Boeing 737 Max8 Aircraft Crashes and Investigations [Part 3] 36

[Sparweb]

This is the continuation from:

thread815-445840
thread815-450258

This topic is broken into multiple threads due to the long length to be scrolled, and many 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.


Some key references:

Ethiopian CAA preliminary report

Indonesian National Transportation Safety Committee preliminary report

The Boeing 737 Technical Site

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

 

[SwinnyGG]

It is the engineer's role to make things work.

Uh... it most certainly is not.

The engineer's job, first and foremost, to ensure the safety of life. Period. Any other approach is irresponsible.

'Just make it work' is the exact attitude that lead to the situation Boeing is now in.

Has it become obvious that MCAS, assuming it were the root cause, will never work no matter how much engineering is thrown at it?

No, I don't believe that has become obvious, and I don't believe that to be true. I don't think anyone who is knowledgeable about this situation thinks that either.

 

[saikee119]

I have been with this thread long enough to know landing gear limitation. I thought LittleInch has put it to bed.

Because the landing gear needs to retract.
Longer gear need a bigger hole in the plane which isn't there.
Longer gear has more drag so impacts landing and take offs.
Longer gear will create larger moment forces from the braked wheels needing stiffer mounts.

Sorry if I exhibit too much respect to others' design. Over the years I come to respect designer's arrangement irrespective how good or how bad it is. For a bad design it is easier for me to find faults and shortcomings. The bottom line is, when I am charged with reviewing a designer's work, it has to work as stated.

I believe the real problem of 737 Max isn’t its engineering but the shattering of our confidence in its manufacturer.

The original intention of hiding MCAS, the resulting faults so fundamental to safety, the amount of bad and risky arrangements in the flight control system now laid bare in front of the public, the delay of admitting and fixing the fault that might have saved the second crash, the hoodwink from the initial claim of making a safe plane even safer and its relationship with FAA to get certification are something much deep rooted and may take a very long time to put right if that can be done at all.

Whenever I traveled for business in the past I was in a Boeing plane more often than I was not. Now suddenly that manufacturer no longer the hallmark for safety and engineering quality. It is like one discovering a bank cheats one’s deposit. In this case the manufacturer renowned of safety is suddenly found putting lives at risk!

 

[saikee119]

jgKRI ,

your last implies Boeing will not be able to fix MCAS so we either have new 737 Max without it or no future 737 Max at all. Is my interpretation correct?

It is difficult to find an acceptable working design that is unsafe in structural engineering. May be in mechanical an unsafe design can be accepted as a workable solution. I suppose a consumer can always purchase a badly designed product that can endanger its end user but I wouldn't say such product works because its design intent has not been fulfilled.

 

[RVAmeche]

I don't doubt Boeing will experience some effects from less consumer confidence, but I don't think you can say there are no other legitimate problems with the plane? Obviously we'll see what the final reports conclude.

MCAS as it was originally designed and implemented only looked at one AoA sensor at a time and had no ability to ignore erroneous data. That's not a good design. Not to mention the minimal pilot training (or even awareness of the system prior to the first crash).

 

[SwinnyGG]

your last implies Boeing will not be able to fix MCAS so we either have new 737 Max without it or no future 737 Max at all. Is my interpretation correct?

No.

What I said implies that I think MCAS as a concept is fixable, if proper engineering processes and controls are applied.

There's only three real 'endgames' available to Boeing here:

1) MCAS is 'fixed' or replaced by a supplementary system that performs the same function but in an acceptable way

2) Boeing removes the Max 8 from the market, and does not offer a high efficiency narrow body jet to compete directly with the 320neo

3) Boeing re-designs the Max 8 wing, landing gear, and fuselage to accommodate a conventional engine placement (negating the adverse aerodynamic effects of the relocated engines and negating the need for MCAS entirely). This triggers re-certification of the airframe and all that entails.

Numbers 2 and 3 are not an option for Boeing.

 

[IRstuff]

"The engineer's job, first and foremost, to ensure the safety of life. Period. Any other approach is irresponsible."

