Talk:Maneuvering Characteristics Augmentation System/Archive 1

Lack of triple redundancy
I heard that the relevant sensors are only duplicated so if one develops a fault, the MCAS can become dangerously unreliable and drive the nose down erroneously. Surely triple redundancy should be industry standard?92.23.35.206 (talk) 17:34, 12 March 2019 (UTC)
 * The article will be updated when there is reliable press to support the discussion. Until then, discussion is speculation better conducted on Facebook or Twitter. There is already a certification requirement for redundancy in the control computers and software (RTCA/DO-178C).  I don't know about requirements for sensor redundancy.  It's a Mom and apple pie argument. Who argues against redundancy? The market and regulators do when it costs or weighs too much for its benefit.  We used to believe that two engines were required to fly passengers in the clouds. We used to believe that four engines and a crew of three were required to fly across the ocean.  No longer.  Now we only require two of each. Rhadow (talk) 17:59, 12 March 2019 (UTC)


 * I'm not sure who you mean by "we". I still believe that four engines are required to fly across the ocean. Mock wurzel soup (talk) 09:45, 13 March 2019 (UTC)

PAGE ]]) 15:03, 9 May 2019 (UTC)
 * "We" includes regulators, manufacturers, airlines, and the passengers who choose to fly. Many models of twin-engine A320, A330, B767, and B777 (and others I don't know) are certified for ETOPS (transoceanic) operation. This is not the forum for that discussion, though. Rhadow (talk) 12:08, 13 March 2019 (UTC)
 * As someone that has recently flown across both the Altantic and Pacific on the twin-engine Boeing 787 Dreamliner, I can confidently state that four engines are not a requirement for transatlantic flights. Four was never a requirement, although three engines was a requirement until ETOPS was introduced in 1985 (hence the introduction of trijets). In fact, when the A380 and 747 stop production in the next few years, the only four-engine passenger plane still in production will be the Russian Ilyushin Il-96. I'd highly recommend the Wendover Productions Small Planes Big Oceans video on the subject. --Ahecht ([[User talk:Ahecht|TALK

Also lack of double redundancy. There are 2 physical AoA sensors and 2 FCC, 1 on each side, but the software (including Mcas) running on each FCC uses only one sensor, on the same side, ignoring the other side. There isn't any kind of redundancy, not just in Mcas, also in the Speed Trim System (STS). The STS is present on the 737 NG too, but it's more predictable and 4 times slower. Even with the software update, if the two sensors deviate by more than 5.5 degrees, Mcas can't tell which one failed, so it simply stops working.

Developing redundant systems is very complex. In a proper, dual-channel system 2 computers each run 2 independently developed software on 2 different processors, comparing the output for agreement. "The first issue was letting MCAS operate on a single vane. Boeing can revise MCAS to be a legitimate fail-safe design by fully utilizing both Flight Control Computer (FCC) channels in a brick-wall fashion. Any software patch to stub in a voted AoA vane on one side may not be fully fail-safe. As each FCC has a dual processor, both processors should agree for any command to be issued, yet this still may not be as compelling as using both FCC channels." — Aron Manning (talk) 04:22, 10 May 2019 (UTC)


 * Whether duplex systems are enough depends to a great extent on whether the loss of one would be safety-critical. For example long-range airliners were required to have at least three engines until safe operation on a single engine could be demonstrated. Two AOA sensors are usually enough, however the special circumstances surrounding the MCAS design and operational regime make that questionable in this particular case. We absolutely need WP:RS before we can comment on it here. &mdash; Cheers, Steelpillow (Talk) 13:50, 15 May 2019 (UTC)


 * In case of Mcas the loss of functionality (augmentation) is less critical, than the loss of integrity (runaway in the accidents).
 * Per Lemme's assessment: the Mcas being part of the FCC, but not the AP is a single-channel system. At any time only one FCC is "augmenting" the flight controls, so triple-redundancy is very far from this. Speed Trim System is very similar to Mcas, so much that the FAA admin presented the Mcas as part of STS (debatable). Lemme says about it: "Speed trim appears to be a single channel, single processor command. I can only assume MCAS is as well." Obviously Boeing won't disclose this information.
 * Lemme goes into detail on the safety levels used in certification: "Generally the system Design Assurance Level (DAL) is tied to the level of the hazard created. Where loss of function creates major hazard, DAL C mandates the software and hardware development levels. A single threaded hardware solution would easily meet DAL D, but would be pressed to meet DAL C without redundancy."
 * He summarizes with: "The alternative use of a dual-channel solution, where both autopilots must agree ..., would yield significant benefits." . Proper geek stuff, so this is for the technical-minded editors.   Aron M🍁   (➕)   16:13, 15 May 2019 (UTC)

sources about the software updates say that when the two sensors disagree the MCAS will not activate in the future. The Verge article said that the original software is also not connected to the disagree alert; it takes whatever bad data it is given. the sensors read differently on the ground in the black box data. MCAS acted on this when the flaps retracted.

