Boeing 737 MAX family NEWS ONLY

[DWG]

Poking about on the Seattle Times site, I found this article from September, which gives a little more context to former 737 Max Chief Technical Pilot Mark Forkner invoking his Fifth Amendment rights to not surrender documents to the DoJ investigation. What I hadn't seen previously is that it was Forkner who convinced the FAA to go along with Boeing not mentioning MCAS in the Pilot's Notes.

Former Boeing official subpoenaed in 737 MAX probe won’t turn over documents, citing Fifth Amendment protection

Mark Forkner, Boeing's former chief technical pilot on the MAX project, invoked the privilege in response to a grand jury subpoena issued by U.S. Justice Department prosecutors looking into the design and certification of the plane.

www.seattletimes.com

 

[Archibald]

Depressing reading.

Information overload of the crew, First Officer with documented (in 2016)

difficulties to control aircraft during manual flight
[...]
[First Officer's] application exercise for stall recovery is difficult due to wrong concept of the basic principle for stall recovery in high or low level” during a 2017 observation

Recurring maintenance issues/errors, exacerbating

absence of an illuminated AOA DISAGREE alert, due to a misconfiguration in the MAX’s software that Boeing discovered in 2017 but did not plan to fix until 2020
[...]
“The AOA DISAGREE alert was not correctly enabled during Boeing 737-8 (MAX) development,” the NTSC says. “As a result, it did not appear during flight with the miscalibrated AOA sensor, could not be documented by the flight crew and was therefore not available to help maintenance.”
[...]
The runaway stabilizer checklist calls for using the cutout switches if other actions, including electric trim inputs, do not stop the runaway condition. On both JT610 and the March 10, 2019, crash of Ethiopian Airlines Flight 302, another 737-8, pilots used electric trim to counter the MCAS. This interrupted the nose-down stabilizer movements, but faulty AOA data triggered the MCAS repeatedly.
“[Erroneous] MCAS activation does not look like a typical stabilizer runaway, which is continuous uncommanded (runaway) movement of the stabilizer,” the NTSC report says. “During the accident flight, the stabilizer movement was not continuous; the MCAS commands were bounded by the MCAS authority (up to 2.5 deg); the pilots were able to counter the nose-down movement using opposing manual electric trim inputs. . . . After the pilots released the manual electric input and MCAS was reset, there was not another MCAS command for 5 sec.”
There is no evidence of the JT610 crew referring to the runaway-stabilizer checklist or toggling center pedestal-mounted cut-out switches that would have stopped the automatic stabilizer movements. The 737 MAX flight crew operations manual did not contain any information on the MCAS. Boeing determined during the MAX’s development that the information was superfluous based on U.S. Federal Aviation Regulation Part 25.1585 (b), which says, “Information or procedures not directly related to airworthiness or not under the control of the crew must not be included, nor must any procedure that is accepted as basic airmanship.”
The FAA accepted Boeing’s logic, the NTSC report says, adding that the rationale behind the decision “was not formally documented in meeting minutes.”

Problems with an earlier flight of the crashed aircraft, contrasted with what happened on its final flight

“The absence of [JT610’s] flight crew discussion of the previous problem suggests the flight crew might not be aware of aircraft problems that might reappear during their flight,” the report says. “This was different compared to the flight crew of the [previous day’s] flight, who had awareness of the aircraft condition after discussion with the engineer about the aircraft problem and the rectification prior to the flight, which may have helped the flight crew to immediately identify the problem correctly. Being unaware of multiple problems that occurred on the previous flight, including the stickshaker activation and uncommanded [nose-down] trim led to the inability of the flight crew to predict and be prepared to mitigate the events that might occur.”

In reaction:

Lion Air has implemented a series of changes based on the NTSC recommendations. It updated a training syllabus to “enhance [the] flight crew decision-making concept during [an] emergency or abnormal situation,” issued instructions to improve its pilot control-handover procedure and recently introduced a “new training standard and pilot performance review program.”

More at the link.

https://aviationweek.com/commercial-aviation/lion-air-report-details-max-design-and-airline-operational-failures

Boeing in full DC-10 rear-door-issue-denial mode...

