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The flight crew of a commuter aircraft believe their failure to 'temperature compensate' for a one degree celsius drop in OAT was the proximate cause of an egpws terrain warning experienced approaching suxci while performing the RNAV (GPS)-D IAP to mfr.
| Attributes | |
| ACN | 989154 |
| Time | |
| Date | 201201 |
| Local Time Of Day | 0001-0600 |
| Place | |
| Locale Reference | ZSE.ARTCC |
| State Reference | WA |
| Aircraft 1 | |
| Make Model Name | Q400 |
| Operating Under FAR Part | Part 121 |
| Flight Phase | Initial Approach |
| Flight Plan | IFR |
| Component | |
| Aircraft Component | Altimeter |
| Person 1 | |
| Function | Captain Pilot Not Flying |
| Qualification | Flight Crew Air Transport Pilot (ATP) |
| Events | |
| Anomaly | Aircraft Equipment Problem Less Severe Inflight Event / Encounter CFTT / CFIT |
Narrative:
We were executing the RNAV GPS D approach into mfr. We crossed brket at 10;000 ft; then descended to 8;500 ft and were established level at 8;500 prior to suxci. We got a 'terrain pull up' warning. We executed a missed approach and requested vectors for the ILS approach into mfr. Surface temperature at mfr had just dropped from 1 to 0 degrees C; and we neglected to temperature compensate. ASOS at mfr does not broadcast weather when ATIS is not broadcast. We were given weather from center just prior to being cleared for the approach. A post flight debrief of this event was performed; and I determined that temperature compensation at that position would have put us at about 8;900 ft. Charted terrain where the event occurred shows a terrain feature in excess of 7;000 ft.the cause of this event was the flight crew's failure to anticipate a temperature drop into the temperature compensation range.
Original NASA ASRS Text
Title: The flight crew of a commuter aircraft believe their failure to 'temperature compensate' for a one degree celsius drop in OAT was the proximate cause of an EGPWS Terrain warning experienced approaching SUXCI while performing the RNAV (GPS)-D IAP to MFR.
Narrative: We were executing the RNAV GPS D approach into MFR. We crossed BRKET at 10;000 FT; then descended to 8;500 FT and were established level at 8;500 prior to SUXCI. We got a 'TERRAIN PULL UP' warning. We executed a missed approach and requested vectors for the ILS approach into MFR. Surface temperature at MFR had just dropped from 1 to 0 degrees C; and we neglected to temperature compensate. ASOS at MFR does not broadcast weather when ATIS is not broadcast. We were given weather from Center just prior to being cleared for the approach. A post flight debrief of this event was performed; and I determined that temperature compensation at that position would have put us at about 8;900 FT. Charted terrain where the event occurred shows a terrain feature in excess of 7;000 FT.The cause of this event was the flight crew's failure to anticipate a temperature drop into the temperature compensation range.
Data retrieved from NASA's ASRS site as of July 2013 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.