Anyway, a triple redundant sensor can still fail if two of them froze in the same position; it would outvote the one not frozen. Shencypeter (talk) 12:04, 18 May 2019 (UTC)

Like others said the point of multi redundancy does not guarantee a reliable result every time, but dual or triple redundant systems recognize faults, and is either capable of disabling completely or voting on the better pair, or average, of data. The SPOF is unable to do any of this. We need to have RS still... Shencypeter (talk) 15:10, 22 May 2019 (UTC)

The media is most interested in the lack of double redundancy. The two sensors are there, but the software only uses one on the same side as the FCC it runs on (there's one FCC for each side). It costs nothing (one line of code) to compare the two values, as the software update will do, no additional sensor or hardware installation necessary. This is truly mind-baffling, it shows a design that ignores the basic principle of redundancy even if it's there for free. Redundancy is so universal in avionics, that it's the baseline: the cables are doubled, there are 2 FCCs, both FCCs have 2 different processors, there are 2 thumb switches for the trim, and - new with the NG - 2 cutout switches for the trim motor. The whole chain is doubled, and that has significant costs. Redundancy in software costs nothing, yet it is missing. This is as negligent as flying up to FL410 without PACs turned on.

With the redundancy in the software update Mcas will be disabled if the two readings differ with more than 5.5 degrees (primary source). In comparison with tripple-redundancy Mcas would still work in 1 sensor failure, but "according to Boeing" Mcas is not necessary to safely fly the plane. Opinion: there will be few cases when Mcas disables, even fewer when the pilot goes into high AoA maneuvers too; in those cases the pilot will be surprised by the handling, and there have been crashes caused by such surprises (see Boeing 727 lessons). Naturally such crashes will be deemed pilot error, although Boeing is pushing the "no simulator time necessary" doctrine. Pilots should be trained for the stall tendency with Mcas disabled (an unstable condition). — Aron M🍂 (🛄📤)    16:25, 22 May 2019 (UTC)


 * I would just caution editors here that the talk page is for suggesting improvements to the article not for debating the subject of the article, please see WP:NOTFORUM. Let's stay on track, please. - Ahunt (talk) 16:52, 22 May 2019 (UTC)

we can’t defend sources without discussing the topic though :-) Shencypeter (talk) 12:51, 27 May 2019 (UTC)

Boeing 737 MAX aircraft have engines installed higher and further forward than other 737 models. This caused an upward pitching moment.
Having engines installed higher should REDUCE the upward moment. Having them installed more forward or aft should not change this moment, hence the ancient planes like DC10 that had their engines at the very back Stefjourdan — Preceding unsigned comment added by 2401:7000:B067:E200:7D72:F822:7D38:C872 (talk) 23:46, 14 March 2019 (UTC)


 * Hello Stefjourdan, while you may have a better understanding of the physics of the 737, nevertheless, the engineers at Boeing decided the MCAS was necessary and the executives decided to pay for it. We Wikipedia editors have to rely on press accounts and not original research. Rhadow (talk) 15:36, 15 March 2019 (UTC)
 * I tweaked the wording a bit (in the 737 MAX article since this was merged) using a quote from The Air Current. Appable (talk | contribs) 20:20, 15 March 2019 (UTC)

Hi. Thanks for attacking me, typical of Wikipedia. I was just asking a question you know? Yes they decided to implement this system, but the reason why they decided so is known to us only by the opinion of this guy, a journalist, https://www.linkedin.com/in/jon-ostrower-7641557/ apparently not even an general engineer. So YOU Wikipedia editor(s?) relied on his "original research" as far as I see and it's good that you have tweaked the wording to " According to The Air Current". My opinion is still that this UPM theory might be completely invented by him or another journalist Thanks stefjourdan — Preceding unsigned comment added by 2401:7000:B067:E200:4996:2B09:8502:BE55 (talk) 08:45, 17 March 2019 (UTC)

"The LEAP engine nacelles are larger and had to be mounted slightly higher and further forward from the previous NG CFM56-7 engines to give the necessary ground clearance. This new location and larger size of nacelle cause the vortex flow off the nacelle body to produce lift at high AoA. As the nacelle is ahead of the C of G, this lift causes a slight pitch-up effect (ie a reducing stick force) which could lead the pilot to inadvertently pull the yoke further aft than intended bringing the aircraft closer towards the stall. This abnormal nose-up pitching is not allowable under 14CFR §25.203(a) "Stall characteristics"."

