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Ethiopian 737-8 Max UPDATE

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Ethiopian 737-8 Max UPDATE
Fri Mar 15, 2019 4:34 pm

Re: Ethiopian 737-8 Max UPDATE
Sat Mar 16, 2019 9:08 am
  • Going computerized is such a double-edged sword. Cockpit systems are built on redundancy and there's a very good reason there are still analog systems in cockpits to this day. My understanding is that pilots didn't even know about this new anti-stall system in their cockpits let alone have proper training in it. That blows my mind. While many computerized systems are intuitive and help tremendously, they have a dark side (if they malfunction) which can create horrific outcomes as we've seen in the news recently.

    There was another major airliner that crashed in the sea killing hundreds and it was discovered if I recall correctly that the anti-stall system was telling the pilots (in zero visibility/IFR) the nose was pitched down and to pull up, so they kept pitching up and didn't realize the computer was incorrect so they were themselves creating an excessive and critical Angle of Attack causing them to stall and literally drop out of the sky until they plunged violently into the Sea klilling everybody on board.

    I am not sure what the solution is quite frankly, as the pilot in the video stated even if you can counter with traditional methods (like the trim wheel and electrical shut off to the stall system) if the problem isn't discovered in time then the physical forces become too great to even matter.

    I watch the show Aviation Disasters not for the crashes but how the NTSB (and the international counterparts) methodically and religiously reverse-engineer every crash to discover the problem and fix it so it doesn't happen again. Their forensic detective work is second-to-none and we should all be profoundly grateful for their commitment to safety.

    Thanks for the video, very interesting. I look forward to this too being properly resolved so there are no more tragedies related to this issue.
    Aros
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Re: Ethiopian 737-8 Max UPDATE
Sat Mar 16, 2019 10:04 am
  • My opinions below are fairly speculative and may show ignorance:

    1. Boeing was going for a new clean sheet design, it was a fact.
    2. Boeing instead went with a modified 737, which became the 737 Max, it was a fact.
    3. 737 Max was further stretched to accommodate more passengers, thus the max 8, 9, 10,
    4. All the stretch and bigger (heavier) engine affect the balance and dynamic of the 737 Maxs
    5. To compensate for the imbalance, and to leverage fly wire, a digital solution was used.
    6. All 737 Max series of planes were not certified by FAA, instead of used 737's original certification cir 1967. this's a fact.

    Boeing might have saved a few pennies, OK billions, in not going for a clean sheet design. Instead Boeing knowingly selling a plane that might have imbalance in it's design, which will in turn cause Boeing more in the long term.

    They always come back to roost.
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Re: Ethiopian 737-8 Max UPDATE
Sat Mar 16, 2019 11:26 am
  • I worked several years on Tanker (a modified 767 for the USAF), a few disagreements with toffee. I have 0 experience with anything outside Tanker, and no experience in Avionics, Flight Controls, or airplane level design. So I'm out of my depth in general.

    Several variants of the 737 MAX are shorter than several variants of the 737 NG - including the two MAX airplanes that crashed. The MAX 8 that crashed are a full inch longer than the 737-800 NGs (I was actually surprised by this, I think the one inch is something with the tail-cone but I didn't want to get that far into the weeds).

    Given that much bigger airplanes use flight cables, I think fly-by-wire is used for reasons other than weight. But that's really out of my understanding.

    Point 6 is just flat out wrong - I know this because I helped on a couple certification projects on Tanker with the FAA. Any new part gets certified, then there is airplane level testing for certification, and sometimes old parts have to get certified to new requirements. The FAA gives a giant list of requirements you have to show compliance towards, and then Boeing has to meet every one and the requirements are the same whether it's a clean sheet or brand new design.
    Boeing can try to claim similarity on specific requirements, but then they have to make an argument (that the FAA evaluates) on why it is so similar it doesn't need to be tested to meet a certain requirement. The FAA is by nature cautious.