 

[steelpillow]

a penal system that decides if the readings for each left/right sensor pair are incorrect, and if so which one of the two is incorrect (and first you have to define which is incorrect), and what to do if it later appears to get better, and what to do if both appear incorrect.

As I understood the solution when it was first proposed, any significant difference would result in MCAS deactivating. No attempt to diagnose which. I'd be surprised if it is more complicated than that.

 

[DWG]

As I understood the solution when it was first proposed, any significant difference would result in MCAS deactivating. No attempt to diagnose which. I'd be surprised if it is more complicated than that.

The problem with that interpretation is the article refers to a change in the overall software architecture of the Max, not just MCAS. And if you decide it's impossible to justify not cross-correlating the left and right side sensor data for MCAS, it becomes very difficult to argue you don't need to do the same for all other data from the two Mission Computers.

 

[steelpillow]

the article refers to...

I can't get past the paywall to see whether or how the plan might have changed. Perhaps you could quote the relevant bits here?

 

[Arjen]

From the Seattle Times piece quoted by DWG:

The software fix has two parts:

• An upgrade to make safe the flight control system — the Maneuvering Characteristics Augmentation System (MCAS) — that activated erroneously on the two crashed flights, in Indonesia and Ethiopia.
• A change to the overall software architecture of the MAX so that its systems take data from both flight control computers on each flight, instead of only one as previously.

 

[steelpillow]

Thank you for this. Yes, contention between the two flight control computers would certainly set the cat among the pigeons on the flight deck! I would think its impact on procedures and hence training would be even bigger than the MCAS fix. So much so that I wonder if there is some misunderstanding going on somewhere.

 

[TomcatViP]

— Airbus Chief Commercial Officer Christian Scherer forcefully rejected the notion that his company is benefiting from the grounding of Boeing's 737 Max fleet while speaking to CNBC during the Dubai Air Show.

"I really need to correct that cultural belief. This does not benefit anyone in this industry, the least of which would be Airbus," Scherer told CNBC's Hadley Gamble on Sunday.

"It's a tragedy, it is an issue for Boeing to resolve, but it is not good for competitors to see problems on any one particular airplane type

Airbus exec: Boeing's 737 Max grounding benefits no one

"It's a tragedy ... it is not good for competitors to see problems on any one particular airplane type," Airbus CCO Christian Scherer told CNBC.

www.cnbc.com

 

[DWG]

He has a point, uncertainty about the safety of the certification process among the public is not good for the industry as a whole. Particularly when most people would be hard put to recognise an individual aircraft as an Airbus or a Boeing.

And on hard-nosed commercial grounds, no matter how much Airbus might have liked to take advantage of anyone wanting to opt-out of a Max buy, their order-books are pretty much full.

 

[steelpillow]

Ah, here's something:

The plan had to change bigtime when the flight sim revealed a deeper flaw in the FCS:

Delays in Boeing Max Return Began With Near-Crash in Simulator - Bloomberg

"Changing the architecture of the jet’s twin flight computers, which drive autopilots and critical instruments, has proven far more laborious than patching the system directly involved in 737 Max crashes."

 

[DWG]

Ah, here's something:

The plan had to change bigtime when the flight sim revealed a deeper flaw in the FCS:

Delays in Boeing Max Return Began With Near-Crash in Simulator - Bloomberg

"Changing the architecture of the jet’s twin flight computers, which drive autopilots and critical instruments, has proven far more laborious than patching the system directly involved in 737 Max crashes."

Interesting. Though it does raise some uncomfortable questions about the flight computer design in pre Max 737s, and disagreements between flight computers has been implicated in several crashes, iirc.

"Developing and testing software on airliners is an exacting process. Manufacturers may have to demonstrate with extensive testing that a software failure leading to a crash would be as rare as one in a billion."

There is no "may" about it. Less than 1*10^-9 Hull losses per flight hour is a certification requirement. Been there, done the maths (actually for one of the cosmic ray bit flips they talk about Boeing testing).

