Originally Posted by
Smythe
The AoA measurement vane with the calibration and usefulness, is not a science but an art. To rely on the AoA measurement, especially on a DEP climb (forget if there is a turn) to be able to determine if the ac is near stall is simply voodoo engineering.
Some enlightened reading would be on the calibration, latency, and overall algorithms created to try to make some use of the readings. The AOA readings must be coupled with airspeed, weight, flaps settings, and winds aloft.
Front landing gear doors open, sideslip, vertical winds, and of course, banked turns...all render the readings useless without an algorithm.
Last algorithm went from 0.5 degrees to 2.5 degrees to make it work....and we see how that went.
Add yet another algorithm that they 'think' might work. (but didnt they already do that?)
I think that you are nearer the mark than most other posts. I am still seeing posts that A/P should be engaged to overcome trim runaway (contrary to Boeing revised OP). Currently, all there is to go on is the Lion Air FDR. However, there are material differences between the "previous flight" and the doomed flight data. It would appear that issues are far more complicated than it may first appear. At the heart of the issues are the algorithms that process the AoA and computed air speed. The doomed flight had stick shaker on take-off rotation unlike the previous flight (stick shaker started at an altitude about 400ft). The published data does not include all the parameters available.
It is not known how the MCAS system actually works. Obviously, somebody at Boeing knows precisely how it works, but they are not going to be posting on PPRUNE any time soon. The real info will be supplied by depositions. The contributions here, are educated guesses based on the limited information available. Even so, it seems that the Preliminary Report into Lion Air may have been too casual about the potential risks. Boeing may have been to casual about the risks. There are some obvious defects in the MCAS system, even from the scant information available. Those defects may be complicated or exacerbated by the changes to the aircraft's flight characteristics in the MAX design. In short, Boeing will have a lot of explaining to do to restore confidence.