Ethiopian Airlines 737 MAX Investigation Preliminary Report • Hacker News Board

Re: Ethiopian Airlines 737 MAX Investigation Preliminary Report

#231

Post by cjbprime » Thu, Apr 04, 2019, 10:05 PM UTC

geofft wrote: post #223

aaron695 wrote: post #200

Earlier quoted context omitted.

> knowing some greedy bunch of assholes were effectively that malevolent entity, whose will was expressed via the aircraft. If this it true then link? When was this confirmed? Who are the assholes? Else this is just Reddit spam that contributes less than nothing.

The "greedy bunch of assholes" are the Boeing execs who optimized for profit over the lives of those pilots and their passengers. (I thought that was pretty clear from the comment, fwiw.) I think it's been pretty thoroughly established at this point that an underlying design constraint in the MCAS was that it was easier for Boeing to get a 737-with-modifications approved than a new airplane, despite the engines being…

Agree on the consensus.

There's a piece of additional flavor, which is that as I understand it Boeing proposed building a new type of plane as an a320neo competitor, and the airlines announced that they'd only buy it if it's a 737 subtype to avoid having to retrain their pilots. It's not just "Boeing doesn't want to pay for certifications", but also -- and perhaps primarily -- "Airlines don't want to pay for training".

So while Boeing's ultimately responsible for building unsafe aircraft, I could imagine people being angrier at the airlines than Boeing.

Re: Ethiopian Airlines 737 MAX Investigation Preliminary Report

#232

Post by zaroth » Thu, Apr 04, 2019, 10:05 PM UTC

hacker_9 wrote: post #224

aaron695 wrote: post #200

Earlier quoted context omitted.

> knowing some greedy bunch of assholes were effectively that malevolent entity, whose will was expressed via the aircraft. If this it true then link? When was this confirmed? Who are the assholes? Else this is just Reddit spam that contributes less than nothing.

You are disgusting

Please don’t pile on.

Re: Ethiopian Airlines 737 MAX Investigation Preliminary Report

#233

Post by crysin » Thu, Apr 04, 2019, 10:06 PM UTC

na85 wrote: post #227

ummonk wrote: post #140

Earlier quoted context omitted.

Why is that getting downvoted? What the heck.

On HN you can say the same things you say anywhere else but GP didn't couch his rant in fancy synonyms and misused Latin phrases like a priori.

I really like this comment because I agree and was trying to write a comment that said this but not in a toxic way. People act like Hacker News is some bastion of discourse that is raised above the rest of the internet but it's not. Most of the comments I read are people stroking their ego's and enjoying the echo chamber.

Re: Ethiopian Airlines 737 MAX Investigation Preliminary Report

#234

Post by cjbprime » Thu, Apr 04, 2019, 10:08 PM UTC

swhitt wrote: post #226

cjbprime wrote: post #95

Earlier quoted context omitted.

> Its been noted in previous discussions that while it would be difficult, the load can be overcome if both pilots were to operate the manual trim wheel at the same time. I haven't seen that noted anywhere, and have seen it theorized as impossible without motor assist, given their airspeed and with the elevator opposing. Got a link?

Manual Stabilizer Trim Excessive airloads on the stabilizer may require effort by both pilots to correct the mis-trim. In extreme cases it may be necessary to aerodynamically relieve the airloads to allow manual trimming. Accelerate or decelerate towards the in-trim speed while attempting to trim manually. https://www.pilot18.com/wp-content/uploads/2017/01/B737NG_FC... page 312 (8.16)

To be clear, that's a link that agrees with me that it can be impossible, not a link that says they just needed to work harder.

It's also from a 20 year-old manual, and isn't present on newer manuals, and pilots haven't trained on it in decades. Not appropriate to expect pilots to know, and possibly not helpful here: the pilots were low altitude, so allowing the nose to drop even further (to relieve aerodynamic load) may have been deadly too.

Re: Ethiopian Airlines 737 MAX Investigation Preliminary Report

#235

Post by toss1 » Thu, Apr 04, 2019, 10:09 PM UTC

aaron695 wrote: post #200

ummonk wrote: post #140

Earlier quoted context omitted.

Why is that getting downvoted? What the heck.

> knowing some greedy bunch of assholes were effectively that malevolent entity, whose will was expressed via the aircraft. If this it true then link? When was this confirmed? Who are the assholes? Else this is just Reddit spam that contributes less than nothing.

They would be the set of assholes who:

1) decided to move the engines forward making the aircraft dynamically unstable, but improve performance and potential sales

2) decided to counter the instability with a software system (MCAS) based on a single sensor, with zero redundancy or fail-safe mode, AND make a second sensor an optional extra cost for the airlines, AND bury the whole thing in a poor UI, in short: cheaping out on a band-aid fix to a critical problem of their own creation, to maximize profits

3) decided to evade normal requirements to make the airframe a new classification, so that airlines wouldn't need to spend money on retaining and separately qualifying pilots for the different airframe, again to reduce apparent costs of the new airplane and increase sales

4) minimized the training on the MCAS system and require no new training when they made changes to the system. AND make the MCAS system automatically re-engage, based on the single sensor to reduce customer costs

5) ensured that this cascade of bad decisions got implemented through the FAA and rolled out globally.

