Boeing 737 8 Max: firm admits technical faults in Ethiopia crash

Aircraft manufacturer Boeing has admitted that a sensor malfunction was to blame for the downing of one of its 737 Max 8 planes in Ethiopia last month.

The statement by Boeing chief executive Dennis Muilenburg marks the “first time” the firm has admitted that its controversial new anti-stall system, rolled out on all 737 Max 8 planes, was a factor in the Ethiopian Airlines crash. The new aircraft crashed just minutes after taking off from Ethiopian capital Addis Ababa on 10 March, killing all 157 people on board.

The circumstances of the accident bore a striking similarity to those of a deadly crash involving another 737 Max 8, operated by lion Lion Air, off the coast of Indonesia in November.

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This crash was later revealed to have been caused by a failure in Boeing’s new Maneuvering Characteristics Augmentation System (MCAS), an anti-stall system introduced on the new planes. The system is designed to automatically bring the nose of the aircraft down if the plane’s Angle of Attack (AOA) sensors detect that the plane is pitched too high, thereby preventing a potentially catastrophic stall in mid-air.

However, an investigation revealed that the Lion Air aircraft’s AOA sensor had fed faulty information to the MCAS, causing the plane’s nose to automatically pitch down. Despite pilots' efforts to prevent repeated nosedives, the aircraft plunged into the Java Sea.

Fears that the same fate may have befallen the Ethiopian Airlines plane have now been confirmed, in a preliminary report by the Ethiopian government. Investigators say that the aircraft nosedived a number of times before crashing, indicating that the MCAS was again responsible for the crash.

Following the release of the report on Thursday, Boeing boss Muilenburg said: "It is apparent that in both flights the manoeuvring characteristics augmentation system, known as MCAS, activated in response to erroneous angle of attack information."

Speaking in a video released by the American firm, he added: "We at Boeing are sorry for the lives lost in the recent 737 Max accidents."

As Business Insider notes, Boeing’s reputation as the “gold standard for aviation is at a make-or-break moment” in the wake of the report, which found that the pilots of the doomed Ethiopian Airlines plane had “repeatedly” followed procedures specifically recommended by Boeing before the crash, and had not made any errors.

In a statement on Thursday, Ethiopian Airlines boss Tewolde GebreMariam said he was "very proud" of the pilots' "high level of professional performance".

Last month, Boeing rolled out a series of software updates and fixes to its automated flight control system on board the Max 8, having been “under pressure from crash victims’ families, airlines, lawmakers in Washington and regulators around the world” to prove that the 737 Max 8 is safe.

Boeing has grounded all 371 planes in the 737 Max fleet, after several countries, including the UK, barred the model from their airspace, The Daily Telegraph reports.

According to ABC News, Boeing has issued a software update that changes the function of MCAS in two significant ways. First, the aircraft manufacturer announced that if the two AOA sensors on the plane offer “widely different readings”, MCAS will deem it a faulty reading and will not activate a pitch-down manoeuvre.

Secondly, the firm added that if a scenario occurs in which the MCAS system is triggered, it will now perform the automated pitch-down only once, allowing the pilots to take control of the plane and negating the possibility of a faulty AOA reading causing the plane to continuously fight against pilot inputs.

However, Boeing is still facing questions from lawmakers over allegations that the firm did not provide adequate training for pilots, and that it is charging airlines extra for “critical” safety features.

Two safety features known as the AOA indicator and the AOA disagree light were not included in the aircraft by Boeing as standard safety features, but were available for an extra charge. The indicator displays the readings of the two sensors and the disagree light activates if those sensors do not agree – information that would have alerted the pilots of the Lion Air and Ethiopian Airlines planes of a faulty AOA reading.

The firm now says that, along with the software updates, the AOA disagree light will come as standard on future models, but it will continue to charge for the AOA indicator.

An investigation of the Lion Air crash in Indonesia revealed that pilots of the 737 Max 8 did not have sufficient information about MCAS. Engadget reports that the aircraft maker has “also produced a new PC-based training program to help pilots better understand MCAS and how to react when the technology is in use”.

German newspaper Deutsche Welle reports that during Boeing’s overhaul of the MCAS systems, the firm this week discovered and subsequently admitted that the 737 Max 8 has “another software error” unrelated the MCAS issue.

Boeing did not disclose the details of the problem, but described it as a “relatively minor issue”.

However, the US Federal Aviation Authority warned that the newly discovered problem could affect aircraft safety, and has made the correction of the issue “another precondition for the aircraft to be allowed to fly again”, the newpaper adds.