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On approach; a saab-340B flight crew received a terrain awareness warning system (taws) terrain alert. During the following morning's first flight of the day checks; the taws test failed citing 'internal GPS not navigating.'
| Attributes | |
| ACN | 818840 |
| Time | |
| Date | 200901 |
| Local Time Of Day | 1801-2400 |
| Place | |
| Locale Reference | ZZZZ.Airport |
| State Reference | FO |
| Environment | |
| Flight Conditions | IMC |
| Light | Daylight |
| Aircraft 1 | |
| Make Model Name | SF 340B |
| Operating Under FAR Part | Part 121 |
| Flight Phase | Initial Approach |
| Flight Plan | IFR |
| Component | |
| Aircraft Component | GPWS |
| Person 1 | |
| Function | First Officer Pilot Flying |
| Qualification | Flight Crew Commercial |
| Events | |
| Anomaly | Aircraft Equipment Problem Critical |
Narrative:
On approach into ZZZZ; we received a taws terrain alert; followed by an obstacle alert; and a pull-up command. We then executed the taws escape maneuver; and received clearance for another approach. We landed uneventfully the second time. We are not sure why we would receive the command; we were at proper altitude; verified by ATC; and on course. The following morning; however; during my first-flight-of-the-day checks; the taws test failed; citing; 'internal GPS not navigating.' so it is possible that taws received a false position from the FMS the night before. Callback conversation with reporter revealed the following information: reporter stated he does not know if maintenance was able to determine the cause of the inflight taws alert on the saab-340B; or the preflight test failure the following morning. Reporter stated he wondered if the pre-programmed database of all the obstacles was an issue or an FMS position signal.
Original NASA ASRS Text
Title: On approach; a Saab-340B flight crew received a Terrain Awareness Warning System (TAWS) Terrain alert. During the following morning's first flight of the day checks; the TAWS test failed citing 'internal GPS not navigating.'
Narrative: On approach into ZZZZ; we received a TAWS terrain alert; followed by an obstacle alert; and a pull-up command. We then executed the TAWS escape maneuver; and received clearance for another approach. We landed uneventfully the second time. We are not sure why we would receive the command; we were at proper altitude; verified by ATC; and on course. The following morning; however; during my first-flight-of-the-day checks; the TAWS test failed; citing; 'internal GPS not navigating.' So it is possible that TAWS received a false position from the FMS the night before. Callback conversation with Reporter revealed the following information: Reporter stated he does not know if Maintenance was able to determine the cause of the inflight TAWS alert on the Saab-340B; or the preflight test failure the following morning. Reporter stated he wondered if the pre-programmed database of all the obstacles was an issue or an FMS position signal.
Data retrieved from NASA's ASRS site as of April 2012 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.