Ethiopian Airlines Tragedy Revisited: NTSB Disputes Final Report Findings on 2019 ET 737-Max Crash

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Note: this article was originally published in December, 2022

Over 3 years after the dreadful Ethiopian Airlines Flight 302 plane crash which claimed all of the 157 lives aboard, a final report on the accident investigation has been released to the public by Ethiopia’s Aircraft Accident Investigation Bureau (EAIB).

However, what was supposed to provide a sense of closure to the tragedy seems to be inadequate as US agency National Transportation Safety Board (NTSB) has posted public comments on its website in disagreement with EAIB’s final report.

The US safety agency claims that EAIB left out NTSB’s comments on the accident findings from its final report which was published on its website on December 27. NTSB also claims that the final report published by EAIB was very different from the draft version the latter provided earlier.

The Accident and Initial Investigations

On the morning of March 10, 2019, Ethiopian Airlines Flight 302 departed from its hub Addis Ababa International Bole Airport en route Jomo Kenyatta International Airport in Nairobi, Kenya.

The months-old  Boeing 737-Max had 8 crew members and 149 passengers on board, including 32 Kenyans, 18 Canadians, 8 Americans, 7 Britons and a myriad of other foreign nationals. Just 6 minutes after it took off, the 737-Max crashed, killing all on board and marking the airline’s (ET’s) deadliest accident to date.

The accident was the second 737-MAX crash, less than 5 months after Indonesia’s Lion Air Flight 610 crash which claimed all 189 lives on board. After the ET crash, the 737-MAX which was relatively new to service at the time was forced into a worldwide grounding for what would be a long time.

An eyewitness at the scene of the accident told the BBC that there was a huge fire as the aircraft crashed to the ground that made it hard for anyone to get near it and try to rescue those aboard.

Following the crash, US representatives travelled down to Ethiopia to assist with the EAIB investigation – the aircraft original equipment manufacturer (OEM) Boeing is American. The US team included NTSB, Federal Aviation Administration (FAA), Boeing and General Electric, the engine manufacturer.

The investigative team were able to recover the Black Box and flight data recorder at the site of the crash, which provided the necessary data for the incident report.

The findings on preliminary investigations attributed the crash to a design flaw in the Manoeuvring Characteristics Augmentation System (MCAS) which then repeatedly forced the aircraft into a nose-down attitude that the pilots were unable to recover from. The Angle of Attack (AOA) sensor gave false readings which triggered the MCAS automatic trimming of the aircraft 4 times within the 6 minutes the aircraft was airborne.

However, further investigations were carried out to find out the nature and extent of the design flaw and if there were any other complications that compounded the failure.

Further investigations by NTSB, FAA as well as the US’s House Committee and Senate Committee revealed that Boeing had initially tried to conceal the existence of the MCAS to prevent the 737-MAX from having to be certified as a new aircraft design. Thus, the FAA had certified the aircraft model, allowing it to enter into service with its flawed systems.

The aircraft was only allowed to re-enter into service after significant design modifications as well as extensive pilot training were undertaken in late 2020. Still, Boeing is yet to fully regain the aviation sector’s trust concerning the 737-MAX.

NTSB’s Additional Conclusions

EAIB provided NTSB with its draft accident report a year after the crash. After review, the latter included comments on factors they believed the Ethiopian Authorities did not adequately address.

NTSB agreed with the MCAS’s part in the accident, however it stated that EAIB failed to mention other relevant factors such as the crew’s inadequate use of manual electric trim and thrust to regain control of the aircraft, as well as the possible bird strike damage sustained to the aircraft AOA sensor.

·         Flight Crew Performance:

NTSB asserts that even with the MCAS’s faults, the flight crew could have salvaged the situation by manually reducing the thrust and trimming the aircraft to maintain control. The agency also opined that the airline had failed to ensure its flight crew was prepared to respond appropriately to the uncommanded movement of the stabiliser trim. The appropriate procedures for such events were stated in the OEM’s flight crew operating manual and the FAA’s emergency airworthiness directive, which were issued four months prior. However, EAIB’s report stated that there was no information pertaining to the MCAS in the operating and flight manuals provided by Boeing.

·         Bird Strike:

The bird strike suggestion was made after Collins Aerospace, the AOA sensor’s manufacturer showed that the recorded data did not point to an internal failure of the sensor, but rather a partial separation of the AOA vane due to a bird strike. NTSB suggested that EAIB’s runway search was inadequate as it did not cover the area surrounding taxiway D, even though the plane would have been positioned around there when the left sensor data became inaccurate. Moreso, bird strikes are not uncommon at the Addis Ababa Bole International Airport. A 2018 EAIB report shared that eagles were usually present around the airport.

The NTSB’s hopes with releasing the additional comments to the public is that significant consideration will also be given to these human factors which pose a threat to flight safety. In aviation, when one party fails to do what is right, the other parties must do all that they can to dampen the effects of the error.

Sources: Simple Flying, BBC, Air Insight Group

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