star : star enroute airway : san |
| Flight Plan | IFR |
| Person 1 | |
| Affiliation | company : air carrier |
| Function | flight crew : captain oversight : pic |
| Qualification | pilot : atp |
| ASRS Report | 380962 |
| Person 2 | |
| Affiliation | company : air carrier |
| Function | flight crew : first officer |
| Qualification | pilot : instrument pilot : commercial |
| Events | |
| Anomaly | aircraft equipment problem : less severe altitude deviation : excursion from assigned altitude other anomaly other |
| Independent Detector | aircraft equipment other aircraft equipment : unspecified other flight crewa |
| Resolutory Action | flight crew : took evasive action |
| Consequence | Other |
| Supplementary | |
| Primary Problem | Aircraft |
| Air Traffic Incident | other |
Narrative:
WX clear, level flight, 8000 ft MSL, altimeter setting 29.86, airspeed 250 KTS, inbound pogie VOR. GPWS terrain, terrain, aural warning. I initiated the escape maneuver, climbed to 9700 ft MSL. Notified socal approach of our altitude deviation. Socal advised the highest terrain is a peak at just over 6000 ft MSL. The radar altimeter tape never came into view, neither through the terrain, terrain aural warning nor through the escape maneuver. I confirmed via the area chart the existence of a 6000 ft MSL peak at the pogie 038/27 fix, but no closure, ie, level flight and 2000 ft clearance. I don't understand why I got the terrain, terrain warning. Approach and landing were uneventful.
Original NASA ASRS Text
Title: FLC OF AN MD80 RESPONDED TO A GPWS WARNING BY CLBING IN AN ESCAPE MANEUVER. SINCE THE ACFT WAS IN LEVEL FLT AT THE TIME, THE HIGHEST TERRAIN MOUNTAIN PEAK WAS WELL BELOW THEIR ALT BY 2000 FT AND THE RADAR ALTIMETER TAPE SHOWED NO CORRESPONDING INDICATION READOUT FOR THIS WARNING, THE FLC CONCLUDED THAT THE GPWS WAS NOT WORKING CORRECTLY.
Narrative: WX CLR, LEVEL FLT, 8000 FT MSL, ALTIMETER SETTING 29.86, AIRSPD 250 KTS, INBOUND POGIE VOR. GPWS TERRAIN, TERRAIN, AURAL WARNING. I INITIATED THE ESCAPE MANEUVER, CLBED TO 9700 FT MSL. NOTIFIED SOCAL APCH OF OUR ALTDEV. SOCAL ADVISED THE HIGHEST TERRAIN IS A PEAK AT JUST OVER 6000 FT MSL. THE RADAR ALTIMETER TAPE NEVER CAME INTO VIEW, NEITHER THROUGH THE TERRAIN, TERRAIN AURAL WARNING NOR THROUGH THE ESCAPE MANEUVER. I CONFIRMED VIA THE AREA CHART THE EXISTENCE OF A 6000 FT MSL PEAK AT THE POGIE 038/27 FIX, BUT NO CLOSURE, IE, LEVEL FLT AND 2000 FT CLRNC. I DON'T UNDERSTAND WHY I GOT THE TERRAIN, TERRAIN WARNING. APCH AND LNDG WERE UNEVENTFUL.
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.