The article linked from it https://www.bloomberg.com/news/arti...lf-profit-gains-on-jump-in-ancillary-revenues , is also interesting.

"
European Union Aviation Safety Agency Executive Director Patrick Ky hit back at claims from Ryanair Holdings Plc chief Michael O’Leary that the authority is “dragging its heels” over the Max, saying it’s simply fulfilling its obligations.

“If Mr. O’Leary doesn’t like it, that’s his problem, but it’s not going to put pressure on me to go faster, I can assure you,” Ky said in an interview in Helsinki. “We are doing what we think is right.”
"

Nice to see the regulators telling O'Leary to keep his opinions to himself for once.

 

[TomcatViP]

Most people don't differentiate a Boeing from an Airbus. Even more an Embraer, a Mitsubishi, a Bombardier or any Russian and then future Chinese airliner. Those that have bet on branding so loudly the name Max post its double tragic crash to instigate fear among passengers hence making them able to identify the plane they are about to board are simply shooting themselves their own feet (and that of the industry). A fraction only of passengers are identifying their plane reading their boarding pass (when this is still possible) and almost never (scarcely in fact) the plane they are-in.

Max or not Max, we all die at that game.

Seems Airbus just concurs to that today (see my previous post

Or here

 

[Desertfox]

The other issue Airbus is afraid off is that if Boeing can not satisfactory fix the MAX, they will have to move forward with an all new (797?) design, which would force Airbus to develop their own counterpart (see 787 -> A350).

 

[steelpillow]

if Boeing can not satisfactory fix the MAX.

I doubt Airbus are losing any sleep over that, unless you can cite a reliable source.
There is nothing inherently wrong with the MAX. Boeing's ability to fix it is a business issue not a technical one. The business does not have the resources to develop a brand new design. it is acutely aware that it needs the income from future MAX sales deliveries to pay for that and therefore has no option but to perform or die. MAX has to be fixed to the satisfaction of the regulators, the only question is when.
What Airbus are surely hoping for is a long and agonising period in which certification keeps getting refused for one reason after another, eating away at Boeing's ability to compete with them in the longer term.

 

[TomcatViP]

You don't understand: the hard beat on non-aerospace business (WTO) will prevent any large subsidy for the next airframe design that will have to replace the A320 serie. It's then a run to the last $ where Airbus position is more unsecure thanks to Bombardier buy (to be developed if not part of an "editorial" cut).

 

[Richard N]

The Long-Forgotten Flight That Sent Boeing Off Course: https://www.msn.com/g00/en-us/money...tandhp&i10c.ua=1&i10c.encReferrer=&i10c.dv=15

 

[Archibald]

And on hard-nosed commercial grounds, no matter how much Airbus might have liked to take advantage of anyone wanting to opt-out of a Max buy, their order-books are pretty much full.

Spot on. Toulouse is churning A320s like crazy, from memory 52 per month with vague hopes to accelerate to 60 but beyond that they hit a brickwall.
More generally 737 and A320 overall numbers are reaching WWII levels - 10 000 and counting -
never seen for jets bar perhaps the MiG series.

 

[galgot]

if Boeing can not satisfactory fix the MAX.

I doubt Airbus are losing any sleep over that, unless you can cite a reliable source.
There is nothing inherently wrong with the MAX. Boeing's ability to fix it is a business issue not a technical one. The business does not have the resources to develop a brand new design. it is acutely aware that it needs the income from future MAX sales deliveries to pay for that and therefore has no option but to perform or die. MAX has to be fixed to the satisfaction of the regulators, the only question is when.
What Airbus are surely hoping for is a long and agonising period in which certification keeps getting refused for one reason after another, eating away at Boeing's ability to compete with them in the longer term.

Agree, the MAX could be an airplane without problem (B737 is a good airframe) if only Boeing hadn't tried to do it the cheapest way they could, and its not the only one to blame for that, airlines like Southwest who wanted a cheapest possible upgrade are too. Now They HAVE to fix it, cause still too much have been invested on it to start from a new thing. And as much as they try to fix it the cheapest way they can, FAA now is very eager the regain the reputation and trust it had before this mess and is now very picky (rightfully) about the fixes.

