Addis Ababa, Ethiopia • The pilots of Ethiopian Airlines Flight 302 performed all the procedures recommended by Boeing to save their doomed 737 Max 8 aircraft, but could not pull it out of a flight-system-induced dive, a preliminary report into the crash concluded Thursday.
In a brief summary of the much anticipated preliminary report on the March 10 crash, Ethiopian Transport Minister Dagmawit Moges told reporters that the “aircraft flight-control system” contributed to the plane’s difficulty in gaining altitude from Addis Ababa airport before crashing six minutes later and killing all 157 on board.
She said the crew "performed all the procedures, repeatedly, provided by the manufacturer but was not able to control the aircraft."
"Since repetitive uncommanded aircraft nosedown conditions were noticed in this preliminary investigation, it is recommended the aircraft flight-control system related to the flight controllability be reviewed by the manufacturer," she said.
As in the aftermath of a Boeing 737 Max 8 crash in Indonesia in October, attention in the Ethiopian Airlines crash has been zeroing in on a flight-control system known as the Maneuvering Characteristics Augmentation System, or MCAS, which pushes the nose of the aircraft down to avoid a midair stall.
While she never mentioned MCAS by name during a news conference despite repeated questions from journalists, Moges's comments suggested that the system was activated during the flight and that the pilots were not able to use Boeing's recommended methods to disable it.
The report, which stops short of determining the cause of the crash, chronicles the chaotic last moments aboard the flight before it crashed.
It details how a minute after takeoff from Bole International Airport, one of the angle of attack sensors sent bad information to the aircraft's system, activating the stick shaker on the pilot's column - a vibration that warns the pilot of an impending stall.
Reacting to the faulty data, the MCAS system kicked in to force the plane's nose down, according to the preliminary report. The MCAS activated four separate times, and each time the pilots fought unsuccessfully to regain control of the plane.
In a statement, Boeing acknowledged the report's finding that faulty data from an angle of attack sensor triggered the MCAS function during the flight, as it had during the flight that crashed in Indonesia. The company said proposed software updates and pilot training will ensure the "unintended MCAS activation will not occur again."
"The update adds additional layers of protection and will prevent erroneous data from causing MCAS activation," the statement said. "Flight crews will always have the ability to override MCAS and manually control the airplane. Understanding the circumstances that contributed to this accident is critical to ensuring safe flight. We will carefully review the AIB's preliminary report, and will take any and all additional steps necessary to enhance the safety of our aircraft," said Kevin McAllister, Boeing's president and chief executive for commercial airplanes.
Black-box data released by Ethiopian investigators showed that the crew tried to use a backup manual trim system to counter the MCAS, in an attempt to raise the plane's nose. The pilot called out "pull up" three times to tell the co-pilot to raise the nose, and in the last seconds of the flight both pilots tried together to pull the nose back up, but still could not regain control of the aircraft, according to the report. The trim system is also used to stabilize a plane.
Experts say the airplane was traveling too fast and the manual trim wheel would have been physically impossible to operate.
"At higher speed, manual trim may not be available due (to) airload on the stabilizer," said John Cox, a former pilot and an airline-safety consultant who has been privately briefed on the evidence by people familiar with the investigation. "Not enough force can be generated manually to move the trim."
According to data from Flightradar24, the pilots pushed the aircraft to a speed of 380 knots - roughly 437 mph - but the plane failed to climb more than 1,000 feet above ground in an area surrounded by high terrain.
Investigators believe MCAS also contributed to the Oct. 29 crash in Indonesia, where they say erroneous data from an outside sensor caused the system to force the nose of that plane down over and over again. Pilots were unable to regain control, and the Lion Air flight eventually plunged into the Java Sea, killing 189 people.
After the Indonesia crash, Boeing issued a bulletin outlining how to shut down MCAS in case of malfunction, and Thursday's preliminary report seemed to indicate that the pilots followed that procedure.
Previous evidence found at the Ethiopian crash site showed that equipment on the 737 Max's tail was positioned in a way that would push the plane's nose down. Satellite data also showed that the Ethiopian Airlines jetliner had ascended and descended multiple times after takeoff, mirroring the behavior of the plane in the Lion Air flight.
Both flights struggled to gain altitude, and both appeared to have erratic flight paths before crashing.
Amid reports that a foreign object might have damaged one of the Ethiopian plane's sensors on takeoff, Amdeye Ayalew, the head of the investigation, said information from the recovered data recorders gave no such indication.
"We did not find any information regarding the foreign object damage on the aircraft," he said. "Is there a structural design problem? No, we cannot verify that now."
Officials said a full report would be completed within a year of the crash.
Ethiopian Airlines said immediately after the news conference that the report absolves the pilots, who "followed the Boeing recommended and FAA-approved emergency procedures."
