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Ethiopian airliner down in Africa

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Ethiopian airliner down in Africa

Old 17th Mar 2019, 16:02
  #1761 (permalink)  
 
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On many of the accidents discussed here on PPRuNe, commentators are regularly criticised for "not waiting until the accident report is released".

I wonder why, in contrast, it seems accepted that Boeing can have a software fix done in weeks, way before any reports are produced, to get the aircraft back in the air.
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Old 17th Mar 2019, 16:03
  #1762 (permalink)  
 
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Is any of what's described yet designed into any production PFD?
probably not- reason- although assigned to Boeing- the incorporation of such would require bucu approvals in house- extreme flight testing- and worst of all, payment to the inventor. Years ago, an employee ( not myself ) came up with a simple ' quick change ' drill chuck' sort of like an air hose connector. required fitting a matchin piece on each drill. Worked great- put into production and no doubt still in use. So inventor got small royalties- but after a year or two with thousands in use, the royalties added up to a tidy sum. Company said - hey we need to change our deal- employees should not make that much money off a patent. Major battle ensued- Boeing lost.

There is more than one story like that . ..

Last edited by CONSO; 17th Mar 2019 at 16:18.
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Old 17th Mar 2019, 16:06
  #1763 (permalink)  
 
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Originally Posted by derjodel View Post
Lion air's FDR show that the trim was moved to full of the available 7 notches (it's not clear how those translate to degrees). They would certainly still be alive if there as a limit. They kept it in air at ~ 3 notches. If max needs more to get out of stall, perhaps it does need a larger hstab/eleveator instead of a hacked together software?

Or perhaps the key really is the reset. Does mcas reset with each trim input and takes the current position as the new neutral? If AoA vane is sending wrong data it's easy to see how this would result in a runaway trim.

This image shows the difference between a 737-800 (yellow) and MAX (magenta). Notice the bigger nacelles and same hstab size.

I thought 0.6 was a hard limit... e.g, we move this much and then it's up to the pilot. If it was 0.6 every 5 seconds it's still bad, but at least easier to manage.
What strikes me in the image is the tiny elevator? It would have been very interesting to see the same picture of the A320 tail/elevator.
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Old 17th Mar 2019, 16:17
  #1764 (permalink)  
 
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A software patch to fix and inherently unstable aircraft. brilliant. Cant wait for it!
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Old 17th Mar 2019, 17:18
  #1765 (permalink)  
 
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I found a picture of the A320. It seems like the elevator, as a percentage of the stabilizer, is quite a bit larger.




Compared the the B737


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Old 17th Mar 2019, 17:38
  #1766 (permalink)  
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March 17, 2019 12:15 p.m. ET https://www.wsj.com/articles/ethiopian-airlines-black-boxes-showed-clear-similarities-with-lion-air-crash-11552839318?mod=hp_lead_pos4 *

Analysis of Black Boxes of Crashed Ethiopian Airlines Flight Showed ‘Clear Similarities’ With Crashed Lion Air Flight —Ethiopian Transport Minister

*Data from ET302 Black Boxes Has Been Validated by Ethiopian, U.S. Investigators—Minister
*Investigators Were Able to Recover All Relevant Data from ET302 Black Boxes—Minister
*Preliminary Report on Crash to Be Released Within 30 Days—Minister
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Old 17th Mar 2019, 17:40
  #1767 (permalink)  
 
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Originally Posted by Lake1952 View Post
Light aircraft pilot since the mid 70s... under what circumstances would a 737 variant require full UP trim or full DOWN trim? On the aircraft that I have flown, the trim spends all its time somewhere in the middle of the range. So again I ask, what purpose is there to having such extreme ranges of trim that it requires huge control forces to counter?
the speed envelope and cg envelope on a swept wing, transport category aircraft is much greater than a GA aircraft.
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Old 17th Mar 2019, 17:41
  #1768 (permalink)  
 
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Originally Posted by ferry pilot View Post
The Electra was shedding wings but was not grounded, even after the second one, and the entire industry pitched in to find the cause, fix the problem and get it out of the headlines. There are many reasons why that will not happen now . . .
Just a reminder: Ultimately, a third of the Electras ever built were either lost in crashes or written off as too damaged to repair. Perhaps it will be a good thing if "that" does not happen now.

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Old 17th Mar 2019, 17:46
  #1769 (permalink)  
 
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Originally Posted by LandIT View Post
Read all that. Stab screw found pointed down. Are you suggesting pilots pushed it that way? Right. So furthermore they couldn't pull it back in time. Not a good system then right?
If MCAS ran the stab full down it occurred through a number of cycles and over a significant period of time. Where were the pilots?
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Old 17th Mar 2019, 17:51
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Originally Posted by Sailvi767 View Post


If MCAS ran the stab full down it occurred through a number of cycles and over a significant period of time. Where were the pilots?
Two crews went into that trap. Doesn't this make you think more critical about the design of MCAS?
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Old 17th Mar 2019, 17:57
  #1771 (permalink)  
 
