Originally Posted by
Luc Lion
CORRECTION: Do you mean that what Boeing calls a "
Elevator Feel Computer" is actually a mechanical computer ???
This is correct for the Elevator Feel Shift (EFS) module which simply increase by a factor 4 the system A pressure fed into the Elevator Feel & Centering Unit.
It is also true for the Elevator Feel & Centering Unit which transforms differential pressure into feel forces.
But the pressure normally fed into the Elevator Feel & Centering Unit is controlled by a computer unit, the Elevator Feel Computer, which uses airspeed and stab position inputs for computing how much hydraulic pressure it should transfer downstream.
I reckon that the AoA is NOT documented as an input data received by the Elevator Feel Computer ; AoA is only available to the EFS (in this area).
But an upgrade of the Elevator Feel Computer by adding AoA input and modifying its algorithms should not be more considerable than fixing the MCAS logic with dual AoA input.
The advantage of acting through the Elevator Feel System is obvious : no effect on the pilot pitch authority if the AoA probe goes mad in normal flight.
I cant answer for the specifics of the EFS computer other than that I am of the understanding that it is purely mechanical.
For sure there exists pure mechanical computers. Early fire control computers on various military ships during and after the WWII was purely mechanical. I have seen ducumentary about them and those computers was marvels of accurate mechanical engineering.