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Ethiopian Airlines Boeing 737 pilots 'could not stop nosedive'

bbc.co.uk

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Re: Ethiopian Airlines Boeing 737 pilots 'could not stop nosedive'

#261

Post by quickthrower2 »

kharms wrote: post #125
Slartie wrote: post #44

Earlier quoted context omitted.

I am pretty sure the software here did exactly what it was supposed to do. There was no buffer overrun, no NullPointerException, not any other kind of bug. There was just software that reacted exactly as specified. The problem is: those specifications were bad. It's a bad idea to just rely on one single sensor when you actually have two, it's a bad idea to write software that disengages on manual input counteracting…

Bad programming was not the sole or root cause but it was a cause, and people died. You can't punt on that unless you want software engineer to actually mean code monkey. The same way a building architect has to sign off on the design demands of a a client, a software engineer on safety-critical systems must evaluate the spec and consider the effects of edge cases.

While a SW engineer isn’t a code monkey, they are probably the last line in a chain that started with someone saying let’s bolt some oversized engines on this plane, and really even if there is a SWE who spotted the problem and pushed back, the only way to effectively make this software safe is to not need it, I.e design a new plane, and the only way to make that happen is to blow the whistle. So yeah a SWE could have done this but so could anyone involved earlier in the chain.

Re: Ethiopian Airlines Boeing 737 pilots 'could not stop nosedive'

#262

Post by quickthrower2 »

jeltz wrote: post #171
Slartie wrote: post #44

Earlier quoted context omitted.

I am pretty sure the software here did exactly what it was supposed to do. There was no buffer overrun, no NullPointerException, not any other kind of bug. There was just software that reacted exactly as specified. The problem is: those specifications were bad. It's a bad idea to just rely on one single sensor when you actually have two, it's a bad idea to write software that disengages on manual input counteracting…

I do not think all blame should be removed from the programmers that easily. Programmers should think about the ramification of their code and not just blindly implement bad specifications which will get people killed. Now it is possible that Boeing is such a toxic place that any disagreement is silenced, but I do not think we should automatically give the programmers a pass just because it is a specification issue.

The question is who is going to blow the whistle because that is what it comes down to. It’s just not a simple case of doing a better job. It’s going to need someone prepared to lose their job. If it was a simple case of “hey boss I think something is wrong here” and they listened and acted I think that would have happened. Something must be culturally wrong I am guessing.

Re: Ethiopian Airlines Boeing 737 pilots 'could not stop nosedive'

#263

Post by cameldrv »

cmurf wrote: post #258
cameldrv wrote: post #242

Earlier quoted context omitted.

The first officer on that flight was extremely inexperienced. He only had 200 hours of total flight time. In the U.S., you need 1500 to sit in the right seat of an airliner in scheduled service. While I would not put the blame on the pilots for the accident, it's impossible to know if it might have turned out differently had there been two experienced pilots in the cockpit.

There were two experienced pilots in Lion Air 610. In the case where prescribed procedures are followed, and don't work well enough (i.e. you're still stuck in a bad situation that continues to degrade), you're basically asking for experience to manufacturer an alternative on the spot. That's rather like a Hail Mary pass, in terms of logic. It's a 'well maybe maybe not'. I'm not sure how that progresses the conversat…

As I said, I would not put the blame on the pilots. That is clear. Boeing made an unsafe airplane. Airline safety is a layered thing though. Even if it's Boeing's fault, it's possible that the pilots could have recovered, even though it looks like recovery is not necessarily easy.

I also have a fair bit more than 200 hours, and I can't say whether I would have made a smoking hole in the ground or not either. Still, if I were put in that position, I would much rather have an experienced pilot sitting to the right of me.

Having an inexperienced pilot that probably hasn't ever experienced a real emergency is a significant liability when you're trying to troubleshoot something like this without a lot of extra time. In this case, they would have had a better chance of surviving if they had identified that the problem was MCAS before the plane got so wildly out of trim, or they had made the decision to turn the electric trim back on sooner. This is a lot easier if you've got two fully fledged pilots instead of effectively a captain and an apprentice.

