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Old 29th Mar 2019, 06:50
  #174 (permalink)  
GordonR_Cape
 
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Originally Posted by IFixPlanes
Engaged MCAS overrides the column cutout switches.
I think it is clearer to say that the MCAS control signals run from the flight control computers to the stabiliser trim through a different circuit. This follows so that MCAS trim is not overridden, unlike speed trim which is inhibited by the column cutout switches.

We know that the wiring and labels of the pedestal cutout switches have been modified in the MAX, so it makes sense that the changes for MCAS were done as part of that process. This was discussed earlier (can't find the reference).

It would not make sense to have wiring going from any of the switches to the FCC, which is my interpretation of your statement. AFAIK the B737 MAX is still fundamentally a manual aircraft, and all software functions are implemented upstream of those downstream cutoff switches.

These wiring differences have profound implications for pilots trained on NG, when trying to diagnose an MCAS fault on the MAX. They probably explain most of the Lion Air pilots actions and confusion.

Last edited by GordonR_Cape; 29th Mar 2019 at 11:58. Reason: Factual inaccuracy.
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