The UK AAIB has released a report on a bizarre incident in which an apparent cockpit display failure on an easyJet Airbus A319 triggered hundreds of master caution warnings in a half-hour span, leading the crew to divert even as it suspected the fault indications were bogus.
The incident occurred in February 2007 on a flight from Barcelona to Liverpool. As the aircraft approached the southern coast of England, a series of fault messages began showing up on the ECAM, including excess exhaust gas temperature warnings on both engines. The crew declared an emergency and diverted to Stansted, and the ECAM continued to generate cautions and aural tones, "too frequently to be read, acted upon, or canceled," the AAIB report said. Investigators later determined that the aircraft generated "around" 460 master cautions in the final 33 minutes of the flight.
The aircraft's voice and data recorders and the suspect avionics were pulled and analyzed, AAIB said. Investigators quickly determined that none of the fault messages were accurate. "Despite extensive on and off-aircraft testing, no hard faults were found that could account for the symptoms experienced during the incident flight," the report said. Airbus said that the type of avionics involved had flown some 5 million hours in the worldwide A320-family fleet without a comparable incident.
Investigators concluded that an intermittent fault in a key circuit board component in one of the aircraft's Display Management Computers (DMCs) was likely to blame. Switching to the back-up (third) DMC would likely have solved the problem, AAIB determined, leading to a recommendation that Airbus make it more clear to flight crews that switching DMCs "may be an appropriate response to abnormal display unit operation."