British Airways flight stall warnings came before a mayday call on 6 July as a British Airways Airbus A320 approached Heathrow Airport from Dusseldorf airport in Germany. The aircraft landed without further incident.
The AAIB said: "The AAIB is investigating a serious incident involving a commercial aircraft which occurred on 6 July on approach to Heathrow airport." British Airways said it was "assisting the AAIB with its investigation" and was "not legally able to comment further at this stage."
The BEA said that as the plane approached Heathrow, a data system failure triggered a stall warning, and the crew then flew the aircraft in alternate law. A second stall warning followed at 3,000 feet, after which the urgency call was upgraded to mayday.
David Gleave on mayday calls
David Gleave, an aviation safety investigator, said there are different forms of mayday calls and that sending an urgency message was not unusual. He said: "You could have sick passengers on board who need urgent medical attention… so it's up to the captains' discretion as to what they call, but its very unusual for it to be a significant failure on board the aeroplane."
That leaves the final issue in plain view: the aircraft got down safely, but the sequence of warnings, the switch into alternate law, and the move from urgency call to mayday all point to a technical failure that the AAIB is now examining by correspondence rather than by sending a field team.
