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Very Hot Topic (More than 25 Replies) Boeing 737-MAX 8 (Read 927 times)
Bob_Roller
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Boeing 737-MAX 8
03/16/19 at 23:18:52
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With the news coverage of the latest incident, I was wondering if anyone had any questions about this situation .
I work for an airline as an aircraft mechanic and have worked on this model of 737 for about 2 years .
My employer has 34 of these aircraft, with hundreds more on order .

Here's a YouTube video of the mechanism that is activated to move the horizontal stabilizer, that is believed to have caused both of the Max 8 incidents .

https://www.youtube.com/watch?v=rxPa9A-k2xY
« Last Edit: 03/17/19 at 00:24:16 by Bob_Roller »  

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Tony Smith
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Re: Boeing 737-MAX 8
Reply #1 - 03/17/19 at 02:41:51
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Bob it seems to me to have at its core an over-reliance on the auto-pilot  and insufficient training about what MCAS does and how to turn it off.

The big airlines don't seem to be having the "incidents", but have reported numerous instants of inappropriate activation which were dealt with without too much drama.

Or do I have this wrong?
  

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Re: Boeing 737-MAX 8
Reply #2 - 03/17/19 at 05:48:48
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I have no experience with aircraft but it seems to me they have over complicated things so much that they have put pilots in the position of not been able to trust their instruments. As a back up, couldn't they provide a basic set of instruments based on fundamental measurements with no computers involved and therefore no possibilty of spurious errors.
  

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BPT
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Re: Boeing 737-MAX 8
Reply #3 - 03/17/19 at 06:54:45
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If I'm understanding correctly (maybe Bob Roller can confirm), there were some big changes to the MAX vs just some "upgrades" that you would normally have with a newer version of the same model.

It sounds like some of the changes then caused the need for further changes and were big enough to affect performance and handling, like moving the position of the engines.  This altered the balance, causing the change with pitch, so Boeing came up with a fix via the MCAS software to compensate.  But because this is different than what the pilots were used to previouslı (and it's sounding like the training for the new system and it's differences was seriously lacking), they can be surprised or confused when the software takes over and does it in a counterintuitive way.

Bob Roller - does that sound close, albeit very simplified?
  

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Bob_Roller
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Re: Boeing 737-MAX 8
Reply #4 - 03/17/19 at 12:45:49
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This new system, is in the software, you can't turn it off
.
The only thing a pilot can do, is turn off two switches, that disable the horizontal stabilizer actuator, if they get uncommanded stabilizer trim movement .

The MAX 8, is a pretty much new aircraft, it looks like the previous series aircraft, the NextGen, -600 -700 -800 -900 variants, but that's where the similiarities end .

I had 100 hours of training on this aircraft, I was in training in October when the first incident occurred .

From what I have heard from the pilots that fly  this aircraft, they had 2 hours of computer based training .

The MCAS system was covered in my training, just amazed that it wasn't covered in the pilots training .

Yes, these machines have gotten too automated and complex .

The experience of the current pilots entering commercial aviation are very low in experience .

Not confidence inspiring .

I have not flown since late February, 2001 .

I didn't like what I saw then .
  

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Re: Boeing 737-MAX 8
Reply #5 - 03/17/19 at 14:37:38
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I don't fly as much as I use to but still get out now and then.

Last time I flew on Air Asia I joked with my friend that it must be Bring Your Kid To Work day - one of the pilots looked like he couldn't have been over 25 years old, actually looked younger than that.  And this was a full sized jet (Airbus A320), not a tiny prop job.  Pilots nowadays definitely aren't as experienced as in the past.  And there are so many of the new, budget airlines popping up all over the world I'm sure they're just getting younger and younger.
  

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Re: Boeing 737-MAX 8
Reply #6 - 03/17/19 at 21:02:48
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Thanks Rob for the infomation. I don't fly but have always had an interest in Planes.
  
