3 ms·

Lion Air 737 MAX crew had seconds to react, Boeing simulation finds

3 points by okket 8y ago

cjbprime 8y ago
I don't understand the 40 seconds idea at all. It seems like you can maintain control of the aircraft indefinitely as long as you use the trim switches on the control column to counter the MCAS movement while you diagnose the issue and eventually disable the trim motor. A claim that they had only 40 seconds to react can't also be true. It's one or the other.
cmurf 8y ago
This article cites its source as: https://www.nytimes.com/2019/03/25/business/boeing-simulation-error.html https://www.nytimes.com/2019/03/25/business/boeing-simulatio... Many questions are still unanswered including the catch all "does this particular variety of MCAS upset look like runaway trim to some pilots, most pilots, or all pilots?" The 40 seconds part is something of a theoretical construction that just means if you're surprised enough that you only try to fight the plane with yoke elevator control alone (unlikely in my pilot, but not 737 pilot, estimation), you've got merely 40 seconds and that very well could induce panic. Central to reacting to an emergency is stabilizing the plane enough to buy time, hopefully indefinitely, but even if you've bought 5 minutes that's OK to move on to rational troubleshooting including preparing for an emergency landing. If you don't ever get it stabilized, panic might set in. Even a stable approach to an ocean ditching is better than an uncommanded nose dive, because you know one could end well and the other won't.
- cjbprime 8y ago
  > The 40 seconds part is something of a theoretical construction that just means if you're surprised enough that you only try to fight the plane with yoke elevator control alone (unlikely in my pilot, but not 737 pilot, estimation), you've got merely 40 seconds and that very well could induce panic. So it's like "you only have 4 seconds to turn your car before it leaves the road, if you don't use the steering wheel"? The trim control is right there on the control column, it's a fundamental control! Positing that the plane will descend and the yoke will get progressively heavier without the pilot attempting trim control is ridiculous.
  - cmurf 8y ago
    It's an example of the magnitude of the defect and the urgency it cause. It is not advocating a course of action. The source article directly points out that using trim toggle would extend the time beyond 40 seconds. Steering wheel is not analogous to a trim toggle, but rather the yoke. There's no appropriate analog for trim on a car.

3 points by okket 8y ago

I don't understand the 40 seconds idea at all. It seems like you can maintain control of the aircraft indefinitely as long as you use the trim switches on the control column to counter the MCAS movement while you diagnose the issue and eventually disable the trim motor. A claim that they had only 40 seconds to react can't also be true. It's one or the other.

cmurf 8y ago

This article cites its source as: https://www.nytimes.com/2019/03/25/business/boeing-simulation-error.html https://www.nytimes.com/2019/03/25/business/boeing-simulatio... Many questions are still unanswered including the catch all "does this particular variety of MCAS upset look like runaway trim to some pilots, most pilots, or all pilots?" The 40 seconds part is something of a theoretical construction that just means if you're surprised enough that you only try to fight the plane with yoke elevator control alone (unlikely in my pilot, but not 737 pilot, estimation), you've got merely 40 seconds and that very well could induce panic. Central to reacting to an emergency is stabilizing the plane enough to buy time, hopefully indefinitely, but even if you've bought 5 minutes that's OK to move on to rational troubleshooting including preparing for an emergency landing. If you don't ever get it stabilized, panic might set in. Even a stable approach to an ocean ditching is better than an uncommanded nose dive, because you know one could end well and the other won't.

cjbprime 8y ago
> The 40 seconds part is something of a theoretical construction that just means if you're surprised enough that you only try to fight the plane with yoke elevator control alone (unlikely in my pilot, but not 737 pilot, estimation), you've got merely 40 seconds and that very well could induce panic. So it's like "you only have 4 seconds to turn your car before it leaves the road, if you don't use the steering wheel"? The trim control is right there on the control column, it's a fundamental control! Positing that the plane will descend and the yoke will get progressively heavier without the pilot attempting trim control is ridiculous.
- cmurf 8y ago
  It's an example of the magnitude of the defect and the urgency it cause. It is not advocating a course of action. The source article directly points out that using trim toggle would extend the time beyond 40 seconds. Steering wheel is not analogous to a trim toggle, but rather the yoke. There's no appropriate analog for trim on a car.