Keep talking about the software. Make it about the software, so no one knows the airframe is fundamentally flawed..
Yaw dampers are workload mitigation devices; not compensatory for design flaws. Dutch roll is inherent to any controllable aircraft. Violation of 25.173 in the form of decreasing stick force response curves on approach to stall is absolutely not the same beast.
Design criteria are prescriptive, and I'm not aware of any line of regulation that says an uncertifiable airframe can be made certifiable by the addition of a computer. These handling characteristics are not undesirable, they are uncertifiable according to regulations as written, and intended.
Even Airbus meets these minimum design criteria at their minimum automation threshold. Boeing for some daft reason seems to be being written a pass to selectively ignore regulations around Civil Transport Aircraft certification based on some serious levels of sunk-cost fallacy.
I don't believe in supporting limp-wristed minimal compliance when it comes to safety critical engineering. Not going the route of designing out the behavior requires the implementation of system after system, after system to compensate, with each link in the chain adding additional risk for failure over and above what doing it right in the first place would have created.
Whitewashing wins no one but Boeing anything. Please remember that. We entrust these people to design and manufacture safer, more efficient, machines. Instead of living up to that mission, they jeopardized it in the name of optimizing the revenue/profit generating characteristics of the company.
I get the reluctance to throw away a potentially recoverable airframe, but I'm dead against letting anyone whitewash over the fact the plane is more dangerous than it needed to be because someone wanted better numbers on their held stock, and was willing to put a more dangerous product on the market in able to do it.
There has never been been an accident due to the airframe's pitch instability and MCAS not accomplishing its intended function. Both of the accidents happened because the MCAS system itself failed and activated when it shouldn't have.
If they had made a reliable MCAS (by which I mean the whole system from sensors to controls to actuation and pilot interface), there would have been no problem.
Regardless, this still seems like the right path (recertification). It seems the FAA is still being strong armed by Boeing. Why? Put these people in prison. Shut the 737 Max down. Make Boeing face the music. They need to fail to get the point, apparently.
Boeing have essentially painted themselves into a very costly corner. The FAA or congress could do a "certify it just for Boeing" action and the plane might even, maybe be safe then. But how many airline customers would want to fly in it?
Yes, a replacement of the 737 is more than overdue, but it is also 10 years away. A rushed new design could be way more dangerous than the known design of the 737.
I do hope Ralph Nader sues the pants off Boeing for killing his goddaughter due to their cheapness and shoddy products.
Please stop perpetuating evening time TV show fearmongering bullshit.
The eli5 explanation of the MAX 8 MCAS incident is as follows:
* Boeing wanted MAX 8 to have the 737 type rating. This means it must handle and fly just like other 737. This would allow existing 737 pilots to fly the MAX 8 with no additional training. This was part of Boeing's financial advantage.
* To achieve the efficiency it has, the MAX 8 has pretty large engines. Because they wanted to keep the airframe like other 737, they couldn't lift the wings to accommodate. Instead they moved the engines closer to the body.
* Moving the engines closer to the body increased the pitch-up characteristic at high AOA. Not so much as to make the plane unsafe (the 757 has a more aggressive pitch-up characteristic). But enough to make it sufficiently different from other 737 to invalidate the type rating.
* Boeing adds MCAS to augment the pitch-up and make it handle like other 737. They get their type rating.
* MCAS software validation happens with the assumptions that it's not a flight critical system, so constraints are relaxed. It passes.
* Flight testing reveals that MCAS needs significantly more pitch authority to do its job. It's updated to get that pitch authority. MCAS now becomes a flight critical system after these changes, but is not re-evaluated as one.
The airframe is fine. If Boeing gives up the 737 type rating and drops MCAS, they could have the fleet back in the air within a few weeks after pilots train for it. It just would cost their clients a lot more than originally promised and be a financial disaster.
https://www.youtube.com/watch?v=CD0JabYjF3A&t=
https://www.quora.com/Is-the-737-Max-supercritical-that-is-i...
The 737 MAX was designed so as to keep the type rating. The design would be different, and very likely fundamentally safer if keeping the 737 type rating were not a goal. A perverse incentive from the start. So I would not dismiss the claim that the 737 is "fundamentally flawed."
