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    I always thought that effectively all modern aircraft were double redundancy nowadays?
    Mostly in hardware but also hydraulic systems (and engines )

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    Quote Originally Posted by adama View Post
    Yes you can move the stick just as much, but my understanding was at the full trim stick fully back was not enough to then take the plane back to level flight based on the previous accident report?
    The trim setting does not affect the control column travel, and there was plenty of control surface movement available to return to level flight. The problem was the elevator was pitching down- there was lots of upward travel available to the control surface.

    The pilots were apparently fighting the MCAS when the crash occurred. The previous flight had the same problem, and the pilots disabled the MCAS and completed the flight without incident.

    Crashed Lion Air 737 Max 8 had repeated speed, altitude issues

    Here is the Boeing bulletin, note they identify the cause as the AOA sensors, not MCAS.

    Boeing issues 737 Max fleet bulletin on AoA warning after Lion Air crash - The Air Current

    The MCAS aggravates the situation, but there will still be downward pressure on the control column with or without MCAS. MCAS was not the cause- it was the bad AOA sensor. If the AOA sensor had not failed, the MCAS would not have behaved the way it did.

    When the pilots get a MISMATCH on the IAS or AOA, they have to apply their training to determine which side is giving the erroneous reading. The Lion Air crash was completely preventable- the airline was operating a jet that was not airworthy because a critical backup system (the left side AOA sensor) was faulty.

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    Quote Originally Posted by jancollc View Post
    Negative. The flight control system on all 737NG and MAX is the same. There are over 7000 737's flying with this flight control system.

    The MAX is a re-engined 737NG with some minor modifications to the wings and airframe.
    no, that is not what I've read, exactly the opposite, they most assuredly did change the system on the max and didn't tell the pilots. I think you can't manually override with the stick, you have to switch it off.

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    and to switch it off, you have to put in a certain mode, thats the fatal flaw, yes if the pilot has the proper training, and responds to the situation optimally yes, its easy. but to have the cutout switch work sometimes and not others depending on operating mode violates every tenant of good design for a critical safety feature. and on top of that, don't train for it, don't even tell the pilots.

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    Quote Originally Posted by cyanidekid View Post
    and to switch it off, you have to put in a certain mode, thats the fatal flaw, yes if the pilot has the proper training, and responds to the situation optimally yes, its easy. but to have the cutout switch work sometimes and not others depending on operating mode violates every tenant of good design for a critical safety feature. and on top of that, don't train for it, don't even tell the pilots.
    If this is the case, it sounds like the Scarebus AF447...

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    Quote Originally Posted by cyanidekid View Post
    and to switch it off, you have to put in a certain mode, thats the fatal flaw,
    This is the second time you have said that- post your source. All I've seen from you so far is uneducated speculation.

    To the pilot it's just a pair of on-off switches, he can use it or not use it- entirely at his discretion. The Lion Air flight right before the crash had the AOA MISMATCH and the pilot just turned off the MCAS. Simple as that.

    The Boeing bulletin says nothing about being in a certain "mode". I don't even know what "mode" you might be referring to. Airplanes have systems, some of them are necessary to make the plane fly, and some are not. Autopilots, autothrottles, autolanding are not typically referred to as "modes" in the aviation community.

    The MCAS is a trim augmentation system used in manual flight only. If you are on autopilot it's not even active. So I don't know what "mode" you could possibly be referring to. The plane was being manually flown.

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    Ok, against my better judgement, I'm going to try to correct some inaccuracies posted here and maybe offer a little bit of perspective.

    First, the 737 is a very stable aircraft with a large flight envelope. It is easy to hand fly. The only time the envelope is small is if you are near the top of it's altitude envelope (based on weight and outside air temp), and that's true of any aircraft.

    No 737 is entirely fly-by-wire. The primary flight controls are hydraulically actuated. There are cables running from the control column to the main wheel well. From there, it's hydraulic. Each primary control surface (aileron, elevator, and rudder) has two actuator on independent hydraulic systems with a third manual (hydraulic for the rudder) backup if they both fail. Starting with the NG models in late 1997, the throttles became fly-by wire. Previously there were cables all the way to the fuel control unit. Now, it's just a potentiometer under each thrust lever and the computer runs the engine. There was one failure of this system (that I know of) that was early on and blamed on faulty firmware. It was fixed. Starting with the MAX, the spoiler system became fly-by-wire (for weight savings, I believe). Spoilers are used for roll control augmentation, extra drag when needed in flight, and on landing to kill wing lift for better braking.

