Boeing held off for months on disclosing fault alert on 737 MAX

(Bloomberg) — Boeing Co. knew months before a deadly 737 Max crash that a cockpit alert wasn’t working the way the company had told buyers of the single-aisle jetliner. But the planemaker didn’t share its findings with airlines or the Federal Aviation Administration (FAA) until after a Lion Air plane went down off the coast of Indonesia in October, according to a Boeing statement as it provided additional details of an issue that first came to light last week.

Boeing’s latest disclosure raises new questions about the 737 Max’s development and testing — and the company’s lack of transparency. The alert was supposed to flash when two angle-of-attack vanes sent conflicting data about the relation of the plane’s nose to the oncoming air stream. Boeing had told airlines and pilots that the so-called AOA disagree warning was standard across the Max fleet, as on a previous generation of 737 jets.

The inactive alert was later deemed to be “low risk” by the FAA’s Corrective Action Review Board, the regulator said Sunday. “However, Boeing’s timely or earlier communication with the operators would have helped to reduce or eliminate possible confusion,” the FAA said.

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Boeing’s transparency is questioned

Boeing engineers discovered the discrepancy “within several months” of the initial Max deliveries in May 2017, the company said. The disclosures followed criticism from airlines and crash victims’ relatives that Boeing hasn’t been forthcoming about issues with the 737 Max, which has been grounded since a second crash in March, in Ethiopia.

The two disasters killed 346 people.

The manufacturer’s own experts reviewed the issue and “determined that the absence of the AOA Disagree alert did not adversely impact airplane safety or operation,” according to the Boeing statement. The company’s review board decided the setup was acceptable until the two alerts could be unlinked with the next planned software update for the plane’s display system.

Boeing said it also told the FAA that company engineers had identified the issue in 2017, along with the findings from their internal review process. In December, a safety review board convened by the manufacturer confirmed that the absence of a functional AOA disagree light didn’t present a safety issue.

Before the Max returns to service, Boeing plans to issue a software update that will allow the AOA disagree light to operate as a standalone feature. Boeing has separately been working to finalize a redesign of the software, known as MCAS, that was mistakenly triggered by the faulty sensor readings. The last major milestone is an FAA certification flight that the company expects to conduct shortly.

Related: Probe of FAA’s oversight of Boeing 737 began before second crash

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