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# Boeing 737 Max8 Aircraft Crashes and Investigations [Part 6]15

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

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

thread815-445840: Boeing 737 Max8 Aircraft Crashes and Investigations [Part 1]
thread815-450258: Boeing 737 Max8 Aircraft Crashes and Investigations [Part 2]
thread815-452000: Boeing 737 Max8 Aircraft Crashes and Investigations [Part 3]
thread815-454283: Boeing 737 Max8 Aircraft Crashes and Investigations [Part 4]
thread815-457125: Boeing 737 Max8 Aircraft Crashes and Investigations [Part 5]

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

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. ### RE: Boeing 737 Max8 Aircraft Crashes and Investigations [Part 6] "...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'. ### RE: Boeing 737 Max8 Aircraft Crashes and Investigations [Part 6] 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/boeing-clashes-w... Btw this system has been changed across many types and OEMs. ### RE: Boeing 737 Max8 Aircraft Crashes and Investigations [Part 6] There's apparently a wiring issue with the MAX. https://www.reuters.com/article/us-boeing-737max-s... > 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. ### RE: Boeing 737 Max8 Aircraft Crashes and Investigations [Part 6] 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.

### RE: Boeing 737 Max8 Aircraft Crashes and Investigations [Part 6]

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.

### RE: Boeing 737 Max8 Aircraft Crashes and Investigations [Part 6]

#### Quote:

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

### RE: Boeing 737 Max8 Aircraft Crashes and Investigations [Part 6]

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..

### RE: Boeing 737 Max8 Aircraft Crashes and Investigations [Part 6]

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

### RE: Boeing 737 Max8 Aircraft Crashes and Investigations [Part 6]

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:

#### Quote (The New York Times, Nov 22, 2019)

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

### RE: Boeing 737 Max8 Aircraft Crashes and Investigations [Part 6]

"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.

### RE: Boeing 737 Max8 Aircraft Crashes and Investigations [Part 6]

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/articles/2020-01-07...

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.

### RE: Boeing 737 Max8 Aircraft Crashes and Investigations [Part 6]

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.

### RE: Boeing 737 Max8 Aircraft Crashes and Investigations [Part 6]

#### Quote (Eufalconimorph)

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

### RE: Boeing 737 Max8 Aircraft Crashes and Investigations [Part 6]

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.

### RE: Boeing 737 Max8 Aircraft Crashes and Investigations [Part 6]

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.

### RE: Boeing 737 Max8 Aircraft Crashes and Investigations [Part 6]

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.

### RE: Boeing 737 Max8 Aircraft Crashes and Investigations [Part 6]

#### Quote:

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 ### RE: Boeing 737 Max8 Aircraft Crashes and Investigations [Part 6] I don't think there are hydraulic Ng Sims. Cae have been producing electro actuated Sims since before the Ng was certified. The older classic 737 Sims are hydraulic. Apart from anything else I don't think there will be a flight model for macas turned off which they will need. And if they do produce one it will allow people to test the envelope and see what's really wrong with it. Sims are run by pilots mostly. It's relatively simple to set one up for a training serial. SIM technicians is a different matter. But they tend to have 2-3 of them for a sim hall which can have 10 to 20 of them running 24h ### RE: Boeing 737 Max8 Aircraft Crashes and Investigations [Part 6] And we find out the reason why Boeing now supports the training in simulators. https://www.bbc.com/news/business-51058929?SThisFB... #### Quote (bbc) "One unnamed employee wrote in an exchange of instant messages in April 2017: "This airplane is designed by clowns who in turn are supervised by monkeys." https://www.scribd.com/document/442346616/Boeing-E...? https://www.scribd.com/document/442346573/Boeing-E...? https://www.scribd.com/document/442346585/Boeing-E...? If there weren't so many people killed these would be funny. ### RE: Boeing 737 Max8 Aircraft Crashes and Investigations [Part 6] The floodgates opened this morning. Boeing is deservedly being publicly wire-brushed. They have a big hole to dig themselves out of now. https://www.nytimes.com/2020/01/09/business/boeing... Brad Waybright It's all okay as long as it's okay. ### RE: Boeing 737 Max8 Aircraft Crashes and Investigations [Part 6] #### Quote (BBC) One unnamed employee wrote...: "This airplane is designed by clowns who in turn are supervised by monkeys." They mention disciplining staff... Who? The unnamed employee(s), the clowns, or the monkeys? ### RE: Boeing 737 Max8 Aircraft Crashes and Investigations [Part 6] Apparently a new court case is brewing.... The Clowns union is not happy..... And as for the monkeys best not talk about what they are going to do.... ### RE: Boeing 737 Max8 Aircraft Crashes and Investigations [Part 6] #### Quote (VEBill) They mention disciplining staff... Who? The unnamed employee(s), the clowns, or the monkeys? #### Quote (Part of Boeing's statement) “The language used in these communications, and some of the sentiments they express, are inconsistent with Boeing values, and the company is taking appropriate action in response. This will ultimately include disciplinary or other personnel action, once the necessary reviews are completed.” Taking actions against the unnamed employee(s). ### RE: Boeing 737 Max8 Aircraft Crashes and Investigations [Part 6] From the perspective of a somewhat informed flying public. Trust or lack thereof. Do you, as a member of the general somewhat informed flying public want to avoid flying on the MAX-8? How do you avoid flying on the MAX 8? What about re-branding? Are there any plans to re-brand the MAX 8? #### Quote (The Guardian) Plenty of observers – among them Donald Trump – have advised Boeing to rebrand the plane before its eventual return to service. The US president tweeted in April: “If I were Boeing, I would FIX the Boeing 737 MAX, add some additional great features, & REBRAND the plane with a new name.” Boeing 737 Max ordered by Ryanair undergoes name change And the trust level falls further. I won't say that I will never fly Boeing or specifically a 737, but avoidance will be diligent. As long as Boeing persists in trying to address uncertifiable flight characteristics with software patches, "If it's Boeing, I'm not going." Public avoidance may add additional losses in the future. Bill -------------------- "Why not the best?" Jimmy Carter ### RE: Boeing 737 Max8 Aircraft Crashes and Investigations [Part 6] #### Quote (waross) Do you, as a member of the general somewhat informed flying public want to avoid flying on the MAX-8? A few weeks ago I could have offered a simpler, more definitive answer-- NO(I would not avoid it)! Today, I'm not sure. I thought they would have had this figured out by now and the 737 MAX could take it's place as it's iteration in one of the safest and most successful line of passenger jets of all time. Brad Waybright It's all okay as long as it's okay. ### RE: Boeing 737 Max8 Aircraft Crashes and Investigations [Part 6] "As long as Boeing persists in trying to address uncertifiable flight characteristics with software patches, "If it's Boeing, I'm not going."" I guess you'll be avoiding fly by wire planes too then? ### RE: Boeing 737 Max8 Aircraft Crashes and Investigations [Part 6] FBW planes may have dodgy flight envelopes, to be honest I don't know if they do or don't I presume some of them do. Its the fact you have to go down 4 if not 5 failure levels before the pilots have to deal with said dodgy dynamics. And all the computers and systems are certified to a much much higher level. Which means the chances of the pilots ever seeing it in their lifetimes is less than winning euro millions. Airbus does have a final law which means basically everything is off line. You can still fly the machine straight and level but you can't land it in that mode. Its only there so all the computers can reboot. And to my knowledge since the Airbus FBW system has been out there over all the types its been fitted to, nobody in the real world has been in it out side the simulator. yes there have been crashes the AF477 being the perfect example. But that was purely pilot error completely disregarding the emergency procedures and pulling back on the stick all the way into the sea. There was a heap of factors leading up to this point which could have stopped it before it happened. And this was a first world nation national carrier crew. In fact if the crew had let go of the controls they might have survived. Max 8 with its Frankenstein FBW fixes, you have one single failure and everything is dumped on the pilot to fly the thing in the uncertifiable envelope. And that goes for the fix as well. Which happened twice in the space of a year. If the crew let go of the controls the aircraft would have just put them into the ground faster. I won't be going in one either unless there is a drastic change in the design of the flight control system. Eg they move Mcas to an input to the elevator instead of the stab. At least then they can overpower it using the stab if it goes crazy. Even putting 3 AoA sensors in only gives you 2 layers of protection. BTW they know who everyone is in these conversations. They are not releasing their names because several people so far who have been named have received death threats. There are also several people on the design teams who's mental health is extremely delicate just now with a few that have tried to commit suicide. Nobody else deserves to die over this stupidity. ### RE: Boeing 737 Max8 Aircraft Crashes and Investigations [Part 6] #### Quote (waross) Do you, as a member of the general somewhat informed flying public want to avoid flying on the MAX-8? Of course. It's a twitchy inbred pit bull that's killed two of its previous handlers. I don't care what muzzle they put on it. ### RE: Boeing 737 Max8 Aircraft Crashes and Investigations [Part 6] New report out. Its causing a bit of indignation in some circles. But to be honest I can't see anything wrong with the key findings and recommendations. There is some sections that just ooze management bullshite bingo talk and trying to stop the clock being rolled back wasting years and millions of dollars of lobbying to get the current situation. https://www.transportation.gov/sites/dot.gov/files... But if they insist on this delegation structure as it is now I can't see anyone else accepting FAA certification. So the machines are going to be certified anyway by the other authorities independently of the FAA. And STC's will only be valid on N reg. ### RE: Boeing 737 Max8 Aircraft Crashes and Investigations [Part 6] That doesn't seem like it'll restore any faith from the international community in the FAA. ### RE: Boeing 737 Max8 Aircraft Crashes and Investigations [Part 6] #### Quote (Special committee report) In nearly all its interviews, the Committee asked a wide range of stakeholders the same two questions: “If Boeing had applied for a new type certificate for the 737 MAX 8, would it have made a difference to the level of scrutiny of the aircraft during certification?” and “Would seeking certification via a new TC have produced a safer aircraft?” The answer from the experts was consistent; each said a new TC would not have produced more rigorous scrutiny of the 737 MAX 8 and would not have produced a safer airplane. Seeking certification via a new TC would have required all of the 737 MAX 8 to be certified again—including those parts and systems now in use in the 737-800 that were previously certified and remained unchanged and unaffected by changes. However, the Committee concluded that additional consideration of the interface between the changed item and the rest of the system, as well and the impact of multiple changes over time, should be required. This includes assessment of their combined effect on the flight crew’s ability to safely manage operational tasks. This for me misses the issue. An unsafe aircraft was made because they stretched the 737 design unreasonably to certify and train on an ammendment instead of new type basis. ### RE: Boeing 737 Max8 Aircraft Crashes and Investigations [Part 6] Tomfh... "Of course. It's a twitchy inbred pit bull that's killed two of its previous handlers. I don't care what muzzle they put on it." I'm thinking 30-06... Dik ### RE: Boeing 737 Max8 Aircraft Crashes and Investigations [Part 6] FAA and funding. At present: Boeing hires and pays the inspectors. Why not: FAA hires and pays the inspectors, and charges Boeing for the expenses? The big expense may not be so much added administration costs as the added cost of doing it right. I can't accept the premise that short funding of the FAA is to blame. Now, Boeing is paying the inspectors directly. They could just as well be paying the inspectors indirectly through FAA billing. How much percentage difference to the cost of a 737 would be incurred if the FAA hired the inspectors and billed Boeing for the inspections? Is this another case of The Boeing System? (BS) Bill -------------------- "Why not the best?" Jimmy Carter ### RE: Boeing 737 Max8 Aircraft Crashes and Investigations [Part 6] What you describe (FAA hiring/paying inspectors) was how they operated until relatively recently. I believe the rationale was ultimately agency budget cuts. They assume(hope?) that the Boeing hired/paid inspector will remain impartial and not be beholden to Boeing. I believe there's even records that Boeing fired/reassigned previous inspectors on the Max project when they started making trouble? I remember seeing that in one of the previous threads. ### RE: Boeing 737 Max8 Aircraft Crashes and Investigations [Part 6] Has there been a serious investigation of how a faulty AoA sensor was allowed out of the FAA approved repair facility and the apparently faulty test procedures that were FAA approved? The FAA seems to have covered that up quite well. Another blow to the credibility of the FAA. Bill -------------------- "Why not the best?" Jimmy Carter ### RE: Boeing 737 Max8 Aircraft Crashes and Investigations [Part 6] (OP) Slow down... How much more do you want your taxes to go up? How slow do you want developments in technology, and delays in aircraft operations? That's how aviation USED to be. Ask anyone if they want safer airplanes, they'll say "yes" every time. Ask people if they want to pay more in taxes, they'll say "no" every time (almost). Every time somebody says "the guvvermint should do that!" I hear money whooshing out of my pocket. Before you suggest that the FAA should employ all the inspectors to keep the companies at bay, just ask yourself how much that would cost, and what it would accomplish. Same goes for Canada, Europe, and the rest of the world; we all use the licensing and delegation system to assign authority and accountability where it can be supported by people in direct contact with the equipment and skills needed to be effective. You do want the most effective people to be solving problems, right? I'm not ignoring your point that the system was abused, and that people knew that they could push beyond the acceptable limits of the system of accountability. That's bad. But if one firefighter is caught starting a fire, you don't condemn all firefighters. It does also degrade the credibility of the FAA, but not really because the FAA let faulty parts for a faulty plane through. It's because they gave credit to people at a company that couldn't act with the level of integrity that they were supposed to, or agreed to when receiving their credentials from the FAA. Which allowed the companies to ignore their own rules and principles. The FAA is supposed to monitor compliance, but they certainly failed in this case. Budget cuts played a role in that. In the past decade, the FAA (like many other parts of the US government administration) have been shut down many times. There's a broader story about the value of the public service that keeps all the details of a country running, and what goes wrong when they can't do their jobs... perhaps for another time. ### RE: Boeing 737 Max8 Aircraft Crashes and Investigations [Part 6] So the parent agency of the FAA, The Department of Transportation, has produced a political document. #### Quote: In April of 2019, U.S. Secretary of Transportation,Elaine L. Chao,created the Special Committee to Review the Federal Aviation Administration’s Aircraft Certification Process (the Committee). Cover Your ASSets bafflalgab. This is not so much an impartial investigation as a statement of defense of the FAA and the any responsibility of the Department of Transportation for a lack of effective oversight. I don't think that this report will do anything to bolster the international reputation of the FAA. #### Quote: "346 people died. And yet, Dennis Muilenburg pressured regulators and put profits ahead of the safety of passengers, pilots, and flight attendants. He'll walk away with an additional$62.2 million. This is corruption, plain and simple," U.S. Senator Elizabeth Warren said on Twitter.
Has there been any recent word on the criminal investigations?

