The Ethiopian Accident Investigation Board recently released the final report on the crash of an Ethiopian Airlines Boeing 737 Max.

Released on Friday (December 23), the state investigators in their final report on ET302 confirm that a software bug is the main cause of the 2019 Boeing 737 Max crash.

The Ethiopian Airlines flight bound for Nairobi crashed six minutes after takeoff from Addis Ababa, southeast of the Ethiopian capital, killing all 157 passengers and crew.

Consistent with the preliminary report, the final report confirmed that the angle-of-attack sensor on the left side of the aircraft “failed immediately after takeoff, sending erroneous data to the flight control system,” said Dagmawit Moges, Ethiopia’s minister of transport.

The erroneous data triggered the MCAS flight control system, which repeatedly pointed the plane’s nose down until the pilots lost control of the plane, she said. The report should be public in the coming days.

In the aftermath of the crash of Ethiopian Airlines flight ET302, there is discord between investigative authorities in Ethiopia and the United States.

The NTSB wrote in a statement that it took the unusual route of publishing the comments on Ethiopia’s report on its own website because the Ethiopian authorities did not include them in its report.

The NTSB also noted with concern that the EAIB final report included significant changes from the last draft the EAIB provided the NTSB.

Bird Strike As a Possible Factor

While the investigators in Ethiopia identified the malfunction of the Maneuvering Characteristics Augmentation System MCAS as the cause of the accident, the NTSB agrees that in the United States, too, the faulty system inputs that led to the nosedive are believed to be the primary cause.

However, the authority’s statement states that the Ethiopian colleagues fail to mention other relevant factors.

The NTSB points out that bird strikes could also have played a role. Incidents involving birds damaging planes at Addis Ababa airport are frequent.

Apparently, the collision with a bird could have damaged the sensor that fed the MCAS erroneous input.

For example, Collins Aerospace, the manufacturer of the plane’s sensor, has said the flight data recorder readings are similar to previous cases of damage from a bird strike.

Crew Performace Not Discussed

In addition, the Ethiopian Aircraft Accident Investigation Bureau did not take into account that the aircraft would have remained controllable despite the MCAS malfunction if the crew had reduced the thrust manually and used the manual electrical trim appropriately.

Ethiopian Airlines received corresponding instructions from the USA months before the accident.

“The lack of information about flight crew performance limits the ability to address broader and equally important safety issues,” the NTSB release said.

However, data to analyze the pilots’ performance throughout the flight was actually readily available.

No Complete Transcript of the Voice Recorder

The US agency also criticizes the fact that the report does not contain a complete transcript of the data from the cockpit voice recorder.

“The current presentation of the transcript prevents one from obtaining a full and objective understanding of the event,” the NTSB concluded. It also accuses the Ethiopian counterpart of making false statements.

The adjustments that Boeing implemented on the 737 Max 8 have not received final approval, NTSB said.

Misleading Statements

Boeing’s failure to properly respond to Ethiopian Airlines’ request for more information about the MCAS following the October 2018 Lion Air 737 Max crash is also not factual.

According to the NTSB, on December 3, 2018, Boeing provided specific guidance on how to deal with uncontrolled stabilizer trim movements for all operators of the model to supplement the previously released operations manual.

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Victor Shalton

Victor Shalton's love for aviation can be traced to when he was 11-years-old. As a seasoned aviation writer, he takes pride in providing the best aviation coverage around the globe and is passionate about advancing his skills in the aviation space. In addition, he loves travelling, writing, arts and while his speaking engagements have taken him around the world, he is proud to call Nairobi home.

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