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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

#81

Post by arethuza »

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…

I remember working in the early 90s on a training simulation of the reactor safety shutdown equipment for a UK AGR reactor - this device was pretty critical as it as responsible for sequencing the shutdown operations during a scram.

It was designed in the 1960s using technology they were completely confident would work and keep working - so it was basically 1940s electro-mechanical technology: relays, worm gears etc.

I don't think they really trusted electronics at that point, let alone computing devices for something so super critical.

No idea how that is done now though!

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

#82

Post by michaelt »

kacamak wrote: post #52
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 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.

Of course, even with triple-redundant systems failures can still occur.

Air France 447 [1] three independent air data systems, two of them failed due to environmental conditions

XL Airways 888T [2] three independent AOA sensors, two failed because the plane was washed without the right covers in place

US Airways 1549 [3] two independent engines, both disabled by bird strike at the same time (No fatalities)

Qantas Flight 72 [4] three independent inertial reference units, bug in voting system if a single sensor's output had multiple spikes 1.2 seconds apart (no fatalities)

An in the data centre, no amount of power-supply redundancy will save you if a technician pulls out the power cables on the wrong server :)

[1] https://en.wikipedia.org/wiki/Air_France_Flight_447#cite_ref... [2] https://en.wikipedia.org/wiki/XL_Airways_Germany_Flight_888T [3] https://en.wikipedia.org/wiki/US_Airways_Flight_1549 [4] https://en.wikipedia.org/wiki/Qantas_Flight_72

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

#83

Post by andy_ppp »

StreamBright wrote: post #79
andy_ppp wrote: post #77

Does anyone else here feel aeroplane software should be mandated as being open source? Boeing would have never even dreamed of releasing the 737-Max software in the state it was in and the more eyes you have on things like this the better.

Do you think there are a massive amount of developers out there who are at the same time avionics experts? I just don't see how being opensource would help. You wouldn't be able to even test these software projects because it requires and emulator or actual hardware to run on that you do not have. What would it chage if it was opensource?

I think the argument you're making is completely false.

First Premise is that there re not many avionics expers - I agree so having more of those experts able to look at review and learn from different implementations would be a good thing.

Second premise is that you need to be an avionics expert to review and improve avionics software, I'm not convinced, there are many clever people out there.

Third premise you can't test or run the software becuase there is no emulator; maybe if the software was open source someone would start writing an emulator - maybe an emulator could be open sourced?

Fourth point; nothing would change if it was open source - I think the quality of code that would be released would go up and that's the main thing I'm talking about, embarrassment would be the optimal solution to something like this - I'd be very suprised if Boeing would release software that used a single sensor as input to a critical system like this.

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

#84

Post by gargravarr »

cm2187 wrote: post #80
JauntyHatAngle wrote: post #72

Earlier quoted context omitted.

The article also states that 2 sensors is not enough as then you have two sensors that can disagree with no way to figure out the correct one.

Yes but at least you know the reading is faulty and avoid applying dangerous commands. Now I don't know if the stall it is meant to avoid is a greater risk than MCAS pushing the plane in the wrong direction.

Stalls can be extremely difficult to recover from as it means the wings have lost lift, and therefore the control surfaces (which you need to regain stability) have reduced or even complete loss of effect - a so-called 'deep stall'. As bad as MCAS is, it could theoretically (in practise, couldn't) be switched off in this scenario and the plane would be flyable. In the imagined scenario where the plane pitched up and began to stall, Beoing's logic is that without MCAS, the plane would be essentially doomed. Air France 447 crashed due to a (pilot-induced) deep stall; it was otherwise stable at cruising altitude.

The root cause is without doubt relying on a single sensor, and then downplaying the importance of the system so that nobody opted for the additional expense of the extra sensor. Boeing also have to answer for their lack of transparency; their flight control logic has always left the pilot fully in control of the plane, and can override any automatic system. This sets them apart from Airbus, which under almost all circumstances will defer to the computer.