Say what you will about the 1500 hour rule, but there has been precisely one fatality in all of U.S. aviation in the ten years since the Colgan flight.

Re: Ethiopian Airlines Boeing 737 pilots 'could not stop nosedive'

#264

Post by cmurf »

alkonaut wrote: post #145
mhandley wrote: post #7

Will be interesting to see the details when the report is actually public. It does sound like the scenario that Mentourpilot explored in the simulator is close to what happened, namely: Bad AoA probe causes MCAS to trim down, and also to indicate IAS disagree. Pilots increase throttle as per non-normal checklist to reduce the risk of stalling due to unreliable airspeed. Pilots disable electric stabilizer trim, as per…

I'm an armchair non-expert at best: but shouldn't planes always be controllable by the column so long as the plane is mechanically OK? I.e. max power + pull stick should always just take the plane up, regardless of any amount of misconfiguration such as being out-of-trim etc? Isn't that a reasonable expectation? That is: a pilot in panic at low altitude should never be required to do anything more than he basically c…

Short answer: it's complicated. But there's this small detail of more accidents in the past than in the present. Without doing a breakdown, this is due to better and more reliable components, better and more reliable pilot training (including CRM), and better and more reliable safeguards provided by computer automation.

In your example, max power + pull stick does almost always take the plane up. Pull back more, rate of climb increases. Pull back more, rate of climb increases. Pull back more, and rate of climb decreases. Pull back more, and you're no longer climbing. Pull back more, and you're sinking. Pull back more, and you crash. So... what went wrong? A pilot induced unrecoverable stall spin. The only inexpensive way of prevention is training. A more expensive system will place safeguards: stick shaker, or in fly by wire flat out ignore nose up input when approaching the critical angle of attack. So that means such systems must know about angle of attack, and that in effect a computer can second guess pilot inputs in certain cases. And that ship has sailed a while ago.

For a few decades now, incident and accident response always includes discussions of "add another button, add another indicator, add another software routine" to add more protections. As far as I'm aware, the pilot is trained about all of those safeguards. How the plane behaves with them. How the plane behaves without them.

What makes me angry about MCAS is not the single fail point (which I leave up to engineers to fight over) but the lack of training.

In the working case, at high angle of attack, this thing is going to cause the plane to exhibit a completely different behavior than prior 737s. It's going to do this rather odd duck nose down push every 10-15 seconds or whatever it is, in addition to stick shaker? That is not aerodynamic abstraction by software. That's like a silent flight instructor who just pushes on the yoke every 15 seconds for no goddamn reason. At first it will seem transient until you pick up on the pattern. And I can turn that shit off? I should know about the consequences of turning it off! There are consequences with it on, and off, and if it's confused! I need at least three kinds of training on this new feature.

I'd love to see this iPad difference training program, and go through this specific part of that training. Or even if a 737 pilot has made a youtube video of that training.

Me: pilot < 1000 hours total flight time, ex-flight instructor, and maybe 20 minutes of 737 sim time in a full motion sim that you get to record as actual flight time in your log book, which is fun to say but does not add to my credibility!

Re: Ethiopian Airlines Boeing 737 pilots 'could not stop nosedive'

#265

Post by cmurf »

CaptainZapp wrote: post #195
Shank wrote: post #160

Earlier quoted context omitted.

> but shouldn't planes always be controllable by the column so long as the plane is mechanically OK? The problem is that you can easily exceed the aircraft flight specifications if you enable unlimited control. If you pull the stick back at max power you can seriously risk the creation of a stall, which is why MCAS exists in the first place. The whole goal Boeing had was to create a safe plane by letting software ens…

The problem is that you can easily exceed the aircraft flight specifications if you enable unlimited control. If you pull the stick back at max power you can seriously risk the creation of a stall, which is why MCAS exists in the first place. That's manifestly wrong. MCAS was introduced because of the design decision to place the larger and more powerfull power plants further in front and higher up. The reason for th…

>MCAS was introduced in order to simulate the same behavioral characteristics of the older 737s.