And lest we forget.
Victims of the Etiopian Airlines crash

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

### RE: Boeing 737 Max8 Aircraft Crashes and Investigations [Part 6]

Spar your taxes will go up anyway. Boeing is going to have to pay by the min for EASA and others certification now.

Foreign OEM's will get it for free under the current FAA system.

Boeing is going to pay the full cost anyway because the FAA is deemed untrustworthy due having a utterly shite system which has been proven to kill.

Realistically the FAA market is reducing by the day, just look at its sale figures for last year never mind delivery's . If the eastern regulators accept EASA but don't FAA and FAA don't accept EASA due to willy waving a pissing contest then Boeing will have to walk the walk anyway because the N reg is just way way to small to pay for type certification with multiple type certs round the world.

Boeing might as well ditch the FAA and go for one that's trusted for initial type certification.

Nothing heard about the multiple investigations, most of us expect it to go the same way as the Challenger investigations and the banking collapses and absolutely zero people being held to account, just more air than out a hot air balloon and cock all changing inside the borders of the USA.

STC's will have to get dual approved for the foreseeable future. Which will mean more work for you. Although I suspect if you just do the EASA route initially then the rest will be tick boxes.

### RE: Boeing 737 Max8 Aircraft Crashes and Investigations [Part 6]

Not much changed lately then:

“There is hardly anything in the world that someone cannot make a little worse and sell a little cheaper, and the people who consider price alone are that person’s lawful prey. It’s unwise to pay too much, but it’s worse to pay too little. When you pay too much, you lose a little money — that is all. When you pay too little, you sometimes lose everything, because the thing you bought was incapable of doing the thing it was bought to do. The common law of business balance prohibits paying a little and getting a lot — it can’t be done. If you deal with the lowest bidder, it is well to add something for the risk you run, and if you do that you will have enough to pay for something better.”

John Ruskin (8 February 1819 – 20 January 1900)

Politicians like to panic, they need activity. It is their substitute for achievement.

### RE: Boeing 737 Max8 Aircraft Crashes and Investigations [Part 6]

Seems the latest software issue is due to the fixing of the autopilot disconnect issue.

On start up and the systems running their internal bite tests. The computers are ready at different times and then produce errors and fail bite tests because other systems are not ready to talk to them.

End result the whole data bus system fails to sync and HAL goes in a sulk.

The fancy engineering simulator didn't get this issue. They only found out when they loaded it on a real aircraft.

### RE: Boeing 737 Max8 Aircraft Crashes and Investigations [Part 6]

Spar,

If one of your family members dies on a plane that was poorly designed by a company is too big to fail, the govt doesn't have enough money to review, and that company faces minimal punishment, you may feel differently.

Yes taxes maygo up if the FAA got proper funding. Good, that means they can do their job; otherwise just get rid of them so we can stop pretending. Companies, especially large companies, have shown repeatedly that society cannot rely on them to "self govern/regulate"; they need someone above them keeping them from pushing the line. Or, to avoid taxes going up, we could stop getting into endless "wars" costing trillions.

### RE: Boeing 737 Max8 Aircraft Crashes and Investigations [Part 6]

Thank you for bringing this to mind, Alistair.
The sub prime crisis was a made in America, too big to fail crisis, and the solution was political.
The automotive crisis was a made in America, too big to fail crisis, and the solution was political.
What most of us including Boeing, the FAA, the parent Department of Transportation and the American law makers may not be considering is that while this is a made in America crisis, a political solution may not be acceptable to the international community.
The approval of the Joint Committee is more important than anything the FAA does.

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

### RE: Boeing 737 Max8 Aircraft Crashes and Investigations [Part 6]

To be fair I think the FAA does realise that the Joint Committee is the prime driver in all this.

Both the FAA and Boeing know fine that a FAA only approval doesn't fix the issue. It will just leave internal US airlines with a load of worthless airframes if they end up with N reg version and rest of the world version if it gets certified at all. The leasing company's won't be interested in them either. So I don't think Boeing would be interested in a FAA only certification.

It a bit worrying that the Engineering simulator didn't pick up this latest issue. If it doesn't pick up a cold start bootup BITE checking hang what else has it missed?

And this was meant to be the MCAS 2 which the FAA was meant to approve in October after watching a power point presentation and Boeing were going to start delivering before 2020.

BTW this boot issue/ loss of sync occurs on other types as well. The solution is you have to power down to black aircraft and leave for 30 seconds then bring everything back up. It can then take another 10 mins for the NAV stuff to get to within limits accuracy and re program the FMC etc.

### RE: Boeing 737 Max8 Aircraft Crashes and Investigations [Part 6]

Now at least July.

https://www.bbc.co.uk/news/business-51200118

I'm not sure I agree that the"flaw has been fixed".

In trying to fix it I think they keep running into more dead ends. The report on the tv also mentioned something about wiring and needing to change it.

But July. Wow.

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

### RE: Boeing 737 Max8 Aircraft Crashes and Investigations [Part 6]

To my mind this debacle is taking on all the elements of a Shakespearean tragedy.

"Schiefgehen wird, was schiefgehen kann" - das Murphygesetz

### RE: Boeing 737 Max8 Aircraft Crashes and Investigations [Part 6]

2
The specific engineering mistake(s) that lead to the MAX crashes are a relatively minor issue. Though a tragic oversight.

However the can of worms has been opened and the worms are ugly as hell. The previous generation the 737NG probably has a pile of 'issues' that never should have passed in the first place. But it has gotten away with it by a grandfathering and a bit of hoodwinking of the FAA. The fact that the 737NG has been largely reliable helps too even if it doesn't meet the letter of the law requirements.

The 737MAX has no such luxury. It started off as a hack job in the first place and now it being examined with a fine tooth comb.

It is a disaster all round that will cost many tens of billions not all on Boeing. The entire supply chain is hurting, airliners are hurting, consumers are hurting though they'll largely not notice it. Airbus is the only winner here. But the majority of European stakeholders would still be better off it Boeing was still in the game.

Also as said many times previously. This is less of an engineering mistake and more of a managerial mistake, decades in the making. And it will take as long for Boeing to dig itself out of this hole.

### RE: Boeing 737 Max8 Aircraft Crashes and Investigations [Part 6]

This article is running in quiet a few places.

https://www.seattletimes.com/business/boeing-aeros...

Must admit I don't know too much about this one.

But from what I have seen last evening its similar 1 sensor wired "funny" and a presumption the pilots will instantly spot the issue and deal with it. Which they did 8 times and didn't on the 9th. But Boeing managed to get away dealing with it, they tried the same tactics with the MAX and it didn't work this time.

### RE: Boeing 737 Max8 Aircraft Crashes and Investigations [Part 6]

human909.

I would dispute your statement that the "mistake" - which one by the way? - was a relatively minor issue. The mistake it would seem was trying to extend the flight envelope of a 50 year old design and add on a semi FBW design to a system which simply isn't designed for it. That's not a minor issue, but a fundamental engineering design decision driven and forced by other factors (time, money, no SIM training). IMHO.

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

### RE: Boeing 737 Max8 Aircraft Crashes and Investigations [Part 6]

The "wired funny" bit on the 737NG crash seems to be that whilst nearly everything else works Left and right side in terms of sensors and flight computer etc, the altitude sensing device which ran into the auto throttle preferentially used the left side. Thus although the pilots knew the left sensor wasn't working properly they thought it was OK as all the other flight controls were on the right side. There was no mention of this anomaly in any of the manuals or training - sounds familiar?

But the real key is this overall human factors / overload on the pilots of things happening to the aircraft which don't make sense and take more than a few seconds to work out what it is while all hell is breaking loose with alarms, stick shakers and dodgy information.

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

### RE: Boeing 737 Max8 Aircraft Crashes and Investigations [Part 6]

yep...

And they new about and designed the same stuff into the max.

Here is the report from Dekker I have actually met him face to face and sat in on one of his lectures. He knows his stuff.

https://www.onderzoeksraad.nl/nl/media/inline/2020...

The most damaging aspect is that accident reports are now political.

### RE: Boeing 737 Max8 Aircraft Crashes and Investigations [Part 6]

There's a new phrase - "automation surprise" and "non event".

I wonder how many more automation surprises they are now finding out about.

Will this version fly again?

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

### RE: Boeing 737 Max8 Aircraft Crashes and Investigations [Part 6]

If they'd had a crash with the 737 NG due to relying on only one of the sensors, and they upgraded the 737NG where they could to use two sensors data, why would they have persisted with the faulty single sensor concept in the 737 MAX? Did they just forget about it?

### RE: Boeing 737 Max8 Aircraft Crashes and Investigations [Part 6]

Different sensor. Altitude vs AoA.
They had a fix for the newer NGs, but not for the older models.

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

### RE: Boeing 737 Max8 Aircraft Crashes and Investigations [Part 6]

Slow learners? No, they were able to fudge the accident report on the NG crash.
First rule; Blame the pilots.
Second rule; Second guess the pilots.
Any more rules to add Alistair?

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

### RE: Boeing 737 Max8 Aircraft Crashes and Investigations [Part 6]

#### Quote (waross)

Different sensor. Altitude vs AoA...

Same lack of system redundancy, same lack of effective documentation, same lack of systems training.

### RE: Boeing 737 Max8 Aircraft Crashes and Investigations [Part 6]

#### Quote (waross)

Different sensor. Altitude vs AoA.

That's Boeing's excuse. Totally different. Apples and Oranges crashes. I would hope most engineers can see thru that.

#### Quote (waross)

They had a fix for the newer NGs, but not for the older models.

Yes and they fixed it where they could, didn't they?

So why when building new planes wouldn't you just avoid the single sensor concept from the outset?

### RE: Boeing 737 Max8 Aircraft Crashes and Investigations [Part 6]

(OP)

#### Quote (Tomfh)

So why when building new planes wouldn't you just avoid the single sensor concept from the outset?

Well, that's the big mystery. There's a safety requirement that requires reliability on all systems that affect the flight controls, including trim. There a standard for compliance that spells out how to assess how critical as system is to the safety of the aircraft, and how to deal with systems that fall into a "major" or "catastrophic" criteria. Somehow Boeing managers/engineers really put the blinders on, despite contrary opinions being expressed internally within the company, that were telling them from many sides that the system was glitchy as all hell. Some of them even seemed to know where the shortcomings were.

### RE: Boeing 737 Max8 Aircraft Crashes and Investigations [Part 6]

#### Quote (SparWeb)

Well, that's the big mystery.

Could it have been an oversight to start with, and by the time they thought about it the design was too far advanced, and so they let it slide?

### RE: Boeing 737 Max8 Aircraft Crashes and Investigations [Part 6]

Ahh Safety assessments.
A good manager can really shine when overruling engineering during a safety assessment.
I was once involved in a safety investigation.
A nose bag was lowered from a height.
It contained a rattle can of paint and some short pieces of steel angles.
It must have hit the ground too hard because something punctured the pressurized paint can and it was hissing.
A worker wondered why it was making a funny noise and picked it up and turned it towards himself.
He painted his face. I don't remember what colour.
He was very upset and in some distress.
First aid was called and they helped him to wash his face and sent him back to work.
Several weeks later I found myself in a safety investigation meeting.
We had a matrix to fill in.
There were five or seven headings and a numerical value under each heading.
We were making our way through the matrix and one heading was;
"How likely is this to happen again?"
The manager leading the investigation stated that it was very unlikely to ever happen again and assigned a low number.
Someone suggested that with the size of the project it may be a little more likely that such a thing could happen again.
The manager thought for few seconds and then stated that;
"No, the likely hood that this will happen again with that size of paint can, in that color, being lowered from that high line is very unlikely. We will stay with this number. (I forget the exact conditions that he stated but his assessment was very very much more restrictive than someone accidentally being sprayed in the face with spray paint.
No one had the temerity to challenge him further.
We finished the matrix and then added up the numbers from each column.
We compared this with another chart which gave us a course of action depending on the total.
Our number allowed us to handle the issue locally and for all intents and purposes that was the end of the inquiry.
Had our number been one digit higher a company vice president would have to be notified and review the incident.
And I thought to myself;
"So that's how the game is played here. I don't think that that is the intent but he plays the game very well."
I wonder where he is now. He could probably be working for Boeing. He knows how to spin the game and fudge the numbers.
Many of you will have had similar experiences.
Those who have not, if you are working for big business, wait for it. Your turn will come.
What did I learn?
If you don't want to be involved with this kind of charade:-
Don't be a witness;
"I was looking the other way and didn't see a thing until it was all over."
Two can play the game, but one may also opt out.

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

### RE: Boeing 737 Max8 Aircraft Crashes and Investigations [Part 6]

Seems the next Boeing aircraft is going to be a clean sheet design.

https://www.seattletimes.com/business/boeing-aeros...

I suspect we will see a FBW Boeing system which can be ported across all new types.

I might add Airbus needs to go through this as well and update its FBW system and philosophy.

To be fair the first rule of blame the pilots is actually usually correct and it is the pilots.

But before all this work starts the regulators are going to have to define a sensible set of standards for data saturation and reaction times. Linked to the normal pilot profile of technical knowledge and thinking. Dump the average pilot mentality and design for the most clueless idiot that can get through basic training. Old days most pilots had an engineers head on them, they thought in energy and instinctively "knew" what to do with the controls to get an energy state. These days its all SOP's and call outs. The theory being that if you always do the SOP's precisely then everything will be safe. But the older designs still rely on the engineering head to recognise what the primary problem is and know which checklist you use to fix things.

My first type rating on the BAe Jetstream 31/32 technical training went down to how the fuel controller worked metering the fuel and how the Propeller pitch controller worked. My last rating on the Q400 we were told each engine has a FADEC which is powered by its own generator. They look after the engines, failure tree is powerplant for advisory, yellow cap for caution, and red cap for Major. And that was it, half a A4 page on the subject where as the Jetstream had some 32 pages on the subject. Personally I found the Jetstream a bit to much detail but the Q400 its a definite policy to only tell the pilots a defined amount of information so they can't get creative. It used to annoy me when I first started flying the Q400 but over the last 2500 hours have come to realise that its probably for the best, having people getting creative pulling CB's trying to fix things will be fatal.

