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Thread: Lion Air 737-Max missing, presumed down in the sea near CGK (Jakarta)

  1. #101
    Senior Member Gabriel's Avatar
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    Quote Originally Posted by Black Ram View Post
    Ok, I see. You are saying the trim would get stuck at full ANU if it got there.
    Not exactly, I am saying that there is a scenario where the autotrim may stealthly trim all the way up (or close to that, doesn't matter) as response of pilot's sidestick or autoflight inputs and then something else happens (maybe it was the plane coming in direct law, I am not sure) that makes the autotrim stealthly disconnect (except for an EICAS message) so pushing nose down would not make the stabilizer move from the (almost) full nose up.

    Again, I don't remember the scenario exactly, but I do remember we discussed it a length in the AF thread before we had the CVR and FDR info, but it was already quite clear from the ACARS and the forensic analysis if the wreckage that the plane had a UAS event and stalled off the sky.

    Some were speculating before the wreckage was found that the crew might have not remembered to move the throttle, causing the stall. But then it became apparent the pilots were using the throttles.
    .

    Yes, when the plane stalled at the top of the impossible climb. Only then they touched the throttles and added full thrust (by the way, all three airspeed indicators were working ok and giving correct and consistent readings since a few seconds by then). They did a 1.5, 7000+ fpm, 2500ft climb from the maximum altitude, without adding thrust. Duh! (but that's for another thread)

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  2. #102
    Senior Member Gabriel's Avatar
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    Quote Originally Posted by ATLcrew View Post
    EVERY? To how many of them have you spoken?
    Isn't runaway trim part of the very basic standard curriculum of what is done in the sim as part of any type rating?

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  3. #103
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    Quote Originally Posted by Gabriel View Post
    Isn't runaway trim part of the very basic standard curriculum of what is done in the sim as part of any type rating?
    Not only that, but I have it on good authority that the malfunction in question is even a memory item on at least one type. Remember, though, "standard basics" are not welcome 'round these parts, only strict, highly type-specific procedures are.

  4. #104
    Senior Member BoeingBobby's Avatar
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  5. #105
    Senior Member Evan's Avatar
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    Quote Originally Posted by ATLcrew View Post
    Not only that, but I have it on good authority that the malfunction in question is even a memory item on at least one type. Remember, though, "standard basics" are not welcome 'round these parts, only strict, highly type-specific procedures are.
    Right, because runaway pitch trim 'standard basics' are so universal... grab the damn pitch trim wheel... on the 737, the 757... oh wait, WHERE'S THE DAMN PITCH TRIM WHEEL?!... or the A320... which... doesn't have a runaway pitch trim problem in the first place... but whatever, we'll just grab the trim wheel and, uh... WHERE ARE THE DAMN CUTTOFF SWITCHES?!

    Better to pay attention in type-specific class, I'm guessing, and practice what you've learned. Cuz when the ground starts coming up and you've got 5...4...3...2...1...

  6. #106
    Senior Member Evan's Avatar
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    The WSJ has published a claim that the 737MAX has new stall protection features that may make it impossible for pilots to overcome an erroneous pitch down command.

    Quote Originally Posted by CNN
    Citing "safety experts involved in the investigation, as well as midlevel FAA officials and airline pilots," the Journal reported Monday that the automated stall-prevention system on Boeing 737 MAX 8 and MAX 9 models -- intended to help cockpit crews avoid mistakenly raising a plane's nose dangerously high -- "under unusual conditions can push it down unexpectedly and so strongly that flight crews can't pull it back up."
    STS has been a feature since the debut of the NG's. It can be overriden (with considerable effort) by the pilots. So what are they talking about here?
    The very idea goes against Boeing's "pilot-has-ultimate-authority" philosophy. If it does turn out that Boeing developed an "airplane-has-ultimate-authority" stall protection system without air data redundancy, the entire 737MAX fleet will have to be immediately grounded and the system redesigned and recertified. That outcome could be curtains for Boeing.
    However, I find it impossible to believe the FAA would certify such a system in the first place, let alone that Boeing would be so foolish as to design one.
    So I'm highly inclined to file this report under "poor fact checking".

    On the other hand, Boeing DID design an autopilot for the NG that would occassionally--due to an undetected weakness in the logic--continue to operate without redundancy when one RA was faulty and this led to the fatal crash of Turkish 1951. That system was quietly replaced in 2003 with a reliable alternative and the press never got wind of it.

