[External] Re: What do you think about this airline vs 5G brouhaha?

Mark Tinka mark at tinka.africa
Fri Jan 21 09:10:06 UTC 2022

On 1/20/22 20:45, Keenan Tims wrote:

> The AOA DISAGREE alert was never intended as an optional feature. 
> However either due to a software bug or miscommunication between 
> Boeing and their contractor for the avionics package (Collins?), it 
> got tied to the optional AoA (value) indicator. This was caught *by 
> Boeing* and reported to the contractor, but Boeing instructed them not 
> to fix the problem and defer it to a later software update 3 years 
> later, and never bothered to notify operators or the FAA about the 
> problem.

In my mind, that is still rather negligent and irresponsible, especially 
because in the -MAX, this was more critical considering the level of 
input from the computer to activate MCAS outside of the pilot's control, 
or even knowledge.

Unlikely to be such a big deal in earlier B737 models, where MCAS is not 

> Somehow it's even worse this way. I don't think a working DISAGREE 
> alarm would have saved the flights, though.

There has been AoA sensor failure in non-MAX B737 aircraft. The 
difference is you don't have MCAS there trying to do its own things.

Of course, had an AoA sensor failure and/or "AoA Disagree" scenario been 
tested and trained for, particularly on the -MAX, it would have been 
fairly obvious to both the Lion Air and Ethiopia crew that 
troubleshooting for a "Runaway Stabilizer Trim" would likely have saved 
their lives. Of course, troubleshooting for a runaway stabilizer with 
MCAS involved also has its nuances, depending on air speed, aircraft 
configuration, e.t.c.


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