| > No, it was not unstable. It just behaved differently enough that some additional pilot training would have been needed without MCAS. Quoting Boeing with my own emphasis: > MCAS, or Maneuvering Characteristics Augmentation System, is a flight control law implemented on the newer models of the 737 to provide consistent airplane handling characteristics at elevated Angles of Attack in certain unusual flight conditions only. Which, to be clear, means it's intended to stabilize the plane ("consistent") in circumstances where the physical design of the plane would render the plane unstable (inconsistent) in certain operating environments. > The EA made a different mistake - turning off the trim when it was too far from neutral. Do you have a specific citation for this? I'm digging through the ECAA report and am not able to find this specific mention. https://web.archive.org/web/20200310004955/http://www.aib.go... (original site is timing out) --- It seems you're generally suggesting that the instructions provided by Boeing were sufficient for the plane to remain airworthy without further mitigation; this was contradicted by the ECAA and others. Is this what you're suggesting? |
Stability has a different meaning when applied to aerodynamic characteristics than they way you mean it (i.e. consistency). Stability in aerodynamics means if you push something off-center, it will return to center. Unstable means it will go further off-center.
Unstable is like balancing a pencil on its point. The slightest perturbation will cause it to fall over.
> Do you have a specific citation for this?
Aviation Week 19-Sep-2019
" The MCAS activated twice, and the crew countered with electric trim. Unlike the JT610 pilots, the ET302 crew flipped the stabilizer trim motor cut out switches, which stopped the MCAS from moving the stabilizer. But after reporting not being able to manually trim the aircraft, they flipped the cut out switches on again. The faulty AOA data was still feeding the left-side FCC, activating the MCAS again and putting the aircraft into a dive."
(The airplane was already in a dive when they turned off the stab trim.)
> It seems you're generally suggesting that the instructions provided by Boeing were sufficient for the plane to remain airworthy without further mitigation; this was contradicted by the ECAA and others. Is this what you're suggesting?
Yes. In fact, on the flight immediately preceding the LA crash, the same MCAS problem was experienced, and the crew returned the trim to normal with the electric trim switches and then cut off the stab trim. They landed safely without further incident.
Exactly what Boeing's EAD stated to do.