British Airways A380 Returns to Johannesburg After Air Cycle Machine Failure (G-XLEH)

Incident Overview and Flight Details On the evening of 12 July 2023, British Airways flight BA56, an Airbus A380-841 with registration G-XLEH, was operating from O.R. Tambo International Aerodrome (FAOR) in Johannesburg, South Africa, to Heathrow International Aerodrome (EGLL) in London, United Kingdom. The aircraft departed Runway 03L at 1747Z with 24 crew members and 429 passengers on board. The flight was conducted under instrument flight rules (IFR) in accordance with Part 121 of the Civil Aviation Regulations (CAR) 2011. ## Emergency Declaration and Return Approximately 120 nautical miles north of FAOR, while climbing through 25,170 feet, the crew declared a Mayday due to a strong acrid smell in the cockpit and cabin areas. The crew immediately initiated a descent to 10,500 feet and returned to FAOR. The aircraft landed on Runway 21R approximately 47 minutes after takeoff. Following the landing, the crew shut down the engines, and Aerodrome Rescue and Firefighting (ARFF) personnel inspected the aircraft, finding no external damage. Emergency medical personnel attended to one passenger who was not feeling well, while the remainder of the passengers and crew were unharmed. ## Investigation and Probable Cause The South African Civil Aviation Authority (SACAA) classified the event as a serious incident. The investigation determined that the acrid smell was likely caused by fretting on the turbine end journal bearing of the Air Cycle Machine (ACM) unit 2, which is part of the Air Generation Unit 1. This failure led to the stoppage of the rotating system and associated damage to other components, including the fan end journal bearing, thrust bearings, compressor rotor, and both turbine rotors.