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737 Max: 1960s Design, 1990s Computing Power and Paper Manuals

nytimes.com

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Re: 737 Max: 1960s Design, 1990s Computing Power and Paper Manuals

#61

Post by cm2187 »

JauntyHatAngle wrote: post #56
myth2018 wrote: post #46

Mass media in general is stressing too much the fact that 737 MAX is allegedly based on dated designs. I think it's fair to say that MAX versions present some compromise solutions (like the now-infamous MCAS, which is there to compensate for the "unnatural" bigger engines). But I think that is not the main point. They would be good solutions it they worked as intended. There are some other more fundamental and more d…

>Like, why does such a critical system like MCAS take only a single AoA sensor as input, when there are two sensors available? Specially considering that the inputs from both are hardware-available to MCAS (the new software version is going to take data from both). Are you saying the answer in the article didn't give enough information? "Airbus addressed this potential problem on some of its planes by installing thre…

No it doesn’t answer the question. If there are two sensors already installed, not requiring change, how come the MCAS only uses one, not both?

Re: 737 Max: 1960s Design, 1990s Computing Power and Paper Manuals

#62

Post by crimsonalucard »

CivBase wrote: post #31

Why exactly does this author think an airplane needs a lot of computing power? Airplane software does not deal with especially large amounts of data or intense computations. Faster hardware does not provide an inherent safety benefit. There is a large degree of coupling between avionics hardware and software amd updating that software is prohibitively expensive. There's just no point in doing it unless you get a tang…

I think the author was referring to processors handling UI displays rather than a computer system that has only the processing power to only handle a blinking LED.

For example if a UI display showed:

"Warning: MCAS overriding pitch up. Disable?"

Is better than a LED #234 and LED 412 are on. Consult manual for instructions.

I would imagine that a lot of the fly by wire or control systems nowadays are either analog systems or very very simple digital systems (with extreme redundancy).

Re: 737 Max: 1960s Design, 1990s Computing Power and Paper Manuals

#63

Post by cm2187 »

flyinglizard wrote: post #58
kacamak wrote: post #52

Earlier quoted context omitted.

>Like, why does such a critical system like MCAS take only a single AoA sensor as input The classic approach is to have three sensors, so in case one fails you can know which one. Having two only indicates something is wrong but is not useful on the fly.

Three with a disagree algorithm is definitely what I’d expect out of such a critical system, but two with signal averaging would still be much better than just one.

Or alternatively with two, and disabling MCAS if they disagree, seems a better solution than having one and having no way to tell if it is working (keeping in mind both can still fail simultaneously). Not an ideal solution but better.

Re: 737 Max: 1960s Design, 1990s Computing Power and Paper Manuals

#64

Post by reacweb »

spacedog wrote: post #49

>> “They wanted to A, save money and B, to minimize the certification and flight-test costs" This seems to be the root cause of the problem. Competition is not always good.

I think Boeing was in a wrong mindset: certification was seen as a burden instead of being seen as an help to build a better aircraft. But maybe it was not only the fault of Boeing. The certification process of FAA is perhaps not friendly enough toward big air-frame changes (like putting the wings slightly higher to make room for the bigger reactor). Here, the certification process has not identified that a failure of one AOA sensor was able to cause a difficult to avoid crash. Maybe we should allow the use of less reliable source of data (like GPS, ...) each time a sensor has a problem.

Re: 737 Max: 1960s Design, 1990s Computing Power and Paper Manuals

#65

Post by jamesdgb »

crimsonalucard wrote: post #62
CivBase wrote: post #31

Why exactly does this author think an airplane needs a lot of computing power? Airplane software does not deal with especially large amounts of data or intense computations. Faster hardware does not provide an inherent safety benefit. There is a large degree of coupling between avionics hardware and software amd updating that software is prohibitively expensive. There's just no point in doing it unless you get a tang…

I think the author was referring to processors handling UI displays rather than a computer system that has only the processing power to only handle a blinking LED. For example if a UI display showed: "Warning: MCAS overriding pitch up. Disable?" Is better than a LED #234 and LED 412 are on. Consult manual for instructions. I would imagine that a lot of the fly by wire or control systems nowadays are either analog sys…

I understood the author the same way you did

Re: 737 Max: 1960s Design, 1990s Computing Power and Paper Manuals

#66

Post by VBprogrammer »

cm2187 wrote: post #61
JauntyHatAngle wrote: post #56

Earlier quoted context omitted.

