737MAX Stab Trim architecture

[gums]

Salute Wolf!

Here's my rationale for my opinion/theory/whatever regarding the AoA sensor and its influence on various aircraft systems.

The cascading failures or unexpected operations of several systems seems evident once you start with the AoA that appears up to 20 degrees different than the other AoA sensor. So let us see the flow chart/system diagram.[AoA data to the air data black boxes and the crew sees unreliable airspeed. Bad AoA flag might not help here if crew does not understand the MCAS, but relation with stick shaker would prolly be recognized by 99% of the crews ]

- At start of the data, one AoA shows about 10 - 12 degrees higher than the other. After liftoff the delta increases to maybe 20 degrees and tracks the other AoA sensor perfectly.
- the overall system fault monitoring system does not flag the AoA disagreement as such [after takeoff. It shows the crew unreliable airspeed once pitot speed is above "x" and AoA data is bad, like 20 degrees delta. ]
- At liftoff we see several trim inputs from the "system", which seems from STS, and they look like STS is doing its job. i.e. trim up to maintain the trimmed speed. But stick shaker is now active.
- flaps are now fully retracted, stick shaker continues because AoA from one vane is very high and the circus starts.
- Hal trims down, gums trims up a bit because we are climbing like normal, increasing speed and that crazy STS is wired backwards.
- Nose down trim geting really strong, but trim switch on yoke seems to be working, But after I let off for 5 seconds I see nose down trim again. This ain't STS, I think.

Somewhere in the scenario the "feel" system is acting on the control yoke, and I do not have the personal flight experience to comment on how it feels and not sure about how it is supposed to work in concert with the other sub-systems and their logic/specs when they go south.

Meanwhile, pilot and MCAS are commanding up trim and down trim for 5 or 10 second intervals until something big happens and we see lotta power commanded and a divergent control pressure for each yoke.

Gums...