Narrative:

We were given the tellr 2 RNAV runway 34R ILS transition. Den had just changed from south to north flow; we received a new clearance for the tellr runway 34 while still at cruise. Once talking to approach; the controller was very busy. The arrival had a 40 to 30-knot tailwind all the way down. Approximately 10 miles from cragg we were vectored off the arrival and told to maintain 210 knots. We were then on a shorter ground track; asked to slow and had a 40-knot tailwind. We used all available drag devices to slow and descend but were still high. We leveled at 13;000'; assigned; and due to communication congestion; we were not able to descend on schedule. All of these made us high on final. We asked for turns on final to try to correct; but were unable to correct. I recollect that approach asked 'do you want to try again?' we understood that to mean go missed approach; and agreed with ATC. This began the 'threats' section of this as soon as possible. The non-standard radio call of 'do you want to try again'. Followed by 'turn right 020' left me confused on altitude assignment. We were in a visual descent towards the runway at 9200' (approximately). The altitude bug was at 10;000'; and no perceived altitude assignment. So we climbed to 10;000' while in an assigned left turn to a heading of 170. I did this because 10;000' was the last ATC clearance and was a good safe altitude in that area. With the controller being so busy; I took appropriate action and wanted to ensure aircraft control and; therefore what I perceived as the safest course of action. The first officer and I were not clear on if we were assigned 9000' or 10;000'. I chose 10;000' due to the altitude bug set there in our AC. I had to make a quick decision and felt 10;000' was the safest; I cleared our flight path and we climbed. I do not believe we were assigned any altitude on missed but we wanted to file to make sure we explained ourselves. Preventative measures: this is tough; den had just changed runways; there was severe turbulence on the arrival; and the tailwind on final. When we landed it seemed that den realized the situation and was already changing back to south flow. When I saw the tailwind and the short vector; I used the risk mitigation mindset to help prepare for the possibility of going around. I can understand how busy the approach controller was and he did an excellent job! But in the maintain aircraft control; risk mitigation mindsets; I wanted to be able to help him out by making sure we didn't put ourselves in an unsafe situation. So with runway change; turbulence; weather; tailwind; etc.; I don't have a suggestion; this is just aviation. The only thing I would mention is the 737 is very hard to descend and slow; even harder with a tailwind and turbulence. A longer ground track (not shorter) is the best way to go during these scenarios. On missed approach keep standard communication '(call sign) execute a missed approach; heading xx climb maintain xx altitude.' let us respond; then 'expect vectors to ILS runway 34R.' this scenario had three turns in less than 30 seconds; with some hesitation that caused CRM to break down.

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Original NASA ASRS Text

Title: B737 flight crew reported confusion over their assigned altitude on a go-around from an unstabilized approach to DEN.

Narrative: We were given the TELLR 2 RNAV Runway 34R ILS transition. DEN had just changed from south to north flow; we received a new clearance for the TELLR Runway 34 while still at cruise. Once talking to Approach; the controller was very busy. The arrival had a 40 to 30-knot tailwind all the way down. Approximately 10 miles from CRAGG we were vectored off the arrival and told to maintain 210 knots. We were then on a shorter ground track; asked to slow and had a 40-knot tailwind. We used all available drag devices to slow and descend but were still high. We leveled at 13;000'; assigned; and due to communication congestion; we were not able to descend on schedule. All of these made us high on final. We asked for turns on final to try to correct; but were unable to correct. I recollect that Approach asked 'Do you want to try again?' We understood that to mean go missed approach; and agreed with ATC. This began the 'threats' section of this ASAP. The non-standard radio call of 'Do you want to try again'. Followed by 'Turn right 020' left me confused on altitude assignment. We were in a visual descent towards the runway at 9200' (approximately). The altitude bug was at 10;000'; and no perceived altitude assignment. So we climbed to 10;000' while in an assigned left turn to a heading of 170. I did this because 10;000' was the last ATC clearance and was a good safe altitude in that area. With the controller being so busy; I took appropriate action and wanted to ensure aircraft control and; therefore what I perceived as the safest course of action. The First Officer and I were not clear on if we were assigned 9000' or 10;000'. I chose 10;000' due to the altitude bug set there in our AC. I had to make a quick decision and felt 10;000' was the safest; I cleared our flight path and we climbed. I do not believe we were assigned any altitude on missed but we wanted to file to make sure we explained ourselves. Preventative Measures: This is tough; DEN had just changed runways; there was severe turbulence on the arrival; and the tailwind on final. When we landed it seemed that DEN realized the situation and was already changing back to south flow. When I saw the tailwind and the short vector; I used the risk mitigation mindset to help prepare for the possibility of going around. I can understand how busy the Approach Controller was and he did an excellent job! But in the maintain aircraft control; risk mitigation mindsets; I wanted to be able to help him out by making sure we didn't put ourselves in an unsafe situation. So with runway change; turbulence; weather; tailwind; etc.; I don't have a suggestion; this is just aviation. The only thing I would mention is the 737 is very hard to descend and slow; even harder with a tailwind and turbulence. A longer ground track (not shorter) is the best way to go during these scenarios. On missed approach keep standard communication '(Call sign) execute a missed approach; heading XX climb maintain XX altitude.' Let us respond; then 'expect vectors to ILS Runway 34R.' This scenario had three turns in less than 30 seconds; with some hesitation that caused CRM to break down.

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.