>Like, why does such a critical system like MCAS take only a single AoA sensor as input, when there are two sensors available? Specially considering that the inputs from both are hardware-available to MCAS (the new software version is going to take data from both). Are you saying the answer in the article didn't give enough information? "Airbus addressed this potential problem on some of its planes by installing thre…

No it doesn’t answer the question. If there are two sensors already installed, not requiring change, how come the MCAS only uses one, not both?

Instrumentation on an aircraft is usually designed with a pilot and copilot set. Everything down to the pitot tubes which feed the information is unique to that side of the aircraft. This harks back to the day when it was the only sensible solution when your guages are actually just directly reading airpressure differences.

Clearly these signals can be cross connected, because that's the solution Boeing are testing at the moment, but it's outside the normal design of aircraft systems.

Re: 737 Max: 1960s Design, 1990s Computing Power and Paper Manuals

#67

Post by BuildTheRobots »

pinewurst wrote: post #2

The "1990s Computing Power" comment is ignorantly harsh. The MAX (to the best of my knowledge) uses a similar AMD29050-based architecture as the 777 (where it was pioneered) and the 737-800/900. It's amply fast and very very reliable, hardware and software (setting MCAS aside which is new to MAX). Any sane person would prefer the solid well-proven choice over the bleeding edge. People used to make similar comments ab…

The "1990's Computer Power" comment is factually correct.

According to wikipedia, the AMD29000 processor was first released in 1988 and "In late 1995 AMD dropped development of the 29k..."

I'm not commenting on whether that's appropriate to be running your aircraft or not, but it does very much seem to be a 1990's CPU running approx 50mhz.

Re: 737 Max: 1960s Design, 1990s Computing Power and Paper Manuals

#68

Post by huffmsa »

dmix wrote: post #35
CivBase wrote: post #31

Why exactly does this author think an airplane needs a lot of computing power? Airplane software does not deal with especially large amounts of data or intense computations. Faster hardware does not provide an inherent safety benefit. There is a large degree of coupling between avionics hardware and software amd updating that software is prohibitively expensive. There's just no point in doing it unless you get a tang…

Wait until they finds out what software powers the nuclear weapons of 90%+ of the world, top-tier fighter jets, "critical" infrastructure like power (including nuclear), and countless financial/banking systems. To be fair the article doesn't critique using 1990s (or earlier) hardware/software. It's merely a clickbait headline. The only reference is dismissed by the very next sentence as insignificant [Boeing could be…

The NYT fired basically their entire editorial staff in 2017. The accelerated degradation has been noticable.

Re: 737 Max: 1960s Design, 1990s Computing Power and Paper Manuals

#69

Post by theclaw »

crimsonalucard wrote: post #62
CivBase wrote: post #31

Why exactly does this author think an airplane needs a lot of computing power? Airplane software does not deal with especially large amounts of data or intense computations. Faster hardware does not provide an inherent safety benefit. There is a large degree of coupling between avionics hardware and software amd updating that software is prohibitively expensive. There's just no point in doing it unless you get a tang…

I think the author was referring to processors handling UI displays rather than a computer system that has only the processing power to only handle a blinking LED. For example if a UI display showed: "Warning: MCAS overriding pitch up. Disable?" Is better than a LED #234 and LED 412 are on. Consult manual for instructions. I would imagine that a lot of the fly by wire or control systems nowadays are either analog sys…

It's a moot point anyway - the could not change the UI beyond converting physical dials to virtual ones, because that would have required retraining which they wanted to avoid.

Even if they could have changed the UI they still needed to hide the existence of the MCAS system, again to avoid retraining, so it's doubtful such a clear an helpful error message would be allowable.

Re: 737 Max: 1960s Design, 1990s Computing Power and Paper Manuals

#70

Post by huffmsa »

JauntyHatAngle wrote: post #57
ReptileMan wrote: post #17

Earlier quoted context omitted.

A lecturer of mine once said - knowing what kind of people we teach here for programmers, I am scared of going to the doctor. The less software is in something(and less cloudy/iot) the better. And the more I program the more I prefer stupid and mechanical things when reliability is on the line. A paper manual is always there for you.

>A paper manual is always there for you. Then have the paper manual as a choice and/or backup. If the programmers working on aircraft are so incompetent that they can't get a the digital manual correct, than they have no business programming any of the other multitude of systems that are critical to fly-by-wire systems.

And the time it takes to realize your iPad has run out of battery or you accidentally open an advertisement before grabbing your paper manual is too long.

The manuals have never been an issue. In fact, having a physical, rigorous checklist has been shown to improve the likely hood of a successful outcome.

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