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Re: Boeing 737-MAX 8
Reply #7 - 03/18/19 at 09:55:57
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This is not confidence inspiring at all. When Bob Roller comments, I listen! Thank you Bob for your detailed reply. At least my bucket list which won't happen anyway got shorter. Forget toying with ideas about Fly 'n Ride...I will think some more about how to transport my small Honda NX250 in a vehicle on this continent(s) for those really long jaunts as I age. I know, the statistics of dying in an aircraft accident are very low and I shouldn't jump to judge, but....
  

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Bob_Roller
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Re: Boeing 737-MAX 8
Reply #8 - 03/20/19 at 19:51:56
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Here's a bit more information about this situation .
Boeing had an option for the MAX 8, an additional Angle of Attack sensor, specifically for the suspect MCAS system, no airline opted for this !!
The Lion Air incident in October, the aircraft involved with this incident, had a similar problem the day before, a pilot riding in the ' jump seat ' in the control cabin stepped in and gave guidance to the crew in command of the aircraft and averted tragedy that day .
The mechanics replaced the faulted sensor, but failed to perform a complete operational check .
The replacement part was faulty, from an overhaul business, my employer had this same issue with these sensors in the early 2000's .
It was finally diagnosed as a faulty circuit on the test equipment, that was used to do a final operational check of the sensor .
Looks like this issue came back 18 years later .
A transcript of the  cockpit voice recorder first incident, came out today and the pilots fought the airplane for 10 minutes before it finally  dove into the ocean .
They went through all of the manuals they had and this was never covered in any of them .
  

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Justin B.
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Re: Boeing 737-MAX 8
Reply #9 - 03/20/19 at 20:43:54
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But, can't the pilot just turn it off and fly manually?
  

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Re: Boeing 737-MAX 8
Reply #10 - 03/20/19 at 21:08:41
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I think that's where the lack of training comes in.  That system causes odd and unexpected things to happen and the pilots don't know how to turn it off
It sounds like it might not be straightforward.  But that's what the jump seat rider Bob mentioned new how to do, while the crew in charge had no idea.
  

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Bob_Roller
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Re: Boeing 737-MAX 8
Reply #11 - 03/20/19 at 21:17:34
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No, it's embedded in software, only thing to disable it, is to turn off power to the horizontal stabilizer actuator, then move a control wheel  manually in the control cabin to return the stabilizer to the correct setting .
I'll try to get some pictures at work tomorrow to show what these are .
  

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Re: Boeing 737-MAX 8
Reply #12 - 03/23/19 at 21:19:59
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Here's a story from the radio (audio link with a transcript to read) that gives the history of the 737 and explains how and why the MAX came about and also about the current problems.
Boeing seems to have rushed to play catch-up with Airbus and then had to create band-aids on top of patches to get over some questionable design.

https://www.npr.org/2019/03/22/705979783/the-evolution-of-boeings-737-jetliner

  

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Re: Boeing 737-MAX 8
Reply #13 - 03/29/19 at 06:04:48
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Bob, 

Is that screw jack the actual horizontal stab actuator?  Last time I saw one of those was as a flap actuator.  To me it moves too slowly for pitch adjustment.  At first glance I thought it was the stab trim actuator. 

I am guessing that it is electrically driven and not hydraulic?  That scares me but I have not spent any time in commercial aviation where aircraft are not subject to "quick" changes of attitude. 

As for the aircraft being software driven and I have no knowledge of the Boeing MCAS, is it partially mechanical driven (e.g., rudder/spoilers/flaps/ailerons) or has everything gone to "fly by wire"? 

Cheers, Dave. 
  

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Re: Boeing 737-MAX 8
Reply #14 - 03/29/19 at 10:08:10
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BPT wrote on 03/23/19 at 21:19:59:
Boeing seems to have rushed to play catch-up with Airbus


I read that too, BPT. It didn't put Boing in a very attractive light. Looks like the key was not enough training on the new patch. Can you imagine, your life is on the line, your plane is out of control, AND YOU BRAEK OUT A F'ING MANUAL TO  FIGURE IT OUT. Starts to make a few hours in the training cockpit look pretty cheap.
  

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