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Notable and disturbing here is the lack of Max simulators in existence. It looks like neither Lion Air nor Ethiopian nor any US airline had access to one. Also

Notable and disturbing here is the lack of Max simulators in existence. It looks like neither Lion Air nor Ethiopian nor any US airline had access to one. Also linked in this article is the original FAA table of differences between the Max and other 737 models. It makes no metion of MCAS.

ajross 8y ago
Yeah. As much blame as Boeing and the FAA certification process seems to deserve here, it's worth pointing out how much of the cascade of failures is in the airlines and cockpits too. I mean, yes, the trim system was being driven by input from a single nonredundant sensor, which is a violation of the kind of engineering for failure process that airliners should be designed in. But at the same time that trim system is, by design, not strong enough to overpower pilot input to the other control surfaces. I mean, it's supposed to have been possible for the pilot to just fly the aircraft to a landing in the face of outrageous trim problems. But the actual pilots didn't, not because they weren't strong enough to push the yoke but because they simply didn't know what to do and didn't have the presence of mind to just yank hard on the controls. Somehow the culture of "just fly the ?!@#! plane" got lost in all those training iPads.
- tafda 8y ago
  Not true. https://www.seattletimes.com/business/boeing-aerospace/failed-certification-faa-missed-safety-issues-in-the-737-max-system-implicated-in-the-lion-air-crash/ https://www.seattletimes.com/business/boeing-aerospace/faile... Quote: The discrepancy over this number is magnified by another element in the System Safety Analysis: The limit of the system’s authority to move the tail applies each time MCAS is triggered. And it can be triggered multiple times, as it was on the Lion Air flight. One current FAA safety engineer said that every time the pilots on the Lion Air flight reset the switches on their control columns to pull the nose back up, MCAS would have kicked in again and “allowed new increments of 2.5 degrees.” “So once they pushed a couple of times, they were at full stop,” meaning at the full extent of the tail swivel, he said. Peter Lemme, a former Boeing flight controls engineer who is now an avionics and satellite-communications consultant, said that because MCAS reset each time it was used, “it effectively has unlimited authority.”
  - ajross 8y ago
    Yes true.[1] You're misunderstanding that quote. It's talking about "authority" in the sense of software's authorization to move the trim tab, not the aerodynamic authority of the tailplane. The 737 has a 60 year old, very conventional elevator with a trim tab. The tab changes the resting angle of the overall elevator, and thus the "center point" of tailplane force on the airframe. Being out of trim means that the aircraft might naturally want to pitch up or down, and forces the pilot to apply to force to the stick (which moves the elevator, not the trim tab!) to correct it. This stick force can be significant and surprising, but it's designed to (and the certification surely requires it to) be achievable by a pilot under all conditions. That is: it's not supposed to be possible for any trim failure on a 737 to render an aircraft uncontrollable, and I don't see any assertion in the analysis of the MAX 8 that changes that. At the end of the day, what happened here is that the aircraft had a runaway trim failure. That was a failure that was understood and forseen (albeit not under software control) in the aircraft's original design, and the redundancy to treat it was the pilot's physical ability to override the trim. This was supposed to have been a recoverable failure within the cockpit, and it wasn't. [1] Style note: why do people do this on the internet? Ah hah! You fool! You are WRONG! Stuff is complicated folks, be nice, assume competence, assume lack of malice, try to teach and not argue.
    - tzakrajs 8y ago
      Your footnote is really appreciated. I think there is a lot of trauma in this world and coping is a daily struggle for many of us. My hat is off to you.
      - wenc 8y ago
        I don't know -- in discourse, it's perfectly fine to dispute ideas (it's the foundation of Western civilization and of analytical thought, and is a means to knowledge and wisdom). If we cannot argue in a marketplace of ideas, we are prevented from having hard but necessary conversations. We need to adhere to parameters of civility of course, but to me, a necessary freedom is the freedom to disagree/dispute. Some ideas are truly wrong and they need to be put through the crucible. That said, I've always been told to always "address the ideas, not the person" (never attack someone's character) and to adopt a pose of "curiosity".
