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Ethiopian airliner down in Africa

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Ethiopian airliner down in Africa

Old 18th Mar 2019, 02:04
  #1841 (permalink)  
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The Seattle Times article makes for very disturbing reading. Again, FCeng84's detailed clarifications have helped a lot.

In the article, one light-bulb moment for me was that the 'Resetting' of the MCAS was in fact a 're-datumizing', (my term) which allows one to understand the summed inputs reaching the end of the jackscrew.

EDIT, just noticed the quote by safelife back here.

Ethiopian airliner down in Africa


Talk about elephants in the room. I'd missed this entire page - see Ian W.



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Last edited by Loose rivets; 18th Mar 2019 at 02:18.
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Old 18th Mar 2019, 02:07
  #1842 (permalink)  
 
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Has anyone told him that there is a removal option?
He would have to know there is such an option. Every Boeing airliner since the 1960's has had that option, and it has been in every checklist.

Was he aware of the option, and was it regularly trained, would be the questions I would be asking.
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Old 18th Mar 2019, 02:14
  #1843 (permalink)  
 
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Originally Posted by Rananim
Mullenberg is an MA in aeronautics and by all accounts a well-rounded guy.He has a good engineering background.
I think you are talking about Dennis Muilenburg (not Mullenberg) who is the CEO of Boeing.
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Old 18th Mar 2019, 02:17
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Originally Posted by deltafox44
Except that A321 has 3 AoA probes, 2 of which were faulty, and the stall protection could be countered by aft stick (on mini-stick required force may not exceed pilot strength, contrary to a control column)
Actually the stall protection could not be countered by the sidestick in normal law. The pilots switched off two of the three ADRs giving them alternate law without stall protection (just speed stability).
This was at that point not a published procedure and it is very likely that lesser pilots with no technical backup from the company would not have successfully completed the flight.
Having said that, a 3 out of 2 voting system is vastly superior to alternating between AOA 1 and 2 as Boeing has done with MCAS.
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Old 18th Mar 2019, 02:17
  #1845 (permalink)  
 
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Originally Posted by FCeng84
Thoughts on Seattle Times article published Sunday morning Seattle time

A second point that did not come through particularly clearly in the Seattle Times article is that the pending MCAS software update has been in the works at Boeing since shortly after the Lion Air accident. As the data for the Ethiopian accident is not yet available (or maybe just came available) nothing that Boeing would be getting out the 737MAX fleet over the next couple of weeks could possibly be based on the most recent event. I'm sure that the team at Boeing will be evaluating the ET accident data as soon as they are able to see (1) if MCAS played any role in this accident, and (2) if MCAS did play a role, how would MCAS have behaved differently had the proposed updates been in place.
The FAA has stated that " The grounding will remain in effect pending further investigation, including examination of information from the aircraft’s [ET] flight data recorders and cockpit voice recorders." There is no current timeframe or defined endpoint to that investigation. However, with Ethiopia now saying that there are strong similarities between both events, is that sufficient for Boeing to proceed?

The press coverage and viral responses are not comparable to any other sequence of accidents for any other type. References to the Electra, Comet, DC-10 do not apply - these events went viral reaching an amazingly broad audience world-wide and the politically charged actions will have an impact (has airspace ever been closed to any other type?).


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Old 18th Mar 2019, 02:17
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Originally Posted by PaxBritannica
I wonder too about the sales process. It does seem a little odd that carriers in the domestic market opted for an extra element there was no obvious reason to buy (if they didn't know there was a software feature for which it was a single point of failure), while third-world airlines did not. Was it just cost-saving, or did Boeing push a little harder / offer discounts where failures were less likely to be written off as down to poor maintenance / airmanship?
if all 737 Max have the second sensor, why should using it cost more, when the only purpose is _safety_ and avoiding a design fault ?
Come to think, why wasn’t MCAS documented properly in some foreign sales but documented in domestic ones?

i don’t get it.


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Old 18th Mar 2019, 02:22
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Can I ask a question about MCAS?