I presume this is the primary source, and The Air Current is the secondary. — Aron Manning (talk) 04:32, 10 May 2019 (UTC)

Claim that Airbus led Boeing into (in fact anything)
I removed for the second time a claim that "Airbus led Boeing in adoption of systems that would not permit a pilot to put an airliner in a dangerous regime." This is unsourced and cannot stay unless backed by reliable sources. Rentzepopoulos (talk) 11:07, 15 March 2019 (UTC)

Merge this into 737 MAX article?
It seems to me that this article would be best merged into Boeing 737 MAX. Please discuss at WT:AV. Rosbif73 (talk) 11:33, 15 March 2019 (UTC)
 * Done. I merged about half of it across, the rest was a poor duplicate of stuff already in the crash subtopic article. &mdash; Cheers, Steelpillow (Talk) 20:04, 15 March 2019 (UTC)


 * I think this merge was premature. Unless "Maneuvering Characteristics Augmentation System" is a Boeing trademark, it's quite possible that similar systems might be used on non-Boeing aircraft. Mock wurzel soup (talk) 21:03, 15 March 2019 (UTC)


 * Hello Appable, thank you for your edit. It doesn't matter anyway. "Experienced aviation editors" (their words) have met over at their clubhouse (WT:AV), discussed AfD, then deleted nine thousand words, it being a "poor duplicate". A snippet went into the very long Boeing 737 MAX article. Rhadow (talk) 21:08, 15 March 2019 (UTC)

Content dispute

 * Please NOTE for clarity that the above heading was added sometime after the thread was created and edited. I oppose the addition of anything that refactors a talk page including this heading as it potentially changes the meaning and flow of the original conversation and in this case there is simply no need for such an addition.  Please also note that the editor insisting on this addition has been warned very clearly about the dangers to his editing rights about continuing to make tendentious edits such as this.  Here  [] Andrewgprout (talk) 23:59, 29 May 2019 (UTC)
 * Indeed, adding this heading became necessary after Andrewgprout made 4 deletes to this talk page, removing the anchor in this place (05-29 18:01, 05-29 07:32, 05-28 17:29, 05-27 21:00). The heading is perfectly apt, as I initiated the content dispute here (05-24 21:50) after Andrewgprout reverted (05-24 21:01) my addition of a reference to the article. There is no tendentious editing, and no need for wiki-lawyering threats. — Aron M🍂 (🛄📤)    02:24, 30 May 2019 (UTC)

The official (primary) source also matters for those, who want to check the references. There is no reason (policy) to remove it (diff), please reinstate the reference. Thank you.

That does not look good: you are not involved with the article, then suddenly reverted an edit within 3 minutes... https://xtools.wmflabs.org/topedits/en.wikipedia.org/Andrewgprout/0/Maneuvering_Characteristics_Augmentation_System Do you have an explanation for this ? — Aron M🍂 (🛄📤)    22:05, 24 May 2019 (UTC)


 * you need to explain what you mean by uninvolved because you are getting very close to claiming ownership of articles which is a very very big problem if you are. You appear to be new here because your editing if failing to understand some of the basics of editing Wikipedia. Firstly Wikipedia is not a directory of references, references are for backing up a detail included in the article nothing more.  If you have a secondary reference that is always preferable to a primary one. If you have a secondary reference a primary one is normally not necessary or useful.


 * And be very careful of being disruptive - from what I can see many people are suggesting things to you but you are simply not listening, evidenced by your own personal definition of consensus, much more of such and people will start to lose patience with you. Andrewgprout (talk) 03:44, 25 May 2019 (UTC)


 * I'd like to ask you to refrain from personal attacks, and remain civil. Your edits in the last 3 days were only reverts of mine. The last revert was 3 minutes after I edited, on this page, that you have never contributed to, not even to the talk page. It seems you are stalking me, and likely doing disruptive edits. Please prove me wrong. I asked you to explain this, will you? Thank you. — Aron M🍂 (🛄📤)    03:54, 25 May 2019 (UTC)


 * I explained to you the difference in importance of secondary rather than primary references, this is what you should be concentrating on. That is my advice if you want to take any note of it. Andrewgprout (talk) 04:11, 25 May 2019 (UTC)


 * Don't get me wrong I do not ask for your advice; I'm reading the actual policies, which seem to disagree with you. Neither did I ask for the uncivil attack, nor the off-topic statements that represent your opinion, and seem to be far from reality. These answers were strawmans to avoid the original question:
 * How did you notice and revert my edit in 3 minutes on a page that you never touched before? — Aron M🍂 (🛄📤)    04:48, 25 May 2019 (UTC)


