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There are several inexcusably egregious errors in the design of the MCAS system, and this "solution" addresses none of them. - Single point of failure: The sys
by tbabb 8y ago
There are several inexcusably egregious errors in the design of the MCAS system, and this "solution" addresses none of them.
- Single point of failure: The system makes command decisions based on the readings from a single sensor. The fact that nobody asked (or was bothered by the answer to) the question "what happens when that sensor fails?" is negligence.
- No re-training of pilots: Pilots were not aware of new ways in which the plane might take command away from them, and were left in the dark with only seconds to react to a deadly situation. The decision not to train was a cost and marketing motivated decision that sacrificed safety, to the tune of hundreds of lives lost.
Slapping on heuristics to condition unreliable data is not a good solution for life-critical systems. As another commentor pointed out, this is armchair quarterbacking, and it is not good armchair quarterbacking. This article should not be here.
- kgilpin 8y agoAmong all the MCAS noise, this is the best summary of the problem that I've seen so far.
- crooked-v 8y agoThe third factor to add to your list is that the design of MCAS makes the plane unrecoverable in some situations. On the Ethiopia Air flight, it looks increasingly like the pilots knew what to do, but even after MCAS was disabled it was impossible to recover control because once trim was maxed out, adjusting the physical control trim wheels may have literally taken more brute strength than the pilots had, there was no way to reactivate electric trim control without also reactivating MCAS, and going nose-down to reduce load on the control surfaces to allow manual trim adjustment was infeasible because this all happened at 1000 ft. altitude.
- treis 8y ago>No re-training of pilots: Pilots were not aware of new ways in which the plane might take command away from them, and were left in the dark with only seconds to react to a deadly situation Both the Lion Air and Ethiopian Air flights recovered from the initial MCAS. The mistake was assuming that pilots could reliably recover from a runaway trim situation. That might have been true when that was a more common failure and when pilots had more experience flying with manual trim.
- cjbprime 8y agoAgree with you, though as a small correction it now appears (according to Ethiopian preliminary report) they made it to 7k altitude AGL, not 1k AGL. Still not so much to work with when you're above the plane's max airspeed and trimmed all the way down.