It's my understanding applying nose down trim, will produce the effect of adding negative pitch attitude. So MCAS when activated is literally pushing the nose down. MCAS is sending nose down trim to bring the nose downward. Is this a completely correct statement from an engineering perspective? Is there any reason to think of MCAS another way? Does trim effect pitch attitude directly or is it providing column force so the pilot changes pitch? Would MCAS ever not be trying to bring the nose down? Is it inaccurate to say MCAS uses nose down trim commands to apply negative pitch attitude to the plane? In other words, does adding nose down trim add negative pitch attitude? Would MCAS ever be active adding trim in a scenario of high AoA and the plane has negative pitch attitude? Is MCAS literally part of the trim system?
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Old 18th Mar 2019, 02:24
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Originally Posted by hans brinker
Actually the stall protection could not be countered by the sidestick in normal law. The pilots switched off two of the three ADRs giving them alternate law without stall protection (just speed stability).
This was at that point not a published procedure and it is very likely that lesser pilots with no technical backup from the company would not have successfully completed the flight.
Having said that, a 3 out of 2 voting system is vastly superior to alternating between AOA 1 and 2 as Boeing has done with MCAS.

Not true. Read the report in the link. The captain was able to hold level flight using 50% aft stick. The ADIRS weren't turned off until over 20 minutes later after consulting with engineering via ACARS.
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Old 18th Mar 2019, 03:22
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WSJ: DOT IG investigating FAA Approvals of 737Max

WSJ: FAA’s 737 MAX Approval Is Probed (full article at the link)

​​​​​​...The Department of Transportation inquiry, which hasn’t been previously reported, focuses on a Seattle-area FAA office that certifies the safety of brand new aircraft models and subsequent versions, as well as a separate office in the same region in charge of mandating training requirements and signing off on fleetwide training programs, people familiar with the matter said.

Files and documents covered by the directive also pertain to the FAA’s decision that extra flight-simulator training on the automated system wouldn’t be required for pilots transitioning from older models, according to people familiar with the matter.

Officials in those offices have been told not to delete any emails, reports or internal messages pertaining to those topics, people familiar with the matter said, adding that the probe also is scrutinizing communication between the FAA and Boeing.

The Department of Transportation inquiry is casting a wide net for documents about potential agency lapses just as House and Senate committees prepare for public hearings in the coming weeks that are expected to grill the FAA’s senior leadership on the same topics.

The DOT investigation is likely to raise more questions about how Boeing designed the airliner, how pilots are trained to fly it and the decisions the FAA took approving the model. The result could be changes to how the FAA certifies aircraft models, particularly giving more scrutiny to design changes from earlier models.
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Old 18th Mar 2019, 03:27
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Originally Posted by FGD135
Rubbish analogy.

To make this video exercise more like the flight situation, change it to one where the viewer must count the number of passes, but then introduce an impediment that momentarily, but repeatedly, blocks his vision. Give the viewer a means to permanently remove the impediment.

Does the viewer realise that his view is being regularly blocked? Does he activate the removal option before time runs out?
I understand what you are doing but the Gorilla experiment is specifically designed to overload the visual / spatial cognitive channel. The theory is that each of us only has cognitive channels that deal with various information inputs. These channels can get overloaded. This is why designers use haptics (feel/touch) like a stick shaker to break through otherwise full cognitive channels. A good example of a cognitive channel is the visual verbal - try to recite a nursery rhyme while you read a paragraph and understand what someone is saying to you. You cannot do all three as your verbal cognitive channel is overloaded. It does appear from what people are saying here that there are some failures that are a cognitive nightmare with visual verbal, aural verbal, graphical, alerts other pilot talking/shouting and the actual handling of the aircraft. This is a common failing the same was said about the AF447 likely explosion of warnings and alerts.

Perhaps the memory items shouldn't be a reasoned chain but a list of immediate safe quick fixes. So for example with Unreliable Airspeed, first action disable stab trim - then go through the subsequent checks replacing stab trim as a last step if the checks indicate that it is safe.