    In addition to elevator control for pitch, the leading edge of the horizontal stabilizer can be moved up and down to trim off elevator control force. There are two motors running a jack screw. One for the autopilot and one controlled by switches on the pilot's control yokes. You can also grab a big wheel on either side of the throttle stand and do it manually. Whenever either motor trims the stab, the big wheel moves. There are stab trim cutout which remove electrical power from the motors.

    MCAS was added to the MAX aircraft. It uses the captain's angle of attack (AOA) vane to determine that a stall (wing reaching critical angle of attack) is imminent and it then runs the stab trim towards nose down for up to 10 seconds. For the record, that's a lot of nose down trim. MCAS only operates with the flaps up and the autopilot off. If the pilot activates the yoke trim switches (which he would naturally do if he were fighting to pull back on the control column), MCAS stops. Once the pilot stops trimming, MCAS can restart if it still detects high AOA. If you turn off stab trim cutout switches, MCAS can no longer function.

    Theoretically, a malfunctioning AOA vane causing a faulty MCAS event is easily recoverable. Obviously, in practice it may not be so easy. You have a hand full of out-of-trim aircraft with possible multiple other loud and confusing aural warnings and the stall warning (stick shaker) going off. Having knowledge of the Lion Air failure makes it much easier for a crew to correctly diagnose and respond to this failure.


    We don't know the cause of the latest accident yet, so let's hold off on the blame game until we do.

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    ^^^ exactly, and thank you for posting some rational commentary.

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    Coming from a guided weapons background that control system, and by extension, all the other highly automated-fly-by-computer are lethal by design given certain sensor errors.

    Bottom line is that the control system is required to fly the designated flight profile. If aircraft issues mean it can't fly the profile it should deviate as gracefully as possible into, at best, a rough landing, at worst a survivable crash. With or without pilot assistance.

    Simplest way to achieve this is with an independent supervisory monitor with its own sensors able to "see" if the computerised control inputs and sensor readings make sense in terms of what the aircraft is actually doing and what its supposed to be doing. Basically what the pilot used to do before things got too complicated. Basic pitch, yaw, tilt and speed sensors along with independent height radar should suffice. Heck wouldn't be surprised if you couldn't get most of the data via GPS. Given the size of a modern airliner 4 receivers, one on each wingtip and at front and back might well give sufficiently precise orientation information. Speed and height you already have.

    Computer controlled flight into the ground means the system designers have cocked up. Big time. It has to be made impossible by design before you start adding the twiddly bits.

    Not a new idea and not necessarily overcomplicated to install if my experience with guide weapons technology demonstrators is anything to go by. That said nothing I worked on ever flew completely autonomously as we were primarily working on target detection and tracking.

    Huge difference between something that actually flies the aircraft and something that just says "Hang on, thats not right." to initiate a failed sensor / failed actuator work around mode.

    Clive

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    Quote Originally Posted by Finegrain View Post
    MCAS is not autopilot. In fact based on the article I linked, MCAS is only enabled when autopilot is off. MCAS is intended to compensate for the MAX version of the 737's tendency to pitch up.
    Mike
    Well it sure as fucking hell does that job. Of course they could just put a timer on the stabilizer trim and force it into full down after ten minutes of flight.
    Accomplishes the same kill rate.

    "Here is the Boeing bulletin, note they identify the cause as the AOA sensors, not MCAS."

    I may be missing something here, but if the MCAS system relies on the angle of attack sensors, then those sensors are
    in a broad sense actually *part* of the MCAS system. Oh, maybe not in a technical, aviation sense, but one would
    think the engineers would think "what happens if the MCAS is getting erronious information from its sensors?"

    Which apparently causes the aircraft to develop a sudden attraction to the ground. Honestly this sounds as bad
    as trying to fly if all the pitot tubes are blocked.

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    Quote Originally Posted by jerholz View Post
    Ok, against my better judgement, I'm going to try to correct some inaccuracies posted here and maybe offer a little bit of perspective.

