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-   -   B737MAX Recertification - Archive (https://www.flyertalk.com/forum/united-airlines-mileageplus/2031779-b737max-recertification-archive.html)

justatourist Apr 3, 2019 7:17 pm

So, being one of the few that actually saw Mentour's video referenced in the Leeham News article, here's a brief description of it. Please note this was done in a real 737 NG SIM with Mentour as the PF.
  • Not a take off simulation but it starts very low altitude and low speed, probably right after take off and in climb phase.
  • IAS disagree is simulated. Both pilots discuss and run through IAS disagree memory item checklist (auto pilots off, flight directs off, 4 degrees climb, auto throttle set to 75% N1).
  • MCAS is simulated (not sure how, if manually via yoke for this simulation purpose or if via SIM). The trim runs and Mentour comments he was expecting trim to run because speed is changing but at this point he is having flight control issues (plane going nose down). Both pilots discuss it, reach the conclusion it is a trim issue and quickly run the runaway trim checklist. At this point the column is already very heavy and you see Mentour putting a lot of effort in keeping the pitch. I think they mention the trim value to be 3 degrees in indicator right next to the trim wheels.
  • Speed is already very high. Co pilot tries to trim manually but cannot move the wheel more than a couple of turns, it is very very hard for him. And Mentour is already hugging the column (literally) to try and keep pitch. And The simulation ends here in a position where they cannot trim the aircraft back.

Some additional notes:

Mentour explained in the beginning what is so problematic about this particular scenario: the acceleration is always there. Even putting the plane in a 4º climb from the IAS disagree memory item checklist is not enough to nullify it, just to reduce it. And why so much emphasis on speed? Because at high speeds the forces on the stabilizer are so great that makes it almost impossible (or even impossible!) to manually trim the aircraft. Now in the middle of all this imagine MCAS kicking in any time pointing the nose down and gaining even more speed. And although there is a way to unload the stabilizer and trim the plane (doing the rollercoaster or yo-yo maneuver), being at low altitude kinda makes you not want to push the nose further down!

In short, if you are at low altitude and a IAS disagree happens, you might be in a position where even if you follow the recommended checklists and memory items, the plane is not recoverable (also detailed in the Leeham News article and in the SatGuru as well).

And it is a shame that the video is not available anymore, it clearly shows everyone that such scenario - that even knowledgeable pilots/instructors following procedures - really exists .

BF263533 Apr 3, 2019 8:12 pm


Originally Posted by mduell (Post 30961307)
Note the professor never actually says the MAX is unstable in pitch.

He makes a number of statements, that are all individually true:

Quote:Originally Posted by danielSuper [img]file:///C:\Users\Schul\AppData\Local\Temp\msohtmlclip1\01\ clip_image001.pngAccording to whom?

As R. John Hansman, a professor of aeronautics at the Massachusetts Institute of Technology, told me in a March 28 interview,As I understand it, at high angles of attack the Nacelles -- which are the tube shaped structures around the fans -- create aerodynamic lift. Because the engines are further forward, the lift tends to push the nose up -- causing the angle of attack to increase further. This reinforces itself and results in a pitch-up tendency which if not corrected can result in a stall. This is called an unstable or divergent condition. It should be noted that many high performance aircraft have this tendency but it is not acceptable in transport category aircraft [emphasis mine] where there is a requirement that the aircraft is stable and returns to a steady condition if no forces are applied to the controls.



He makes a number of statements, that are all individually true:

Quote:

As I understand it, at high angles of attack the Nacelles -- which are the tube shaped structures around the fans -- create aerodynamic lift.

This is true, and true for every 737 model back to the -100.

Quote:

Because the engines are further forward, the lift tends to push the nose up -- causing the angle of attack to increase further.

This is also true, and every 737 back to the -100 has had the inlet ahead of the wing leading edge.

No doubt the MAX, and the NG in some configurations, feel light in pitch. But no one, including your MIT professor, is actually claiming they're unstable. Less stable, but still positively stable.

