What happened
On 8 March 2024, a Boeing 737-8200, registration EI-HGG, was performing a commercial passenger flight from Poland to London Stansted Airport. During the ILS approach, the aircraft became unstable at a low altitude, prompting the commander to initiate a go-around. The aircraft was flown manually through the missed approach procedure until reaching 3,000 feet.
Following the go-around, the crew prepared for a second approach. To allow the co-pilot to program the Flight Management Computer, the co-pilot handed control of the aircraft back to the commander. During this transition, the crew failed to communicate that the autopilot and autothrust remained disengaged. Consequently, the aircraft entered a descent that went unnoticed by the crew until it had deviated approximately 550 feet from its cleared altitude. The total altitude loss reached 600 feet before the commander corrected the flight path.
The investigation
The AAIB investigation examined the cockpit voice recorder and flight data to reconstruct the sequence of events. The investigation established that the aircraft was being flown manually following the go-around, and the full procedure for re-engaging automated systems had not been completed.
Investigators also reviewed the operator's Flight Crew Operations Manual (FCOM) regarding handover protocols. It was found that the co-pilot did not follow the required verbal format for stating the status of the autopilot and autothrust. Furthermore, the investigation looked into air traffic control (ATC) records, noting that the controller was occupied with coordinating a departure and did not observe the deviation. The investigation also assessed the proximity of a nearby helicopter operating under VFR, which passed within 300 feet and 1.7 nm of the aircraft during the event.