3 ms·
You missed the big one that even made MCAS necessary: 0. Reposition the engine forward on the wing such that the airframe is inherently unstable and needs soft
by petilon 7y ago
You missed the big one that even made MCAS necessary:
0. Reposition the engine forward on the wing such that the airframe is inherently unstable and needs software for stabilization.
- mseidl 7y agoPlus if I remember they didn't mention the MCAS anywhere?
- sokoloff 7y agoThe airframe is not unstable. It exhibits positive longitudinal aerodynamic stability. It’s positively but insufficiently stable to meet certification requirements, which is what required them to add MCAS. MCAS is nowhere near fast enough to compensate if the Max were actually unstable.
- petilon 7y ago> insufficiently stable to meet certification requirements Sounds like unstable to me. "I am not fat, I am just insufficiently thin".
- na85 7y agoIt's stable. In aerodynamics, stability has a specific meaning and it's possible for two things to be stable, and for one of those things to be less stable than the other. Picture a pendulum that is hinged on a greased axle vs one that is hinged on a high-friction axle. Both will reach equilibrium eventually (they're stable) but one will do it faster/with fewer oscillations. The 737 MAX is longitudinally stable, but it doesn't meet certain nuanced requirements of the Airworthiness regs.
- tim333 7y agoSeems so. More info here: https://www.quora.com/Is-the-Boeing-737-MAX-aerodynamically-unstable-I-have-read-that-the-new-heavier-and-higher-mounted-engines-have-changed-its-center-of-gravity/answer/Alan-Dicey https://www.quora.com/Is-the-Boeing-737-MAX-aerodynamically-... > what happens is that the stick force lessens as angle of attack increases at high AoA and low airspeed, whereas in order to be compliant with certification it has to gradually increase with increasing AoA, just like a 737–100.
- petilon 7y agoThere is so much doublespeak here. If it is less stable than required for airworthiness then it is not airworthy. Can we agree on that?
- na85 7y agoSure, but that doesn't mean it's unstable.
- petilon 7y agoIf it is not stable enough then it is unstable. Where do you draw the bar on stability, if not airworthiness?
- na85 7y ago>If it is not stable enough then it is unstable. Nope, sorry, that's not what stability and instability mean. Stability means it will return to equilibrium if disturbed, but the issue with the MAX is that it requires a positive force gradient per the Part 25 Airworthiness Regulations, which the MAX does not exhibit in a specific part of the envelope. Stability is not a binary condition. The MAX is longitudinally stable in every part of the flight envelope. "Not airworthy" does not equate to "unstable". Those two terms are orthogonal.
- throwaway3563 7y agoWhat I’ve learned from these 737 discussions: Anyone who uses the term “inherently unstable” is an armchair aerospace engineer. It’s such a vague weasely term.
- petilon 7y agoWould you prefer "insufficiently stable" instead? The kinds of mistakes Boeing made are so basic that even laypersons can immediately understand it. Like not having redundant sensors. Like fixing a hardware problem using software. See this video about the plane's tendency to pitch up at low speed and full thrust. That's "insufficiently stable"! https://www.youtube.com/watch?v=6p5sboD2oO8 https://www.youtube.com/watch?v=6p5sboD2oO8
- deleted 7y ago[deleted]