After flying on the 737-200 for almost 15 years were you a little surprised the first time you stepped on the 737-300 and saw those much larger engines in front of the wing? The engine & nacelle on the 737-200 were long and thin and extended beyond both the front and rear of the wing. This differed from its contemporary wing mounted aircraft such as the 707, DC-8 & Convair 880, which had engines that were mounted well in front of the wing and did not extend to the rear of the wing like the 737. Google an image of the 737-200 with the JTD8 engine and compare it with an image of the 737 MAX with a Leap engine. The nacelle surface area of the JTD8 is much less than that of the Leap engine, and the Leap engine is mounted almost entirely in front of the wing. If the nacelles are creating lift at high angles of attack then the 737- MAX has a lot more nacelle surface area further forward compared to the 737-200’s JTD8. Some articles out there also discuss that the lift is being generated forward of the center of gravity.

The experts commenting on the 737 MAX are not conclusively stating that the MAX is unstable, but leaving conclusions on the MAX's stability to further investigation and testing. The investigation into MAX and its testing may well define what modern day aircraft stability should mean, and this would apply to Airbus also, whose accidents also raised stability concerns for me. See the referenced article that also discuses engine location and lift.

http://nymag.com/intelligencer/2019/...th-saving.html

spin88 Apr 3, 2019 8:23 pm


Originally Posted by PVDtoDEL (Post 30961799)
It's not that a system inhibits it, but rather that the force required is more than a human would realistically be able to apply.

More details: https://leehamnews.com/2019/04/03/et...as/#more-29790

Given that the ET crew had been trained on the new BA bulletin, I speculated above that something else was going on, not as certain folks want to assert "third world pilots." If true the "first world" management at Boeing is basically guilty of manslaughter. Faced with a crash that was the result of a serious design flaw, they failed to do what prudent engineers would do, and instead came out with some "blame the pilot" fix, that they then did not bother to check-out in the real world to see if it was rugged enough.

If this is true, that the procedure they sent out as a "fix" did not work, well then people ought to go to jail.

n198ua Apr 4, 2019 2:59 am

Ethiopian Airlines Stmnt on the Prelim Rpt of the Accident on ET 302
 

spin88 Apr 4, 2019 3:05 am

There appears to be confirmation that the ET crew - who we earlier knew were trained on the fraudulent Boeing "fix" - actually tried it. https://www.washingtonpost.com/world...=.a9926b71db4b

It did not work. It is one thing to put out a dodgy design, with a system put on for business reasons (MCAS) which overrides the pilots when a single sensor - with a long history of failure - failing. But it is quite another when that system kills 150+ people not to then do an honest and careful assessment, and instead put out a procedure thet when followed does not fix the situation. That is criminally negligent. Did Boeing in its haste to blame the Lion Air pilots, and deflect blame from its negligent design work just not test its procedure? See if it actually worked?

It was possible, although hard to believe, that the ET pilots failed to follow BA's written instruction on how to deal with a MCAS problem. But now we know that the ET pilots did follow the process, I don't see how anyone can fault them. Working with an aircraft that had a MCAS induced issue at 1000 feet, they followed BA's written safety bulletin and it did no good. This crash was 110% Boeing's fault if the ET pilots followed BA's written safety instructions. Really a sinister cast to Boeing's actions at this point.

Given this information showing the fix was not really a fix, I question why anyone would trust Boeing or the FAA at this point on anything. This is IMHO the worst possible outcome for Boeing. Not only did their design flaws/business decisions cause the first crash, they failed to adequately address the issue when putting out written safety instructions after the first crash, leading to a second crash.

So who wants to trust Boeing that the "new" fix on the MAX works? Who trusts them on the 777x? Who trusts them on anything?

n198ua Apr 4, 2019 3:07 am

"....despite their hard work and full compliance with the emergency procedures, [sic], they could not recover the airplane from the persistence of nose diving."

The statement also says that both pilots followed Boeings and the FAA's emergency procedures to "handle the most difficult emergency situation created on the airplane."

spin88 Apr 4, 2019 3:19 am


Originally Posted by n198ua (Post 30963349)
"....despite their hard work and full compliance with the emergency procedures, [sic], they could not recover the airplane from the persistence of nose diving."

The statement also says that both pilots followed Boeings and the FAA's emergency procedures to "handle the most difficult emergency situation created on the airplane."