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Old 18th Mar 2019, 03:30
  #1851 (permalink)  
 
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Why did the MCAS activate straight after rotate?

An objective analysis of the the FR24 supplied ADSB data raises many questions.

The first MCAS event (and perhaps the only one), seems to have occurred just after the aircraft left the ground.
The data shows a spike in the V/S at the approximate time the aircraft would have been leaving the ground coincident with a drop in altitude, at the 05:38:47z datapoint.
Remember the aircraft has an IVSI where accelerometers amplify V/S readings at the beginning of a climb or descent.

This spike make have been caused by an instinctive "yug" on the control column following a sensed drop in altitude.
Reports state that ATC knew the aircraft was in trouble even just after this point due to its undulating flight path at low altitude.
The pilot reports of a "flight control problem" occurred one minute after takeoff, around the time that the aircraft was first beginning to pitch down from about 300' AAL.

So what has happened here?

The MCAS will not operate with flaps extended. Yet it appears it was operating when it should not have been.
In conversation with 737 pilots it was stated to me that the A/C can do Flaps 1 takeoffs. At a high altitude airport a low flap/low drag takeoff setting is preferable for an engine out condition.
We know the FO was VERY inexperienced. Perhaps still being trained or on his first line sector.

The question is; Was the flap raised instead of the gear after rotate, thus activating the MCAS?

It would explain much, but not everything.

The MCAS stops operating when the high AOA condition is corrected, is opposed by the electric trim (but only while the trim switches are operating), or if the STAB switches are turned off.

However it does not automatically return to a lower stab incidence. It must be trimmed back to a proper value commensurate with the speed and configuration of the aircraft. If the Stab switches have been turned off as per the procedure, then the STAB must be manually trimmed back to a proper position.

ETH302 accelerated continuously till it crashed; indicating perhaps that the crew weren't minding the shop as they attempted to deal with the trim issue. It went way past VMO.

IF the STAB had not been sufficiently trimmed back from the nose down position, the increasing speed would have given the same impression of a runaway stab even if the switches had been cutout; an increasing nose down trim change, even though the stab trim was inactive.

The increasing force with the increasing speed would have made it eventually impossible for them to counter, perhaps indicated by the recovery at the 05:40:18 datapoint but no recovery at the final dive.

I stress I don't know what happened; however this makes some sense. Happy to be corrected. Kremin


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Old 18th Mar 2019, 03:59
  #1852 (permalink)  
 
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I think Boeing is probably facing a potentially bigger issue than the failure of the MCAS system. The bigger issue is that it is becoming increasingly apparent that the FAA failed to provide adequate oversight of delegated certification functions. What Boeing really needs to fear (apart from the punitive damages from the lawsuits) is that the airplane will have to undergo a complete re-certification. And even if senior FAA officials are satisfied, I am not sure that other world authorities, especially the European JAA are going to take the FAA's word on it this time.
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Old 18th Mar 2019, 04:07
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MCAS and autopilot together?

Originally Posted by Icarus2001
MCAS and autopilot together?
Is your question suggesting MCAS and autopilot might somehow be improperly connected via software logic, contrary to original assumption that MCAS CANNOT trigger unless autopilot is OFF? After reading the ASRS reports of MAX pilots switching autopilot ON during flaps up climb followed by almost immediate nose downs (fortunately stopped by going manual), I have been wondering if one possible explanation could be that through an untested bug in autopilot logic, MCAS code (which was supposedly an entirely independent subsystem) was inadvertently executed within the a/p system. Just a thought, but thus far I haven't seen a good hypothesis for the rather suspicious behavior.
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Old 18th Mar 2019, 04:32
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The first MCAS event (and perhaps the only one), seems to have occurred just after the aircraft left the ground.
For the Lion Air accident flight, the captain's stick shaker activated whilst the aircraft was still on the runway and continued for almost the entirety of the flight. If this was the case here too, then the apparent pitching down and early reports of "flight control problem" may have been the pilot responding to the stick shaker.