And on hard-nosed commercial grounds, no matter how much Airbus might have liked to take advantage of anyone wanting to opt-out of a Max buy, their order-books are pretty much full.

Spot on. Toulouse is churning A320s like crazy, from memory 52 per month with vague hopes to accelerate to 60 but beyond that they hit a brickwall.
More generally 737 and A320 overall numbers are reaching WWII levels - 10 000 and counting -
never seen for jets bar perhaps the MiG series.

Funny… I recall reading on this forum Airbus was a failure

 

[Arjen]

The Long-Forgotten Flight That Sent Boeing Off Course: https://www.msn.com/g00/en-us/money...tandhp&i10c.ua=1&i10c.encReferrer=&i10c.dv=15

Above a certain level in an organisation, the only way to fall is up.

 

[galgot]

The Long-Forgotten Flight That Sent Boeing Off Course: https://www.msn.com/g00/en-us/money...tandhp&i10c.ua=1&i10c.encReferrer=&i10c.dv=15

Aboulafia contradicting himself :

“The difference between doing MCAS right and MCAS wrong was not an economic thing. It’s a culture thing.”

but then:
"It wasn’t just technical knowledge that was lost, Aboulafia said. “It was the ability to comfortably interact with an engineer who in turn feels comfortable telling you their reservations, versus calling a manager [more than] 1,500 miles away who you know has a reputation for wanting to take your pension away. It’s a very different dynamic. As a recipe for disempowering engineers in particular, you couldn’t come up with a better format.”

Well, as if putting as much distance from engineers to the management resulting in fears about their pensions if they raise concerns isn’t a "economic thing"…

 

[steelpillow]

Another pre-MAX blooper by Boeing unearthed.
The impossibly stiff manual trim wheel dates back decades to the 737-200 and an operational workaround was devised and added to the pilot documentation and training. This workaround never made it into the pilot information for the MAX:

Vestigial design issue clouds 737 Max crash investigations

After preliminary report into Ethiopian 302, a 53-year old idiosyncrasy in the 737's design is expected to become a focus of the inquests.

theaircurrent.com

The horizontal stabilizer trim is actuated by a jackscrew. When the elevator operates to raise the nose, it sets up a strong force on the jackscrew which opposes any corrective force from the trim wheel. Exerting enough force manually to overcome the force exerted by the elevator gets more and more impossible as speed increases and the jack screw effectively jams in place.
The workaround is called the "roller coaster" technique. Counter-intuitively, the pilot first pushes the nose down further, before easing back to gently raise the nose again. During this easing back period, the elevator deflection reduces or even reverses, its force on the jackscrew does likewise and the manual trim eases up.
Had the pilot training and notes kept track of this issue down the decades, it is conceivable that the pilots might have been able to leave MCAS switched off and recover the plane despite its high speed. There appears to be a prima facie case for criminal negligence here and at least one of the old engineers has been subpoena-ed for the DoJ criminal inquiry.

Seems to me there must now be a strong risk of a regulatory demand for hardware changes to provide adequate manual trim under all flight conditions (or maybe just to provide separate OFF switches for MCAS and the power-assisted trim) before they let that plane into their skies again. Against that, Boeing will argue that in the 45 years of 737 operation since that workaround came out, there has been no call for any other fix. But then, that has also been true of the dual-redundant flight control system they are now being forced to upgrade. At the very least, pilot's emergency procedures for all the intervening variants must be flying out the filing cabinets...

 

[TomcatViP]

Over trim is part of aviation since it does exist. During WWII it was recommended to cruise trim an airplane before attempting an high speed dive. Heck, any low end PC simulator even has trim function implemented one way or another for anyone to practice.

If you fly in GA, it's something that could have been raised early to your attention. Idem for stall*.

You can turn the thing anyway you want but if you don't have flight knowledge (not you personally but generally speaking)
you are not fit to fly, especially as a professional. Passengers trust your sanctioned habitities. Airline count on you in their business model. And engineer expect this minimal understanding.