In ways, the 737 MAX crashes are the antithesis of the 447 crash - the pilots thought they were in full command of the plane, whereas an automatic system designed to protect them malfunctioned, versus the pilots in the Air France plane believed the computer would protect them from exceeding the plane's capabilities, whereas the plane's computers could not get reliable data and passed full control to the pilots.

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

#85

Post by stallmanite »

jonas21 wrote: post #10
kbos87 wrote: post #4

The thing that baffles me - why the hell has there never been any innovation in the form of making it easier to diagnose a problem and move through the necessary steps in a checklist beyond fumbling through a paper manual? In a situation where seconds count, it seems illogical that this has never been improved upon. Didn’t at least one of these planes crash because the pilots are believed to have only gotten X number…

As mentioned in the article, other Boeing jets do automatically present a checklist on the display when they detect a problem: > A second electronic system found on other Boeing jets also alerts pilots to unusual or hazardous situations during flight and lays out recommended steps to resolve them. The 737 is stuck in the past because given the choice, nobody wants to have to retrain their pilots on more modern system…

Why is anyone being given the choice?

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

#86

Post by bluedino »

jschwartzi wrote: post #54
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…

Yes, the 486 or 586 are far more powerful processors than what you would actually need for everything but the cockpit UI. You could probably get away with a Z80 or something similar. The flight control computers in our space probes frequently have a similar level of functionality simply because it's more than enough. The only thing a more modern processor buys you is more memory, a faster tick rate for your RTOS, pot…

The goddamn space shuttle ran on 386's, and that was an upgrade from 8086's

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

#87

Post by bdavis__ »

bluedino wrote: post #86
jschwartzi wrote: post #54

Earlier quoted context omitted.

Yes, the 486 or 586 are far more powerful processors than what you would actually need for everything but the cockpit UI. You could probably get away with a Z80 or something similar. The flight control computers in our space probes frequently have a similar level of functionality simply because it's more than enough. The only thing a more modern processor buys you is more memory, a faster tick rate for your RTOS, pot…

The goddamn space shuttle ran on 386's, and that was an upgrade from 8086's

i think the space shuttle used a couple of AP101's, which were 16 bit machines, with core memory, programmed in JOVIAL...

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

#88

Post by myth2018 »

VBprogrammer wrote: post #66
cm2187 wrote: post #61

Earlier quoted context omitted.

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 a…

Uhm.. I don't know.. I'm aware this is the case of airspeed indicators and many others, but, for instance, the autopilot is fed with readings of Pitot tubes from both sides and it disengages when the sensors disagree beyond sensible thresholds. Besides, such issue is brought clearly to the knowledge of pilots.

In the MCAS case, however, we are speaking about a computer which not only interferes in the flight controls, but also does that in a way impossible to override and it's too difficult for the pilots to spot the root cause.

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

#89

Post by myth2018 »

kacamak wrote: post #52
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 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.

Boeing has been using only two for quite a time. Having a failed and a working one would simply indicate that something is wrong, but this information is valuable anyway -- it could be used to prevent MCAS from engaging based on wrong data, exactly one of the features the new software update is bringing.

Besides, those AoA sensors are EXTREMELY reliable. So reliable that some have raised the hypothesis that the real problem is not in the sensors themselves, but in some piece of hardware or software between them and the flight computers.

It seems plausible to me since failures in those sensors are too rare in the other planes but, despite that, they allegedly failed in two 737 Max 8s and in a really short timespan.

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

#90

Post by jaclaz »

cryptonector wrote: post #40
da_chicken wrote: post #9

Earlier quoted context omitted.

Yeah, the B-52, adopted in 1952, is planned to be is service through the 2050s. An airframe design expected to last for over 100 years. Keep in mind that flight itself is barely 100 years old. And paper manuals? Are they expecting to use iPads for in flight documents or something? Shall we compare failure states of paper vs tablets?

Actually, yes, lots of pilots prefer ipads. They are lighter, for one, and for many tasks faster than paging through paper.

>They are lighter, for one, and for many tasks faster than paging through paper.

And are them in your opinion also as reliable as paper manuals?

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