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B737 first officer reported erroneous terrain warnings while established on an instrument approach.
| Attributes | |
| ACN | 1685376 |
| Time | |
| Date | 201909 |
| Local Time Of Day | 1801-2400 |
| Place | |
| Locale Reference | RNO.Airport |
| State Reference | NV |
| Environment | |
| Light | Night |
| Aircraft 1 | |
| Make Model Name | B737-800 |
| Operating Under FAR Part | Part 121 |
| Flight Phase | Initial Approach |
| Flight Plan | IFR |
| Component | |
| Aircraft Component | GPWS |
| Person 1 | |
| Function | First Officer Pilot Not Flying |
| Qualification | Flight Crew Air Transport Pilot (ATP) Flight Crew Instrument Flight Crew Multiengine |
| Experience | Flight Crew Last 90 Days 240 Flight Crew Type 4000 |
| Events | |
| Anomaly | Aircraft Equipment Problem Less Severe Deviation - Procedural Published Material / Policy Inflight Event / Encounter Weather / Turbulence Inflight Event / Encounter Unstabilized Approach |
Narrative:
Cleared for the RNAV Y [runway] 16R. The approach was normal. Tower reported a surface wind that resulted in more than 10 kts. Tailwind so we elected to go around and shoot the ILS [runway] 34L. While on final for [runway] 34L; we were encountering a 25 to 30 [kt.] tailwind while tracking the localizer and glide slope. Around 1500 ft. AGL; we received a terrain warning. Despite being on the localizer and glide slope; we followed company procedure and executed the terrain avoidance maneuver. Tower was perplexed by our go-around and handed us off to norcal. Norcal was also confused about the reason for the go-around. We were vectored back around for another ILS to [runway] 34L. Our fuel on board at the time was just over 5;000 pounds. We discussed the possible need to divert to smf in the event of another missed approach. The captain decided to configure early and slow early in case the terrain warning derived from our high ground speed (with the 30 knot tailwind) and our descent rate. At 1500 ft. AGL; with the localizer and glide slope tracking dead on; we received three or four terrain cautions. We could visually see the terrain off the left side of the aircraft. The captain; after conferring with me; decided to continue; exercising his emergency authority. I wholeheartedly agreed with his decision and his reasoning. It was readily apparent that the caution was erroneous. We were in constant communication with tower during our entire approach and there was no concern on their part.
Original NASA ASRS Text
Title: B737 First Officer reported erroneous terrain warnings while established on an instrument approach.
Narrative: Cleared for the RNAV Y [Runway] 16R. The approach was normal. Tower reported a surface wind that resulted in more than 10 kts. tailwind so we elected to go around and shoot the ILS [Runway] 34L. While on final for [Runway] 34L; we were encountering a 25 to 30 [kt.] tailwind while tracking the localizer and glide slope. Around 1500 ft. AGL; we received a Terrain Warning. Despite being on the localizer and glide slope; we followed Company procedure and executed the terrain avoidance maneuver. Tower was perplexed by our go-around and handed us off to NorCal. NorCal was also confused about the reason for the go-around. We were vectored back around for another ILS to [Runway] 34L. Our fuel on board at the time was just over 5;000 pounds. We discussed the possible need to divert to SMF in the event of another missed approach. The Captain decided to configure early and slow early in case the Terrain Warning derived from our high ground speed (with the 30 knot tailwind) and our descent rate. At 1500 ft. AGL; with the localizer and glide slope tracking dead on; we received three or four terrain cautions. We could visually see the terrain off the left side of the aircraft. The Captain; after conferring with me; decided to continue; exercising his emergency authority. I wholeheartedly agreed with his decision and his reasoning. It was readily apparent that the caution was erroneous. We were in constant communication with Tower during our entire approach and there was no concern on their part.
Data retrieved from NASA's ASRS site 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.