Any plane is prone to crash if flown outside its flight domain. It's true for Cessna, a Jodel, an F-22 as well as any Boeing or Airbus out there.

If you are used driving stick shift, you won't be surprised of the consequences switching back to first while driving full speed on the motorway...


Regarding your offs switch proposal, this is already there (I posted a link to the relevant checklist month ago here ). Feel free to read.



* I was personally pushed trought my first stall exercice not even having logged 3hr

 

[DWG]

"if Boeing can not satisfactory fix the MAX, they will have to move forward with an all new (797?) design, which would force Airbus to develop their own counterpart"

Not fixing Max would destroy Boeing's market position by leaving them without an A320 Neo competitor for 5-7 years. Larger aircraft may cost more, but it is the volume of the 737 line that is Boeing's lifeblood. The prospect is unacceptable to Boeing's investors, Max will be fixed (and there's nothing unfixable about Max, it just needs a properly developed FCS).

If Boeing did develop a new short-haul airliner, it would mean their cancelling the New Market Airliner (NMA, 757 replacement), because they don't have the engineers to run two development programmes in parallel (or probably the finances). Airbus have basically gained an entire development programme's advantage over Boeing because the A321LR (which is an ultra-long range Neo) is already competing in that market at the bottom end, with the A330 Neo competing in it at the top end. So if Boeing opt not to build NMA they're basically abandoning an entire market segment to Airbus. Additionally Airbus have the A220, with the potential to stretch it to compete in the 737 replacement market sector at a far lower cost.

Remember, at the start of the 2010s both Airbus and Boeing were serious about launching A320/737 replacements, but the airlines weren't ready and opted for Neo/Max development instead. Revamping those plans isn't difficult, though they and the airlines may well prefer to wait a few years for optimised low emission designs.

 

[DWG]

Aboulafia contradicting himself :

“The difference between doing MCAS right and MCAS wrong was not an economic thing. It’s a culture thing.”

but then:
"It wasn’t just technical knowledge that was lost, Aboulafia said. “It was the ability to comfortably interact with an engineer who in turn feels comfortable telling you their reservations, versus calling a manager [more than] 1,500 miles away who you know has a reputation for wanting to take your pension away.

That's money, not economics. And I'd agree with Aboulafia that it's a cultural issue.

 

[DWG]

You don't understand: the hard beat on non-aerospace business (WTO) will prevent any large subsidy for the next airframe design that will have to replace the A320 serie. It's then a run to the last $ where Airbus position is more unsecure thanks to Bombardier buy (to be developed if not part of an "editorial" cut).

"On 11 April 2019, the WTO adopted its final compliance report in the Boeing dispute, confirming that U.S. subsidies to Boeing continue to cause significant harm to Airbus, including lost sales. "

WTO Boeing dispute: EU issues preliminary list of U.S. products considered for countermeasures

The European Commission has today launched a public consultation on a preliminary list of products from the United States on which the European Union may take countermeasures in the context of the ongoing Boeing dispute at the World Trade Organisation (WTO).

ec.europa.eu

As for the A220 - Airbus did _not_ buy Bombardier - Airbus picked up a complete aircraft programme and the first couple of hundred sales for $1 while making Boeing look like idiots. The only expense they're facing on that is setting up a production line in the US, which further advances their strategic intent to become a US company as much as a European one, and which is something they do regularly anyway, cf the Chinese completion centres.

 

[DWG]

You can turn the thing anyway you want but if you don't have flight knowledge you are not fit to fly, especially as a professional. r

Plenty of stories of extremely experienced airmen being overwhelmed by stick forces, people with their feet on the instrument panel trying to generate enough leverage to shift the stick when power assist fails. Trim is no different, but a trim-wheel vs a control column makes it far more difficult to develop the necessary leverage. This is an increasing concern as the pilot population has shifted away from ex-military types towards a more representative mix, giving a shift in average pilot strength. No one can be faulted for not following an instruction that isn't in the pilot's manual, or for being unable to override a mechanical system by sheer brute force (which really, really doesn't meet any professional's definition of acceptable handling qualities).

