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Latest 737 Max Fault That Alarmed Test Pilots Rooted in Software

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Re: Latest 737 Max Fault That Alarmed Test Pilots Rooted in Software

#81

Post by robin_reala »

tyingq wrote: post #65
Maakuth wrote: post #41

Earlier quoted context omitted.

Here's an article about it. According to this piece, 737 avionics run on a pair of 80286s. https://www.moonofalabama.org/2019/06/boeings-software-fix-f...

If true it uses a 286, for some relative comparison, the fastest 286 is 1.5 MIPS. A run of the mill current Arduino is probably 20 MIPS, and a Raspberry PI3 is 2451 MIPS.

Can’t find the exact MIPS estimate for the Harris CS80C286 25Mhz 286, but given that the 1.5MIPS was quoted for the 10Mhz Intel one I’d guess it’s substantially faster.

Although still slower than an Arduino :)

Re: Latest 737 Max Fault That Alarmed Test Pilots Rooted in Software

#82

Post by WJW »

jacobush wrote: post #55
alexis_fr wrote: post #25

Earlier quoted context omitted.

I wonder if the human life calculation worked well this time. As far as I see, Boeing lost more than the sum of the human lives; they also lost reputation for everything new they’ve designed in the last 7 years being corrupted, and they also engulfed the reputation of FAA with them, whose agents would fit the definition of “corrupted” by any people’s definition (I know, they are not, they just used agents of Boeing t…

There is so much of U.K. which is incredible and depressing at the same time. Completely pummelled by war, (receiving no aid like West Germany did) they managed to, in 1949, release a Space Age passenger commercial airliner, defining the genre. It looks modern even today. Yet, fumbled the ball. They also had a space program, closed it down after their first satellite, which was a success. Concorde! (With France.) It…

The United Kingdom received over twice the amount that West Germany did under the Marshall plan. https://en.wikipedia.org/wiki/Marshall_Plan#Expenditures

Re: Latest 737 Max Fault That Alarmed Test Pilots Rooted in Software

#83

Post by cstross »

mattlondon wrote: post #70
the-dude wrote: post #66

Earlier quoted context omitted.

The U.K. had an educational computer initiative with the BBC and Acorn. Worked wonders. Then they discontinued the effort.

Yes, although ARM came out of that and now look at that (...or your smartphone) so its not all a disaster. The Raspberry Pi is a spiritual successor which I am generally pleased to see. The RPi was I think partly responsible for a real Computer Science curriculum getting back into schools ... I hate to say it but I think it was Michael Gove that made this happen!

Arm Holdings is now owned by Japan's Softbank, because a Conservative (business-first) administration thought selling off the family silver was a fine idea.

This is pretty typical of the UK government's approach to the computer hardware/software industry. Had the first business computer industry in Europe (anyone else remember the LEO line of mainframes?) and a promising software biz, of which only bits remain. (The gaming industry is thriving, but the rest mostly ended up being absorbed by US multinationals. I could speculate that having a common language, in combination with a series of governments who believed in leaving things to the Invisible Hand, and a business culture dominated by accountants, were at the root of the problem ...)

Re: Latest 737 Max Fault That Alarmed Test Pilots Rooted in Software

#84

Post by antihero »

aurelwu wrote: post #46
thelittleone wrote: post #39

Earlier quoted context omitted.

Wasn’t aware the compute power was low on the 737. Interested if you have some more info? Always thought they would spec a substantially more processing capability than required. I understand economics are a factor but surely it’s not through necessity to save power?

The issue is (from what I understand as layman) that to avoid recertification they kept their old computer hardware from earlier 737 generations, and added more and more tasks to do for it. https://www.nytimes.com/2019/06/26/business/boeing-737-max-f... (somewhere in the middle: "The issue discovered last week is linked to the data-processing speed of a specific flight control computer chip, according to the two peop…

> to avoid recertification they kept their old computer hardware from earlier 737 generations,

This is unbelievably fucked

Re: Latest 737 Max Fault That Alarmed Test Pilots Rooted in Software

#85

Post by jacobush »

bboreham wrote: post #80
jacobush wrote: post #55

Earlier quoted context omitted.