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However, pilots and aviation experts say that what happened on the Lion Air flight doesn’t look like a standard stabilizer runaway, because that is defined as continuous uncommanded movement of the tail.On the accident flight, the tail movement wasn’t continuous; the pilots were able to counter the nose-down movement multiple times.In addition, the MCAS altered the control column response to the stabilizer movement. Pulling back on the column normally interrupts any stabilizer nose-down movement, but with MCAS operating that control column function was disabled. These differences certainly could have confused the Lion Air pilots as to what was going on.Since MCAS was supposed to activate only in extreme circumstances far outside the normal flight envelope, Boeing decided that 737 pilots needed no extra training on the system — and indeed that they didn’t even need to know about it. It was not mentioned in their flight manuals.
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Old 17th Mar 2019, 18:21
  #1772 (permalink)  
 
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Ethiopian safety board

I give full respect to the Ethiopian safety board investigating this crash.

but given that the two 737max crashes raise such massive questions about aircraft manufacturing,government and trans national oversight and trillion dollar industries as well national interests for the US aircraft msnufacturing industry vis a vis China snd Europe ,are tje Ethiopians a tiny bit out of their depth?
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Old 17th Mar 2019, 18:21
  #1773 (permalink)  
 
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Wonder no more

Originally Posted by WHBM View Post
On many of the accidents discussed here on PPRuNe, commentators are regularly criticised for "not waiting until the accident report is released".

I wonder why, in contrast, it seems accepted that Boeing can have a software fix done in weeks, way before any reports are produced, to get the aircraft back in the air.
Wonder no more --> $
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Old 17th Mar 2019, 18:22
  #1774 (permalink)  
 
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So how often does MCAS operate?

Naive question from slf. I seem to recall that T tail aircraft had stick pushers that operated if you got very close to the stall, but that you normally would not get that close.

At what angle of attack does MCAS operate and how far from the normal post take off angle of attack is this?
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Old 17th Mar 2019, 18:25
  #1775 (permalink)  
 
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Originally Posted by gearlever View Post
Two crews went into that trap. Doesn't this make you think more critical about the design of MCAS?
this forum is full of people who severely overestimate the capacity of human brain, also (or speciall) their own.

At the same time, most would fail a simple attention test

not that it’s their fault. It’s due to the design of human brain. Yet we design machines pretending this is not the case. Just another human fault i suppose.
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Old 17th Mar 2019, 18:46
  #1776 (permalink)  
 
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Originally Posted by OldnGrounded View Post
Just a reminder: Ultimately, a third of the Electras ever built were either lost in crashes or written off as too damaged to repair. Perhaps it will be a good thing if "that" does not happen now.
otoh, the Electra continued as the Navies P-3. For a very long time. One of the last Electra crashes I recall was attitude indicator failure.
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Old 17th Mar 2019, 19:15
  #1777 (permalink)  
 
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Is an Easy fix proof of sloppy work the first time around?

Here is a thought.

Rumors will have it that Boeing has an MCAS software fix by the end of March, a mere five months after the Lion Air crash, and if this fix is indeed a real fix, and not just a small tweak of some parameters, doesn't this show that Boeing has the knowledge, skills and capacity to crate safe MCAS software.

So this leads me to ask, if this is really true, why the hell did they not do it correctly from the beginning. I am certain that if it comes out that this is an easy fix, and that Boeing did not prioritize it the first time around, that Boeing will be open to severe liability claims.

Clearly this shows that the priority was to get the MAX out fast, and grab as many costumers from the NEO as possible.

I really think that a fast fix shows that Boeing could have done it correctly from the beginning, but chose not to spend the required resources on it.
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Old 17th Mar 2019, 19:16
  #1778 (permalink)  
 
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It seems as if the bottom line is that the safety margin of the legacy 737 was simply eroded to an unacceptable degree with the new engines and became “cigarette paper” thin with the MAX in the search for ever better fuel economy. Boeing recognized this during the development phase and tried to code their way out of it with MCAS thereby creating a solution which may well be more dangerous than the original risk.

Is that reasonable summary ?

I wonder what parameters have been changed with the new software patch, and I’m still curious about the purpose of the 5 second delay which could easily trick pilots into believing there was no problem with the system.

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Old 17th Mar 2019, 19:18
  #1779 (permalink)  
 
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Originally Posted by HarryMann View Post
No, i dont believe most are saying that exactly . . But aren't you equally saying engineers no longer need to be engineers (that live and breathe aeronautic and human interfaces, and are proactive designers, whilst this sounds a somewhat reactive solution ).
Amazed spinning that trimwheel about like that ever passed muster at Boeing let alone nodded through by AW @ FAA - a dozen things could be predicted to go wrong day one of concept by a brainstorming group of experienced systems and aeronautic engineers.
assuming that trim wheel is just like in the 727 and the stab does not move without that big wheel spinning and that it is as loud as it ever was? It is a powerful visual and aural que of what is going on. If it is turning then it should be because speed and or configuration is changing and if I have commanded neither and that stab is moving, I want to know about it.
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Old 17th Mar 2019, 19:21
  #1780 (permalink)  
 
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A software patch to fix and inherently unstable aircraft. brilliant. Cant wait for it
The aircraft is not inherently unstable. Where on earth did you get that idea? MCAS is about reducing AoA at extremes due engine nacelle effects. The fact that a faulty AoA sensor can activate it is the issue. Then that SOME crews have been unable to process what is occurring and turn off the stab trim, or hold manual wheel, or use electric trim against MCAS input.
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