  7. #107
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    Quote Originally Posted by Evan View Post
    If it does turn out that Boeing developed an "airplane-has-ultimate-authority" stall protection system without air data redundancy, the entire 737MAX fleet will have to be immediately grounded and the system redesigned and recertified. That outcome could be curtains for Boeing.
    Oh...Evan, it would take a lot more than that to cause "curtains" for Boeing, trust me.

  8. #108
    Senior Member 3WE's Avatar
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    Quote Originally Posted by ATLcrew View Post
    Oh...Evan, it would take a lot more than that to cause "curtains" for Boeing, trust me.
    However, I AM sure it would generate much parlour talk.
    Les règles de l'aviation de base découragent de longues périodes de dur tirer vers le haut.

  9. #109
    Senior Member Evan's Avatar
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    Quote Originally Posted by ATLcrew View Post
    Oh...Evan, it would take a lot more than that to cause "curtains" for Boeing, trust me.
    So, a significant delay of over 4,500 deliveries (and the potential cancellations of those orders) and the thusly expanded time to profitability and loss of public confidence on that airframe wouldn't cause a fatal shareholder panic in the age of shareholder panic. That's reassuring.

  10. #110
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    Quote Originally Posted by Evan View Post
    So, a significant delay of over 4,500 deliveries (and the potential cancellations of those orders) and the thusly expanded time to profitability and loss of public confidence on that airframe wouldn't cause a fatal shareholder panic in the age of shareholder panic. That's reassuring.
    Remind me how long the Nightmareliner sat on the ground over a battery.

  11. #111
    Senior Member Evan's Avatar
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    Quote Originally Posted by ATLcrew View Post
    Remind me how long the Nightmareliner sat on the ground over a battery.
    About four months, at which point they had around 900 orders to delay. As opposed to 4,500. Perhaps Boeing could simply modify the 737 system to integrate AoA redundancy (and disengage if redundancy is lost) and get it re-certified in a similar timeframe. Or perhaps they could use their political muscle to keep the fleet flying in the meantime and only issue a recommendation for the upgrade, as they did with that treacherous autothrust unit. I think, if this turns out that the crew really had no reasonable chance of restoring flight control, the FAA would ground it until it could be re-certified as safe. That would do some real injury to a brand that absolutely depends on public trust.

  12. #112
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    Every cockpit needs one of these to disable HAL.

    Click image for larger version. 

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  13. #113
    Senior Member Gabriel's Avatar
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    Quote Originally Posted by Evan View Post
    The WSJ has published a claim that the 737MAX has new stall protection features that may make it impossible for pilots to overcome an erroneous pitch down command.
    I don't believe that. The pilot can always overpower the trim wheel.

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  14. #114
    Senior Member Evan's Avatar
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    Quote Originally Posted by Gabriel View Post
    I don't believe that. The pilot can always overpower the trim wheel.
    I think the WSJ is just misinformed. I hope it is.

    However, now the NY times is reporting on this...

    Quote Originally Posted by NY Times
    “We’ve just been informed that there’s an entire new system on the Max,” said Capt. Dennis Tajer, spokesman for the Allied Pilots Association, the union for pilots at American Airlines, and a 737 pilot.

    He said he was referring to what is known on the new version of the plane as the M.C.A.S., or maneuver characteristics augmentation system. The previous system, and the one in the standard manual, goes by a different shorthand, E.F.S., for elevator feel shift.
    Quote Originally Posted by NY Times
    The pilots’ union for American Airlines, which also flies the Max 8, said Tuesday that the emergency system in question had not been included by Boeing in the standard operating manual. In addition, the flight checklist — which contains information for manually overriding the emergency system — was incorrect, the union said.
    If this is a stall-protection system that introduces automated flight control inputs based on a single source of AoA data... this is looking very very bad for Boeing....

  15. #115
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    From PPRUNE.ORG

    From the extremely brief description of the MCAS, we can possibly conclude:

    JT 610 retracted flaps to the clean configuration (MCAS becomes active)

    Low mach number, therefore maximum rate of horizontal stabilizer of 0.27 degrees per second, and a forward deflection to the limit with a spurious AoA input.


    And LOTS of talk of none of this being in the 'manual'

    This is looking like a whole lotta lawsuit for Boeing

  16. #116
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    There has been a lot of talk about this. Some have suggested Boeing needed the new system on the MAX to make it behave the same way as the NG, despite the heavier engines and altered center of gravity. This was needed for certification. But now they are saying Boeing did not clearly describe the changed behavior from the new system - possibly to keep commonality with the NG and avoid any additional training that would have been required? It is speculation, but that's one reason forums exist.

