I am sure this will be blamed on pilot error, but it was really an algorithm that killed the people on Lion Air flight JT610. I was wrong about the IRS malfunctioning, though I was very much in the right neighborhood. It was probably the angle of attack sensor which performs a similar function of measuring attitude that malfunctioned.
I also wasn’t aware that the 737 MAX had a new system that performed automatic pitch control adjustments with no pilot input based on the AOA sensor. This sounds like a truly terrible idea to me. Why does it not check with the IRS? Surely there must be a good reason for that but I can’t think of one. Sure the IRS could be wrong but it’s far more likely the AOA will be wrong since it’s an externally-mounted physical sensor. This automated pitch control system that relies on only one sensor (this is a big no-no in this arena) sounds truly moronic and it will likely result in more crashes as currently designed IMO.
The pilots could’ve still gotten accurate attitude information and survived this AOA problem, though. On the ADIRU where the IRS-related stuff is located, you can flip the switch to ATT and this will show you the plane’s actual attitude independent of the AOA sensors. I don’t remember the procedure well enough to recall what position the ADIRU is supposed to be in during takeoff and am too lazy to look it up but it’s just a knob you turn to get attitude and heading.
Regardless, it sounds like only one AOA sensor was malfunctioning. Hard to tell from the stories so far. If so, the pilot and co-pilot would’ve had contradictory information and should’ve switched that system off — if they had time.
Like I said, it was an algorithm that killed those people, not really the pilots. When alarms are blaring, you’re at pretty low altitude and the nose keeps pitching down with no explanation, most people are going to be hard-pressed to make sense of it before it’s too late.