The effect of all of this was to overlook and minimize critical flaws in a complex human flight system, and do so in order to maximize sales and profits over safety.

They killed 346 people already, and nevermind the economic knock-on effects.

No, I'm not going to hunt back and provide a link to every bit of analysis I read gathering the above facts. It is all recent, non-obscure, and very google-able.

Yes, bad engineering and management decision that kill people will tend to get folks a bit riled up. This is a good thing. While this forum should indeed emphasize facts and intellectual argument, this is not a peer-reviewed journal, it is a forum for humans to discuss issues, and we should also keep here the human perspective on engineering.

Re: Ethiopian Airlines 737 MAX Investigation Preliminary Report

#236

Post by Moru » Thu, Apr 04, 2019, 10:15 PM UTC

Zak wrote: post #26

The design of this system, from what I've heard so far sounds insane . For some background, systems intended to automatically override pilot input upon detecting an impending stall have been used on large, complex aircraft for a long time. The most common mechanism is a stick pusher, which mechanically pushes forward on the stick to mimic what a pilot should do about an impending stall. The force of a typical stick p…

The design is this way due to a long number of decisions going back 50 years. All this due to a staircase that not even exists any more[0].

[0] https://www.latimes.com/local/california/la-fi-boeing-max-de...

Re: Ethiopian Airlines 737 MAX Investigation Preliminary Report

#237

Post by cjbprime » Thu, Apr 04, 2019, 10:16 PM UTC

toss1 wrote: post #235

aaron695 wrote: post #200

Earlier quoted context omitted.

> knowing some greedy bunch of assholes were effectively that malevolent entity, whose will was expressed via the aircraft. If this it true then link? When was this confirmed? Who are the assholes? Else this is just Reddit spam that contributes less than nothing.

They would be the set of assholes who: 1) decided to move the engines forward making the aircraft dynamically unstable, but improve performance and potential sales 2) decided to counter the instability with a software system (MCAS) based on a single sensor, with zero redundancy or fail-safe mode, AND make a second sensor an optional extra cost for the airlines, AND bury the whole thing in a poor UI, in short: cheapin…

> AND make a second sensor an optional extra cost for the airlines

This would be extremely egregious, but it's not what happened. Every MAX has two AoA vanes. Every MAX only hooks up the MCAS to one vane. The optional feature was just an "AOA disagree" light and display, which wasn't even hooked up to an error alarm. It's a red herring for these crashes, in my opinion. The pilots aren't going to hunt around the cockpit during an emergency and notice a disagree light and be able to conclude anything meaningful about what's happening to the plane and how to stop it.

Re: Ethiopian Airlines 737 MAX Investigation Preliminary Report

#238

Post by tuna-piano » Thu, Apr 04, 2019, 10:17 PM UTC

davepage wrote: post #43

Rooster61 wrote: post #7

> The crew performed runaway stabilizer checklist and put the stab trim cutout switch to cutout position and confirmed that the manual trim operation was not working. This is very damning to Boeing. It's precisely the procedure they prescribed and intended to mitigate possible MCAS caused trim runaway. In light of the fact that they put this in place as a justification for moving the engines forward without reclassif…

It does not appear to be "precisely" the procedure, in that sufficient nose up trim was not selected by the yoke manual trim switch prior to pulling the trim cutouts. And then they did not work the mechanical trim wheel hard enough to reset the residual nose down trim. And, the crew left the power setting at climb throughout almost the entire sequence, so they oversped the airframe. And, when they (against procedure)…

Just to put their "mistakes" in context - Sully, America's favorite hero pilot, accidentally put his airplane into an almost stall as he was performing the Miracle on the Hudson (due to the A320's design philosophy, the airplane prevented the stall...). It goes to show- even great pilots doing good work in a stressful time can make critical oversights.

Re: Ethiopian Airlines 737 MAX Investigation Preliminary Report

#239

Post by VBprogrammer » Thu, Apr 04, 2019, 10:18 PM UTC

danaliv wrote: post #218

VBprogrammer wrote: post #179

Earlier quoted context omitted.

The graphs record the AND trim movement even if the electric trim is disabled. You can see that by comparing the pitch trim absolute position to the manual and automatic electronic trim graphs.

Right, I get that, but the last automatic AND actually moved the stabilizer.

Your right. They didn't mention it, probably because it's not indicated on the CVR at what point they decided to try turning it back on.

Re: Ethiopian Airlines 737 MAX Investigation Preliminary Report

#240

Post by alkonaut » Thu, Apr 04, 2019, 10:20 PM UTC

jpatokal wrote: post #197

ec109685 wrote: post #145

Earlier quoted context omitted.

For comparatively trivial things like what to do when we get too much traffic on servers, engineers do “game day” testing. How does anyone expect pilots to run through these crazy scenarios and perform flawlessly unless they have done it in a simulator many times?

Um, they do? Endless simulator drills of various emergency scenarios is a large part of becoming a pilot and staying certified.

And if training for this scenario in a MAX-specific simulation was recommended/required then Boeing wouldn’t sell many planes because that would mean buying simulator time and retraining your existing 737 pilots.

For specific training to be reqired I assume it would need to be made a different certification entirely? Is that even a plausible scenario that this could change?