The final investigation report of Lion Air Flight 610 by Indonesia’s National Transportation Safety Committee (KNKT) has found a series of events contributed to the loss of control of the aircraft in an accident that killed all 189 people on board, with the investigators noting faults with Boeing’s MCAS software on the 737 MAX, along with errors by airline staff.

Investigators criticised the anti-stall system, MCAS, which triggered during the flight, automatically pushing the nose of the aircraft down and contributing to difficulties in controlling the aircraft. The report considered the “design and certification of this feature was inadequate.” The report also found the aircraft flight manual and flight crew training did not include information about the feature.

Investigators also found that there was a “lack of clear and effective communication” between the flight crew which contributed to the struggle to control the aircraft and following faults on earlier flights the day before the accident, the aircraft should have been grounded. It appears that the co-pilot was unfamiliar with the recovery procedures and had encountered difficulties during his training. The report indicates that although the captain managed to lift the nose of the aircraft up 20 times, the first officer was unable to complete the checklist that would have deactivated the MCAS.

Through the investigation, it was found that an Angle of Attack (AOA) sensor, which provides data to the MCAS anti-stall system, had been miss-calibrated in Florida, and according to Reuters the report found indications that it was not tested during installation by Lion Air’s maintenance staff. The report also said a “lack of an API written procedure” may have contributed to this and argued this “indicates inadequacy of FAA oversight.”

“We are addressing the KNKT’s safety recommendations, and taking actions to enhance the safety of the 737 MAX to prevent the flight control conditions that occurred in this accident from ever happening again,” commented Boeing president and CEO Dennis Muilenburg.

The company’s engineers have been working with the US Federal Aviation Administration and other global regulators to make software updates and other changes, taking into account the information from the investigation. Boeing also said: “Since this accident, the 737 MAX and its software are undergoing an unprecedented level of global regulatory oversight, testing and analysis.”

The company has redesigned the way the AOA sensors work with MCAS and in future the MCAS will compare information from both AOA sensors before activating and in addition, will only turn on if both AOA sensors agree, will only activate once in response to erroneous AOA and will be subject to a maximum limit that can be overridden with the control column.
Boeing is also updating crew manuals and pilot training.

“Safety is an enduring value for everyone at Boeing and the safety of the flying public, our customers, and the crews aboard our airplanes is always our top priority,” Muilenberg said.

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