    First, the 737 is a very stable aircraft with a large flight envelope. It is easy to hand fly. The only time the envelope is small is if you are near the top of it's altitude envelope (based on weight and outside air temp), and that's true of any aircraft.

    No 737 is entirely fly-by-wire. The primary flight controls are hydraulically actuated. There are cables running from the control column to the main wheel well. From there, it's hydraulic. Each primary control surface (aileron, elevator, and rudder) has two actuator on independent hydraulic systems with a third manual (hydraulic for the rudder) backup if they both fail. Starting with the NG models in late 1997, the throttles became fly-by wire. Previously there were cables all the way to the fuel control unit. Now, it's just a potentiometer under each thrust lever and the computer runs the engine. There was one failure of this system (that I know of) that was early on and blamed on faulty firmware. It was fixed. Starting with the MAX, the spoiler system became fly-by-wire (for weight savings, I believe). Spoilers are used for roll control augmentation, extra drag when needed in flight, and on landing to kill wing lift for better braking.

    In addition to elevator control for pitch, the leading edge of the horizontal stabilizer can be moved up and down to trim off elevator control force. There are two motors running a jack screw. One for the autopilot and one controlled by switches on the pilot's control yokes. You can also grab a big wheel on either side of the throttle stand and do it manually. Whenever either motor trims the stab, the big wheel moves. There are stab trim cutout which remove electrical power from the motors.

    MCAS was added to the MAX aircraft. It uses the captain's angle of attack (AOA) vane to determine that a stall (wing reaching critical angle of attack) is imminent and it then runs the stab trim towards nose down for up to 10 seconds. For the record, that's a lot of nose down trim. MCAS only operates with the flaps up and the autopilot off. If the pilot activates the yoke trim switches (which he would naturally do if he were fighting to pull back on the control column), MCAS stops. Once the pilot stops trimming, MCAS can restart if it still detects high AOA. If you turn off stab trim cutout switches, MCAS can no longer function.

    Theoretically, a malfunctioning AOA vane causing a faulty MCAS event is easily recoverable. Obviously, in practice it may not be so easy. You have a hand full of out-of-trim aircraft with possible multiple other loud and confusing aural warnings and the stall warning (stick shaker) going off. Having knowledge of the Lion Air failure makes it much easier for a crew to correctly diagnose and respond to this failure.


    We don't know the cause of the latest accident yet, so let's hold off on the blame game until we do.
    Thanks for the clarification.
    It’s easy to forget how old the 737 design is.

    To clarify.
    The 737 flies with out software loops in the primary control surfaces at all?

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    Quote Originally Posted by jim rozen View Post
    Well it sure as fucking hell does that job. Of course they could just put a timer on the stabilizer trim and force it into full down after ten minutes of flight.
    Accomplishes the same kill rate.

    "Here is the Boeing bulletin, note they identify the cause as the AOA sensors, not MCAS."

    I may be missing something here, but if the MCAS system relies on the angle of attack sensors, then those sensors are
    in a broad sense actually *part* of the MCAS system. Oh, maybe not in a technical, aviation sense, but one would
    think the engineers would think "what happens if the MCAS is getting erronious information from its sensors?"

    Which apparently causes the aircraft to develop a sudden attraction to the ground. Honestly this sounds as bad
    as trying to fly if all the pitot tubes are blocked.
    That’s what took out the Air France flight a few years back.
    The Pitot tubes likely iced, which the autopilot recognized.
    It kicked off, the crew then miss handled the transition.

    An unplanned return to manual flight sounds pretty traumatic.

    Also, the software changed states, which changed the way the aircraft responded to pilot input.

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    Quote Originally Posted by Miguels244 View Post
    Thanks for the clarification.
    It’s easy to forget how old the 737 design is.

    To clarify.
    The 737 flies with out software loops in the primary control surfaces at all?
    Correct.

    Sent from my SAMSUNG-SM-G930A using Tapatalk

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    Quote Originally Posted by Miguels244 View Post
    That’s what took out the Air France flight a few years back.
    The Pitot tubes likely iced, which the autopilot recognized.
    It kicked off, the crew then miss handled the transition.

    An unplanned return to manual flight sounds pretty traumatic.

