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Boeing 737 MAX crash and the rejection of ridiculous data

philip.greenspun.com

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Re: Boeing 737 MAX crash and the rejection of ridiculous data

#151

Post by salawat »

meshko wrote: post #119

All the talk about how crappy Boeing engineering here was is bullshit and speculation and I am surprised PG participates in it. What we can discuss objectively here is incident response in which Boeing allowed the situation to continue after the first crash. How did they not run hundreds of hours of simulations, code reviews etc, etc on the system assumed to be at fault? How did they not immediately change the safety…

It's not really speculation. The proof, as they say, is in the impact crater.

The only mystery left is, what is the nature of the paper trail that led to this catastrophe?

Was there malicious malfeasance? Overt and irresistible pressure to certify at all costs?

Was it all just a tragic mistake? We don't know. We only know the physical systems that contributed to the crashes, and some of the motivations that would have contributed. The technical implementation can be roughly inferred by any programmer, and it doesn't take a rocket scientist to figure out a ball was dropped somewhere for a plane development program to fall afoul of such a foreseeable failure state.

Re: Boeing 737 MAX crash and the rejection of ridiculous data

#152

Post by salawat »

FartyMcFarter wrote: post #82

Maybe someone can illuminate this. This comment seems to say that Boeing has recently implemented a bunch of fixes to prevent MCAS from activating in various scenarios, which allegedly make MCAS safety a non-issue: https://philip.greenspun.com/blog/2019/04/08/boeing-737-max-... I'm not knowledgeable on planes, but some parts of this make me wonder if these fixes will cause the opposite problem. For example if the two…

You are correct. The rather humorous aspect is that they really can't stick to the "no retraining" claim or really the claim the plane is airworthy because the plane is only certifiably airworthy when MCAS is operating.

So in short, yes. Their fix is introducing problems elsewhere. This characteristic is what has many thinking their was a series of grievous process, business, and regulatory errors layered on top of the known poor engineering decisions that came together to set the stage for these catastrophes.

Re: Boeing 737 MAX crash and the rejection of ridiculous data

#153

Post by cmurf »

pedasmith wrote: post #146
cmurf wrote: post #142

Earlier quoted context omitted.

A commonality in AF 447 and the two MAX cases: angle of attack is not displayed to the pilots. A substantial difference between them, is automation had totally checked out in the 447 case, whereas in the MAX cases automation took action contrary to reality. I let the engineers argue over redundancy. As a pilot I think it's a factor, but far less so than the pilots being denied knowing their airplane. 447 pilots had n…

The real question is: what training would you drop in order that the pilots get this alternate training? You can't just say, "train train train"; eventually the pilots have to actually fly.

Absurd for three reasons:

- You've produced no evidence these pilots are at any training limit, you just made that up, so I call bullshit.

- I'm a pilot and a former flight instructor so I have some credibility in refusing a binary choice like you've proposed. It's not that much training. I had to do difference training for checkouts on a regular basis (giving it and receiving it) and it's not high quantity training, it is high quality training.

- The strongest argument there's plenty of opportunity for training is the fact the MAX had the same type certification as the previous NG model series. So what's the worst case scenario for difference training? It'd require an aircraft type certificate, which will require pilots undergo training and checkout for an additional type rating.

Quite a lot of pilots have multiple type ratings, it's not unusual, in fact the pilot of Ethiopian Airlines 302 had type ratings for B737-7/800, B757/767, B777, and B787. What, was he only training and never flying?

Re: Boeing 737 MAX crash and the rejection of ridiculous data

#154

Post by salawat »

olliej wrote: post #57

I mean of course Arizona does get hot enough to melt street signs: https://www.accuweather.com/en/weather-news/its-so-hot-in-ar... Maybe those were metal ones a 400+ degrees does happen? I mean survivor bias means we won't have met anyone from Arizona who went out in that heat :D

Completely off topic, but I hate Accuweather. The guy that runs it has lobbied left and right to keep the NWS and NOAA from being able to just deliver weather products because they'd cut into his revenue stream he's developed by charging people for access to public data.

Anyway... End rant.

Re: Boeing 737 MAX crash and the rejection of ridiculous data

#155

Post by salawat »

fixermark wrote: post #87
geggam wrote: post #78

Earlier quoted context omitted.

Have you had to fight your lane assist yet ? I am all for the sensors to give me information but when the systems take over control I am not a fan. Cyclists in the EU have learned that the car sensors will slam on the brakes. Quite irritating when the car slams on the brakes and they are laughing at you.

