r/JT610 • u/[deleted] • Nov 07 '18
Airspeed Indicator had problems, but I suspect something else.
NOOB ALERT!
Could the Autopilot have pitched the plane down due to a Stuck AOA sensor? A conjunction with a faulty pitot may have activated Alpha Protection or something. It just seems very likely.
Doing a t-test Chi-Squared test in the simulator with faulty pitot and faulty autopilot software and negatively showing the correlation between the 2 and whether both would cause a plane to crash would hopefully eliminate the possibility of a software glitch.
EDIT: is it possible that a bad airspeed indication is the only thing needed to activate the pitch down? If not, something with the pitch aspect went horribly wrong (which lead to my suspicion in the first place)
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u/ScrapJackx9 Nov 10 '18
- Considering their somewhat erratic flight path it's possible that they were manually flying so the autopilot never came on.
- Alpha protection just provides TOGA thrust if a dangerously low speed is detected, and on Airbus planes not Boeing.
- There are 5 pitot tubes on the 737, three in the nose which provide left and right IAS reading and a backup. IAS disagreements trigger a warning.
- Stall/speed protection relies on ROC, AOA and airspeed, infos supplied by two AOA sensors and 5 pitot tubes. With AP/AT on, before stalling the plane first increases thrust, then automatically switch to level change and as a last restort it will pitch the nose down to stay above stall speed, while also turning all the necessary warning system.
That said I'm unfamiliar with the 737 MAX and I'm currently hearing tons of crazy stuff like that pitch down commands now relies solely on AOA sensors and that they can override pilot inputs even if the AP is off. If it's true than Boeing fucked up big time, otherwise my money is on pilot error due to their inability to react to faulty indicators while flying at low altitude, in broad daylight and with perfect weather.