    Also, the software changed states, which changed the way the aircraft responded to pilot input.
    What happened with AF447, was the pilot and co-pilot had the same make/model pitot tubes.
    They iced up and IAS said too slow. So co-pilot was pulling up on the stick so nose was high and inducing stall.
    Pilot thought he took control of the plane - they switched from copilot to pilot and the little light lit to say he had control, but the plane kept falling.
    There was a "feature" with the airbus that although the switch and light said the pilot had control, because the co-pilot still had his hand on the stick and the stick was still fully back, this rendered the handover inactive because the stick had to be in the neutral position for the handover to take place.
    They fell lower and lower and the Captain came back to the cockpit too late - he had been sleeping in the rear and realised what had happened and it was then too late.
    Too many flashing lights, too many alarms screaming, and dark.
    The crash was at night. Always best to not fly at night - pilot disorientation...

    By memory, there were previously (I'm thinking 8 if memory serves) issues of this exact same thing happening, but luckily no crashes.
    But a lot of bullets dodged...

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    I have been watching the news and reading. It is somewhat in a scramble now for things to settle down for a thorough eval.

    There is the issue also floated that not all countries demand pilots have a minimum amount of flight hours to fly a passenger jet. In the latest crash the flight hours may be found to be low. It becomes a scary thing the experience levels expected in say here in the USA vs another country.

    We are wrong to believe pilots have equal experience and training at the appropriate level needed and/or required.

    I always think once the black boxes are found it is then we must wait to find out anything.

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    There is too much we do not know right now I think it best to take a rest on this topic until we learn some more.

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    Quote Originally Posted by barbter View Post
    What happened with AF447, was the pilot and co-pilot had the same make/model pitot tubes.
    They iced up and IAS said too slow. So co-pilot was pulling up on the stick so nose was high and inducing stall.
    Pilot thought he took control of the plane - they switched from copilot to pilot and the little light lit to say he had control, but the plane kept falling.
    There was a "feature" with the airbus that although the switch and light said the pilot had control, because the co-pilot still had his hand on the stick and the stick was still fully back, this rendered the handover inactive because the stick had to be in the neutral position for the handover to take place.
    They fell lower and lower and the Captain came back to the cockpit too late - he had been sleeping in the rear and realised what had happened and it was then too late.
    Too many flashing lights, too many alarms screaming, and dark.
    The crash was at night. Always best to not fly at night - pilot disorientation...

    By memory, there were previously (I'm thinking 8 if memory serves) issues of this exact same thing happening, but luckily no crashes.
    But a lot of bullets dodged...
    Back to HMI design.
    Something as simple as having the sticks mechanically tied together, as with conventional control yokes.

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    Quote Originally Posted by jancollc View Post
    This is the second time you have said that- post your source. All I've seen from you so far is uneducated speculation.
    as found on the website "The Air Current"
    (it wouldn't let me copy and paste "protected content");

    "flight crew operations manual bulletin for the Boeing company #TCB-19 Nov 6 2018

    ...nose down stabilizer trim movement can be stopped and reversed with the use of the stabilizer trim switches but may restart 5 seconds after the electric stabilizer trim switches are released. repetitive cycles of uncommanded nose down stabilizer continue to occur unless the stabilizer trim system is deactivated through use of both STAB TRIM CUTOUT switches in accordance with the existing procedures in the runaway stabilizer NNC. in the event of an uncommanded nose down stabilizer trim is experienced on the 737-8/9, in conjunction with one or more of the above indications or affects, do the Runaway Stabilizer NNC insuring that the STAB TRIM CUTOUT switches are set to cutout and stay in the cutout position for the remainder of the flight"

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    How long can we expect to wait for a report?

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    Since the NTSB is in charge of the official report, it may be a year or more before it is issued. I spent my career flying every thing from tube and fabric two-seaters to the latest computer-aided designs by Boeing and Airbus. Regardless of any contributing factors in this accident, any properly trained pilot would have re-configured the systems, and recovered the aircraft safely. Third World aviation is a far cry from what we in the U.S expect and get. Training is sometimes glossed over, or skipped, for a variety of reasons. A state-of-the-art, computer-aided aircraft demands that the crew is knowledgeable and competent in the emergency operation of the systems. Failing that, the result is what we see in Somalia. Regards, Clark


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