a98u13c5 wrote:
Looks like the old adage 'you get what you pay for' holds true today, when the oversight is poor in Ethiopia also.
Hard to believe they would buy the "safety lite" option, but that's business for you, especially on the cheap.
But as was shown in other events, even the "safety lite" system is robust enough if the personnel have well training.
You obviously haven't read the report have you?
They followed Boeing's post Lion Air instructions to the letter. However, what Boeing didn't say in their AD, possibly because they didn't realize, is that above a certain speed the aerodynamic forces on the horizontal stabilizer are too great for it to be cranked manually. So the pilots, faced with an aircraft that was loosing height and gaining speed, turned the two cut switches to the trim motor back on so they could use the electric trim to try to get the aircraft back under control. Unfortunately at that point the MCAS, which was still lurking in the background, (it's impossible to shut off) saw its chance and immediately sent a nose down demand to the motor. 18 seconds later it was game over, the aircraft hit the ground 40° nose down at about 500 kts.
I'm not sure what you mean when you say this aircraft was 'safety lite'. I assume you are referring to the basic option for the MAX which is to have an AOA DISAGREE light on the panel. This is the same system as used on the NG and there are over 7,000 of them flying. This was the option chosen by most of the low cost operators, including SouthWest. Following Lion Air many airlines opted for the additional software package to add the AOA Disagree to either the Heads Up Display or the Heads Down Display. After Lion Air that package became standard on new airplanes. Anyway, I'm not sure what difference this would have made when you are climbing at a normal AOA but the stall warning is blaring, the stick shaker is going mad and you have one sensor telling you that your angle of attack is over 70° you don't need a pretty screen to tell you something is wrong.
The two AOA systems gave wildly different readings, at one point the left AOA value reached 74.5° while the right AOA was reading 15.3°. Similar discrepancies also existed in airspeed and altitude readings, at the time of the crash they were: Left Indicated Airspeed approximately 458 kts and the right Indicated Airspeed, 500 kts. The last recorded pressure altitude was 5,419 ft on the left and 8,399 ft on the right. The MCAS only takes data from one sensor and it looks like it uses that input in other calculations as the left indicated altitude was a couple of thousand feet below ground level.