This is a rather absolutist view of engineering. The fact that you have to leave the ground, riding on a tank of aviation fuel, in the company of turbines spinning at high speeds, with wings that have to flex and change shape, imposes many conflicting requirements against safety of life. No engineer, nor company, can afford to design something that is absolutely safe, since it's likely that such a craft would either be too heavy to take off, or only carry a much smaller amount of cargo. We don't see many airplanes with redundant landing gear, albeit most have some level of manual control, and there is a risk analysis associated with that was deemed to be acceptable. The McDonnell Douglas DC-10 had a fatal flaw that passed through such a risk analysis; its tail engine turbine failed and flung turbine blades through the one place in the plane where there was no redundancy for the flight control hydraulics, resulting in the loss 111 passengers, and had it not been for the fact that an FI was on board as a passenger, the entire plane might have been lost.

The engineer's job is to design, to the best of their abilities, for a calculated and acceptable risk. The design/risk analysis process failed in this case; sadly, though, this is often how processes get improved. As with certain other failures, this is how we wind up with realistic risk probabilities and consequences to do the next risk analysis.

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

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[Alistair_Heaton]

There is a load more...

To be honest it's spiral argument everything revolves round not triggering recertification. And not triggering differences training in the SIM or new type rating due cost the customer.

Once the customer hits training costs then a change in OEM is on the cards. And the single isle medium haul market is huge.

Loosing 5 years certifing a new type when the only opersition has something already flying with 20% fuel savings means your dead in that market and will struggle to recover you market share as type ratings die only 2 years after you flew a type.

Its this grandfather certification trigger which is causing the issue. I am pretty sure the design engineers would have preferred not have had to bodge a software fudge instead of doing it properly. But that would have meant tripling the development costs and at least doubling the timeline.

 

[LittleInch]

This incident and design though has definitely shone a Grade A searchlight into places previously kept pretty much in the dark apart from those dealing with it on a day to day basis, i.e. the FAA oversight (or lack thereof) and certification. That is a much bigger issue and the forming of the Joint Authorities Technical Review which hasn't yet started and could be a very difficult beast to please.

This is what the 737 technical site says ( I assume they mean will meet for the first time on ....)
and is a direct copy of the FAA news site

https://www.faa.gov/news/updates/?n...mai6lDb0DzJiRPC17PieI4puPn8B58p_eVBOjHxXJ53nQ

"Joint Authorities Technical Review panel

The JATR panel was convened by the FAA and first met on 29 April 2019. The FAA said about the JATR: “The JATR team will conduct a comprehensive review of the certification of the aircraft’s automated flight control system, The team will evaluate aspects of the 737 Max automated flight control system, including its design and pilots’ interaction with the system, to determine its compliance with all applicable regulations and to identify future enhancements that might be needed.”


The JATR is led by veteran NTSB investigator, Chris Hart and has is comprised of representatives from the civil aviation authorities of Australia, Brazil, Canada, China, the European Union, Japan, Indonesia, Singapore and United Arab Emirates.

The group is expected to take up to 90 days to conclude, which suggests that the 737 Max will be grounded until at least August."

So not just the MCAS software patch but the entire flight control system and design,

And also certain practices like charging a phenomenal amount of money for "extras" like the AoA indication and AoA disagree light and reliance on single instruments.

My money is on an eventual return to service, but it could be the end of 2019 and might decide it needs sim training or extra mods.

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

 

[waross]

Alistair; Thank you for your patience and courteous replies.
We I am trying to work through the 5 whys, or as many whys as needed.
Another old trouble shooting maxim: Don't fight the problem.
I agree that the 737 is a great airplane, until the Max series.
Design is often a compromise. Adding engines that won't fit under the wings involved compromise.
Please bear with me as I ask some more silly questions.
Why did they want to use the Leap engines.
I understand they burned less fuel. That is acceptable.
Yes the use of those engines involved compromise. Instead of defending a system that has cost over 300 lives, destroyed two planes and resulted in a world wide grounding of a fleet of new aircraft, can we explore the idea that MCAS may not have been the best compromise?
I have asked a number of questions. Not all the first answers are holding up.
How many billions of flight hours have been accumulated by the existing 737 fleet without the problems of the Max8?
The landing gear on the Max10 only extends on rotation.
It is higher and it will fit in the wheel wells. Don't fight the problem. Try harder.
I am not saying that longer landing gear is the solution. I am pointing out that MCAS may not be the only solution.
Does the Airbus have over wing exits?
How much extra weight is involved in the longer pylons to mount the Leap engines in the new position? A good part of over 2000kg.
Link
"The MAX is approximately 3,000kg heavier than its equivalent NG. This all stems from the LEAP1B engines each of which are 385kg heavier than the CFM56-7. This extra weight requires stronger (and therefore heavier) engine struts, wings, fuselage and landing gear."
Comments on the credibility of this site are welcome.
What's in a word? I may have been in error in choosing the words "inherently unstable" to describe a flight characteristic that is outside the flight envelope that is accepted by the FAA.
I am suggesting that there may be sound engineering solutions to correcting the flight characteristics without implementing MCAS.
I am suggesting that the focus on MCAS is an unreasonably narrow view point that may preventing the consideration of a solution of the original problem, in which case the MCAS will become a moot issue.
Pop quiz in regards to longer landing gear:
Why won't it work?
How can we make it work?
Pick one.