 * , you can't state an editor can't edit an article because he's "uninvolved", as claiming you are stalked, and those can be seen as personal attacks. Andrewgprout was right to point you the importance of a secondary source. You are indeed a new contributor, and when someone join an established community, it is necessary to observe some time to understand its usages. With time I understood the main way to add information here is to be WP:bold, and to let it vanish when it is reverted, with discussions only if absolutely necessary. Seasoned editors edit the main namespace for over 80%, you are only at 25% right now. Discuss less, do more and don't fret if there is obvious disagreement. Someone else can notice and revert your edit in 3 minutes if he wants - the simplest answer is he's following the page.--Marc Lacoste (talk) 05:05, 25 May 2019 (UTC)


 * Please look at the diff before you make conclusions. The "important secondary source" is still there, with the additional primary source. Both of you misinterpreted my edit as if it replaced the secondary with the primary. This makes all your rant pointless.
 * Now that you seem to have time to give lectures, I'd remind you your positive contribution is very much expected on the EL consensus, to move forward the consensus process that you halted with multiple reverts after leaving the discussion.
 * You complained about WP:COTD before. Please don't do it yourself, let Andrew answer the question. Thank you. — Aron M🍂 (🛄📤)    06:02, 25 May 2019 (UTC)


 * which diff? No need for overcite with a lesser ref. I didn't answered for Andrew, I offered you a simple explanation.--Marc Lacoste (talk) 06:13, 25 May 2019 (UTC)
 * Obviously the diff you linked. — Aron M🍂 (🛄📤)    06:22, 25 May 2019 (UTC)


 * of course I looked at it, and I said "No need for overcite with a lesser ref"--Marc Lacoste (talk) 06:27, 25 May 2019 (UTC)
 * Great. Then why did you ask which diff? Btw thank you for you opinion, it does not counter (see: Graham's hierarchy of disagreement) my reason to add (see at beginning of this thread), thus it is kindly ignored. — Aron M🍂  (🛄📤)    06:38, 25 May 2019 (UTC)


 * Because it wasn't obvious. Ignoring others arguments is not the best way to progress.--Marc Lacoste (talk) 07:01, 25 May 2019 (UTC)
 * Indeed. "Ignoring others arguments is not the best way to progress." The problem is that's exactly what you did in |[the EL dispute] before triggering page protection. You are [blocking progress] since then, and instead disrupt this discussion which is unrelated to you. You need to mind your own advice. — Aron M🍂 (🛄📤)    23:58, 25 May 2019 (UTC)


 * If I stopped arguing in another talk page, it's because I have nothing left to say. I participate as I see fit, not because of your injunctions. But I can participate here if I see it apt. Article talk pages does not belong to anyone.--Marc Lacoste (talk) 05:11, 26 May 2019 (UTC)


 * The question is still: How did you notice and revert my edit in 3 minutes on a page that you never touched before? — Aron M🍂 (🛄📤)    06:02, 25 May 2019 (UTC)


 * As answered by another user the obvious answer is that I have the page on my watchlist. The reason for my revert was primarily as a response to your edit summary indicating that the edit was for a primary reference which is a big red flag to experienced editors that the edit is questionable. There is a reason primary refs must be used with caution as documented in WP:SECONDARY, a policy I have already pointed out to you. Andrewgprout (talk) 06:49, 25 May 2019 (UTC)


 * Which I have read recently. "Wikipedia articles usually rely on material from reliable secondary sources. " "Unless restricted by another policy, primary sources that have been reputably published may be used in Wikipedia, but only with care, because it is easy to misuse them." As the secondary source is still there, the policy has no problem with it. Only you saw a problem, and you reverted twice instead of discussing. This is what the policies suggest? My advice is to re-read WP:BRD.


 * Aron - In regard to your mentioning WP:BRD above. Please note B means bold (that was you), R means Revert (which means I am perfectly entitled to revert your bold edit which I did with an expaination), and D means Discuss this is what you should have done at this point if you were following BRD.  It is NOT what you did however, you did BRR - just saying!  Please take time to read the policies and advice given to you because at the moment you are not digesting this information in anyway except to try to confirm your misconceptions about how things are done, which as a whole you are misinterpreting as you have just misinterpreted BRD. Andrewgprout (talk) 04:51, 26 May 2019 (UTC)


 * "The first person to start a discussion is the person who is best following BRD." – Old wikipedia proverb from WP:NINJA. I'm happy to have invited you to this discussion. Nvm it took 2 reverts before you joined. Simply said: I'm this first person, get your facts straight before accusing me with BRR. I'll reiterate: I frequently read all these policies, and I'm stunned how you turn these upside down. It seems you should take your own advice, or just simply don't waste our time. Thank you 😉. — Aron M🍂 (🛄📤)    03:34, 28 May 2019 (UTC)


