Narrative:

Around 300' on final; tower issued instruction; 'go around; aircraft on runway'. They assigned an immediate turnout to a north westerly heading and a level off of 2000'. I hand flew to 2000'; called for VNAV and engaged the autopilot. Being that we were given an early turnout; with VNAV engaged the airplane started an immediate descent to the published restriction of 1100' that we had not crossed due to the early turnout. Upon seeing this; I immediately clicked off the autopilot and returned to 2000' after about a 250' loss of altitude. After calling for lvl chng; straight and level; I reengaged the ap; end of event. On arrival into dfw with approaching front; the airport was switched from a south to a north operation. On vectors with approach ATC was having difficulty with a new controller who I believe was in training. It seemed like every other instruction he was giving was immediately changed by a supervisor. In his defense; there was a passing front and a good amount of traffic saturation. With strong tailwinds until short final; this was probably the first time this controller had seen this type of weather event. On the missed approach; I should have called for level change; not VNAV as we were taken off the published missed procedure which had an 1100' restriction. In my opinion; the controller in training should have been removed and the supervising controller should have taken over after the 3rd correction they had to make in short time. Aircraft were being vectored too close together with the winds the way they were. It seemed like every other instruction the controller in training was giving had to be corrected. On our 2nd approach; we had to query them on what speed they would like because we saw the same issue happening. The controller said 'maintain 190k' to which the supervisor immediately came on and said 'no; maintain 160k.' I immediately configured for final approach and slowed further to 150k. Had we not queried ATC when we did; we would have no doubt had to go around again as traffic ahead was barely clear of the runway as we landed. In a weather event such as this; with dfw congestion; ATC should not have been training or at least should have removed controller in training after a few corrections had to be made. Also; I do not know why the tower had us make an early turnout and a level off lower than the published missed approach altitude. A straight ahead missed or published missed to published missed altitude before vectors to get back in line would have been fine.

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Original NASA ASRS Text

Title: A Flight crew reported conducting a go around and exceeding the assigned altitude then while correcting the auto pilot descended the aircraft below their assigned altitude.

Narrative: Around 300' on final; tower issued instruction; 'go around; aircraft on runway'. They assigned an immediate turnout to a north westerly heading and a level off of 2000'. I hand flew to 2000'; called for VNAV and engaged the autopilot. Being that we were given an early turnout; with VNAV engaged the airplane started an immediate descent to the published restriction of 1100' that we had not crossed due to the early turnout. Upon seeing this; I immediately clicked off the autopilot and returned to 2000' after about a 250' loss of altitude. After calling for LVL CHNG; straight and level; I reengaged the AP; end of event. On arrival into DFW with approaching front; the airport was switched from a south to a north operation. On vectors with approach ATC was having difficulty with a new controller who I believe was in training. It seemed like every other instruction he was giving was immediately changed by a supervisor. In his defense; there was a passing front and a good amount of traffic saturation. With strong tailwinds until short final; this was probably the first time this controller had seen this type of weather event. On the missed approach; I should have called for level change; not VNAV as we were taken off the published missed procedure which had an 1100' restriction. In my opinion; the controller in training should have been removed and the supervising controller should have taken over after the 3rd correction they had to make in short time. Aircraft were being vectored too close together with the winds the way they were. It seemed like every other instruction the controller in training was giving had to be corrected. On our 2nd approach; we had to query them on what speed they would like because we saw the same issue happening. The controller said 'maintain 190k' to which the supervisor immediately came on and said 'no; maintain 160k.' I immediately configured for final approach and slowed further to 150k. Had we not queried ATC when we did; we would have no doubt had to go around again as traffic ahead was barely clear of the runway as we landed. In a weather event such as this; with DFW congestion; ATC should not have been training or at least should have removed controller in training after a few corrections had to be made. Also; I do not know why the tower had us make an early turnout and a level off lower than the published missed approach altitude. A straight ahead missed or published missed to published missed altitude before vectors to get back in line would have been fine.

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.