Originally Posted by
FCeng84
MCAS activation requires AOA above an activation level that is a function of Mach number. The dependence on Mach is not particularly significant (i.e., errant Mach would not significantly impact the MCAS activation point). The amount of stabilizer motion that MCAS will command is also a function of Mach number. With Mach less than 0.4 MCAS will move the stabilizer as much as 2.5 degrees if AOA exceeds the activation threshold by many degrees. At cruise Mach number the size of the MCAS stabilizer motion increment is less than 1/3rd that at low Mach numbers. The bottom line with regard to the question posed here is that a blocked pitot coupled with healthy AOA data would not cause MCAS to activate unless actual (and thus properly sensed) AOA increased to a level significantly above that for normal operation. If you follow pitch/power guidelines after pitot blockage and detection of unreliable airspeed you will not get MCAS. If you get slow and get to elevated AOA following pitot blockage you are likely to encounter MCAS provide flaps are up and autopilot is not engaged.
Thanks for the clarification!
So it’s possible we’ve had hardware failure in two separate components? Pitot and alpha vane?