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Ethiopian airliner down in Africa

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Ethiopian airliner down in Africa

Old 12th Mar 2019, 11:01
  #641 (permalink)  
 
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MCAS and AS (artificial stupidity)

Engineer here - trying to look at MCAS out of the box...

So they say, one AoA sensor outputting wrong data alone can activate the MCAS erroneously.
If that is so, which engineering workgroup at Boeing could in their sane minds design such a system, that is supposed to save you from a stall but instead:
  • decisively flies you into the ground
  • on a calm sunny cloudless day
  • with a (except from the AoA sensor) perfectly functioning airplane and engines
  • with the same system getting indications for:
    • positive vertical (upward) speed within normal margins
    • positive horizontal (forward) speed and acceleration within normal margins
    • secondary parameters like radar AGL data, GPS groundspeed
  • last but not least two pilots, able to look out of the window and able to assess AoA visually

Why would an engineer think it is a good idea to implement such a system that ignores all other available data (which indicates nothing like a stall)? Even if you want to take the pilot/human out of the equation, assuming he put the airplane into an attitude that will result in a stall in the first place, you still have lots of other available data the system can read, that tells it that you are in fact not stalling and that most likely the AoA sensor is telling you nonsense.

Probably the MCAS subsystem will enter the course books of engineering schools, as a textbook example of AS, artificial stupidity, a system designed to be stupid, when you actually need a smart system.

Or are these engineers disciples of the Church of the AoA sensor, since they believe the one and only AoA sensor never fails?

Someone can enlighten me? What did I overlook?


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Old 12th Mar 2019, 11:07
  #642 (permalink)  
 
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Why doesnít Boeing do what another OEM didnít hesitate to do?

On May 24th 2011 a Dassault Falcon 7X experienced a pitch anomaly resulting in a sudden and rapid pitch up in Malaysian airspace. This was recovered by some quick and good thinking on the part of the flying pilot.

2 days later, the manufacturer asked EASA to ground the entire fleet. One day later, the FAA followed.

A key Dassault employee acknowledged that Ďour design was not perfectí. Pretty honorable thing to do for a (rightfully) proud French engineer.

Shouldnít Boeing do the honorable thing, too?

(see article below)

Attached Files
File Type: pdf
7X pitch up incident.pdf (342.6 KB, 144 views)
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Old 12th Mar 2019, 11:07
  #643 (permalink)  
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Originally Posted by KRUSTY 34 View Post
Didnít work with Lion Chesty. Perhaps it is easier said than done?
Most definitely is. I haven't seen the Lion Air data so I don't know if it ran full forward and stayed there or something else. Obviously startle factor might play a part as well but I'm not sure how startling the trim running slowly forward would be but maybe combined with the stall warning going off wouldn't encourage you to haul back as hard as you can.

I'm only saying that it is controllable at either extreme. Just.
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Old 12th Mar 2019, 11:10
  #644 (permalink)  
 
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Originally Posted by Interflug View Post
Engineer here - trying to look at MCAS out of the box...

So they say, one AoA sensor outputting wrong data alone can activate the MCAS erroneously.
If that is so, which engineering workgroup at Boeing could in their sane minds design such a system, that is supposed to save you from a stall but instead:
-decisively flies you into the ground
-on a sunny cloudless day
-with a (except from the AoA sensor) perfectly functioning airplane and engines
-with the same system getting indications for:
positive vertical (upward) speed within normal margins
positive horizontal (forward) speed and acceleration within normal margins-secondary parameters like radar AGL data, GPS groundspeed-last but not least two pilots, able to look out of the window and able to assess AoA visually

Why would an engineer think it is a good idea to implement such a system that ignores all other available data (which indicates nothing like a stall)? Even if you want to take the pilot/human out of the equation, assuming he put the airplane into an attitude that will result in a stall, you still have lots of other available data the system can read, that tells it that you are in fact not stalling and that most likely the AoA sensor is telling you nonsense.