The possible existence of a work-around does not excuse the airframer from developing a fix.

 

[TomcatViP]

Sorry folks and Admins, I feel like I have to repost one of my earlier post that can be seen on Pg2 of this thread. Emphasizes added by me.

The angle of attack is also used to control an Automatic trim action during manual flight to gradually relieve the pilot of any constant stick forces. This action is not described in the 737NG FCOM and might be the reason why the bulletin is restricted to the 737 MAX type, which has implemented this to increase longitudinal stability for this type.

Any such Automatic trim action which doesn’t makes sense has the feel of a runaway pitch trim which is a very common emergency simulator training scenario. In isolation, this should be easy to spot and the correct action (Cut out the trim as described below) could be taken in relative calmness. I’m inclined to think the JT610 crew had to handle a more difficult and stressing false Stall warning and recovery situation, which is the same between the 737NG and the 737 MAX.

The Stall warning and recovery functions are:

Above a preset AOA, a stall warning audio voice says: “Stall, Stall, Stall” and the Pilots control yoke on the side with the high AOA start shaking as an additional physical warning
If the AOA does not decrease after the triggered Stick Shaker but stays at a high angle, the system then creates a stronger control Yoke force through the Elevator Feel & Centering unit by applying a nose down stick force for the present Yoke position.
As an additional measure, the Flight Control Computer starts a stabilizer trim nose down movement using the Autopilot trim channel. The trim action lasts 10 seconds. The Pilot’s can counteract the trim by using their trim buttons, it overrides the Stall system trim.
If the AOA persists, the Pitch trim nose down will trigger again after a certain time lapse. If the PIlots have counter trimmed, the system waits 5 seconds until it repeats the trim nose down for 10 seconds.
If the crew suspects an Automatic trim action or Stall warning to be false, the Operating Procedure is to switch off the Nose down trim action by disengaging both trim channels of the Pitch trim system and trimming the stabilizer manually by the wheel. These switches are placed on the central pedestal, Figure 4.

Figure 4. Control stand Switch to Cut Out the AUTO PILOT’s STAB TRIM function (No 6) and the PIlot’s trim channel (No 5). No 4 are the Pilot’s trim buttons operating the MAIN ELECTrical trim (No 5) in normal operation. Source: 737NG FCOM.
It’s this action that Boeing’s message conveys, reminding the 737 operators this is the procedure for suspected false stall actions caused by a false AOA reading.

See also here: https://www.flightglobal.com/news/a...-probe-strives-to-comprehend-pitch-up-456702/
(regarding similar nose pitch down and accelerated dive down on the crashed Atlas's 767).

 

[DWG]

IMOHO, Airbus bought a non-proven design

A 'non-proven' design that delivers a 20% fuel burn improvement vs the Max, and is delivering performance better than the book figures at a point in its service introduction where most aircraft are struggling to meet their book figures. I think most airline figures will say if that's 'non-proven', give me more.

 

[galgot]

Aboulafia contradicting himself :

“The difference between doing MCAS right and MCAS wrong was not an economic thing. It’s a culture thing.”

but then:
"It wasn’t just technical knowledge that was lost, Aboulafia said. “It was the ability to comfortably interact with an engineer who in turn feels comfortable telling you their reservations, versus calling a manager [more than] 1,500 miles away who you know has a reputation for wanting to take your pension away.

That's money, not economics. And I'd agree with Aboulafia that it's a cultural issue.

...?... In my world money is all about economics. But if you like...

 

[DWG]

...?... In my world money is all about economics. But if you like...

Economics starts when there isn't enough room on your cheque for all the zeroes.

 

[TomcatViP]

A 'non-proven' design that delivers a 20% fuel burn improvement vs the Max, and is delivering performance better than the book figures at a point in its service introduction where most aircraft are struggling to meet their book figures. I think most airline figures will say if that's 'non-proven', give me more.

Unproven in the sense of long term reliability, sustainment cost and Maintenance network. There is a lot of cost to be added here. On the contrary Embraer buy is devoid of any of this with cash flow unrestricted.