### RE: Boeing 737 Max8 Aircraft Crashes and Investigations [Part 6]

#### Quote (Tomfh)

Could it have been an oversight to start with, and by the time they thought about it the design was too far advanced, and so they let it slide?

I extremely doubt it was oversight, I can't prove it and don't have any data to back my opinion up.

It all revolves around not triggering critical software certification, using as much grandfather certification as possible. And this requirement that pilots can get away with 30mins looking at an Ipad for training.

I really don't think the current MAX is the aircraft that the people in the design shop wanted to produce. And even after they have re certified it people will not have any feeling of pride when they see one flying because basically its not the aircraft they wanted to make.

### RE: Boeing 737 Max8 Aircraft Crashes and Investigations [Part 6]

(OP)

#### Quote (Alistair Heaton)

its probably for the best, having people getting creative pulling CB's trying to fix things will be fatal.

Yes, before the plane takes its first flight, as many disaster scenarios as possible are pictured in advance, and the response planned in such a way that the procedure gets you on the ground in one piece. The history of aviation has put a lot of smoking pits in the ground to inform the engineers what kinds of mistakes and failures are likely to happen. Indeed, this process of testing the assumptions and evaluating the aircraft response to the emergency procedures in simulators before flying the real thing is the subject of many (maybe most) of the e-mail and IM traffic that was released in those documents.

AH, if you still want the information overload for your turboprops, just sit down to read the maintenance manual. When you're done (a month later) then you'll have more insight into every actuator and pump on the thing than you ever thought you'd need to know. The OEM's haven't really intentionally dumbed down the AFM's, they've just concentrated the data in other books. It's not actually better that way. The maintenance crews can't see the operations books and vice-versa.

www.sparweb.ca

### RE: Boeing 737 Max8 Aircraft Crashes and Investigations [Part 6]

We are not allowed to read them, even the fleet technical pilot has limited access to them as information has a tendency to propagate via galley FM.

The Jetstream I had access to everything, was qualified to do daily and weekly checks on them. Had dupe authorisation for signing off control run maint. I could change tyres..etc

I even did an engine change on one and re rigged it with one of the B1's checking things at crucial points. I still have the wire lock scars from that one.. I thoroughly enjoyed it though.

I could sign off MEL's and differ things and clear them.

I used to have a knack of finding out what electrical issues were occurring. Which was more about trouble shooting technique, isolation of the problem and tracing it. It wasn't an in depth knowledge of the systems per say just an engineers logic. The technicians tended to just swap boxes in the hope it would fix the problem.
But when it came to finding out which 3 way microswitch was acting up on an intermittent fault that technique used to fall over.

Q400 I am not allowed to change a light bulb. Only thing we are authorised to do as Captains is the Overspeed Governor Check. I am more than happy with this situation.

I do know where you coming from though with differences between manuals. The required O2 pressure for 3 crew in the front is a classic example. Our book says 1800 psi at 5 deg temp and the maint book says 1600 I think. Thankfully management top cover has settled that particular issue and when the jump seat is to be used then they fill the bottle up to max what ever its reading.

### RE: Boeing 737 Max8 Aircraft Crashes and Investigations [Part 6]

Following the feelgood pep talk link by Calhoun posted by Alistair I came across this interesting article.
Longtime Boeing advocate Maria Cantwell formally criticizes report on FAA’s certification process for 737 MAX
Some excerpts:
Maria Cantwell, Washington’s junior U.S. senator and longtime Boeing advocate, criticized Friday a government advisory committee’s findings this week that largely endorsed how the Federal Aviation Administration oversaw the certification of the 737 MAX, saying it “defends a system that is in clear need of improvement.”

That report concluded that federal regulators followed established procedures when they certified the Boeing 737 MAX and did not delegate too much safety oversight for the plane to the airplane manufacturer itself.

In a letter to U.S. Secretary of Transportation Elaine Chao, Cantwell wrote that the special committee’s report “falls short” and contradicts findings and recommendations for safety improvements that have been made by other review panels.
...
Cantwell’s criticism joins that of at least two key House lawmakers who’ve said they plan to seek legislative reforms to the FAA’s certification process. Rep. Peter DeFazio, an Oregon Democrat who chairs the House Transportation and Infrastructure Committee, and Rep. Rick Larsen, an Everett Democrat who chairs the House panel’s aviation subcommittee, each criticized the report’s findings in statements this week.
....
Like Larsen, Cantwell is a longtime Boeing advocate who supported the FAA Reauthorization Act of 2018 that changed the certification process to allow for more delegation of regulatory oversight to Boeing and other manufacturers.

