The National Transportation Safety Board (NTSB), the investigative agency responsible for civil transportation accident investigation, criticized the certification of the 737 MAX by Boeing and the Federal Aviation Administration (FAA) for misjudging the reaction of pilots in case of malfunction of the MCAS system that caused the crashes of Lion Air and Ethiopian Airlines. This misinterpretation could have consequences for other aircraft certified in the United States.

In a non-final 13-page report published on September 26, 2019, the NTSB gives seven recommendations that target not only the Boeing 737 MAX but also the way other aircraft were certified by the FAA. These observations are based on the ongoing investigations into the two crashes, in both of which the NTSB is participating.

“We saw in these two accidents that the crews did not react in the ways Boeing and the FAA assumed they would,” said NTSB Chairman Robert Sumwalt. The NTSB says it does not judge the behavior of pilots in both accidents, but the assumptions made during the 737 MAX certification process in the United States. “It is important to note that our safety recommendation report addresses that issue and does not analyze the actions of the pilots involved in the Lion Air and Ethiopian Airlines accidents,” comments Sumwalt.

In the original design of the flight system of the aircraft, Boeing believed the pilots could disable the MCAS immediately if this one was to malfunction. The Ethiopian Airlines and Lion Air crashes that killed 346 people proved otherwise. “Those assumptions were used in the design of the airplane and we have found a gap between the assumptions used to certify the MAX and the real-world experiences of these crews, where pilots were faced with multiple alarms and alerts at the same time,” Sumwalt explains. The report states that current FAA guidance does not take into account the event of multiple flight-deck alerts and indications when evaluating pilot recognition and response.

In this regard, the board relates the two crashes to the Air France flight 447. In its final report published in July 2012, the French Bureau of Enquiry and Analysis for Civil Aviation Safety (BEA) concluded that the Airbus A330 pilots failed to respond correctly to the icing of the pitot tubes partly because “they were never in a position to make the connection between the messages that appeared and the procedure to apply, although reading the ECAM and messages should facilitate the analysis of the situation and allow failures to be handled”. Back then, the BEA recommended that the EASA “study the relevance of having a dedicated warning provided to the crew when specific monitoring is triggered, in order to facilitate comprehension of the situation”.

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Thus the NTSB recommends that the FAA require that Boeing “consider the effect of alerts and indications on pilot response and address any gaps in design, procedures, and/or training“ in already existing “uncommanded flight control inputs“ of the 737 MAX system and other already certified aircraft. The FAA also has the responsibility to inform other regulators such as the EASA of said recommendations so they can conduct the same reevaluation. It also calls for the development of new tools and methods of certification to better assess pilot response to failures, and of system diagnostic tools that better report and prioritize failure indications to the flight crew.

NTSB says it continues assisting Indonesian and Ethiopian investigators. The KNKT (the Indonesian investigation office) accident report is expected to be released in the coming months, and its analysis of the Lion Air accident could generate further conclusions and recommendations, according to the Board.