Boeing Built Deadly Assumptions into 737 Max, Blind to a Late Design Change • Hacker News Board

Re: Boeing Built Deadly Assumptions into 737 Max, Blind to a Late Design Change

#271

Post by salawat » Mon, Jun 03, 2019, 2:35 PM UTC

cmurf wrote: post #260

TheOtherHobbes wrote: post #186

Earlier quoted context omitted.

It's not stable in a "crashes into the ground and kills everyone on board in spite of the best efforts of its pilots" manner. In exactly what manner is it not obvious this is not an acceptable design outcome?

You are confusing stability, which is a specific aerodynamic term, with two examples of catastrophic outcomes. Reread the original post I replied to, none of the first three sentences are true: unstable flight characteristics, instability is a hardware problem, software routine only exists to paper over the hardware problem. The problem results from an edge case or it would be happening a lot more often. That it's an…

I'm one of the chief repeaters who has Harper on the stability issue and the control stick force curve; I usually Eve up dropping a post or two about it in each MAX thread.

You are right on target, but I do wish to point out the aerodynamics are still a problem, and a problem that has caused a great deal of grief in aviation history.

Take a trip down memory lane, and give the D.P. Davies Interview from the Royal Aeronautics Society a listen. Specifically, the one revolving around the 727 certification.

There seems to be two schools of thought to aircraft design. One is the test pilot's wet dream: simple layout, well behaved, neutral stability, or minimal bad behavior up to the corners of the flight envelope, then easily discernable, and recoverable stall behavior.

The other school is the realm of the Engineer. The Tricky Sick school if you will. Apply enough computer and piloting aid to the properly shaped brick, and it can be flown like a 737! Or Airbuses version of "let the plane fly itself, just tell it where to go."

Even as far back as the certification of the 727, test pilot's saw the shift away from the meutrally stable machine that "just flew" to an ever increasing complex mishmash of complex systems working in the background to male unstable airframes fly like naturally (neutrally) stable ones. Which is all fine and good until something goes wrong, and those systems fail, leaving a pilot in uncharted waters.

The control stick force stuff is not a distraction, just another link in the chain of normalization of deviance that resulted in a departure from "building an airworthy frame" to figuring out how to mask the "unairworthyness" of a frame sufficiently so as to get it by the regulators.

That's not to say it can't be done, but one approach is definitely inherently riskier than the other, and requires increased levels of communication among everybody involved.

Point being: this has been built up to since as far back as the 60's. See the 727 certification in above mentioned interview, the many difficulties that the MD-11 ran into with it's LSAS, and note the similar less than stellar results that emerged from trying to optimize for fuel efficiency at the cost of having to implement increasingly complex control system hacks to maintain parity with regulations/previous airframes.

Interview:

https://www.aerosociety.com/news/audio-the-d-p-davies-interv...

Re: Boeing Built Deadly Assumptions into 737 Max, Blind to a Late Design Change

#272

Post by bumby » Mon, Jun 03, 2019, 2:49 PM UTC

HyperTalk2 wrote: post #269

bumby wrote: post #79

Earlier quoted context omitted.

There are standards for how many independent inputs are needed based on the criticality of the system. It's not just a guess as to how many are sufficient. That's why the categorization of MCAS correctly ('catastrophic' vs. 'hazardous' is important)

No. If you have a hundred AoA sensors, then you know to trust that whatever 90% of them are reporting is the truth. You also know exactly which of the remaining 10% need to be repaired or replaced upon landing.

I'm not sure what you're saying a hard "no" to; that's a strange response to my point. Your response is a little naive in terms of the way sensors work. You won't necessarily know which are reporting "truth" because in reality there will be a range of values reported because each sensor has a bound of uncertainty. It comes down to understanding what level of uncertainty and reliability are necessary for the application.

In designing airframes, there's actually guidance along these lines to remove the ambiguity of how many sensors are necessary. You can use calculations to define what level of reliability is sufficient. As an example to this point, there are standards like IEC 61508 that outline the procedure for doing such calculations. Many organizations also create their own standards (e.g., five redundant sensors for mission critical systems, self-diagnostic sensors for safety critical systems etc.) It shouldn't be guesswork. It's a risk-based decision, not a subjective guess as to whether two or "a hundred" sensors are necessary.

