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What we learned from Ethiopian airline officials about Flight 302

This is the conclusion of the Ethiopian aviation authorities on Thursday, when they discussed a much anticipated preliminary report on the investigation of the accident investigation, which has not yet been published.

Last month's catastrophe – along with another crash of the same type of jet in October killed 189 – was enough to ground the entire service fleet of the world out of 737 Maxes and question the safety of the aircraft.

The automated anti-stall software called Maneuver Characteristic Expansion System (MCAS) is under suspicion.

Its function is to prevent the 737 Max nose from pointing upwards at a high angle – the so-called "angle of attack" referred to in the aviation industry. A dangerously high angle of attack (AOA) would bring a plane to a halt and possibly crash.

The Max models are the only 737-series aircraft using MCAS, and the system is suspected of contributing to the crash of the Lion Air Flight 61

0 in Indonesia.

On Thursday, Ethiopian Transport Minister Dagmawit Moge Flight 302 experienced "repeated, unannounced flight conditions" before its crash.

The description is similar to the Lion Air crash, though the minister did not specifically refer to this disaster. She also did not specify what the plane turned down.

  Ethiopian Airlines 737 Max pilots followed the expected procedures before the crash, say aircrew.

Without mentioning the word "MCAS", investigators recommend that Boeing review the "Flight Control System for Aircraft-Controlled Aircraft" and ensure that regulators are "adequately addressed" before the 737 Max fleet returns to service is provided.

According to Boeing, a new version of MCAS is currently being developed. It is expected that it will take weeks for the US aviation authorities to get approval.

Was there a problem with the sensor?

Regarding the possibility of a faulty MCAS sensor providing poor data, an Ethiopian accident investigator said Thursday that there was no damage to the aircraft sensors that could have contributed to the crash.

"We can confirm that we have not found foreign body damage," said Amdeye Ayalew, investigator of the Ethiopian Accident Information Bureau, to reporters through a translator. The AOA sensor at startup works normally. But after the start there was wrong data.

Already in October, the day before the crash of the Lion Air, a defective AOA sensor was replaced in the same aircraft, which had failed according to the Indonesian authorities. The plane then flew to Jakarta the same day, and the pilots reported further problems.

The improved MCAS system is powered by data from two AOA sensors on the outside of the jet – instead of one, says Boeing. The MCAS systems aboard the two crashed Max 8 were powered only by an AOA sensor. The idea is to provide an additional redundancy layer. MCAS enhancements also include a cockpit display to warn pilots when something is wrong with the sensors.

MCAS training did not seem to help prevent the crash

Ethiopian Airlines said in a statement Thursday that the pilots "followed the Boeing recommended and FAA-approved emergency procedures coping with the toughest emergency situation created on the plane … it was very unfortunate that they could not recover the airplane from the persistence of nasal diving. "In the statement of the airline MCAS was also not mentioned by name.

This concerns questions about training needs to fly the jet safely.

The airline's chief executive officer told CNN's Richard Quest last month that Flight 302 pilots used a flight simulator to learn how to fly the Boeing 737 Max. However, this simulator did not replicate MCAS.

CEO Tewolde GebreMariam said pilots switching from older 737 models to the Boeing 737 Max 8 would only need to complete a short Boeing-prescribed computer-based training program approved by the FAA.

Max 8 pilots for Southwest Airlines and American Airlines participated in courses that lasted between 56 minutes and three hours.

Following the crash of Lion Air, the FAA issued an emergency order with instructions on how pilots should unlock autopilot systems when the aircraft "has an unmatched hardware to stabilize the nostrils".

Overall, the Ethiopian aviation authorities make it clear that the pilot's mistake does not seem to be a problem in the crash and Boeing is now pressured to ensure the 737 Max is safe.

Richard Quest and Helen Regan of CNN contributed to this report.

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