There's a million things that went wrong with the MAX 8 debacle, serious things that need to be addressed after the industry takes a hard look at itself. But there being something wrong with the airframe isn't amongst them. That meme has no grounds, isn't supported by anyone at all in the industry, and originated from clickbait spamblogs and late night tv shows that feed off FUD.
> The design would be different, and very likely fundamentally safer if keeping the 737 type rating were not a goal
Errrr. The design is may not be maximally optimal (what does that even mean?) because of type rating pressure, therefore the design is fundamentally flawed? Please stop. You're perpetuating clickspam driven fake news and distracting from the real problems.
Really?
Would you like to supply some names, or provide some whitepaper for that?
https://www.seattletimes.com/seattle-news/times-watchdog/the...
Btw, the entire cause for MCAS being implemented is a desperate attempt to comply with FAR 25.173. If the non-certifiable behavior hadn't been there, there would not have been an issue.
But wait, there's more!
https://www.nytimes.com/2019/07/27/business/boeing-737-max-f...
So we even have severe concerns over whether Boeing overstepped bounds in the safety process by approving their control line setup in spite of FAA concerns anyway.
Some gems from that.
>F.A.A. managers conceded that the Max “does not meet” agency guidelines “for protecting flight controls,” according to an agency document. But in another document, they added that they had to consider whether any requested changes would interfere with Boeing’s timeline. The managers wrote that it would be “impractical at this late point in the program,” for the company to resolve the issue. Mr. Duven at the F.A.A. also said the decision was based on the safety record of the plane.
>Engineers at the agency were demoralized, the two agency employees said. One engineer submitted an anonymous complaint to an internal F.A.A. safety board, which was reviewed by The Times.
>“During meetings regarding this issue the cost to Boeing to upgrade the design was discussed,” the engineer wrote. “The comment was made that there may be better places for Boeing to spend their safety dollars.”
>An F.A.A. panel investigated the complaint. It found managers siding with Boeing had created “an environment of mistrust that hampers the ability of the agency to work effectively,” the panel said in a 2017 report, which was reviewed by The Times. The panel cautioned against allowing Boeing to handle this kind of approval, saying “the company has a vested interest in minimizing costs and schedule impact.”
>By then, the panel’s findings were moot. Managers at the agency had already given Boeing the right to approve the cables, and they were installed on the Max.
So, forgive me if I question the veracity of "most in the industry have figured it isn't a big deal", and even if they have, I question whether or not that decision comes from some level of just wanting to return to business as usual with minimum interruption or action/further regulation based on the coming to light of the scale of regulatory capture that has been uncovered by this debacle.
The physics and presence of MCAS at all don't lie. The plane could not be certified without it. Personally, I deem an airframe to only encompass the physical structure without automation, and that assumption seems to be well received by those I know who have worked in aviation circles previously.
Given that when I raise concerns with them, I universally get some variation of "what the hell were they thinking?," I'm not terribly willing to accept that a large portion of the active industry is necessarily making the most impartial judgement given that their livelihoods may very well be adversely effected by the fiscal failure of this plane.
My sources include a former safety investigator/tech, and someone who worked with a maintenance squadron. So make of that what you will.
Furthermore, I'm willing to tolerate some leniency with stretching regulations a bit, but not to the extent of normalizing deviance for the sake of expediency. Down that road lies too much catastrophe.
Now I'll admit, I was one of the early central repeaters of the artificial feel system theory; I didn't have access to good technical docs, but apparently someone at the Seattle Times was able to find some corroboration, but I've done my damnedest to keep my reasoning constrained to my enthusiast level understanding of aerospace engineering and aviation, which has been rapidly expanding in my efforts to understand how something like this could happen in an industrial vertical famous for it's capacity to generate some of the safest machines on the planet. Just that reasoning alone is enough to at least get me questioning the sanity of the design decisions that have transpired w.r.t the MAX.
This isn't FUD. People need to pay attention.
https://news.ycombinator.com/threads?id=salawat&next=2043595...
Also, it’s the ‘airframe is fundamentally flawed’ meme. That’s an important difference.
