ADDIS ABABA (Reuters) - Ethiopian investigators singled out faulty systems on a Boeing (BA.N) 737 MAX plane in an interim report on last year’s Ethiopian Airlines crash that killed 157 people, piling pressure on the U.S. jetmaker on the eve of the disaster’s anniversary.
The accident, following the 2018 crash of the same model plane in Indonesia killing 189 people, led to the grounding of Boeing’s 737 MAX worldwide, wiped billions off the company’s value and sparked hundreds of lawsuits from bereaved families.
Monday’s report focused purely on technical matters and identified no issues with the airline or pilots’ handling of the brand-new 737 MAX, which crashed shortly after take-off.
Inaccurate sensor readings activated the MCAS anti-stall system that pushed the plane down as pilots struggled to right it, the report said. The fully loaded jet burrowed into a field with its nose down 40 degrees and dropping at 500 feet a second.
“Most of the wreckage was found buried in the ground,” it said.
The interim report here bolstered findings of Ethiopia's initial assessment, which linked the crash to a Boeing automated system. It said two sensors recording the plane's angle - known as the "angle of attack" or AOA - differed in readings by 59 degrees.
Under the plane’s design, regulators have found that flight computers were only capable of consulting one AOA sensor at a time, meaning there was no backup beyond the presence of trained crew, due to miscalculation of the risks of failure.
The 130-page report devoted some 20 pages to listing a cascade of problems caused by the loss of accurate AOA data, including flight computer and throttle settings, signaling where Ethiopian authorities will argue the root cause lies.
But the U.S. Federal Aviation Administration adopted a cautious stance and suggested it would consult other reports, while remaining open to human as well as technical factors.
“We believe it’s important to have the full final report to evaluate it against other independent reports so that we might fully understand all of the factors - both mechanical and human - that played a role in this tragic loss of life,” it said.
The Ethiopian interim report contrasted with a final report into the Lion Air crash by Indonesia which faulted Boeing’s design of cockpit software on the 737 MAX but also cited errors by airline workers and crew.
Safety experts say most airliner accidents are caused by a cocktail of factors.
Ethiopian authorities did not release the report at a press conference, and neither the transport ministry nor the airline answered calls seeking comment.
In a short statement, Boeing reiterated condolences to relatives of victims and said it looked forward to seeing full details and formal recommendations in Ethiopia’s final report.
Passengers from 33 nations had been aboard the plane and families from many nations gathered in the capital of Addis Ababa ahead of a memorial at the crash site on Tuesday.
Some welcomed the report, but others said they were too consumed by grief to read it.
“We wish the report had come earlier or after this moment as we are now in a moment of grief, and want to focus on remembering our loved ones,” said Zekarias Asfaw Shankut, 42, who lost his brother. “Now it is actually a distraction.”
The Ethiopian report criticized Boeing for “inadequate” training for pilots flying the new model because it had not included scenarios where MCAS was erroneously activated.
Some industry experts have questioned certain aspects of the pilots’ handling of flight ET302, including the engines being left at hard-to-manage take-off power, while acknowledging they were grappling with overwhelming physical forces and flawed control software. The airline strongly denies any pilot error.
But the report said the throttles did not move during the flight because the flight computer was looking at wrong data.
The report backed safety recommendations already underway, including modifications to sensors and anti-stall MCAS software. Boeing recently endorsed calls for more costly simulator training after holding out for months against it.
The U.S. House Transportation Committee on Friday faulted the FAA’s approval of the plane and Boeing’s design failures, saying the two 737 MAX flights were “doomed”.
Writing by Katharine Houreld; Additional reporting by Katharine Houreld in Nairobi, David Shepardson in Washington and Tim Hepher in Paris; Editing by Andrew Cawthorne and Mark Potter