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