ADDIS ABABA, Ethiopia — Ethiopian investigators said Thursday that the pilots of a doomed Ethiopian Airlines flight repeatedly followed procedures recommended by Boeing but were still unable to recover before the plane dived into the ground last month.
The crash of Ethiopian Airlines Flight 302 on March 10 followed the unrecoverable nose-dive almost five months earlier of another jet of the same model, a Boeing 737 Max 8, in Indonesia. Indonesian investigators have implicated a malfunctioning automated anti-stall program in that disaster, in which the plane’s computer system appeared to override pilot directions based on faulty data.
The investigators’ initial findings Thursday, based on analysis from 18 Ethiopian and international investigators and information from the jet’s flight data recorder and cockpit voice recorder, were released several hours after a news conference held by Ethiopia’s minister of transportation.
The report said that pilot-side sensor readings connected to the computer system varied wildly and affected everything from their understanding of the plane’s pitch to its airspeed.
“These guys are executing the check list,” Dennis Tajer, a spokesman for the American Airlines pilot union, said of the Ethiopian pilots after reviewing the report. “They were identifying the problem and taking swift action.”
The initial findings are likely to heighten scrutiny of the Max, Boeing’s newest and top-selling generation of jets. Since the Ethiopian Airlines crash, airlines worldwide have grounded their Max fleets amid concerns over the apparent propensity of the stall-prevention system, known as MCAS, to malfunction when fed erroneous data.
Dagmawit Moges, Ethiopia’s minister of transportation, said that the flight crew repeatedly followed procedures recommended by the plane’s manufacturer “but was not able to control the aircraft.”
Moges recommended that the plane’s flight control system be reviewed by the manufacturer. And she suggested that the aviation authority ensure that a review of the aircraft flight control system be adequately addressed by the manufacturer before the aircraft was released for operations.
During the news conference, Moges did not specify who the manufacturer was or to which aviation authority she was referring. Nor did she or the report mention MCAS by name.
After the conference, however, Moges told The New York Times that MCAS had been active during the flight’s brief journey. “The pilots have turned the MCAS on and off, but I can’t say how many times because we will find that out when we have the final report,” she said.
The crash of Ethiopian Airlines Flight 302, which killed all 157 people on board, came less than five months after Lion Air Flight 610 went into the sea off the island of Java, killing all 189 passengers and crew members.
Both 737 Max 8 jets crashed at high speed minutes after takeoff in clear weather, following roller-coaster trajectories that hinted at desperate struggles by pilots to control planes seemingly immune to their interventions.
“To ensure unintended MCAS activation will not occur again, Boeing has developed and is planning to release a software update to MCAS and an associated comprehensive pilot training and supplementary education program for the 737 Max,” Boeing said in a statement after the report from Ethiopia was released.
Indonesian investigators have focused on whether the anti-stall system was activated by incorrect data on the plane’s angle of attack, essentially a measure of an aircraft’s likelihood of stalling.
MCAS, which was introduced in all Boeing 737 Max jets, pushes a plane’s nose downward if data indicates that the aircraft could stall because it is angled upward too steeply.
After the Lion Air crash last October, pilots and airlines complained that they had not been adequately briefed on MCAS by Boeing. The Max manual had no specific mention of how to correct a malfunctioning MCAS. Some pilots reported that they had not even known of the software’s existence.
In creating the Max jet, Boeing added bigger engines to the 737, which gave the airplane the fuel efficiency it needed to compete its rival, Airbus. But the change also altered the jet’s aerodynamics, and the larger engines had a tendency to push the airplane’s nose up.
To compensate, Boeing engineers created MCAS, which was meant to make the Max behave more like older versions of the 737. To become certified to fly the Max, pilots with prior 737 experience had to do only a couple of hours of online training.
Boeing has said that existing procedures were sufficient to address a MCAS malfunction, but early data suggests that pilots may not have known how to disengage the system, or may have done so too late to save their flights.