A British Airways Airbus A320-200, registration G-EUUK performing flight BA-811 from Copenhagen (Denmark) to London Heathrow,EN (UK), had boarded the passengers, the crew started the APU, about one minute after activating the APU bleed air the right hand air conditioning pack was activated when immediately a strong odour of sweaty socks occurred. The left pack was activated, a similiar but lesser odour was noticed. Both packs were deactivated and the cockpit windows opened to ventilate the aircraft. The odour dissipated, the aircraft was able to depart with a delay of 30 minutes. On approach to Heathrow's runway 27R while descending through 5000 feet the odour of sweaty socks was again detected throughout the aircraft. The crew worked the related checklists and the smell dissipated from the flight deck, but remained in the cabin. The aircraft landed without further incident, medical and engineering support was requested.
The AAIB, in their bulletin for another occurrence, see Accident: British Airways A320 at London on Sep 23rd 2019, smoke in cabin, mentioned this occurrence writing:
The aircraft had been parked overnight at Copenhagen Airport and was scheduled for a return flight to Heathrow on the morning of 1 October 2019. After completion of boarding the APU was started and run for one minute with its air bleed selected off. The air bleed was then selected on, and after a further minute, the right air conditioning pack was selected on. Almost immediately a strong odour, described as being like sweaty socks became apparent on the flight deck. The left pack was selected on and a similar odour but to a lesser extent was apparent throughout the cabin. Both packs were selected off and the cockpit windows opened to vent the fumes which dissipated in approximately seven minutes. After a 30 minute delay, the aircraft preparations for departure were completed and the aircraft flew without incident until the final approach to Heathrow.
As the aircraft commenced final approach to Runway 27 at Heathrow, at about 5,000 ft, a sweaty sock odour was detected throughout the aircraft. The smoke and fumes abnormal and emergency procedures were completed and, within 60 to 90 seconds, the fumes dissipated from the flight deck. Fumes were still apparent in the cabin, so engineering and medical assistance was sought. Some of the cabin crew reported a fuzzy headed feeling, tingling throats and nasal congestion. This alleviated in fresh air and medical assistance was not required.
G-EUUK pilots observation
The pilots of G-EUUK had noted that another fume event had taken place on the previous afternoon during descent into Heathrow and was recorded in the maintenance log. The log showed that the prescribed post event work pack had been completed and the aircraft had been released to service. It then flew to Copenhagen without incident prior to its overnight stop.