Re: Boeing Built Deadly Assumptions into 737 Max, Blind to a Late Design Change

#273

Post by salawat » Mon, Jun 03, 2019, 2:52 PM UTC

BurningFrog wrote: post #135

ficklepickle wrote: post #52

This whole plane sounds like any ugly hack. They slapped very different engines on an existing airframe. Then, when it inevitability exhibited undesirable behaviour, they tried to paper over the cracks. Then they hid this information from their customers, regulatory agencies and the pilots. It makes me wonder if there are other issues with the Max that the public doesn't know about yet. I hope a thorough review of Bo…

It's an ugly hack because the design tries to stay within what The Regulator considers the same airplane type. This in turn is because getting a new airplane type to market would cost some (I assume, facts are welcome!) unholy amount of money and time to get approved. If you consider that decision "greed" or "a rational response to perverse regulatory incentives" is I suppose a personality test as good as any :)

Those regulatory incentives are there for a reason. They are written in blood for the most part.

It's one thing to scoff and believe "Oh, it's nothing! You're just holding us all back!"...

...Right up until a plane load of freight or people plunges out of the sky.

Free market economics optimizes for one thing, and one thing only as a first,order optimization. That's why we regulate. To ensure that all those nuisance secondary facets are accounted by everyone equally to ensure that market forces natural race to the bottom doesn't compromise the central tenet of air safety; that everyone and everything that goes up, comes back down, safely, controlled, and alive.

The business part, if you think about it, is secondary to the capability to make and safely deploy a new plane. A nice bonus.

Sacrificing the quality of the final product for the sake of looking better on the balance sheets us a cardinal sin. Plain and simple. Based on testimony from inside, that sin seems to be SOP at Boeing for the better part of the last decade.

Re: Boeing Built Deadly Assumptions into 737 Max, Blind to a Late Design Change

#274

Post by salawat » Mon, Jun 03, 2019, 3:56 PM UTC

KaoruAoiShiho wrote: post #105

How would you design your bureaucracy so that this kind of thing can't happen? I see this type of failure all the time in organizations big and small. Sometimes things are just too complex to have an auteur that can understand the entire system and when every department strives to optimize for its specific goal shit can really hit the fan.

Don't disincentivize defect reporting?

Don't restrict your definition of "actionable" to only pertain to fixes that don't come with a monetary cost?

Don't get rid of your Quality people. Definitely don't get rid of them for raising too many defects.

Don't stop focusing on "the box" (I.e. the plane) because customers already assume it will be "high quality", and reengineer a physical engineering/design firm into some ungodly act of "financial innovation".

Don't treat regulations as something to be worked around.

Don't skimp on Acceptance Testing of outsourced software deliverables.

Make sure your CEO and Sales staff understand there are things you can not (and should not) sell.

Listen to your Unions. Don't try to work around them.

These aren't hard. They are all also things that by not doing them, Boeing set the stage for this cascaded failure of epic proportions.

Pity that American manufacturing and Engineering firms never (in my experience) took Edward W. Demmings seriously. His 14 points are a hell of a good start.

Re: Boeing Built Deadly Assumptions into 737 Max, Blind to a Late Design Change

#275

Post by londons_explore » Mon, Jun 03, 2019, 4:06 PM UTC

bowmessage wrote: post #159

tomglynch wrote: post #148

I posted this as a comment the other day in another Boeing and MCAS discussion. In my research into the topic the saddest bit of information I've seen is the image of the black box data for the flight (the first crash): https://i.imgur.com/WJuhjlO.png You can see from the graph that in the final minutes and seconds, the pilot put insane amounts of force on the control column (aka the yoke) to try to pull the plane ou…

Interesting that there are two angle of attack sensor readings in the black box image when the major issue with MCAS seems to be that it was relying on only a single sensor?

Apart from at the start (when the plane is on the ground), both sensors seem to report the same data?

So why did it crash?

Re: Boeing Built Deadly Assumptions into 737 Max, Blind to a Late Design Change

#276

Post by magduf » Mon, Jun 03, 2019, 4:20 PM UTC

_ph_ wrote: post #177

tacosx wrote: post #87

Earlier quoted context omitted.

It's not impossible to make it work, and in the future I'd expect more and more automated systems in planes for sure. But you have to recognize the whole engine hack is just a convoluted workaround to avoid as much pilot training as possible. The entire goal of the project seems to be to avoid ever training pilots for as long as possible. It's a brand new plane, the newest plane on the market, and the first thing you…

The problem with training pilots for a new machine isn't the training itself but rather, that a pilot is rated for one machine type only. If the MAX had a different type rating, MAX pilots would no longer be rated for the non-MAX 737. There are some larger US carriers which are 737 only, partly so that all pilots are trained for all of the machines. Having to split the fleet into two types would have a huge impact on…

>The problem with training pilots for a new machine isn't the training itself but rather, that a pilot is rated for one machine type only.

Citation needed. I've never heard this before, except for some other person on a message board, and I've been involved with aviation and known pilots with multiple type ratings.