I am sure that had the superior/exceptional AMERICAN pilots followed Boeing and the FAA's emergency procedure at 1000 feet it would have worked out just fine. /snark/. The problem is these poorly trained 3rd world pilots as we all know. /snark/ Move on, nothing to see, we all know that AMERICAN engineering and corporate management is just the best, "if it is not Boeing, I ain't going". /snark/

moondog Apr 4, 2019 3:57 am


Originally Posted by spin88 (Post 30963372)
I am sure that had the superior/exceptional AMERICAN pilots followed Boeing and the FAA's emergency procedure at 1000 feet it would have worked out just fine. /snark/. The problem is these poorly trained 3rd world pilots as we all know. /snark/ Move on, nothing to see, we all know that AMERICAN engineering and corporate management is just the best, "if it is not Boeing, I ain't going". /snark/

I have talked with my pilot friends at Delta, United, and Cathay Pacific about the 737 Max incidents, and all have told me the same thing:
1. They don't think highly of Asian LCC pilots
2. But, flying 737s is not rocket science
3. They would have also panicked if their planes decided to nose down (on their own) at 3,000 feet

spin88 Apr 4, 2019 4:14 am


Originally Posted by moondog (Post 30963436)
I have talked with my pilot friends at Delta, United, and Cathay Pacific about the 737 Max incidents, and all have told me the same thing:
1. They don't think highly of Asian LCC pilots
2. But, flying 737s is not rocket science
3. They would have also panicked if their planes decided to nose down (on their own) at 3,000 feet

As I noted up-thread, I talked to an AA pilot (who flies the A320) and he said that his 737 co-workers were very concerned. Two approaches, one is "there but by the grace of god go I" the other is "I know all, I would have fixed the issue". The reality is that it is very hard at 1000 feet, and the design put out by Boeing was just deadly. When the Boeing recommended procedure turned out to be a fraud or not tested or itself defective (pick your guess) and you are at 1000 feet, going really fast into the Ground, not a lot of options.

And I might add, that there is a big difference between Asian LLC pilots, and - despite aspersions on them - ET's pilots who are well trained.

username Apr 4, 2019 6:42 am

I think pilots from bigger countries like US and Canada are probably better because many of them start flying at a younger age than pilots from most other countries because of geography necessity and easier access. However, I also think Boeing exploited Lion Air's history / reputation to protect itself rather than getting to the bottom of things and come clean fast.

https://www.nytimes.com/2019/04/02/w...-lion-air.html is another interesting article. This probably also explains why ET sent the black boxes to France.

Now the spins such as https://boeing.mediaroom.com/2019-03...tion-Community after the ET crash make them look like big liars. Did he not know what was going on or still hope to cover things up?

I hope the truths come out from the investigations and lawsuits. Let us all - business people, engineers, PR people, government - learn from this lesson of ethics/integrity/trust, engineering, government's role in regulations, etc.

Aussienarelle Apr 4, 2019 8:18 am


Originally Posted by username (Post 30963735)
...I hope the truths come out from the investigations and lawsuits. Let us all - business people, engineers, PR people, government - learn from this lesson of ethics/integrity/trust, engineering, government's role in regulations, etc.

I am hoping that this is the start of a swing back to government agencies protecting the people.

It seems to me too many government agencies are pandering to the businesses that lobby to make it easier for business without necessary protections and line the pockets of elected officials.

We the people are the government, we the people elect the officials to run the nation, state, county, city, etc. to run those places on our behalf and yet it appears the moneyed interests are the ones looked after.

Businesses are there to make money for shareholders. I am a capitalist at heart and endorse this approach.

Governments and their agencies are supposed to be the protection for their constituents and put rules in place and administer those rules to protect the people (not pander to the interests of business). If governments and the agencies do not protect the public interests who will?

Sorry it took the deaths of people but do hope those deaths result in changes in the way the FAA and other government agencies conduct themselves and their accountability to the people.

ExplorerWannabe Apr 4, 2019 8:20 am

Nothing in today's report that we didn't know yesterday and again ... WHY WAS THE PLANE NOSEDIVING?