Boeing employees collectively contributed nearly $62,000 to her reelection bids since 2015, according to opensecrets.org. A spokeswoman said Cantwell doesn’t take money from corporate political action committees. Is this a display of moral courage or am I missing something? Bill -------------------- "Why not the best?" Jimmy Carter ### RE: Boeing 737 Max8 Aircraft Crashes and Investigations [Part 6] Notice though they have a Semi realistic time scale for it flying again. I don't think they will manage it though, but would love to be wrong. This time next year is my gut feel. ### RE: Boeing 737 Max8 Aircraft Crashes and Investigations [Part 6] I really don't understand the legal aspects though of the various committees and investigations. As far as I can tell there 7 different processes going on. How they could effect it flying again and the people involved I have no clue. ### RE: Boeing 737 Max8 Aircraft Crashes and Investigations [Part 6] #### Quote (Alistair) It all revolves around not triggering critical software certification, using as much grandfather certification as possible Ok sure. What was the AoA sensor setup on the NG? How many feeding into computers and in what configuration? And what did the pilots know? ### RE: Boeing 737 Max8 Aircraft Crashes and Investigations [Part 6] Same as the MAX. AoA feeds into multiple computers, stall protection, Flight management computers to work out current weight and a few others. So 2 sensors. And I believe even the part numbers are the same from the 737-300 right the way through to the MAX. There were options to have a AoA gauge on the NG on the EFIS screen like the MAX. But very few airlines paid for it. https://www.satcom.guru/2019/10/flawed-assumptions... if you dig through that blog I think he does a comparison between the two. ### RE: Boeing 737 Max8 Aircraft Crashes and Investigations [Part 6] #### Quote (Alistair) So 2 sensors. And I believe even the part numbers are the same from the 737-300 right the way through to the MAX. How come it would void automatic recertification to have the MAX use both sensors? Thank link says Boeing was already working on a two sensor fix after Lion air? ### RE: Boeing 737 Max8 Aircraft Crashes and Investigations [Part 6] I think the basic problem is with only two sensors, and not three, and only two FCC and not three, which one do you believe if the readings diverge? An average? Just forget about the reading if they are xx degress apart? But then how do you decide on x? Basic problem is that the MAX needs MCAS to work when the AoA is high. Just making the input zero when it should be working might cause a stall to occur. Fix one problem to create another. Also the FCCs are ancient technology, but probably fairly simple and hence high reliability. Now you need to get them talking to each other in a reliable manner. Not easy. And again how will the other one know which reading is correct. This is really the issue - the airplane needs a higher level of computer reliability and operation than it is built for to correct a fault in the physical make up of the airplane because the landing gear is too short for the engines they want to use. That's why your grandfather needs to retire eventually and go and sit on the porch watching the other airplanes fly past.... Remember - More details = better answers Also: If you get a response it's polite to respond to it. ### RE: Boeing 737 Max8 Aircraft Crashes and Investigations [Part 6] Changing the logic of the way you use the sensor data is counted as a major change and you need to certify the changes. So if the NG only uses 1 input at a time and you do the same with the next then that system is deemed grandfathered and no further testing required. Start using two inputs then you have to recertify the changes. As said above using 1 or 2 doesn't actually add in any failure protection because you can't know which data is good and which is bad. You can only stop using both. The problem they have is that the MCAS that requires that data is required for the flight envelope to be certified as fit for use by the pilots. Loosing all the data then dumps everything on the pilot with an uncertifiable aircraft. If there would be 2 or 3 additional failure levels before dumping it on the pilot then that would be deemed acceptable. Because there is computers involved then what they are deemed to do defines what certification level they require. if their job is not deemed to be critical then they are certified to a lower level. Critical which is required for anything to do with FBW controlling of critical flight surfaces then the standard is much higher. There is another huge area which Boeing might have issues in, is MCAS actually an anti stall system or not. If it is deemed to be one then the certification requirements are again higher and different. But this is sparwebs area of competence. I am just an end user who used to dabble in such things for minor changes of a none structural nature. So if he comes back and says no your wrong AH then I will have zero issue with that. ### RE: Boeing 737 Max8 Aircraft Crashes and Investigations [Part 6] A few tidbits that I have come across in the Dept of Transportation report (pp 31 & pp 60) Statement by a poster: Changing the landing gear would require re-certification of the gear. General Description of the Aircraft #### Quote (Dept of Transport Report) The 12 changes identified by Boeing at the time of application as “significant” under the changed product rule, in accordance with 14 CFR 21.101 are 2.A longer nose landing gear strut to provide greater engine ground clearance; 8.Strengthening the main landing gear to accommodate heavier engines; [quote ] Statement by a poster: Changes to the wing would trigger re-certification [quote DoT]10.Strengthening of the local empennage and fuselage to accommodate heavier engines; 12.Wing strengthening to accommodate heavier engines. The full list: The 12 changes identified by Boeing at the time of application as “significant” under the changed product rule, in accordance with 14 CFR 21.101 are: 1.The use of more powerful engines with better fuel efficiency; 2.A longer nose landing gear strut to provide greater engine ground clearance; 3.New strut and nacelle to account for heavier engines and new engine positioning; 4.Advanced technology winglets to maximize the overall efficiency of the wing and reduce fuel use; 5.A reshaped tailcone to reduce drag; 6.A digital engine bleed system for increased optimization of the cabin pressurization and ice protection systems, giving reduced fuel use; 7.A fly-by-wire spoiler system to improve production flow, reduce weight and improve stopping distances; 8.Strengthening the main landing gear to accommodate heavier engines; 9.A modified fuel system; 10.Strengthening of the local empennage and fuselage to accommodate heavier engines; 11.System revisions (note: changes to flight controls, including the introduction of MCAS, were covered by this listing); 12.Wing strengthening to accommodate heavier engines.(See Appendix 6.2.) With the many mentions of Fly By Wire in this thread I thought that item #7 was interesting. #### Quote (DoT) n the FAA’s certification of the Boeing 737 MAX 8aircraft, which took place from 2012to 2017. Bill -------------------- "Why not the best?" Jimmy Carter ### RE: Boeing 737 Max8 Aircraft Crashes and Investigations [Part 6] #### Quote (Alistair) Changing the logic of the way you use the sensor data is counted as a major change and you need to certify the changes. So if the NG only uses 1 input at a time and you do the same with the next then that system is deemed grandfathered and no further testing required. Start using two inputs then you have to recertify the changes. Ok. Is that what they did with the NG when they upgraded to using two sensors after the other crash? ### RE: Boeing 737 Max8 Aircraft Crashes and Investigations [Part 6] Apparently the NG alternated between the right and left flight control computers and each computer had its own sensors. Except that the automatic throttles did not alternate and always used the same sensor. Apparently the pilots knew that the left sensor was dodgy, but thought that they were OK because they were using the right control computer. They had never been told that the automatic throttle never alternated sensors. When the auto pilot unexpectedly reduced the throttles to idle they were unprepared and they did correct but it was too late. Uhm, Only one sensor. Unexpected activation of a system that had not been fully disclosed to the pilots. Boeing knew about the problem and deployed a fix for the newer planes. BUT They did not think that it was serious enough to alert the pilots of the older planes. Then the accident report; Pressure on the regulators to get the spin that they wanted. Down playing and minimizing the seriousness of possible consequences seems to be SOP to slip borderline issues past the FAA. We only have to fudge one metric to get this matrix below the decision line . Deja vu all over again, Yogi? Please, if I have seriously misunderstood the events, correct me. Bill -------------------- "Why not the best?" Jimmy Carter ### RE: Boeing 737 Max8 Aircraft Crashes and Investigations [Part 6] They will have gone through a certification process for the new setup. And I presume the MAX will use 2 rad alts as well due to grand father certification from the NG fixing that problem. But maybe not!!!! as Boeing seems to love using single sensors for flight critical systems. The Q400 uses 2 and one can fail and all you get is "RAd Alt # fail" on the central screen but it doesn't effect anything. You can still do CAT II approaches. If one fails during a CAT II approach its about the only tech issue you can continue the approach. But that's the limit of what pilots are meant to know. Its 10 days to get it fixed but you can continue to operate without any restrictions. There are different grades of changes and depth of testing after they are done. I can't remember the full list. The level of change is also subject to interpretation. It depends on what things are connected to, and what authority over the aircraft the data has. I have only ever dealt with minor changes which are really only very expensive paper work exercises. Rad alt complete failure is a funny one it worms its way into 3/4 safety systems such as EGPWS and TCAS on turboprops without AT, 15 years ago you really didn't care about if the Rad alt was working. You would loose CAT II/III capability and you would run quiet happily without it for 10 days. These days it triggers a cascade through the MEL taking out other systems which means if its gone your pretty much limited to 3 days in most places and 6 sectors if your flying in German airspace. But per say its nothing to do with the rad alt itself, its the systems hanging off its data that are the limitation. The OEM's don't really seem to care about this mid life modifications and certifications as long as the planes are flying and are coming out the production hanger and money is rolling in. Now the MAX is grounded and the can of worms opened with the regulators there is a raft of issues surfacing which would normally be fixed anyway before the product is deemed mature. I am sure as well some of the issues would never have surfaced because nothing would happen in the real world to highlight them. It seems the NG is a perfect example of this. Great safety record but the MAX is highlighting now a chunk of issues which made it past certification on the NG and were then grandfathered onto the MAX and now under increased scrutiny are raising the question how they hell was that certified on the NG. So Boeing has the original MCAS issue to deal with, which a lot of us think was a distraction fix for an uncertifiable flight envelope. But even if they fix the MCAS the underlying issue which it was created to fix/hide is now out in the open and needs fixed as well. That issue was not simple or cheap to fix in both time and money during initial design. But its certainly cheaper than the current 11 billion bill increasing by the day that is the current situation. The real issue for Boeing is the aircraft is grounded and all the issues which would have normally been fixed in the first 5 years of it flying are having to be done now under intense scrutiny on the ground with no money coming in. ### RE: Boeing 737 Max8 Aircraft Crashes and Investigations [Part 6] I don't know much about aviation, but it sure sounds like a mess. If I was Boeing CEO and I was offered Jan 2021 for commercial resumption I'd take it! ### RE: Boeing 737 Max8 Aircraft Crashes and Investigations [Part 6] They won't be offered anything. Its up to Boeing to prove to the regulators that the aircraft is compliant. They have basically spent the first 9 months trying to bluff and use lawyer talk to get the aircraft flying again. There was also a huge media push to blame the pilots. Which failed miserably I might add globally, but seemed to have an effect in the USA. But as the FAA is seen globally to have failed to do its job its had zero effect. I think in Nov when there usual power point presentation failed to pass the documentation "check" with basically the regulators walking out. They realised it wasn't going to work. They then tried putting pressure on about shutting down production, the bluff was called and its now shutdown. In that period between Nov and now quiet a few of the "faces" have either been removed or have left themselves. But that's only one side of it, to do with the actual aircraft in question. The flip side is that the regulators have discovered huge issues amongst themselves. Basically over the last 20 years they have been moving towards a global system of trust so that multiple certification processes don't have to be run. That's been blown out the water. Also its been noted that the regulations are not fit for use with modern aircraft systems and also the current pilot demographics and training standards. The 737 MAX is a bit of a frankfurter mish mash of standards anyway due to it organically growing from a 1960's design. The 737 was one of the first commercial aircraft without an Engineering station in the cockpit. Training, information flow, acceptable information load, what can be grandfathered are now for the regulators to sort out before the next batch of new types are started. Boeings mantra has always been the pilot flies the plane, Airbuses mantra is the pilot manages the system. Like it or not modern aircraft are a load of complex interconnected systems inside an aluminium tube. As soon as you get to the point those systems have a primary input into the aircraft controls you have to manage the complete package because the pilot can't just fly the plane and then work out what is going on. The biggest issue is working out what to turn off to be able to just fly it without fighting with a system. The current regulation and assumption is the pilot should only need 3 seconds to diagnose the problem and kill the rouge system. That has been proved multiple times as being completely unrealistic. Boeings problem is that a lot of its certification assumptions are that the pilot will respond inside 3 seconds and will stop the failure becoming catastrophic. Therefore the failure and system is deemed acceptable. After putting more than a few normal pilots through the sim using the current Boeing procedures it was found that over 50% failed to get the correct emergency checklist for the fault. So the whole emergency checklist and operating procedures and training also need to be sorted. Which for the 737 is colossal. Modern new design aircraft have a thing called ECAM which leads you through the checklists, priorities the fault and most importantly remembers the series of failures progressing. So if it starts with a bus fail and as things progresses it ends up with half the electrical system showing a fault as services drop out the ECAM will show the checklist of BUS fail. One switch change to kill a generator or tie a bus bar and everything goes out apart from the guilty system. MAx could have had a ECAM system same as the 777 but didn't get it due to grandfather certification and costs and time getting it certified and this huge issue for them it would trigger training requirements. So the MAX has a paper book which is about 5 cm thick and you have to find the thing first of all, then work out what your issue is, then find the page and run the checklist... all in 3 seconds. If you get the wrong drill then you can end up making matters worse. For the above electrical failure it is not unknown for people to shut down engines because they haven't spotted the bus fail was the first lamp to light up. Boeings line is that shutting down an engine by mistake is not a catastrophic failure and nobody will die IF the pilots then go onto fly the aircraft properly single engine. So no need to have an ECAM system fitted. So you have a system which diagnoses the issue and takes you the correct checklist. It is displayed in the middle of the cockpit so its possible for both pilots to see it at the same time. It is impossible to drop it or not find the book in roller coaster conditions. It even automatically checks items when it senses they are done. If they are done already it won't mention them. If things change away from what's required after the checklist is complete it then flags they are incorrect. MAX pilots will still have a 5cm thick paper book behind the FO's seat when it starts flying again. BTW the QRH paper book is 5cm thick on the MAX....new aircraft On the Q400 its 2.5cm thick 15 year old aircraft 1cm thick on the Jetstream 31/32 35 year old aircraft. A220/CS no book and 1 memory item new aircraft with zero grandfather systems. Its a mess which has been developing for the last 20 years or so. The Boeing MAX is just the trigger for things having to change. ### RE: Boeing 737 Max8 Aircraft Crashes and Investigations [Part 6] waross, without going too far off track, but the incident referred to in amsterdam was actually that initially the auto throttle did exactly what was expected ( went to idle) because they were trying to pick up the glide slope having got a late call to land. The issue was that after 70 seconds when the throttles should then have kicked in to maintain speed they didn't and hence this was what the report ( which is a long but very good read from the link by AH) says was an unexpected error or basically something didn't happen which should have. These are difficult to pick up when they are normally so reliable. The fact that that system worked differently to all the other systems in its reliance on the left hand R/A wasn't in any manual or any training and it is very difficult to blame the flight crew I think. The other big issue was that the Radio altimeter wasn't strictly failed, but just giving the wrong data. Hence it was outputting a signal / number / altitude, but just the wrong one. One consequence was that there was a near constant alarm going on about needing to lower the undercarriage which didn't make sense to anyone when they were at or above 2,000ft above the ground. but yes there has been an insidious creep of automation and control into the Boeing family of planes which means that they have become semi FBW planes without all the required back ups and three seconds to sort something out is not feasible. In reality how the 737 NG has been so reliable seems to be pure luck / pilot skill. Remember - More details = better answers Also: If you get a response it's polite to respond to it. ### RE: Boeing 737 Max8 Aircraft Crashes and Investigations [Part 6] Thanks LittleInch. Maybe faulty rather than failed. As far as doing what it should, I once had to trouble shoot a machine that automatically set sizes. If it approached the target from the right it was accurate. If it approached the target size from the left there was an unacceptable 3/4 inch error. I wouldn't accept the premise that it was doing exactly what it was supposed to, until.... The pilots thought that they were on one system when they were on the other. By reducing power at the proper time, the problem was masked and there was no indication that they were on the faulty sensor until it was too late. The main point is the similarities in process. lack of training and the direction that Boeing's culture was developing. While the system reduced power as it should have, by doing so it masked a serious issue. Bill -------------------- "Why not the best?" Jimmy Carter ### RE: Boeing 737 Max8 Aircraft Crashes and Investigations [Part 6] They are a pain in the arse to be honest, with the old school ones which the NG and the MAX will have due