Probably the MCAS subsystem will enter the course books of engineering schools, as a textbook example of AS, artificial stupidity, a system designed to be stupid, when you actually need a smart system.

Or are these engineers disciples of the Church of the AoA sensor, since they believe the one and only AoA sensor never fails?

Someone can enlighten me? What did I overlook?
Yes Interflug, very difficult to disagree with you. Quite amazing, not in a good way. I have been flying the 737 off and on since the late 70s then the -200 through to latterly, the NG. I have continually said that the 737 is an old aircraft with bits bolted on over the decades. The ergonomics of the flightdeck are out of date for 2019 with the stab trim cut out switches hid away to the right of the start levers among many counter intuitive switches / system. I thought that the NG was a step too far, let alone the max. I am not going to join in the speculation but it does not look good. Tragic.
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Old 12th Mar 2019, 11:16
  #645 (permalink)  
 
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Originally Posted by Chesty Morgan View Post
If it gets to the forward stop there's no rush to get to the stab trim cut outs cos it ain't going any further. Fly it away from the ground, might take both of you, then distribute work load accordingly. It'll take something like 30 odd turns to get it back to somewhere more manageable.
From full AND to about 5 units it takes 60 - 70 turns. Manually trimming on ground is easy. In the air itís a different story. Add 300 kts+ and it gets even worse. Not impossible, of course, but much harder.
If any of you would like to try manual trim on your next flight, remember to place the stabilizer cut out switches to OFF. That trim wheel can be very nasty if it starts to trim when you hold the handle.
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Old 12th Mar 2019, 11:20
  #646 (permalink)  
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Originally Posted by wheels_down View Post
The Fiji MAX will be grounded in Sydney. Thankfully they didnít send the other to Melbourne otherwise they would be screwed. The Brisbane flight just got out in time.
Could the authorities give effected airlines a quick 'heads up' to remove or divert their aircraft before any bar comes into force?
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Old 12th Mar 2019, 11:26
  #647 (permalink)  
 
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Originally Posted by Chesty Morgan View Post
Most definitely is. I haven't seen the Lion Air data so I don't know if it ran full forward and stayed there or something else. Obviously startle factor might play a part as well but I'm not sure how startling the trim running slowly forward would be but maybe combined with the stall warning going off wouldn't encourage you to haul back as hard as you can.

I'm only saying that it is controllable at either extreme. Just.
Believe me Chesty I’m not attempting to downplay your expertise, nor the basic nuts and bolts required to save this situation. Unfortunately it appears that two professional airline crews have been unable to prevent their aircraft from flying them into the ground/sea. That sort of ticks the easier said than done box for me.

There are many more moving parts to this story, and I’m afraid we’re not just referring to the trim wheel.
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Old 12th Mar 2019, 11:27
  #648 (permalink)  
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Originally Posted by KRUSTY 34 View Post


Believe me Chesty Iím not attempting to downplay your expertise, nor the basic nuts and bolts required to save this situation. Unfortunately it appears that two professional airline crews have been unable to prevent their aircraft from flying them into the ground/sea.

There are many more moving parts to this story, and Iím afraid weíre not just referring to the trim wheel.
Of course, and I agree with your second paragraph. The trim is just a part of the big puzzle.
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Old 12th Mar 2019, 11:30
  #649 (permalink)  
 
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It has been reported that crew in the following aircraft at holding point (tower frequency) heard the crew advise ATC of 'an airspeed issue' and 'controllability problems' whilst declaring their intention to turn back.
This is not something that appears to be reported at present, which seems odd. (media)

Where is the manufacturer in all this? Funny how the party line always refers to safety, however those in the industry know and understand all too well the commercial prerogative will normally (covertly) take precedence.

