- Pitot tubes are heated. Weather conditions on FL 30 and up are pretty stable, so pitot tubes either freeze over daily or never.
- The misaligned speed indications lasted less than a minute, after which all three speed indications returned the same approximate value again.
- The pilots noticed they were in alternate law (see voice recorder transcripts), so they should've been trained to input perfect steering commands from then on.
- Trained pilots must have noticed a hard stall, after temporarily climbing up to FL35 (see recorded data)
- Whatever feeling the pilots may had after they've been falling like a rock for 2 consecutive minutes, they are trained to rely on instruments, not gut feelings. The altitude meter has a backup that is not dependent on the pitot tubes. Radar altimeters? Barometers? Inner ear pressure? Squeaks in cabin panels from rapid pressure changes? GPS-inferred altitude, no matter how imprecise they may be? A sustained, rapid descent that doesn't resolve through a nose-up attitude with full power applied must, to a trained pilot, seem like a true stall or a control surface wreaking havoc.
"Luck" should have no place in modern aviation. This is not a lottery. It's either design flaws, failed procedures or pilot error.
And we don't managed to rule out PAX-induced cellphone EMI as a confounding factor in this case. We know the speed indicators were unreliable for a minute and *think* it was the pitot tubes. I'm not saying it was, but it *could* have been interference.
There's still some unclear points:
- Automatically and silently disabling a stall warning at low speeds is a decision that can't naively be understood, since low speeds are a major potential reason for stalling the plane. What's the reason behind that?
- Airbus procedures that command a full nose up in response to a stall seem even more cryptic, especially when conducted at FL30 with plenty of room to turn the nose down to regain speed. A Nose-up, speed-up close to coffin-corner airspace seems very counter-intuitive. I can't think of a compelling reason for that, so there's a [citation needed].