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Citation? This is a very significant claim if true, it would be a clear violation of FAR 25.173. I don't see how a plane is certified to be airworthy by softwar

by cmurf 8y ago

Citation? This is a very significant claim if true, it would be a clear violation of FAR 25.173. I don't see how a plane is certified to be airworthy by software work around, in particular one that can be disabled instantly rendering the plane not airworthy.

tyingq 8y ago
Not exactly as strong as "crack test pilot", but from the article: "after a few minutes of wrestling with the control yoke, the pilots on Flight 302 did invoke the checklist procedure, and moved the STAB TRIM switches to CUTOUT. The stabilizer then stopped responding to MCAS nose-down commands, but the pilots were unable to regain control of the airplane."
- cmurf 8y ago
  That is due to the mistrim situation that a perturbed MCAS had already put the plane into. Proposing that without MCAS (from the outset) the aircraft is inherently unstable is what I'm questioning.
  - mike_john23 8y ago
    You can see the previous flight made by the same lion air plane that crashed here[1]. They not only did not declare an emergency but they contained the flight as normal and flew for over an hour with no MCAS and no electric trim. [1]: https://leehamnews.com/wp-content/uploads/2018/11/Previous-flight.png https://leehamnews.com/wp-content/uploads/2018/11/Previous-f... I should point out they found the stab cut out procedure by trial and error and were able to maintain control of the plane simply by counteracting the errant downward trim. The reason the Ethiopian plane crashed is that they didn't execute the airspeed disagree procedure and left the throttles on basically maximum. Yes MCAS is an issue, But since no one on this site has gotten this right I might as well point that out
    - cmurf 8y ago
      On what basis do they follow the IAS disagree procedure, and not the procedure in emergency AD 2018-23-51? KNKT's preliminary report says the prior flight, Lion Air 34, was not airworthy due to continuous stick shaker activation. Further, that flight expressly requested a much lower altitude, citing control problems for that request. Neither are normal.
    - cjbprime 8y ago
      You're saying that IAS disagree and unreliable airspeed ought to have caused them to throttle down? That seems counter-intuitive. If you don't know how fast you're going, how are you supposed to avoid stalling? Are you looking at a specific QRH entry? What does it say?
kevin_thibedeau 8y ago
Egypt air pilots performed the recovery procedure and still crashed. Pretty damning evidence that it can't fly safely with MCAS off.
- cmurf 8y ago
  Post hoc ergo propter hoc is a logical fallacy. Very basic. MCAS caused the extreme mistrim that resulted in the crash. Turning it off does not solve the mistrim.
  - kevin_thibedeau 8y ago
    The procedure includes manually correcting the trim. It didn't work.

by cmurf 8y ago

tyingq 8y ago

Not exactly as strong as "crack test pilot", but from the article: "after a few minutes of wrestling with the control yoke, the pilots on Flight 302 did invoke the checklist procedure, and moved the STAB TRIM switches to CUTOUT. The stabilizer then stopped responding to MCAS nose-down commands, but the pilots were unable to regain control of the airplane."

cmurf 8y ago
That is due to the mistrim situation that a perturbed MCAS had already put the plane into. Proposing that without MCAS (from the outset) the aircraft is inherently unstable is what I'm questioning.
- mike_john23 8y ago
  You can see the previous flight made by the same lion air plane that crashed here[1]. They not only did not declare an emergency but they contained the flight as normal and flew for over an hour with no MCAS and no electric trim. [1]: https://leehamnews.com/wp-content/uploads/2018/11/Previous-flight.png https://leehamnews.com/wp-content/uploads/2018/11/Previous-f... I should point out they found the stab cut out procedure by trial and error and were able to maintain control of the plane simply by counteracting the errant downward trim. The reason the Ethiopian plane crashed is that they didn't execute the airspeed disagree procedure and left the throttles on basically maximum. Yes MCAS is an issue, But since no one on this site has gotten this right I might as well point that out
  - cmurf 8y ago
    On what basis do they follow the IAS disagree procedure, and not the procedure in emergency AD 2018-23-51? KNKT's preliminary report says the prior flight, Lion Air 34, was not airworthy due to continuous stick shaker activation. Further, that flight expressly requested a much lower altitude, citing control problems for that request. Neither are normal.
  - cjbprime 8y ago
    You're saying that IAS disagree and unreliable airspeed ought to have caused them to throttle down? That seems counter-intuitive. If you don't know how fast you're going, how are you supposed to avoid stalling? Are you looking at a specific QRH entry? What does it say?

kevin_thibedeau 8y ago

Egypt air pilots performed the recovery procedure and still crashed. Pretty damning evidence that it can't fly safely with MCAS off.

cmurf 8y ago
Post hoc ergo propter hoc is a logical fallacy. Very basic. MCAS caused the extreme mistrim that resulted in the crash. Turning it off does not solve the mistrim.
- kevin_thibedeau 8y ago
  The procedure includes manually correcting the trim. It didn't work.