grandfathering. But like all these things thier role has morphed over time from just a height indication above ground to being linked to 4-5 safety systems and 2-3 flight control systems on Jets. They have twin transmitter and receiver under the aircraft. Two pods with a Tx and RX in each for the two channels . The old school units the pod was hollow made out of fibreglass and a cable came through the pressure hull and the connection made inside the pod. The pods were then sealed onto the aircraft with basically bathroom silicone and bolts to hold them on. The fibreglass used to crack and then wick water into it which would then screw with the measurements. The sealant used to go and then a pool of water would form in the bottom of the pod and also corrode the connections. The water used to freeze thaw during flight cycles which just made matters worse. Modern units have the same fore and aft configuration but the cable goes through the pressure hull and the connector is internal. The whole lot is embedded in resin and there is an outside cover of Kevlar mat which is a 10 min job to replace. When they replace the cover they cook them to dry them out and then reseal them and then paint them again with special paint unless the matrix has been destroyed through getting a stone on it. The Jetstream it used to regularly appear in the techlog and deferred item list with the old school ones, monthly. In the last 4 years on the Q400 I haven't seen a single mention of rad alt failure and don't have a clue if they are old school or new they just work and never seem to give any trouble. But the Q400 is cat II approved and dual FD approach certified and maintained which may include additional checks and maintenance on that system, as pilot I don't need to know. The issue per say isn't that it failed and caused a crash. Its the fact that Boeing managed to influence the resulting Accident report to adjust the primary cause of the accident and remove the focus away from the technical and HP issues with the design. And then to add insult to injury they seem to have repeated the same mistake with the MAX on another critical system which has input on a primary flight control. ### RE: Boeing 737 Max8 Aircraft Crashes and Investigations [Part 6] #### Quote (Alistair) The issue per say isn't that it failed and caused a crash. Its the fact that Boeing managed to influence the resulting Accident report to adjust the primary cause of the accident and remove the focus away from the technical and HP issues with the design. And then to add insult to injury they seem to have repeated the same mistake with the MAX on another critical system which has input on a primary flight control. That is the point of my last post but you have said it much better than i could. Thank you. Bill -------------------- "Why not the best?" Jimmy Carter ### RE: Boeing 737 Max8 Aircraft Crashes and Investigations [Part 6] #### Quote (Alistair) In reality how the 737 NG has been so reliable seems to be pure luck / pilot skill. I think that’s an aspect of engineering in general. There are lots of holes, but the holes have to line up for people to die. Admittedly there are usually more layers of cheese, and people generally fix the gaping holes, rather than assume the pilot layer will catch anything that falls thru... ### RE: Boeing 737 Max8 Aircraft Crashes and Investigations [Part 6] It wasn't me that said it but... I think what it is, is that Boeing is very good at metal structures. It knows what its doing with hydraulics and good old fashioned relays. And knows its materials (I am not so sure with its composites). If you going to go off road in an aircraft or the gear collapse Boeing has a superb safety record of sacrificing the airframe and protecting the occupants. Its just years behind the other OEM's with digital systems. And its not helped by the fact that since the merger it has only pushed stretched model upgrades. Models which if you showed the original designers the current models they would have to sit down with a cold sweat. These systems which are shoe horned in are removing layers of cheese compared to older versions just to get them to work. So you have far less to line up for a fatal accident. NG has a disconnect on the yoke so when the pilot pulls back at over xxlbs of force it cuts out the systems input to the stab. NG has twin cut out switches, one cuts the AP/system input and the other one cuts the electrical trim. So there you have it, NG the third failure layer is the pilot. And if the max had those options I suspect both crews would have saved the day. One of them would have functioned/been used and the MCAS would have been removed from the equation. I don't think it is luck with the NG, its just a way better system design. So more layers of cheese. ### RE: Boeing 737 Max8 Aircraft Crashes and Investigations [Part 6] "[Boeing is] ...years behind the other OEMs with digital systems." Over the decades, there's been a pattern of Airbus FBW incidents where the pilots didn't intend that the aircraft would strike the ground, but the aircraft rather insisted. A common thread is that the aircraft was in perfect mechanical condition in the millisecond before impact (some with clogged pitot tubes). During those same decades, the typical Boeing incident often involved something breaking at the outset. A fairly common thread was that the aircraft was mechanically damaged at the beginning of the incident (sometimes faulty repairs). These historical common threads have largely evaporated over the past decade. Now we're seeing Boeing giving the automation more authority (e.g. MCAS). I hope that we're not entering an era of mechanically fit Boeing aircraft that occasionally insist on striking the ground. Lesson to be learned: automation requires more training, not less. ### RE: Boeing 737 Max8 Aircraft Crashes and Investigations [Part 6] I can't remember any, where the airbus aircraft took them into the ground through computer inputs to the flight surfaces. Last one was when it went into the forest believing it was landing and not spooling up because the pilot hadn't pressed TOGA to get it into climb mode. If your meaning the AF447 where after an airspeed issue the crew pulled back on the controls all the way to the ground in a stall not following the procedures. I might added that we stopped teaching pull the stick back in a stall in world war 1. If you do that with any aircraft you will die. ### RE: Boeing 737 Max8 Aircraft Crashes and Investigations [Part 6] Alistair, I suspect VEBill is thinking back to F-GFKC (where the systems protected the airframe from overload at the expense of failing to clear an obstacle). A. ### RE: Boeing 737 Max8 Aircraft Crashes and Investigations [Part 6] That's the not spooling up after the pilot did a stupid and illegal low pass and got down to 10ft on idle power on a runway that wasn't long enough for it to land on. All 40 ton+ jets at flight idle will touch the ground from 10ft if you do a go-around a 28500kg dash will never mind a jet. They were at alpha floor anyway because of doing the low slow fly pass if they had been allowed to lift the nose back anymore they would have hit the ground harder in a full stall. It didn't let them over load the airframe and put them into a stall. They didn't have any energy to climb because the engines were spooling up from idle which takes 5-6 seconds.... They were going to hit the ground what ever happened. Here is the accident report. https://reports.aviation-safety.net/1988/19880626-... ### RE: Boeing 737 Max8 Aircraft Crashes and Investigations [Part 6] #### Quote (VEBill) Lesson to be learned: automation requires more training, not less. Right. Operators (pilots in this case) have to know how things work in order to make it work properly, and also to be able to figure out why things aren't working. Some operators have more aptitude and therefore better understanding than others do. Training needs to clearly identify thresholds of necessary understanding and be able to detect when an operator just doesn't quite get it right. I know nothing about pilot training, but in my experience this exists across all markets and technologies. Brad Waybright It's all okay as long as it's okay. ### RE: Boeing 737 Max8 Aircraft Crashes and Investigations [Part 6] #### Quote (thebar3) I know nothing about pilot training, but in my experience this exists across all markets and technologies. Cases in point, the Uber and Tesla robotic driving accidents. "Schiefgehen wird, was schiefgehen kann" - das Murphygesetz ### RE: Boeing 737 Max8 Aircraft Crashes and Investigations [Part 6] China Airlines Flight 140 is an example where the A300 crash was attributed to pilot error, but there was a related software update that hadn't yet been installed. I've explained the common thread above: that the Airbus was in perfect mechanical condition in the millisecond before impact. There are many such examples. Attribution of these sorts of incidents to pilot error, especially where the pilots are experienced, rather supports my point. ### RE: Boeing 737 Max8 Aircraft Crashes and Investigations [Part 6] A300 is not fly by wire. It has no flight envelope protections. Its old school, the current Airbus FBW system with all the envelope protections was sort of fitted to a few of them towards the end but it didn't come in until the A320 in 1984. Quick google and it turns out that they hit toga by accident probably because the Captain had been flying 747 before and the AP didn't disconnect properly which there was a fix for already released but CA hadn't performed it yet. Funny actually because we spotted the same issue in these threads with the MAX and it got flagged to EASA and Boeing are having to fix it. If it wasn't for the two crashes they more than likely would have spotted it and also put the fix through the same way. Every single aircraft type in operation today has had a pilot take them into the ground when the aircraft is fully serviceable through not following SOP's or loosing situational awareness. Here is a A300 cockpit. Colgan Air Flight 3407 is an example from my own type the Q400. They stalled the aircraft and the Captain decided to pull back even more. Through the stick shaker, then through the stick push which requires over 45lbs pull (which I have never had to do in training I might add) and everyone died. US airline, US crew, US trained. There is a technique for the situation of elevator stall which is not mentioned in the Q400 manuals which does mean you have to pull back on the stick but while your doing that you put the flap back to where you have just moved it from. I got taught it by an old BAe Chief test pilot for the Jetstream 41. Never heard it mentioned before and never heard it mentioned since so I doubt that crew even knew about it. Some say it was a fault in the aircraft design that the tail fell off the A300 AA585 after the first officer did a good impression of doing "river dance" on the rudder pedals after a wake vortex encounter. Lots of noise after that one as well until they worked out that it had actually failed at 2.75 of the design load which had a safety factor of 1.5 applied to it. But AB had used a composite rudder and everyone said it only broke off because of that. After a few weeks they decided that it was the US technique of lifting the wing with rudder that was being taught to recover from flight upsets that was at fault. A couple of weeks after that Boeing changed all its type manuals to state cyclic inputs of rudder, elevator and ailerons would result in structural failure at under rough airspeed/Vma. Scary thing is there are still flight schools teaching lift the wing with the rudder. It sort of supports your point but every type has had the same issues with pilots. Its not unique to a particular make or type, country of operation, country that the pilots trained in, if they have lumpy jumpers or not, sexual preference or skin colour. ### RE: Boeing 737 Max8 Aircraft Crashes and Investigations [Part 6] #### Quote (AH) Colgan Air Flight 3407 is an example from my own type the Q400. They stalled the aircraft and the Captain decided to pull back even more. Through the stick shaker, then through the stick push which requires over 45lbs pull (which I have never had to do in training I might add) and everyone died. US airline, US crew, US trained. There is a technique for the situation of elevator stall which is not mentioned in the Q400 manuals which does mean you have to pull back on the stick but while your doing that you put the flap back to where you have just moved it from. I got taught it by an old BAe Chief test pilot for the Jetstream 41. Never heard it mentioned before and never heard it mentioned since so I doubt that crew even knew about it. That crash happened about 7 or 8 miles from my house, I live under the SW approach to BUF and the crash was on the NW approach. #### Quote (From the accident wikipedia) Following the clearance for final approach, landing gear and flaps (5 degrees) were extended. The flight data recorder (FDR) indicated the airspeed had slowed to 145 knots (269 km/h).[3] The captain then called for the flaps to be increased to 15 degrees. The airspeed continued to slow to 135 knots (250 km/h). Six seconds later, the aircraft's stick shaker activated, warning of an impending stall as the speed continued to slow to 131 knots (243 km/h). The captain responded by abruptly pulling back on the control column, followed by increasing thrust to 75% power, instead of lowering the nose and applying full power, which was the proper stall recovery technique. That improper action pitched the nose up even further, increasing both the g-load and the stall speed. The stick pusher activated ("The Q400 stick pusher applies an airplane-nose-down control column input to decrease the wing angle-of-attack [AOA] after an aerodynamic stall"),[3] but the captain overrode the stick pusher and continued pulling back on the control column. The first officer retracted the flaps without consulting the captain, making recovery even more difficult.[23] There was a lot in the local news about pilot fatigue and health because the FO had a bad cold and lived in washington state and took a flight across the lower 48 to nap in the crew lounge in new jersey for a bit before taking off as a co-pilot. The pilot had a bad training record and was chatting up the FO on approach and IIRC mentioned the SAAB 340 or some plane where the stall procedure was supposed to be pull the yoke instead of pushing it. The american fear of doctors and sick days probably figured into the FO's decision to fly sick. ### RE: Boeing 737 Max8 Aircraft Crashes and Investigations [Part 6] There is no aircraft that stall recovers by pulling back on the stick. Power is a bonus but even gliders can recover from a stall. Please though we are in an Engineering forum, don't use the term Stall speed it is meaningless. The only thing that stalls an aircraft is critical angle of attack exceedance. I can take you up and be doing 0 knots and not be stalled and I can also have you in the stall at Vne in an acrobatic aircraft. You will more than likely throw up somewhere in between the two events though. And its not the doctors that make US FO's fly. The whole payment system even up to Delta, AA mainstream crews is done by the flying hour. Hence the union taking legal action for damages to earnings in the US on Boeing. It also carries safety aspects because as a captain if you ground the aircraft then you loose pay because the flying hours are not completed. They don't get paid for days off, days on standby or for training. US regionals are full of pilots with bad training records. It the same in Europe as well but decreasing because the regionals are all going due to loco's. That doesn't mean the pilots are not flying. They just go and fly in Asia and Africa etc. You ask why are the regionals still flying these pilots? because basically they would shut down through lack of crew if they didn't. All the good crew move up the ladder ASAP. You might ask why I am still flying a crappy regional Q400. Because my roster and disposable income is better than my mate who flies A320 for Easyjet based out of Gatwick. I really don't care what I fly its all about quality of life these days. And his Terms and conditions are far better than working for British Airways. ### RE: Boeing 737 Max8 Aircraft Crashes and Investigations [Part 6] You can go edit the Wiki article if you don't like the quote. Still, my understanding is that AOA, speed and lift all work together, which means there certainly will be a stall speed for each particular AOA in an aircraft in its current configuration. Operating right at the critical AOA means the highest lift or lowest stall speed, or more simply the ability to keep successfully flying at the slowest speed. However, while flying at critical AOA and the lowest possible speed, any increase or decrease to AOA will reduce lift and the plane will drop. In other words, a change to the AOA away from critical requires more speed to not stall, which is what I believe the Wiki quote was describing. Even if the pilot had decreased AOA, the plane would still drop until enough speed was reached that enough lift was produced to keep the plane flying. ### RE: Boeing 737 Max8 Aircraft Crashes and Investigations [Part 6] Stall is when the airflow separates for the aerofoil. When this happens Cd increases significantly and Cl decreases significantly. There is only one critical angle of attack for each aerofoil. It doesn't vary with weight, or speed, gear down or up. It does though vary with flap setting because that changes the shape of the aerofoil. You think we always fly with the ground directly under us? Airframe reference coordinate system for lift and drag is completely different to ground coordinate system references. We can climb quite happily at 3o degrees nose up to the ground system but in reality we are only climbing at 10 deg AoA to the aircraft coordinate system. ### RE: Boeing 737 Max8 Aircraft Crashes and Investigations [Part 6] #### Quote (LionelHutz) ...my understanding is that AOA, speed and lift all work together, which means there certainly will be a stall speed for each particular AOA in an aircraft in its current configuration... Alistair is correct that stall is primarily linked to AOA, and only secondarily to speed (excepting transonic effects). Exceed the critical angle of attack, and the air unsticks from the upper surface and the wing stalls. Reduce the angle of attack and the air reattaches. The thing often referred to as "stall speed" is the speed at which the angle of attack required to produce enough lift to maintain 1g level flight at some load condition (usually maximum gross weight) is that at which the wing stalls. Any slower, and you can't support 1g flight because you can no longer increase the angle of attack. Your only choices are to either speed up or reduce the lift required by allowing the aircraft to accelerate downward (sub-1g flight). If you know a few things about the airplane in question you can easily use the pV^2 family of expressions to find the stall speed associated with every condition of lift and load factor (vertical acceleration). But it's a pretty pointless exercise; if you want to know if the wing is stalled it's easiest to just look at angle of attack: Below critical, not stalled. Above critical, stalled. His assertion that he can have an unstalled wing at 0 kts airspeed is easily demonstrated: In 0g flight the wing produces no lift and is essentially at 0 AOA, so the air happily sticks to wing and flows over it just fine. Or would if it were moving, like at a half knot or so. This is the condition encountered in a parabola or its subset the vertical climb. His assertion that he can have a stalled wing at Vne (never exceed speed) is perhaps true, but demands a very robust aerobatic airplane, as he suggests. By inspection of most airplane V-N diagrams, we see that Vne is well above the speed at which the critical angle of attack produces so much lift that it overstresses the airframe. However, there are exceptions, and I think the Boeing Stearman Model 75 trainer might be one of them. Make sure he uses one of those to demonstrate. And bring a neck brace. --Bob K. ### RE: Boeing 737 Max8 Aircraft Crashes and Investigations [Part 6] A wing doesn't go from producing maximum lift at the critical AOA to no lift the second you go past it. The airflow over the top of the wing doesn't suddenly change from being fully attached to completely separated. The airflow separates more and more as the AOA increases past critical. So, I would say airfoil stall would more