quote:
Most modern, computerized aircraft -- such as more recent Boeing models and Airbus SE’s jets -- use three computer systems to monitor each other, Hansman and Lemme said.

By contrast, the 737 Max had two separate computers. One operated the flight systems and another was available if the first one failed, with the roles switching on each flight. But they interacted only minimally.

Boeing decided to make the two systems monitor each other so that each computer can halt an erroneous action by the other. This change is an important modernization that brings the plane more in line with the latest safety technology but raised highly complex software and hardware issues.

Wasnt 1 of the AOA sensors connected to one flight computer and the 2nd connected to the second flight computer?

Once they expanded MCAS beyond the high speed windup turn case to include use at slower speeds and more powerful & larger trim movements they also dropped sensors related to sensing higher speed or Gs to rely only on one AOA. Besides not keeping these sensors included for the high spend maneuver to only allow smaller trim movements at high speeds which may have helped Ethiopian flight would the original design of flight computers not communicating with each other be real reason they didn’t include using and comparing both AOA sensors. Change wasn’t even reported to FAA and just wondering if someone did a cost analysis of time and money involved or lost to include 2nd sensor and potential risk involved to not delay rollout to get this done and just wait until regular maintenance type software updates.

The excuse they used about failure rate of MCAS deeming need of only one sensor never made much sense when they had a second AOA sensor sitting there each flight unused (can’t remember exact terminology used about failure and number of sensors). It really was failure rate of sensor more than main MCAS and having only 1 in play that with a failure would also cause other warnings & stick shaker on top on and even before MCAS kicked in distracting pilots seemed kind of dumb. I remember reading one AOA connected to one computer and the other to 2nd computer and how they along with respective computers switched each flight, but I didn’t realize they were walled off from each other like this. I also don’t know if this wall effected how quickly or easily they could have updated software to include using both AOAs and still launched product at same time.

This post was edited on 11/8/19 at 5:11 pm