What happened
On the evening of 12 July 2023, a British Airways Airbus A380-841, registration G-XLEH, departed O.R. Tambo International Aerodrome (FAOR) for London Heathrow. The flight was carrying 429 passengers and 24 crew members. Shortly after takeoff, while climbing through approximately 25,170 feet, the flight crew noticed a strong, burning, and acrid odor permeating both the cockpit and the passenger cabin.
In response to the deteriorating air quality, the pilot-in-command declared a Mayday and requested an immediate return to Johannesburg. The crew initiated a descent to 10,500 feet and began a turn back toward the airport. During the descent, the crew noted a haze in the upper and main decks and reported a grinding noise originating from the number 2 engine.
After approximately 47 minutes of flight time, the aircraft landed on Runway 21R. The crew brought the aircraft to a halt on the runway and shut down the engines. While emergency medical personnel treated one passenger for an unspecified ailment, no other injuries were reported among the passengers or crew. Aerodrome rescue and firefighting teams inspected the exterior of the aircraft but found no visible damage.
The investigation
The South African Civil Aviation Authority (SACAA) AIID conducted an investigation into the serious incident. The inquiry examined the flight data, cockpit communications, and the mechanical state of the aircraft's systems. Investigators focused on the source of the fumes and the mechanical failure within the engine components that led to the emergency declaration.
Findings
- The primary cause of the emergency was the failure of the Air Cycle Machine (ACM) unit 2, which is a component of the Air Generation Unit 1.
- The acrid smell reported by the crew was likely caused by fretting on the turbine end journal bearing.
- The mechanical failure involved the stoppage of the rotating system due to damage to the compressor rotor, both turbine rotors, the thrust bearings, and the fan end journal bearing.