precisely be when an increase in the AOA decreases lift, not when the flow over the airfoil is separated from the surface. Apparently, certification requires the manufacturer to publish the stall speeds for a bunch of different flight configurations (weights and flap positions). Each AOA in a specified configuration does have a minimum associated speed. You might say it's not the stall speed, but the end result is the same. Go to slow and the plane begins dropping out of the sky unless you either speed up or change the AOA to restore enough lift. Saying that stall can't happen at 0 speed is being rather pedantic, really worthy of nothing more than being a water cooler discussion. ### RE: Boeing 737 Max8 Aircraft Crashes and Investigations [Part 6] (OP) #### Quote: ...an unstalled wing at 0 kts airspeed is easily demonstrated: In 0g flight the wing produces no lift and is essentially at 0 AOA, so the air happily sticks to wing and flows over it just fine. Or would if it were moving, like at a half knot or so. This is the condition encountered in a parabola or its subset the vertical climb. An aircraft at any airspeed can do this. Such as the "vomit comet". The aircraft cannot have any lifting forces at the time it is following the ballistic trajectory, otherwise it would be accelerated - not the point of the flight. My flight instructor also demonstrated this to me. I knew exactly what was going on and all the math - but it was fascinating and memorable just the same. ### RE: Boeing 737 Max8 Aircraft Crashes and Investigations [Part 6] Here is a graph of some common types Cl V AoA note it includes 737-300 wing, the top curve is with flaps down slats out and the bottom one with sharp drop off is a clean wing. While your correct that it does not go to zero immediately after exceeding Alpha crit depending on the profile it can be quiet a vicious drop off. But the drop in CL is usually enough you start dropping like a brick. Training type aircraft such a Cessna 150/152/172 have extreme placid stall characteristics and its more of a leaf falling towards the ground than a brick falling off the top of a building. Every one thinks Bernoulli makes aircraft fly but there is a fair old lump of Newton reaction force in there as well as most wings have a 3-5 deg angle of incidence built in relative to the hull so in no way is it zero lift, just not enough to maintain altitude or tighten a turn (which is usually where stalls occur). Conversely the piper tomahawk PA38 which I did most of my instructing in was a vicious little bitch stalling. But I quickly realised that this produced a better more prepared pilot post PPL completion after they moved to more benign aircraft types such as the 4 seater C172 which just makes a screeching noise the nose doesn't drop and it wafts towards the ground at a slightly greater rate of decent than normal. The Tommy nose drops by 30 degs you usually get the wing dropping suddenly all very quickly after a couple of buffets. Designers have a few tricks to keep the airflow attached and move the initial stall point. They stick vortex generators on the top surface and they position them so the wing stalls at the root of the wing instead of the towards the tips or behind the alerions so you don't loose roll control in a stall. But with all these things if you design the wing for nice easy stalling you loose other KPI's . Commercial aircraft are built mostly for fuel economy, they have two stage stall protection run off the AoA sensors (which is why they were initially added to the design) You have the stick shaker going off at 8% to go to the stall and a stick pusher forcing the nose down at 5%. When you turn the icing protection on they automatically alter the protection Alpha critical to a lower value and the trigger points change correspondingly. As for the Vne speeds and stall Bob is correct for utility class aircraft you would bend the wings and the engine would cut out way before you reached stall speed. Extra, Steerman and a few others in the unlimited aerobatic class can do it although its extremely unpleasant even attempting it add most pilots will get G-LOC and release the back pressure on the controls before actually stalling. TO be honest outside acrobatic stupidity the main time this may be an issue and does happen is in a spiral dive or spin recovery. Some of these ultra light cat aircraft have quite low Vne with a cruise speed of 80-90 knots and a Vne of 130- 140kts. And once they dig themselves out of a spin they then end up pointing straight at the ground past Vne and pulling back on the stick with a dead mans grip. The poles in the wings bend, aircraft is written off, but most of the time the occupants survive. This discussion might seem off topic. But there is a strong suspicion that MCAS is a stall protection device. If it is deemed to be one because of dirty stall characteristics then the certification requirements for it is going to go through the roof. We won't get to find out until the other regulators get there hands on the aircraft for test flights. EASA will be testing the flight envelope with MCAS turned off and stall characteristics will part of those tests. And BTW the Steerman is a great aircraft to fly. Your wallet takes a huge hit though. It burns 50 ltrs an hour at 2$ a ltr in the UK. And that's just the fuel. Add on the dry rental price and you talking 500$an hour. Mucho fun though. But I am a family man these days so don't go near anything that burns petrol or get in a helicopter of any type of fuel. ### RE: Boeing 737 Max8 Aircraft Crashes and Investigations [Part 6] "There is only one critical angle of attack for each aerofoil." Wouldn't there be a 2nd one when the aircraft is upsidedown? e.g. A stunt aircraft making a level pass while inverted. ### RE: Boeing 737 Max8 Aircraft Crashes and Investigations [Part 6] :D I like it, and you are correct Inverted is beyond my knowledge. I just know that you get poo loads of drag and things can go very dangerous very quickly and you have to put opposite inputs in than usual to recover. And delta wings are a bit of a mystery as well. There is a new course that all commercial pilots have to do before their first multicrew rating Advanced upset prevention and recovery. Every time we are in the sim we do some form of wake vortex/ mountain wave upset recovery. But as its a new requirement and only applies before you do the first type rating I won't have to do this course which is in a single engine piston aerobatic type. ### RE: Boeing 737 Max8 Aircraft Crashes and Investigations [Part 6] AH: "Inverted is beyond my knowledge. I just know that you get poo loads of drag and things can go very dangerous very quickly and you have to put opposite inputs in than usual to recover." Even with a 747? Dik ### RE: Boeing 737 Max8 Aircraft Crashes and Investigations [Part 6] Are you thinking about the famous barrel roll flybys with the prototype 707? Barrel Roll Bill -------------------- "Why not the best?" Jimmy Carter ### RE: Boeing 737 Max8 Aircraft Crashes and Investigations [Part 6] This is where it becomes complicated to visualise Please see my comments above ref aircraft coordinate systems V ground reference system. Most aerobatic maneuverers are done at positive G which means lift is still for want of a better word is in the normal direction. A barrel roll and loop are both positive G manoeuvres so at no point is the aerofoil inverted even though the aircraft is upside down in relation to the ground. Its only when things are negative G that inverted aerofoil performance is occurring. ### RE: Boeing 737 Max8 Aircraft Crashes and Investigations [Part 6] ^That's not inverted 1g steady state that would give you a negative alpha. A barrel roll is a positive alpha case all the way around. Pouring water during a barrel roll: Link ### RE: Boeing 737 Max8 Aircraft Crashes and Investigations [Part 6] This lady is the world champion at aero's and I chose it because her hair is extremely good for seeing what forces are going on and when the aircraft is negative G. BTW her neck muscles must be like wire rope. She is pulling between +7 G and -2.5G during this display. Most people would black out. You can see her tense up before the heavy G pulls to trap blood in her head. https://youtu.be/AYrH_rELbf4 ### RE: Boeing 737 Max8 Aircraft Crashes and Investigations [Part 6] Does an aircraft lose a lot of altitude during a barrel roll or is it falling more forward than down? Bill -------------------- "Why not the best?" Jimmy Carter ### RE: Boeing 737 Max8 Aircraft Crashes and Investigations [Part 6] It should come out at the same alt as it goes in. You basically draw a circle round a reference marker with your nose. Pick a ref point 45 deg off the nose on the horizon. pitch up as you do start the roll input when your at the top your nose should be 45 deg above the horizon above the reference point. This is the lowest G loading of about 0.5g. The continue the rolling as you descend and when you get back to the same picture as you started every thing should be the same again. Gliders you loose maybe 200ft doing one. The amount of alt gained at mid point is a function of the roll rate. The main reason why most planes can't fly inverted or under negative G for any prolonged periods. Is nothing to do with the flight dynamics of the surfaces. It because the engines need fitted with special oil and fuel systems to keep them running. Commercial aircraft can do Barrel rolls as well but its not normal and not trained for. Concorde apparently did one on its test flight after getting the rubber tank protectors fitted with the head of UK CAA test pilot at the controls and the BA Concorde fleet chief pilot in the other seat. ### RE: Boeing 737 Max8 Aircraft Crashes and Investigations [Part 6] While all this is good stuff and very interesting, I think we need to remember why we're here discussing this. The 737 MAX was designed around new, larger, more powerful yet more fuel efficient engines. They didn't fit in the space available from the 737NG for historical design reasons. Thus the engines were placed further forward and higher than other similar aircraft. This has an impact on the flying characteristics of the plane, especially in high AoA situations whereby the control forces become lower as the AoA increases. The 737 is a power assisted aircraft, much the same way as power assisted steering on a car. Like a car, the forces being fed back to the operator (pilot/driver) increase as the forces on the item in question increase. Other design (FBW) is to be a fully powered system which divorces pilot / driver input and runs it through a set of computers to decide what to make the control surfaces do. Thus those units need to be very reliable. So for a car, to take an analogy, as you enter a bend and start to turn, if keeping a constant speed, the force to decrease the turn radius gets harder and harder until something finally gives and the car under or over steers. Same thing with the plane while increasing AoA. As I understand it this is the "rule" for this type of operation. This doesn't happen in the 737MAX and hence they introduced an artificial modification which mimics the same feedback. However the reliability of this needs to be very high to operate when it is supposed to and not when it isn't. So is it a stall protection device? I think it is very close to that myself (though what do I know?). It still won't prevent a stall if the pilot just keeps pulling back, but at least he or she won't do it by accident as the stick forces reduce, which is counter intuitive and counter "normal" operation. There are other things coming out into the open but if they haven't really got a reliable solution for the key underlying issue yet then it makes you wonder if they ever will. Remember - More details = better answers Also: If you get a response it's polite to respond to it. ### RE: Boeing 737 Max8 Aircraft Crashes and Investigations [Part 6] According to Boeing; " MCAS is NOT a stall prevention system. It is only there to prevent unexpected stalling." If you can not say that convincingly you will not make it in Boeing management. After some contradictory information about how the 737 elevators work and study of the elevator control diagram I believe the following is correct: With the hydraulic system working properly, there is no feedback whatsoever on the elevator linkage. It is full hydraulic power. The only force on the control cables is the force required to operate a hydraulic valve against the centering springs. As the elevator moves the valve moves so although there is no force feedback there is position feedback. The force on the stick is generated by the force computer which uses hydraulic pressure to apply a graduated force to the stick to mimic a direct mechanical feedback. In the event of a complete hydraulic failure, There will be a force transmitted back to the stick via the linkage. This increases the force on a fulcrum in the linkage system. The fulcrum is movable and is connected to the elevator trim tabs. With a complete hydraulic pressure failure the trim tabs are able to move the elevator against the normal operating hydraulics. As the rudder moves due to trim tab action, the valve moves with it and so there is still position feedback as well as force feedback from the direct action of the trim tabs. This is not that important in regards to the crashes as the hydraulic systems were functioning and the force computer had ample hydraulic pressure available to generate the extreme forces on the stick. It would have probably made the plane more flyable if they had adjusted the proportional band of the force control computer so that the forces were still proportional but about 50% of what they are now in the Max and probably in the NG. In perfect hindsight, how about this for a memory item. In the event of repeated, unexpected nose down trim caused by a failure of the MCAS system, turn off the main STAB TRIM switches. Restore trim manually. In the event that the aerodynamic forces on the stabilizer are too great to allow manual trimming the following procedure may be used to trim the stabilizer electrically. WARNING When the STAB TRIM switch is turned on, MCAS will reactivate in 5 seconds and/or will activate 5 seconds after the column switch is released. To trim electrically, the STAB TRIM may be turned on and a correction made with the column switch within 5 seconds. The STAB TRIM switch must be turned off within 5 seconds of releasing the column stabilizer switch. Alternatively. The column switch may be held in the direction that it is desired to move the STABILIZER TRIM, and the trim activated by momentarily turning the main STAB TRIM on and off. IN THE EVENT OF UNWANTED, REPEATED NOSE DOWN TRIM EVENTS THE MAIN STAB TRIM SWITCHES MUST NOT BE LEFT ON FOR MORE THAN 5 SECONDS. The pilots in the second crash may have been about to figure this out. All except the 5 second "Gottcha". With more altitude they would probably have survived. Unwilling martyrs to the correction of a flawed system, both mechanical and regulatory. That information, shared with pilots in a timely manner would have avoided the second crash, and so would have avoided the groundings and worldwide re-certification. That may well have triggered sim training and cost Boeing a few hundred million in rebates, while saving a few billions and a reputation and the loss of future sales. Any potential customer weighing the choice between Airbus and Boeing will most likely go airbus. Bill -------------------- "Why not the best?" Jimmy Carter ### RE: Boeing 737 Max8 Aircraft Crashes and Investigations [Part 6] I'm very happy to be proved wrong in my understanding of how the elevators work and the force feedback, but this doesn't quite gel with the requirement for MCAS in the first place. My understanding was that the issue was that the stick force required to increase AoA did not increase with AoA as required by the certification rules. Remember - More details = better answers Also: If you get a response it's polite to respond to it. ### RE: Boeing 737 Max8 Aircraft Crashes and Investigations [Part 6] This is my understanding. The MCAS original design intent was to provide the correct "feel" to mimic the 737NG's stick, which would minimize the amount of retraining. On top of that was the part that FUBARed the two planes, which was to force the nose down if there was excess AoA, based on issues encountered during testing. Because MCAS depended on only one of the two available AoA sensors to determine its behavior, a single point failure would cause the MCAS to do what it did. TTFN (ta ta for now) I can do absolutely anything. I'm an expert! https://www.youtube.com/watch?v=BKorP55Aqvg FAQ731-376: Eng-Tips.com Forum Policies forum1529: Translation Assistance for Engineers Entire Forum list http://www.eng-tips.com/forumlist.cfm ### RE: Boeing 737 Max8 Aircraft Crashes and Investigations [Part 6] ...and it seems to get more interesting: "Internal emails from Boeing staff members working on the 737 MAX were made public earlier this month have revealed new safety problems for the company's flagship 777X, a long-range, wide-body, twin-engine passenger jet, currently in development that is expected to replace the aging 777-200LR and 777-300ER fleets, reported The Telegraph. Already, damning emails released via a U.S. Senate probe describes problems during the MAX development and qualification process. The emails also highlight how Boeing employees were troubled by the 777X – could be vulnerable to technical issues." Dik ### RE: Boeing 737 Max8 Aircraft Crashes and Investigations [Part 6] Seeing that management changes have only been made recently, it seems likely that the 737 MAX issues would be systemic and therefore have metastasized into other programs. My only wonder is how was the 787 spared (or was it)? Brad Waybright It's all okay as long as it's okay. ### RE: Boeing 737 Max8 Aircraft Crashes and Investigations [Part 6] It wasn't, the batteries are still causing issues on the 787. There is also issues with the lightning protection of the composite panels. ### RE: Boeing 737 Max8 Aircraft Crashes and Investigations [Part 6] I'm aware of the battery problem, but I think that is discrete and different from the problems with the 737 MAX and (alledgedly) the 777X programs where it seems that Boeing obfuscated and obscured information from the FAA for systems that they knew were not what they were claimed to be, and apparently realized was poorly designed, at least in the 737's case. I guess I wasn't privy to the composite lightning protection design until you just pointed it out. It seems Boeing needs to organize a new department of "what to do, what to do..." Brad Waybright It's all okay as long as it's okay. ### RE: Boeing 737 Max8 Aircraft Crashes and Investigations [Part 6] RE: Is it an anti-stall system I think this is why 737 max 8 sim models, and until the crashes happened, the existence of MCAS were kept as confidential as possible. With the boeing 'pilot as the ultimate authority' philosophy, stick/yoke feedback is more critical than with an FBW system with programmed attitude, alpha and speed limits because stick feedback is a proxy for the stick feel that a pilot would have with unpowered controls, and would be a cue for the pilot about a/c performance. If you ask 'what does an anti-stall system do?' Signals impending stall and modifies aircraft configuration or pilot input to prevent passing critical alpha. some answers could be: Prompts pilot about impending stall (stall horn, stick shaker) Modifies/prevents pilot input that would stall a/c (alpha limiter, stick pusher) Modifies wing to change stall characteristics based on alpha or airspeed.(automatic slats passive on rollers like A-4, actuated like F-16, both change wing camber and alpha) Autothrottle linked to alpha or airspeed to maintain margin on stall speed at 1g, steady state airspeed MCAS was added as a patch because at high alpha (unknown how high?, how near critical alpha?) the stick feel was not sufficiently increasing in proportion to alpha. Or was it alpha was no longer linearly reponsive to to elevator input? Since it's full hydraulic this begs the question 'couldn't they modify the artificial feel unit instead?'