Boeing 737 Max8 Aircraft Crashes and Investigations [Part 5] 19

[Sparweb]

This is the continuation from:

thread815-445840
thread815-450258
thread815-452000
thread815-454283

This topic is broken into multiple threads due to the length to be scrolled, and images to load, creating long load times for some users and devices. If you are NEW to this discussion, please read the above threads prior to posting, to avoid rehashing old discussions.

Thank you everyone for your interest! I have learned a lot from the discussion, too.

Some key references:
Ethiopian CAA preliminary report

Indonesian National Transportation Safety Committee preliminary report

A Boeing 737 Technical Site

Washington Post: When Will Boeing 737 Max Fly Again and More Questions

No one believes the theory except the one who developed it. Everyone believes the experiment except the one who ran it.
STF

 

[Alistair_Heaton]

Unfortunately I will be at 25000ft when its on.

The NTSB hearing was on for the Southwest uncontained engine failure and explosive depressurisation accident last year.


As if the 737 design office doesn't have enough on its plate its now got issues with one of the engine types on the NG as well as the pickle forks.

Mind you in the current climate the FAA might just ignore the NTSB again.

https://www.seattletimes.com/busine...-retrofit-engine-casing-on-thousands-of-737s/

 

[LittleInch]

Well the documentary was a little underwhelming. Mainly a Human Interest angle and also one lawyer working for some of the families of the Ethiopian airline crash got a lot of air time. A few nice graphics ok and when you see the original "dumpy" 737 flying you realize just how many things have changed.

Rather simplistic explanation of MCAS.

Only interesting points were a recording of airline pilots in a meeting with Boeing after Lion Air, when they basically said nothing was wrong and the pilots should have followed trim runaway procedures....

An FAA retired employee saying the FAA knew from the start that lack of simulator training was an utterly key aspect to the design. Some were uneasy about this but no real smoking gun. The revision training has now gone to 2 hours, but what's a hour when you're flying a new plane??

They had a sim session where they showed the manual trim control was either very difficult / not possible on the ET flight hence in their words the ET pilots "rolled the dice", by reactivating the trim. They were working on the basis of a bird strike taking out the AOA vane, but no evidence other thaqn the very abrupt change in the AoA signal.

A passing mention of the 4 second pilot response and the level of cockpit alarms and actions going on meaning the pilots couldn't respond in the way it had been assumed. To that extent I don't think the very small AOA disagree light would have been noticed even if it was there (which it wasn't).

So for a forensic, detailed analysis of the 737max issues - this isn't it.

Update: the recent gulf air show seems to have prompted a lot of chatter. This from the FAA is interesting - end March is "more conservative".

https://gulfnews.com/business/aviation/no-timeline-for-return-of-boeing-737-max-faa-says-1.67958572

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[davefitz]

MCAS to be renamed HAL-9000 ?

"...when logic, and proportion, have fallen, sloppy dead..." Grace Slick

 

[moon161]

'I'm afraid I can't pull up Dave. You know as well as I do that would endanger the mission'

 

[VEBill]

“MCAS has to go,” a manager at Canada’s aviation regulator said in an email to global peers,

https://www.nytimes.com/2019/11/22/business/boeing-canada-737-max.html

 

[waross]

“MCAS has to go,” a manager at Canada’s aviation regulator said in an email to global peers,

Mr. Marko’s email included a PowerPoint presentation expanding on his argument and outlining how Boeing might remove MCAS from the Max. He noted that public confidence in the Max was “LOW.”

Linh Le, a system safety engineer at the F.A.A., shared Mr. Marko’s message with others at the agency. He noted that the Canadian official believed that “MCAS introduces catastrophic hazards that weren’t there before,” that “it and the fix add too much complexity,” that “there have been many revisions to the software” and that “each was a band-aid.”

Mr. Le said he had similar misgivings about Boeing’s proposed fix for the Max. “I have held similar perspective (questioning the need for MCAS, at least from the system safety standpoint),” he said in the email to colleagues. It is unclear whether international regulators will take any action in response to Mr. Marko’s concerns.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[Alistair_Heaton]

Here is the original email plus some of the PP slides.

https://theaircurrent.com/aviation-...-official-urges-removal-of-mcas-from-737-max/

As you can see from the article the MCAS stuff is the headline but there are several more issues in the works.

The way I see it now is the Certification Engineers are fighting back the media spin and getting there position public so they can't be accused of not saying anything, god forbid if another one spears in.