Sounds plausible, but something with the story is still super screwy because a nose down "push" every 15 seconds is nothing like older 737 approach to stall behavior. If the idea is you want the same stick forces at approach to stall as 737NG, then you need some kind of motor or brake in the yoke mechanics to simulate it on a MAX.

If it were really simulating the 737NG stick forces, and this were erroneously triggered in an appropriate angle of attack state, the pilot would simply be getting weird/unexpected control stick forces - rather than a fight to the death, possibly at low altitude.

And if that simulation were to fail when needed (real high angle of attack), well yeah you're fucked if it's a necessary simulation to help the pilot avoid a developed stall. But at least in that case I would expect even slightly delayed recovery from stall is a better scenario than forcing the nose down.

I just don't like this feature pretty much as designed when working, when it's disabled, and when it's confused. It all smells like bullshit. Now I could easily be wrong and it's actually duck farts. But something stinks. I don't see how it gets around either FAR 25 airworthiness certification requirements, because it can be disabled. Or around FAR 61.31 type rating requirement, because it can be disabled. Disable it, and now your airplane is not airworthy and your pilot possibly not suitably type rated? Come on.

Re: Ethiopian Airlines Boeing 737 pilots 'could not stop nosedive'

#266

Post by calcifer »

Yetanfou wrote: post #226
calcifer wrote: post #202

Earlier quoted context omitted.

"I don't see colour, it's not about race" said the white Western European guy...

You're implying I am 'white', 'western-European' and '[a] guy' even though this is irrelevant and there is no indication of either my race, origin or sex in my post. Please stop doing that, it only serves to create strife where no strife is needed. It is almost as if you did not read the comment you responded to or - worse - decided to ignore it because it does not fit a given narrative.

> You're implying I am 'white', 'western-European' and '[a] guy'

I'm saying it out right, not 'implying'. Based on your comment history, I think I'm right on all three of those adjectives, though I'm happy to be corrected.

Re: Ethiopian Airlines Boeing 737 pilots 'could not stop nosedive'

#267

Post by phire »

treis wrote: post #228
phire wrote: post #178

Earlier quoted context omitted.

> Now, from what I understand, appying nose-up electric trim should override MCAS, and so this course of action should be possible. I'm not so sure. Will have to wait for the final report to be sure, but I feel like the Lion Air flight should have survived if the pilot's trim up commands took priority over MCAS's trim down commands. They were fighting it with trim up commands and they lost. I fail to see how they cou…

You're right, but since 10 > 5 the pilot should always be able to "win". You can see it happening in the Lion Air flight: https://spectrum.ieee.org/image/MzE4Mjg2OQ.jpeg I count 20 cycles of MCAS -> Pilot correction. It's not clear why the pilots lost the 21st cycle. It could be that they stopped making corrections or another yet to be identified airplane failure.

The MCAS activation just after 23:33:53 pushes the stabiliser down slightly further than it did at any point previously.

After this point, the stabiliser looks like it stops responding to trim up commands. The pilots do a few more trim up commands, but the is never a significant upwards response again. Perhaps this is because the pilot's trim up commands appear to be shorter, or perhaps the pilots are pressing the trim up button, hearing a loud girding noise from the electric trim motor as nothing moves, so they stop holding trim up.

With all this talk about aerodynamic forces being too strong on the Ethiopian Airlines flight for pilots to manually trim up, I'm wondering if the Lion Air flight experienced aerodynamic forces so strong that even the electric motor was struggling to trim up.

Re: Ethiopian Airlines Boeing 737 pilots 'could not stop nosedive'

#268

Post by VBprogrammer »

simion314 wrote: post #247
VBprogrammer wrote: post #237

Earlier quoted context omitted.