    I'd also disagree that a "clean sheet" design is inherently safer than a "re-use" airplane. With God Knows how many million hours of flight time the 737 family has, there's a ton of data on how it performs. You know a whole bunch of the components are safe, you know the life of the airframe, you know when maintenance is needed. A clean sheet design doesn't have all that data. The reason these MAX airplanes crashed is probably due to something new - the more new things you introduce, the more chances something doesn't work the way you expected it to. Remember the 787 cracking issues? That was because Boeing used carbon fiber technology and didn't fully understand how it would handle the stresses of aviation. There's lot of good reasons to do clean-sheet designs, but safety is not one of those reasons.
    Snohomie
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Re: Ethiopian 737-8 Max UPDATE
Sat Mar 16, 2019 4:20 pm
  • I worked from 1990 to 2007 for Rockwell Collins Avionics (in the Seattle Service Center), spending most of my career there as the main autopilot computer tech. 757/767 had one model of autopilot computer, 747-400 had a newer version. Helped develop the 777 fly-by-wire autopilot (totally different from 757/767), then the 737-400/etc. (which replaced the older Honeywell autopilots, and allowed auto-landing). I was slightly involved in developing the 787 autopilot, but early on in that program I transitioned to maintaining all the test equipment in the service center (including the automated test benches for all of the autopilots, TCAS, SATCOM radios, and weather radars). I may know a thing or two here...

    757/767 and 747-400 are standard digital autopilots that drive hydraulic servos at the control surfaces which are also connected to the controls via cables (as a last-ditch control scheme). 737-400+ are the same. 777/787 are full fly-by-wire where the autopilot computers talk to the main flight control computer which command electrical controls (stepper motors, basically) at the control surfaces. The fly-by-wire autopilots also have a secondary task of controlling feedback servos that drive the pilot's controls to mimic the way they would respond if they were still attached via cables. This is as opposed to the joystick controller of the Airbus planes that don't give tactile feedback to the pilot of what the plane is doing.

    Digital vs. analog was decided decades ago - the autopilots in the 707 and 727 were analog, none since. Safety-of-flight avionics get scrutinized even harder than the nuclear controls I work on these days, which would be hard to believe if you worked only on the nuke side and not the aviation side. I noted with some surprise that after generations of using safety-of-flight avionics from only Honeywell or Rockwell Collins that the 737-MAX went with BAE Systems (London based). Probably a typical business decision to buy from the lowest bidder instead of who you know and trust.

    If you think that a new avionics system doesn't need FAA certification on it's own (even if it's being stuck into an existing platform) then I don't know what to tell you because you don't know the first thing about how all of this works. However, it's pretty hard to know what you don't know, so the best simulations you can come up with can fall short if there is a failure mechanism that was unforeseen. Which sounds like what's happened here.

    On the other hand, I'm tempted to make a comment about trusting British electrical systems - just ask anybody who owns an English car!
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Re: Ethiopian 737-8 Max UPDATE
Sat Mar 16, 2019 7:06 pm
  • I was in the pilot training department for a local airline for the last 7 years before I retired, in that time we introduced a brand new aircraft (E-175) and it was at least a year and 1/2 before we were flying revenue with normal pilots, the time developing the training plan was incredible, the amount of hoops that had to be jumped thru in order to get approval from the FAA, the thousands of hours of simulator training and than proving runs, than flying a significant amount of time with a qualified instructor and an FAA inspector before they let you loose on the line, deciding which capabilities of the aircraft that would be used and which would not was thousands of hours of meetings and presentations, ;it is such an anal and microscopic process it would make your head spin.

    However if say you are already typed in a 737, if upgrading to the maxi is just what they call "differences" training which is a much shorter footprint and that could have been the case here? not sure, not sure what other countries training requirements are but don't think for a second that US carriers have not been trained for every possible circumstance in a very rigorous and demanding course (initially) and at least yearly recurrent training and observations from instructors.
    m0ng0
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Re: Ethiopian 737-8 Max UPDATE
Sat Mar 16, 2019 10:26 pm
  • Great responses from qualified folks here. These are very insightful, so thank you for adding depth to this thread.
    Aros
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Re: Ethiopian 737-8 Max UPDATE
Mon Mar 18, 2019 7:45 am
  • Snohomie wrote:I worked several years on Tanker (a modified 767 for the USAF), a few disagreements with toffee. I have 0 experience with anything outside Tanker, and no experience in Avionics, Flight Controls, or airplane level design. So I'm out of my depth in general.

