Originally Posted by
mosquito88
Could someone familiar with the AoA vane and MCAS tell me what would happen if a bird strike jammed the vane in either an up or down condition?
Can the system detect a damaged sensor and if not, what would happen?
In its certified form or yet to be released updated version? No one really knows, but I believe the PPRuNE brains trust would say something along the lines "it depends".
There would be many different failure scenario's, the AoA reported value could be frozen at its last known good position, it could detect the failure and report no value, and many other possibilities in between (erratic oscillations etc). The next question is the software side, and how much error checking and validation it does and how gracefully it handles anticipated failure modes.
Generally, the opinion (and Boeings own failure analysis) of the MCAS software is assumes the pilot will handle any system input error and disable the system via the stab trim via the cutout switches. This turned out to be a heroic assumption...
Seattle Times:
Flawed analysis, failed oversight: How Boeing, FAA certified the suspect 737 MAX flight control system
System failed on a single sensor
The bottom line of Boeing’s System Safety Analysis with regard to MCAS was that, in normal flight, an activation of MCAS to the maximum assumed authority of 0.6 degrees
was classified as only a “major failure,” meaning that it could cause physical distress to people on the plane, but not death.
In the case of an extreme maneuver, specifically when the plane is in a banked descending spiral, an activation of MCAS was classified as a “hazardous failure,
” meaning that it could cause serious or fatal injuries to a small number of passengers. That’s still one level below a “catastrophic failure,” which represents the loss of the plane with multiple fatalities.