The question is; Was the flap raised instead of the gear after rotate, thus activating the MCAS?
If I was a betting man, I would bet my house that this wasn't the case - purely because the odds against having both these events at the same time would be astronomical.
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Old 18th Mar 2019, 04:42
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Originally Posted by Cropduster
I think Boeing is probably facing a potentially bigger issue than the failure of the MCAS system. The bigger issue is that it is becoming increasingly apparent that the FAA failed to provide adequate oversight of delegated certification functions. What Boeing really needs to fear (apart from the punitive damages from the lawsuits) is that the airplane will have to undergo a complete re-certification. And even if senior FAA officials are satisfied, I am not sure that other world authorities, especially the European JAA are going to take the FAA's word on it this time.
from wsj tonight

A grand jury in Washington, D.C., issued a broad subpoena dated March 11 to at least one person involved in the 737 MAX’s development, seeking related documents, including correspondence, emails and other messages, one of these people said. The subpoena, with a prosecutor from the Justice Department’s criminal division listed as a contact, sought documents to be handed over later this month.

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Old 18th Mar 2019, 04:48
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The Lion Air aircraft had a known AOA vane issue. There has been no indication ETH302 did. If it did and we haven't been made aware of it, then you are probably correct. If not....
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Old 18th Mar 2019, 04:57
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Boeing statement on Sunday March 17, 2019:

Boeing CEO Muilenburg Issues Statement on Ethiopian Airlines Flight 302 Accident InvestigationCHICAGO, March 17, 2019 /PRNewswire/ --

Boeing Chairman, President and CEO Dennis Muilenburg issued the following statement regarding the report from Ethiopian Transport Minister Dagmawit Moges today.


First and foremost, our deepest sympathies are with the families and loved ones of those onboard Ethiopian Airlines Flight 302.

Boeing continues to support the investigation, and is working with the authorities to evaluate new information as it becomes available. Safety is our highest priority as we design, build and support our airplanes. As part of our standard practice following any accident, we examine our aircraft design and operation, and when appropriate, institute product updates to further improve safety. While investigators continue to work to establish definitive conclusions, Boeing is finalizing its development of a previously-announced software update and pilot training revision that will address the MCAS flight control law's behavior in response to erroneous sensor inputs. We also continue to provide technical assistance at the request of and under the direction of the National Transportation Safety Board, the U.S. Accredited Representative working with Ethiopian investigators.

In accordance with international protocol, all inquiries about the ongoing accident investigation must be directed to the investigating authorities.

SOURCE Boeing

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Old 18th Mar 2019, 05:00
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Originally Posted by Zeffy
WSJ: FAA’s 737 MAX Approval Is Probed (full article at the link)
The Grand jury can start with Ali Bahrani and the B787 certification.

Regulatory capture complete with revolving doors between regulator and industry. Blurred lines of defined governance. Increasingly well established and proven techniques of separation watered down an increment at a time.

Cost reductions permeating every segment of the businesses.
MCAS certification, the requisite training and haste of system design all reek of cost and schedule control.

Cost reductions seen ex-post for what they are: Short term gain.
Long term is someone else's problem.

President and CEO Dennis Muilenburg weasel words won't cut it Boeing.
As the lights get turned on it will be interesting to watch which cockroach gets squished on the heel.

Last edited by Rated De; 18th Mar 2019 at 05:08. Reason: misread
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Old 18th Mar 2019, 05:12
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Originally Posted by AerocatS2A
Not true. Read the report in the link. The captain was able to hold level flight using 50% aft stick. The ADIRS weren't turned off until over 20 minutes later after consulting with engineering via ACARS.
I did. I was not clear in my response. What I meant was:
You cannot override the stall protection in normal law. While they were able to hold altitude they weren't close to the stall. Before that at higher altitude and during the turns they made, the flight envelope protection pushed the nose down, and no amount of pull would have kept the nose up into a stall, so I had an issue with "the stall protection could be countered by aft stick".
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Old 18th Mar 2019, 05:38
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O1 failure every 30 days pretty well matches up with the facts.
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