Talk:Maneuvering Characteristics Augmentation System

Useful secondary-tertiary source

https://www.bbc.co.uk/news/resources/idt-sh/boeing_two_deadly_crashes

— 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)

@Shencypeter: Could you dump the sources you mention here, please? Thanks. —Aron M🍂 (🛄📤)   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#Useful_secondary-tertiary_source(s) Shencypeter (talk) 02:08, 4 June 2019 (UTC)

To editor Shencypeter: 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#Expert_analysis 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🍂 (🛄📤) 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)

References

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)

DailyBeast not being Aviation

@Marc Lacoste:: If you are rejecting a citation based solely on the domain name and not the content, I hardly find the recent revert convincing.

It's not a WP:cite, it's a WP:EL.--Marc Lacoste (talk) 20:14, 26 July 2021 (UTC)

MCAS INPUT

Current costly aircrafts have MULTIPLE Systems of Sensors to determine their speed, position and attitude. The original MCAS used ONLY ONE AoA sensor input. This FAIL-SURE logic could only be developed and approved by Retards (in rank and file and also in power/top jobs) 123.201.65.73 (talk) 04:09, 2 January 2022 (UTC)

WP:NOTFORUM. Your opinion does not matter here.--Marc Lacoste (talk) 12:45, 2 January 2022 (UTC)

EASA

This article repeatedly uses the acronym EASA without anywhere defining what it means. Similarly, although the Federal Aviation Administration is mentioned by name in the second paragraph, the acronym FAA is used throughout also without definition. 130.246.57.110 (talk) 11:44, 21 February 2022 (UTC)

Done. See my diff 1 and diff 2. Thank you for drawing that to our attention. Dolphin (t) 11:54, 21 February 2022 (UTC)

Needs an updated link 145

Link 145 is sort of broken it no longer points to the referenced document as the FAA document system was revised. I noticed this while looking for info to supplement a documentary on the 737 MAX I was watching.I do not know how to properly add a citation. Here is the link

https://drs.faa.gov/browse/excelExternalWindow/FB91ABC41EF06432862586260051E5DF.0001 Bruce A. WIlliamson (talk) 14:45, 18 May 2023 (UTC)