- outworlder 8y ago
  > But at the same time that trim system is, by design, not strong enough to overpower pilot input to the other control surfaces. That is incorrect for the 737 and many airliners. Elevator input is way less strong than trim. Trim moves the entire surface, not just the elevator control surface. I had the same misconception, my brain was translating GA aircraft knowledge to airliners.
  - DiffEq 8y ago
    The GA Aircraft; Cessna 182B has Stab trim.
    - sokoloff 8y ago
      Most light GA aircraft have a trim system that works by using a smaller trim surface to aerodynamically deflect the larger control surface. In such a system, the horizontal stabilizer has a fixed relationship to the fuselage. Later 182s definitely have this system (I owned a 182K for 16 years). Some light GA aircraft have systems with jackscrews that deflect the horizontal stabilizer as in airliners. These systems are more efficient aerodynamically, but can overpower pilot input, at least in theory. The aero trim system (in prior paragraph) cannot.
- lagolinguini 8y ago
  > But at the same time that trim system is, by design, not strong enough to overpower pilot input to the other control surfaces. No this is not true. In near stall situations for which the MCAS is designed, a full deflection of the elevators is not enough to counter the stabiliser effects. I'm not sure about the entire flight envelope, but I guarantee there are other situations where the elevator cannot counter the stabiliser. The right way to "regain control" isn't to overpower the stabiliser by inputs to other flight control surfaces, but to disable automatic stabiliser trim and manually trim the aircraft.
rnbrady 8y ago
> It makes no metion of MCAS. 27 - FLIGHT CONTROLS STABILIZER TRIM: Stab Trim cutout switches panel
- racingmars 8y ago
  Not sure what the meaning of your comment is. The Stab Trim cutout switches have been in the 737, in the same place aft of the flap selector, since the original 737. These were not a new feature related to the MCAS system.
  - AnimalMuppet 8y ago
    No, not a new feature. But don't they stop the ability of MCAS to change the trim?
    - racingmars 8y ago
      Yes, the "correct procedure" would be for the pilots to recognize the MCAS problem (whether they know about the existence of MCAS or not) as a runaway stab trim problem, and treat it as such. One of the steps for the runaway stab trim emergency checklist (which I believe is a memory item for 737 pilots) is to set the stab trim switches to cutoff. At that point, they can manually (with the wheels in the cockpit) return the stabilizer to a better trim position, then recover control of the aircraft. I'm not a real-world airliner pilot (I just play with them in simulators), so I can't comment on whether it's reasonable to expect pilots to recognize the situation and react accordingly in this new failure mode. Without knowledge of the existence of the MCAS system and how it can fail, with uncommanded nose-down, it's unclear that pilots would think there were any factors they recognize that would cause a runaway trim situation and think, "oh, I need to run the runaway trim checklist." I think that's the crux of the argument "any 737 pilot should have been competent to save the plane because they should have recognized runaway stab trim" versus "the set of conditions that caused this problem involved systems that pilots weren't trained on, so it's not reasonable for them to recognize what was happening and realize they can fall back on different training that they did have." Anyway... comment I was replying to seemed to imply the existence of the stab trim cutout switches implied that the MCAS system was made known to pilots, which is why I pointed out those switches had been there forever.
vt240 8y ago
The banner of the EAA website says they have a Full 737MAX simulator [1]. From this Press Release [2], it would seem they were rolling out in Oct, 2017. [1]: https://www.ethiopianairlines.com/EAA https://www.ethiopianairlines.com/EAA [2]: https://www.cae.com/news-events/press-releases/caes-boeing-737max-aircraft-full-flight-simulator-and-flight-training-device-qualified-by-transport-canada/ https://www.cae.com/news-events/press-releases/caes-boeing-7...