But if they just remove MCAS then it means they have removed a certification requirement that's been around for some 70 odd years just to save Boeings shareholders wallets....

 

[moon161]

This article about the DC-10 is about how weak certification oversight and making a 'safe enough plane' led to preventable crashes of the DC-10. So, in that way, no a new problem.

https://theaircurrent.com/historica...ons-for-boeing-in-the-grounding-of-the-dc-10/

 

[LittleInch]

I actually think there is a typo in his e-mail.

He wrote " No matter what Boeing does with MCAS it still won't be equivalent to a MAX [sic] because it has MCAS."

I think he meant won't be equivalent to an NG....

And therein lies the issue which Boeing simply can't get around after years of trying.

So if there is no MCAS, would it mean that the MAX wouldn't be allowed to operate above a certain AoA? What would happen if the stall warnings all went off at the point the controls started going light? From previous descriptions it looks like this is a bit less than 10 degrees, with stall at around 15 degrees.

Is it possible to fly the plane safely?

And it's not just Boeing who are in trouble here as noted previously. Several large airlines have bet their hat on this plane and are now in big trouble if it doesn't come back.

If the root cause is a hardware issue, then the change needs to be hardware also. So two trim motors? Larger elevators? Taller landing gear to move the engine backwards.

I suspect it's just too late to do most of those, but that's still where it might end up.



Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[Alistair_Heaton]

There are a few cases where we take the plane to near the stall on purpose and a couple when it does occur when its not meant to for some.

The main on purpose is a wind shear escape which is when the wind direction or strength or both changes virtually instantaneously. The momentum of the aircraft means it can take on the flying characteristics of a building brick.

The escape is to firewall the power which takes a few seconds to come online on big fan jets and pitch to the stick shaker, don't change the configuration, wings level and basically pray to which ever divinity is your preferred deity.

I have once in 16 years had to turn off the engine protection system Torque temp limiter (TTL) and basically accepted that I was going to destroy half a million worth of engines. Firewall with engine protection in limiting torque to 105% stick shaker going and still going down at 1500ft/min going through 700ft AGL. TTL system off engines giving 120% torque we escaped. Turns out I didn't destroy them You have to love Garrett engines, soap test every day for a week, then every week for a month and then give up. Lucky it was winter and the EGT was well below limits so no burnt turbine. Gear box was good for 150% torque apparently. If one of them had failed during it then we would have been dead with VMC rollover because there is no way the rudder had enough power at stall to control the aircraft one engine. Only way to escape VMC rollover is to reduce power on the live engine.


The main area where its likely to happen when it shouldn't is go-around. TOGA power and pitch up to climb, with less experienced pilots the engines take a while to spool up so they pitch to the go-around and then the engine pitch couple kicks in lifting the nose further. The pilot should compensate for this effect but it usually takes 2-3 sim sessions after qualifying on first jet type for it to become instinctive. I have this learning curve to look forward to when I move to jets.

 

[Sparweb]

Without a way to technically audit Mr. Marko's comments, I will put my confidence in them anyway, based on a number of other contacts I've had with him over the years. This is where I point out that I work in the aero engineering community in Canada, and interactions with Transport Canada are frequent - though not as frequent with the specialists in headquarters, like Mr. Marko. Having attended a couple of his presentations on the development and application of reliability guidebooks for systems analysis, I can't think of a more competent authority that I've met on the subject. As soon as the Max's were grounded, Mr. Marko became "unavailable" to all of us in the broader community as his attention became completely focused (among many others) on the Boeing issue. No matter how this turns out, I look forward to opportunities to hear Mr. Marko speak of his experience dealing with this problem. One of those "year of hell" stories that probably warrants a book deal.

http://www.sparweb.ca

 

[debodine]

Once again the Swiss cheese theory of holes has proven itself. I am sure readers may disagree on the weight of each factor, but when you line up these factors here (plus more of which I am yet unaware), the holes slowly line up. As usual, a series of poor choices is what lines them up. These are not in chronological order or order of importance, just a list for illustration.

The decision to use a critical flight control (stabilizer trim) for other than it's flight critical job of trimming the aircraft, but instead to divert it from its main task to a sub-task in a corner of the flight envelope.

Making the decision about using the trim because of a desire to NOT properly correct a fuselage design flaw with a fuselage correction (such as downward-angled strakes on the aft underside of the aircraft as one possible solution).