. Taken at face value, since stick feel is a stall avoidance input to the pilot, if it looks like a duck and quacks like a duck, it's a duck. ### RE: Boeing 737 Max8 Aircraft Crashes and Investigations [Part 6] (OP) You've all got the picture, AFAIK. It's not about the stall or the angle of stall, it's about the slope of the curve approaching stall that's non-linear. Without a feedback system, a pilot could pull back by 1 inch with added 1 pound of force to keep it back, but the next 1 inch back would take <1 pound to hold. If at some point you can pull back another inch with nearly zero additional force, then the control feedback vanishes and the confusion begins. Pull it back 1 more inch, and you will need -1 pound to keep it there, and now confusion rules. This figure was posted here many months ago but since the topic has come back... It shows that the feedback is linear but not at high angle of attack. Nose-down is positive in airplane pitching moment terms, so that's why the trend goes down (nose-up). The graph also shows the complication of the MCAS adjustment that puts the feedback force back closer to the original linear trend. As with any non-PID feedback control, using discrete lumps of negative feedback leads to zig-zag trend lines. ### RE: Boeing 737 Max8 Aircraft Crashes and Investigations [Part 6] LittleInch. The point is that there is no force feedback in normal flight. The force on the stick is generated artificially by the force computer. A dependable AoA signal could have been used to bias the force computer. The force on the stick relative to the elevator deflection could have easily been adjusted to much less and still been proportional in accordance with the regulations. Bill -------------------- "Why not the best?" Jimmy Carter ### RE: Boeing 737 Max8 Aircraft Crashes and Investigations [Part 6] Apart from the artificial restrictions on the MCAS, such as avoiding sim training, is there any requirement for a uniform stick feel on all aircraft? Would the FAA allow an aircraft to fly with 1/2 of the stick force of a similar but different model plane? Is there any regulatory requirement for the high forces on the stick that MAX pilots experience when fighting off a MAC attack? Bill -------------------- "Why not the best?" Jimmy Carter ### RE: Boeing 737 Max8 Aircraft Crashes and Investigations [Part 6] To some degree, I would think that one wants relatively uniform behavior across all planes a pilot is certified to fly; otherwise one runs the risk of the pilot expecting one behavior in an emergency, but getting something different, failed to respond correctly. I have much more trivial issues with cruise control activation across the different cars I drive, because they are different. TTFN (ta ta for now) I can do absolutely anything. I'm an expert! https://www.youtube.com/watch?v=BKorP55Aqvg FAQ731-376: Eng-Tips.com Forum Policies forum1529: Translation Assistance for Engineers Entire Forum list http://www.eng-tips.com/forumlist.cfm ### RE: Boeing 737 Max8 Aircraft Crashes and Investigations [Part 6] (OP) #### Quote (FAA, FAR 25) 25.173 Static longitudinal stability. [Under the conditions specified in Sec. 25.175, the characteristics of the elevator control forces (including friction) must be as follow: (a) A pull must be required to obtain and maintain speeds below the specified trim speed, and a push must be required to obtain and maintain speeds above the specified trim speed. This must be shown at any speed that can be obtained except speeds higher than the landing gear or wing flap operating limit speeds or VFC / MFC , whichever is appropriate, or lower than the minimum speed for steady unstalled flight. (b) The airspeed must return to within 10 percent of the original trim speed for the climb, approach, and landing conditions specified in Sec. 25.175 (a), (c), and (d), and must return to within 7.5 percent of the original trim speed for the cruising condition specified in Sec. 25.175(b), when the control force is slowly released from any speed within the range specified in paragraph (a) of this section. (c) The average gradient of the stable slope of the stick force versus speed curve may not be less than 1 pound for each 6 knots. (d) Within the free return speed range specified in paragraph (b) of this section, it is permissible for the airplane, without control forces, to stabilize on speeds above or below the desired trim speeds if exceptional attention on the part of the pilot is not required to return to and maintain the desired trim speed and altitude.] Amdt. 25-7, Eff. 11/14/65 #### Quote (FAA FAR 25) Sec. 25.175 Demonstration of static longitudinal stability. Static longitudinal stability must be shown as follows: (a) Climb. The stick force curve must have a stable slope at speeds between 85 and 115 percent of the speed at which the airplane-- (1) Is trimmed, with-- (i) Wing flaps retracted; (ii) Landing gear retracted; (iii) Maximum takeoff weight; and (iv) 75 percent of maximum continuous power for reciprocating engines or the maximum power or thrust selected by the applicant as an operating limitation for use during climb for turbine engines; and (2) Is trimmed at the speed for best rate-of-climb except that the speed need not be less than 1.3 VSR1. (b) Cruise. Static longitudinal stability must be shown in the cruise condition as follows: (1) With the landing gear retracted at high speed, the stick force curve must have a stable slope at all speeds within a range which is the greater of 15 percent of the trim speed plus the resulting free return speed range, or 50 knots plus the resulting free return speed range, above and below the trim speed (except that the speed range need not include speeds less than 1.3 VSR1, nor speeds greater than , nor speeds that require a stick force of more than 50 pounds), with-- (i) The wing flaps retracted; (ii) The center of gravity in the most adverse position (see Sec. 25.27); (iii) The most critical weight between the maximum takeoff and maximum landing weights; (iv) 75 percent of maximum continuous power for reciprocating engines or, for turbine engines, the maximum cruising power selected by the applicant as an operating limitation (see Sec. 25.1521), except that the power need not exceed that required at / ; and (v) The airplane trimmed for level flight with the power required in paragraph (b)(1)(iv) above. (2) With the landing gear retracted at low speed, the stick force curve must have a stable slope at all speeds within a range which is the greater of 15 percent of the trim speed plus the resulting free return speed range, or 50 knots plus the resulting free return speed range, above and below the trim speed (except that the speed range need not include speeds less than 1.3 VSR1,nor speeds greater than the minimum speed of the applicable speed range prescribed in paragraph (b)(1), nor speeds that require a stick force of more than 50 pounds), with-- (i) Wing flaps, center of gravity position, and weight as specified in paragraph (b)(1) of this section; (ii) Power required for level flight at a speed equal to (VMO + 1.3 VSR1)/2 and (iii) The airplane trimmed for level flight with the power required in paragraph (b)(2)(ii) of this section. (3) With the landing gear extended, the stick force curve must have a stable slope at all speeds within a range which is the greater of 15 percent of the trim speed plus the resulting free return speed range, or 50 knots plus the resulting free return speed range, above and below the trim speed (except that the speed range need not include speeds less than 1.3 VSR1 , nor speeds greater than VLE, nor speeds that require a stick force of more than 50 pounds), with-- (i) Wing flap, center of gravity position, and weight as specified in paragraph (b)(1) of this section; (ii) 75 percent of maximum continuous power for reciprocating engines or, for turbine engines, the maximum cruising power selected by the applicant as an operating limitation, except that the power need not exceed that required for level flight at VLE ; and (iii) The aircraft trimmed for level flight with the power required in paragraph (b)(3)(ii) of this section. (c) Approach. The stick force curve must have a stable slope at speeds between VSW , and 1.7 VSR1 , with-- (1) Wing flaps in the approach position; (2) Landing gear retracted; (3) Maximum landing weight; and (4) The airplane trimmed at 1.3 VSR1, with enough power to maintain level flight at this speed. (d) Landing. The stick force curve must have a stable slope, and the stick force may not exceed 80 pounds, at speeds between VSW and 1.7 VSRO with-- (1) Wing flaps in the landing position; (2) Landing gear extended; (3) Maximum landing weight; [(4) The airplane trimmed at 1.3 VSRO with-- (i) Power or thrust off, and (ii) Power or thrust for level flight.] (5) The airplane trimmed at 1.3 VSRO with power or thrust off. Amdt. 25-115, Eff. 8/2/2004 ### RE: Boeing 737 Max8 Aircraft Crashes and Investigations [Part 6] Thank you Spar. I recognize the effort you have expended. May I impose on you and ask for an explanation of this: #### Quote (FAA REgs) (c) The average gradient of the stable slope of the stick force versus speed curve may not be less than 1 pound for each 6 knots When an aircraft is cruising in a trimmed condition and the force on the stick is basically zero, how is this reg applied? Bill -------------------- "Why not the best?" Jimmy Carter ### RE: Boeing 737 Max8 Aircraft Crashes and Investigations [Part 6] You change the speed by 6 knts then measure the force on the stick. ### RE: Boeing 737 Max8 Aircraft Crashes and Investigations [Part 6] Thanks Alistair. Bill -------------------- "Why not the best?" Jimmy Carter ### RE: Boeing 737 Max8 Aircraft Crashes and Investigations [Part 6] Ok, I got this wrong. The issue as I see it now isn't so much the feel of the stick and elevator ( which is more artificial than I anticipated ) as the fact that as you get to about 10 degrees AoA the position of the stick is no longer proportional to what the airplane wants to do. i.e. up to about 10 degrees as you pull the stick back for every inch you get a similar effect in terms of AoA. The issue is that above 10 degree this effect changes and for every further inch back the plane stops responding in the same way and the elevator has a lower effect than before. Hence for the same amount of stick movement the AoA increase faster. So to make the plane respond in the manner sparweb quotes, they needed to counter the lift being generated by the engine nacelles and the way they chose was to use the large stabiliser to counter this and allow the elevator to be the sole/ main input into increasing AoA. My main point is that this is so fundamental to the design of the aircraft that given its age of design and lack of the required reliability of the control systems compared to true FBW machines, that there may not be a solution i its current form. Remember - More details = better answers Also: If you get a response it's polite to respond to it. ### RE: Boeing 737 Max8 Aircraft Crashes and Investigations [Part 6] How about this: AoA sensors and reliability: How about a two point calibration check and agreement check before each flight? WOW! Over the top. Completely unrealistic, right? That may be a lot easier and a lot simpler than you think. When the plane leaves the gate, both AoA sensors will be pointing straight down. Easy to automatically check the position each time the plane leaves the gate. Easy to check agreement. Next check: As the plane approaches takeoff speed, the AoA sensors will be horizontal. Again easy to check the position and agreement. A third check may be done to compare the point at which the AoA sensors begin to move. That will check mechanical binding and freedom of movement. An automatic, two point calibration and freedom of movement check each time the aircraft leaves the gate. Now what do we do with this signal? There will be a signal coming to the stick force generator from the force computer. A suitably conditioned AoA signal may be used to bias that signal and continue to increase the stick force with increasing AoA. How do we know which AoA sensor to use? Easy, use both. A circuit as simple as two diodes may be used to select the higher of two signals. Alternately, and remember that the stick shaker and alarms will be going off to alert the pilot that he is approaching a stall. He is already at a bad AoA. Use both signals compounded. The AoA signal conditioners can be set so that the primary sensor leads the secondary sensor by a few degrees. This added force may violate the proportional force rule, but the pilot has already continued to increase his AoA despite alarms, the stick shaker and the increased stick force. More stick push-back may not be a bad thing and may be accepted by the regulators. It has a lot of KISS going for it. Bird strikes: That may be easy to recognize. A flock of birds. A thump. Immediate, increased stick force. The plane is still controllable. A three position switch, left, both and right. Cut out either but not both AoA sensors. Let the pilot fly the plane. KISS And, by the way, restore the stabilizer control circuits to the original NG configuration. Step 1. Approval in principle from the regulators. Step 2. World wide headlines: MCAS IS GONE REGULATORS APPROVE MAX 8 FIX WITHOUT MCAS PRODUCTION TO RESTART IMMEDIATELY Step 3. Rewire the controls on the existing fleet back to NG configuration may start within days. Production may restart slowly and efficiently. Think of any objections as engineering challenges to be met rather than reasons that it will not work. Bill -------------------- "Why not the best?" Jimmy Carter ### RE: Boeing 737 Max8 Aircraft Crashes and Investigations [Part 6] There is multiple solutions now they have ditched the iPad training. Only problem is which one is quickest to get through certification and costs the least to retro fit to 500 airframes already built. ### RE: Boeing 737 Max8 Aircraft Crashes and Investigations [Part 6] It looks as if Boeing is pursuing band-aids on band-aids on band-aids, with MCAS being the first band-aid. Bill -------------------- "Why not the best?" Jimmy Carter ### RE: Boeing 737 Max8 Aircraft Crashes and Investigations [Part 6] AH: "Only problem is which one is quickest to get through certification..." Looking through my dad's old log books; he was a pilot for the RCAF during the last war. There are numerous certifications for different aircraft, and it appears the time involved was a day or less... planes must have been a lot simpler back then... Dik ### RE: Boeing 737 Max8 Aircraft Crashes and Investigations [Part 6] They could fly a new plane after reading the pilot notes in the bar over lunch in the 2nd ww. And swap between single engine spits one day and multi engined bombers the next. And they weren't simple aircraft to pilot. But system wise they were. But they had a large brutal failure rate compared to today. Certification in the context I was using is the aircraft not the pilot type rating. ### RE: Boeing 737 Max8 Aircraft Crashes and Investigations [Part 6] AH: what bar... at the beginning of the war it was de-icer fluid... pure ethyl alcohol... then the air force denatured it by adding a toxic additive... and it came in 40 gal drums... with the oxygen masks... they sobered up pretty quick. Dik ### RE: Boeing 737 Max8 Aircraft Crashes and Investigations [Part 6] Weren't flying paying passengers, either. The problem with sloppy work is that the supply FAR EXCEEDS the demand ### RE: Boeing 737 Max8 Aircraft Crashes and Investigations [Part 6] Seems there is a clash of Regulators now over the wiring loom possibility of short circuits in the tail. FAA and Boeing say its fine as they are and have a powerpoint presentation to prove it. EASA says move them. FAA is going to release a statement next month on the subject. Which I presume won't occur until there is some form of financial result declaration at the same time. ### RE: Boeing 737 Max8 Aircraft Crashes and Investigations [Part 6] Alistair: They have a PowerPoint proving all is fine? Well, then <sarcasm on> I just don't see how EASA has any reason to gripe! <sarcasm off> FYI I truly enjoy your posts and since I caught a whiff of your sarcasm in this one, I thought I would just push the noise level up a bit. ### RE: Boeing 737 Max8 Aircraft Crashes and Investigations [Part 6] Thanks, it seems to be a feature of being Captain. Those that don't seem to have healthy dose of it seem to suffer health wise. Must act as a stress release. I found the site when the Miami bridge collapsed. And found good intelligent educated comments, which is somewhat of a rarity on the internet these days. PPrune when I started flying was the same but in the last 10 years has rapidly lost its professional educated members and seems to be mostly populated by wannabies, spotters, self loading freight, reporters and walts. I haven't gone near it in years. The rotary section is still populated by those that know what they are talking about. And rotary pilots levels of sarcasm is leagues ahead of fixed wing. Having not practised as a mech eng for 17 years now I felt I wasn't in position to add anything. This thread came up and I felt I could add to the discussion with technical input. So I joined up. Its actually very good for me to interact with designers and those that are practising. I have learned a lot from the discussions as well. Thanks to you all with a special mention for Sparweb who has corrected my deviations from course and provides the raw regulation for certification. ### RE: Boeing 737 Max8 Aircraft Crashes and Investigations [Part 6] (OP) #### Quote (Alistair Heaton) self loading freight And thanks to you for the useful terminology! LOL ### RE: Boeing 737 Max8 Aircraft Crashes and Investigations [Part 6] and an appreciation from the audience... Dik ### RE: Boeing 737 Max8 Aircraft Crashes and Investigations [Part 6] My favourite quote from the above article: #### Quote (N.T.S.B. said “there should be confidence in the integrity” of its participation in the initial investigation of the 2009 crash, insisting that its work was always “independent, transparent and free from bias.”) The B.S. meter is hitting the red line of that. It is pretty damn impossible to be completely to ever "“independent, transparent and free from bias" let alone ALWAYS be spot. At best complete arrogance, at worse actively covering up past mistakes. Likewise their refusal to participate doesn't suggest transparency. Hey. Maybe NTSB is beyond reproach and have performed perfectly. (Unlikely given the recent issues) But even so in the current climate they need to rebuild the trust of the international community for their own benefit. ### RE: Boeing 737 Max8 Aircraft Crashes and Investigations [Part 6] The h*ll of it is that they know that, but voice it anyway. It further detracts from their credibility. Dik ### RE: Boeing 737 Max8 Aircraft Crashes and Investigations [Part 6] Sounds like NTSB's 2009 report is pining for the fjords. ### RE: Boeing 737 Max8 Aircraft Crashes and Investigations [Part 6] It's got beautiful plumage! ### RE: Boeing 737 Max8 Aircraft Crashes and Investigations [Part 6] (OP) #### Quote (Sidney Dekker, Report Of The Flight Crew Human Factors Investigation, July 2009) Post-accident manufacturer recommendations that, in effect, tell flight crews to mistrust their machine and to stare harder at it not only mismatch decades of human factors and automation research, but also leave a single-failure pathway in place. Wow, the contempt is palpable. This report is an informative and entertaining read. There is a significant degree of disgust expressed by the author almost everywhere with the system design's fault tolerance, which was exposed in this case. #### Quote (New York Times; Feb. 6, 2020) In (...) the 2009 crash, which involved a 737 NG, Boeing’s design decisions allowed a single malfunctioning sensor to trigger a powerful computer command, even though the plane was equipped with two sensors. (...) the company had determined that if a sensor failed, pilots would recognize the problem and recover the plane. But Boeing did not provide pilots with key information that could have helped them counteract the automation error. This sounds strangely familiar! ### RE: Boeing 737 Max8 Aircraft Crashes and Investigations [Part 6] It's seems they have been getting away with this single sensor onto primary flight controls automation for 20 odd years. You can see why the design shop could do very little about it with the max even if they thought it was stupid. O well I am sure they have saved several million over the years by doing so. Many bonuses which can't be reclaimed will have been paid. More than likely the originator of this practice is now dead through old age. Running estimated cost of the max grounding is 19 billion$ to Boeing alone. Now production is shut down the are now starting to calculate the cost to the economy and third party suppliers. I have a gut feel it will end up in the region of 50 billion after it's all sorted out all in.