    Several variants of the 737 MAX are shorter than several variants of the 737 NG - including the two MAX airplanes that crashed. The MAX 8 that crashed are a full inch longer than the 737-800 NGs (I was actually surprised by this, I think the one inch is something with the tail-cone but I didn't want to get that far into the weeds).

    Given that much bigger airplanes use flight cables, I think fly-by-wire is used for reasons other than weight. But that's really out of my understanding.

    Point 6 is just flat out wrong - I know this because I helped on a couple certification projects on Tanker with the FAA. Any new part gets certified, then there is airplane level testing for certification, and sometimes old parts have to get certified to new requirements. The FAA gives a giant list of requirements you have to show compliance towards, and then Boeing has to meet every one and the requirements are the same whether it's a clean sheet or brand new design.
    Boeing can try to claim similarity on specific requirements, but then they have to make an argument (that the FAA evaluates) on why it is so similar it doesn't need to be tested to meet a certain requirement. The FAA is by nature cautious.

    I'd also disagree that a "clean sheet" design is inherently safer than a "re-use" airplane. With God Knows how many million hours of flight time the 737 family has, there's a ton of data on how it performs. You know a whole bunch of the components are safe, you know the life of the airframe, you know when maintenance is needed. A clean sheet design doesn't have all that data. The reason these MAX airplanes crashed is probably due to something new - the more new things you introduce, the more chances something doesn't work the way you expected it to. Remember the 787 cracking issues? That was because Boeing used carbon fiber technology and didn't fully understand how it would handle the stresses of aviation. There's lot of good reasons to do clean-sheet designs, but safety is not one of those reasons.


    I love how you just sneak in here and go "Hey this totally isn't my first post in five years but ya business as usual".

    Good to see ya. ;)
    MontanaHawk05
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Re: Ethiopian 737-8 Max UPDATE
Mon Mar 18, 2019 8:16 am
  • So, I was watching Air Disasters on the TV last night and noted that this episode was about an A-330 that suddenly started going nose-down. Luckily for all concerned the pilots overcame the avionics and didn't crash, but a lot of crew and passengers were injured from negative-G suddenly turning positive again. Then the investigators went on figure out that a problem with the avionics was causing the system that controls pitch to think it was about to stall and order an auto-pitch-down. Then they went on to realize that this had happened before to other A-330s and the cause wasn't figured out on those. Then they went on to realize they could find no actual cause and the end fix was a software patch from Airbus to fix a problem that they still don't know the root cause for.

    Looked eerily like the 787-MAX problems, and this automatic pitch controller is a new thing for Boeing since the mods to the airframe to make it a -MAX give it a tendency to want to pitch up.

    And Airbus uses flight controls from European manufacturers. I wonder if we are literally watching history repeat itself, and they'll never find the root cause of this problem, but Boeing has already said they're rolling out a software patch to prevent it from happening?
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Re: Ethiopian 737-8 Max UPDATE
Tue Mar 19, 2019 8:38 am
  • I was totally going to post about the same thing...Watched that episode last night and was like, "Sounds familiar." I like what the pilot said at the end...That the hierarchy should always be pilot #1, computers #2.
    Aros
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Re: Ethiopian 737-8 Max UPDATE
Wed Mar 20, 2019 9:07 am


  • A previous video on the Lion Air B-737 Max MCAS UPDATE 28 Nov 2018 offers some additional depth. Although the author badly confuses the terms elevator trim with stabilizer trim, an attentive read can sort out that confusion. He does mention the big problem of retiring pilots and loss of their depth of experience . He also mention that (general aviation and commercial) pilots are trained to address one emergency at a time ..... not compound problems.

    Pitch control via a moving elevator on a fixed horizontal stabilizer is much simpler to understand and master. That is the starting point for new pilots. Having both a moving stabilizer and a moving elevator compounds the understanding of pitch control. Many years ago, the Air Force launched and funded a study that it described and defined as Human Factors Engineering. I'm inclined to speculate that the limits of human factors training and engineering will force further development of closed loop machine automation as well as reexamination of all follow on pilot training in qualifying for any type that adapts engines to a modified air frame that significantly alters the aerodynamics in a way that requires a augmented feature for specific situations.

