NTSB picks holes in EAAIB’s final report on Ethiopian Airlines B737-MAX crash
The United States National Transportation Safety Board (NTSB) has expressed its disapproval over a recently published final report on the crash of Ethiopian Airlines B737-MAX which did not capture its final comments.
According to the NTSB, the report, which was published by the Ethiopian Aircraft Accident Investigation Bureau (EAAIB) last Friday, was deliberately crafted to reflect an outdated version of its (NTSB) comments, prompting the agency to do the “unusual” by publishing its final and valid comments on its website publically.
Firstly, the NTSB said it received the EAAIB’s final report on December 27, 2022, four days after it was initially published by its Ethiopian counterpart, citing a violation of ICAO’s (International Civil Aviation Organisation) Annex 13, which states that “countries participating in the investigation are provided with the opportunity to review the draft report and provide comments to the investigative authority” before it goes public.
“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,” the NTSB added.
The NTSB noted that the report cited mechanical fault, particularly referring to the repeated nose-down movements made by the Maneuvering Characteristics Augmentation System (MCAS) in the aircraft as a probable cause of the crash, without paying attention to human errors in the management of emergency procedures.
While the agency (NTSB) agreed that the MCAS partly contributed to the crash, it still argues 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.”
It added that the probable cause of the crash could be a combination of MCAS failure and the flight crew’s “inadequate use of manual electric trim and management of thrust to maintain airplane control.”
The NTSB, also, accused Ethiopian Airlines of its failure to adhere to procedural information on how to respond to uncommanded nose-down movements, which were outlined by Boeing’s Flight Crew Operating Manual (FCOM) and the FAA’s Airworthiness Directive (AD), both of which were published four months prior to the crash.
Another contributing factor, according to the NTSB, could be that the ill-fated aircraft “impacted a foreign object that damaged the AoA sensor, resulting in several erroneous activations of MCAS.”
In its report, however, the EAAIB indicated that the aircraft manufacturer Boeing, along with the Federal Aviation Administration (FAA), and the NTSB failed to point out engineering errors related to the 737 MAX.
The Ethiopian investigators insisted that it was not informed about the aircraft’s “engineering design error in their initial AOA (Angle Of Attack – ed. Note) Sensor Hazard Analysis.”
The EAAIB, also, argued that the “new Airplane experienced unexplained electrical and electronic faults within weeks of entering service, and in the weeks and days prior to its crash,” suggesting that it did not receive or notice the inclusion of procedural information on how to manage uncommanded nose-down movements of the aircraft as claimed by the NTSB.
However, reports indicated that Boeing delivered the 737 MAX in November 2018, four months before the accident occurred in March 2019.
Other probable factors not captured in the report, according to the NTSB, are that the EAAIB did not discuss the flight crew’s performance, including Cockpit Resource Management (CRM) throughout the report, despite their input playing a key role in the crash.
“The absence of flight crew performance information limits the opportunity to address broader and equally important safety issues,” said the NTSB.
It added: “As we have reiterated throughout the investigation, design mitigation must adequately account for expected human behaviour to be successful, and a thorough understanding of the flight crew’s performance in this accident is required not only for robust design mitigations but also for operational and training safety improvements necessary to achieve multiple layers of safety barriers to trap human errors and prevent accidents.”
On the assumption that the MCAS made the aircraft uncontrollable, the NTSB argued that “if the crew had manually reduced thrust and appropriately used the manual electric trim, the airplane would have remained controllable despite uncommanded MCAS input”, adding that the crew did not perform the described non-normal procedures following the unreliable speed, stall warning, runaway stabilizer, and overspeed warning alerts.
The agency also observed that the EAAIB’s report touched on the CRM and its effect on the cockpit environment during the flight yet failed to “fully evaluate the CRM that occurred during the accident flight.”
Another inadequacy highlighted by the NTSB is that the report failed to provide the full transcript of the Cockpit Voice Recorder (CVR) data, adding that the transcript provided by the EAAIB had been altered with inappropriate commentary without the consent of other members of the investigation team.
“The current presentation of the CVR transcript prevents the reader from having a complete and objective understanding of the event,” NTSB said.