Condolences to those people who have been directly affected by this tragic event.
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Old 12th Mar 2019, 11:30
  #650 (permalink)  
 
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Not a pilot, but an engineer.
Reading this stuff, no doubt in my mind that all these aircraft need to be grounded until comprehensive answer and solution is found.
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Old 12th Mar 2019, 11:33
  #651 (permalink)  
 
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Originally Posted by rzw30 View Post
Not a pilot, but an engineer.
Reading this stuff, no doubt in my mind that all these aircraft need to be grounded until comprehensive answer and solution is found.
I'm pretty surprised that these aircraft are still flying in a lot of countries, like here in the United Kingdom for instance. There needs to be a worldwide ban while the investigation takes place.
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Old 12th Mar 2019, 11:36
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Originally Posted by Chesty Morgan
If it gets to the forward stop there's no rush to get to the stab trim cut outs cos it ain't going any further. Fly it away from the ground, might take both of you
Controllable? At say 340KIAS (380 GS)? I very much doubt it.
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Old 12th Mar 2019, 11:38
  #653 (permalink)  
 
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Obvious that many of you do not understand the different forces involved with the stabiliser and elevator. The elevator only generates a small fraction of the force that the stabiliser generates.
On second and third generation aircraft I flew we had a huge wheel with a white mark, a claxon and a by heart emergency drill to stop a runaway.
You cannot override the stab with the elevator on most aircraft.
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Old 12th Mar 2019, 11:39
  #654 (permalink)  
 
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Originally Posted by ifylofd View Post
Where is the manufacturer in all this? Funny how the party line always refers to safety, however those in the industry know and understand all too well the commercial prerogative will normally (covertly) take precedence.
Indeed, with Max sales trailing the NEO by 2900 to 4400 I would be suspicious that Boeing will do everything they can to avoid any suggestion that there is a problem with the MAX.

Boeing enjoyed dominance of this market sector for decades, and the MAX being reduced from dominance to a 40% market share will have the suits worried.
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Old 12th Mar 2019, 11:40
  #655 (permalink)  
 
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Pinch of salt warning.
Interesting observation by one witness, for further consideration: "Tamrat Abera, a witness who saw the plane go down, told The Associated Press smoke was coming out of the rear and the aircraft rotated twice before hitting the ground."
https://www.aljazeera.com/news/2019/...020507489.html
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Old 12th Mar 2019, 11:42
  #656 (permalink)  
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Originally Posted by Capn Bloggs View Post
Controllable? At say 340KIAS (380 GS)? I very much doubt it.
Well they didn't start at 340kts but they let it get there.



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Old 12th Mar 2019, 11:42
  #657 (permalink)  
 
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Maybe it would be good to remind people that aerodynamic forces increase with the square of airspeed. When mis-trimmed airspeed is not your friend.
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Old 12th Mar 2019, 11:51
  #658 (permalink)  
 
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Originally Posted by Capn Bloggs View Post
Controllable? At say 340KIAS (380 GS)? I very much doubt it.
I'm not sure people fully appreciate that the crew only had three minutes to sort this out, that is not a lot of time to process the situation and troubleshoot in any circumstances, but especially so close to the ground at that speed just after take off, no matter what the cause.
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Old 12th Mar 2019, 11:58
  #659 (permalink)  
 
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Originally Posted by jolihokistix View Post
Pinch of salt warning.
Interesting observation by one witness, for further consideration: "Tamrat Abera, a witness who saw the plane go down, told The Associated Press smoke was coming out of the rear and the aircraft rotated twice before hitting the ground."
https://www.aljazeera.com/news/2019/...020507489.html
Having interviewed many folk who have witnessed aircraft accidents, it is not unusual to get the sequence of events in the wrong order or to misinterpret what they are seeing. It is a very traumatic experience for them.
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Old 12th Mar 2019, 12:03
  #660 (permalink)  
 
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Originally Posted by jan99 View Post
Maybe it would be good to remind people that aerodynamic forces increase with the square of airspeed. When mis-trimmed airspeed is not your friend.
And if AOA sensor reports a stall, pitch up force on the elevator is multiplied by 4 by EFS.
(I don't imply that this is what happened for the ET accident, but it did happen with the Lion Air accident)
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