And now Boeing needs to produce at least two clean sheet designs in the next 10 years and start thinking about a 737 replacement clean sheet.

### RE: Boeing 737 Max8 Aircraft Crashes and Investigations [Part 6]

H'mm wonder if they only had one clock on the space rocket....

And only one sensor to say if the service module is still attached....

### RE: Boeing 737 Max8 Aircraft Crashes and Investigations [Part 6]

#### Quote (Alistair_Heaton)

It's seems they have been getting away with this single sensorIt's seems they have been getting away with this single sensor onto primary flight controls automation for 20 odd years. onto primary flight controls automation for 20 odd years.

From what I can see it is all part of the grandfathering process that going on since 1967 so potentially over 50 years. From something I read the flight computers still used are Intel 80286. That computer processor is from 1982!!

Having two separate completely independent flight computers reading separate sensors, processing separately and outputting separately is great redundancy when the pilot is the one in control and is simply wanting reliable data. Shoehorning autopilot or even worse flight envelope protection that can't be readily turn off onto is far from ideal.

### RE: Boeing 737 Max8 Aircraft Crashes and Investigations [Part 6]

It's not though

Along with speed trim system it was new to the Ng.

The Ng has a raft of things that were duplicate systems that were condensed down to single.

It used to have two motors on the trim stab jack screw. One was only for the pilots electric trim and the other for aircraft systems input.

Radalt would have only needed to be used by the autothrust when autolanding was required which again was new to the NG.

The 500's are apparently bullet proof and everyone knows how they work and how to deal with there vices. NG is a completely different aircraft system wise.

### RE: Boeing 737 Max8 Aircraft Crashes and Investigations [Part 6]

The use of the 80286 is apparently because after that the processors went multi threaded and it's exponentially harder to certify the system if it's multi threaded software.

I don't have much of a clue to be honest on the system software and hardware certification. All I know is that there are two standards. One is for when failure means nobody dies. And second one is for catastrophic. Boeing so far because the pilot was argued to be always to be able to spot an issue and solve it in 3 seconds has gone for the none catastrophic certification.

https://en.m.wikipedia.org/wiki/DO-178B

You will more than likely understand it better than I do.

### RE: Boeing 737 Max8 Aircraft Crashes and Investigations [Part 6]

Threading isn't processor, it's software. You could still run single thread software on new processors if you wanted to. There were/are newer processors that are still single core.

### RE: Boeing 737 Max8 Aircraft Crashes and Investigations [Part 6]

Nevertheless, unless the 286 is being overtaxed, using such a processor might actually be safer, since it's an orders of magnitude simpler design, and therefore, simpler to test and validate. Today's processors could go through years of testing without necessarily even verifying that all possible "stuck-at" faults can be found.

TTFN (ta ta for now)
I can do absolutely anything. I'm an expert! https://www.youtube.com/watch?v=BKorP55Aqvg
FAQ731-376: Eng-Tips.com Forum Policies forum1529: Translation Assistance for Engineers Entire Forum list http://www.eng-tips.com/forumlist.cfm

### RE: Boeing 737 Max8 Aircraft Crashes and Investigations [Part 6]

Weren't there reports last year that there was evidence the 286 was being overtaxed during simulations/testing? I recall seeing articles that, while the 286 was perfectly adequate in previous iterations, the addition of MCAS and other software appears to be pushing it beyond it's limits.

Not sure what the outcome of those reports was, since they haven't changed processors yet.

Example Article

### RE: Boeing 737 Max8 Aircraft Crashes and Investigations [Part 6]

Nevertheless, it's a well-qualified part with literally millions of hours of actual reliability data.

We used to source metal-gate PMOS telecom parts until we decided to screw the pooch that laid nearly golden eggs; we actually out-sourced everything but printing our own logo and part number on the parts and still made 90% margin, and our infinitely-wise GM forced last-time buys. The reason they were so profitable was that they, likewise, were fully qualified and had gobs of reliability history, which is often hard to come by.

These were 6-micron PMOS parts being built when 2-micron CMOS parts were already get a bit long in the tooth.

TTFN (ta ta for now)
I can do absolutely anything. I'm an expert! https://www.youtube.com/watch?v=BKorP55Aqvg
FAQ731-376: Eng-Tips.com Forum Policies forum1529: Translation Assistance for Engineers Entire Forum list http://www.eng-tips.com/forumlist.cfm

### RE: Boeing 737 Max8 Aircraft Crashes and Investigations [Part 6]

#### Quote (Quote)

Weren't there reports last year that there was evidence the 286 was being overtaxed during simulations/testing? I recall seeing articles that, while the 286 was perfectly adequate in previous iterations, the addition of MCAS and other software appears to be pushing it beyond it's limits.

I read similar, but I haven’t seen any concrete claims that the 80286 is actually underpowered and that it has anything to do with the failures.

### RE: Boeing 737 Max8 Aircraft Crashes and Investigations [Part 6]

Since I brought up the discussion of the use of Intel 286s, I just wanted to say that by no means was I suggesting this was inadequate for its task just because of its age. (I'm in no position to judge.) All I wanted to do was highlight just how much they have grandfathered keeping the same processing unit while still adding on additional software tweaks.

### RE: Boeing 737 Max8 Aircraft Crashes and Investigations [Part 6]

Understood, but coincidentally there were reports that it may be under powered in the Max. Presumably they've found a workaround or the reports were exaggerated since Boeing hasn't had to commit to switching processors yet, as far as I'm aware.

### RE: Boeing 737 Max8 Aircraft Crashes and Investigations [Part 6]

Boeing will probably just try to overclock them....

### RE: Boeing 737 Max8 Aircraft Crashes and Investigations [Part 6]

A colleague of mine attempted to control a lumber sorter in a sawmill with an 8080.
Making a couple of outputs a second sounds easy, but there was a critical size.
As the size of the sorter increased there were more sorting bins and more choices, including keeping track of the number of pieces in each bin and diverting to an alternate bin while a bin was being emptied.
Too much information.
The boards arrived at a steady rate.
The 8080 would start missing boards in a large sorter.
Lumber sorters reverted to the old discrete logic gates until faster chips with more than 8 bits were developed.
As tasks are added, there is a real possibility that a task may not be completed in a timely manner.
A missed task in a lumber sorter meant that a board would ride the chain to the end and then drop on the ground.
Not a good thing for an airplane.
Looking at the input from one sensor and generating an output is one thing.
Looking at and comparing the outputs from three sensors, and also checking for rapid changing signals adds much computing time.
This all added to a computer that may be quite busy already.

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

### RE: Boeing 737 Max8 Aircraft Crashes and Investigations [Part 6]

A little bit of digging found these gems

https://www.palisadeshudson.com/2019/07/is-ancient...

Here's the blog is listed

https://www.moonofalabama.org/2019/06/boeings-soft...

Some of the comments below the article add something to the issue.

A new one
https://www.theverge.com/2020/2/6/21126364/boeing-...

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

### RE: Boeing 737 Max8 Aircraft Crashes and Investigations [Part 6]

Great articles LI... I was surprised a financial outfit had noted the processor issue.

Dik

### RE: Boeing 737 Max8 Aircraft Crashes and Investigations [Part 6]

From LittleInche's linked article:

#### Quote (THE WALL STREET JOURNAL)

Boeing Loses MAX Deal to Airbus
Saudi airline says it will buy up to 50 Airbus jets, worth more than $5.5 billion AND #### Quote (MOON OF ALABAMA) Some decades ago your host programmed special input device drivers for Intel 80286 and alike systems. Their purpose was to record and process data from industrial process sensors, often hundreds at a time. Performance and timing issues required that the 80286 input drivers had be written in low level assembler language. But even with extremely optimized code the system would eventually come to its limits. The delayed procession of data from one sensor would eventually cascade into further delays and in the end the system would fail to record and process anything. The task was simply above its physical limits. Bill -------------------- "Why not the best?" Jimmy Carter ### RE: Boeing 737 Max8 Aircraft Crashes and Investigations [Part 6] Are they saying it could have been too much for the processors to do a more complex and thorough assessment of multiple sensors? ### RE: Boeing 737 Max8 Aircraft Crashes and Investigations [Part 6] Modern processors might prove to be unsuitable for many aircraft. Cosmic radiation goes up with altitude. Modern processor have much smaller transistor size (Moore's Law), and are more susceptible to upset. It's a complex subject, and in the conservative engineering of aerospace there is a tendency to reuse what has proven reliable before. When applications leave earth, and full radiation-hardened processors are needed, the computing power tends to lag decades behind current consumer products. The Curiosity Rover on Mars uses a Rad hardened variation of the PowerPC processor that Apple introduced in products in 1991. ### RE: Boeing 737 Max8 Aircraft Crashes and Investigations [Part 6] #### Quote (Tomfh) Are they saying it could have been too much for the processors to do a more complex and thorough assessment of multiple sensors? Yes. From the days of industrial use of the 8080 processor and the TRASH 80. Tandy RAdio SHack 80. Bill -------------------- "Why not the best?" Jimmy Carter ### RE: Boeing 737 Max8 Aircraft Crashes and Investigations [Part 6] Seems the FAA are getting slammed for the Air Southwest oversight. 88 planes were brought into the N reg and they managed to sign off 70 planes in one day as compliant. It normally takes 3-5 people going through the aircraft paperwork 2 days per aircraft up until 10 years old, and an extra day for every 5 years over 10. ### RE: Boeing 737 Max8 Aircraft Crashes and Investigations [Part 6] AH: Another government agency that has been marginalised. Dik ### RE: Boeing 737 Max8 Aircraft Crashes and Investigations [Part 6] It's unfortunate that they couldn't migrate the 286 to the 386DX, with internal floating point, which would have simplified the processing. Feature sizes on the 286 are probably around 200 times bigger than the feature sizes on a current generation Snapdragon processor. However, the throughput is on the order of 4000 times higher, which could allow for triple modular redundancy in the processor software to easily deal with single event upsets, along with running full ECC on the data. TTFN (ta ta for now) I can do absolutely anything. I'm an expert! https://www.youtube.com/watch?v=BKorP55Aqvg FAQ731-376: Eng-Tips.com Forum Policies forum1529: Translation Assistance for Engineers Entire Forum list http://www.eng-tips.com/forumlist.cfm ### RE: Boeing 737 Max8 Aircraft Crashes and Investigations [Part 6] I seem to remember from a few threads back that its the internal floating point which makes it so extremely hard to certify ### RE: Boeing 737 Max8 Aircraft Crashes and Investigations [Part 6] Not sure there's that much difference between the 287 and the 386 internal FPU. The older FPUs are likely to be substantially less complicated than, say, the Pentium FPU, which had microcode errors. TTFN (ta ta for now) I can do absolutely anything. I'm an expert! https://www.youtube.com/watch?v=BKorP55Aqvg FAQ731-376: Eng-Tips.com Forum Policies forum1529: Translation Assistance for Engineers Entire Forum list http://www.eng-tips.com/forumlist.cfm ### RE: Boeing 737 Max8 Aircraft Crashes and Investigations [Part 6] I think it comes down to the culture at Boeing, from the managers through the board of directors to the owners. If we can't grandfather it, we won't do it. So we get a 35 year old processor in a 50 year old airframe. Bill -------------------- "Why not the best?" Jimmy Carter ### RE: Boeing 737 Max8 Aircraft Crashes and Investigations [Part 6] Since the company's board is driving this, they have to start making them personally liable. Dik ### RE: Boeing 737 Max8 Aircraft Crashes and Investigations [Part 6] I'm sure they'll be fined some absurdly small amount and maybe have to do community service. ### RE: Boeing 737 Max8 Aircraft Crashes and Investigations [Part 6] I agree with both dik and RVAmeche. Their lost and cancelled sales and payouts to airlines will be the rel punishment. They have probably paid out over a billion already in settlements to airlines. From the reports it is not clear if these settlements are for 2019 with more to come or if they are final settlements. If these settlements are for 2019 alone, the final total may be double or more. More information on settlements and lost sales at this link. Did Boeing Just Pay American Airlines More Than$500 Million To Settle 2019 MAX Claims?

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

### RE: Boeing 737 Max8 Aircraft Crashes and Investigations [Part 6]

Is it just a coincidence that American and Alaska have just announced Alaska joining the OneWorld alliance... do you suppose AA has some Machiavellian scheme for commandeering Alaska's fleet to backfill for the missing Max's?

"Schiefgehen wird, was schiefgehen kann" - das Murphygesetz

### RE: Boeing 737 Max8 Aircraft Crashes and Investigations [Part 6]

That is an interesting idea, so I took a look at their fleets.
From Wiki:
American Airlines
American is the largest operator of the Airbus A320 family in the world.[1][n 1] It operates the largest fleet of A321 aircraft, and the largest A319 fleet in the world.
American operates 945 aircraft.
Of those, 304 are 737-800s flying.
24 Max-8s are grounded and 76 Max-8s are on order.
American also has 56 Airbus A321neos on order and 50 Airbus A321XLRs for delivery from 2023 to 2025.
So 100 planes out of 945 is worrisome but probably survivable.

Alaska Airlines
Excluding freight and subsidiaries airlines, Alaska operates 234 Aircraft.
Of those, 163 are 737 types.
On order are 32 737 MAX-9s, overdue since June 2019.
As well, on order are 30 Airbus A320neos.
With 32 aircraft missing from a fleet of 234, Alaska's percentage is a little worse than American's, but probably survivable.
I suspect that the deal will benefit both airlines through code sharing.

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

### RE: Boeing 737 Max8 Aircraft Crashes and Investigations [Part 6]

https://www.seattletimes.com/business/boeing-aeros...

Word from EASa side of things it doesn't matter what the FAA agree to its going to get sorted....

The chaffing nonsense is utter bollocks they can leave the original wires in place and cut them at both ends and then reroute new ones and take the 2 kg hit to the dry operating weight. this is standard bollocks with logo light wiring.

Another thing in the mix is this nonsense over aircraft tariffs, they have already stop production of and there is production plants already up and running to get round the tariffs anyway. And the tariffs only hit the USA consumers. And even if American airlines wanted to buy US produce they have shut the production down anyway..... So the airlines have the choice of pay up or not have any new planes and pay the hit in fuel.

And because the US is refusing to appoint for the WTO courts nothing can get sorted out anyway. And the case against Boeing which every man and his dog knows is going to go the same way as the airbus one is due out soon but no appeal court to process the appeal. Not that it matters because Boeing can't deliver anyway.

https://www.seattletimes.com/business/boeing-aeros...

What a stupid mess.

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