Investigative Agencies Dispute March 2019 737 MAX-8 Accident

Upon its 27 December receipt of the Ethiopian Aircraft Investigation Bureau’s (EAIB) final report on the 10 March 2019 loss of Ethiopian Airlines Flight 302—the National Transportation Safety Board (NTSB) took the unusual step of publishing comments it had previously provided to the EAIB regarding the infamous 737 MAX-8 accident.

The board asserted the EAIB “failed to include the NTSB’s comments in its final report on its investigation.”

In accordance with the provisions of the International Civil Aviation Organization (ICAO) Annex 13, countries participating in the investigation of a given accident or incident are afforded opportunity to review draft reports and provide comments pertaining to such to the investigative authority.

If the investigating authority disagrees with the comments or declines to integrate them into the accident report, participating countries are entitled to request that their comments be appended to the final report.

According to the NTSB, the EAIB’s draft report failed to include salient input from the NTSB, including the following assessment of probable cause in the accident:

“We agree that the uncommanded nose-down inputs from the airplane’s MCAS system should be part of the probable cause for this accident. However, the [EAIB’s] draft probable cause indicates that the MCAS alone caused the airplane to be ‘unrecoverable,’ and we believe that the probable cause also needs to acknowledge that appropriate crew management of the event, per the procedures that existed at the time, would have allowed the crew to recover the airplane even when faced with the uncommanded nose-down inputs. We propose that the probable cause in the final report present the following causal factors to fully reflect the circumstances of this accident: 

• uncommanded airplane-nose-down inputs from the MCAS due to erroneous AOA values and
• the flight crew’s inadequate use of manual electric trim and management of thrust to maintain airplane control. In addition, we propose that the following contributing factors be included:
• the operator’s failure to ensure that its flight crews were prepared to properly respond to uncommanded stabilizer trim movement in the manner outlined in Boeing’s flight crew operating manual (FCOM) bulletin and the FAA’s emergency airworthiness directive (AD) (both issued 4 months before the accident) and
• the airplane’s impact with a foreign object, which damaged the AOA sensor and caused the erroneous AOA values.”

In its statement, the NTSB further set forth: “The EAIB provided the NTSB with its first draft of the report last year. The NTSB reviewed the report and provided comments on several aspects of the accident the NTSB believed were insufficiently addressed in the draft report. The comments primarily were focused on areas related to human factors.”

The board added: “The NTSB also noted that the final report included significant changes from the last draft the EAIB provided the NTSB. As a result, the NTSB is in the process of carefully reviewing the EAIB final report to determine if there are any other comments that may be necessary.”

FMI: www.ntsb.gov