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Things are not so simple as the pilots knowing everything and just hiding the truth. They still identified there was an issue, but couldn’t match it to MCAS as

by hrktb 7y ago

Things are not so simple as the pilots knowing everything and just hiding the truth. They still identified there was an issue, but couldn’t match it to MCAS as they didn’t know about it, and misattributed the effects to a simulator error. > As the two pilots banter back and forth in the messages, Forkner says the system is "running rampant in the sim on me," then adding, "I'm leveling off at like 4000 ft, 230 knots and the plane is trimming itself like crazy." For me this clears the bar of pilots detecting there is an issue.

missosoup 7y ago
The pilots knew about MCAS. What the texts indicate is the behaviour of MCAS was changed during testing without the pilots being informed, and the pilots also failing to report that change despite becoming aware of it. This was certainly a contributing factor to the events that occurred later, but not at all the smoking gun that the title implies. Forkner: "Oh shocker alerT! MCAS is now active down to M .2 [mach 0.2] It's running rampant in the sim on me at least that's what Vince thinks is happening"
bonzini 7y ago
The issue that resulted in the crashes was angle of attack sensors reporting broken data, which caused MCAS to nose down the plane; this is absolutely not what the pilots are talking about. Everything else that has been discussed (whether the pilots should have been told how to disable it and tried it in the simulator, whether Boeing should have added the second vane or even a third one on all planes, etc.) fundamentally depends on having incorrect data from the sensors and the plane not being able to deal with that. The exchange might hint that MCAS had an awful design history, but even a perfect MCAS could have had issues if supplied with incorrect sensor data; garbage in, garbage out. Now if there was somewhere an email about the lack of a voting system on vane readings, that would be another story.
- mannykannot 7y ago
  The issue is the undocumented (and obfuscated) behavior of the airplane after the failure of a single AofA sensor.
  - bonzini 7y ago
    Right, and it has nothing to do with the issue reported by the test pilots in the simulator.
    - mannykannot 7y ago
      I see what you mean - there is no evidence (at least in the transcript) that the problems were in response to a simulated system failure, and the actual MCAS seemed to work well enough when nothing was broken.
mannykannot 7y ago
It is not clear from the transcript whether it was a misattribution when they attributed the problems they were discussing to the simulator. It also seems clear that they were not getting flying time on the actual airplane, and so were not in a position to know if the airplane itself had problems. There are definitely issues to be investigated here, and it is not going to be helped if people are taking the fifth, as Forkner himself has done. He might want to reconsider that.

by hrktb 7y ago

missosoup 7y ago

The pilots knew about MCAS. What the texts indicate is the behaviour of MCAS was changed during testing without the pilots being informed, and the pilots also failing to report that change despite becoming aware of it. This was certainly a contributing factor to the events that occurred later, but not at all the smoking gun that the title implies. Forkner: "Oh shocker alerT! MCAS is now active down to M .2 [mach 0.2] It's running rampant in the sim on me at least that's what Vince thinks is happening"

bonzini 7y ago

The issue that resulted in the crashes was angle of attack sensors reporting broken data, which caused MCAS to nose down the plane; this is absolutely not what the pilots are talking about. Everything else that has been discussed (whether the pilots should have been told how to disable it and tried it in the simulator, whether Boeing should have added the second vane or even a third one on all planes, etc.) fundamentally depends on having incorrect data from the sensors and the plane not being able to deal with that. The exchange might hint that MCAS had an awful design history, but even a perfect MCAS could have had issues if supplied with incorrect sensor data; garbage in, garbage out. Now if there was somewhere an email about the lack of a voting system on vane readings, that would be another story.

mannykannot 7y ago
The issue is the undocumented (and obfuscated) behavior of the airplane after the failure of a single AofA sensor.
- bonzini 7y ago
  Right, and it has nothing to do with the issue reported by the test pilots in the simulator.
  - mannykannot 7y ago
    I see what you mean - there is no evidence (at least in the transcript) that the problems were in response to a simulated system failure, and the actual MCAS seemed to work well enough when nothing was broken.

mannykannot 7y ago

It is not clear from the transcript whether it was a misattribution when they attributed the problems they were discussing to the simulator. It also seems clear that they were not getting flying time on the actual airplane, and so were not in a position to know if the airplane itself had problems. There are definitely issues to be investigated here, and it is not going to be helped if people are taking the fifth, as Forkner himself has done. He might want to reconsider that.