After initially climbing away as expected during the go-around, the aircraft then descended for over 30 seconds reaching a minimum radio altitude of 457 ft. Simultaneously, the crew and the controller realised the aircraft was not climbing away as they expected. The crew corrected the flight path and the aircraft was vectored for a further uneventful approach.
The loss of altitude occurred because the target altitude on the Mode Control Panel was set to the minimum altitude for the approach having not been set to the missed approach altitude before the go-around. Neither crew member noticed initially that the aircraft was descending.
The operator has taken two safety actions as a result of this incident. They have used this incident as part of their annual recurrent ground school to highlight the risks of rushed and unstable approaches. They are also continuing to work on their flight data monitoring programme so that similar approaches will be identified more rapidly and easily in future.