It was the second crash of a Max jet in less than six months and led to the worldwide grounding of the newest version of what had been Boeing’s best-selling plane.
The interim findings came as families of the victims from around the world gathered in Ethiopia for events commemorating the crash anniversary.
According to the report, the “differences” training provided to the airline’s pilots — meant to instruct them on how the Max would behave differently than an earlier version of the 737 — was found to be “inadequate.” A key cockpit alert did not work, contradicting a Boeing manual. And Boeing and its U.S. regulator did not properly consider how things might go wrong with a new automated feature, known as the maneuvering characteristics augmentation system, or MCAS, the report said. MCAS has been cited as a contributing factor in both 737 Max crashes.
“We continue to extend our heartfelt sympathies to the families and loved ones of Ethiopian Airlines Flight 302,” Boeing said in a statement.
“Boeing continues to provide technical assistance in support of the investigation, at the request of and under the direction of the U.S. National Transportation Safety Board, the accredited representative for the United States,” the company said. “We look forward to reviewing the full details and formal recommendations that will be included in the final report from the Ethiopian Accident Investigation Bureau.”
Federal Aviation Administration officials said they are reviewing the interim report but emphasized that any final actions must be driven by a full review of all factors that may have contributed to the crash.
“With the one year anniversary of the loss of Ethiopian Airlines Flight 302 upon us, the professionals of the FAA want to again express sincere condolences to the families of those who were lost,” the agency said in a statement. “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.”
Unlike the final investigative report into the first Max crash, a Lion Air flight that crashed off the coast of Indonesia on Oct. 29, 2018, the report from Ethiopian investigators focuses almost exclusively on flaws in the 737 Max’s design. The report lists 16 factual findings and makes a half-dozen safety recommendations; it does not make formal conclusions about the cause of the crash.
The final report on the Lion Air crash included a complicated set of nine connected causes, including poor keeping of maintenance records by the airline, an angle-of-attack vane installed on the plane that was improperly calibrated at an American repair shop and faulty assumptions by Boeing of how pilots would react to the triggering of MCAS.
Ethiopian officials and executives at Ethiopian Airlines have pushed back against any allegations that pilot error played a role in the crash. The airline was one of the few in the world that had a 737 Max simulator at the time of the crash.
Whether pilots should have been able to avert disaster caused by a faulty MCAS system has been a theme underlying commentary from U.S. officials and others as the investigations have continued. Investigators in both Indonesia and Ethiopia think that MCAS, acting on erroneous data from a malfunctioning angle-of-attack sensor, repeatedly pushed the planes’ noses down as pilots, who were unaware of the system, struggled to regain control.
Under congressional questioning last year, Daniel K. Elwell, a top FAA official, said the Ethiopian pilots “didn’t adhere” to an emergency directive issued by the FAA in November 2018 and failed to control the plane's speed as needed. He said aviation crashes always have “three or four or five links in the chain, any one of which, if it hadn't gone wrong, the plane would have survived.”
Some Republicans in Congress have questioned the skills and training of Ethiopian and other international pilots, while other observers have dismissed suggestions that U.S. pilots would have been able to prevent the crash. At a congressional hearing last year, Capt. Chesley B. “Sully” Sullenberger III said it was “unlikely” other crews would have performed differently.
Safety experts said the crashes did point to weaknesses in how “human factors” are considered in complex technical and automated environments.
In a report last year, the NTSB said Boeing did not sufficiently consider the effect that a cacophony of alarms shaking, clacking and lighting up throughout the cockpit would have on pilots struggling to prevent disaster caused by an MCAS malfunction.
The safety agency said the FAA should require Boeing to perform a more rigorous analysis of how warning systems might overwhelm pilots, echoing the Ethiopian authorities’ call in their interim report for the FAA to better consider potential hazards.
Ethiopian authorities also recommended that training simulators “need to be capable of simulating” the type of incident that led MCAS to misfire.
The NTSB said Monday that it would “continue to assist the [Ethiopian Aircraft Accident Investigation Bureau] as they work toward a comprehensive final report.”
The two Max crashes killed a total of 346 people and led to renewed scrutiny of the FAA’s process for certifying the jetliner, the newest version of a plane that began operating in the late 1960s.
Boeing has been working on changes to the Max, including software fixes to MCAS and an updated pilot training program, to win approval from the FAA to return the plane to service, which the company expects to happen midyear. The events have also damaged Boeing’s reputation and cost the company billions. The aerospace giant fired its chief executive, Dennis Muilenburg, in December and stopped production of the Max in January.
In a preliminary report last April, Ethiopian investigators said MCAS was triggered by an erroneous reading taken from one of the plane’s angle-of-attack indicators. The system, designed to push the plane’s nose down if it appeared it was at risk of stalling, was a new addition to the 737 Max. It was designed to compensate for changes to the plane’s design, which included larger engines placed farther forward on the jetliner.
That conclusion is bolstered in the interim report released Monday, which noted that erroneous information from the angle-of-attack sensor also caused the stick shaker — a vibration in the pilots’ controls that warns of an impending stall — to activate. It also triggered MCAS, which repeatedly forced the plane’s nose down, even as the pilots struggled to regain control. In all, MCAS activated at least four times.
The discrepancy between the two angle-of-attack indicators was stark. The devices measure the relative position of the nose of the airplane and the oncoming wind, vital readings for safe flight. The left indicator reached 74.5 degrees, but the right one maxed out at 15.3 degrees, a vast disconnect that fed bad information into the plane’s powerful flight control feature, MCAS.
Yet Boeing, during its assessment of potential hazards, did not simulate the specific things that could lead MCAS to keep trying to force the plane’s nose down, including wildly divergent angle-of-attack readings, the report said.
That shortcoming led to others, the report said, noting that pilots faced a barrage of “additional flight deck effects” — including numerous and varied alerts. But those warnings “were not simulated and were not documented” as safety assessments of the aircraft were being done, the report said.
The Ethiopian investigators recommended the FAA should guarantee comprehensive safety work is performed before planes are first certified safe to fly.
“The regulator shall confirm all probable causes of failure have been considered during functional hazard assessment,” the report said.
Last week, House Democrats released details of their investigation into the FAA’s certification process and into Boeing’s company culture. The report said there was a “culture of concealment” at Boeing and that the FAA’s oversight of the manufacturer was “grossly inefficient.”