On Wed, 12 Dec 2018 17:56:17 +0000, Jan Panteltje wrote:

> It is a programming fault,
> the program SHOULD check for altitude, and it did not.
>
Read the linked stuff a bit closer: the LionAir plane was quite high and
fast - certainly at climbout speed - when the autotrim jumped in. In any
case it wasn't and should not be interested in altitude because the
condition it was supposed to prevent is more likely to occur both lower
and slower than typical high altitude cruise.

This is more likely to be a design error rather than a programming fault,
because it couldn't handle a single AOA sensor failure despite having a
pair of AOA sensors fitted. I say design, because the system test regime
will (and should) be created from the system specification rather than
the code - and clearly there was no acceptance test for operation with a
failed sensor or, as seems likely, nor for automatic disengagement if
both sensors fail.

> Also as to airspeed it should use at least 2 sensors and do arbitration
> and disable itself and give a clear warning to the pilots if an abnormal
> condition occurred.
>
Nope - by design this time. The autotrim was *designed* to correct an AOA
excursion without telling the pilots. Remember that the pilots were
intentionally not informed that it was installed, hence no training about
its effect or how to disable it.

> It is a design error, and I would sue the sh*t out of Boeing if it
> concerned me.
>
That will certainly happen: just give it time: the US justice system is
often very slow and Boeing will be fighting it all the way to the
courtroom door. Its just lucky for Boeing and their passengers that this
happened with fewer than ten 737-MAX in service.


--
Martin    | martin at
Gregorie  | gregorie dot org

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