737 MAX

Discussion in 'Politics' started by Bammer, Mar 11, 2019.

  1. DaveFla

    DaveFla Well-Known Member
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    Trim bias.

    Although this is a completely different system, the 737 has had a system that did/does much the same thing during CAT III approaches for years. As pilots, we trained to expect it and let it ‘do its thing’ during a low vis approach.
     
  2. DaveFla

    DaveFla Well-Known Member
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    Yes
     
  3. Zambo

    Zambo Poo Flinger
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    It does a what and when?
     
  4. DaveFla

    DaveFla Well-Known Member
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    I have a type rating in the 737. I have about 3,000 hours in them, beginning with the -200 and ending with the -800. No MAX time. I even instructed in them for a short while, in a Part 121 environment, though haven’t flown one in more than 10 years.

    The trim bias was used in anticipation of a go-around. During an autoland CAT IIIa approaches. Some point below 50’ RA, with dual A/P channels coupled, the stab trim would begin to ‘bias’ nose down trim just in case of a GA without any control input. Just a few tenths of a unit, as I recall, but you could see (hear) it wen it happened.

    As pilots, we anticipated this, and expected it. That was the only time, however, that it would do this.
     
    #44 DaveFla, Mar 17, 2019
    Last edited: Mar 17, 2019
  5. Zambo

    Zambo Poo Flinger
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    Maybe I never heard of it since we don't have autoland. We just hand fly cat3 approaches using heads up guidance.
     
  6. DaveFla

    DaveFla Well-Known Member
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    We weren’t allowed to hand fly CAT III approaches, with or without using the HUD. We had to use CAT II mins when had-flying an approach.
     
  7. Detroitgator

    Detroitgator General Factotum
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    You mean to tell me you actually fly the plane?!?!?!
     
    • Zambo

      Zambo Poo Flinger
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      You're god dam right I do!!!
       
      • Zambo

        Zambo Poo Flinger
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        Yeah it just op specs for our airline. Our HUD has an expanded AIII mode and you can go down to 50 feet. A lot less expensive than installing and maintaining autoland capability

        I searched the FRM for any mention of bias trim or trim bias and didn't see anything so it must have to do with autoland. The closest thing I can think of is the speed trim system but like the MCAS that only operates when hand flying.
         
      • DaveFla

        DaveFla Well-Known Member
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        I’ve done maybe 5 actual autolands in the 737 in my life.
         
      • NVGator

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        Gotta day, I’m digging this pilot geek speak. :naughty:

        Where’s @pilot-in-fla ?
         
      • Zambo

        Zambo Poo Flinger
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        PIF is in his underground bunker sharpening his e-tool and jerking to Melania.
         
        • Bammer

          Bammer Serving up sh*t sandwiches
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          He loves the First Ladies. Let's just hope Bernie doesn't get elected.
           
        • Detroitgator

          Detroitgator General Factotum
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          Who do you think you are? Luke Fukkin Skywalker?!?!!? “Use the Force Zambo... trust me.”
           
        • URGatorBait

          URGatorBait #TeamDubs
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          Hillary isn't in the picture anymore so what's there to talk about? :heehee:
           
        • Taco Gratis

          Taco Gratis Clear eyes. Full hearts.

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          Saw this on a Twitter thread today. Wondering what our more aeronautically experienced (and/or software-designer type) board members think:



           
        • Detroitgator

          Detroitgator General Factotum
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          My experience with tragic failures resulting in death? It’s never one thing... it’s a chain of small, individual failures that add up (not necessarily even compound) to one big one. It’s synergy personified
           
          #57 Detroitgator, Mar 17, 2019
          Last edited: Mar 17, 2019
          • 5-Star Finger

            5-Star Finger Apex predator of the political forum biome
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            How many tubes are feeding information for the automatic trim correction? Given the short time between take off and the crash could it be something similar to what caused that Airbus crash some years ago? If the tubes had picked up debris (or accumulated it through improper maintenance) couldn't it cause the computer to believe the airspeed was much lower than it actually was? I understand that there was at least an awareness of faulty airspeed indications in the cockpit of the Ethiopian flight.

            I was immediately suspicious that our carriers seem to be operating them with no reports of incidents and we have two incidents with relatively new additions to the fleet of two foreign budget carriers.

            I appreciate you taking the time to educate us. I've always loved flying and one of these days I'm going to finally make the time to get a PPL.
             
            #58 5-Star Finger, Mar 17, 2019
            Last edited: Mar 17, 2019
          • gator1946

            gator1946 Senior Member
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            @ Taco

            1. Don't like shooting my mouth off when I don't have the facts.
            2. Read an earlier post I made about cascading events (and see Detroit's post above).
            3. It's a plausible explanation BUT all the facts aren't in yet.
            4. Focusing on software for a moment. If all of his post is close to the truth, he's got one thing wrong. Of course software was A PROBLEM. I don't view the job of a systems engineer as separate from software design. This would be a Harvard case study where the system engineer/software designer fails to understand, pay attention to, or communicate it's impact on the entire system. And consequently the guy coding and other people involved have no clue. The bigger and more integrated the system, the more critical it is to talk to one another. And that's why we do not outsource software development. Something always get's lost in the wash. What you get is not what you need or in this scenario what is absolutely critical.
            5. We still don't know for sure. And I'm still having a hard time believing they dropped the ball like this.
             
            • pilot-in-fla

              pilot-in-fla Deplorable
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              I've been lurking mostly these days. I don't have any personal experience relative to the current issue but the item Taco posted seems pretty credible.
               

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