Ah, see, I'm American. ;) The lane assist can be disabled and a cyclist who hard-brakes in front of me is taking their life in their hands because my Ford only stops if I touch the brake (it just stops as hard as it needs to to minimize risk of impact, regardless of how soft I push the pedal). (Sidebar: I almost feel like that cyclist game is something that should be solved with more sensors. If it's a common issue,…

No. No. No.

So we need more software to solve problems created by software being exploited by people.

I have a much simpler solution that doesn't involve taking away from someone's agency.

A)look both ways before crossing

B) Don't drive the piece of equipment distracted.

The more sensors we put on cars, the more we lay the foundations for technologies that can handle will be used in tyrannical ways. No thanks.

Re: Boeing 737 MAX crash and the rejection of ridiculous data

#156

Post by salawat »

penagwin wrote: post #128
geggam wrote: post #126

Earlier quoted context omitted.

Yes, the rear. I didnt make that clear. When backing out the bikes can be 50 ft away coming fast and the car senses they will be close so it slams on the brakes way before anyone is in danger. Coffee spills etc

Whoops my bad! I thought you meant they were purposely traveling in front of the car, knowing it's sensors would force it to stop. It'd be super moronic and dangerous, but if you recognized the car model it would at least be possible.

That's what I thought too.

Re: Boeing 737 MAX crash and the rejection of ridiculous data

#157

Post by [deleted] »

pedasmith wrote: post #146
cmurf wrote: post #142

Earlier quoted context omitted.

A commonality in AF 447 and the two MAX cases: angle of attack is not displayed to the pilots. A substantial difference between them, is automation had totally checked out in the 447 case, whereas in the MAX cases automation took action contrary to reality. I let the engineers argue over redundancy. As a pilot I think it's a factor, but far less so than the pilots being denied knowing their airplane. 447 pilots had n…

The real question is: what training would you drop in order that the pilots get this alternate training? You can't just say, "train train train"; eventually the pilots have to actually fly.

[deleted]

Re: Boeing 737 MAX crash and the rejection of ridiculous data

#158

Post by brandonjm »

cmurf wrote: post #153
pedasmith wrote: post #146

Earlier quoted context omitted.

The real question is: what training would you drop in order that the pilots get this alternate training? You can't just say, "train train train"; eventually the pilots have to actually fly.

Absurd for three reasons: - You've produced no evidence these pilots are at any training limit, you just made that up, so I call bullshit. - I'm a pilot and a former flight instructor so I have some credibility in refusing a binary choice like you've proposed. It's not that much training. I had to do difference training for checkouts on a regular basis (giving it and receiving it) and it's not high quantity training,…

A fourth reason:

Wouldn't a pilot rather spend some time to train for a new potential issue than not know what to do when that issue came up?

Re: Boeing 737 MAX crash and the rejection of ridiculous data

#159

Post by teyc »

ChuckMcM wrote: post #90
Ataraxic wrote: post #21

It should be noted in the doomed Air France 447 flight, the plane activated the stall warning because of a high angle of attack that was leading to stall. (thanks pdx for the corrected info) At some point the system rejected the data and stopped the stall warning because the angle of attack was so severe that it considered the data erroneous. This is speculated to have caused the co-pilot to keep pulling back on the…

Your basic point is spot on, it isn't simple. The challenge I think is to keep two things separated, one is the flight control laws that the system is implementing to keep the plane in the air (to the best of its ability), and the other is the situational awareness indicators for the pilots so that they can tell what what the plane is "thinking" about how it is flying (or not). The closest analogy I can come up with…

It wasn't due to the cost. It is the whole business of avoid pilot retraining - which is apparently "must-have" for airlines. At some point, Boeing prioritised papering over the fundamental difference in the flight characteristics of MAX _above_ the pilots' needs to be informed of what is actually happening with the plane.

Re: Boeing 737 MAX crash and the rejection of ridiculous data

#160

Post by joezydeco »

noxryan wrote: post #18
yongjik wrote: post #8

With all due respect, this sounds too much like the kind of armchair quarterbacking that routinely appears on HN when avionics/politics/astronomy is mentioned, where a lone programmer feels competent enough to criticize an industry for missing "something obvious". I mean, this particular change might have saved the particular 737, but I'd rather hear it from someone who actually knows how 737s fly.

I agree that we frequently see this on HN in regards to aviation. However, I don;t think it applies to Greenspun. He's a knowledgeable and active pilot himself.

However, any programmer that's been around the block a few times knows when they see a phrase like

"all of the problems on the Ethiopian flight could potentially have been avoided by changing....about 10 characters of code"

It's a sign that things are never as simple as they seem on the surface.

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