Boeing 737 Max8 Aircraft Crashes and Investigations [Part 6] 17

[Sparweb]

This post is the continuation from this series of previous threads:

thread815-445840
thread815-450258
thread815-452000
thread815-454283
thread815-457125

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

BBC: Boeing to temporarily halt 737 Max production in January

 

[LittleInch]

Well it's come to a bit of a halt over the Christmas and New Year break, but I don't think any of us here really have a clue what Boeing is going to do to sort out their $100 billion dollar mess.

The software route is where they were definitely going but that seems to have hit a few road blocks and appears to be in the grey zone between manual flying and FBW regulations and certification.

I think they will have to do some sort of wiring / switches modifications to allow the MCAS part to be isolated if required but still allow electric thumb control of the elevator. A purely software driven system runs into the issue of only having two sensors ( not three) and only two FCCs. There's just no way around it - doing a FBW with the current hardware just won't wash (I believe). Their previous attempt to do a partial FBW is how we got here in the first place.

So they will need to add something else that is relatively easy to do and doesn't change too much.

The flaps ideas, longer undercarriage etc would take too long, but is probably the best engineering solution.

Also the chances of not requiring simulator training, at least outside the US, is not high.

Interesting year ahead!

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

 

[VEBill]

"...some sort of wiring / switches modifications to allow the MCAS part to be isolated if required but still allow electric thumb control of the elevator."

Amen. That'd move the whole issue towards 'Minor'.

 

[Alistair_Heaton]

There is a financial statement due middle of Jan. Which should have some details.

Seems BA are not going to let the current relationship change.

https://www.flightglobal.com/news/b...-auxiliary-tank-explosion-risk/135973.article

Btw this system has been changed across many types and OEMs.

 

[Eufalconimorph]

There's apparently a wiring issue with the MAX.

https://www.reuters.com/article/us-...iring-issue-on-grounded-737-max-idUSKBN1Z40U9

> The FAA flagged the wiring issue as potentially “catastrophic.” It is possible other protections like shielding, insulation and circuit breakers could prevent the short circuit, a company official said.

 

[thebard3]

An excerpt from that article-
"The crisis has cost Boeing $9 billion..."
...so far. I'm sure that's a pretty small percentage of what the total cost will eventually be.

Brad Waybright

It's all okay as long as it's okay.

 

[Alistair_Heaton]

hell if they have to go back in and change wiring looms in all the aircraft already produced....


That's a full check level of strip down to get at them.

Even if they do get to fly it in March which is doubtful they will have extremely few of them flying for the summer season.

edited to add its only 1 bracket that's causing an issue and its easy to get at in the tail. So its more headline grabbing that Boeing has made a statement about it than there is an actual issue.

The other strong rumour is sim training will be mandated by the FAA for the max. They are now trying to figure out a software change for NG sims because MAX sims still are relatively rare. Plus the electric actuated sims apparently cant produce enough power on the yoke or the trim wheel to simulate a max out of trim.

 

[waross]

Plus the electric actuated sims apparently cant produce enough power on the yoke or the trim wheel to simulate a max out of trim.

Or for an NG out of trim?
I understood that the early videos of pilots fighting the trim wheels in simulators were done in NG sims with full stabilizer travel to mimic the MAX 8 issues. Is this correct?

A thought. Originally, when the intent was to avoid at all cost any hint of simulator training, the control forces at the yoke had to be the same as in the NG.
If there is going to be simulator training, it may not have to feel exactly the same as an NG.
In that case the issue of excess force on the yoke may be resolved by reducing the force generator output to 75% or 50% of what it is now.
That leads to the question;
Does the elevator have enough authority to counteract full nose down stabilizer trim?
I had assumed that simulators used the same force generator as was used in the planes.
I guess that one shouldn't ass u me.
I am surprised that the sims don't use the same force generator as is used in the aircraft.
Probably because of Boeing pricing.

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

 

[Alistair_Heaton]

It is a Ng SIM you see them fighting with.

Apparently the force you can fight against and over power with an electro actuated sim.

The force is less than real world.

Remember the 737 is cables. Full stab and Vmo any movement in the yoke is likely to be cable stretch.



The old hydraulic Sims you wouldn't be able to overpower.

I don't have a clue if the elevator could counter act the stab. Or for that matter if the hinges could handle it.

Problem is that without mcas the flight envelope is uncertifiable. So a single failure then dump it on the crew is not an option. You would need another layer of protection before dumping it on the crew.

3 AoA sensors would give you that extra layer. But then your into FBW certification rules..

 

[Lou Scannon]

737 reminds me a bit of Ford's Model T, except unlike Ford Boeing apparently didn't know when to push it off a cliff and start with a clean sheet of paper, which Ford eventually did with the Model A.

"Schiefgehen wird, was schiefgehen kann" - das Murphygesetz

 

[waross]

Two incidents from my late teens;
A friend had a '32 ford coupe.
He installed a Packard engine in car.
This was a very heavy straight six or eight, much heavier than the original engine.
His first test drive, he took a corner fast.
He could have made it in most cars but the added front end weight compromized the handling and he totalled the car on the first test run.
About the same time our shop teacher replaced the very small 4 cylinder engine in his Morris Minor with a flat head Ford V-8
Another school acquaintance badly wanted the car.
The teacher was moving away about 100 miles but promised to keep the car over the summer to let the student have time to earn the money.
The student worked hard all summer and saved every dime he made.
At the end of summer he took his money and bought the car.
Same issue.
An inappropriate engine compromised the handling of the car.
He totaled the car on the way home.