    Although the Lion Air video is provided for depth, it remains flawed in that it confuses the term elevator trim and stabilizer trim ...... two moving surfaces that affect pitch and can confuse ........


    For further depth of understand, the following video touches on the authors experience with trends in increasing automation and the challenge it presents to new pilots ......


    ....................................... maybe it has all become too complex. It makes a bush plane feel safe.
    Jville
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Re: Ethiopian 737-8 Max UPDATE
Wed Mar 20, 2019 2:52 pm
  • I just had a realization - I bet I know why the A-330s and the 737-MAX planes are doing what they're doing. Ever heard of the phenomenon of "tin whiskers"? It's a known condition with ROHS-compliant (lead-free solder) electronics where for an unknown reason hair-like conductive strands erupt from circuit board traces and solder junctions, and grow long enough to short out signals. At Rockwell-Collins we actually got an exemption from the requirement for ROHS-compliance from the EU, at least for the safety-of-flight stuff. I bet nobody thought about it when they designed these new auto-pitch-control devices... They would be un-findable after a crash because they are pretty fragile and break off if the device is given a good thump. On the TV show they tested the defective device over and over without finding any repeat of the signal problem, which is exactly what would have happened if it was tin whisker caused.
    GeekHawk
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Re: Ethiopian 737-8 Max UPDATE
Wed Mar 20, 2019 5:14 pm
  • let pilots fly instead of being homer simpson
    m0ng0
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Re: Ethiopian 737-8 Max UPDATE
Wed Mar 20, 2019 10:28 pm
  • Latest Update (March 20, 2019) to continuing coverage where he gets further into "human factors" .......
    Jville
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Re: Ethiopian 737-8 Max UPDATE
Thu Mar 21, 2019 5:54 pm
  • GeekHawk wrote:I just had a realization - I bet I know why the A-330s and the 737-MAX planes are doing what they're doing. Ever heard of the phenomenon of "tin whiskers"? It's a known condition with ROHS-compliant (lead-free solder) electronics where for an unknown reason hair-like conductive strands erupt from circuit board traces and solder junctions, and grow long enough to short out signals. At Rockwell-Collins we actually got an exemption from the requirement for ROHS-compliance from the EU, at least for the safety-of-flight stuff. I bet nobody thought about it when they designed these new auto-pitch-control devices... They would be un-findable after a crash because they are pretty fragile and break off if the device is given a good thump. On the TV show they tested the defective device over and over without finding any repeat of the signal problem, which is exactly what would have happened if it was tin whisker caused.


    I’m not going to pretend to know anything about this stuff but I’ve heard of the “tin whisker” before.

    Actually can’t remember the exact circumstance but it was mentioned in an article that I read years ago.

    You may be on to something and should forward your thoughts to an appropriate place. It is feasible that this phenomenon has been overlooked.
    pmedic920
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Re: Ethiopian 737-8 Max UPDATE
Thu Mar 21, 2019 10:23 pm
  • To my knowledge, a competitive substitute for Tin-Lead solder (SnPb) has yet to be found for critical applications such as Aero/Space Avionics or Medical Equipment among others. The lead in Tin-Lead solders mitigates the formation of tin whiskers. Lead is not water soluble so it suppresses corrosion. In a time of lead hysteria, it remains a favorite alloying metal for critical applications.

    Lead is very ductile. A SnPb solder flows readily and forms an excellent circuit connection with smooth shiny surfaces. By comparison non lead solders are finicky, more suspect and result in a comparatively brittle and ugly connection. The Boeing Company compared the two and concluded that the resistance to vibration failure by Tin-Lead connections is easily ten time better than that of non lead solder connections.

    With resistant to tin whiskers, resistant to corrosion and ductile resistance to vibration failure, I take comfort in the thought that any ambulance or hospital that comes to my aid has SnPb connections in it's life support electronics. I like to feel the same way when it comes to taking flight.
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Re: Ethiopian 737-8 Max UPDATE
Fri Mar 22, 2019 6:11 am
  • Yeah, but *lead*! Think of the children!
    GeekHawk
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Re: Ethiopian 737-8 Max UPDATE
Fri Mar 22, 2019 6:37 am
  • Your right ..... that became the stampede and outcry of many well-intentioned people.