 * BRR is not BRD it is that simple - here you are misinterpreting stuff again. Andrewgprout (talk) 03:41, 28 May 2019 (UTC)


 * Indeed. Let me help you: BRD is my Bold addition, your disruptive Revert, and my Discussion, that you are participating in. Take a look at the timestamp at : 22:05, 24 May 2019, then look up when I reverted you (i'll help you): 22:32, 24 May 2019‎. DISCUSS come first. As your revert had a false comment, and it was obviously mistaken, I did not wait for you, along with your uncivil remarks and strawmans, but went forward and fixed it. At best you can call it a BRDR, if you insist. Anyway it's pretentious to preach of discussions, when it took 2 reverts to get your attention. I should also remind you of your revert on the groundings page, that you never ever discussed. That was the third revert in an EW. BRRR as you would say, the last R being yours. Top-down example you make. If I were you I would drop the stick, instead of sinking deeper at this point. Cheers. — Aron M🍂 (🛄📤)    04:31, 28 May 2019 (UTC)

PAGE ]]) 21:12, 28 May 2019 (UTC)
 * Yes I agree this is BRDR - that is not BRD however. BRD stops at D and you know it.  Yes and I freely admit I was not following BRD for my second and final revert of your revert - BRD is a curteous way to behave not an obligation and by that time I was not feeling curteous. Andrewgprout (talk) 05:27, 28 May 2019 (UTC)
 * Sadly, I don't know of any instance when you have followed BRD, despite your repeated reverts of my beneficial contributions. Your "courteousness" is no more than the uncivil personal remarks in your first response to this thread. Your wikilawyering is disruptive, please stop this and instead apply the policies you are talking about. As this discussion does not lead to you LISTENING to reason, I suggest we follow WP:NOTAFORUM. Have a nice day, and please focus on other activities. — Aron M🍂 (🛄📤)    13:37, 28 May 2019 (UTC)
 * WP:BRD is not a policy, nor is it even a guideline. The actual policy just says When agreement cannot be reached through editing alone, the consensus-forming process becomes more explicit: editors open a section on the associated talk page and try to work out the dispute through discussion. Arguing over the exact sequence of events instead of either trying to seek consensus or moving on to dispute resolution is the very definition of wikilawyering. --Ahecht ([[User talk:Ahecht|TALK
 * I fully support BRD, it's a great tool, if used, and Andrew also speaks positively about it. Albeit content dispute resolution did not happen. I started this thread with:
 * "The official (primary) source also matters for those, who want to check the references." Although this is a good reason (for verifiability), this was not addressed sadly, as we veered off-topic. — Aron M🍂 <small style="background:#af01;box-shadow:#af03 0 0 8px">(🛄📤)    21:44, 28 May 2019 (UTC)


 * You have never edited any of the 737 Max articles before, nor the talk pages, even when you were invited. I you had it on watchlist, then how many articles do you watch? And how do you find the time to read through all the summaries? Maybe you do. Then you choose from all that many pages, probably hundreds of edits 3 edits in 3 days, made by me. It's kind of improbable. — Aron M🍂 <small style="background:#af01;box-shadow:#af03 0 0 8px">(🛄📤)    07:14, 25 May 2019 (UTC)


 * I Have no idea what you are talking about, why does any of that matter? Slow down and listen and learn from other editors. Andrewgprout (talk) 07:36, 25 May 2019 (UTC)


 * If you don't understand, then why do you try to teach? To put it simple: the WP:PRIMARY policy does not necessitate deleting the primary source in this case. I have cited the appropriate sentences from the policy. If you disagree, do it with citations, to avoid misinterpreting the policy again.
 * To return to the question: I believe you intentionally reverted 3 of my edits in a row. Do you have a better explanation? — Aron M🍂 <small style="background:#af01;box-shadow:#af03 0 0 8px">(🛄📤)    07:56, 25 May 2019 (UTC)

I have explained why I reverted your edits, of course I did such intentionally, I didn’t do it by mistake. Your edits here are not making much sense. And as another editor pointed out to you in his edit summary revering your last edit the primary ref is not necessary here given the presence of a perfectly acceptable secondary reference. Andrewgprout (talk) 08:11, 25 May 2019 (UTC)


 * This does not answer the question yet again, just avoids it by stating your opinion without any fact that would support it. This discussion is just wasting time. Please refrain from targeting my edits in the future. Thank you. — Aron M🍂 <small style="background:#af01;box-shadow:#af03 0 0 8px">(🛄📤)    08:56, 25 May 2019 (UTC)


 * Aron, Andrew never targeted you. The addition was not a good thing, this is all.--Marc Lacoste (talk) 09:54, 25 May 2019 (UTC)


