JAKARTA (REUTERS, AFP) - Mechanical and design issues contributed to the crash of a Lion Air 737 Max jet last October, Indonesian investigators told victims’ families in a briefing on Wednesday (Oct 23) ahead of the release of a final report.
Contributing factors to the crash of the new Boeing jet, which killed all 189 people on board, included incorrect assumptions on how an anti-stall device called the Manoeuvring Characteristics Augmentation System (MCAS) functioned and how pilots would react, slides in the presentation showed.
Reliance on a single angle-of-attack sensor made the MCAS system more vulnerable to failure, while the sensor on the plane that crashed had been miscalibrated during an earlier repair, according to the slides.
A Boeing spokeswoman declined to comment on the briefing, saying, "as the report hasn’t been officially released by the authorities, it is premature for us to comment on its contents."
A Lion Air representative declined to comment.
The briefing slides said a lack of documentation about how systems would behave in the crash scenario, including the activation of a "stick shaker" that warned pilots of a dangerous loss of lift, also contributed.
The flight crew also faced multiple distractions and "deficiencies" in manual control of the aircraft and communication, the slides added.
The 737 Max was grounded worldwide after a second deadly crash in Ethiopia in March 2019.
The planemaker is due to release its third-quarter financial results later Wednesday.
Last month, a plaintiffs' attorney told AFP that Boeing had so far reached settlements with 11 families of victims in the Lion Air crash.
The briefing comes after Boeing on Tuesday replaced the chief of its commercial plane division, the most significant executive departure since the 737 Max grounding plunged the company into crisis seven months ago.
The crashes and grounding of the Max have dented Boeing's reputation, with the crashes having already cost the US planemaker billions of dollars and sparked calls to reform its corporate culture and transparency issues.
Uncertainty continues to cloud Boeing's timeframe for returning the single-aisle jet to service.
A report released by international regulators said the US Federal Aviation Administration lacked the manpower and expertise to fully evaluate the jet's MCAS system when it certified the plane.
Boeing faced new scrutiny following text messages from November 2016 in which a Boeing pilot described the MCAS during a simulation as "running rampant" and behaving in an "egregious" manner.
Boeing shared the messages with the Department of Justice in February.
But the FAA learned of their existence only recently and publicly criticised Boeing for withholding the documents.
The aviation giant, which faces scores of lawsuits, said earlier this year it would spend US$100 million (S$136.41 million) on communities and families affected by the 737 Max disasters.