"Despite their hard work and full compliance with the emergency procedures, it was very unfortunate that they could not recover the airplane from the persistence of nose diving," the airline stated.
The similarities between the two crashes, five months apart, prompted aviation authorities to ground more than 370 of the jetliners worldwide.
Those familiar with the investigation also point to some differences between the two flights. For example, the Ethiopian aircraft had no mechanical problems before the crash.
"It had flown to Johannesburg and back without any maintenance issues," Cox said.
"The airplane was mechanically sound. It had no deferrals, no write-ups, and that makes a big difference," he said.
By comparison, the Lion Air plane had multiple issues starting Oct. 26, including on the four flights before the one that crashed into the Java Sea three days later, according to a preliminary report from Indonesian authorities. The plane's maintenance log showed that pilots reported defects with incorrect displays of speeds and altitude and that airline mechanics worked to resolve the problems.
The Max 8 single-aisle aircraft is the most recent iteration of the 737 line - the world's most popular commercial airliner that first flew in 1967. The Max is the fastest-selling plane in Boeing's history, with nearly 4,700 planes sold or on order.
The new revelations about the ill-fated jetliner come after Boeing, grappling with fallout from the two deadly crashes, outlined upgrades to the aircraft's software and increased training for 737 Max pilots.
Boeing has said it would take about an hour for technicians to load a software update for the planes. The company's software fixes will change the way the MCAS receives information, requiring feeds from both outside "angle of attack" sensors, rather than one, before it is triggered.
The system will also have more limits on how often it will engage, and Boeing will make changes that prevent the anti-stall feature from angling the plane's nose too far downward in its attempts to correct for a possible stall.
On Wednesday, Boeing announced that its chief executive, Dennis Muilenburg, Muilenburg had joined pilots aboard a flight to test the updated MCAS software as part of the certification requirements and that "it worked as designed."
A Federal Aviation Administration spokesman said Monday that the agency expects to receive the final package of software and training updates for review "over the coming weeks," reflecting a delay from its initial timeline. Boeing had initially planned to submit the fix for FAA review last week.
Questions surrounding the two crashes have turned a harsh spotlight on Boeing. In the wake of the disasters, U.S. lawmakers have raised doubts about FAA oversight. They have called for several hearings, including one last week in which Daniel K. Elwell, acting FAA administrator, said the certification process for the Max aircraft was "detailed and thorough."
Elwell painstakingly explained that Boeing's goal in the redesign of the 737 Max was to make it fly exactly as previous generations of the plane had, despite the fact that the engines were somewhat larger and repositioned farther forward on the wings.
To combat the additional lift provided by the new engines, Boeing introduced the MCAS, an unprecedented computerized device designed to push the plane's nose down to combat that added lift and to prevent a "stall" that could cause the plane to crash.
There have been 17 generations of the 737 since it began flying, and Boeing wanted the Max to perform exactly as its predecessor, the 737 NG, had.
The U.S. Justice Department's criminal division is looking into the Max jets, while the Transportation Department's inspector general is investigating the way they were certified. Transportation Secretary Elaine Chao has formed an "expert special committee" to review the procedures for the planes.
The FAA said late Wednesday it is creating a technical review team that will be headed by a former top U.S. transportation safety official and will include representatives from NASA and foreign civil aviation authorities.
According to the preliminary report, the aircraft's data recorder was recovered Mar. 11 and had data from 73 hours of operation, covering 16 flights, including the fatal flight. The voice recorder, which was recovered the same day had just over two hours of information, which included the previous flight in addition to Flight 302.
The plane crashed in a farm field and indicated evidence of a "high energy impact." There was no indication of fire. The impact of the crash created a crater roughly 33 feet deep, 92 feet wide and 131 feet long. Most of the plane's wreckage was buried in the ground, but small fragments were found scattered around an area roughly 656 feet wide and 984 feet long.
On March 25, Ethiopian Airlines chief executive Tewolde Gebremariam went out of his way to express his company's continued belief in Boeing, despite repeatedly expressing concern about the Max jets.
"Let me be clear: Ethiopian Airlines believes in Boeing. They have been a partner for many years," he said in a statement.
Boeing's Muilenburg returned the favor the next day and reiterated the company's strong ties with Ethiopian Airlines, praising the carrier as "a pioneer and a leader" in the industry with a "reputation for service and safety." He called the airline a symbol of the progress "of a great people."
Ethiopian Airlines, one of the country's flagship companies, has been engaged in a massive expansion, tripling the size of its fleet in less than 10 years to 113 aircraft. The airline now flies to 120 destinations on five continents and carries more than 11 million passengers a year.
Lazo reported from Washington. Ashley Halsey III and Lori Aratani in Washington contributed to this report.