There is so much of U.K. which is incredible and depressing at the same time. Completely pummelled by war, (receiving no aid like West Germany did) they managed to, in 1949, release a Space Age passenger commercial airliner, defining the genre. It looks modern even today. Yet, fumbled the ball. They also had a space program, closed it down after their first satellite, which was a success. Concorde! (With France.) It…

“The largest recipient of Marshall Plan money was the United Kingdom (receiving about 26% of the total), followed by France (18%) and West Germany (11%).” https://en.wikipedia.org/wiki/Marshall_Plan

Today I learned!

Re: Latest 737 Max Fault That Alarmed Test Pilots Rooted in Software

#86

Post by ethbro »

robin_reala wrote: post #81
tyingq wrote: post #65

Earlier quoted context omitted.

If true it uses a 286, for some relative comparison, the fastest 286 is 1.5 MIPS. A run of the mill current Arduino is probably 20 MIPS, and a Raspberry PI3 is 2451 MIPS.

Can’t find the exact MIPS estimate for the Harris CS80C286 25Mhz 286, but given that the 1.5MIPS was quoted for the 10Mhz Intel one I’d guess it’s substantially faster. Although still slower than an Arduino :)

I love how HN is taking umbrage in the rest of the comments about Boeing being too aggressive with MCAS et al. redesign.

Then taking umbrage here that they were too conservative and possibly froze the hardware spec.

Re: Latest 737 Max Fault That Alarmed Test Pilots Rooted in Software

#87

Post by raverbashing »

tus88 wrote: post #28
burfog wrote: post #18

Earlier quoted context omitted.

It's proper. This is exactly how you do things with life-critical embedded software. You detect when things are crazy, which of course shouldn't happen but nevertheless does, and you react in a way that is hopefully not disastrous. The alternative is to ignore the problem. Sensors go bad. Actuators go bad. Voting hardware goes bad. Message routing goes bad. Even the RAM sometimes goes bad. When the hardware is failin…

The way I read it they are not detecting malfunctioning sensors, but essentially a computer fault caused by it's inability to deal with erroneous input. Rather than fixing the computer, they are essentially wrapping a great big try/catch around it....good God.

> are not detecting malfunctioning sensors

Because most of the time you can't. There is no reliable way of knowing when the sensor is lying to you.

You might try to reduce the probability of it happening and try to make it warn you (for example, redundancy, etc), but in aviation, even things that have a probability of failure of 10e-6 or even lower must be considered. 0% chance of reading an erroneous value doesn't exist.

The computer can deal with suspected erroneous input: it can ignore it. There. That's the standard way.

Re: Latest 737 Max Fault That Alarmed Test Pilots Rooted in Software

#88

Post by tyingq »

ethbro wrote: post #86
robin_reala wrote: post #81

Earlier quoted context omitted.

Can’t find the exact MIPS estimate for the Harris CS80C286 25Mhz 286, but given that the 1.5MIPS was quoted for the 10Mhz Intel one I’d guess it’s substantially faster. Although still slower than an Arduino :)

I love how HN is taking umbrage in the rest of the comments about Boeing being too aggressive with MCAS et al. redesign. Then taking umbrage here that they were too conservative and possibly froze the hardware spec.

No umbrage here. Just interesting to me. My Commodore 64 was half a MIP.

Re: Latest 737 Max Fault That Alarmed Test Pilots Rooted in Software

#89

Post by ethbro »

selestify wrote: post #48
comex wrote: post #47

Earlier quoted context omitted.

That interpretation seems like a stretch to me.

The way it's worded, that's exactly the interpretation that a lot of us in this thread get. If this is not actually the case, they should really word it differently.

This is the same Bloomberg that reported on the SuperMicro hardware "compromise."

Re: Latest 737 Max Fault That Alarmed Test Pilots Rooted in Software

#90

Post by ethbro »

Aloha wrote: post #37
nraynaud wrote: post #29

Earlier quoted context omitted.

It would be a not very good airplane. It has only 2 selling points: its type certificate, and its 737 footprint at the terminal. Any new airplane would be a bit higher, it brings some downsides (ground operations people really like the easy access), but having bigger engines under the wings is such an advantage that it overrides all other considerations.

Thats kinda my point, the shared type certificate is most of the justification for the airplane to exist, Boeing would rather build a whole new small aircraft, people who fly on them would rather fly on a whole new aircraft - airlines however strongly prefer something that costs as little as possible to put into service - and has commonality with existing fleets, which means not a whole new aircraft. I bet if you off…

And by "airlines", let's be specific: American Airlines was the carrier that specifically asked Boeing to build an 737 with new engines.
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