A B777 flight carrying 235 passengers and crew was forced to turn back when the pilots became starved for oxygen in the cockpit, forcing them to open the cockpit door and don oxygen masks.
The serious incident took place aboard a Seattle-bound British Airways B777. The flight was forced to return to London Heathrow airport. A report by Britain’s Air Accident Investigation Branch (AAIB), just released, has found the flight deck door was open for about 15 to 20 minutes, in contravention of anti-terrorism provisions – but it needed to be open. The first priority is breathing.
The pilots used oxygen masks for their main air supply and air from the plane’s cabin, entering through the door, as a backup. Two cabin crewmembers and “the ‘heavy’ co-pilot” stood by the front of the open cockpit door for security while the crisis continued, the report said.
Instead of continuing the transatlantic flight, which took place in March 2015, the crew decided to turn back to Heathrow wearing their oxygen masks as their main air supply.
The pilots became aware of low airflow in the cockpit during taxiing, but it got worse after take-off and climbing. What’s more, the cabin was getting hotter. At a cruising altitude of 34,000 feet, flight crew were compelled to take breaks outside the flight deck, as otherwise they experienced “headache, nausea, light-headedness, a constant urge to take deep breaths and difficulty maintaining concentration”.
The same aircraft had been investigated for similar problems in February and engineers thought they had fixed the problem – but evidently not.
The report continues: “The decision was made to return to Heathrow with all three crew members on oxygen and the cockpit door closed.
“An uneventful landing was carried out and it was found that debris in the conditioned air duct below the cockpit floor was almost completely blocking airflow to the flight deck. The source of the debris and how long it had been present could not be determined.”
The report concluded that the problems “were almost certainly caused by the migration of debris which had accumulated in the underfloor ducting from an unknown source at a time which could not be pinpointed.”
BA’s internal investigation identified two potential actions which could help prevent recurrences of a similar nature:
- Publicising the event throughout the airline to improve awareness
- Requesting the aircraft manufacturer clarify references in their Fault Isolation
Manual (FIM) to airflow being ‘satisfactory’ or ‘not satisfactory’.
Technical records show that pilots have reported similar airflow problems across the B777 fleet but they were “sufficiently rare that it could be concluded that such problems were not endemic”, the report stated.
Written by Peter Needham