There was definitely an air of superiority of American pilots. The problem is that there is a grain of truth to it. A big part of this is that the American Airforce train a huge number of pilots to an incredibly high standard who eventually leave the military and become civilian pilots. Any pilot who isn't naturally gifted in the art of flying an aeroplane will be flunked before finishing their training. They are tes…

So, do you know as a fact that plots in other countries are less passionate or have less training? It would be interesting if you have a source of how many civilian pilots are ex-military pilots, as an non-expert I would say that having experience with a fighter plane is not better then having same hours of experience with a civilian plane, it is not like fighter plane experience is much better then other planes when…

Apparently somewhere around 30% if this is to be believed.

https://www.washingtonpost.com/news/wonk/wp/2018/04/20/the-o...

"A grain of truth" doesn't mean it's provably true. But it's hard to argue that flying a plane load of passengers on autopilot from the same 4 airports for hours on end remotely gives you the same skill level as flying low level, in high performance and often in formation with other aircraft would.

Re: Ethiopian Airlines Boeing 737 pilots 'could not stop nosedive'

#269

Post by jussij »

salawat wrote: post #248
jussij wrote: post #119

Earlier quoted context omitted.

> Is it shameful because we suspect that it was an intentional lie on their behalf Exactly this. > or is it shameful even if it was honest opinion of these Boeing representatives at the time? It seems fairly obvious Boeing was aware the 737-MAX had some serious faults, but instead of admitting those faults it seems fairly obvious they went out of their way to deflect blame way from their failed aircraft onto the now…

This is because of Product Liability law. If they admit in any way to releasing a known dangerous product they open themselves to massive damages.

But don't Boeing still find themselves in that exact same position, if not worse only because of all the deaths involved?

When the Lockerbie bombing brought down Pan Am Flight 103, the relatives sued PA AM over those deaths.

In that case a jury found Pan Am was liable for damages because it's poor security procedures had failed to protect the passengers.

I would imagine lawyers would be salivating at the though of suing Boeing over these two disasters in what would appear to be a much easier case to win.

Re: Ethiopian Airlines Boeing 737 pilots 'could not stop nosedive'

#270

Post by DuskStar »

cmurf wrote: post #260
DuskStar wrote: post #249

Earlier quoted context omitted.

There's a major difference between the Lion Air and Ethiopian Airlines crashes though - altitude and incident duration. Things that are recoverable from 5000' AGL might not be from 1000' AGL. Speed is life, and altitude is life insurance after all. From my reading, the Lion Air pilots could have disabled electronic trim anytime after those 26 recoveries and been fine. But the Ethiopian Airlines pilots only had 1000'…

Could have disable it, but didn't? We don't actually know yet whether they did or when they did, and if they did if it was already too late. Critically we don't know their mental state, as we don't have transcripts yet. If the pilots are reactive or even panicked at the unexpected uncommanded pitch behavior, they may have been doomed right from that moment. The previous flight, Lion Air 34, the pilots likewise did no…

> Could have disable it, but didn't? We don't actually know yet whether they did or when they did, and if they did if it was already too late. Critically we don't know their mental state, as we don't have transcripts yet.

'Could have' in the purely mechanical "we think this would have been possible and allowed the aircraft to survive" sense, not the "the pilots knew how to do this" sense.

> As for why MCAS is triggered below 1500' AGL in the Ethiopian Airlines case, that is a very good question. I have not seen the altitude above which MCAS is supposed to apply, and I haven't discovered how that trigger altitude is determined, radar altimeter?

It's not altitude limited, but flaps limited - so would have engaged when flaps were retracted sometime after reaching 1000' AGL. (at least, 1000' seems to be the altitude mentioned in the procedure summaries I've seen for other 737 models - things might be different for high altitude takeoffs) And as it turns out, ET-302 reached FL 140 ~5 minutes into the flight, so there goes that theory.

> Most of the facts we still don't know.

And hopefully we'll eventually learn them, and write some new rules with them.

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