Semantron 23 Summer 2023

The Boeing 737 Max crisis

During the interview with Captain Davydov, regarding JT610, despite the fact that MCAS wasn’t fully described in the FCOM, it is still a memory item for pilots in case of RUNAWAY STABILIZER (QRH ref 9.1), STABILIZER OUT OF TRIM (QRH ref 9.14) or STABILIZER TRIM INOPERATIVE (QRH ref 9.15). He also mentioned that the pilots were facing 2 significant issues simultaneously, i.e. Airspeed Unreliable and Stabilizer Runaway. ‘ Both require memory items . . . We are not trained to deal with that (two memory items simultaneously ).’ Regarding the second crash, Captain Davydov expressed his shock, as Boeing had already issued a special bulletin on how to deal with MCAS. ‘ Pilots I would say tried the part of the memory items. They selected the stab trim switches to cut out but because of the high aerodynamic loads. ’ However, he added that all of those wouldn’t have happened if it wasn’t because of the poor design of MCAS. 104

Figure 17: A screenshot of part of the QRH, on Runaway Stabilizer (ref 9.1)


It is also important to note that during the development of MCAS, one of the coordination sheets (dated June 11, 2018) which records the history of developing MCAS, showed that ‘ a slow reaction time scenario (>10 seconds) found the failure to be catastrophic due to the inability to arrest the airplane overspeed ’. 105 This essentially means, if the pilots cannot disable MCAS from erroneously interfering with the control of the aircraft within 10 seconds, there will be no point of return, causing ‘catastrophic failure’. And of course, Boeing knew this.

Figure 18: Service Bulletin issued by the Boeing Company after the crash of flight JT610


In short, pilots from the first crash faced extreme pressure, and without really knowing or acknowledging MCAS and its counteractions, they failed to perfo rm the ‘memory items’. While in the second crash, despite knowing more than the pilots from the first crash did, and tried performing the right measures,

Figure 19: Coordination Sheet of MCAS, June 11, 2018

104 Davydov 2022, Email Questionnaire with Captain Denys Davydov by Matthew Wu . 105 The Committee on Transportation and Infrastructure 2022, Hearing Before the Committee on Transportation and Infrastructure, House of Representatives, One Hundred Sixteenth Congress, First Session : 22.


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