Re: Boeing Built Deadly Assumptions into 737 Max, Blind to a Late Design Change

#277

Post by baud147258 » Tue, Jun 04, 2019, 4:14 PM UTC

Crosseye_Jack wrote: post #219

blinky1456 wrote: post #211

Earlier quoted context omitted.

I disagree, It is a free image hosting platform for sharing images. There is nothing wrong with linking to it. If you upload or want to share what is on the platform, they would prefer if you link it that way, as is their right. It is a business after all. And If people want to hotlink directly to an image they should pay up and host it themselves.

I don’t disagree that if people want to be able to hot-link images they should pay for the hosting themselves (It’s something I do myself - instead of replying on imgur I just pay to host the files on S3). I just find it amusing that imgur was born out of being a better image host then the competition as linking to images on reddit at the time sucked, and now (IMO) has turned to “the dark side” and are doing the thin…

> they have become what they hated

I think that's the fate of all image hosts: current offerings have a lot of (crappy) ads to pay for hosting => competitors arrives, starts with less ads to incite onboarding => competitors gets a market share => competitors now has to turn a profit => add more ads (or ask money for hosting)

Re: Boeing Built Deadly Assumptions into 737 Max, Blind to a Late Design Change

#278

Post by Crosseye_Jack » Thu, Jun 06, 2019, 4:36 AM UTC

baud147258 wrote: post #277

Crosseye_Jack wrote: post #219

Earlier quoted context omitted.

I don’t disagree that if people want to be able to hot-link images they should pay for the hosting themselves (It’s something I do myself - instead of replying on imgur I just pay to host the files on S3). I just find it amusing that imgur was born out of being a better image host then the competition as linking to images on reddit at the time sucked, and now (IMO) has turned to “the dark side” and are doing the thin…

> they have become what they hated I think that's the fate of all image hosts: current offerings have a lot of (crappy) ads to pay for hosting => competitors arrives, starts with less ads to incite onboarding => competitors gets a market share => competitors now has to turn a profit => add more ads (or ask money for hosting)

Thing is imgur was profitable (before reddit became its own image host, dunno what their status is these days, I just know there submission numbers dropped sharply after reddit did that, but maybe their own community was able to recover from that).

Back in the day you used to be able to pay to upgrade your imgur account to allow larger file uploads (which was great for gifs), disable the ads you saw site wide and disable the ads people saw coming to your submissions. I guess the Rev they were generating off ads back in 2015 was out stripping the Rev generated from Pro accounts (esp with the ability to prevent ads on your submissions. If you were a imgur pro user you were either trying to support that platform or was a power user and getting a fair few visits to your submissions) because that’s when they they dropped them and they were reporting as profitable back then. Which is odd (to me) because it’s been since then that the service (IMO) has gotten worse. To me they had a winning formula and the user base to make it work but fucked it up (or not, they are still around today. So maybe they did the right thing, I’m just an old grumpy user who doesn’t like change. Now get off my lawn, I have clouds to shout at...)

Re: Boeing Built Deadly Assumptions into 737 Max, Blind to a Late Design Change

#279

Post by CamperBob2 » Sat, Jun 08, 2019, 8:09 PM UTC

jussij wrote: post #134

CamperBob2 wrote: post #48

Earlier quoted context omitted.

Anything short of admitting "we fundamentally screwed up, and are rethinking the poor decision to pair this engine with this airframe" Can you cite the basis for this often-expressed sentiment? There's absolutely no reason why a properly-designed and -vetted MCAS system wouldn't have been a perfectly acceptable solution to any handling irregularities caused by the engine configuration. The idea was fine. The fault wa…

> There's absolutely no reason why a properly-designed and -vetted MCAS system wouldn't have been a perfectly acceptable solution Surely that was exactly the MCAS that was installed in both of the planes that crashed. But the fact it failed so badly suggest it might in fact be a rather difficult system to get right.

If you're arguing that MCAS was "properly designed and vetted," you're the only voice crying in that particular wilderness.

Boeing's implementation will be a mainstay in engineering ethics classes for the next 100 years, right next to the Therac-25 and the Kansas City Hyatt.

Re: Boeing Built Deadly Assumptions into 737 Max, Blind to a Late Design Change

#280

Post by quink » Tue, Jun 11, 2019, 12:09 PM UTC

CydeWeys wrote: post #227

quink wrote: post #161

Earlier quoted context omitted.

Say what now? It sounds like you want the FAA to revoke the A320 type certificate?

Yes. The A320neo should be the last new design allowed under the same certification. They'll be forced to re-certify whatever they do next anyway, so they won't have to try to shoehorn things into the older design like Boeing did with the 737.

But Airbus shoehorned the same thing - a CFM LEAP - into an older design, just like Boeing did.

It's not the case that they won't have to try, they already did it years ago.