The final report by Indonesian investigators into the crash of a Boeing 737 Max plane flown by Indonesia’s Lion Air that left 189 people dead has found that problems with Boeing’s design, the airline’s maintenance of the jet and pilot errors contributed to the disaster.
The report into the October 2018 crash criticised the US planemaker’s new anti-stall system, MCAS, that automatically pushed the plane’s nose down, leaving pilots fighting for control.
The 737 Max’s MCAS system is also at the centre of separate investigations into an Ethiopian Airlines crash in March that killed 159 people. Boeing’s 737 Max planes were grounded worldwide following the crashes.
The MCAS should be redesigned to include a backup and all systems that can take over flight control should receive closer scrutiny during certification, according to the final report published by the investigators on Friday.
“The investigation considered that the design and certification of this feature was inadequate,” the report said. “The aircraft flight manual and flight crew training did not include information about MCAS.”
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The report also found that Boeing failed to detect a software error resulting in a warning light not working and failed to provide pilots with information about the flight control system.
“The absence of guidance on MCAS […] in the flight manuals and pilot training made it more difficult for flight crews to properly respond to uncommanded MCAS,” said a presentation shown by investigators in Jakarta on Friday.
Boeing has already said it plans to remake the system and provide more information about it in pilot manuals. The company still expects the troubled 737 Max jet to return to service by the end of the year.
The final report said the first officer onboard was unfamiliar with procedures and had shown issues handling the aircraft during training.
The report also found that a critical sensor providing data to an anti-stall system had been miscalibrated by a repair shop in Florida and there were strong indications it had not been tested during installation by Lion Air maintenance staff.
Lion Air should have grounded the jet following similar faults on the plane’s previous flight, the report said, adding that 31 pages were missing from the airline’s October maintenance logs. Lion Air did not respond to a request for comment.
The Indonesian investigators also made recommendations that regulators, including the US Federal Aviation Administration and its counterpart in Indonesia, improve their oversight over certification and maintenance.
The report is one of multiple investigations, including those by US regulators and Congress, faced by Boeing into the crashes of what was previously its most popular plane.
The crisis has led Boeing to set aside $4.9bn (£3.8bn) to cover the costs of the groundings. On Wednesday, the company announced it made $20bn in revenues during the third quarter of the year, down by more than a fifth from the previous year. Profits fell by more than 50%.
On Friday, Boeing said it had implemented three new software fixes for the MCAS issues that would mean it was not dependent on a single sensor and that would allow a pilot to override it. Boeing has completed a certification test flight with the updates in place.
Dennis Muilenburg, Boeing’s chief executive officer, who had the chairmanship removed this month, said: “On behalf of everyone at Boeing, I want to convey our heartfelt condolences to the families and loved ones of those who lost their lives in these accidents. We mourn with Lion Air, and we would like to express our deepest sympathies to the Lion Air family.”
“We are addressing [Indonesia’s National Transportation Safety Committee’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.”
Boeing still expects to regain regulatory approval for the 737 Max “in the fourth quarter of 2019”. The company hopes to increase its rate of production of the aircraft – which it cut in the aftermath of the flight bans – from 42 per month to 57 per month by late 2020.
