Although the AoA disagree alert was supposed to display whether or not you had ordered the optional AoA continuous display, apparently there was a bug that meant that the alter was dependent on the optional display in practice:
(source)
>>After deliveries of the 737 Max commenced in 2017, Boeing discovered a software issue prevented the angle-of-attack (AOA) Disagree alert from working if customers had not chosen the optional AOA indicator.
>>“The Boeing design requirements for the 737 Max included the AOA Disagree alert as a standard, standalone feature, in keeping with Boeing’s fundamental design philosophy of retaining commonality with the 737NG,” says the company in a statement issued on 5 May.
>>“Several months” after 737 Max deliveries started in 2017, Boeing engineers discovered that “the 737 Max display system software did not correctly meet the AOA Disagree alert requirements.”
>>“The software delivered to Boeing linked the AOA Disagree alert to the AOA indicator, which is an optional feature on the Max and the NG. Accordingly, the software activated the AOA Disagree alert only if an airline opted for the AOA indicator.”
Biting the hand that feeds IT
