A321, en-route, near Pamplona Spain, 2014

A321, en-route, near Pamplona Spain, 2014

Summary

On 5 November 2014, the crew of an Airbus A321 temporarily lost control of their aircraft in the cruise and were unable to regain it until 4000 feet of altitude had been lost. An investigation into the causes is continuing but it is already known that blockage of more than one AOA probe resulted in unwanted activation of high AOA protection which could not be stopped by normal sidestick inputs until two of the three ADRs had been intentionally deactivated in order to put the flight control system into Alternate Law.

Description

On 5 November 2014, an Airbus A321 [D-AIDP] being operated by Lufthansa on a passenger flight from Bilbao to Munich was just reaching the top of climb to cruise at FL310 in day VMC when abnormalities in the airspeed display prompted the crew to disengage the Autopilot. A steep descent which could not initially be stopped by crew input to the flight controls then followed and 4000 feet of altitude was lost before flight path control could be regained, albeit using abnormal flight control inputs. Advice by ACARS from Company Maintenance on simplifying control facilitated the completion of the flight, uneventfully, to destination.

Investigation

After delegation of authority from the State of Occurrence on 11 November, an Investigation was commenced by the German Bundesstelle für Flugunfalluntersuchung (Germany) (BFU) and is ongoing. Data from the SSFDR and the 2-hour SSCVR has been successfully downloaded and has been central to the Investigation, along with aircraft and maintenance documentation and "various witness' statements".

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