Re: If it was a real spin on a 737 and he had to try to take it out of it....
I'm not yet sure if the plane is safe to fly? MCAS is there because if you pull back on the stick and hold it at a certain angle the plane won't always maintain the expected continuous climb, but might go into an increasingly steep climb - then stall. That's caused by the engine cowlings generating increasing lift as the angle-of-attack increases.
As I understand it, that's enough for the plane to fail to get certified as airworthy. However I've not read how serious it is - or how easy to recover from once the process starts.
Hence MCAS.
On the other hand, MCAS was only certified to have authority for a 0.6° total trim adjustment to the stabiliser. Making it only a moderate safety risk, and allowing it to get away with only having one sensor. Which is minor, and suggests MCAS isn't that important, it's just there to make the plane tick the boxes.
On the gripping hand, according to the Seattle Times, Boeing allowed MCAS to exceed that authority after flight testing. Now it has authority for 2.5° of trim change - 4 times what it says in the certification documents! That would move it up the safety critcal list, and mean it might have needed more work, or more sensors. So does that just mean MCAS didn't work as expected during testing, or that they found it needed to be much beefier, because the plane wasn't safe without it, or something else?
Separately there appears to be a bug in the MCAS design. As it doesn't limit itself even to 2.5° - it just keeps on adjusting trim every ten seconds, if the sensor is faulty.
Basically it's flaws all the way down. Which leads me to suspect that with trust in Boeing at a low ebb, this is going to take at least 6 months to sort. And European regulators have far less incentive to rush to re-certify, as Boeing compete with Airbus, and most of the European airlines who ordered the new 737s haven't taken delivery yet.
Biting the hand that feeds IT