 * The facts don't agree with you. — Aron M🍂 <small style="background:#af01;box-shadow:#af03 0 0 8px">(🛄📤)    12:41, 25 May 2019 (UTC)


 * Nothing factual but a personal disagreement.--Marc Lacoste (talk) 13:42, 25 May 2019 (UTC)

Further reading is not dumping ground
adding the Boeing PR statement about the software update (diff) just adds an unnecessary link. The only information of value in it is the 5.5 degree tolerance, which I properly referenced in the article, until you reverted it. — Aron M🍂 <small style="background:#af01;box-shadow:#af03 0 0 8px">(🛄📤)    01:12, 26 May 2019 (UTC)


 * The 5.5° diff is already noted in #Software upgrade: "MCAS activation requires both sensors to be in agreement within 5.5 degrees of each other." (The Air Current. 2019-03-27.). As a primary source, the Boeing MCAS page is interesting to see how its creator present it, and is perfectly apt in #Further reading.--Marc Lacoste (talk) 05:05, 26 May 2019 (UTC)

Make the list collapsible if desired. What is dumping ground or not isn’t worth another content dispute, hehe Shencypeter (talk) 12:55, 27 May 2019 (UTC)

Your EL is disputed. "In disputes over external links, disputed links are removed unless and until there is a consensus to include them. " (WP:NOCON).
 * External Links is not a dumping ground for anything remotely related. It is better to add it as a ref, where it has context. — Aron M🍂 <small style="background:#af01;box-shadow:#af03 0 0 8px">(🛄📤)    08:00, 29 May 2019 (UTC)

Article structure
Now that enough on the MCAS itself has been published to make it notable in its own right, I see that someone has restored this article to life. That is all well and good, but this article is not about the Boeing 737 MAX groundings nor the accidents which led to that, nor even why the AOA sensors failed. It is about the MCAS. In this, even its new incarnation leaves a lot to be desired, so I have been restructuring it accordingly. &mdash; Cheers, Steelpillow (Talk) 10:15, 15 May 2019 (UTC)

Useful secondary-tertiary source
https://www.bbc.co.uk/news/resources/idt-sh/boeing_two_deadly_crashes

&mdash; Cheers, Steelpillow (Talk) 07:54, 17 May 2019 (UTC)

Missing details from the grounding's Certification Inquiry
Guys, I just want to point out that there's much emphasis on the single point of failure in both articles, but the article misses other key details from the "aviation engineers" interviewed by Seattle Times (cited in the scrutiny paragraph).


 * Single Angle of Attack, Single point of failure
 * The MCAS deflection exceeds certified limits by 4 times
 * MCAS reactivates as long as bad data persists
 * understated/downplayed safety risks. Shencypeter (talk) 02:45, 29 May 2019 (UTC)


 * Could you dump the sources you mention here, please? Thanks. — Aron M🍂 <small style="background:#af01;box-shadow:#af03 0 0 8px">(🛄📤)    09:25, 29 May 2019 (UTC)


 * https://www.seattletimes.com/business/boeing-aerospace/failed-certification-faa-missed-safety-issues-in-the-737-max-system-implicated-in-the-lion-air-crash/ Seattle times Shencypeter (talk) 12:08, 29 May 2019 (UTC)

Single point of failure vs. recovery options (NG vs MAX cutout switches wiring)
IMHO, because the 737 is not a fly-by-wire aircraft, it is not THAT important whether the system reads from one sensor or two or three simply because the computer does not have multiple-redundancy (there are two computers, but only one is active, and switching to another one is possible only on the ground), and the whole linkage between whatever small computer it has and the flight controls is mechanical and goes through pilot's controls. This aircraft was never meant to fly on full auto. MCAS like STS before it is just a crutch.

The bigger issue is how to recover the problem after runaway trim has been detected. On the NG the pilot can turn off the right switch, this would turn autopilot/STS off, then the pilot can still use electric trim switches to adjust the stabilizer with the help of electric assist. On the MAX the pilot does not have this option - only manual crank. Even with the updated software the Ethiopian crew would not be able to recover using electric trim, and would still hit the ground. Granted, they may not have gotten in such a dire situation at the first place, but if they did, they would not be able to recover because the cutout switches on the MAX are different to the NG, and Boeing does not seem inclined to re-wire them back. https://www.seattletimes.com/business/boeing-aerospace/boeing-altered-key-switches-in-737-max-cockpit-limiting-ability-to-shut-off-mcas

From another article: https://www.seattletimes.com/business/boeing-aerospace/boeings-emergency-procedure-for-737-max-may-have-failed-on-ethiopian-flight/ "The procedure Boeing offered after [Lion Air] accident to keep planes safe now appears to have been woefully inadequate and may have doomed the Ethiopian Airlines jet."