  17. #117
    Senior Member TeeVee's Avatar
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    if this turns out to be true, forget about lawsuits. people should be charged criminally. fat chance of that happening though.

  18. #118
    Senior Member Evan's Avatar
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    Quote Originally Posted by Black Ram View Post
    There has been a lot of talk about this. Some have suggested Boeing needed the new system on the MAX to make it behave the same way as the NG, despite the heavier engines and altered center of gravity. This was needed for certification.
    This comes down to Boeing's decision to postpone the Y1 project, a clean-sheet replacement to the 737-757. The 737 was designed for turbojets and regional airports without jetways or large airstairs. Its achilles heel is its limited undercarriage: it sits too low to the ground to accommodate the kind of high-bypass turbofans that the modern age requires. Nevertheless, Boeing chose to crutch the 737 into the 21st-century by mounting the larger engines forward of the wing. This allowed them to squeeze in bigger fans, but at the cost of moving the center of thrust forward, where it would have a more pronounced pitch-coupling effect.

    The NG's therefore required the STS system to be certified. That worked out. There have been no upset incidents that I know of involving that system.

    But the MAX required even bigger fans, and, once again, Boeing responded by pushing the engines out further ahead of the wing. The MCAS system is apparently the STS replacement needed to certify the MAX. The concerns regarding the 737's pitch coupling potential only increased and perhaps something more extreme was required to give it the same flying characteristics.

    All this because the airframe, designed in the mid-1960's, wasn't suitable for modern turbofans.

    The other issue, which I think we will be hearing a lot more about, is how Boeing marketed the 737MAX on the merits of cockpit commonality with customers' existing 737NG fleets. This represented a large cost-saving advantage over the A320 to operators not already flying that type. Boeing was telling potential customers that the 737MAX would require only 16 hours of type-specific transitional training. Clearly, this training did not address the new pitch augmentation system.

    If all this proves true, then I think the fix will lie in adding at least one layer of redundancy to the MCAS system and more type-specific training, both on reacting to a malfunction and in flying the 737MAX more cautiously with the system inoperative. Because, without a properly-functioning MCAS, the 737MAX is apparently considered too unsafe to certify...

    Note: MCAS is even not listed in the 737MAX MMEL found online. There is a listing for "speed trim function", which indicates that two units are present and dispatch requires one to be confirmed operational, provided the faulty one is disconnected.

  19. #119
    Senior Member Gabriel's Avatar
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    Quote Originally Posted by Evan View Post
    This comes down to Boeing's decision to postpone the Y1 project, a clean-sheet replacement to the 737-757. The 737 was designed for turbojets and regional airports without jetways or large airstairs. Its achilles heel is its limited undercarriage: it sits too low to the ground to accommodate the kind of high-bypass turbofans that the modern age requires. Nevertheless, Boeing chose to crutch the 737 into the 21st-century by mounting the larger engines forward of the wing. This allowed them to squeeze in bigger fans, but at the cost of moving the center of thrust forward, where it would have a more pronounced pitch-coupling effect.

    The NG's therefore required the STS system to be certified. That worked out. There have been no upset incidents that I know of involving that system.

    But the MAX required even bigger fans, and, once again, Boeing responded by pushing the engines out further ahead of the wing. The MCAS system is apparently the STS replacement needed to certify the MAX. The concerns regarding the 737's pitch coupling potential only increased and perhaps something more extreme was required to give it the same flying characteristics.
    Can you please provide more explanation of what phenomena you have in mind in reference to the parts I highlighted in bold font?

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  20. #120
    Senior Member Evan's Avatar
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    Quote Originally Posted by Gabriel View Post
    Can you please provide more explanation of what phenomena you have in mind in reference to the parts I highlighted in bold font?
    The STS system was needed to certify the 737NG, due to more pronounced pitch characteristics in certain situations, such as with high thrust, light gross weight and aft CoG. As I understand it, this was attributed to the relocation of the engine mounts to a position more forward of the wing, and perhaps the increased thrust of the new engines. The new power/geometry would have more pronounced pitch-up effects in these situations. As I understand it, the MAX required Boeing to further compensate for this issue with a replacement for the STS that, as I understand it, has more pronounced behaviors.

    So now tell us about the physics...

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