A BAW British Airways Airbus A320-200, registration G-EUUN performing flight BA-919 from Dusseldorf (Germany) to London Heathrow,EN (UK), was on approach to Heathrow's runway 27L when the aircraft suffered an Air Data Reference failure causing the aircraft to change to Alternate Law, the failure also triggered a stall warning prompting the crew to declare PAN PAN. The aircraft went around and entered a hold, then positioned for another approach to runway 27L when another stall warning occurred at 3000 feet resulting in an abrupt recovery maneouver, the aircraft descended to about 2200 feet and deviated to the left of the approach path before returning onto the glidepath and re-aligning with the runway center line. The aircraft landed safely about 30 minutes after aborting the first approach.
The AAIB opened an investigation into the serious incident reporting: "During the approach phase, an ADR failure triggered a stall warning; the crew flew the aircraft under alternate law and declared a PAN. A further stall warning occurred at 3,000 feet, accompanied by a potentially abrupt recovery maneuver, resulting in the PAN being changed to a MAYDAY. The aircraft landed without further incident."