ajross 8y ago

Yeah. As much blame as Boeing and the FAA certification process seems to deserve here, it's worth pointing out how much of the cascade of failures is in the airlines and cockpits too. I mean, yes, the trim system was being driven by input from a single nonredundant sensor, which is a violation of the kind of engineering for failure process that airliners should be designed in. But at the same time that trim system is, by design, not strong enough to overpower pilot input to the other control surfaces. I mean, it's supposed to have been possible for the pilot to just fly the aircraft to a landing in the face of outrageous trim problems. But the actual pilots didn't, not because they weren't strong enough to push the yoke but because they simply didn't know what to do and didn't have the presence of mind to just yank hard on the controls. Somehow the culture of "just fly the ?!@#! plane" got lost in all those training iPads.

tafda 8y ago
Not true. https://www.seattletimes.com/business/boeing-aerospace/failed-certification-faa-missed-safety-issues-in-the-737-max-system-implicated-in-the-lion-air-crash/ https://www.seattletimes.com/business/boeing-aerospace/faile... Quote: The discrepancy over this number is magnified by another element in the System Safety Analysis: The limit of the system’s authority to move the tail applies each time MCAS is triggered. And it can be triggered multiple times, as it was on the Lion Air flight. One current FAA safety engineer said that every time the pilots on the Lion Air flight reset the switches on their control columns to pull the nose back up, MCAS would have kicked in again and “allowed new increments of 2.5 degrees.” “So once they pushed a couple of times, they were at full stop,” meaning at the full extent of the tail swivel, he said. Peter Lemme, a former Boeing flight controls engineer who is now an avionics and satellite-communications consultant, said that because MCAS reset each time it was used, “it effectively has unlimited authority.”
- ajross 8y ago
  Yes true.[1] You're misunderstanding that quote. It's talking about "authority" in the sense of software's authorization to move the trim tab, not the aerodynamic authority of the tailplane. The 737 has a 60 year old, very conventional elevator with a trim tab. The tab changes the resting angle of the overall elevator, and thus the "center point" of tailplane force on the airframe. Being out of trim means that the aircraft might naturally want to pitch up or down, and forces the pilot to apply to force to the stick (which moves the elevator, not the trim tab!) to correct it. This stick force can be significant and surprising, but it's designed to (and the certification surely requires it to) be achievable by a pilot under all conditions. That is: it's not supposed to be possible for any trim failure on a 737 to render an aircraft uncontrollable, and I don't see any assertion in the analysis of the MAX 8 that changes that. At the end of the day, what happened here is that the aircraft had a runaway trim failure. That was a failure that was understood and forseen (albeit not under software control) in the aircraft's original design, and the redundancy to treat it was the pilot's physical ability to override the trim. This was supposed to have been a recoverable failure within the cockpit, and it wasn't. [1] Style note: why do people do this on the internet? Ah hah! You fool! You are WRONG! Stuff is complicated folks, be nice, assume competence, assume lack of malice, try to teach and not argue.
  - tzakrajs 8y ago
    Your footnote is really appreciated. I think there is a lot of trauma in this world and coping is a daily struggle for many of us. My hat is off to you.
    - wenc 8y ago
      I don't know -- in discourse, it's perfectly fine to dispute ideas (it's the foundation of Western civilization and of analytical thought, and is a means to knowledge and wisdom). If we cannot argue in a marketplace of ideas, we are prevented from having hard but necessary conversations. We need to adhere to parameters of civility of course, but to me, a necessary freedom is the freedom to disagree/dispute. Some ideas are truly wrong and they need to be put through the crucible. That said, I've always been told to always "address the ideas, not the person" (never attack someone's character) and to adopt a pose of "curiosity".
outworlder 8y ago
> But at the same time that trim system is, by design, not strong enough to overpower pilot input to the other control surfaces. That is incorrect for the 737 and many airliners. Elevator input is way less strong than trim. Trim moves the entire surface, not just the elevator control surface. I had the same misconception, my brain was translating GA aircraft knowledge to airliners.
- DiffEq 8y ago
  The GA Aircraft; Cessna 182B has Stab trim.
  - sokoloff 8y ago
    Most light GA aircraft have a trim system that works by using a smaller trim surface to aerodynamically deflect the larger control surface. In such a system, the horizontal stabilizer has a fixed relationship to the fuselage. Later 182s definitely have this system (I owned a 182K for 16 years). Some light GA aircraft have systems with jackscrews that deflect the horizontal stabilizer as in airliners. These systems are more efficient aerodynamically, but can overpower pilot input, at least in theory. The aero trim system (in prior paragraph) cannot.
lagolinguini 8y ago
> But at the same time that trim system is, by design, not strong enough to overpower pilot input to the other control surfaces. No this is not true. In near stall situations for which the MCAS is designed, a full deflection of the elevators is not enough to counter the stabiliser effects. I'm not sure about the entire flight envelope, but I guarantee there are other situations where the elevator cannot counter the stabiliser. The right way to "regain control" isn't to overpower the stabiliser by inputs to other flight control surfaces, but to disable automatic stabiliser trim and manually trim the aircraft.

rnbrady 8y ago

> It makes no metion of MCAS. 27 - FLIGHT CONTROLS STABILIZER TRIM: Stab Trim cutout switches panel

racingmars 8y ago
Not sure what the meaning of your comment is. The Stab Trim cutout switches have been in the 737, in the same place aft of the flap selector, since the original 737. These were not a new feature related to the MCAS system.
- AnimalMuppet 8y ago
  No, not a new feature. But don't they stop the ability of MCAS to change the trim?
  - racingmars 8y ago
    Yes, the "correct procedure" would be for the pilots to recognize the MCAS problem (whether they know about the existence of MCAS or not) as a runaway stab trim problem, and treat it as such. One of the steps for the runaway stab trim emergency checklist (which I believe is a memory item for 737 pilots) is to set the stab trim switches to cutoff. At that point, they can manually (with the wheels in the cockpit) return the stabilizer to a better trim position, then recover control of the aircraft. I'm not a real-world airliner pilot (I just play with them in simulators), so I can't comment on whether it's reasonable to expect pilots to recognize the situation and react accordingly in this new failure mode. Without knowledge of the existence of the MCAS system and how it can fail, with uncommanded nose-down, it's unclear that pilots would think there were any factors they recognize that would cause a runaway trim situation and think, "oh, I need to run the runaway trim checklist." I think that's the crux of the argument "any 737 pilot should have been competent to save the plane because they should have recognized runaway stab trim" versus "the set of conditions that caused this problem involved systems that pilots weren't trained on, so it's not reasonable for them to recognize what was happening and realize they can fall back on different training that they did have." Anyway... comment I was replying to seemed to imply the existence of the stab trim cutout switches implied that the MCAS system was made known to pilots, which is why I pointed out those switches had been there forever.

vt240 8y ago

The banner of the EAA website says they have a Full 737MAX simulator [1]. From this Press Release [2], it would seem they were rolling out in Oct, 2017. [1]: https://www.ethiopianairlines.com/EAA https://www.ethiopianairlines.com/EAA [2]: https://www.cae.com/news-events/press-releases/caes-boeing-737max-aircraft-full-flight-simulator-and-flight-training-device-qualified-by-transport-canada/ https://www.cae.com/news-events/press-releases/caes-boeing-7...