    The 2010 usage of lead, in all applications, was approximately 21 million pounds. Of that, 16.8 million pounds was consumed in batteries and only about 10,500 pounds would have been consumed in IC lead finish if the RoHS directive were not in force for electronics.

    Recall that the expected environmental harm from lead in electronics was the impetus behind the RoHS legislative action. Lead was feared as a contaminant to groundwater. Many well-intentioned people overlook one important fact, however: Elemental lead is not water soluble. Other sources concur: "Lead does not break down in the environment. Once lead falls onto soil, it usually sticks to the soil particles."5 When burned in an open-fire recycling operation, lead was feared to cause a poisonous vapor if inhaled. From NASA6, the facts are:

    An open-fire temperature is approximately 1000°C, but lead boils at 1740°C.
    Thus, the vapor pressure of lead would be negligible, presenting little possibility of lead-vapor poisoning.
    Workers who solder with tin lead (SnPb) solder do not have high lead levels in their blood.


    In the end, there is no evidence that lead in electronics presents a health risk or causes environmental harm. Ironically, many of the proposed lead-free solutions do pose environment problems and many are much worse for the environment.


    Understanding and mitigating tin whiskers >>>>> https://www.eetimes.com/document.asp?doc_id=1279227&page_number=2
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Re: Ethiopian 737-8 Max UPDATE
Thu Apr 04, 2019 9:51 am
  • The latest articles reiterate what we already pretty much know and that was their MCAS system gave improper AOA sensor data forcing the nose down 4 times before the crash. What should NEVER EVER EVER happen in aviation is any automated systems overruling the input of the pilot! EVER!
    Aros
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Re: Ethiopian 737-8 Max UPDATE
Thu Apr 04, 2019 10:44 am
  • In all the systems I worked on for Rockwell Collins (autopilots for 737-300 and +, 757, 767, 747-400 and +, 777, and 787) there was a force gauge on the controls that would turn off the autopilot when the pilot forcefully pushed/pulled/turned on the wheel, stick, or pedals. I don't understand why Boeing they would get away from that, but I note once again that the MCAS is made by BAE Systems (a British company), and I also note that this override feature is absent from Airbus jets where the "control" is a joystick and the pilot's "command" is more of a request.
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Re: Ethiopian 737-8 Max UPDATE
Thu Apr 04, 2019 11:24 am
  • In many companies, a software glitch or error is a mere nuisance. In aviation it literally ends lives. It's incredibly sad that it took the loss of all these hundreds of lives for this "glitch" to be fixed.
    Aros
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Re: Ethiopian 737-8 Max UPDATE
Thu Apr 04, 2019 11:59 am
  • Standards must have changed or the Quality was pushed or inspections reduced due to labor and or as many Management say inspections create additional labor and if they build it per drawings is not needed. so you can turn out more planes. When I worked for a Aviation company both commercial and Military grade they beat on us all the time for holding up flow due to a issue with passing tests and or inspections and that was back in 1999 when I was last in that environment.

    Part manufacturers get changed all the time, date codes of parts can have flaws, you have to test all the time. Nothing is a rubber stamp.

    Each parts manufacturer is also trying to shave costs and cut corners, you have to keep everyone honest and test and inspection does that.

    I was a Certified FAA test tech, wrote failure analysis, corrective actions and did down to component level troubleshooting. I was also a production and developmental integration tech at the same time. I wrote procedures and implemented processes and test procedures as well as ran them.
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Re: Ethiopian 737-8 Max UPDATE
Thu Apr 04, 2019 4:13 pm
  • Here is an informative April 4th update ...........................
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Re: Ethiopian 737-8 Max UPDATE
Thu Apr 11, 2019 4:47 pm
  • Another update. This one addresses human factors a little more pointedly.

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Re: Ethiopian 737-8 Max UPDATE
Mon Apr 15, 2019 12:42 pm
  • This will probably be my last update post on the subject ........................

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