A quote from an engineer and pilot who knows very much more than I about aircraft.

The should stop any more interations of the 737 using the old certification grandfather rights which is based on a 1960's design.

New certification to modern standards not just fundging things so they don't have to comply with modern standards or do a full certification testing program.

Note the limiting dimension on engine size may be the fan diameter. The Leap engine fan has an increased diameter of 8.4 inches over the NG engines. That would seem to be within the possibilities of longer landing gear.
Please consider that MCAS may be covering a symptom rather than the root cause.


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

 

[saikee119]

I never share Boeing's optimism of fixing just the MCAS would cut it.

The FAA credibility is now at stake and it covers its back side by dragging more people into the firing line. The JATR would therefore want to know if the 737 Max has other issues in the flight control so the entire system will be looked at bits by bits, section by sections, module by module and the way the whole thing is put together. This is a good development but the process could slow down 737 Max returning to service.

So instead of being certified by itself Boeing now has to bite the bullet to satisfy other aviation authorities that 737 Max is safe to fly. Technically it is a brilliant idea as Boeing will no longer be able to hide something like MCAS again, the certification cost is shared out internationally and ultimately the plane should be safer with more parties involved in its review.

 

[saikee119]

waross,

Despite the two fatal crashes 737 Max had been flying more than a year with over 350 operating world wide. If the AoA sensor did not fail in the last two cashed plane we probably would not know MCAS's short coming for a while yet.

The two plane crashes do not make the public suddenly become better plane designer than Boeing.

This Forum provides opportunity to exchange ideas. Our combined effort and technical knowledge can peel off the problem layer by layer so that mistake is understood.

To re-design any part of the 737 Max one needs access to many information and constraints which are not available to the public.

 

[RVAmeche]

From an outsider's perspective, it seems like something like this was somewhat inevitable due to the self certification and heavy avoidance of reclassifying the plane at all costs. As it's been discussed in the previous threads, these planes (not just the 737 MAX) have been upgraded heavily since their initial release. This iteration finally pushed it over the limit.

 

[IRstuff]

Actually, I think even spatulas have gone through some iterations, because there are those of us that often use spatulas to cook things, and burning spatula material is not conducive to human health, even if it were wood and not some sort of plastic.

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

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[djhurayt]

what do you mean IR, the spatula is the best tasting part of my cooking

 

[Alistair_Heaton]

The main issue is not a Boeing issue it's more a regulatory issue.

And the issue is not an FAA issue, it's all the regulators.

And the cost of the joint committee will be paid for by Boeing not the regulators. They will all be staying in 5 star hotels with first class transport home every week for two days off. Early knock off Friday and late start Monday. This cost will either be passed onto the unit cost or taken as an accounting hit. Every single minute spent on it will be billed to Boeing.

I will not comment on the technicalities of changing the gear. Just don't know enough about the ins and outs of it.

What I do know is that fuel accounts for 80% of every airlines variable costs. If you can reduce that by 20% by flying a certain type compared to your competitors then you can under cut them and the consumer will always go for the lowest price ticket. You just need to under cut them by 1% so you remain in profit and they are not covering costs and they will be out of business inside 6 months.

They can hedge fuel for a year, after that then oil fluctuations can add insult to injury.

I burn 5 tons a day 20 days a month on average all year round. That's 5200 tons of fuel a year on a 72 seat turbo prop.

632$ a ton that's 3 239 000 $ per year. We have 3 crews per aircraft. So call it 10 million $ per aircraft. 20 % saving per aircraft 2 million. We have over 10 of my type....

A fleet of 100 neo's against 100 ng's 800 your talking 350 million $ difference in variable operating costs for fuel alone in a year. That will easily pay for 600 type ratings plus tech ratings which is in the region of 25 million.

