* Posts by camber

2 posts • joined 3 Apr 2019

We don't know whether 737 Max MCAS update is coming or Boeing: Anti-stall safety fix delayed


Re: "he MAX is probably no worse than the previous 737 NG model in this respect"

The MAX is probably no worse than the NG in thrust-pitch coupling, as it's engines produce similar thrust levels roughly the same vertical distance below the wing as the NG. You are describing the aerodynamic effects of the bigger engines, which is definitely worse on the MAX. However, you are describing a pitch unstable or divergent aircraft at high AoA, as common with most current technical discussions. If true it's terrible and the MAX should not have been certified at all no matter good MCAS is...under certification rules the aircraft must still be able to be safely flown and landed without augmentation. It's more likely (but not known) that the MAX is less stable (not unstable) at high AoA, so it gets easier to pull through at high AoA but won't pitch up by itself at constant yoke input. In some ways this makes the bad implementation of MCAS worse, as it presents a lethal risk to solve a less critical deficiency.


Re: Question for the experts

As a participant on those forums (PPRune): the MCAS system is not to do with engine thrust. Although engines under the wing (when increasing thrust) tend to pitch the nose up, the MAX is probably no worse than the previous 737 NG model in this respect. Also the MCAS system is not an antistall system as described in the article, it is supposed to improve handling at high wing angles of attack near the stall. This is because the engine nacelles are large and forward of the wing, which reduces stability.The plane without MCAS gets easier to pull up near the stall, so the description is mostly but not totally wrong. MCAS doesn't take thrust into account.


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