This issue should be described more prominently in the article. Mikus (talk) 17:41, 3 June 2019 (UTC)


 * and I advocate for more MCAS information to be added to this article. My view is that the original MCAS trusts whatever bullish value is provided by the AoA sensor. The update only serves to make it shut off when two sensors do not agree -- only a triply redundant system can decide which pair of sensors are good. We've seen Boeing reverse itself, saying the disabled disagree light wasn't necessary, but later saying it was a mistake to deliver planes without it turned on. But there was another article saying that MCAS was changed from the original design that factored G-forces into MCAS activation: G-forces was removed because MCAS was needed in low-speed recovery. We put a number of secondary sources on the matter here, some of which may be useful. Talk:Boeing_737_MAX_groundings Shencypeter (talk) 02:08, 4 June 2019 (UTC)

Diff: "In simulator sessions, pilots were stunned by the substantial effort needed to manually crank the trim wheel out of its nose down setting." → I think the wording was better before (that was the point), but the ref is wrong in either case, see ["archived" full version of ref]. There is a [more detailed article] mentioning the sim session of Mentour Pilot (he is Norvegian). There was some article mentioning an american airline also recreating this in simulator, but that was vague, not really official from the airline. On Ethiopian_Airlines_Flight_302 I wrote: Pilots have demonstrated in simulator that the trim wheels cannot be moved in severe mis-trim conditions combined with a high airspeed. — Aron M🍂 <small style="background:#af01;box-shadow:#af03 0 0 8px">(🛄📤)  08:39, 12 June 2019 (UTC)
 * Thanks, Aron. I'll use your referenced sources and restore the better diff.Shencypeter (talk) 09:22, 12 June 2019 (UTC)

Sullenberger testimony
http://www.sullysullenberger.com/my-testimony-today-before-the-house-subcommittee-on-aviation/ Shencypeter (talk) 00:08, 20 June 2019 (UTC)

I would point out that this testimony is NOT saying that pilots have no control over the stabilizer trim when the MCAS system is reacting to faulty AOA sensor as the Wikipedia article indicates just before it references foot note #7. They indeed DO have the ability to command "nose down" stabilizer trim using the thumb switches on the yoke and it will override the MCAS "nose up" input. In addition, they have the ability to completely disable ALL automated stabilizer trim changes by switching the "STAB TRIM" switches just to the right of the throttles to "CUT OFF" and then trim the aircraft by "hand" using the wheel. This is covered in the Boeing released notice after the first accident. What Sully was talking about was the "behind the scenes" trim adjusting by an system unknown to pilots for reasons they couldn't understand leading to a loss of control. It's not that pilots are incapable of dealing with this situation, it is just that they are not aware of enough details to properly diagnose the problem and reconfigure to alleviate the symptoms. Sully is decrying the disconnect that automation and complex systems cause between the aircraft and pilots' flying skills because they are accustom to the automation doing the complex stuff for them.

There is another issue though that has recently been noted. That of the force required to move the stab trim wheel when the aircraft is badly out of trim exceeds what many pilots can apply. They decreased the circumference of this wheel with the cockpit redesign making the mechanical advantage less when turning the wheel. So, if the MCAS has misbehaved and created a heavy nose down trim imbalance and the pilots have NOT corrected it before switching STAB TRIM to CUT OFF it may indeed be a problem they cannot solve conceptually solve if they haven't been trained. Boeing's AD clearly provides the necessary procedure, re-trim using the thumb switches or wheel BEFORE you switch to CUT OFF. Again, the aircraft is indeed controllable if one can properly diagnose and apply the proper corrective action.

In all these possibilities, the "problem" really turns out to be with pilot awareness and procedures. They lacked the ability to properly troubleshoot issues with the MCAS because they where unaware of what it was doing or that it even existed. The net effect is the aircraft becomes uncontrollable and the pilots are unable to fly it, but this, to me, is a result of training failures which fell out of documentation being inadequate and how that was allowed to happen is the *real* problem here.

To wit... I recommend the page be edited to remove the inaccurate description of the MCAS as impossible to override, because it is possible and Boeing's Advisory after the Lion Air crash makes that clear. — Preceding unsigned comment added by 199.46.249.140 (talk) 22:28, 26 June 2019 (UTC)
 * You are free to apply your point of view to this article. I added the Sullenberger testimony here as a TODO item but have used this as a citation...yet. We are free to theorize MCAS here but the pilots only had 6 and 12 minutes to do so without prior training. The planes are grounded for 3 months now to do work that should've been done before 400 planes are delivered and two crashed. Choosing to delay the aircraft would've been much less embarassing. Shencypeter (talk) 01:20, 27 June 2019 (UTC)
 * Specifically, Sullenberger was using the term "control wheel" where Boeing seems to use "control column" or "control yoke." Sullenberger was describing the control column cutoff switch which, on previous models, stopped nose down trim merely by pulling back on the column. MCAS exists because of poor feel when pulling back on the column on the MAX, so they got rid of that nice feature. Fotoguzzi (talk) 02:36, 10 September 2019 (UTC)