1) The 737 MAX is a perfectly viable airplane without the MCAS, whose sole purpose is to not invalidate the type rating;
2) The 737 MAX has dangerous, uncertifiable flight characteristics without the MCAS; namely, the stick force gradient inverts at high angles of attack. One comment[1] in this thread has even linked the relevant legislation[2].
So, which is it?
[1] https://news.ycombinator.com/item?id=20607242 [2] https://www.law.cornell.edu/cfr/text/14/25.173
It’s realistic to build aircraft where software is required to fly said aircraft depending on the flight dynamics, and the pilot(s) are fully aware of what’s running. But that changes the type rating and blows Boeing’s regulatory sidestep out of the sky.
Flight computers are a fundamental part of normal aeronautical design.
Asking Boeing to fly a Max without MCAS would be like asking you to write a bug free C++ program... with a compiler with no error messages or validation.
https://en.wikipedia.org/wiki/Air_France_Flight_296
https://www.telegraph.co.uk/technology/9231855/Air-France-Fl...
The following planes (among others) all translate flight inputs. Airbus A320, A330, A340, A350, A380; Boeing 777. https://en.m.wikipedia.org/wiki/Flight_control_modes
A non-Max 737 doesn't need MCAS because it already behaves like a 737.
Essentially, most replies on this boil down to people being shocked (shocked!) that computers are currently helping all planes fly. I'm not sure how they thought AEs were getting efficiency gains while physics stayed the same...
Hundreds of people were killed due to a bad implementation of a deeply irresponsible and insensible approach to make money by skirting flight safety regulation. The bad implementation was in part software, but nobody is confusing that aspect with the whole picture.
The 737 MAX does not need MCAS. Nothing needs MCAS. Boeing executives wanted the money that MCAS made them.
If that were the case, then you'd see people debating the relative merits of SDLC approaches and organizational blinders to letting bugs slip through.
In reality, that's only about 20% of any Boeing discussion.
80% is outrage about how Boeing could have released such an "obviously flawed" airplane that required flight computer adjustments. And misunderstanding that Boeing pivoted from a clean sheet design to instead build exactly what the carriers asked them to.
Generally, HN comments are pretty good, but the amount of kneejerking in Boeing threads in lieu of informed discussion is terrible.
Edit: Although reading through new replies this morning, it's nice to see voting mostly sorted the technical wheat from the chaff.
If I read this correctly you're implying a 737 Max doesn't behave, aerodynamically, as that a non-Max 737 does? And if we follow that line of thinking since non-Max 737 don't require MCAS to behave appropriately then the 737 Max is not a 737 airframe and it should be recertified as something else, no?
I'm in no way "shocked" computers fly and/or help fly airplanes. I am shocked so many comments defend the gross negligence by Boeing, however.
Remember that in all of the needless death the 737 Max is attributed with absolutely zero deaths were because of a flight computer. The real root cause of the 737 Max crashes are Boeing executives and FAA personnel making cognizant choices to allow process to be skipped in the vain of profits and loss avoidance. I believe we'll see this, at some point, no different than the commonly referenced Challenger failure [0].
[0] https://www.breakingthewheel.com/root-cause-analysis-five-wh...
Sophisticated flight computers are only necessary for aircrafts that are inheritenly unstable (fighter jets) that require special flight characteristics.
Safe commercial, and private aircraft are built to be inheritenly stable. It's less complexity.
Sure we've added fly by wire, or dynamic power controls. But those are relatively straight forward.
Changing the center of gravity of the plane and therefore introducing different (dangerous, risky, and unsafe) flight charectierstics is a major issue.
Depending on how exactly you define it, pilot error is either the #1 or #2 cause of commercial plane crashes. FBW systems seek to reduce or eliminate that.
Auto-trim has been around for years, and failures are usually more annoying than serious. But the 737 MAX's auto-trim had far too much control authority, and was being used to compensate for bad handling characteristics, making it a flight critical system.
Google the 'Murray Gell-Mann Amnesia effect'.
