Either way, it's apparent that Boeing broke a cardinal rule in engineering: if you create a product (eg MCAS) to solve a safety issue (stick lightening), the failure of that product cannot cause a more severe issue (uncontrolled nose dive into terrain). Which is why I and many in aerospace engineering are convinced it was an intentional gaff with the one sensor design, to get the plane to market and save market share that was threatened by the Airbus Neo.
This is really what it all comes down to, just sit and think about the entire thing for a second. They supposedly needed the slightest amount of stick force added in some rare circumstance so the solution they thought up was move the one of the main control surfaces of the plane (a device whose entire point is to leave the ground and then avoid it for as long as needed) so that it tends toward the ground. Then they increased the authority so that it aggressively shifts the nose downwards for some reason, and also remove a redundancy that would allow the pilots to shut off automatic trim controls while still allowing the pilots to manually give electric trim commands. It's just such an obviously dangerous idea for resolution of what is a small technical certification requirement.
Either Boeing is hiding something else about the MAX's flight characteristics or they are simply incompetent, and in either case it doesn't say good things about the rest of the MAX as a whole or any other product they've worked on since then.
It's even worse than that. Boeing didn't only increase the authority (as in speed of control surface travel and max travel per activation cycle) of an automatic control for no properly documented reason (that we know of, at least), they also
- increased dramatically the activation envelope of the automatic control by removing G-load from the control logic
- by the same stroke, they removed an input channel making MCAS a single input channel architecture without adding the required input sanitation logic
- made the controller's authority effectively unlimited by allowing multiple activation cycles.
As if this wasn't already enough, they also modified the stab trim cut out switches logic - mind you - not by "removing a redundancy", but by removing the one manual control, already present in the ancestor design, that would have effectively disabled the controller without disabling the electric stab trim motor. The reason for this change was not only not properly documented, but actively camouflaged as a mere "labeling change".
Even worse than that: the new cut out switch labeling (PRImary + Back/Up) is indicative of the intention to add
redundancy to the electric stab trim motor cut off switch. C'mon, really? You've got a single active FCC, driven by a single active air data sensor suite, and you worry about adding redundancy to a mechanical switch
? And you do this by removing
switch that would have disabled a runaway controller?
Many posters here claim they believe this incredible design was the result of a series of good-faith mistakes, driven by a mix of incompetence, schedule pressure and budget constraints. But even if I would really like to subscribe to this opinion, I just cannot bring myself to imagine someone *that* incompetent (let alone an engineering team).
I'm eagerly awaiting the results of the testing with the bare airframe.
So it's confirmed that this test still has not been flown?