== As an automated corrective measure, the MCAS was given full authority to bring the aircraft nose down, and could not be overridden by pilot resistance against the trim wheel as on previous versions of the motorized trim. ==

The footnote is Sullenberger's testimony. Sullenberger uses "control wheel" in the same sense as "control column" or "control yoke." Sullenberger is pointing out that on previous 737 versions, pulling back on the control column would activate a switch that would stop stabilizer nose down commands.

That switch is called "column cutout switch." https://www.satcom.guru/2018/11/stabilizer-trim.html

Sullenberger does not refer to the stabilizer trim handwheel.

Fotoguzzi (talk) 09:36, 9 September 2019 (UTC)

I changed "trim wheel" to Sullenberger's "control wheel," but "control column" would fit other usages in the article. Fotoguzzi (talk) 09:46, 9 September 2019 (UTC)

Improvements section
"In particular, there have been no public statements regarding reverting the functionality of the stabilizer trim cutout switches to pre-MAX configuration."

Boeing procedures on previous models called for turning off both switches at once, so as is explained elsewhere in the article by the company president, there is no reason to "revert."

"A veteran software engineer and experienced pilot suggested that software changes may not be enough to counter the 737 MAX's engine placement."

I'm not understanding why this software engineer who has time in simulators is someone worth quoting about engine placement.

"Seattle Times notes that while the new software fix Boeing has proposed 'will likely prevent this situation recurring, if the preliminary investigation confirms that the Ethiopian pilots did cut off the automatic flight-control system, this is still a nightmarish outcome for Boeing and the FAA. It would suggest the emergency procedure laid out by Boeing and passed along by the FAA after the Lion Air crash is wholly inadequate and failed the Ethiopian flight crew.'"

This may have been true before the preliminary report appeared, but is it relevant to the "Improvements" section? Fotoguzzi (talk) 02:54, 10 September 2019 (UTC)
 * This article is underdeveloped compared to the main groundings article as it pertains to the whole aircraft... Shencypeter (talk) 05:24, 15 October 2019 (UTC)
 * Indeed it is but, taking the long-term view, the groundings will soon be a thing of the past. Admittedly, some of the content here is more related to the groundings and the inquiry and is largely duplicated in the groundings article. Conversely, there's a fair bit of content in the groundings article that could usefully be moved to this article. In the long term (no doubt once the groundings are over), though, I suspect that this article will end up being merged back into the main 737 MAX article. Rosbif73 (talk) 15:06, 15 October 2019 (UTC)

Criminal Corporations
The MCAS page doesn't address how the US Government responds when the public is aware of a corporation that murders people. This is appropriate here because MCAS as a system in the 737 Max product is how Boeing murdered people.

Moreover, the MCAS page should refer to a 737 Max page that is rewritten to describe the US Government as largely impotent by political choice, indifferent or protective of corporations like Boeing who create murderous products. US citizens respectively have little to no power to address criminal corporate behavior because their representation is typically corrupt.

As an example, Ralph Nader's complaints (a form of controlled opposition that protects the company by carefully controlling and creating protest against it) are not the equivalent of obtaining justice that would presumably require the Federal Government to "pursue" Boeing management for mass murder.

Recent corporate behavior has included damaging the economy (Wall Street fraud), homicidal behavior in distributing opioids (pharma) with zero prosecutions in the first instance, and primarily other-than-federal lawsuits in the second instance. — Preceding unsigned comment added by 173.120.141.146 (talk) 02:40, 19 October 2019 (UTC)


 * WP:NOTFORUM--Marc Lacoste (talk) 06:25, 19 October 2019 (UTC)

Referencing errors
Looks like this article is trying to share a lot of content with the Boeing 737 MAX groundings article. The sharing is poorly executed and there are numerous referencing errors -- lots of undefined references and a couple of undefined references, too. I'll try to straighten these out, but it's quite a tangle. In at least one instance, it seems like the groundings article is referencing this article, but then that text is included back into this article leaving readers wandering in a circle. -- Mikeblas (talk) 22:05, 27 October 2019 (UTC)

Glitch fix
When shortening the lead, I had edit conflict with tag Bot. I copied the entire article, including my shortened version of the lead, and replaced the upper text with my text and published. Somehow, I over-duplicated the whole article; that's why byte numbers were so large. Went back and deleted the extra copy or copies. DonFB (talk) 10:26, 25 July 2021 (UTC)