 

[WKTaylor]

I'd bet a few $$ that Boeing was leaning on the MCAS to stabilize the MAX without adding the two 'draggy' wide-ventral-fins that were added onto the 737AEW&C [E-7 Wedgetail], lower-aft fuselage.

It appears these wide-span ventral fins were added to this 737 variant to enhance aero-stability at extreme-AoA due to [mostly] destabilizing effects of the 'wide-blade' antenna on the upper-aft cabin... on what 'looks' like a shorter body 737

Regards, Wil Taylor

o Trust - But Verify!
o We believe to be true what we prefer to be true. [Unknown]
o For those who believe, no proof is required; for those who cannot believe, no proof is possible. [variation,Stuart Chase]
o Unfortunately, in science what You 'believe' is irrelevant. ["Orion", Homebuiltairplanes.com forum]

 

[saikee119]

And the cost of the joint committee will be paid for by Boeing not the regulators. They will all be staying in 5 star hotels with first class transport home every week for two days off. Early knock off Friday and late start Monday. This cost will either be passed onto the unit cost or taken as an accounting hit. Every single minute spent on it will be billed to Boeing.

I find this hard to believe as it implies even FAA has been fully paid by Boeing to certify their planes. In that case Boeing owns all the aviation regulators' representatives in the JATR.

I would have thought the JATR representatives would be salaried staff from foreign regulators and their work and visits will be paid by the foreign regulators who can an arrangement with FAA. I don't believe the public would accept the time, accommodation and all expenses of certifying a plane is the plane manufacturer's liability as in such case the FAA can operate with a zero budget and has no necessity to ask for funding from the Congress.

If Boeing has to pay every minute of time for the FAA staff to certify their plane that might have driven Boeing to go for the grandfather certification to minimize the cost and indirectly contributed the two plane crashes.

 

[charliealphabravo]

I'd bet a few $$ that Boeing was leaning on the MCAS to stabilize the MAX without adding the two 'draggy' wide-ventral-fins that were added onto the 737AEW&C [E-7 Wedgetail], lower-aft fuselage.

I've always wondered at how few control and stabilizing surfaces were on commercial airliners. I'd imagine that there are many stability and safety benefits to various unused stabilizer technologies and control surface redundancies that could make airframes an order of magnitude safer. I'm sure it is mostly due to matters of fuel efficiency which is a sad trade off.

 

[Alistair_Heaton]

Yes the OEM's pay for everything with certification by the regulator. They provide the test data and then the regulator used to sign it off. Now keeping a load of suitably experienced and qualified certifiers on pay roll is highly expensive and they are not used that much. So the regulators don't want to pay for it. So they try and shift the certification signatures to the OEM's and reduce the payroll. The OEM's always complain about the costs of certification so are more than happy to allow an employee to make the signature and then have paper work checks that all the required documentation has been done. So the regulator takes on more of a box ticking exercise than an actual engineering certification role.


FAA is only one regulator. They have to convince all the others as well unless they are happy with the max flying internal in US airspace. The others used to accept FAA certification now that's not the case.


Some 20 odd years ago when you had a ramp inspection it was an experienced pilot with ATP/ATPL and a licensed engineer that did the check. These days its a admin ops person who has been trained up what documentation to check and someone that sort of knows what an aircraft looks like and is more interested in various stickers and service dates on lifejackets and fire extinguishers than knows the difference between a hydraulic weep and a leak. Getting a clean inspection quiet often is a gauge of the Captains Bullshitting skills than compliance.

Its the same with air operators certificates. The company wanting one is liable for every minute spent on it. Something wrong in your manuals a revesion notice is issued and you pay for them to look at the manuals again.

Last AOC I was involved in getting it was 1.5 million UK pounds for an A to B limited to europe operations for a Saab 2000 sized aircraft . World wide operating and your looking at another half a million.

 

[Sparweb]

As far as I know, the FAA and EASA have drastically different cost of doing business.
The FAA represents the interests of one nation, based on the economic value of aviation industry that benefits that same nation. So fees for certification work are generally low or non-existent for many services. This is well aligned with the economic philosophy of the USA.
EASA represents dozens of nations, so the cost of its administration is covered partly by national contributions and partly by fees paid by the users. No single nation benefits, so no single nation would volunteer to pay for it all. And there are lots of things they want you to pay for. You might say that this, too, is well aligned with the economic philosophies prevalent in Europe.

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