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B737 first officer reported descending below the minimum sector altitude due to a communication breakdown with ATC.
| Attributes | |
| ACN | 1544833 |
| Time | |
| Date | 201805 |
| Local Time Of Day | 1201-1800 |
| Place | |
| Locale Reference | ZZZ.TRACON |
| State Reference | US |
| Environment | |
| Light | Daylight |
| Aircraft 1 | |
| Make Model Name | B737-700 |
| Operating Under FAR Part | Part 121 |
| Flight Phase | Initial Approach |
| Flight Plan | IFR |
| Person 1 | |
| Function | First Officer Pilot Flying |
| Qualification | Flight Crew Instrument Flight Crew Air Transport Pilot (ATP) Flight Crew Multiengine |
| Experience | Flight Crew Last 90 Days 159 |
| Events | |
| Anomaly | ATC Issue All Types Deviation - Altitude Overshoot Deviation - Procedural Clearance Deviation - Procedural Published Material / Policy Inflight Event / Encounter CFTT / CFIT |
Narrative:
We were flying to [the destination airport] and had several heading; speed; altitude and runway changes within the last 20 minutes of flight due to thunderstorms moving over the field; and ATC having to hold aircraft and vector aircraft for runways changes. We were set up for the localizer 22. About 20 miles from the field we were given a vector off of the arrival again and told ATC was turning the airport around. We were told to expect runway 4; and we set up for the ILS. We were then told to fly a heading towards the southwest and descend and maintain 2000 feet. At the time; we didn't question the 2000 foot descent because we were expecting a short approach; since we were on a downwind close to the FAF (final approach fix). We ended up be left on that heading paralleling the final approach course outbound for a pretty good distance; maybe 15 miles. We were talking about the MSA (minimum sector altitude) of 3100 feet for the approach as we were approaching 3000 feet; because we knew there were towers on the north side of the approach course and we were on the south side of the approach course. Around 2650-2700 feet; ATC asked us what altitude we were going to and asked why we were not level at 3000 feet. I immediately arrested the descent and climbed back up to 3000 feet. ATC believed that he had given us a descent to 3000 feet and I know that he gave us a descent to 2000 feet. The rest of the approach and landing was uneventful.
Original NASA ASRS Text
Title: B737 First Officer reported descending below the Minimum Sector Altitude due to a communication breakdown with ATC.
Narrative: We were flying to [the destination airport] and had several heading; speed; altitude and runway changes within the last 20 minutes of flight due to thunderstorms moving over the field; and ATC having to hold aircraft and vector aircraft for runways changes. We were set up for the Localizer 22. About 20 miles from the field we were given a vector off of the arrival again and told ATC was turning the airport around. We were told to expect Runway 4; and we set up for the ILS. We were then told to fly a heading towards the southwest and descend and maintain 2000 feet. At the time; we didn't question the 2000 foot descent because we were expecting a short approach; since we were on a downwind close to the FAF (Final Approach Fix). We ended up be left on that heading paralleling the final approach course outbound for a pretty good distance; maybe 15 miles. We were talking about the MSA (Minimum Sector Altitude) of 3100 feet for the approach as we were approaching 3000 feet; because we knew there were towers on the north side of the approach course and we were on the south side of the approach course. Around 2650-2700 feet; ATC asked us what altitude we were going to and asked why we were not level at 3000 feet. I immediately arrested the descent and climbed back up to 3000 feet. ATC believed that he had given us a descent to 3000 feet and I know that he gave us a descent to 2000 feet. The rest of the approach and landing was uneventful.
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.