Originally posted by Gabriel
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Lion Air 737-Max missing, presumed down in the sea near CGK (Jakarta)
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Originally posted by Chris K View PostAt this point there seems general agreement that the pilots screwed the pooch but I go back to my original point/post which is that a test flight should have been conducted given the circumstances. I've read on av-herald both a mechanic and pilot saying the plane should have been rejected to being returned to service given the circumstances. (For me, "test flight" and "rejected to return to service" are synonymous.)
It seems to me, as a lowly passenger, we're being asked to be guinea pigs with insufficient knowledge of the circumstances, at the mercy purely of the pilots skills, thereby eliminating a ginormous mountain of potentially mitigating safeguards. As I said before, if you give me Sulley or Boeing Bobby or Neil freaking Armstrong, I'll buckle up and take my chances, and same for a nearly brand new properly functioning plane with pilot(s) I assume are competent. But a "who knows?" pilot with an aircraft coming off a serious maintenance event? Very few people would sign up for that and rightfully so.
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In the older [737] versions, pilots could help address the problem of the nose being forced down improperly — a situation known as “runaway stabilizer trim” — by pulling back on the control column in front of them, the pilots say.
In the latest 737 generation, called the Max, that measure does not work, they said, citing information they have received since the crash.
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At this point there seems general agreement that the pilots screwed the pooch but I go back to my original point/post which is that a test flight should have been conducted given the circumstances. I've read on av-herald both a mechanic and pilot saying the plane should have been rejected to being returned to service given the circumstances. (For me, "test flight" and "rejected to return to service" are synonymous.)
It seems to me, as a lowly passenger, we're being asked to be guinea pigs with insufficient knowledge of the circumstances, at the mercy purely of the pilots skills, thereby eliminating a ginormous mountain of potentially mitigating safeguards. As I said before, if you give me Sulley or Boeing Bobby or Neil freaking Armstrong, I'll buckle up and take my chances, and same for a nearly brand new properly functioning plane with pilot(s) I assume are competent. But a "who knows?" pilot with an aircraft coming off a serious maintenance event? Very few people would sign up for that and rightfully so.
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Front page story on the New York Times today. It includes this revelation:
Originally posted by NY TimesIn the older [737] versions, pilots could help address the problem of the nose being forced down improperly — a situation known as “runaway stabilizer trim” — by pulling back on the control column in front of them, the pilots say.
In the latest 737 generation, called the Max, that measure does not work, they said, citing information they have received since the crash.Originally posted by Gabriel View PostWhy on Earth would the pilots do that? Why would they stop adding enough nose-up trim?
Originally posted by NY TimesThe pilot had handed control of the plane to the co-pilot just before the plane went into its final dive.
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Originally posted by Gabriel View PostYou mean these pilots never encountered nose-down tendency that required nose-up trim to avoid keep pulling back on the yoke? Actually they did, the last 12 minutes or so before the loss of control.
Well, a more sound MCAS logic on disagreeing AoA (or a 3rd AoA vane, or a third AoA calculated based on other flight parameters like speed, weight and Gs) would have been helpful too. And more in line with "avoid putting pilots in these kinds of situations".
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Originally posted by Evan View PostOk, let's run with that analogy, but fix it. Say that in the office where you work one day they build a new wall in a place you've never walked through before. It wouldn't make any difference. You'd just be lost anyway.
How often do NG pilots get a runaway trim encounter that requires them to cut off the stab trim to regain control? I'm guessing these pilots had never encountered that.
I'm also guessing they had never encountered training for that.
The key to avoiding these kinds of accidents is to avoid putting pilots in these kinds of situations. Nothing else is going to reliably work.
Solid training on runaway trim procedure would have avoided this situation.
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Originally posted by Evan View PostThe key to avoiding these kinds of accidents is to avoid putting pilots in these kinds of situations.
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Originally posted by Gabriel View PostOnce again, I disagree. Or more precisely, I agree with what you say but it is not enough to explain what happened.
Say that in the office where you work one day they build a new wall in a place you usually walked through. Would you just walk into the wall that is there in plain sight, and that you do see it, and then blame that there was no memo informing of the new wall and that you were not properly trained in wall avoidance?
How often do NG pilots get a runaway trim encounter that requires them to cut off the stab trim to regain control? I'm guessing these pilots had never encountered that. I'm also guessing they had never encountered training for that.
...and when the nose did go down and pulling up didn't fix it they thought that they were still in a stall and decided to not to make more nose-up trim inputs (but then why they kept pulling up as hard as they could?)
The key to avoiding these kinds of accidents is to avoid putting pilots in these kinds of situations. Nothing else is going to reliably work.
Solid training on runaway trim procedure would have avoided this situation.
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Originally posted by Gabriel View PostThis is going to be a cornerstone in the aviation industry. Plane makers consistently not disclose (which is not the same as hide) details of how the plane works.
If Boeing is severely hit because of this incident, and in particular if there is a criminal prosecution, the they would go lawyer mode and put in the manuals EVERY detail of the plane and systems design, down to flowcharts and line codes. It will be so much information that it will be impossible for pilots to learn and retain everything. And then the plane makers will just blame the pilot (because we clearly stated in the manuals that if sensor B-47 in the computer RJT62 gave a false signal combined with the flight-sub-mode being on alternate 34 then there wold be an input of 2.45mV in the left side of the green control system that would make trim add incremental nose-down inputs and the recovery procedure for that is to move the trim cutout switches to cutout", instead of just saying "in case of trim runway (which by the way can happen in a number of different scenarios and for a number of different reasons), move the trim cutout switches to cutout. Which one do you think is safer?
As automation increases, systems become intrinsically more complex and interface with the human is supposed to become simpler. It is that interface, and not the deep levels of details, which needs to be very clear.
The procedure for trim runaway was there in the plane's operation and training manuals, and also in the QRH, and it is a memory item. And as I explained, they also had alternate reasonable, intuitive ways not to crash following just common pilot practices that apply to a Piper Cub too. According to Boeing (we still need to see how true this is), the existence and general explanation of this new system was also in the plane's manual, although apparently there was no great details nor specific procedures for its operation (which were not needed, since the general "trim runaway procedure for any reason" would apply.
Come on now. Just setting flaps to 5 again (or even better, keeping them there the whole time) would have avoided this. Only if they knew!
Also, some pilots (admittedly on internet forums) disagree this is just a normal case of trim runaway, mostly because of the intermittent nature of MCAS inputs.
Maybe maintenance did mess up (though we don't know for now), and the plane should not have been flying to begin with, but this could have happened randomly on any other such airplane.
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