It feels as if Boeing pushed a 50 year old design as far as it could go, taking advantage of grandfathering privileges.
After that they built the MAX-8.
The handling is compromised by inappropriate engines.
And lest we forget:

A manager at Canada’s aviation regulator believes that Boeing should remove software that played a role in two deadly crashes of its 737 Max before the plane is cleared to fly again, according to emails between global aviation regulators this week that were reviewed by The New York Times.

The Max has been grounded since March, days after a crash in Ethiopia. Together, the two accidents killed 346 people and have sent Boeing into a crisis. The company is working furiously to get the Max back in service with a fix to the software system, known as MCAS.

“The only way I see moving forward at this point, is that MCAS has to go,” the official, Jim Marko, the manager in aircraft integration and safety assessment at Transport Canada Civil Aviation, wrote in the email. He sent the email on Tuesday to officials at the Federal Aviation Administration, the European Union Aviation Safety Agency and Brazil’s National Civil Aviation Agency.

At least one F.A.A. employee shares his concerns, according to a separate email reviewed by The Times.

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.

In his email, Mr. Marko said he was writing the other regulators because he wanted “to get some confidence back to us all that we as Authorities can sleep at night when that day comes when the MAX returns to service.”

He expressed concern that regulators might accept the update to MCAS even as issues with the fix kept cropping up. “This leaves me with a level of uneasiness that I cannot sit idly by and watch it pass by,” Mr. Marko wrote.

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

 

[LittleInch]

"Does the elevator have enough authority to counteract full nose down stabilizer trim?"

Not as I understand it which is why the two planes crashed with both pilots exerting maximum force pulling the stick back.

Back in the threads there was a good explanation of this, with the sheer size of the stabiliser dwarfing the elevator cross sectional area, something which has got more out of kilter as the planes have got bigger and bigger.

Also I don't think changing the "feel" of the controls would make any difference. They just work by modifying the force . The problem / issue is that the reaction force on the elevator decreases at high levels of attack which is contrary to the certification requirements, hence why MCAS was used to replicate this.

What Boeing (and maybe the FAA) have discovered I think is that there is no such thing as a part FBW design. It's either based on manual forces and assist systems or it's FBW. There is no in between, especially for a design that is 50 years old with computers based on 1980's technology.

To get this plane back flying worldwide I believe will need some hardware mods of some sort, whether wiring, trim motor design or something more fundamental with the engine nacelles.

But what do I know??


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

 

[Eufalconimorph]

Bloomberg (I know, not a trustworthy news source) is reporting that "Boeing is recommending that airlines put pilots through simulator training before they fly the 737 Max"

https://www.bloomberg.com/news/arti...elf-to-back-simulator-training-for-max-pilots

That makes me far more confident in the MAX flying. It means the pilots will be trained to recognize MCAS and to fly with it disabled. It's still a weird hybrid FBW/manual system dependent on only 2 sensors instead of 3, with underpowered computers, and an anemic manual trim system, but it's probably safe enough to get certified by the FAA.

 

[human909]

On face value this is a MASSIVE back down from Boeing. And it will cost Boeing dearly.

On of the key selling points of the MAX was that it need minimal additional training. If significant additional training is needed this will likely be at Boeing's expense. Though all this is subject to discussions and negotiations with Boeing's customers. This decision wouldn't have been taken lightly. But if it is a necessary requirement to get the MAX in safely the air it is then it better than leaving it grounded.

Boeing will continue to haemorrhage money on this. But with an updated MAX and better training they can hopefully meet safety requirements and get back into the business of building and selling aircraft.

 

[JohnRBaker]

Bloomberg...is reporting that "Boeing is recommending that airlines put pilots through simulator training before they fly the 737 Max

The problem is that there are only 34 737 MAX simulators in operation around the world, and yet there are more than 1,000 pilots who would need to complete a training cycle in a simulator.

John R. Baker, P.E. (ret)
EX-Product 'Evangelist'
Irvine, CA
Siemens PLM:
UG/NX Museum:

The secret of life is not finding someone to live with
It's finding someone you can't live without

 

[LittleInch]

Well they had to do something to move forward and if true this might be enough, but the fix still needs to be approved. Whether software on its own will cut it will be intereating to see.

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

 

[VEBill]

Same news item.

https://www.cbc.ca/news/business/boeing-737-max-simulator-training-pilots-1.5418103

From The Associated Press, so likely not incorrect.

 

[Alistair_Heaton]

I think they have been told they have zero chance of it returning with just iPad training.

So they might as well recommend it so the public think they have seen the light and have new ethos about safety.


Nothing has changed though. It's just more MBA's trying to climb the ladder as the top deck gets cleared out.

 

[Eufalconimorph]

Yeah, we were all pretty sure training would be needed no matter what. Boeing sticking to the "no training" plan wasn't going to be able to last forever. The only thing that's changed is the acknowledgement of it by Boeing (instead of just some non-US regulators), which mostly only matters to stockholders.

 

[waross]

The problem is that there are only 34 737 MAX simulators in operation around the world, and yet there are more than 1,000 pilots who would need to complete a training cycle in a simulator.

Quite a few more than 1,000 Pilots, or did CBC slip a decimal point?

Boeing even offered to pay Southwest Airlines a rebate of $1 million US per plane if the airline had to train its nearly 10,000 pilots in simulators before they could fly the Max.

There were reports that the MAX simulators did not properly simulate a MAX 8.
Has that been sorted out?
Can an NG hydraulic simulator be reprogrammed to simulate a MAX?
If a flood of new simulators are put into use, will there be an issue training simulator operators?

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