4 ms·

Interactive visualisation of 737 Max MCAS system

14 points by miohtama 8y ago

birdiesanders 8y ago
This clears up a lot of how this happened. A system that does not have an upper limit on number of corrections is dangerous. A system that relies on one single sensor is dangerous. A system that has both flaws is lethal.
cmurf 8y ago
I'm disappointed that MCAS is still being made primarily about stall avoidance and the idea that a stall means good chance (let alone certain chance) of a crash. A pilot is required to understand and demostrate competency in approach to stall, full stall, and stall recovery for category/class rating and also for type rating. The purpose of MCAS is to moderate the pitch up due to the aerodynamic lift the new nacelles produce in high angles of attack. But it did so with such aggression that it made it possible, perhaps even likely, that it would result in sufficient mistrim and high airspeed as to make it difficult to correct in a low altitude scenario until it was too late. It was a one size fits all correction, and it was abrupt, regardless of airspeed, which is rather significantly a problem at high airspeeds that would cause a problem even if high angle of attack were true. The graphic also ignores that MCAS accepts absurd angle of attack values as actionable. In the Ethiopian Airlines case, 75 degrees is a nonsense value, there's no point in correcting for it. In effect, they made it both too simple, and deadly.
- Doxin 8y ago
  The problem with the 737 MAX is that it can get into a stall from which you cannot recover. It doesn't behave the same as a regular 737 at all, which in turn means that the actions needed to prevent a stall are wildly different. In a regular 737 you apply more throttle in a stall to get more lift. In a 737 MAX applying more throttle will point the plane even more nose-up worsening an already bad situation.
  - cmurf 8y ago
    Do you have a citation for this? Getting into an unrecoverable stall is a violation of FAR 25.203(c).
    - Doxin 8y ago
      I should've been more specific: unrecoverable using the old procedures And I'll be honest I'm rather an armchair expert here, so I don't have any citations to back up above claims.
acqq 8y ago
> As part of the update, the company said Max pilots would need to receive an additional 30-minute training program on the software. But on an iPad! Boeing is still pretending that the training on the new simulator is not needed. In fact there are almost no new simulators at all — the MAX’s selling point was that it’s the same as the old 737. And that was a very deadly lie. Still, even after the software patch, with MCAS turned on, the plane pretends to behave as the old one. Once MCAS is switched off, a pilot is left with a new plane. For which he is not trained! And exactly at the moment the plane is already in danger! Because Boeing’s marketing. The obviousness of the plane not being the same is an exact reason why Boeing tried to hide the existence of MCAS completely. Now they still think everything is allowed to them.

14 points by miohtama 8y ago

This clears up a lot of how this happened. A system that does not have an upper limit on number of corrections is dangerous. A system that relies on one single sensor is dangerous. A system that has both flaws is lethal.

cmurf 8y ago

I'm disappointed that MCAS is still being made primarily about stall avoidance and the idea that a stall means good chance (let alone certain chance) of a crash. A pilot is required to understand and demostrate competency in approach to stall, full stall, and stall recovery for category/class rating and also for type rating. The purpose of MCAS is to moderate the pitch up due to the aerodynamic lift the new nacelles produce in high angles of attack. But it did so with such aggression that it made it possible, perhaps even likely, that it would result in sufficient mistrim and high airspeed as to make it difficult to correct in a low altitude scenario until it was too late. It was a one size fits all correction, and it was abrupt, regardless of airspeed, which is rather significantly a problem at high airspeeds that would cause a problem even if high angle of attack were true. The graphic also ignores that MCAS accepts absurd angle of attack values as actionable. In the Ethiopian Airlines case, 75 degrees is a nonsense value, there's no point in correcting for it. In effect, they made it both too simple, and deadly.

Doxin 8y ago
The problem with the 737 MAX is that it can get into a stall from which you cannot recover. It doesn't behave the same as a regular 737 at all, which in turn means that the actions needed to prevent a stall are wildly different. In a regular 737 you apply more throttle in a stall to get more lift. In a 737 MAX applying more throttle will point the plane even more nose-up worsening an already bad situation.
- cmurf 8y ago
  Do you have a citation for this? Getting into an unrecoverable stall is a violation of FAR 25.203(c).
  - Doxin 8y ago
    I should've been more specific: unrecoverable using the old procedures And I'll be honest I'm rather an armchair expert here, so I don't have any citations to back up above claims.

acqq 8y ago

> As part of the update, the company said Max pilots would need to receive an additional 30-minute training program on the software. But on an iPad! Boeing is still pretending that the training on the new simulator is not needed. In fact there are almost no new simulators at all — the MAX’s selling point was that it’s the same as the old 737. And that was a very deadly lie. Still, even after the software patch, with MCAS turned on, the plane pretends to behave as the old one. Once MCAS is switched off, a pilot is left with a new plane. For which he is not trained! And exactly at the moment the plane is already in danger! Because Boeing’s marketing. The obviousness of the plane not being the same is an exact reason why Boeing tried to hide the existence of MCAS completely. Now they still think everything is allowed to them.