Believing that additional training in the flight characteristics was not required beyond a video, so as to avoid a market-limiting issue.

Tying the operation of a flight-critical control to a single sensor, with no cross-reference, no two out of three voting and not even any input smoothing to avoid the consequences of full scale spikes in the data stream.

Believing that the typical flight crew could notice, identify and correctly respond within 4 seconds to a system function failure that had never been practiced in a simulator.

Making all of the above poor choices, and then afterwards changing the control authority of the MCAS without re-addressing the issue with the FAA.

I recall reading years ago the book "On a Clear Day You Can See General Motors" by the now dead John Z. DeLorean. While he had his own share of flaws and foibles and I would not use him as either a managerial or lifestyle coach, I remember very clearly in his book his description of various high-level meetings about products. I am paraphrasing what I recall because I no longer have a copy of the book. As best as I recall, he concluded that a room full of smart, well-meaning people could collectively make a horrendous decision that not one of them would agree to or accept responsibility for if they alone were the decision-maker.

 

[waross]

Apart from the issues with the 737 Maxx, I wonder what regulatory changes and design changes we will see in the future.
Given the correlation between fan diameter and efficiency the trend may be to ever increasing engine diameter.
We may anticipate more control challenges as engine sizes increase.
MCAS was designed to comply with the regulatory requirement that the control forces must increase proportionally.
While MCAS may comply with the letter of the regulation I seriously doubt that it complies with the original intent of the regulation.
May we anticipate the following regulatory changes?
Rewriting of the regulatory requirement that the unassisted control forces must increase proportionally so as to limit the amount of automatic correction of control forces.
A limit on the maximum allowable movement and authority of the stabilizer, so that stabilizer movement may be overcome by elevator movement.
A re-evaluation of the grandfathering criteria.
A limit on the allowable amount of mis-trim caused by engine upthrust at high angles of attack, by engine thrust, and by engine location.
Will we see a trend to rear mounted engines such as the 727?

In September 1984, after a 22 year production run, the last 727 was delivered (a 727-200F to Federal Express). The once “very risky” 727 had become one of the greatest selling commercial jets in history.

I understand that larger engines were considered for the 727 but the issues with increasing the size of the center engine were economically unsolvable.
The third engine is no longer required for this class of aircraft.
I understand that mounting the engines in the plane of the center of gravity all but eliminates most engine induced trim issues.
Comments?

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[LittleInch]

Not a bad list, but I think

"Believing that additional training in the flight characteristics was not required beyond a video, so as to avoid a market-limiting issue."

Really should be
"Having a primary design constraint that additional training would not be required beyond a video, so as to avoid a market-limiting issue."
Also

Failing to tell pilots about this change from the NG,

Changing the cut out switches so that manual electric trim could not be maintained alone,

Failing to add even a simple AoA disagree warning light (not that I think this would have made much of a difference, but it didn't help)



Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[LittleInch]

waross,

I would hope that they pick up some of the issues identified by the NTSB with respect to overload of flight crew from multiple alarms and other issues caused by a single failure making it very difficult for the crew to determine the best course of action.



Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[debodine]

LittleInch, all good points to my post. Thanks for the comments!

 

[zeusfaber]

Failing to add even a simple AoA disagree warning light

If I've got this right, it wasn't they failed to add an AoA disagree warning light - they'd designed one in, but somehow failed to notice that it wasn't working on a majority of the jets they sold. Hard to blame that on groupthink.

A.

 

[IRstuff]

Failed in the sense that someone on the development team had a dot on their forehead to ensure that a design verification test would be performed.

TTFN (ta ta for now)
I can do absolutely anything. I'm an expert!

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[Comcokid]

Boeing experienced a fundamental change in company management culture beginning 20 years ago. I've been at smaller companies that had similar changes and the resulting impact in company culture. This recent article outlines the change at Boeing.

https://www.theatlantic.com/ideas/archive/2019/11/how-boeing-lost-its-bearings/602188/

 

[IRstuff]

I'm always a bit leery of Atlantic articles. While it's possibly true that McDonnell Douglas management won out in the end, what's missing from this narrative is that Boeing was making that fundamental change on its own. The McDonnell Douglas management could not have risen to ascendancy without being bought out by Boeing in the first place. And note that Boeing bought not only McDonnell Douglas, but also Rockwell, so Boeing management was already pushing the company into a non-engineering structure by the very act of buying two large companies.

TTFN (ta ta for now)
I can do absolutely anything. I'm an expert!

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