The reports are that it kept nosediving even with MCAS turned off so it's not the software. The engineering analysis quoted earlier indicated qualities that are contrapositive to nosediving early in flight so what caused the nosediving in the first place and kept it going while the electrics (including MCAS) were turned off?
I am sure that unexlained nosediving with only 1000 feet altitude would cause panic. That's not a lot of time or altitude to come up with a solution. On the other hand, the charges that the design is deadly, that Boeing or employees are guilty of criminal conduct just are not supported by the evidence released so far. The basic 737 design and construction has been well-proven with tens of thousands of flights. The design qualities in the MAX that reportedly prompted the MCAS software should actually have mitigated this scenario when MCAS was turned off so what happened? Is it a different design defect in the aircraft? Perhaps Boeing did something else wrong in the design or construction and the furor about MCAS is hiding it. Was there an overlooked maintenance issue? (yes, I know Ethiopia brandished the recent certificate but the fact remains that very aircraft had a similar incident recently and IIRC there were other reported maintenance issues on it). Was there something else wrong in the launch configuration?

worldclubber Apr 4, 2019 8:38 am


Originally Posted by username (Post 30963735)
I think pilots from bigger countries like US and Canada are probably better because many of them start flying at a younger age than pilots from most other countries because of geography necessity and easier access. However, I also think Boeing exploited Lion Air's history / reputation to protect itself rather than getting to the bottom of things and come clean fast.

I fully agree on your last sentence: It was not the smartest move to solely blame the Lion Air pilots, rule out failure on the part of Boeing and neglect the potential learning process. Additionally, it was economically and culturally very insensitive, as Lion Air is one of the largest 737 customers in the world and Boeing will cry like a baby when they lose orders in the region as result of all this.

Concerning your first sentence: Are pilots from a developed country, who grow up flying technologically up-to-date and well-maintained planes in a well-organized airspace necessarily better pilots than pilots who learn to fly and survive under much less ideal conditions? Depends on the definition of better I guess.

DenverBrian Apr 4, 2019 8:54 am


Originally Posted by ExplorerWannabe (Post 30964002)
Nothing in today's report that we didn't know yesterday and again ... WHY WAS THE PLANE NOSEDIVING?

And until we have a definitive answer, MAXes must stay grounded.


The basic 737 design and construction has been well-proven with tens of thousands of flights.
Increasingly, I believe many people are coming to the conclusion that the MAX is NOT a "basic" 737 design and in fact is so changed from the "basic" or even NG design that it probably needs its own type certification before it flies.

EWR764 Apr 4, 2019 9:51 am

As the case has evolved, a major issue appears to be the fact that the MCAS has full authority over the horizontal stabilizer. A fully nose-down trimmed stabilizer will effectively negate the elevator control given that the stab is about 4x the surface area of the elevators. The physics are pretty straightforward. It appears the ET crew eventually, correctly recognized an MCAS runaway, acted appropriately and in accordance with their training, but the MCAS rolled in so much nose-down trim they either weren't able to manually reverse, it or ran out of time (altitude).

What this says is, to avoid catastrophe in the event of an uncommanded MCAS activation, the pilot must be able to recognize the anomaly immediately and cut out the automatic trim before it rolls in too much nose down, because (as noted in a post above from the sim demonstration) aerodynamic forces in the climb phase make it physically demanding to manually re-trim back to nose up with the wheel. If the nose-down trim is at the stops, it may well be impossible to recover, especially at low altitude. I have faith in well-trained pilots, but that's an awful lot to put on the two people at the pointy end, especially when a single point of failure theoretically delivers you to that do-or-die moment in a hurry.

This is a problem, and while it likely will be overcome by software and perhaps mechanical fixes (like dozens of systems working safely on all modern airliners to counteract aerodynamic consequences of certain designs), it's not looking like the MAX will return to service very quickly.


Originally Posted by ExplorerWannabe (Post 30964002)
Nothing in today's report that we didn't know yesterday and again ... WHY WAS THE PLANE NOSEDIVING?

The bits of information that are coming out regarding the ET crash are related back to the same issues. If anything, it serves to more narrowly focus the inquiry on what exactly was the culprit.


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