 

[galgot]

...?... In my world money is all about economics. But if you like...

Economics starts when there isn't enough room on your cheque for all the zeroes.

Sorry but doesn’t all Boeing engineers pensions makes a lot of cheques, and thus a number with lots of zeroes… if that is what it needs to be part of economics.

Ok then, it’s an economic culture maybe ?

 

[Jemiba]

This thread is about the 737 MAX, not about US/European, Boeing/Airbus competition.
So, please stay with the original theme, especially as the digressions very easily can lead
into politics ...

 

[TomcatViP]

Canadian Official Calls for Removal of Key Software From 737 Max (Published 2019)

“MCAS has to go,” a manager at Canada’s aviation regulator said in an email to global peers, referring to software in the Boeing plane.

www.nytimes.com

 

[Archibald]

But if they remove the entire MCAS, then the 737 will fly like a pig due to the bigger engines / pylons / wing / CG interactions. No ?
Wasn't the MCAS introduced to correct some kind of exagerated nose down attitude ?

 

[TomcatViP]

...nose-up

 

[Moose]

MCAS wasn't added because it would "fly like a pig," it was added to enable 737NG pilots to hop in and fly without needing extra sim time to learn to handle the nose-up tendency and thus impacting the airlines' training budgets. Outside the nose-up, and MCAS trying to kill you in certain circumstances, I haven't seen much suggesting the MAX is a worse flying experience on the whole.

 

[steelpillow]

But if they remove the entire MCAS, then the 737 will fly like a pig due to the bigger engines / pylons / wing / CG interactions. No ?
Wasn't the MCAS introduced to correct some kind of exaggerated nose down attitude ?

MCAS was introduced to fix a commercial problem not a technical one. However the commercial problem had a technical origin.

The new engines for the MAX were so big they had to be moved forward to clear the wing. Their huge cowlings also moved the aerodynamic centre forwards, leading to reduced stability in pitch. This in turn led to a tendency to pitch up even steeper at high angles of attack during takeoff and landing, risking the plane stalling. Normally this would have been dealt with by enhanced warning devices and pilot training compared to the previous models, possibly also some tweaks to the main flight control parameters or even a third flight control system (FCS) making it triple-redundant. The design would and should have been perfectly flyable.

However this would have required the MAX to be re-certified as a new type, with not only all the extra analysis and testing involved but also pilot re-training. Boeing were so desperate to get MAX flying, due to competition from Airbus, they did not want to wait that long. So they introduced MCAS to mimic the behaviour of the old models and hid it from the pilots so that the plane appeared to all intents and purposes the same as before. Thus, MCAS was a technical solution to a commercial problem.

 

[Foo Fighter]

That would make it a technical solution to a technical problem, changing the behaviour of the aircraft artificially. Makes it a disaster in my book. The fact that they lied about it and failed to ensure passengewr/crew safety by telling people about it and then covering it up, badly, makes it criminal negligence on the part of the whole lot of them.

 

[TomcatViP]

Once again, pitch-up is inherent to swept wings. It's not something unique to the 737 MAX. It's old like the jet plane. Airbus has its own MCAS equivalent embedded with their FCS (one that have posed problem in the past and still does).

The geometry of the plane being different (more inertia coupling due to the frwd projected bigger engine, perhaps) the MCAS of 737 is just a patch to make the new model feel like the older one. It stiffens the ctrl input to prevent a pitch departure and add a secondary awareness element that is the slight pitch down behavior (like tapping the shoulder of someone falling in sleep behind the wheel).

If certifying a plane had not been such a nightmare, the tricking part of the MCAS would never have been by itself. Like I have written often, it's a big part too ofen chunk-out of the problem to forget that.

So, yes and no, this not only a commercial problem. It's systemic. Just like a tremor tells you about a seismic ridge.

We do not need more but better regulation.

So suggesting that MCAS should simply be discarded looks like simply negating the problem why Boeing was not able to build a fully coherent FCS for that specific model without the extra cost of a full recertification. At the age of an emerging AI, you would have taken for granted that Intelligence was not something only slumbering among manned agencies.