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>Are physics computer simulations (e.g. aerodynamic flow[0]) realistic enough that engineers could have predicted the tendency for the nose to push up into a st

>Are physics computer simulations (e.g. aerodynamic flow[0]) realistic enough that engineers could have predicted the tendency for the nose to push up into a stall with the forward-mounted bigger engines while still at the CAD drawing stage? (Place some engines on the drawing with X amount of specified thrust, move them forward on the wing, then run a simulation, etc.) Or is the interaction of behavior so complex or so subtle that they had to build the real thing before realizing "Oops, our internal test pilots just noticed the plane is unstable and it looks like we need a software augmentation system!" Yes. They knew full well that the MAX would do that in circumstances where a normal 737 would not. There is nothing wrong with the MAX's performance characteristics. The aircraft itself is perfectly safe to fly. What isn't safe is the half baked MCAS system they used to deal with that edge case so they could avoid having to retrain pilots.

jasode 8y ago
>Yes. They knew full well that the MAX would do that in circumstances where a normal 737 would not. To be clear, you're saying Boeing engineers knew this as early as the CAD drawing stage?
- dsfyu404ed 8y ago
  Probably. A bunch of engineers who do that stuff every day are going to look at the prints and be able to infer the implications on handling. They probably couldn't predict exactly what circumstances would cause the pitch up behavior to manifest itself or whether those circumstances would have even been within the flight envelope but they would have known how moving the engines up and forward would have affected handling. Any automotive engineer who designs that stuff can look at a vehicle suspension and give you a rough estimate of how the vehicle will handle under certain circumstances. People who are well versed in boat hulls can look at a shape and make the same inferences. Yes, commercial airline designers should be able to look at a design and have a rough idea of how it will handle. It's not magic. It's physics. If your day job involved understanding that niche of applications you should be able to look at it and draw some rough conclusions.
simion314 8y ago
>There is nothing wrong with the MAX's performance characteristics. The aircraft itself is perfectly safe to fly How do we know? because the FAA approval is not ensuring me that there are not any other problematic systems where Beoing self approved the corner cuts they made. IMO a full re-approval is needed with a trust worthy institution is needed before you can claim that the airplane is "perfectly safe"
- cmurf 8y ago
  FAR 25, perhaps specifically 25.171-25.181 related to stability but there are separate sections on stall behavior, controllability, maneuverability, performance, etc. Those things must be demonstrated to get an airworthiness certificate under that part. Is this FAR all encompassing of that which makes an airplane safe or not? Because we have an airplane that was so certified, and yet we have two crashes that directly contradict their safety (hence they're grounded). I'm less concerned that these planes are somehow, without computers, not complying with FAR 25. I'm more concerned that Boeing (and FAA) will accept a software only fix, and continue to avoid a type certificate for this derivative model aircraft, and thus avoid any additional training for pilots. Basically, I expect Boeing will take the full hit, i.e. the software was flawed and now it is fixed, so that airlines won't be dinged for any on-going training requirement. Thus far the market isn't significantly dinging Boeing's value. Today's price is the same as it was in September of last year before either accident happened. The market is effectively saying those accidents don't matter that much, cost wise. Unless more information comes out that suggests there was wrong doing by either Boeing or the FAA. That could change the whole calculus.
  - simion314 8y ago
    I am not optimistic either, if the crashes happened in US then I am sure things would have been different.

jasode 8y ago

>Yes. They knew full well that the MAX would do that in circumstances where a normal 737 would not. To be clear, you're saying Boeing engineers knew this as early as the CAD drawing stage?

dsfyu404ed 8y ago
Probably. A bunch of engineers who do that stuff every day are going to look at the prints and be able to infer the implications on handling. They probably couldn't predict exactly what circumstances would cause the pitch up behavior to manifest itself or whether those circumstances would have even been within the flight envelope but they would have known how moving the engines up and forward would have affected handling. Any automotive engineer who designs that stuff can look at a vehicle suspension and give you a rough estimate of how the vehicle will handle under certain circumstances. People who are well versed in boat hulls can look at a shape and make the same inferences. Yes, commercial airline designers should be able to look at a design and have a rough idea of how it will handle. It's not magic. It's physics. If your day job involved understanding that niche of applications you should be able to look at it and draw some rough conclusions.

simion314 8y ago

>There is nothing wrong with the MAX's performance characteristics. The aircraft itself is perfectly safe to fly How do we know? because the FAA approval is not ensuring me that there are not any other problematic systems where Beoing self approved the corner cuts they made. IMO a full re-approval is needed with a trust worthy institution is needed before you can claim that the airplane is "perfectly safe"

cmurf 8y ago
FAR 25, perhaps specifically 25.171-25.181 related to stability but there are separate sections on stall behavior, controllability, maneuverability, performance, etc. Those things must be demonstrated to get an airworthiness certificate under that part. Is this FAR all encompassing of that which makes an airplane safe or not? Because we have an airplane that was so certified, and yet we have two crashes that directly contradict their safety (hence they're grounded). I'm less concerned that these planes are somehow, without computers, not complying with FAR 25. I'm more concerned that Boeing (and FAA) will accept a software only fix, and continue to avoid a type certificate for this derivative model aircraft, and thus avoid any additional training for pilots. Basically, I expect Boeing will take the full hit, i.e. the software was flawed and now it is fixed, so that airlines won't be dinged for any on-going training requirement. Thus far the market isn't significantly dinging Boeing's value. Today's price is the same as it was in September of last year before either accident happened. The market is effectively saying those accidents don't matter that much, cost wise. Unless more information comes out that suggests there was wrong doing by either Boeing or the FAA. That could change the whole calculus.
- simion314 8y ago
  I am not optimistic either, if the crashes happened in US then I am sure things would have been different.