- It was originally intended to have an authority of +/- 0.6 degrees of trim
- Later it was discovered that this it not enough due to the aerodynamic effects of the engines becoming apparent also at lower speeds, which led boeing to increase authority to +/- 2.5 degrees per iteration with unlimited iterations until the maximum range
If you don't believe me, see pprune.org (real pilots discussing the issue) and https://www.satcom.guru/2018/11/stabilizer-trim.html
This is not a software fault.
This whole thing smells like a bunch of dodgy decisions. Some of them recent and others historical. For instance not being able to manually adjust trim while the elevator is under load. That's dodgy, they got away with it because runaway trim is really rare.
If we assume MCAS is only disabled in an emergency, we don't want the result of cutting out an automated system to be further automatic manipulation of the control surfaces, right? That's one more weird behavior for the pilots to have to keep in their situational awareness while doing the most important step (i.e. flying the plane).
You have two separate things a pilot may need to do. One is disabling the MCAS control action. In that case you do want it to return to normal trim. Second is disabling the Automatic/Electrical Trim. In that case you want it to stop and allow the pilot to set the trim manually.
However if you kill the power to the trim motor and then turn it back on MCAS will blindly add more trim on top of the trim it previously added. It doesn't remember how much trim it's already applied.
For a start, by not ramming an essentially new type through all test flying & certfication testing in 17 months before declaring it ready for service.
There is a reason that the Soviet Ministry of Aviation made newly-approved types fly only cargo and mail for a year or more; not just because their techniques were 'unsophisticated' per the Western view but also because they understood that introducing a complex system into a complex environment of weather and human factors couldn't be fully modelled but had to be subjected to prolonged real-World experience.
From what I have read it sounds like part of the problem is that manually adjusting the trim wheel requires more strength than at least some pilots possess due to the mechanical forces on the plane. I don't think it's reasonable to expect simulators to replicate those types of forces.
As with what potentially happened to these crashes, the operating procedures might not be fully known by the pilot. The simulation might also allow the simulated pilot to do things that humans can't, for example turn the trim wheel when the jackscrew is under heavy load from the nose being pitched down.
Wow that's harsh. You may want to add a bit of sugar to that; it's not nice addressing fellow developers like that. Just a thought.
The AOA calculation is also much more complicated than the article explains. There is a speed element, engine power, etc.
The sensor simply measures the angle of the airflow with respect to the airframe.
In fact it is just a free-moving surface attached to the airframe.
Classic 737s climb via trim, not constant stick inputs. This has changed slightly with the MAX but now you have automated AoA correction (involving trim). That's a nasty combination.
So, you have reviewed the software? If it's so stupid simple, why did it kill a bunch of people?
There is no lower limit on the complexity of a system required to kill people.
So, you're essentially parroting Boeing's narrative IMO. Yes, they want you to think that the system is 'stupid simple' and it's 'no big deal, just one little fix' because obviously that's good for their business.
Maybe, the system required for safe operation is not so simple, and Boeing is no longer competent enough to create a system. Perhaps the 'stupid simple' system was all they were able to muster.
I'm not sure why you think boeing would lie about it. Or how they'd convince the regulators in two different countries to cover it up since you can see the behaviour by reading the graphs in the preliminary report.