Edit: https://en.m.wikipedia.org/wiki/Gell-Mann_amnesia_effect
https://qph.fs.quoracdn.net/main-qimg-0f650e809408f3962a1ed0...
How do you argue what they did and are continuing to do is just in this situation?
The problem is now the lack of public trust in their work. They might fix the software, but how to prove they're not lying again?
You may find that OK, if you wish. You may choose to do nothing.
We don’t, and won’t.
Is the MCAS the only place they messed up? Will this fix truly be 100%? Remember that their first attempt at a fix was rejected.
When you see one bug, that’s often an indication that more are nearby.
If, hypothetically, an Airbus had a problem in the same region of flight would it even be detected in flight testing? As far as I'm aware it wouldn't be as direct mode is a reversionary mode intended to get the aircraft safely on the ground.
They cannot be greater than a set level (essentially, an average strength pilot), particularly when performing critical manuevers.
This was actually the whole reason MCAS was engineered in the first place: to lower the effective stick force required to within the acceptable limits in certain scenarios.
So presumably Airbus in direct mode could still have similar issues flagged in direct mode, if the plane behaved in such a way as to require unacceptably high stick force to move control elements (even if it was a 1:1 mapping).
One thing I'm not sure about is whether Airbus would have to demonstrate proper controllability (i.e. adherence to control force regulations) in all phases of flight and corner conditions.
You could have a scenario where by they have a complete control reversal on the approach to stall but under normal law the pilot would be oblivious. This would obviously show up in direct law.
I'd hope they would have to demonstrate both things: (1) that a given mode can or cannot be active in a certain scenario, and (2) how the plane behaves in all tested scenarios under all modes potentially active.
Is there a reason this necessarily wouldn't be the case?
But that's not commerical aviation - that's combat aviation. That's "you fly faster or the missile catches you and you die anyway" aviation.
Building intentionally unstable airframes for civilian aviation is a very different proposition. And unrelated to the use of fly-by-wire.
> Airbus jets carry passengers and have been fly-by-wire for decades
a response to
> instability of high performance jets
?
Nice strawman. We are talking about the MAX not the 737 in general.
Why don't you explain why previous variants of the 737 didn't require MCAS?
The trim equivalent of MCAS would be some elevator trim that ensures the excess AOA potential of the MAX could not occur, if set correctly. That is how a stable aircraft behaves. MCAS is a computer override to compensate for a condition that should not really occur in the first place.
I agree, so where is your comparison of 737 Max and non-Max airframe? Because we have real data, including death toll, that shows one airframe is not like the other.
> Boeing's mistake was in underestimating the burden placed on the pilots in a runaway trim situation, and assuming that pilots could execute a recovery procedure correctly that remained unchanged from prior iterations but that had also been rarely needed on prior iterations (vs. the MAX, where MCAS failures were common enough that an average pilot might actually need to execute the procedure).
This is not the whole truth as we know in this situation MCAS 1.0 was a critical flight system with a non-redundant data source. The "burden" placed on pilots was that the system did not have sufficient and trustworthy information to prevent a faulty and inadequately designed system (MCAS) from crashing the airplane. Furthermore since MCAS is not required, again, on non-Max airframe it seems your assertion that you have background in aerospace engineering is egregious because you should understand all 737 Max are currently grounded because the 737 Max is not a 737 airframe and should be recertified as such.
Balloons, paper jets...
Since both crashes were caused by malfunctioning software, this doesn't tell you anything about the fundamental soundness of the airframe.
> We know the MCAS was a workaround to an aerodynamics problem
MCAS was a workaround to make the plane handle more like a 737. The existing handling was fine by itself (not 'fundamentally flawed'), it just didn't match the 737.
> How do you argue what they did and are continuing to do is just in this situation?
I don't see where I did that. I just don't think there is any evidence that the airframe is actually fundamentally unsafe.
It's pretty clear that the author of the comment I originally responded to was not considering software.
See: https://en.wikipedia.org/wiki/Air_France_Flight_447
https://aviation.stackexchange.com/questions/62338/why-did-a...
And that pilot crashed a perfectly fine airliner after he lost situational awareness and then did the one thing you should never do - pull the steering column back in a mad panic until the plane stalls.